Restricted takeoffs, VRS, and ground effect
What about the guy who spends his entire life flying low level, in the weeds, dodging obstacles, hovering over hostile terrain close to solid (moving)objects and never hit anything after 30yrs? And in that same time frame experienced 3 engine failures. How do you think they view the risk of donk's stopping when they review their risk factors?
I guess - looking at it from a regulatory perspective - the authorities can only do so much towards risk assessing the human being who drives helicopters - after that it is all about pot luck and whether he got out of bed the right side on the morning of his CFIT. No amount of gadgetry will ALARP this guy.
However, if it is an object - like an engine - you can risk assess it 100% and hence engine failures, though they are rare (for some) - can be catered for to remove even the slightest risk during take-off and landing in particular. Hence the performance profiles designed to protect life in public transport - no?
I guess - looking at it from a regulatory perspective - the authorities can only do so much towards risk assessing the human being who drives helicopters - after that it is all about pot luck and whether he got out of bed the right side on the morning of his CFIT. No amount of gadgetry will ALARP this guy.
However, if it is an object - like an engine - you can risk assess it 100% and hence engine failures, though they are rare (for some) - can be catered for to remove even the slightest risk during take-off and landing in particular. Hence the performance profiles designed to protect life in public transport - no?
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However, if it is an object - like an engine - you can risk assess it 100% and hence engine failures, though they are rare (for some) - can be catered for to remove even the slightest risk during take-off and landing in particular. Hence the performance profiles designed to protect life in public transport - no?
Irrational at the cost of helicopter effectiveness and performance.
The twin engined arguements are corrupt and wrong 1x10^-10 is a bogus theoretical figure damaging helicopter's future.
The attempt to increase the weight of helicopter per payload is a strategy designed to rip off government procurement processes and oil companies - especially in the military where the helicopter effectiveness was severely crippled by carrying spare engines around in Afgan rather than food ammunition etc. ridiculous (massive cost - poor effectiveness)
Agree with Nick.
The attempt to increase the weight of helicopter per payload is a strategy designed to rip off government procurement processes and oil companies - especially in the military where the helicopter effectiveness was severely crippled by carrying spare engines around in Afgan rather than food ammunition etc. ridiculous (massive cost - poor effectiveness)
Oh and by the way, military aircraft need more redundancy since they get shot at a lot so having a spare engine to get you home rather than crashing in enemy territory is quite a good idea.
if military effectiveness was crippled (which I don't think it was) then lack of performance by old aircraft at high density altitudes and OATs was the limiting factor (Sea King, Lynx and to some extent Merlin).
The military requirement is completely irrelevant to the PC1/2 performance considerations on this thread.
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Single v twin...again? Don't make it military either, from records Hurricanes and Spitfires had only the one donk - and yes I realise they're not helicopters. Single engine Hueys in Vietnam? The Afghan war highlighted lots of issues, especially DA. Even an old RN colleague had an engine failure in a Lynx resulting in n emergency landing in Greece, not enough power to get into a hover back to the ship....at sea level!
Twin engines really should be for niche markets, the money saved by the odds of an engine failure make it more than worth it. We all seem to be happy for one engine during training,
Twin engines really should be for niche markets, the money saved by the odds of an engine failure make it more than worth it. We all seem to be happy for one engine during training,
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"The weight in engines, fuel and lost payload spent making you immune to engine failure in the 10 seconds of takeoff rob you of a hundred more important safety features that we leave off to save their weight."
Forgive my ignorance, but what safety features are you referring to that get left out to save weight? Redundant systems? I fly an old aircraft so I guess I'm not up to date on what these safety features would entail. Thanks!
Forgive my ignorance, but what safety features are you referring to that get left out to save weight? Redundant systems? I fly an old aircraft so I guess I'm not up to date on what these safety features would entail. Thanks!
We all seem to be happy for one engine during training,
Once you start operating with pax, the risk to life (in terms of numbers) increases and the size and power of that single engine has to increase to cope with the extra payload. Once you start moving pax and cargo you need even more power espeically at high DA.
