Wycombe air park - accident

[AfricanEagle]

Not much left of a 610m runway once airborne if you decide to abort.

I occasionaly fly a Lance 1, most times heavy and hot, and I personally, with current experience on aircraft, will only take off with at least 1000m.

[Final 3 Greens]

I wonder if raising the gear immediately after lift-off would have taken him out of the back-of-the-drag-curve pickle. On the other hand, you wouldn't rush to blow your chances of a safe landing on the remaining runway, in case you decide to abort. Tricky one, I suppose.

I don't know this particular model, but sometimes gear in transit is draggier than gear down.

One conventional tail singles, you may also encounter a marked pitch change -not great , although on the T tail arrow, I don't seem to remember one, so the T tail Lance may not suffer from this.

[A and C]

I will chuck this in for the forum to consider on the understanding that it is pure speculation.

The pilot lines up on the runway knowing that he is at or near MTOW having done the W&B calculation. He is keen to get the aircraft into the air ASAP and so rotates the aircraft on the basis of a rapidly approaching runway end rather that by using the airspeed as his marker for rotation, the aircraft gets into the air only due to ground effect, it cant accelerate due to the high AoA and it wont for the same reason climb out of ground effect.

The aircraft is now in a state were it cant fly more than a few feet above the ground and has not enough room to stop on the airfield.

My final request is for someone with access to the flight manual for this aircraft to publish a take off performance calculation for the aircraft at MTOW using the conditions for the day.

[IO540]

I think there are two ways to look at this "ground effect" stuff, and it is connected with the "soft field" takeoff procedure.

In the SF procedure, you haul the plane off the runway ASAP, using a lot of elevator pull, which is draggy, but it gets it out of the muck ASAP and a) reduces the risk of landing gear damage from bumps encountered at high speed and b) enables the plane to continue accelerating because flight in ground effect is very efficient. If you did not do this, the plane might only reach a "terminal velocity" which, due to the landing gear drag on the ground, is below rotation speed.

However, the total takeoff run in the SF procedure is (in probably all cases) no shorter than in a conventional departure from a hard surface. This is due to the slow initial acceleration, and the large amount of elevator drag needed early on.

On the other hand, once you get the plane into ground effect and hold it in ground effect, by quite a lot of, and an increasing amount of as the speed builds up, push on the elevator, you get very rapid acceleration.

I think that most of the cases where somebody does

it cant accelerate due to the high AoA and it wont for the same reason climb out of ground effect.

it is because they failed to keep the plane low down, have allowed it to climb to a height where the ground effect only just supports it (and a plane will climb to this height naturally, which is why you have to push it back "down" during a proper SF takeoff) and in this state it will indeed never accelerate because it just hangs there on the back of the curve.

I don't think many flight manuals give any figures for SF takeoff performance, and it is very variable anyway.

The most astounding example of ground effect acceleration I have seen was in a Jetprop, where the expert pilot kept it a few feet above the runway (on a low pass) and held it there up to about 170kt, and the resulting zoom climb was spectacular in reaching ~ 1000ft in just a few seconds.

[Conventional Gear]

it is because they failed to keep the plane low down, have allowed it to climb to a height where the ground effect only just supports it (and a plane will climb to this height naturally, which is why you have to push it back "down" during a proper SF takeoff) and in this state it will indeed never accelerate because it just hangs there on the back of the curve.

Rather than thinking in terms of 'ground effect only just supports it', consider what ground effect actually does. It reduces drag by a significant amount. Climbing out of it produces an increase in drag.

The scenario then becomes one of an aircraft at high aoa, no excess power, already on the back of the drag curve and decelerating because of the increased drag experienced when transitioning from ground effect. We all know to fly slower on the back of the drag curve and maintain height needs more power - as none is available the result is a predictable loss of lift.

Not only now do we have an aircraft that cannot accelerate and climb, we now have one that cannot maintain airspeed or lift.

I think it would be difficult to 'escape' ground effect in this condition, I don't know if anyone knows what height the aircraft reached, but I suspect it never really got out of ground effect at all.

[IO540]

Rather than thinking in terms of 'ground effect only just supports it', consider what ground effect actually does. It reduces drag by a significant amount. Climbing out of it produces an increase in drag.

I agree but I would put it the other way round i.e. ground effect provides "support" for the vortex being shed behind the wing and thus reduces the AOA required for a specific speed and weight (and configuration, if applicable), and a lower AOA means less drag.

Climbing out of ground effect means a higher AOA is required to continue flight, but if you got enough speed while in it, the climb will be rapid.

