Edson AB crash, VRS?

[malabo]

Edson AB helicopter crash (https://globalnews.ca/video/rd/ed446d68-eaf5-11ed-a09e-0242ac110005/?jwsource=cl)

Yesterday, A350 B2. Downwind, looking at the subsequent smoke. VRS or loss of power?

[Rotorbee]

Strange. Would not bet on VRS. Too much forward speed and no waggling of tail. Loss of power? Might be, but still strange. I'll wait for the report. Could be an interesting read.
But it looked like he landed with quite a bit of tailwind. Why would he do that?

[Robbiee]

Maybe this is that thing where they simply waited too long to apply the brakes?

[SASless]

Just once I would like to see a brand new first ever way to crash a helicopter.

Open airfield with at least one wind sock somewhere....and the Ace lands downwind with a near gale blowing.....now what could possibly go wrong in a situation like that?

The good news is either the crashworthy fuel system worked....or there was not enough fuel in the system to feed a fire.

[Rotorbee]

I am not sure, but in the beginning of the video there is something that looks like a windsock. Very blurry, but it is straight out in the direction of flight. Could have been a clue.

[albatross]

Strange. Would not bet on VRS. Too much forward speed and no waggling of tail. Loss of power? Might be, but still strange. I'll wait for the report. Could be an interesting read.
But it looked like he landed with quite a bit of tailwind. Why would he do that?

Looking at the video it appears to me as a “Perfect” VRS entry. The tailwind would make the machine look “faster” due to the higher ground speed. His airspeed would have been much lower. You can see the sudden increase in rate and angle of descent.

Just my opinion. The report will hopefully provide Truth.
Glad the pilot is only shaken but OK.

[[email protected]]

Looking at the video it appears to me as a “Perfect” VRS entry. The tailwind would make the machine look “faster” due to the higher ground speed. His airspeed would have been much lower. You can see the sudden increase in rate and angle of descent.

Just my opinion. The report will hopefully provide Truth.
Glad the pilot is only shaken but OK.

Agreed, the sudden increase in ROD is a fair indicator of VRS on a downwind approach.

Don’t they teach people how to get from downwind to into wind whilst maintaining ETL any more?

[Hughes500]

Think he is moving forward too quickly and the ROD doesnt look that high for VRS, Think he lost translational lift, realised too late was going down too quickly and overpitched it.

[Rotorbee]

Think he is moving forward too quickly and the ROD doesnt look that high for VRS, Think he lost translational lift, realised too late was going down too quickly and overpitched it.
Yupp, I go with that, too. Exactly my thinking.

[Nubian]

Think he is moving forward too quickly and the ROD doesnt look that high for VRS,.

His forward speed pretty much match the windspeed. His ROD is increasing, but lucky for him he didn’t have much height to start with. If he had had a bit more height, the damn thing would pancake even harder, as the VRS would develop properly.

What this guy was thinking is hard to comprehend…

[megan]

The video in the OP's link won't open for me, so here it is if others are having similar trouble.

https://www.youtube.com/watch?v=24G0Nn5oFZ4&t=17s

[FH1100 Pilot]

Think he is moving forward too quickly and the ROD doesnt look that high for VRS, Think he lost translational lift, realised too late was going down too quickly and overpitched it.
Sooooo, settling with power, then?

[Hughes500]

To get VRS in a 350 you have to catch up your downwash, that is around 800 / 900 ft a minute ROD ( depending on how heavy the helicopter is , the heavier the machine the more downwash and therefore less likely to catch up the downwash ). I demo incipient VRS in a Hu 300 for ppl's, ROD 500 ft a minute lee than 20 kts and 18" MAP the book says one is in VRS, I will demo pull the power back in, the 300 stops descending and climbs back up, so no VRS because we have not caught up our downwash. To me the 350 as our cousins from across the pond say is settling with power or as we would call overpitching. Simply put the pilot has forgotten his energy mangement. The airframe has built up too much energy by descending too fast, he has come off translational lift ( downwind ) he has then forgotten that by pulling power the nose pitches up robbing him of even more translational lift ( what little he has ) now asks engine for more energy, puts in a boot load of right pedal, ( (bet the power alarm was gong off if it was a B3)even more energy is robbed from the main rotor and down she goes as he overpitches everything . Might be wrong but the ROD for me is not high enough for VRS ! Stand to be corrected here

[[email protected]]

The classic way to get VRS is on a downwind approach - as he is.

Then let yourself get steep - as he does.

Then start to try to recover with power - as he does.

Then try to reduce speed with a flare that won’t have any effect due to being downwind - as he does.

Then experience what some long-line pilots describe as falling into a hole - as he does.

And finally crash because you don’t have enough height for recovery - as he does.

You need a RoD between 0.5 and 0.75 approx of your down wash speed to encounter VRS with a forward airspeed of less than about 15 Kts - the lighter the aircraft the lower the RoD required as the downwash speed is lower.

He may not have got into fully developed VRS but I see no indication of over pitching or settling with power.

I remain with VRS as the cause.

[Rotorbee]

Well, the result is the same. Anyway, I am still on Hughes500's side. VRS needs time to set up. You have to pump energy in these vortices. Even if it may feel like it, VRS does not occur in the blink of an eye. It starts before the pilot even feels something. And in this case, I would expect that the tailwind, which is conventional airspeed but from the wrong end, would disturb the formation of the vortices.
And as we have all stated numerous times in the past, VRS-accidents are rare, very rare. Much rarer that some want to make us believe. Overpitching is much more common.
He came in hot, descending, had the collective down, flared and was slow on the power management when the flare did not bring the results he was anticipating. And it was a B2. Other blades and engine than the B3 or B3e. Though, if, as H500 suggest, a B3 would already yell at the stick jock, the B2 is worse.

[Robbiee]

VRS?
Overpitching?
Just a dumbass?

Taking all bets :cool:

[[email protected]]

VRS needs 3 conditions to be met - high RoD (0.5 to 0.75) of your downwash speed, low IAS and then power applied.

In the video he clearly has 2 out of the three thanks to a steep downwind approach but doesn’t hit VRS until he brings in the power, builds the tip vortices and begins to stall the roots.

He doesn’t have enough height to recover and his only option is to try and power out of it which just makes it worse.

He may over pitch it right at the end in panic mode but VRS did the damage there.

[[email protected]]

Definitely dumbass I reckon Robbiee :ok:

[[email protected]]

Settling with power usually comes as a result of trying to establish an OGE hover without the power margin to do so.

[Hughes500]

Crab, so what is 0.75 of the downwash of a B2 then ? having loads of time in a B3 with a line lifting I would suggest that its downwash speed is pretty close to 1000 ft plus a minute. In over a 1000 hours of lifting on a longline never experienced the " hole" or near vortex ring. What have had is getting pretty close to dumping the load a I have let the ac and load build up too much energy on a steep approach and got my energy management all wrong, ended up luckily getting the load on the ground as the FLI hit 10 banana's and a bong in the headset. No damage done aprart from a quick change of underwear and that was just the ground crew !!!!!!! Just as well I was wearing brown trousers

[Nubian]

Crab, so what is 0.75 of the downwash of a B2 then ? having loads of time in a B3 with a line lifting I would suggest that its downwash speed is pretty close to 1000 ft plus a minute. In over a 1000 hours of lifting on a longline never experienced the " hole" or near vortex ring. What have had is getting pretty close to dumping the load a I have let the ac and load build up too much energy on a steep approach and got my energy management all wrong, ended up luckily getting the load on the ground as the FLI hit 10 banana's and a bong in the headset. No damage done aprart from a quick change of underwear and that was just the ground crew !!!!!!! Just as well I was wearing brown trousers

Comparing loadlifting in a B3 and an “empty” B2 doing a steep approach in tailwind is not comparable for downwash speed. I bet in your over 1000 hours, you haven’t tried this trick downwind in the B3 either.

What you explain below is you balancing on over pitching and being lucky.

[Nubian]

And it was a B2. Other blades and engine than the B3 or B3e. Though, if, as H500 suggest, a B3 would already yell at the stick jock, the B2 is worse.

Other engine yes, same AS355 blades as all models after the original B.
Knowing how to operate safely, you don’t need the overlimit warning to tell you that you c..ked up.

The B3‘s performance might have saved the day, but only to spend a lot of time in the hangar changing very expensive parts before going back to work.

[RVDT]

The info is there for some "fag packet forensics".

Assumptions:
1 crew
End of the mission and heading home with "min" reserves.
Mass ~ 1500 kg

For reference use passing over the vertical pole in the perimeter fence in the video as where it all started.

Using the length of the aircraft fuselage to eyeball the height above the ground = 35 ft x ~ 3 = ~ 105 ft.
Time stamps from the video passing over the pole to impact point = ~ 5-6 seconds so ROD ~ 1000 - 1300 fpm give or take. As the 350 normally only has a standard VSI it would not indicate this rate due to lag in the timeframe involved.

Again "fag packet" calcs would point to the induced downwash velocity around ~ 1600 - 1800 fpm. Crabs estimate of ROD requiring 50-75% of your downwash is in the ballpark for VRS .
Keep in mind the lighter you are the easier it is to get into VRS due to lower disk loading and resultant lower downwash velocity.

Go and talk to a Lama pilot (not so many left) and wonder why Mr Vuichards videos always have a Lama in them?

Use the smoke after the impact to estimate the wind speed and direction versus the groundspeed after passing the perimeter vertical pole. I would guess IAS was near zero just after passing the pole at about 90 ft.
There is a pitch attitude and ROD change as it passes behind the horizontal perimeter fence pole where I am guessing it has just dawned that "something ain't right" and someone reverted to being a passenger.

As the camera tracks the aircraft pretty well watch the video with your hand covering the lower part so you remove any indication of movement and you can only see the aircraft. Would you fly this profile with zero airspeed?

As to "overpitching" which is just poor handling of power margins versus inertia - meh! If the wind was blowing the other way we wouldn't be having this convo here? All helicopters hover and climb as bad as each other at MTOM due to commercial and design specification minimums.

As many of my old crusty peers over the years have said - "If you are flying a helicopter and do not know constantly what your local wind speed and direction is - it was suggested that you just land, get out and seek employment in another field.

It is actually quite difficult to get into VRS and requires some effort to demonstrate but one day you will get lucky if you keep the effort up.

As an aside B3 blades are B3 blades and cannot be fitted to other models with the exception of maybe a 355N or NP. Yes they may look similar with grey paint but...............internally they are different. A B3 is not just a B2 with a "phat" engine. I know people who have tried unsuccessfully to put B2 blades on a B3 and had to throw away a lot of parts on discovery of their error!

[FH1100 Pilot]

Go and talk to a Lama pilot (not so many left) and wonder why Mr Vuichards videos always have a Lama in them?
Claude's latest video is done in a Robinson.R-22.

(26) Claude Vuichard demonstrates the efficiency of the « Vuichard Recovery Technique » on a R22 - YouTube

[Robbiee]

Claude's latest video is done in a Robinson.R-22.

(26) Claude Vuichard demonstrates the efficiency of the « Vuichard Recovery Technique » on a R22 - YouTube (https://www.youtube.com/watch?v=bIqEezEDb9A)

Something tells me this wouldn't have saved this guy in the Astar.

[[email protected]]

Claude's latest video is done in a Robinson.R-22.

(26) Claude Vuichard demonstrates the efficiency of the « Vuichard Recovery Technique » on a R22 - YouTube (https://www.youtube.com/watch?v=bIqEezEDb9A) yes an aircraft with a similarly light disc loading and low downwash speed.:ok:

It’s not very scientific but I have always considered that the downwash speed of a helicopter in an OGE hover is probably equivalent to its RoD in a bucket speed auto - both steady state with no acceleration but I couldn’t prove it mathematically.

The higher the disc loadings of helicopters I have flown, generally the higher the RoD in steady state auto.

The 350 from memory is about 1800 to 2000’ per min so you would need about 900’ to say 1500’ per min to meet the first condition of VRS.

[Rotorbee]

Right, here we go again. VRS and Vuichard discussions. I really hoped that was over.
@Robbie: You are so right.
VRS is a very good excuse for a pilot who finds itself in a situation where the "bottom dropped out". With that, you are pardoned, because VRS sounds like he/she was just unlucky. It is by far not as bad in the perception of peers and public, than having to say: "I messed up". Despite the fact, that he/she also "f**** up" by getting in VRS. But it is so much easier to blame a mysterious aerodynamic effect, than your own stupidity.
It is very human, to lock for another culprit. There are quite a few statements of pilots out there, where they claimed, that they lost power in the worst possible moment. But afterwards nobody finds anything wrong with the engine.
Human beings are often very bad sensors. When we are focussed on a certain task, we are capable of ignoring a lot of other things that are going on. Even though our brains are extremely powerful in processing information, our brain is optimised for efficiency, not processing information in parallel. When we are tired, the brain shuts down even more unimportant informations. That is the precise moment, when we are surprised by something we did not expect to happen and our reaction time becomes a lot longer. In our case here, it is exactly why in the end, the question if it was VRS or not, is really not important, because in either case, the result is the same. The big mistake was made when the pilot decided to come in fast with a tailwind. When the "bottom dropped out", he was too surprised to do anything that could have saved the day in the altitude he had left. And bang.
I am certain, Transport Canada will find out what happened, but just using probabilities, I can stay with my bet, that it wasn't VRS. Furthermore, the aerodynamics of VRS are much more complicated than Vuichard and pilot handbooks make us believe and I am pretty sure that in this case, it did not happen.