At some point you come to the conclusion that 2 quite powerful engines are possibly better than one extra powerful one even though the mathematical risk of a single engine failure is very low - it is one of the few single point failures you can do something about relatively easily unlike double/no tail rotors or twin main rotors (clearly not impossible but they bring an increase in engineering complexity).
Anyone going to convince a regulator to go back to single engine ops for all helos??? Would you cross the Atlantic in a single engine A380? the probability of an engine failure is so theoretically low that by the arguments presented on this thread, it should be common place.
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Chuklehead : The thing to understand is that redundancy is not all it's cracked up to be. Better to have one system unlikely to fail than two dodgy ones one to catch the frequent failure of the other... don't think about having a spare tailrotor think instead of making one that can withstand the fabled test chicken. SIMPLEX theory is quite good. What do you want in your car a strong reliable braking system or a marginal one with a spare for when the main one doesn't work?
Instead of wasting payload on carrying a spare engine/gearbox and it's EXTRA fuel , spend it on critical components.
Engines are simple to duplicate and it is obvious to the layman that it sounds like a good idea... but what does the layman know? They think a helicopter falls out of the sky on engine failure, they also don't appreciate that engines are not allways a good thing... they explode catch fire and cause other problems .. so doubling the exposure to that is not such a great idea either.
This being shot at nonsense is just that - in Vietnam very few engines were hit despite taking fire often. The performance loss from carrying 2 engines is worse than the payload and performance loss, as Crab quite rightly points out in the Lynx, Sea king and to some extent the THREE ENGINED Merlin. (rubbish reliability/serviceability ratio etc chronically ineffective in Bang/Buck)
Sure good thing the Chinook was there (needing both engines)
When you need both engines to perform in a twin at altitude you are twice as exposed to engine failure than in a single - as well as carrying less life-saving supplies etc
It is not correct to say that higher DA favours 2 engines quite the opposite ref: AS350B3 compare to the almost useless AS355. Engine failure is not the problem in the B3 (and neither was it in the Gazelle - which would have done a better job bang per buck in Afgan surely?)
Crab: as for the single engined 380 you do have a good point and that is a matter of scale; the bigger the aircraft gets and the smaller the proportion of payload that is spent on carrying the spare engines around, the more it makes sense to carry 'redundant' engines around with you, like the payload rational for carrying a defribulator when you have 600 pax, small proportion of weight, high chance of it being useful. In the 380 also it's engine off landing characteristics are not as good as a helicopter. A 160kt arrival in a 300 ton aircraft is not going to be pretty. Landing gently at no airspeed (even at sea) is not such a bad thing.
Instead of wasting payload on carrying a spare engine/gearbox and it's EXTRA fuel , spend it on critical components.
Engines are simple to duplicate and it is obvious to the layman that it sounds like a good idea... but what does the layman know? They think a helicopter falls out of the sky on engine failure, they also don't appreciate that engines are not allways a good thing... they explode catch fire and cause other problems .. so doubling the exposure to that is not such a great idea either.
This being shot at nonsense is just that - in Vietnam very few engines were hit despite taking fire often. The performance loss from carrying 2 engines is worse than the payload and performance loss, as Crab quite rightly points out in the Lynx, Sea king and to some extent the THREE ENGINED Merlin. (rubbish reliability/serviceability ratio etc chronically ineffective in Bang/Buck)
Sure good thing the Chinook was there (needing both engines)
When you need both engines to perform in a twin at altitude you are twice as exposed to engine failure than in a single - as well as carrying less life-saving supplies etc
It is not correct to say that higher DA favours 2 engines quite the opposite ref: AS350B3 compare to the almost useless AS355. Engine failure is not the problem in the B3 (and neither was it in the Gazelle - which would have done a better job bang per buck in Afgan surely?)
