Singles v. Twins
Guest
Posts: n/a
There are significant differences to fixed wing experience. Firstly asymmetric thrust is probably a big factor in fixed wing engine failure accidents and secondly I suspect pilot experience and competency is generally much greater in heli twins, due to the cost of flying them and fewer low time PPLs etc.
Nevertheless pilot training must be very important as shutting down the wrong engine is still a risk with both. At least a pilot has substantial control over his competence, whereas he has little control over whether his engine will fail ...
Nevertheless pilot training must be very important as shutting down the wrong engine is still a risk with both. At least a pilot has substantial control over his competence, whereas he has little control over whether his engine will fail ...
Guest
Posts: n/a
Singles are fine for poodlin' about in IF you're obeying the law!
I fly twins Police. Too many times I see singles down at my height limits (900' below non-police civilian machines!)
If you fly where you can't auturotate clear (over a city!) you're playing with other peoples lives. It's irresponsible & unproffesional.
My one remaining engine may 'only get me to the crash' but at least it'll be an area of my choosing & not the high street!
The law says...THOU SHALT NOT ENDANGER A THIRD PARTY.
As for which are better, I've got to agree with others...there is no correct answer. It depends what you're using it for.
signed....militant mini!
I fly twins Police. Too many times I see singles down at my height limits (900' below non-police civilian machines!)
If you fly where you can't auturotate clear (over a city!) you're playing with other peoples lives. It's irresponsible & unproffesional.
My one remaining engine may 'only get me to the crash' but at least it'll be an area of my choosing & not the high street!
The law says...THOU SHALT NOT ENDANGER A THIRD PARTY.
As for which are better, I've got to agree with others...there is no correct answer. It depends what you're using it for.
signed....militant mini!
Guest
Posts: n/a
Slightly tangential, but I wonder if its really necessary to adhere to UK twin-engine requirements when operating air ambulances over remote areas like Northumberland and Devon & Cornwall. These machines are funded via the raffle ticket and jumble sale method; is it sensible to impose significant extra cost for an arguable statistical benefit?
------------------
"Fair is foul, foul is fair,
Hover through the fog and filthy air..." Macbeth, Act 1 Scene 1
------------------
"Fair is foul, foul is fair,
Hover through the fog and filthy air..." Macbeth, Act 1 Scene 1
Guest
Posts: n/a
Don't the helo's in these areas land in built up areas then? Don't they fly at night? Isn't flight at night IFR in the UK? Doesn't this all add up to 2 engines?
Anyway the Devon air ambulance needs a lot more than another engine after its latest outing
------------------
Thermal runaway.
Anyway the Devon air ambulance needs a lot more than another engine after its latest outing
------------------
Thermal runaway.
Guest
Posts: n/a
Dear Mr not so natural type person.
With relation to your point on twins being an extra burden on Ambulance resources etc. Yes they are....BUT Flight Safety surely has to take precedence over economics!?
Single engine in rural ares....donk stops....forced landing on the side of a hill....splat....ooops....roll....crash....etc.
At least with two he's got a chance of finding a nice place, that's if he can't make it to a nice airfield. Not to mention some valid points from Mr TC.
Your point is not ignored however. I feel further government/ insurance company funding must be found to enable these yellow perils to continue ops!!
With relation to your point on twins being an extra burden on Ambulance resources etc. Yes they are....BUT Flight Safety surely has to take precedence over economics!?
Single engine in rural ares....donk stops....forced landing on the side of a hill....splat....ooops....roll....crash....etc.
At least with two he's got a chance of finding a nice place, that's if he can't make it to a nice airfield. Not to mention some valid points from Mr TC.
Your point is not ignored however. I feel further government/ insurance company funding must be found to enable these yellow perils to continue ops!!