[SLFMS]

Oh God here we go. VRS or not, settling with power, Vuilchard. Where’s the guy that hates twins…..

Let’s settle an easier topic like a peace process for Ukraine.

Guys always focus on ROD for VRS, whereas it’s actually flow though the disk. A big flare downwind, to the disk is the same as ROD.
My two cents is it looks exactly like VRS and ticks all the boxes.

[Winnie]

It's funny that most of you are talking about the same thing, but have different vernacular!
In the US FAA Land Settling With Power (SWP) is what we used to demonstrate, and is the same as Vortex Ring State (VRS) we demonstrated in Canada... Power Settling would be the same in both jurisdictions...

The requirements to enter SWP/VRS as per the Transport Canada textbook is speed less than ETL, some power applied, and a rate of descent greater than 300 feet per minute. It doesn't take much. This looks like that, but obviously that will have to be sorted by the experts.
Funnily enough, on any PPC in Canada you usually have to talk about 3 things in some detail, those being Vortex Ring State, Loss of Tail Rotor Effectiveness, and lastly Power Settling. In the 20 years I've had PPC's I've had to talk through all 3 every time...

[Robbiee]

The problem I've always had with VRS, is that we always practice the recovery from a 2,000' hover. Something tells me the aircraft is going to feel very different in a tailwind approach where you think you have enough airspeed,...and I'm curious as to how the Vuichard technique would handle that?

Anyway, I'll never have a fat enough logbook (or wallet) to crash an Astar, so I can only guess here, but my money is still on, that he came in too hot and waited too long to start slowing down.

[[email protected]]

You can come in too hot downwind and get away with it if you are shallow (or level) and understand you will need more power than doing it into wind. Your flare will have little effect once you lose ETL as you don't get the benefit of the change in relative airflow to increase rotor thrust.

If you come in steep downwind then you better not be too hot or all your problems are going to come in at the end when you really, really want to stop - you will need a lot more power to arrest groundspeed and RoD and put yourself right in the bracket for VRS ( and if you don't have enough power you will compound it by settling with power/overpitching).

Without wanting to restart the argument all over again - if you are falling out of the sky because you don't have enough power and the Nr is decaying, that is SWP. If you are falling out of the sky because you f*****ed up but haven't run out of power and Nr is normal then that is VRS.

You can experience both and either one can lead to the other which is often the cause of much confusion.

[Rotorbee]

@Winnie: A few years ago, the FAA finally caved in. In the new Helicopter Pilot Handbook published by the FAA, it is called VRS.

For this case here, one might consider the following. In a flare, you do not use a lot of power, if you come in really hot, the collective might even be on the floor. Otherwise you balloon up up and away and with it your NR. The rotor is therefore in a windmill state. In this state you can not have VRS. As you can not have VRS in an autorotation. VRS can only develop, when you bring in power and since the vortices need time to build up, it will not be immediately in the VRS state. But the surprise was, that the flare did not bring the intended result, i.e. stop the forward speed and the descend rate, the floor came up faster than the pilot could bring in the power and develop any meaningful VRS. The PROBABLE cause of the accident was NOT VRS. The probable cause was a tailwind approach with way too much wind where the pilot did not anticipate the higher than normal sink rate. This kind of accident happened many times over the years. One is even documented on film by Robinson. During certification testing, the FAA pilot flared aggressively, levelled the ship and hit the ground. The blades folded down and chopped of the tail. The FAA pilot jumped out an threw his helmet on the ground. He wasn't a happy camper. And that was into the wind. I asked some more knowledgeable pilots if that could have been caused be VRS and the answer was no. It was HTG (Hit The Ground).

[[email protected]]

All valid points Rotorbee but where is the harsh flare in the 350 video? There isn't one and what little flare there is comes way too late and is very small.

If he had been shallow and fast I would completely agree with you but he was steep and slow and right in the bracket for VRS.

[Robbiee]

I've never liked terms such as "not enough power", "running out of power", and "power required exceeds power available", because these terms seem to put the blame on the aircraft, when its clearly the pilot who's at fault.

If you "don't have enough power" its because you're too heavy for what you're trying to do.

If you're "running out of power" its because you either waited too long to start slowing down, or you've entered the Vortex Ring State.

[fdr]

Oh God here we go. VRS or not, settling with power, Vuilchard. Where’s the guy that hates twins…..

Let’s settle an easier topic like a peace process for Ukraine.

Guys always focus on ROD for VRS, whereas it’s actually flow though the disk. A big flare downwind, to the disk is the same as ROD.
My two cents is it looks exactly like VRS and ticks all the boxes.

Not quite... I understand the sentiment, but a flare with any forward IAS will reduce inflow through the rotor disk. If there is no airspeed, then the consequence is not altering the inflow to the disk, but the angled lift vector will result in higher AOA demand to avoid a descent developing, and that starts getting into the potential rapid entry into over pitching, where the Nr starts to droop due to the excessive AOA related torque demand.

VRS is related to a re-circulatory flow field down through the rotor disk, and that means it isn't encountered in an autorotative state, which is what arises in a big flare downwind. Now, coming out of the flare, there is an increased thrust requirement, a skittish directional stability issue, and a need to still counter the tailwind condition if you are external referenced.

[Robbiee]

Meh, we're all kinda missing the point here. He crashed because he came in on a tailwind and didn't adjust his technique accordingly. So, the real question is, why did he do that?

Anyway, they should make it mandatory that pilots who crash must go on social media to explain themselves. :p

[Rotorbee]

Robbiee, you are not wrong. We can argue about VRS or overpitching till the cows come home, but the reason why this accident happened does not lie in those two single states.

Crab, I think we are missing a crucial information here. What was the wind speed? From the very blurry picture what could be a wind sock, I would estimate the windspeed around 10 to 15 kts. Could be worse. But did he fly at that speed? What did he see on his speed indicator? Did he look at it? When he flared higher up, did he feel the loss of ETL?
If the windspeed was higher by a certain amount than the speed of the helicopter, then there is no VRS. I think I see the ship turning a bit and if that was the case, he would have a slight side wind. In that case again VSR would be very unlikely. Those vortices are not so stable and are easily blown away. We also do not know how heavy the ship was. There is the possibility that with that side wind and high gross, there wasn't just enough power left to stop the descend.
These are all things we do not know and who could change the picture radically.

[albatross]

I have talked to a fellow who was there.
Seems VRS is the local working theory.

[Hughes500]

I just love HTG, must remember that in my next student briefing !

[Nubian]

As an aside B3 blades are B3 blades and cannot be fitted to other models with the exception of maybe a 355N or NP. Yes they may look similar with grey paint but...............internally they are different. A B3 is not just a B2 with a "phat" engine. I know people who have tried unsuccessfully to put B2 blades on a B3 and had to throw away a lot of parts on discovery of their error!

Curious to see what has changed?? Can you get me the part number(s) for these B3 blades then?

As for the B3 not being a B2 with a big engine, I'll ask, what's so different with it besides it all got a lot simpler to operate and with better performance?


As for relevant info for this thread.
METARs UTC -6 DST
CYET 050156Z AUTO 16022G32KT
CYET 050211Z AUTO 17016G34KT

Runway is 07/25 and the buildings in the background are located on the north side of centreline.


Good thing the pilot only sustained minor injuries, as it could have got a lot worse.

[staycalm]

This was VRS. Those saying the decent rate doesn't match VRS I'm sure would have a different opinion from inside the helicopter at the time. He didn't have much altitude to build up a descent rate, but it was more than enough to smash the aircraft to pieces. That counts as "high rate of descent" for me.
Practicing VRS recovery (at a safe altitude) is simple, reliable, and eye opening for those who think it only happens if the wind is a certain way or expect there to be some noticeable feeling in the aircraft.

1. At a safe altitude (say 2,000') fly level at roughly max endurance with power also roughly at max endurance. (It doesn't matter which way the wind is blowing, and you're not maneuvering in relation to ground references.)

2. Without changing anything else, pitch up about 5-8 degrees.

3. Simply hold that attitude as airspeed bleeds off. Don't change power.

4. Altitude might increase briefly, but then decrease. Hold the "wings" level, nose slightly up attitude, and moderate power setting. As airspeed bleeds off the rate of descent increases until you recover with a change of attitude (with decent rate above 300'/min you can also notice the ineffectiveness of adding power).

5. You won't "feel" it (unless you're too low and have ground rush) and the aircraft doesn't feel out of sorts, despite the alarming behavior of the altimeter and VSI. This is important to know for those who think they'll get some kind of seat-of-the-pants warning before VRS.

6. Recover (pitch down or bank/roll).

Fly safe (i.e. paranoid)

[Rotorbee]

Hi staycalm. Nice to see a new face here. Just that you know, you are a bit late to the VRS party. We have beaten that dead horse to mush by now in several several threads and most of us get sweaty palms when "VRS" shows up in a title. And for "save" in VRS demos, since I have seen the flight test data of an ONERA VRS research, I will not feel completely save in a VRS demo ever again. The increased flapping is just too much for my taste and too close to the tail boom.

BTW, has anybody heard anything about the R44 crash a few years ago, where the ship fell out of the sky with a young CFI, probably demoing VRS?

[staycalm]

Yeah, I've seen the arguments over semantics and acronyms here and elsewhere. There are issues of physics/momentum, and issues of aerodynamics. Sometimes they occur separately, other times together. Not going further on that. ;)

VRS is serious business, and I am opposed to anyone taking a demo to an unnecessary extreme, thinking it's safe to do so. But that goes for all the other maneuvers in a helicopter, too. Right? There's a middle ground to work within, giving us the opportunity to do cool stuff and earn a paycheck. But there's also a point to "knock it off" in any aviation operation. Perhaps the R44 doesn't have much of that middle ground. I would guess otherwise, but that community can decide for themselves.

I think it's valuable to experience how easy it is to slip into VRS, and that the entry is much more insidious than is typically assumed. The practice method I described is seemingly benign, yet results in undeniable VRS. Pilots should not be fooled into thinking it only happens with a tailwind, or flaring a certain way, only when you're heavy, or this or that... Those can all be factors, but the three ingredient of VRS can also combine under seemingly tame situations. It will bite when you're not thinking about it because of task saturation or complacency with something you've done 1,000 times. When you see the ground rush, believe it, abandon your pride and immediately make whatever ugly, aggressive recovery maneuver the situation allows for.

[Hughes500]

This was VRS. Those saying the decent rate doesn't match VRS I'm sure would have a different opinion from inside the helicopter at the time. He didn't have much altitude to build up a descent rate, but it was more than enough to smash the aircraft to pieces. That counts as "high rate of descent" for me.
Practicing VRS recovery (at a safe altitude) is simple, reliable, and eye opening for those who think it only happens if the wind is a certain way or expect there to be some noticeable feeling in the aircraft.

1. At a safe altitude (say 2,000') fly level at roughly max endurance with power also roughly at max endurance. (It doesn't matter which way the wind is blowing, and you're not maneuvering in relation to ground references.)

2. Without changing anything else, pitch up about 5-8 degrees.

3. Simply hold that attitude as airspeed bleeds off. Don't change power.

4. Altitude might increase briefly, but then decrease. Hold the "wings" level, nose slightly up attitude, and moderate power setting. As airspeed bleeds off the rate of descent increases until you recover with a change of attitude (with decent rate above 300'/min you can also notice the ineffectiveness of adding power).

5. You won't "feel" it (unless you're too low and have ground rush) and the aircraft doesn't feel out of sorts, despite the alarming behavior of the altimeter and VSI. This is important to know for those who think they'll get some kind of seat-of-the-pants warning before VRS.

6. Recover (pitch down or bank/roll).

Fly safe (i.e. paranoid)

Staycalm, 300ft rate of decent, just pull the collective and the aircraft will climb, so not VRS. Dont believe it come to UK and I will show you ( or read Nick Lappos post many years ago ). Feel it, oh yes you do, before you ask, Yes I have been in full VRS with a ROD of 3000 ft a minute, scary !

[Rotorbee]

Good (please insert your preferred deity here) H500. Do you really want to trigger that discussion again?