Crab: as for the single engined 380 you do have a good point and that is a matter of scale; the bigger the aircraft gets and the smaller the proportion of payload that is spent on carrying the spare engines around, the more it makes sense to carry 'redundant' engines around with you, like the payload rational for carrying a defribulator when you have 600 pax, small proportion of weight, high chance of it being useful. In the 380 also it's engine off landing characteristics are not as good as a helicopter. A 160kt arrival in a 300 ton aircraft is not going to be pretty. Landing gently at no airspeed (even at sea) is not such a bad thing.
Better to have one system unlikely to fail than two dodgy ones one to catch the frequent failure of the other..
The difference comes when an engine does fail in a single compared to a twin - if you are over a nice landing area with plenty of height to set up your EOL then no problem in a single BUT when you are at high AuM at low speed, low level or over inhospitable terrain/sea then a failure in a twin leaves you able to get home, a failure in a single leaves you dead....it's that simple.
In the car analogy, due you want single or dual circuit brakes, can you accept the weight penalty for ABS, traction and stability control, airbags etc etc none of which are essential for driving but all make it safer if something bad happens.
This being shot at nonsense is just that - in Vietnam very few engines were hit despite taking fire often.
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Nice retorts, guys! Crab, you are quite right, my plea was to assess safety in the actual operation, and add the next thing that can measurably increase safety. If you spend your job in OGE hover or at low altitude and low speed, OEI safety is clearly an important safety option.
Where do we need more safety attention? Helicopter instrument procedures and kits, Night equipage, CFIT solutions, DVE solutions, expert copilot systems that tell you what actually happened in an emergency, etc, etc.
BTW, Crab, engines being shot seemed to be pretty rare in Vietnam. Once we read of a Marine pilot getting a DFC, and the citation read something about him getting an engine failure and flying for 30 minutes over enemy territory on one engine. We tore out the article and took it to our Awards and Decorations officer, asking for our DFCs, since all our aircraft were single engine and we had about 1,000 hours each "over enemy territory"! He threw us out on our bums.
Where do we need more safety attention? Helicopter instrument procedures and kits, Night equipage, CFIT solutions, DVE solutions, expert copilot systems that tell you what actually happened in an emergency, etc, etc.
BTW, Crab, engines being shot seemed to be pretty rare in Vietnam. Once we read of a Marine pilot getting a DFC, and the citation read something about him getting an engine failure and flying for 30 minutes over enemy territory on one engine. We tore out the article and took it to our Awards and Decorations officer, asking for our DFCs, since all our aircraft were single engine and we had about 1,000 hours each "over enemy territory"! He threw us out on our bums.
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Go take a peak at CatPolH 305 (EASA regulation) the safety systems that demands as well as risk assessments and OEM reports on failure data will show you the future, and trust me its' no better than the past, but the legislature have covered their arses magnificently.
I spend a lot of time flying rotary at night/IFR (couple of hundred hours a year night and IFR, with 10 500 hour rotary and another 5 000 fixed wing total time) and the spare engine is welcome, as are the auto-pilots, nav systems, coffee cup holders and illuminated approach plate holders, HUMS is great for telling me when bits are as shagged as I am, I just fail to understand how last year EGLW and LFPI were fine for my aircraft and this year I've got to do a f***ing great paper work exercise to fly the same aircraft to the same LZ's I did last year. All that has done is take my time and effort and improved nothing in safety.
SND
I spend a lot of time flying rotary at night/IFR (couple of hundred hours a year night and IFR, with 10 500 hour rotary and another 5 000 fixed wing total time) and the spare engine is welcome, as are the auto-pilots, nav systems, coffee cup holders and illuminated approach plate holders, HUMS is great for telling me when bits are as shagged as I am, I just fail to understand how last year EGLW and LFPI were fine for my aircraft and this year I've got to do a f***ing great paper work exercise to fly the same aircraft to the same LZ's I did last year. All that has done is take my time and effort and improved nothing in safety.