[Conventional Gear]

I agree but I would put it the other way round i.e. ground effect reduces the AOA required for a specific speed and weight (and configuration, if applicable), and a lower AOA means less drag.

Yep, but that requires the pilot to hold the required lower aoa - I guess the question then becomes did this pilot do that?

I've done soft field take-offs and even as a newbie taildragger pilot who almost has their head around pushing the stick forward in the take-off run, doing it just above the ground takes a real 'I've just got to do this' effort and it doesn't come all that easily.

Of course it is conjecture, for all we know the pilot experienced power failure or reduced power, that's for the AAIB.

What I'm taking from this is if I plan a take-off at near the loading and performance limits - I'm going to be very sure to question my currency on the aircraft and piloting techniques.

I think if one didn't 'plan' to take-off and accelerate in ground effect, it would be very difficult to figure it out in a wallowing plane which doesn't want to fly.

[IO540]

I've done soft field take-offs and even as a newbie taildragger pilot who almost has their head around pushing the stick forward in the take-off run, doing it just above the ground takes a real 'I've just got to do this' effort and it doesn't come all that easily.

Yes; it is quite counter-intuitive. But the acceleration is rapid.

Oddly enough this was never taught in my UK PPL, but the Americans love examining soft field and short field takeoffs.

I don't know anything about the accident aircraft so can't comment on the accident, but most light "6 seaters" have pretty severe tradeoffs on the W&B characteristics. And a real 5/6-person (UK sized person!) hauler is some tank like an Aztec.

[Brooklands]

Not much left of a 610m runway once airborne if you decide to abort.

The Hard runway at Wycombe (which is what the aircraft was using is) is 735m long. I'll agree that it doesn't give you much more to stop in if everything goes wrong. Also the aircraft went through the hedge off to one side, and before the end of the hard runway. Having seen the pictures I'll agree they were very luck to walk way.

Brooklands

[bingofuel]

I will not speculate on what happened regarding this incident, and I do not know what the required TODR was for this aircraft in the conditions, but will comment that if someone attempts to take off from a runway where it is only possible to attain a safe departure by using perfect flying technique, or attempting to accelerate to a suitable climb speed in ground effect, prior to attempting to climb to avoid colliding with an object on departure, then the take of distance available is inadequate, or no safety margin has been applied to the performance figures.

Sadly performance planning does not seem to feature highly in the ppl training system.

[englishal]

It was certainly too heavy to fly at the speed it lifted off...so either it was too slow to fly at the speed it lifted off (i.e. unexpected rotate - GofG or trim out, pilot SNAFU, or loss / lack of engine power), or it was too heavy to fly at the book speeds and was on the back of the drag curve and would be difficult or impossible to climb away.

[smarthawke]

"Sadly performance planning does not seem to feature highly in the ppl training system."

No doubt the comment was a general one and wasn't aimed at the incident in question as I don't think anyone confirmed if the incident pilot was a PPL or CPL.

[bingofuel]

No doubt the comment was a general one

Indeed it was, as I said I am making no specific comment on the incident, more a general opinion on how some pilots (regardless of licence held) are perhaps a little blase when operating some aeroplanes.
I am not referring to the pilot in this case, let us wait for the AAIB findings.

[proudprivate]

Short field take offs and soft field take offs are not in the JAA PTS

I just checked...

Oddly enough this was never taught in my UK PPL, but the Americans love examining soft field and short field takeoffs.

I concur. From personal experience : nothing of that on my JAA checkride (short field landing yes, but not take-off); Tested extensively on my FAA checkride.

But hey, its only a practical safety matter. Since when did that become an issue ? As long as you know your inner ear anatomy.

Sadly performance planning does not seem to feature highly in the ppl training system

You can earn €11 by turning it into a multiple choice question and sending it to the French DGAC.

[BEagle]

There is an entire PPL theoretical knolwedge examination in the UK, entitled Flight Performance and Planning!!

On the PPL Skill Test, I always required the applicant to complete a mass and balance calculation and take-off performance calculation for the aircraft used for the test and the weather conditions of the day. So I dispute any allegation that flight performance and planning is an afterthought for the JAR-FCL PPL(A)!

[Conventional Gear]

The issue is more habit.

For 99% of flights during the PPL I filled the Warrior to tabs, knowing that with fuel to tabs, instructor and me it would fly and have enough runway at the training field.

We all do the calculations for the test I'm sure.

The trouble comes when one then takes 2 friends, fills it to tabs and realises one is on the porky side.

It still flies and so on, until the day when it is hot, the friends become 3 friends we decide to fill it full for the trip so we don't have to refuel.