Just so everybody knows, in a few years we will see the effectiveness of the different recovery techniques, because EASA has initiated a research program to find out what it is all about.
VRS (Helicopter Vortex Ring State Experimental Research) (https://www.easa.europa.eu/en/research-projects/vrs-helicopter-vortex-ring-state-experimental-research)
Now we can lean back and wait for the results.

[FH1100 Pilot]

HAHAHAHAH! I laugh. Pilots arguing over whether a crash was "caused" by VRS or SWP. HAHAHAHAH. So silly. I've said for a long time that IT DOES NOT MATTER which is which. The end-results are the same: If you come in downwind, chances are good that you will crash and the geeks on PPRUNE will argue interminably about which particular anomaly you experienced. You can go up to altitude and do VRS demonstrations all you like - but that's not where the accidents happen, is it? Nope, they happen at the bottom of f'ed-up approaches. When you pull the collective up but the helicopter keeps descending, the dynamics of what's happening are pretty moot. Who cares?

1. Does wind always blow horizontally, or can there be vertical components that might affect and compromise that scientific and sacrosanct "300 fpm" RoD that people think is so vital and absolute in exciting VRS? (Exciting it, not exiting it.)

2. People talk about "overpitching." Will a B3 droop its rotor if you pull 100% power?

Argue on, my brothers. Me, I'll just keep laughing and landing into the wind, thank you. Which is what our foolish Astar pilot should have done. (Or at least, if he knew that he had a ripping tailwind and needed to go into that spot anyway, he should have performed the technique properly. Sadly, he - or she! - knows that now.)

Repeat after me: "It doesn't matter how many hours you have; helicopters are very easy to crash." Learn it, live it.

[Robbiee]

I have been in full VRS with a ROD of 3000 ft a minute, scary !

What were you doing that got you into it?

[staycalm]

Staycalm, 300ft rate of decent, just pull the collective and the aircraft will climb, so not VRS. Dont believe it come to UK and I will show you ( or read Nick Lappos post many years ago ). Feel it, oh yes you do, before you ask, Yes I have been in full VRS with a ROD of 3000 ft a minute, scary !The reason you got to 3000'/min was because you remained in the aerodynamic condition of VRS that started around 300'/min.

If you say that you can add power as RoD exceeds 300'/min and recover (while maintaining the attitude I described), I won't disagree with you as long as you acknowledge that it takes a lot more power than it normally would (VRS has reduced the efficiency of the rotor system). That's just the approximate point at which a change of attitude becomes necessary to effect recovery from VRS.

And yes, I'm sure you are feeling things at 3000'/min. I don't see much training value beyond half that. The proper response is the same. Unless your experience was an intentional demo, it's hard to imagine why someone would be dinking around at high altitude/low airspeed to allow room to get that extreme and still be able to recover.

I won't deviate from the intention I had in my original message. Others can argue semantics and personal terminology preferences.

[Hughes500]

Robbie, junior instructor teaching it, came with 100 ft of hitting the ground from 2000 ft . A distinct brown trouser moment

[Sir Korsky]

Looks like he came in at top end torque and had nothing left to arrest the decent with. First class lesson in power management.

[SASless]

Nubian posted the following:

As for relevant info for this thread.
METARs UTC -6 DST
CYET 050156Z AUTO 16022G32KT
CYET 050211Z AUTO 17016G34KT

Runway is 07/25 and the buildings in the background are located on the north side of centreline.


Looking at the smoke trail post impact....it does appear to be a downwind approach across the runway (if the wind was as posted and the smoke trail representing the wind direction....and approach direction).

If one assumes an average wind of 165/19 gust to 33knots the question begged is why would any experienced pilot make a downwind approach to an airfield with such winds being reported and discernible by means of the wind sock and other visual indicators?

All this talk about VRS etc ignores the root cause of the accident.

Is there a rearwards flight airspeed limitation on the aircraft involved?

Could a flat approach with gradual deceleration have worked?

If one tried an OGE hover at altitude.....could VRS be avoided or escaped by accelerating rearwards out of the rotor downwash column of air?

Playing the "what if" game as is being played....why not debate this line of thought.

If you are not descending into your downwash....does it matter which direction you are moving re VRS?

[Rotorbee]

SASless (BTW where is that nice lady that always called you SASSY Darling), you are certainly right, the root cause of the accident has nothing to do with VRS or overpitching. Robbiee said it, FH1100 and others. But VRS is such a nice subject to disagree on. And in the final report, there will be the reason, why he choose that kind of approach. Maybe it was mandatory, or he was confident enough to be sure to pull it of? We will see.
The rotor does not care which direction you go to get out of VRS, but do you really want to bring the disk closer to the tail boom by going backwards, when flapping is easily double the normal amplitude? Even worse with gusty winds?

[[email protected]]

He could have avoided the crash in many ways, making his approach to the spot into wind being the most simple.

However, life and ATC aren’t always that simple and he could have made the same downwind approach safely by coming in slower and more shallow and getting the power in early and keeping the RoD nicely under control providing he had OGE performance plus a decent excess above that figure, say 10-15% Tq in hand.

Or, approach to the left of the spot, but not steep, and make a gentle right turn maintaining ETL until getting an into wind component - a curving approach.

I won’t be surprised if fatigue features in the accident analysis, its insidious nature can cause competent pilots to make very poor decisions and if you are single pilot you have no one to recognise your fatigue level.

[SASless]

Had the aircraft been parked facing down wind could it have been started and brought to a hover to begin a flight with such a wind of the strength and direction?

Or, would flying be cancelled for the day if there was no way to turn it around using ground handling wheels?

[Nubian]

Had the aircraft been parked facing down wind could it have been started and brought to a hover to begin a flight with such a wind of the strength and direction?

Or, would flying be cancelled for the day if there was no way to turn it around using ground handling wheels?

Yes, no doubt with a normally experienced 350 pilot.

Starting and stopping wind envelope is 40kts from any directions, 50 in headwind. The 350 has an extremely good t/r authority and very capable in tailwind conditions compared to the competetors in the class.

[Fun_police]

I won’t be surprised if fatigue features in the accident analysis, its insidious nature can cause competent pilots to make very poor decisions and if you are single pilot you have no one to recognise your fatigue level.


Yes, quite possibly. Northern Alberta has been experiencing a very active early fire season and fatigue might well be a contributing factor. Having said that though, if working fires and returning to an airport on a windy day like that if the pilot was unaware of the wind strength and direction (even without the aid of a wind sock etc etc), then one has demonstrated a total lack of situational awareness.
I have read on another site who the owner/operator is and being a small company with 206’s plus that one Astar suggests that there might have been a new 350 pilot who was enjoying the power and flexibility that a 206 does not offer and got caught…(this is not meant as a slam directed at the outfit; there’s no reason why they can’t provide a quality service based on size alone).
That is supposition on my part but I can’t imagine why someone would make such a poor decision.
Hopefully the pilot makes a full recovery, is able to move on past this and may we all remember that no amount of power will let you get away with mistakes of this magnitude…

[[email protected]]

Yes, no doubt with a normally experienced 350 pilot.

Starting and stopping wind envelope is 40kts from any directions, 50 in headwind. The 350 has an extremely good t/r authority and very capable in tailwind conditions compared to the competetors in the class. yes the conditions were well within the capabilities of the aircraft as Nubian says. I have taught downwind approaches in similar conditions in a 350 to a pretty basic student.

[staycalm]

Looks like he came in at top end torque and had nothing left to arrest the decent with. First class lesson in power management.

Torque doesn't do much good if it's handed to a rotor system that is operating at a fraction of its normal capacity. At 3,000' an Astar has plenty of power to arrest the rate of descent seen in the video, even if it were full of fuel and pax. In this case, the pilot was the sole occupant, and was returning at the completion of a flight, so probably not close to a full load of fuel. I'm sure the pilot pulled up on the collective, the blades pitched as far as they could go, and that the engine maintained Nr near 100% to impact. (at least there's been no mention so far of a mechanical issue) The pilot didn't need more power to arrest the descent. The rotor system needed "clean" air (VRS recovery).

If you're driving up a steep icy hill, it doesn't do any good to mash the throttle. The engine roars and the wheels spin, but if the tires have no traction, gravity will win.

[helispotter]

Good (please insert your preferred deity here) H500. Do you really want to trigger that discussion again?
...EASA has initiated a research program to find out what it is all about.
VRS (Helicopter Vortex Ring State Experimental Research) (https://www.easa.europa.eu/en/research-projects/vrs-helicopter-vortex-ring-state-experimental-research)
Now we can lean back and wait for the results.

I have noticed topics of VRS and LTE seem to get some PPRUNEr's really worked up. I haven't yet read the old threads where these topics have apparently been done to death so perhaps not yet jaded by the topics.

I did read the link to the EASA VRS experimental study. It mentions "shall include an experimental flight test activity on at least two different helicopter types having different kinds of main rotor systems". It occurs to me that with all the fantastic scale model helicopters now available, complete with scale rotorheads and small gas turbines, experimental program could be conducted at model scale where risks to people are negligible (unless a model tumbled on their head in full VRS). Model mass dynamics as well as control system and engine responses 'just' need to be properly scaled. That should be possible as I have worked in a similar field of scale model testing, not aviation. A model test program (at least initially) should also permit a wider spread of helicopter types and load states (eg: rotor disk loadings) at a much lower cost. This doesn't stop subsequent (careful) verification of findings at full scale on a more limited number of cases.

[Rotorbee]

@helispotter: I very much doubt, that a model helicopter would be appropriate for this kind of test. The problem does not lie in the mass and engine response, but in the dynamics of the main rotor. Building a scaled down model of the rotor with all the correct flexing and flapping isn't as easy as it sounds. The commercially available models lack a lot of components of a real rotor. No flapping- or lead/lag hinges for example. Not even virtual hinges in the blade root. Model helicopters do not need that. And then there is the Reynolds number.
But it has been done to visualise VRS in wind tunnels. But here they want to fly certain manoeuvres and that is difficult in a wind tunnel.
The budget isn't very high. I think for that money it is cheaper to use a real helicopter.

[Sir Korsky]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit as that little tail rotor tries to keep you straight. To stop a violent weather vane once you run out of tail rotor authority, you may try and reduce the pitch to stop the spin. Maybe he just realized he had no foot left, was close to the ground and let nature take over.

[RVDT]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit as that little tail rotor tries to keep you straight.

Did you actually think this through or is it an assumption or personal experience?

[Sir Korsky]

Go out and try it !

[MightyGem]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit
​​​​​​​What???

[staycalm]

We're being trolled. ;)

[Agile]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit as that little tail rotor tries to keep you straight. I think there is a point there, it is just inaccurately expressed. If you approach at 30 knots with a reasonable rate of descent, expecting to be on the front end of the power curve, lightly above ETL and doing everything right.
with downwind, you might be on the back end of the power curve, with no induced flow and a very inefficient rotor system. as you slow down to a hover you will eventually have tail wind (beneficial to the induced flow and the rotor system effectiveness).
In this case he did not make it to having downwind on the aircraft.

A good pilot will realize the mistake by the level of vibration and the power setting being above usual, at that point in the approach but when you are tired and just want to wrap up your job things like that happen.
having a powerfull airframe will aslo mask out the early sign, Do that in an R22 with an overweight instructor and there is not much to save you, but the early signs will be comparatively amplified.

[[email protected]]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit as that little tail rotor tries to keep you straight. To stop a violent weather vane once you run out of tail rotor authority, you may try and reduce the pitch to stop the spin. Maybe he just realized he had no foot left, was close to the ground and let nature take over.
The main rotor doesn’t care which way the wind is coming from so no increase in power required there.

The tail will be more twitchy and you may need more yaw inputs to maintain the heading, especially in a gusty wind.

Being weathercocked back into wind is a real danger, but that’s not at all what it looks like happened in this case.

Downwind approaches - get the ground speed off early, keep the RoD under control and go around early if you are struggling to maintain your desired flight path or keep within power limits. It’s not rocket science.

[FH1100 Pilot]

Being weathercocked back into wind is a real danger, but that’s not at all what it looks like happened in this case.

It's not a "danger," it is a fact of helicopter life. Helicopters are big weathervanes: They like to point themselves into the wind. I think I even heard ol' Igor himself reply, "Well, DUH!' when I mentioned that to him. He even added, "Comrade student pilot, do not land with tailwind. If you FA, you will FO." See, Igor knew. And he was pretty hip!

As long as the dumb meat-servo at the controls keeps these things in mind, he'll be okay and won't be surprised when the inevitable happens. Hovering with a strong tailwind is do-able, but you must, must, MUST be ready for the ship to want to swap ends. And, if you're even slightly late on the pedal application, you might not be able to prevent it. Crab is right that making an approach with a strong tailwind is do-able - with the proper technique - a technique that was, evidently and sadly, not imparted to our hapless Astar pilot. "Wait, what? You mean I was supposed to slow down and get through translation again FROM THE REAR?? That's insane!" Again, these are facts of life that all helicopter pilots should understand but many, obviously, do not.