SND
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CRAB:
Yup I think the answer there is you want a reliable single system, and you can use the weight saving (weight not so critical in a car) to run the ABS, traction control, airbags etc etc
There's a much better safety yeild available in helicopters from other things than duplication the relatively complex and low yeilding engine at such a high cost to payload effectiveness, especially daft to carry enough spare engine to mitigate engine failure risk during the 8 second window of transition, especially considering the risk of prolonging, in an upwards and backwards takeoff, the exposure to tailrotors and other risks (about 30 seconds of that exposure instead)
Anyhow some twin maths can just work, if the helicopter is big and the risk of landing is most likely to be fatal, like over jungle.
In the car analogy, due you want single or dual circuit brakes, can you accept the weight penalty for ABS, traction and stability control, airbags etc etc none of which are essential for driving but all make it safer if something bad happens.
There's a much better safety yeild available in helicopters from other things than duplication the relatively complex and low yeilding engine at such a high cost to payload effectiveness, especially daft to carry enough spare engine to mitigate engine failure risk during the 8 second window of transition, especially considering the risk of prolonging, in an upwards and backwards takeoff, the exposure to tailrotors and other risks (about 30 seconds of that exposure instead)
Anyhow some twin maths can just work, if the helicopter is big and the risk of landing is most likely to be fatal, like over jungle.
Last edited by Senior Pilot; 7th Aug 2015 at 00:26. Reason: Insert quotes
Yup I think the answer there is you want a reliable single system, and you can use the weight saving (weight not so critical in a car) to run the ABS, traction control, airbags etc etc
Weight not so critical in a car????? do you know less about cars than you do about helos?
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Crab I am just never rude to you at all, but you are sarcastic, rude and unclear.
are you trying to suggest that weight is more critical in a car than a helicopter? (seems odd, if that is what you are saying (unclear), you'll have to explain why). You think you know more than i do about fundamental car 'PoF' too? (showdown? £10k says you don't, if I win proceeds to next pprune bash!)
and incidentally the only brake failure accident I know of happened in a car with a dual (redundant) brake system design (Bentley).
Ref VRS Crab: "Don't worry about VRS - you won't get near the RoD required (probably somewhere around 12 - 1500'/min for your aircraft)."
That I guess originates from the recent opinion that VRS won't occur untill half the downwash speed? I don't think that is true nor helpful and as such would constitute dangerous advice. I have found that you can neatly slip into VRS at about 1/8th to 1/4 of the downwash speed.
tread drift re cars sorry - I'll probably get in trouble again but I am only answering crab's rather rude thread drifting point, crab won't get in trouble for this since he seems to be 'teachers pet'. I'm already in trouble for suggesting that the multi engine maths gets better for more engines (3,4,5). Although I am not allowed to say that IMO it's not worth it since the reliability goes down, KISS is a dirty word around here.
PS according to Nick L, Crab also seems to be quite wrong about the risk of engines being shot out, the Huey experience in Veitnam being an excellent example of utility of payload vs redundancy. thank you Nick.
are you trying to suggest that weight is more critical in a car than a helicopter? (seems odd, if that is what you are saying (unclear), you'll have to explain why). You think you know more than i do about fundamental car 'PoF' too? (showdown? £10k says you don't, if I win proceeds to next pprune bash!)
and incidentally the only brake failure accident I know of happened in a car with a dual (redundant) brake system design (Bentley).
Ref VRS Crab: "Don't worry about VRS - you won't get near the RoD required (probably somewhere around 12 - 1500'/min for your aircraft)."
That I guess originates from the recent opinion that VRS won't occur untill half the downwash speed? I don't think that is true nor helpful and as such would constitute dangerous advice. I have found that you can neatly slip into VRS at about 1/8th to 1/4 of the downwash speed.
tread drift re cars sorry - I'll probably get in trouble again but I am only answering crab's rather rude thread drifting point, crab won't get in trouble for this since he seems to be 'teachers pet'. I'm already in trouble for suggesting that the multi engine maths gets better for more engines (3,4,5). Although I am not allowed to say that IMO it's not worth it since the reliability goes down, KISS is a dirty word around here.