Guest
Posts: n/a
There's another thread running on single vs twin safety, perhaps this topic belongs there. But without wishing to upset anybody, I think that the statistical risk of an engine failure may not be high enough to justify asking the charity collectors, week in, week out, to raise so much extra money. Yes, they operate in built-up areas in D&C and Northumberland, but not many. Has anyone done any genuine comparisons between like for like twin/single accidents (ie exclusive of non-engine failure)?
------------------
"Fair is foul, foul is fair,
Hover through the fog and filthy air..." Macbeth, Act 1 Scene 1
------------------
"Fair is foul, foul is fair,
Hover through the fog and filthy air..." Macbeth, Act 1 Scene 1
singles v. twins
Yes, yes, we know that conventional twin-engine helicopters still have only one tail rotor and one main transmission and all that rot. But the weak link is still the engine, let's face it. We can kid ourselves that modern turbine powerplants are as reliable as Big Ben, but the fact is that they're still a variable and they still sometimes go boom when you least expect it.
At the same time, a properly maintained t/r gearbox or main transmission will confidently go to TBO. That a t/r or m/r blade might just go flying off into space is not something even worth worrying about.
As evidence of the new shift of thinking about the relative "safety" of single-engine designs, someone mentioned previously about how the Pilatus PC-12 and Cessna Caravan are becoming more popular as "airliners." Yes, well...*maybe* Day/VFR-only but certainly not overwater. Then, perusing the FAA database today, I saw this tidbit:
.
Of course, we don't know the nature of the engine failure. Was it a catastrophic failure? ...Pilot induced? We'll undoubtedly find out in time.
Some pilots desperately like to think that engines are "reliable enough" to be safe when used singularly. It is a philosophy to which I do not personally subscribe.
At the same time, a properly maintained t/r gearbox or main transmission will confidently go to TBO. That a t/r or m/r blade might just go flying off into space is not something even worth worrying about.
As evidence of the new shift of thinking about the relative "safety" of single-engine designs, someone mentioned previously about how the Pilatus PC-12 and Cessna Caravan are becoming more popular as "airliners." Yes, well...*maybe* Day/VFR-only but certainly not overwater. Then, perusing the FAA database today, I saw this tidbit:
IDENTIFICATION Regis#: 96WF Make/Model: PC12 Description: PC-12/45, PILATUS Date: 10/16/2002 Time: 1825 Event Type: Accident Highest Injury: Minor Mid Air: N Missing: N Damage: Substantial
LOCATION City: TRENTON State: NJ Country: US
DESCRIPTION: ACFT CRASHED SHORTLY AFTER TAKE-OFF FROM RWY 6, DECLARED AN INFLIGHT EMERGENCY DUE TO ENGINE FAILURE, LANDED HARD AND SLID OFF END OF RWY 16, 2 PILOTS AND 4 PASSENGERS ON BOARD, ONE PASSENGER SUFFERED A MINOR INJURY, TRENTON, NJ
LOCATION City: TRENTON State: NJ Country: US
DESCRIPTION: ACFT CRASHED SHORTLY AFTER TAKE-OFF FROM RWY 6, DECLARED AN INFLIGHT EMERGENCY DUE TO ENGINE FAILURE, LANDED HARD AND SLID OFF END OF RWY 16, 2 PILOTS AND 4 PASSENGERS ON BOARD, ONE PASSENGER SUFFERED A MINOR INJURY, TRENTON, NJ
Of course, we don't know the nature of the engine failure. Was it a catastrophic failure? ...Pilot induced? We'll undoubtedly find out in time.
Some pilots desperately like to think that engines are "reliable enough" to be safe when used singularly. It is a philosophy to which I do not personally subscribe.
In the same light....we can read about an American Airlines three engine aircraft losing an engine (literally) on takeoff at Chicago and crashing. El Al had a 747 lose an engine and crash after takeoff. The only real difference is following an engine failure in a single....there is going to be a forced landing that may very well result in a crash. Make the scenario of one of IFR at night with obscured terrain.....and the thought of putting one down in an emergency chills my heart. I came to that very conclusion one night in a Cessna Caravan over the Northern Cascade mountains between Wenatchee, Washington and Seattle. I realized I would certainly die if the engine failed. You can argue statistics till the cows come home....but reality is the single engine aircraft puts crew and passengers at mortal risk under many situations whereas the multi-engine aircraft does not. Multi's have their own ways of killing you.....but the odds get much better.