[Robbiee]

..Crab is right that making an approach with a strong tailwind is do-able - with the proper technique - a technique that was, evidently and sadly, not imparted to our hapless Astar pilot. "Wait, what? You mean I was supposed to slow down and get through translation again FROM THE REAR?? That's insane!" Again, these are facts of life that all helicopter pilots should understand but many, obviously, do not.

I hear that some pilots these days don't believe in LTE. So, maybe that's why? :E

[Rotorbee]

I hear that some pilots these days don't believe in LTE. So, maybe that's why? :E

That is, because LTE is mostly a Bell problem, it seams. Apparently, I could be wrong here, the first 206' had a very weak tail rotor. Later models hat less problems.
You can get a vortex around your tail rotor in a tail wind, that swaps you around. Even in a Robinson. Frank was a master of the tail rotor, and Robinson helicopters have very good tail rotor authority. Even so, you can get in trouble in a tail wind, but with a slight wiggle on the cyclic, you can fix that (my own experience). Everything with a normal tail rotor from Airbus, has reportedly very good tail rotor authority. The rumor is, that only Bell pilots experience LTE and Bell invented the term.

[henra]

If you try and hold a stationary hover with a 30 knot tailwind, your collective will be up in your armpit as that little tail rotor tries to keep you straight.
I'm not sure I fully got your point. If you are in a stationary hover vs the ground while facing a 30kts tailwind your main rotor will be merrily working at 30kts relative airspeed. Silghtly above ETL, below high drag area. That is the spot where it will need about the lowest power throughout the whole envelope. So for the collective this will be the opposite of armpit.
That said, at the tail the situation will be vastly different. If not super quick on the pedals you will quickly have to test the stops in order to avoid playing sun and have the Earth rotate around you.

[Robbiee]

That is, because LTE is mostly a Bell problem, it seams. Apparently, I could be wrong here, the first 206' had a very weak tail rotor. Later models hat less problems.
You can get a vortex around your tail rotor in a tail wind, that swaps you around. Even in a Robinson. Frank was a master of the tail rotor, and Robinson helicopters have very good tail rotor authority. Even so, you can get in trouble in a tail wind, but with a slight wiggle on the cyclic, you can fix that (my own experience). Everything with a normal tail rotor from Airbus, has reportedly very good tail rotor authority. The rumor is, that only Bell pilots experience LTE and Bell invented the term.

LTE is one of those things that teaches us that different wind angles can require more attention on our part. Besides, it doesn't matter how awesome your tail rotor is, if your feet are alseep on the pedals. Just as it doesn't matter how much extra power your fancy French chopper has, if you wait too long to use it.

[helispotter]

@helispotter: I very much doubt, that a model helicopter would be appropriate for this kind of test... Building a scaled down model of the rotor with all the correct flexing and flapping isn't as easy as it sounds... And then there is the Reynolds number... The budget isn't very high. I think for that money it is cheaper to use a real helicopter.

Rotorbee: There are some very large and seemingly accurately scaled RC helicopters around these days. I accept these are not models that can just be bought over the counter. Take as an example this 1:2.6 scale SA-315B Lama: https://www.youtube.com/watch?v=E1uVIDL8j8Q

The rotor head on this model seems relatively scaled to me? Yes, perhaps the rotors themselves are stiffer (in relative terms) than a full scale Lama as they don't droop/sag much when rotor is stationary but it would seem fairly trivial to adjust stiffness of model blades using a different material. In any case, I wonder how much the stiffness of blades comes into influencing the dynamics of a VRS and getting out of it? While it might be more complex to accurately model 3+ blade rotorheads on scale models, it seems relatively trivial on 2 blade helicopters, of which there are of course many! I accept the Reynolds Number will be less than full scale, but no longer substantially so once you have a decent size model. Just as with blade stiffness, I wonder how much the Rn is actually influencing dynamics of a VRS? I appreciate Rn influences profile drag and lift coefficient at larger AoA. I accept it might actually be more straightforward to instrument a full scale helicopter for such a research project than to do so on a model. I was mainly thinking about reducing the risk of an accident involving aircrew if they deliberately seek out VRS conditions. I guess if you have altitude on your side to conduct experiments, the risk is managed...

[RVDT]

Be cheaper to find an expired Lama and fit the RC bits to it!

[helispotter]

Be cheaper to find an expired Lama and fit the RC bits to it!

Along these lines but without the control cable: :O

H21 Helicopter Controlled Crash Tests (video only) - YouTube

[Rotorbee]

@Robbie: I only gave you the history of LTE, not an argument against or for anything. If you have lazy feet in almost anything that flies, except probably for the original Ercoupe, you will get in trouble. Even with a headwind.
Can I refer you to Nick Lappos amazing thread about Helicopter Urban Myth (https://www.pprune.org/rotorheads/158490-helicopter-urban-myths.html)? A very interesting read. There are quite a few threads about LTE in Pprune.
@helispotter: Have it your way, but I am pretty sure, that those scale heads do not have lead/lag- or flapping hinges. Anyway, building an accurate model with all the instrumentation necessary fitted, would probably eat up the whole budget and take ages. The contract is for only two years. I am pretty sure Onera is up to the task doing it safely. They have already done some work on VRS a few years ago and can build on that.

[[email protected]]

I'm not sure what further modelling of VRS will achieve - its existence is well documented and we know that avoiding flight regimes where low IAS is coupled with allowing a significant RoD and application of power will keep us clear of it.

Maybe pilot training isn't what it was or newer pilots have been spoiled with such powerful and capable helicopters compared to 50 years ago but of all the very many helicopter pilots I know or have flown with, few have experienced LTE and even fewer (probably 2 or 3) have experienced VRS.

Maybe it is a function of the modern generation that they can't accept what they have been told by the old guys, they have to find out for themselves and won't be happy until there is a VRS or LTE App for their I-phones to keep them out of trouble.

[helispotter]

After this I stay quiet about RC helicopters for research, but earlier I did to a bit of basic searching on the internet and found out that drone / quadcopter manufacturers such as DJI apparently limit the rate of decent in their newer drone models in an effort to prevent occurrence of VRS. I also came across this video (and others) which suggest drone is caught in VRS condition in the footage shown:https://youtu.be/q3jhYhBn_NQ

Perhaps more interesting, in a discussion about drones and VRS, there was a link to this full scale AS350 accident footage from inside the helicopter. Title on YouTube attributes accident to VRS but description and comments provide few other details:

https://youtu.be/mP72wdgq5PU

I tried to work out which helicopter it was. While N4075S is shown earlier in the footage, this doesn't seem to be the one involved in the accident which instead may have registration N?094S which is partly visible on cowling towards the end of the video. These helicopters appear to be operated by Sunshine Helicopters in Hawaii. ASN reports on the accident of N6094H in Hawaii on 17 June 2014 which sort of fits the description in this video, but the "H" in rego doesn't match rego seen in footage and the video was apparently posted 1 June 2012 so accident must pre-date it. Anybody know this case? Perhaps it has been discussed to death on PPRuNe already, but I couldn't find a thread after some key word searching.

[212man]

Perhaps more interesting, in a discussion about drones and VRS, there was a link to this full scale AS350 accident footage from inside the helicopter. Title on YouTube attributes accident to VRS but description and comments provide few other details:

https://youtu.be/mP72wdgq5PU

I tried to work out which helicopter it was. While N4075S is shown earlier in the footage, this doesn't seem to be the one involved in the accident which instead may have registration N?094S which is partly visible on cowling towards the end of the video. These helicopters appear to be operated by Sunshine Helicopters in Hawaii. ASN reports on the accident of N6094H in Hawaii on 17 June 2014 which sort of fits the description in this video, but the "H" in rego doesn't match rego seen in footage and the video was apparently posted 1 June 2012 so accident must pre-date it. Anybody know this case? Perhaps it has been discussed to death on PPRuNe already, but I couldn't find a thread after some key word searching.
Maybe this one and the earlier portions of the event are missing in the video. Picture quality looks like 2000! It was also a definite loss of power event and nothing to do with VRS, I'd say. https://aviation-safety.net/wikibase/30181

[Nubian]

Maybe this one and the earlier portions of the event are missing in the video. Picture quality looks like 2000! It was also a definite loss of power event and nothing to do with VRS, I'd say. https://aviation-safety.net/wikibase/30181

Not that one.

But this, N6094S (https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20001212X19565&AKey=1&RType=Final&IType=LA)

Same company though

[Robbiee]

@Robbie: I only gave you the history of LTE, not an argument against or for anything. If you have lazy feet in almost anything that flies, except probably for the original Ercoupe, you will get in trouble. Even with a headwind.
Can I refer you to Nick Lappos amazing thread about Helicopter Urban Myth (https://www.pprune.org/rotorheads/158490-helicopter-urban-myths.html)? .

Hmm,... I'm unfamiliar with those myths. I guess they never made it to Arizona,..where I got my license. :eek:

[[email protected]]

Not that one.

But this, N6094S (https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20001212X19565&AKey=1&RType=Final&IType=LA)

Same company though
That one is definitely SWP and not VRS

[Rotorbee]

That one is definitely SWP and not VRS

Yup. Definitely not.

[albatross]

That one is definitely SWP and not VRS

I respectfully disagree but also think we’ve danced around the maypole enough about this event.

i am sure a report will be forthcoming.

”If I’m getting smaller it means I’m leaving.”

[[email protected]]

I respectfully disagree but also think we’ve danced around the maypole enough about this event.

i am sure a report will be forthcoming.

”If I’m getting smaller it means I’m leaving.”

I'd be interested in your reasons for disagreeing albatross - for me the low Nr horn is a significant indicator of overpitching and asking for a collective pitch position that the engine can't provide enough power for.

SWP can lead to VRS but the fact they survived the impact would lead me to believe the RoD was not that of fully developed VRS.

[Hughes500]

I m with Crab here, having experienced full vortex ring once ( a real brown trouser moment ) what you see from inside is nothing like I saw. The ground comes up at an alarming rate, what you see is a slightly hire than normal rate of descent with not enough power to stop, basically crap energy mangement !

[Robbiee]

You guys always get too hung up on the effect. The cause here was just another tailwind approach using the wrong technique.

[albatross]

I'd be interested in your reasons for disagreeing albatross - for me the low Nr horn is a significant indicator of overpitching and asking for a collective pitch position that the engine can't provide enough power for.

SWP can lead to VRS but the fact they survived the impact would lead me to believe the RoD was not that of fully developed VRS.

I have not seen any video from inside the accident aircraft in Edson. Please post a link.
Also overpitching the collective to a position in your armpit is often a reaction to sudden, low level, VRS especially if the planet is fast approaching. This massive over-torque will lead to the low rotor horn and an accelerated rate of descent.

[[email protected]]

albatross - I believe we are talking at cross-purposes here.

My comments about SWP are not to do with the Edson crash at all - that was VRS in my opinion.

The two other 350 links, one to a cockpit video and the other to the N6094s accident report are both SWP I believe but may well be separate accidents.

[helispotter]

Thanks 212man and Nubian for looking for reports of the accident seen in the video linked in my post #78. The NTSB report found by Nubian certainly fits the bill as the portion of registration seen in video is consistent with N6094S.

This case doesn't turn up in ASN database no matter how I try to search for it. I also couldn't find details of that helicopter (c/n 2722) on helis.com database. Even though it occurred on 24 Aug 1999, the video wasn't posted to YouTube until 2012. NTSB report indicates: "...the probable cause(s) of this accident to be: The pilot's initial misjudgment of the wind speed and his decision to continue a downwind landing approach when his speed and altitude profile was inadequate, and his failure to maintain main rotor rpm, resulting in settling with power and a hard landing."

I haven't followed the distinctions being made in the more recent comments here. From what I had picked up from earlier discussions including on other threads, I thought SWP and VRS are just different expressions for the same situation? Sorry in advance if I am opening an old can of worms.

[[email protected]]

I thought SWP and VRS are just different expressions for the same situation? Sorry in advance if I am opening an old can of worms. No, that is what was taught and promulgated in some regions - particularly the US but they all seem to understand the difference now.

Settling with Power effectively means running out of power because the aircraft doesn't have the performance to do what you are asking of it - usually in the low speed environment and associated with the loss of ETL ie trying to establish an OGE hover or making a steep approach into a landing site without the performance to do so. Low Nr is a classic symptom because the pilot keeps pulling the collective up as he/she realises they can't stop the descent.

VRS is all aerodynamic and involves recirculation at the blade tips and stalling at the blade roots leaving only the middle part of the blade producing useful lift - it is also encountered in the low speed environment which often leads to the confusion. You have caught up with your own downwash and the rotors really don't like it.

In full VRS the outcome is usually fatal due to the high rate of descent - in SWP often the aircraft gets bent with minimal or minor injuries because the rate of descent is lower.