It's just an honest opinion of the mechanism behind some of these type of accidents and what I generally see. If one isn't flying a type often there is so much to remember that one can skip the most vital step, checking it will fly and give the performance necessary. I wonder how much of this actually relates to the fact that many spam cans have been designed to be easy to fly but also easy to overload.

I keep a few printed off balance sheets in my flight bag with the fixed figures pre-calculated. I also carry a small ASA book which gives an idiot's guide to the performance calculations. I'll be honest though that the last time I actually did them, eer was for a renewal test.

Makes me realise I need to change my habits.

[gasax]

I think there is a real lack of appreciation of perfromance planning for ppls. There is a short amount of w&b and take-off and landing distances. But practical experience of it? Virtually none.

The differences in real world performance between a light pa28 and one loaded to the gills is very different. New ppls will have no experience of these effects - they learn them (or not) when they start to fly aircraft with greater payloads or perforamnce differences.

My own 'conversions to C172/182/180 pa28 etc all included some chat about w&b but no flying at max weight.

The largest single difference in an aircraft's performance is caused by its weight. All of which is very topical as last weekend we took a visiting pilot to one side nad asked some pointed questions about the number of people and things he was piling into a C172 at our pretty short and difficult strip. He was adamant he could do it, checked the numbers and lifted about 150 odd metres before the end of the strip.......

[IO540]

The problem with grass is that it is highly variable.

My takeoff run is ~ 350m (MTOW) but I have seen up to ~ 800m on grass ~ 8" tall, with rough ground underneath, and I was flying alone on that occassion.

Short dry grass is about 600m, short wet grass maybe 800m.

These figures are not in the POH.

Also, a lot of planes are knackered.

[proudprivate]

On the PPL Skill Test, I always required the applicant to complete a mass and balance calculation and take-off performance calculation for the aircraft used for the test and the weather conditions of the day.

That is good for you. The fact of the matter remains that the practical test standards do not contain it;

Also, the lack of a thorough oral examination restricts the possibilities for well-meaning and true safety standards adhering JAA examiners (like yourself).

On my PPL-checkride, while doing the engine run-up, my examiner asked me : "So what is our ground roll under the current circumstances". When I replied "We're near Max Gross, Sea Level, 25° OAT, this is going to be about 900 feet", he told me "Ok, show me the takeoff as if this were 2000 feet grass".

That is what I would call emphasis on performance from the very beginning.

In all fairness, as we progress to Multi-Engine the differences between JAA and FAA in aircraft performance issues (accelerate-stop and accelerate-go etc...) become less outspoken.

But I'm convinced that the relatively high number of performance related accidents in Europe can be reduced by making it a special emphasis item on the PPL checkride. Not in order to flunk candidates who foul up, but to make candidates learn of its importance and to save lives while doing it.

So I dispute any allegation that flight performance and planning is an afterthought for the JAR-FCL PPL(A)!

Obviously the inner ear anatomy quote was meant to be inflammatory. However, the excessive emphasis on non-safety related theory in Europe inevitably degrades the attention that should be dedicated to things that matter. That is (admittedly just) one of the reasons why FAA-PPLs per flown hour are safer than JAA-PPLs.

We all do the calculations for the test I'm sure.

The trouble comes when one then takes 2 friends, fills it to tabs and realises one is on the porky side.

It still flies and so on, until the day when it is hot, the friends become 3 friends we decide to fill it full for the trip so we don't have to refuel.

Never ! Not say that you or anyone on this forum does this, but with over 95% of all accidents due to pilot error, this accident chain of events is simply inexcusable.

The surprise should come when you do your first W&B calculation for 4 people in a 4 seater and realise that the manufacturers of PA-28's, AA5A's, C172's are actually cheating when putting 4 seats in it.

So we do our calculations for each combination of passengers and see what would work and what not.
(2 adults + 2 kids, 3 adults, 2 adults and a fat guy, etc... + potential luggage, bikes, etc...)
And we don't take off unless the numbers add up. Otherwise, why bother paying insurance ?

[Sillert,V.I.]

Originally Posted by IO540

Also, a lot of planes are knackered.

That, I suspect, is often the last hole in the swiss cheese.

A long while ago, and shortly after getting my PPL, I flew a couple of friends to a gliding site in an ancient cherokee 140. Foolishly I then let a third friend join us for the short trip back to base & took off without a W&B check. Can't remember the fuel state but I'm betting we were well overloaded. I remember it took most of the 1200m tarmac to get airborne & ROC was around 200'/min. I mentioned on returning that the engine seemed down on power & was told the following week that following an inspection it was indeed not giving all that it should and that the aircraft had been withdrawn from service pending overhaul.

Only the runway length saved a nasty incident and I learned a valuable lesson that day.