OK, I'll debate you on this topic.
What is the source of the information regarding the engine being the limiting component in helicopter safety?
Same info for transmissions and drivetrains?
Info for main and tail rotor blade failures?
Without statistical data, these are very difficult to quantify, but this seems to be somewhat subjective conclusion.
I would consider that the failure of any of the items you specifically mention might be a significant contribution to the accident record, and a little research might prove the same to be true.
What is a more likely cause of an accident, a failure of the helicopter and systems, or the actions of the crew?
What is the source of the information regarding the engine being the limiting component in helicopter safety?
Same info for transmissions and drivetrains?
Info for main and tail rotor blade failures?
Without statistical data, these are very difficult to quantify, but this seems to be somewhat subjective conclusion.
I would consider that the failure of any of the items you specifically mention might be a significant contribution to the accident record, and a little research might prove the same to be true.
What is a more likely cause of an accident, a failure of the helicopter and systems, or the actions of the crew?
Thomas coupling wrote:
What a pithy and perfectly useless post. Thanks for adding...um...nothing to the thread. Then again, I shouldn't have expected anything else from you. I guess next time we should all run our post topics through TC to see whether they're judged "worthy" or not.
I'm going for a leak, and when I come back, this topic will have ended
What a pithy and perfectly useless post. Thanks for adding...um...nothing to the thread. Then again, I shouldn't have expected anything else from you. I guess next time we should all run our post topics through TC to see whether they're judged "worthy" or not.
Now easy Prune Fan......we all find satisfaction in our individual ways. If TC can achieve that in the loo....all by himself...then we should afford him that outlet. I assume what he meant was ......that as his visits to such places take lenghty periods of time ...he merely wanted to report to us that he would not be able to participate in a meaningful manner as a result of his need to see a man about a dog, and thus we would have discussed this issues to their logical conclusions before he completed his research. He no doubt does his research while engaged in his activities there , and probably draws from such august tomes as the Readers Digest. I rest assured he will be better informed and in a much more ready frame of mind upon his return and shall provide his so deeply thought out contribution to the forums here. He can be such pistol at time, our TC.
Join Date: Mar 2002
Location: Here,there &everywhere
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
PPF1,
I can honestly say that I preffer to fly twins,specially when flying over Tiger Country,but unfortuanatly all of us are'nt in the position to decide that we won't fly singles anymore.
I can honestly say that I preffer to fly twins,specially when flying over Tiger Country,but unfortuanatly all of us are'nt in the position to decide that we won't fly singles anymore.
Guest
Posts: n/a
Some statistic approximations about failures, (a failure is a total catastrophic loss of full function):
Turbine engines fail at about 1: 250,000 hours for engine cause, about 1:100,000 hours for all causes (fuel lines, tanks, pilot fingers on switches).
Transmissions, rotors and such tough stuff fails about 1:10,000,000 hours to 1:100,000,000)
So, for a 10,000 helicopter fleet, where they each fly 500 hours per year, (this is approximately the world's civil helo fleet) we collectively log 5 million hours per year.
At the above failure rates, we can expect an engine failure every week (50 per year), a main rotor or main transmission failure every two years.
If we include all the military helos in the world (10,000 in the US alone, about the same for the rest of the world) we would triple the usage, and therefore increase the likelihood of occurrence by a factor of three.
Three engine failures a week, and a major rotor/transmission failure every 8 months.
To examine what it means to any one of us, we have to fly 200 years at 500 hours per year to get an engine failure, and we have to fly for 20,000 years before a transmission or rotor fails.