​​​​​​​In both conditions, continuing to raise the collective just makes things worse - in SWP you just decay the Nr further - in VRS you worsen the recirculation and the root stall.

Both conditions are easily avoided and encountering either is usually the result of poor performance planning, poor wind awareness or simply poor piloting.

[albatross]

albatross - I believe we are talking at cross-purposes here.

My comments about SWP are not to do with the Edson crash at all - that was VRS in my opinion.

The two other 350 links, one to a cockpit video and the other to the N6094s accident report are both SWP I believe but may well be separate accidents.

Ah Crab …the light. has illuminated.
My failure to take into account “Thread Drift”.
Silly me!
Cheers
Albatross.
PS When I typed Crab..Spell Check changed it to Crap. Funny! Glad I caught that error.

[FH1100 Pilot]

Thanks 212man and Nubian for looking for reports of the accident seen in the video linked in my post #78. The NTSB report found by Nubian certainly fits the bill as the portion of registration seen in video is consistent with N6094S.

This case doesn't turn up in ASN database no matter how I try to search for it. I also couldn't find details of that helicopter (c/n 2722) on helis.com database. Even though it occurred on 24 Aug 1999, the video wasn't posted to YouTube until 2012. NTSB report indicates: "...the probable cause(s) of this accident to be: The pilot's initial misjudgment of the wind speed and his decision to continue a downwind landing approach when his speed and altitude profile was inadequate, and his failure to maintain main rotor rpm, resulting in settling with power and a hard landing."

I haven't followed the distinctions being made in the more recent comments here. From what I had picked up from earlier discussions including on other threads, I thought SWP and VRS are just different expressions for the same situation? Sorry in advance if I am opening an old can of worms.
Ohhh, you just have to know where to look:
Report_LAX99LA282_47145_5_20_2023 9_41_50 AM.pdf (file:///C:/Users/rbarb/Downloads/Report_LAX99LA282_47145_5_20_2023%209_41_50%20AM.pdf)

The ship must not have been damaged too badly, because the ROTORSPOT database still shows it as still owned by Sunshine, still active and not withdrawn from use or written off or whatever.

It's interesting (to me, at least) that the PIC reported a total time of 11,871 hours, with 8,347 in that actual make/model! So much for experience being helpful in avoiding accidents, eh? Hah. I've said it before and I'll say it again: Helicopters are VERY EASY to crash. And having a ****load of time gives you no immunity or even protection from doing so, despite what you might egotistically believe about yourself and your mad skillz as a pilot. And it gets back to what I've said about landing/taking-off into the wind: After we get our PPL and get out in the world, we get to thinking that it's not *that* important anymore...that we can handle a downwind landing...easy-peasy!...done it a million times....OOPS! Another one bites the dust, hey-hey!

[Robbiee]

No, that is what was taught and promulgated in some regions - particularly the US but they all seem to understand the difference now.

Settling with Power effectively means running out of power because the aircraft doesn't have the performance to do what you are asking of it - usually in the low speed environment and associated with the loss of ETL ie trying to establish an OGE hover or making a steep approach into a landing site without the performance to do so. Low Nr is a classic symptom because the pilot keeps pulling the collective up as he/she realises they can't stop the descent.

Yeah, I admit I've been confused as to what you actually mean everytime you guys use this antiquated term. In fact, I actually thought you were referring to the Canadian definition, where you just wait too long to start slowing down.

If you just said, "overpitching", or "he's just too heavy to go that slow", there wouldn't be any confusion.

[albatross]

Yeah, I admit I've been confused as to what you actually mean everytime you guys use this antiquated term. In fact, I actually thought you were referring to the Canadian definition, where you just wait too long to start slowing down.

If you just said, "overpitching", or "he's just too heavy to go that slow", there wouldn't be any confusion.

Overpitching? You can be overpitching and climbing like a homesick angel. Of course this can lead to Over torque, over temp, N1 topping, Loss of RPM, loss of tail rotor authority ect. ect. including meetings with the Chief Pilot where no tea and cookies will be offered and severely PO’d maintenance staff
I’ ll will stick to my antiquated terminology for 2 completely separate conditions of flight.
Vortex Ring State and Settling With Power were always referred to and taught separately when i got my licence here in Canada.
Yes, one can lead to the other but they are not the same.
Sorry if you are confused.

[Robbiee]

Overpitching? You can be overpitching and climbing like a homesick angel. Of course this can lead to Over torque, over temp, N1 topping, Loss of RPM, loss of tail rotor authority ect. ect. including meetings with the Chief Pilot where no tea and cookies will be offered and severely PO’d maintenance staff
I’ ll will stick to my antiquated terminology for 2 completely separate conditions of flight.
Vortex Ring State and Settling With Power were always referred to and taught separately when i got my licence here in Canada.
Yes, one can lead to the other but they are not the same.
Sorry if you are confused.

If you're overpitching you won't be climbing for long, lol.

​​​​Anyway, I'm only confused because the term has at least three different definitions depending on where the pilot using it was trained.

How about this, if you're so dedicated to using this term, then could you at least specify which country you are from, so there's no confusion (and/or resulting arguments) over what you actually mean?

[FH1100 Pilot]

Yes, one can lead to the other but they are not the same.
The outcome almost always is.

If you get into one of those situations where the helicopter goes down faster as you pull up more on the pole, then you'll do one of two things: 1) If you're high enough, recover using Vuichard or some other technique and then come on PPRUNE and swear to us that you got SWP or VRS and tell us why; or 2) Crash. If you select Option #2, it won't matter whether it was SWP or VRS.

[helispotter]

crab and albatross: thanks for the SWP vs VRS distinction. Out of interest, I looked through BASI Aviation Safety Digest issues to see what terminology they had used. ASD 68 from 1970 has an article discussing a ​​​​Bell 47G-3B-1 crash in New Zealand attributed to Vortex Ring State or Power Settling as if the two are interchangeable terms:https://www.atsb.gov.au/sites/default/files/media/5774765/asd_68_may_70.pdf

ASD 51 of 1967 discusses accident with a Bell 47-G2 in Western Australia, but in that case it is attributed simply to overpitching:

https://www.atsb.gov.au/sites/default/files/media/5774748/asd_51_jul_67.pdf

FH1100 Pilot: Thanks for looking up the fate of N6094S. It would have been an expensive repair. The pdf document link you provided didn't work for me though.

[Ascend Charlie]

Sorry it's a long post, but for the benefit of Robbiee and his mates, here is a gathering of Nick Lappos's Urban Myths, plus some notes from the late Shawn Coyle, both these gents being highly qualified test pilots:Helicopter Urban Myths
These Urban Myths pervade our understanding of helicopters and how they operate. Each is fundamentally incorrect, but most are generally held as gospel, because training, lore and reference documents have repeated them long enough that they are simply accepted.
1) Vortex Ring State (VRS) can happen at as little as 300 foot per minute descent, it does not have to be a higher descent rate
2) VRS is more likely at high altitude and high gross weight
3) Hovering with the nose off wind consumes much more power
4) Blade stall is always preceded by vibration
5) Winds affect the power we require when we are in forward flight
6) Downwind takeoffs are absolutely forbidden
7) The Height Velocity curve is a precise guide to the engine failure danger zone
8) Engine failure is the most common accident cause, so full CAT A is the most cost effective safety enhancement we can incorporate into new helicopters.
9) The legal definition of VFR is sufficient to assure flight control and safety using outside references
10) "They" sometimes hide things from us. We should not trust them, the only reliable information we can trust is our own wits.
11) The helicopter is perched on a ball of high pressure air when close to the ground, and "falls off" this ground cushion when it moves forward.
12) Phase lag is cause by gyroscopic precession, and is always exactly 90 degrees
13) LTE is when you run out of power pedal and can be experienced by any single rotor helicopter.
14) NVG are dangerous and should only be used by gifted military pilots.
15) You have to first learn to fly fixed wing before you take helicopter training
16) Torque limits, overspeed limits, temperature limits, hours and airframe limits have huge safety factors built into them by the engineers, so it is OK to bust them every now and then.
Davy07,
The books say so, but they are quite wrong. VRS can only be induced by descending at least as fast as 75% of the downwash velocity of the helicopter and at a forward speed of not more than about 8 knots. For a Robbie this is at least -750fpm rod. For an S76 it is about -1500 fpm.

Why is 300 taught? Because one can start a VRS event by entering a hover with too little power, slip into an overpitching event and in short order, enter VRS. In a helo with scads of OGE hover performance, the 300 fpm is truly a myth, in one without, it is misleading as a VRS cue, but good word as an overpitching warning.

Manfrom Uncle, what you are correctly saying is that going faster uses more power. The wind has nothing to do with it. 80Kts airspeed uses the same power both up and down wind.
For the record, there is no pressure gradient below the rotor, in fact, that lame conventional explanation doesn't even hold water for a millisecond when you realize that ground effect only works on the induced power. How does a "pressure bubble" single out induced power as the only recipient of its wonder?
In fact, pressure bubblers have some difficulty explaining how ground effect works for an airplane at 250 knots, when the "pressure bubble" is about 1/4 mile behind the wing.

Maybe you should get a hold of Shawn Coyle's "Cyclic and Collective":

http://i159.photobucket.com/albums/t145/CNN77/Low-Altitude-Vortex.jpg?t=1195957331

Dear Shawn, Mr. Publisher, dear mods: if this should violate any copyrights and isn't appreciated to be posted, please remove it immediately or have me remove it - I just can't explain it better )
delta 3,

OK, your work is truly great, and I can see the reduction on angle of attack and power. It is truly a desktop universe, and I mean that in a good way.
The problem is that without careful explanation, one could actually think you show how the "pressure bubble" under the rotor is what ground effect is, and that would be untrue. Ground effect is when the ground plane flattens out the flow, causing the rotor to behave as if the blades were much longer. As a result, the tip losses for the blades are sharply reduced, causing a sharp reduction in the induced power requirements. The reason why ground effect does not show very well at 100 knots is that induced power is very low there, but ground effect is still present at 100 knots.

For an airplane, the case is easier to picture. As the wing comes down into ground effect, the tip wash reduces sharply, and the wing behaves as if it were infinitely long. This requires less angle of attack (which had caused a large drag rise prior to entering the ground effect). The induced drag wastes power, so ground effect shows itself as a reduction in angle of attack and a reduction in the power required.
Ground effect is not caused by a pressure rise, nor is the advantage to the aircraft due to any pressure that pushes the aircraft up (or any other such pressure bubble nonsense.)

Ground effect explained
Misinformed Instructors who propel the pressure bubble myth should be asked to do a quick Yahoo search using "induced drag ground effect" so that they can learn how to tell their students the truth, and not convenient myths. We would be all the better for it. Pressure bubblers, please note:

Induced drag explained:

http://galileo.phys.virginia.edu/cla...ero/node5.html (http://galileo.phys.virginia.edu/classes/311/notes/aero/node5.html)

http://www.grc.nasa.gov/WWW/K-12/airplane/induced.html (http://www.grc.nasa.gov/WWW/K-12/airplane/induced.html)

Ground effect explained:

http://www.faatest.com/books/FLT/Cha...oundEffect.htm (http://www.faatest.com/books/FLT/Chapter17/GroundEffect.htm)

http://www.pilotfriend.com/training/...g/aft_perf.htm (http://www.pilotfriend.com/training/flight_training/aft_perf.htm)

"Many pilots think that ground effect is caused by air being compressed between the wing and the ground. This is not so. Ground effect is caused by the reduction of induced drag when an airplane is flown at slow speed very near the surface."

The quiz for today, for the bright student:

Define induced drag

define aspect ratio

explain how aspect ratio affects induced drag

explain how proximity to the ground affects aspect ratio

I love this block, we can go round and round it forever!

Some points:

1) I never said that ground effect was a myth, I said that the "pressure bubble" was a myth! Ground effect is very real, and amounts to a typical 15% power savings for most helicopters (where the rotor cannot get closer to the ground that about .3 radius.

2) Those who love the pressure bubble theory are welcome to it, believing myths is not against the law! However, ask yourself why ground effect disappears when you hover over long grass - and don't tell me that grass absorbs pressure! The grass slows the outflow, which is the mechanism that changes the blade angle of attack and reduces the hover power.

3) The pressure bubble theory cannot explain why ground effect only reduces the induced drag of the blades, if that theory is correct, more velocity makes more pressure, and thus saves more power. If the air velocity gets banged against the ground, and pressure builds, then a higher velocity should make even more pressure, and more ground effect, right? No, wrong! Maximum ground effect is about +15% power, regardless of how fast the downwash velocity is. In fact, ground effect is no different for highly loaded rotors, with faster downwash, than it is for low disk loading rotors with gentle downwash.

4) If pressure bubbles push the aircraft up, then high speed airplanes, with the wake hitting the ground hundreds of meters behind the aircraft, should see no ground effect. But they do! That is because the effect is on the wing, where the angle of the flow around the wing is changed by the presence of the ground.

5) Ground effect makes the wings or blades act as if they are longer, and this cuts the tip losses that make the induced drag. They have nothing to do with the pressure under the blade or wing, they have everything to do with the reduction in outflow, and the reduction in the tip vortex pattern due to that outflow.

With my respect for Shawn unabated, I must respectfully disagree with him. There is a meaningful difference between the two cases, light vs heavy. But first we must clarify what we mean by Vortex Ring State (VRS) - and what is meant by a different problem called "Settling with Power (SWP)" or "over pitching" or "insufficient power to Hover OGE"
Most accidents where a hovering helicopter falls and crashes and VRS is blamed are actually cases of SWP or over pitching, where the hover performance is marginal, and insufficient reserve power (power margin) is available to allow moderate climbs and descents while OGE. The aircraft "falls through" the hover, hits hard (usually with just a bent helicopter and bruised ego) and then someone says "It was VRS." Sometimes the mistaken person is an official accident investigator!

In a helicopter at high MGW, with only slight or no margin between the power needed to HOGE and the power available from the engines, "over pitching" is more likely than in a lightly loaded helicopter where lots of power above hover power is available. When lightly loaded, there is much extra power available above the hover power, so the lightly loaded helo is much less likely to experience "over pitching" and thus the lightly loaded helo is much less likely to be mistakenly labeled as a VRS accident.

Now the truth: Since true VRS involves the descent of the helicopter into its own downwash, and since in a light helicopter the downwash velocity is quite a bit less than in that same helicopter when heavy, a lightly loaded helicopter needs much less rate of descent to experience true VRS.
Thus, heavy helicopters require more descent rate to get true VRS, and so are less likely to enter that state, but heavily loaded helicopters have more over pitching power control accidents that are too often labeled "VRS", so the mistaken pilot lore says heavy helicopters are more likely to experience VRS.

For the record, no helicopter can experience true VRS unless it is descending nearly vertically at about 800 to 1000 feet per minute.
Also for the record, most helicopters can experience SWP or overpitching at rates of descent near zero if they have little hover power margin.
Also, heavily loaded helicopters have less propensity to enter VRS because they need more vertical descent rate than lightly loaded helicopters, which need less descent rate to get into VRS.

[[email protected]]

AC - most of those links don't work any more unfortunately.

I was lucky to find Nick Lappos and Shawn Coyle on these pages 25 years ago and have tried to pass on their wisdom where possible ever since.

[albatross]

There was a thread called “Vuichard Again” a while ago.
A lot of the points here were discussed there and by the same cast of characters….myself included.

https://www.pprune.org/rotorheads/626806-vuichard-again.html?highlight=vuichard

[Robbiee]

Sorry it's a long post, but for the benefit of Robbiee and his mates, here is a gathering of Nick Lappos's Urban Myths, plus some notes from the late Shawn Coyle, both these gents being highly qualified test pilots:Helicopter Urban Myths
These Urban Myths pervade our understanding of helicopters and how they operate. Each is fundamentally incorrect, but most are generally held as gospel, because training, lore and reference documents have repeated them long enough that they are simply accepted.
1) Vortex Ring State (VRS) can happen at as little as 300 foot per minute descent, it does not have to be a higher descent rate
2) VRS is more likely at high altitude and high gross weight
3) Hovering with the nose off wind consumes much more power
4) Blade stall is always preceded by vibration
5) Winds affect the power we require when we are in forward flight
6) Downwind takeoffs are absolutely forbidden
7) The Height Velocity curve is a precise guide to the engine failure danger zone
8) Engine failure is the most common accident cause, so full CAT A is the most cost effective safety enhancement we can incorporate into new helicopters.
9) The legal definition of VFR is sufficient to assure flight control and safety using outside references
10) "They" sometimes hide things from us. We should not trust them, the only reliable information we can trust is our own wits.
11) The helicopter is perched on a ball of high pressure air when close to the ground, and "falls off" this ground cushion when it moves forward.
12) Phase lag is cause by gyroscopic precession, and is always exactly 90 degrees
13) LTE is when you run out of power pedal and can be experienced by any single rotor helicopter.
14) NVG are dangerous and should only be used by gifted military pilots.
15) You have to first learn to fly fixed wing before you take helicopter training
16) Torque limits, overspeed limits, temperature limits, hours and airframe limits have huge safety factors built into them by the engineers, so it is OK to bust them every now and then.
Davy07,
The books say so, but they are quite wrong. VRS can only be induced by descending at least as fast as 75% of the downwash velocity of the helicopter and at a forward speed of not more than about 8 knots. For a Robbie this is at least -750fpm rod. For an S76 it is about -1500 fpm.

Why is 300 taught? Because one can start a VRS event by entering a hover with too little power, slip into an overpitching event and in short order, enter VRS. In a helo with scads of OGE hover performance, the 300 fpm is truly a myth, in one without, it is misleading as a VRS cue, but good word as an overpitching warning.

Manfrom Uncle, what you are correctly saying is that going faster uses more power. The wind has nothing to do with it. 80Kts airspeed uses the same power both up and down wind.
For the record, there is no pressure gradient below the rotor, in fact, that lame conventional explanation doesn't even hold water for a millisecond when you realize that ground effect only works on the induced power. How does a "pressure bubble" single out induced power as the only recipient of its wonder?
In fact, pressure bubblers have some difficulty explaining how ground effect works for an airplane at 250 knots, when the "pressure bubble" is about 1/4 mile behind the wing.

Maybe you should get a hold of Shawn Coyle's "Cyclic and Collective":

http://i159.photobucket.com/albums/t145/CNN77/Low-Altitude-Vortex.jpg?t=1195957331

Dear Shawn, Mr. Publisher, dear mods: if this should violate any copyrights and isn't appreciated to be posted, please remove it immediately or have me remove it - I just can't explain it better )
delta 3,

OK, your work is truly great, and I can see the reduction on angle of attack and power. It is truly a desktop universe, and I mean that in a good way.
The problem is that without careful explanation, one could actually think you show how the "pressure bubble" under the rotor is what ground effect is, and that would be untrue. Ground effect is when the ground plane flattens out the flow, causing the rotor to behave as if the blades were much longer. As a result, the tip losses for the blades are sharply reduced, causing a sharp reduction in the induced power requirements. The reason why ground effect does not show very well at 100 knots is that induced power is very low there, but ground effect is still present at 100 knots.

For an airplane, the case is easier to picture. As the wing comes down into ground effect, the tip wash reduces sharply, and the wing behaves as if it were infinitely long. This requires less angle of attack (which had caused a large drag rise prior to entering the ground effect). The induced drag wastes power, so ground effect shows itself as a reduction in angle of attack and a reduction in the power required.
Ground effect is not caused by a pressure rise, nor is the advantage to the aircraft due to any pressure that pushes the aircraft up (or any other such pressure bubble nonsense.)

Ground effect explained
Misinformed Instructors who propel the pressure bubble myth should be asked to do a quick Yahoo search using "induced drag ground effect" so that they can learn how to tell their students the truth, and not convenient myths. We would be all the better for it. Pressure bubblers, please note:

Induced drag explained:

http://galileo.phys.virginia.edu/cla...ero/node5.html

http://www.grc.nasa.gov/WWW/K-12/airplane/induced.html

Ground effect explained:

404 - File or directory not found. (http://www.faatest.com/books/FLT/Cha...oundEffect.htm)

http://www.pilotfriend.com/training/...g/aft_perf.htm

"Many pilots think that ground effect is caused by air being compressed between the wing and the ground. This is not so. Ground effect is caused by the reduction of induced drag when an airplane is flown at slow speed very near the surface."

The quiz for today, for the bright student:

Define induced drag

define aspect ratio

explain how aspect ratio affects induced drag

explain how proximity to the ground affects aspect ratio

I love this block, we can go round and round it forever!

Some points:

1) I never said that ground effect was a myth, I said that the "pressure bubble" was a myth! Ground effect is very real, and amounts to a typical 15% power savings for most helicopters (where the rotor cannot get closer to the ground that about .3 radius.

2) Those who love the pressure bubble theory are welcome to it, believing myths is not against the law! However, ask yourself why ground effect disappears when you hover over long grass - and don't tell me that grass absorbs pressure! The grass slows the outflow, which is the mechanism that changes the blade angle of attack and reduces the hover power.

3) The pressure bubble theory cannot explain why ground effect only reduces the induced drag of the blades, if that theory is correct, more velocity makes more pressure, and thus saves more power. If the air velocity gets banged against the ground, and pressure builds, then a higher velocity should make even more pressure, and more ground effect, right? No, wrong! Maximum ground effect is about +15% power, regardless of how fast the downwash velocity is. In fact, ground effect is no different for highly loaded rotors, with faster downwash, than it is for low disk loading rotors with gentle downwash.

4) If pressure bubbles push the aircraft up, then high speed airplanes, with the wake hitting the ground hundreds of meters behind the aircraft, should see no ground effect. But they do! That is because the effect is on the wing, where the angle of the flow around the wing is changed by the presence of the ground.

5) Ground effect makes the wings or blades act as if they are longer, and this cuts the tip losses that make the induced drag. They have nothing to do with the pressure under the blade or wing, they have everything to do with the reduction in outflow, and the reduction in the tip vortex pattern due to that outflow.

With my respect for Shawn unabated, I must respectfully disagree with him. There is a meaningful difference between the two cases, light vs heavy. But first we must clarify what we mean by Vortex Ring State (VRS) - and what is meant by a different problem called "Settling with Power (SWP)" or "over pitching" or "insufficient power to Hover OGE"
Most accidents where a hovering helicopter falls and crashes and VRS is blamed are actually cases of SWP or over pitching, where the hover performance is marginal, and insufficient reserve power (power margin) is available to allow moderate climbs and descents while OGE. The aircraft "falls through" the hover, hits hard (usually with just a bent helicopter and bruised ego) and then someone says "It was VRS." Sometimes the mistaken person is an official accident investigator!

In a helicopter at high MGW, with only slight or no margin between the power needed to HOGE and the power available from the engines, "over pitching" is more likely than in a lightly loaded helicopter where lots of power above hover power is available. When lightly loaded, there is much extra power available above the hover power, so the lightly loaded helo is much less likely to experience "over pitching" and thus the lightly loaded helo is much less likely to be mistakenly labeled as a VRS accident.

Now the truth: Since true VRS involves the descent of the helicopter into its own downwash, and since in a light helicopter the downwash velocity is quite a bit less than in that same helicopter when heavy, a lightly loaded helicopter needs much less rate of descent to experience true VRS.
Thus, heavy helicopters require more descent rate to get true VRS, and so are less likely to enter that state, but heavily loaded helicopters have more over pitching power control accidents that are too often labeled "VRS", so the mistaken pilot lore says heavy helicopters are more likely to experience VRS.

For the record, no helicopter can experience true VRS unless it is descending nearly vertically at about 800 to 1000 feet per minute.
Also for the record, most helicopters can experience SWP or overpitching at rates of descent near zero if they have little hover power margin.
Also, heavily loaded helicopters have less propensity to enter VRS because they need more vertical descent rate than lightly loaded helicopters, which need less descent rate to get into VRS.



Hmm,...are you sure these aren't "Rural Myths". I never heard them training in the city.


By the way, since you guys keep pointing this list out to me, is there any one particular "myth" you all think I'm perpetuating?

[[email protected]]

Robbiee - so when you learned about ground effect, no-one mentioned high pressure air or a bubble under the aircraft? No-one mentioned keeping RoD at slow speed under 300'/min to avoid VRS? No-one explained phase lad by calling it gyroscopic precession?

Sounds like you were trained by Nick and Shawn themselves.......

[Robbiee]

Robbiee - so when you learned about ground effect, no-one mentioned high pressure air or a bubble under the aircraft? No-one mentioned keeping RoD at slow speed under 300'/min to avoid VRS? No-one explained phase lad by calling it gyroscopic precession?

Sounds like you were trained by Nick and Shawn themselves.......

Ground effect was about the vorticies being restricted (and thus smaller) at less than rotor height above the ground.

ROD being less than 300 fpm with airspeed less than ETL was about not getting into the onset of VRS, not necessarily full blown VRS.

As for gyroscopic precession? No one said the rotor was a gyro, just that it acted similarly to one.

Anyway, none of these read like those "myths" above, and none of them have anything to do with any of my comments on this thread. Which is why I'm puzzled as to why I keep getting referred to them?

​​​​​​

[Ascend Charlie]

Robbiee, you must have learned somewhere other than the Hew Hess Hay - someplace where instructors have over 100 hours more than their students, and where the horsefeathers aren't passed from one under-informed pilot to the next. Well done!

Some people still think that "flapping to equality" is happening in forward flight, and that even though the disk is tilted down at the front, "the advancing blade is still flapping up."