To compare to cars, in the US, one person dies about every 25,000,000 miles driven (100 million cars at 10,000 miles each, at 40,000 fatalities). If you drive 10,000 miles per year, you can expect to be killed every 2500 years in your car. This is slightly conservative, because there might be more than one occupant in the typical car, but then again, everything else in this post isn an approximation.
Turbine engines fail at about 1: 250,000 hours for engine cause, about 1:100,000 hours for all causes (fuel lines, tanks, pilot fingers on switches).
Transmissions, rotors and such tough stuff fails about 1:10,000,000 hours to 1:100,000,000)
So, for a 10,000 helicopter fleet, where they each fly 500 hours per year, (this is approximately the world's civil helo fleet) we collectively log 5 million hours per year.
At the above failure rates, we can expect an engine failure every week (50 per year), a main rotor or main transmission failure every two years.
If we include all the military helos in the world (10,000 in the US alone, about the same for the rest of the world) we would triple the usage, and therefore increase the likelihood of occurrence by a factor of three.
Three engine failures a week, and a major rotor/transmission failure every 8 months.
To examine what it means to any one of us, we have to fly 200 years at 500 hours per year to get an engine failure, and we have to fly for 20,000 years before a transmission or rotor fails.
To compare to cars, in the US, one person dies about every 25,000,000 miles driven (100 million cars at 10,000 miles each, at 40,000 fatalities). If you drive 10,000 miles per year, you can expect to be killed every 2500 years in your car. This is slightly conservative, because there might be more than one occupant in the typical car, but then again, everything else in this post isn an approximation.
Join Date: Jul 2002
Location: too near London
Posts: 214
Likes: 0
Received 0 Likes
on
0 Posts
Great post NP, but I'd say it's not exactly comparing like with like - with aircraft you quote mechanical failure not death or injury rates( for each accident, rather than total headcount), and the opposite with motorists. Presumably the debate is about meaningful conclusions drawn from sensible analysis of statistics, rather than common sense or anecdotal evidence, and whether the gain in reliability is worth the extra cost? My view is that the FedEx experience of SE Caravans alone makes the position of the Euroland authorities a bit tenuous, and the resistanc to twin engine single prop. aircraft idiotic
Here's a nice statistic: the UK police kill about 30 people a year during car chases, That's roughly 3 times the fatalities for GA helicopters in the UK. And you thought flying Helicopters with one engine was dangerous.
Here's a nice statistic: the UK police kill about 30 people a year during car chases, That's roughly 3 times the fatalities for GA helicopters in the UK. And you thought flying Helicopters with one engine was dangerous.
Join Date: Jan 2001
Location: UK
Age: 71
Posts: 1,364
Likes: 0
Received 0 Likes
on
0 Posts
nr,
I know I shouldn't rise to the bait, BUT the police do not kill 30 people per year in pursuits - with writing skills like that, there is a career for you as a journalist.
There are around 30 fatalities that occur annually associated with pursuits by the police of vehicles that fail to stop when required to do so. The majority are caused when the "other" car crashes or collides with third party vehicles, people etc.
There are around 3,000 fatalities that occur that are nothing to do with police pursuits.
There is an almost irresistable temptation to divert this thread onto a new direction, but I will be strong..
I know I shouldn't rise to the bait, BUT the police do not kill 30 people per year in pursuits - with writing skills like that, there is a career for you as a journalist.
There are around 30 fatalities that occur annually associated with pursuits by the police of vehicles that fail to stop when required to do so. The majority are caused when the "other" car crashes or collides with third party vehicles, people etc.
There are around 3,000 fatalities that occur that are nothing to do with police pursuits.
There is an almost irresistable temptation to divert this thread onto a new direction, but I will be strong..
The Reverend Nicholas of Lappos opined (in part):
I love statements like that. They're so laughably contradictory. On one hand, we have one pilot per week suffering an engine failure. On the other hand, we have those same fifty pilots (justifiably?) crying out, "Blimey! I've only been flying for two years! This ain't supposed to be happening to me for another 198 years. Drat the luck! If I ever get my hands on that Nick Lappos, I'll..."