[Robbiee]

Robbiee, you must have learned somewhere other than the Hew Hess Hay - someplace where instructors have over 100 hours more than their students, and where the horsefeathers aren't passed from one under-informed pilot to the next. Well done!

Some people still think that "flapping to equality" is happening in forward flight, and that even though the disk is tilted down at the front, "the advancing blade is still flapping up."

Yeah, that's dynamite.

Still doesn't explain the relevance of this so-called "myths" list to anything I've said about this thread topic, or why I've been referred to it twice?

[[email protected]]

The disc can't flap to equality when the cyclic position prevents it from doing so. Doesn't mean it isn't trying to.

[fdr]

@helispotter: I very much doubt, that a model helicopter would be appropriate for this kind of test. The problem does not lie in the mass and engine response, but in the dynamics of the main rotor. Building a scaled down model of the rotor with all the correct flexing and flapping isn't as easy as it sounds. The commercially available models lack a lot of components of a real rotor. No flapping- or lead/lag hinges for example. Not even virtual hinges in the blade root. Model helicopters do not need that. And then there is the Reynolds number.
But it has been done to visualise VRS in wind tunnels. But here they want to fly certain manoeuvres and that is difficult in a wind tunnel.
The budget isn't very high. I think for that money it is cheaper to use a real helicopter.

Interesting. quick thorts:

For evaluating VRS, please note that vortex structures and their development are essentially independent of Reynolds Number, which is not obvious, but happens to be the case. Lots of good experimentation out there covering that topic, go to AIAA ARC (expensive) or NASA NTRS (free).
For establishing the effects of VRS, the type of rotor head involved is only of relevance to moments transferred to the mast and then to the body suspended from the mast, it doesn't affect the flow through the rotor itself.
Blade bending and torsion modes don't affect VRS. VRS may excite some high order bending modes, but they would be very low amplitude, there being unsteady inflow conditions to midspan to near full span rotor inflow, which will give more unsteady CL, CD and CM moments, but they are normally unsteady anyway.
Flapping itself doesn't affect VRS, but VRS will affect flapping, more on rotors withy zero hinge moments, and will affect roll/pitch moments directly on rotors with hinge offset.
in plane load relief is not particularly affected by VRS, lead-lag is not of great interest in modelling VRS.
The Lock number is pretty easy to emulate for a series of blades.

[fdr]

Robbiee, you must have learned somewhere other than the Hew Hess Hay - someplace where instructors have over 100 hours more than their students, and where the horsefeathers aren't passed from one under-informed pilot to the next. Well done!

Some people still think that "flapping to equality" is happening in forward flight, and that even though the disk is tilted down at the front, "the advancing blade is still flapping up."

Hmmm.

We may be speaking different dialects of English, but here is the equation of motion of flapping in forward flight, [eq:6.130 of reference]

https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/1210x182/screen_shot_2023_05_22_at_10_27_04_am_b5ccf625362a0a43fc73f2 bb08402a00eb8b376e.png

The aerodynamic coefficients are the flap moments due to angle-of-attack changes produced by the blade pitch, twist, inflow, flapping velocity, and flapping displacements, respectively. A flapping velocity produces an angle-of-attack perturbation that changes the blade lift to oppose the motion; hence the blade has aerodynamic damping given by the coefficient MBetadot.

Johnson, Wayne. Rotorcraft Aeromechanics (Cambridge Aerospace Series, 36) . Cambridge University Press.

Now, remove flapping to equality and you need a ton of cyclic input to achieve a zero roll moment other than your desired roll command. Helo aerodynamics and the laws of motion, control derivatives etc are fun; there is a lot going on and most of it is non linear, but it has algebraic solutions to give an understanding of what is actually going on. For transition from steady state hover, there is a characteristic cyclic position to achieve a flight path, and that is able to be determined using all of the effects that occur in the process, and right in the middle of that all is the harmonic of flapping motion.

In what context are we telling people that "flapping to equality" (a passable descriptive term of harmonic flapping) doesn't occur in forward flight?

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/890x522/screen_shot_2023_05_22_at_10_57_08_am_8d861a11994b1e60a7009a 6302dc09049438a588.png

Beta is flapping
Theta is blade pitch
Zeta is lead/lag...
Psi is the azimuth position that is being considered.

And here is the Fourier series of the harmonic motion of a rotor, and that gives the flappy bit above which is occurring in forward flight.
https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/1096x268/screen_shot_2023_05_22_at_10_57_33_am_478fe0548d4da0573f943d 228835c4ed5ceae4fc.png
These harmonics don't suddenly stop as the rotor shaft, skids, fuel, engine, and bio mass starts to move forward, they explain the motion that results at all times.

Your comment confuses me, I can only refer to the equations of motion in our universe. :)

[fdr]

The disc can't flap to equality when the cyclic position prevents it from doing so. Doesn't mean it isn't trying to.

?

I know it is some time since many of us looked at the books, but.... the tip path plane is only partly directed by the cyclic, it is otherwise determined by the flapping resulting from translation of the rotor disk through the air. While flapping alters the TPP, it doesn't add significant rolling moments to the hub (it isn't perfectly isolated though, there are some relatively small consequences). The effect of flapping from the translation is to balance forces, and the cyclic adds an additional force that causes the TPP to alter, and where there is a hinge moment, to develop a roll or pitch moment to the body of the helo, and with zero hinge moment, for the motion of the disk to lead to a moment from the center of the disk to the CG of the helicopter, which then moves the body in lag to the disk.

The cyclic doesn't alter the flapping of the TPP resulting from translation, which is resulting in varying velocity of the advancing and retreating blades. The cyclic is additive to the flapping response, as is shown in the Fourier series that describes the TPP. theta sub 1c is lateral cyclic pitch angle, theta sub1s is longitudinal cyclic pitch angle, and theta subo is the collective pitch angle. beta gives the flapping... zeta is the in plane lead lag, gamma is the lock number (the relationship of aerodynamic to inertial response of the rotor blade).

There is a wealth of really good reading for helicopter drivers out there, stuff that actually tells it as it is, gives the equations of motion, derivatives etc, and which (for my money) is well worth the coin for any helo driver. I do fundamental aerodynamic flight testing in helicopters and jet aircraft, as well as prop planes, and the helicopter is the one that I take the most care over, by far; I respect the courage of young helicopter CFIs that go out and teach engine failure OGE to a zero time student in an R-22, they are braver than I am... knowing the maths is not necessary to fly a helo, but knowing the science (the equations) is worth the effort if you go and play on the periphery of the envelope. The beauty of the helicopter and the reason I love flying them is that they are brutally honest, they show what the pilot is doing instantaneously, more than a Pitts S1 does.

Suggested reading list:

Principles of Helicopter Aerodynamics J Gordon Leishman.
Helicopter Aerodynamics Vol 1, Vol 2, Vol 3 Ray Prouty
Helicopter Performance Stability & control Ray Prouty
Basic Helicopter Aerodynamics John Seddon & Simon Newman
Aerodynamics of the Helicopter, Alfred Gessow & Gary C Myers Jr
Helicopter Theory, Wayne Johnson
Rotorcraft Aeromechanics Wayne Johnson
Rotary-wing Aerodynamics W.Z. Stepniewski & C.N. Keys
Helicopter Flight dynamics Gareth Padfield
Practical Methods for Aircraft and Rotorcraft Flight Control Design: An Optimization-Based Approach, Mark B Tischler, Tom Berger, Christina M Ivler, M H Mansur, K.K. Cheung, J Y Song
Cyclic & Collective, Shawn Coyle
The Art and Science fo Flying Helicopters, Shawn Coyle
The Little Book of Autorotations, Shawn Coyle

....

and something written by the FAA.

Shawns work is easy reading and a good operational input. Rays stuff is also relatively easy to get into, and it is worth having in hard back, (I've worn out a couple of copies). Gessow and Myers dates back to 1952, and not much has changed, Ch 7 is worth reading there, and it is consistent with Prouty, Johnson Stepniewski & Keys, and Leishman. (I like Johnsons work, he looks at each state from various analysis and that gives a helpful overview). Gessow and Myers work is available as a PDF, and is still relevant but does use some nomenclature that has fallen from favour in later works, the physics remain the same.

[[email protected]]

A lovely dismissive series of post there FDR without actually adding anything to the thread other than a level of maths that most pilots really don't care about.

Test pilots don't usually talk in pilot language, they usually lecture in engineer degree maths-speak, but Nick and Shawn were different in that respect - maybe you could try that.

Should I tell a pilot who is trying to fly us into the ground to remember his Fourier transformations and flapping harmonics or just get him to pull back on the cyclic?

[fdr]

AC - most of those links don't work any more unfortunately.

I was lucky to find Nick Lappos and Shawn Coyle on these pages 25 years ago and have tried to pass on their wisdom where possible ever since.

Nick is alive and well, and occasionally to be found in the old country, Shawn finally hung up his helmet on 19 June 2021 after a really bad run of health issues, if it was fitted, it went U/S at some point in his fight. A shame.

[fdr]

A lovely dismissive series of post there FDR without actually adding anything to the thread other than a level of maths that most pilots really don't care about.

Test pilots don't usually talk in pilot language, they usually lecture in engineer degree maths-speak, but Nick and Shawn were different in that respect - maybe you could try that.

Should I tell a pilot who is trying to fly us into the ground to remember his Fourier transformations and flapping harmonics or just get him to pull back on the cyclic?

You are very welcome. :ok:

If something is being added that has a potential to impact the operation of some young driver, it should be supportable if represented as fact, otherwise it adds to the mass of uncontrolled anecdotal wisdom. You have more than enough operational experience to add to the knowledge base, people read your commentary, are you sure you are happy with the accuracy of your recent post:

The disc can't flap to equality when the cyclic position prevents it from doing so. Doesn't mean it isn't trying to.

as written does it not contradict the equations of motion of the rotor? The flapping motion of the rotor is independent of the cyclic input. It may be a language issue as to what is being described, so if you are able to describe how the statement works in practice you will find a receptive audience. :)

P.S.: I did a bit of proof reading of Shawn's work, so I do agree in your view in that area. Shawn was a kindly and capable guy to go fly with or spend time with. His passing in June 2021 was another loss to the industry.

[SASless]

I suppose colored pencils are akin to wax crayons and are basic visual aids for those not fully weaned from their use in the explanation of complex problems that require the understanding of higher forms of math in order to achieve more precise understanding of the principles governing helicopter aerodynamics.

Did the many exams inflicted upon our British fellows fail somehow to elicit a more detailed grasp of those principles than might be garnered from the results of delving into for's reading list?

I am of the thought the colored pencil brigade may have imposed unintended limits upon the desired outcome even allowing for the basic assumption their transfer of knowledge was satisfactory for practical purposes despite failing to arise to the level one might obtain elsewhere and by different methods and different instructors.

One thing for sure is those believers in the pencils do not care to be challenged or alas contradicted.

One thing I learned very early in my flying career was I can always learn something from others no matter who they are or how much experience they have.....even if the teaching point is only to never to do it the way they did.

The reading list offered by fdr points us to some very useful information although I am not sure the FAA would on my list of favorites.

I always found it useful to re-read the wonderful small Sikorsky Blue Booklet on Helicopter Aerodynamics as it was written in language that was easily understood.

[[email protected]]

FDR - the problem with people with your level of education and depth of knowledge is that you often see what is meant to be a simple statement as an affront to accuracy because it isn't supported by pages of proof.

If I had wanted to offer a cogent argument to ACs post with supporting evidence and referencing, I would have done so - but I didn't - this, as you know, has been (another) thread about VRS and SWP following yet another avoidable accident and the more off-topic the thread goes, the less value it is to those young drivers.

I have taught those young drivers for nearly 40 years in a variety of roles and never once have I been asked for mathematical proof for what I have demonstrated or explained because for 99.9% of the time it is irrelevant.

If my operational and instructional experience and credentials aren't enough for you then I apologise - I have never claimed to be an aerodynamicist nor a maths or engineering guru - I am just a fairly well trained and tested pilot and instructor who seems to have got the message across reasonably well in the past.

If you want to explain the subtleties of flapping here then please do so in language clear and unambiguous to me and those young drivers but it might be worth a new thread.

I am always very happy to be educated - I have read a number of those sources you quote and regularly refer to my Prouty and Gessow and Myers .

[[email protected]]

You never can resist a dig Sasless..........sad.

[Ascend Charlie]

In what context are we telling people that "flapping to equality" (a passable descriptive term of harmonic flapping) doesn't occur in forward flight?

FDR, my science degree with majors in physics and mathematics was 55 years ago, so you lost me with your way-too-deep equations.

My comment was that a lot of people think that the advancing blade is flapping up in forward flight and the retreating blade is flapping down , when in fact they are doing the exact opposite.

Regarding Shawn, I had a delightful lunch with him in LA back in 2003, and got a signed copy of his book as well. I found quite a few things that could have been clarified better, and lots of spelling and grammatical errors, and I sent him a list of the suggested amendments. But when the next edition came out, the same errors were there - perhaps he didn't like the critique, or maybe the 2nd edition was already in the hands of the printers, will never know. But a lovely guy.

[Hughes500]

AC think the problem is a lot to do with the exact English and exactly whatever one is talking about. Case in point the blade does flap down if one is in forward flight, but most will think about accelerating the helicopter then the disc is trying to flap back and hence the push forward on the cylic. I have found over the years a picture paints a thousand complicated words, as long as the driver knows what happens when he does x or y , it doesnt really matter the why's and where fore's

[Robbiee]

Well, since we're on this ride,...

If Dissymmetry of Lift is being eliminated through flapping (as my textbook tells me) then why does the R22 have a right trim knob which (I am told) is to alleviate the right cyclic pressure needed to counter, Dissymmetry of Lift? :ooh:

[SASless]

The Vertical Flight Society has a library of about 15,000 articles among which are many dealing with research studies re helicopter aerodynamics.

It would be interesting to see how many professional helicopter pilots are members of the VFS or other similar organizations that offer continuing education on topics relating to our profession.

One thing we should consider is the difference between the theoretical and the practical and find a consensus where that line should. be drawn when assessing what a licensed helicopter pilot should know.

As in other professions, actually in order to be considered a profession there should be a requirement for continuing education for its members.

Is there such a thing for helicopter pilots.....not training or testing....but education?

[Lonewolf_50]

I have taught those young drivers for nearly 40 years in a variety of roles and never once have I been asked for mathematical proof for what I have demonstrated or explained because for 99.9% of the time it is irrelevant. . Getting back to the topic of this thread, would you teach one of those young drivers to do a down wind landing (to a hover) in the manner shown in the example video?
(I'll bet two pints of Guinness that you would not!)
As interesting as this thread has been, in parts, some pilots a few pages back (to include yourself and Robbie) pointed to what appears to me to be a root cause:
Either a poor choice to try to land downwind, or, a poor technique in attempting to accomplish a downwind landing.

Which I think is the takeaway from this crash, if lessons are to be learned.

[SASless]

If one uses the reported winds as posted and the runway lay out for the landing location....and the only other reference is the short video with limited perspective and visual references to confirm the relativity of the wind to landing azimuth.....perhaps some of the discussion is misplaced.

Was was the cross wind component if any"

Perhaps the immediate take away might be would be that that commonly used phrase of "WTF" was he thinking (referring to the Pilot at the controls"?

It does seem an occasion for an old fashioned down wind approach with a polite turn back into wind at the bottom kind of situation that did not happen that way for some reason.

Was there a reason beyond just simply not doing it?

Is there anyone here that KNOWS what the pilot was thinking or KNOW. why he did what he did?

This discussion should have ended immediately upon the first mention of VRS or SWP and a new thread....perhaps we should see a Jet Blast like "SWP/VRS Hamster Wheel" thread starts for Rotorheads.

All in favor....say "Aye"....."Nay's" remain silent please!

[FH1100 Pilot]

With respect to SASless''s question about the mindset of the Astar pilot...

He came in from over the town; and that ripping tailwind probably had him doing a pretty good clip. How could a Commercial pilot (or any pilot for that matter) *not* realize that he had a big, stinking tailwind? It seems astonishing. So we know that wind direction was not in the forefront of his mind, as it should have been. If it had, he would've just extended out a bit and done a simple 180 to come back into the wind to get to his pad (see Google Maps view for orientation). So again, it's not important to know what he *was* thinking about - we know confidently what he was *not* thinking about. That's pretty obvious. No sane, awake, competent pilot would deliberately conduct such an approach. There doesn't seem to be any good, compelling reason for him to have done that (unless he had to pee, really, REALLY badly). And hey, it's harsh, but maybe that guy (gal?) was in the wrong line of work? Not all of us can be Chuck Yeager/Aaron, and I've met some really, um, "less than stellar" pilots in my day. You're lying if you say you haven't too.

Then, of course, after every one of these accidents, the discussion devolves into the old VRS/SWP argument. It's silly, because IT DOES NOT MATTER if it was one or the other. If you're making a downwind approach, whether you run out of engine power or rotor power, the end result is usually the same. If you're shallow, you might get away with an unplanned running landing and the resultant change of shorts. If you're steep: Boom. Soooooo, was this Astar accident the result of SWP or VRS? I say, "Who cares? It makes no difference."

[Nubian]

If one uses the reported winds as posted and the runway lay out for the landing location....and the only other reference is the short video with limited perspective and visual references to confirm the relativity of the wind to landing azimuth.....perhaps some of the discussion is misplaced.

Was was the cross wind component if any"

Perhaps the immediate take away might be would be that that commonly used phrase of "WTF" was he thinking (referring to the Pilot at the controls"?

It does seem an occasion for an old fashioned down wind approach with a polite turn back into wind at the bottom kind of situation that did not happen that way for some reason.

Was there a reason beyond just simply not doing it?

Is there anyone here that KNOWS what the pilot was thinking or KNOW. why he did what he did?

This discussion should have ended immediately upon the first mention of VRS or SWP and a new thread....perhaps we should see a Jet Blast like "SWP/VRS Hamster Wheel" thread starts for Rotorheads.

All in favor....say "Aye"....."Nay's" remain silent please!


“Aye”!


Although I have said to use ASN with care earlier, some of the info could explain the decision of the pilot. Maybe a long day out?! At least the pilot has probably given as much information as needed for TC to do their investigation.

The updated info of this crash is saying:

” Range Helicopters Inc Eurocopter AS 350B2 Ecureuil, was returning to the Edson Airport (YET/CYET), Alberta, from a staging area supporting firefighting operations to the east of Edson, AB.
On approach to CYET the pilot elected to expedite his arrival routing due to incoming fixed wing air traffic. On the final approach to landing, the helicopter entered a descent that resulted in a hard landing and roll-over”

[[email protected]]

LW 50 - in answer to your question, yes I would and have taught lots of pilots to make a downwind approach in those conditions BUT NOT in the manner he did it.

Being able to conduct a safe downwind approach is a basic pilot skill because sometimes it is the only way in (terrain, obstacles, tactics etc etc).

Never ever taught it as a limited power exercise and always with an emphasis on keeping the RoD and closure speed nicely under control. Once in the hover turn into wind and land. At any stage if you are not happy with RoD/closure speed or power requirement GO AROUND early.

Plenty of other options, some I mentioned before - a downwind approach maintaining ETL with a co-ordinated yaw/roll/pitch turn through 180 when abeam the LS (more advanced but not rocket science) or simply a curving, descent to end up into wind facing the spot.

You can expedite the crossing of the airfield/runway without ending up in a heap at the end. I would call it a downwind flare and turn quickstop.

Not much value to those who need the info and knowledge in relegating the discussion to jetblast just because some are bored with it. I don't mind repeating myself if some of it eventually goes in and prevents another pilot making the same dumb mistakes.

So NAY.

[Chock Puller]

Crab It appears you overlooked what was said.

Yes.a typo where "starts" appears for "started"

I bolded the one word just to draw your attention to that word....as it was not in bold in the original post.

This discussion should have ended immediately upon the first mention of VRS or SWP and a new thread....perhaps we should see a Jet Blast like "SWP/VRS Hamster Wheel" thread starts for Rotorheads.

[T28B]

Presented as a Mod/Admin:
I am of mixed thinking on the suggestion about a bundling of the VRS discussions, since I'd not like to see a "JB" style penetrate the hallowed halls of Rotorheads.
One JB is enough, thank you. :p

Perhaps a VRS sticky thread at the top with links to the salient threads?
What do you all think of that, dear colleagues of Rotorheads?
This is in many ways your pub, your crew room, so I'd like to know what you all think.

[megan]

Not all of us can be Chuck YeagerAnd thank God for that, his NF-104 crash illustrated all his failings, main one being arrogance and unwillingness to accept training from an individual of subordinate rank. Also his attempt to make Neil Armstrong look a fool at Edwards.

[[email protected]]

Chock puller and T28B - if you mix down all the VRS/SWP threads into one hamster wheel then the analysis of individual incidents like the Edson one will disappear and everyone will just say 'oh no here we go again'.

The fact that the confusion between the two still exists is the main reason to keep debating it and reinforcing the difference.

If I was in my 'pub' and someone was confused about the difference, I would try to educate them not push them to another room to be ignored.

[Robbiee]

The fact that the confusion between the two still exists is the main reason to keep debating it and reinforcing the difference.



There was never really a confusion over the two terms, only the refusal by some to accept that different cultures use the same words to describe different things.

[helispotter]

...here is a gathering of Nick Lappos's Urban Myths, plus some notes from the late Shawn Coyle, both these gents being highly qualified test pilots:Helicopter Urban Myths
These Urban Myths pervade our understanding of helicopters and how they operate. Each is fundamentally incorrect, but most are generally held as gospel, because training, lore and reference documents have repeated them long enough that they are simply accepted.
...
5) Winds affect the power we require when we are in forward flight...


At the risk of further "thread drift" from the original accident, I wanted to challenge this specific supposed 'myth'.

What was the original claim? Was it comparing identical helicopters achieving the same speed over the ground, one in still air, the others in a headwind or tailwind? Or was it comparing helicopters all achieving the same airspeed even if their ground speeds all differ? If the former, this wouldn't be a myth. If the latter, I would agree the statement is a myth. To elaborate for the case of constant ground speed:

* Helicopter A flying in still air at 110 knots ground speed hence airspeed also 110 knots. Resistance roughly proportional to velocity squared, so call this 100% resistance case.

* Helicopter B flying at 110 knots ground speed into 20 knot headwind, so airspeed 130 knots. Its resistance will be ~140% of Helicopter A.

* Helicopter C flying at 110 knots ground speed with 20 knot tailwind, so airspeed 90 knots. Its resistance will be ~67% of Helicopter A.

Power required from engine will be related to the combination of generating lift to support the helicopter and rotor thrust to overcome its resistance, so certainly changes. The differences in power demand are more stark the slower the helicopter ground speed and the higher the wind speed.

If I am wrong here, I would obviously like to be corrected.

I can't see an ideal solution for managing where discussions on SWP / VRS / LTE etc, etc, turn up. But I am learning regardless of which thread such exchanges appear in.

[FH1100 Pilot]

And thank God for that, his NF-104 crash illustrated all his failings, main one being arrogance and unwillingness to accept training from an individual of subordinate rank. Also his attempt to make Neil Armstrong look a fool at Edwards.
Oh Megan... Missy, you may be too young to know the importance and history of the brave aviators who came before you, and I don't really fault you for that. The "innocent hubris of youth" and all. And I know that it's fashionable these days for you gals to denigrate and devalue all men in general, especially the ballsy, hyper-masculine test-pilots who blazed the trails for the rest of us. But despite all of his purported "failings" as you call them, I don't think that there's any question or doubt that General Yeager was a superlative pilot...one that we all can try to emulate. The Astar driver who is the subject of this here thread? Not so much.

[[email protected]]

There was never really a confusion over the two terms, only the refusal by some to accept that different cultures use the same words to describe different things.

That was exactly the cause of the confusion. And the refusal of some to acknowledge that VRS and SWP are different.

In answer to your question about the R22 lateral trim - I believe it is to help with Inflow Roll (roll towards the advancing side) - usually perceived as being purely a low speed phenomenon but present in smaller measure throughout forward flight. The airflow entering the front of the disc has a different inflow angle to the air entering the rear of the disc (more time travelling across the disc to be affected by it) creating an inequality of lift between front and rear and resulting in a right roll tendency.

[Robbiee]

That was exactly the cause of the confusion. And the refusal of some to acknowledge that VRS and SWP are different.

In answer to your question about the R22 lateral trim - I believe it is to help with Inflow Roll (roll towards the advancing side) - usually perceived as being purely a low speed phenomenon but present in smaller measure throughout forward flight. The airflow entering the front of the disc has a different inflow angle to the air entering the rear of the disc (more time travelling across the disc to be affected by it) creating an inequality of lift between front and rear and resulting in a right roll tendency.

I'm not going to get into that argument again. I'll only say that it seems rather stubborn to hold onto a term that clearly has multiple definitions of which no one can agree on which is the "one true definition". Which is why I am with the FAA and Robinson in that I simply no longer use the term anymore.

So, if you have a hard landing despite still having a fully functional running engine, it is because,...
1) You entered VRS
2) You came in hot and waited too long to put on the breaks
3) You're too heavy to do what you are trying to do
4) You're in a tailwind and simply using the wrong technique
5) You are overpitching

As for the rt trim nob? Its to alleviate right cyclic pressure countering a left roll tendency. What you are describing is Transverse Flow Effect. Besides, the rt trim knob is used primarily in cruise, not low speed flight.