This is why the comparative study of statistical percentages is so silly. It might have some relevance in a general sort of way to the whole industry, but it is meaningless to us individually. Just show me the cold, hard failure-rate numbers and let me draw my own conclusions without tossing in a fruit salad of other "criteria," thanka, thankavrymch (as Elvis used to say).
The Nickmeister does pass one an interesting factoid, if any of his figures can be believed (egad, why would we not!): Engine failures occur far more often than other drivetrain failures. I know that the "single engines are just as safe" guys will choke on this before agreeing with it. Nick makes a darn good argument for having two...what do the Aussies call them...donks?
I sort of rest me case.
Now, I understand why a cheapskate, sc*mbag operator would only want aircraft with one engine, but why a PILOT would argue against two engines is simply unbelievable to me. Wait...hold the phone! Now I remember. It's because that second engine would add a level of complexity that would actually contribute to having an accident.
What incompetent, unskilled simpletons we must have flying helicopters 'round the world, eh?...if they would eschew the increased safety of a second engine on the grounds that it would make the machine far too complicated for their meager stick-wiggling talents.
No wonder helicopter pilots are so highly thought-of within the rest of the aviation industry!
At the above failure rates, we can expect an engine failure every week (50 per year), a main rotor or main transmission failure every two years.
To examine what it means to any one of us, we have to fly 200 years at 500 hours per year to get an engine failure, and we have to fly for 20,000 years before a transmission or rotor fails.
To examine what it means to any one of us, we have to fly 200 years at 500 hours per year to get an engine failure, and we have to fly for 20,000 years before a transmission or rotor fails.
I love statements like that. They're so laughably contradictory. On one hand, we have one pilot per week suffering an engine failure. On the other hand, we have those same fifty pilots (justifiably?) crying out, "Blimey! I've only been flying for two years! This ain't supposed to be happening to me for another 198 years. Drat the luck! If I ever get my hands on that Nick Lappos, I'll..."
This is why the comparative study of statistical percentages is so silly. It might have some relevance in a general sort of way to the whole industry, but it is meaningless to us individually. Just show me the cold, hard failure-rate numbers and let me draw my own conclusions without tossing in a fruit salad of other "criteria," thanka, thankavrymch (as Elvis used to say).
The Nickmeister does pass one an interesting factoid, if any of his figures can be believed (egad, why would we not!): Engine failures occur far more often than other drivetrain failures. I know that the "single engines are just as safe" guys will choke on this before agreeing with it. Nick makes a darn good argument for having two...what do the Aussies call them...donks?
I sort of rest me case.
Now, I understand why a cheapskate, sc*mbag operator would only want aircraft with one engine, but why a PILOT would argue against two engines is simply unbelievable to me. Wait...hold the phone! Now I remember. It's because that second engine would add a level of complexity that would actually contribute to having an accident.
What incompetent, unskilled simpletons we must have flying helicopters 'round the world, eh?...if they would eschew the increased safety of a second engine on the grounds that it would make the machine far too complicated for their meager stick-wiggling talents.
No wonder helicopter pilots are so highly thought-of within the rest of the aviation industry!
Join Date: Nov 2000
Location: UK
Posts: 183
Likes: 0
Received 0 Likes
on
0 Posts
Odd attitude you've got for a newbie, Pprune Fanny#1.
If you'd been around the forum a little longer you'd be able to understand TC's post which, roughly translated, means 'Oh Gawd! Not that same old chestnut which has been done to death so many times.' You'd also know TC is an experienced aviator who makes valuable contributions to discussions.
If you'd been around the forum a little longer you'd be able to understand TC's post which, roughly translated, means 'Oh Gawd! Not that same old chestnut which has been done to death so many times.' You'd also know TC is an experienced aviator who makes valuable contributions to discussions.