PS according to Nick L, Crab also seems to be quite wrong about the risk of engines being shot out, the Huey experience in Veitnam being an excellent example of utility of payload vs redundancy. thank you Nick.
AnFI - If I am rude to you it is because you insist on trying to hijack threads with your own pet hobby horse ie singles are better than twins.
If weight is not important in cars (and I didn't say it was more important than in helos) why do car manufacturers, especially of performance cars, spend so much R and D reducing the weight of their vehicles? Oh yes...... it is to improve performance which is the whole subject of this thread!
I use Nick L's VRS figures since they are derived from testing as opposed to yours which are just your opinion and ignore any real evidence to the contrary.
Your childish bet is frankly typical of your posts - you don't like being criticised and react in playground fashion when you are.
Yes, I was wrong about the number of engines shot out in Vietnam - it still doesn't validate any of your hobby horse arguments though.
If weight is not important in cars (and I didn't say it was more important than in helos) why do car manufacturers, especially of performance cars, spend so much R and D reducing the weight of their vehicles? Oh yes...... it is to improve performance which is the whole subject of this thread!
I use Nick L's VRS figures since they are derived from testing as opposed to yours which are just your opinion and ignore any real evidence to the contrary.
Your childish bet is frankly typical of your posts - you don't like being criticised and react in playground fashion when you are.
Yes, I was wrong about the number of engines shot out in Vietnam - it still doesn't validate any of your hobby horse arguments though.
I think that's a bit unfair Crab - you mocked: "Weight not so critical in a car?" ... which is quite a silly thing to say. If course weight is not so critical in a car [as in a helicopter]. An overweight car can still be quite usefully and safely driven whereas an overweight helicopter either cannot get off the ground or cannot get safely back onto the ground!
But what is worse, is you went on to rewrite history:
You say "If weight is not important in cars" but that's not what was said and quite different to what you said which is "not so critical".
and I don't believe "improve performance" is the subject of the thread; it is "improve safety".
and "and I didn't say it was more important than in helos" - no, but you implied it was at least as critical.
But what is worse, is you went on to rewrite history:
You say "If weight is not important in cars" but that's not what was said and quite different to what you said which is "not so critical".
and I don't believe "improve performance" is the subject of the thread; it is "improve safety".
and "and I didn't say it was more important than in helos" - no, but you implied it was at least as critical.
Krypton John
is what AnFI wrote in reply to what I said which was
it is your interpretation of my words which were meant to highlight that weight is indeed important in cars - I didn't say it was more critical which is what AnFI seems to believe I meant.
I would suggest there are very many automotive safety experts who would disagree with that statement - I do know what you meant but that is what happens when you take every word literally and ignore context.
The thread was about helipad profiles which are all about performance which leads to increased safety.
You are encouraging the troll that is AnFI who only has one tune about singles being better than twins.
are you trying to suggest that weight is more critical in a car than a helicopter?
Weight not so critical in a car?????
An overweight car can still be quite usefully and safely driven
The thread was about helipad profiles which are all about performance which leads to increased safety.
You are encouraging the troll that is AnFI who only has one tune about singles being better than twins.
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Thank you Krypton John.
Yes Crab I am afraid it is just your misunderstanding which led to your frustration and rudeness and additionally I think if you insult my knowledge of cars as well as helicopters then I have every right to demand that you justify that rudeness which you refuse to do [insulting me further instead again], so you should retract that too please.
the only person who has been wrong here is you as you have admitted yourself - what you are not capable of doing is apologising for being so damn rude, being rude again to me in response to KJ, it's outrageous !
The way you chose to address the serious points I make through insult is demeaning to you, and I think you come from a better place than that (surely?)
The relationship of weight/power/payload is key [to safety[in a helicopter]]. As long as folk like yourself will not seriously engage in discussing these issues in a serious manner, relying on some bizzare gut feel, and DISHONEST MATHS (like the squaring of 1x10^-5) then longer we'll be condemned to the dark ages.
Yes Crab I am afraid it is just your misunderstanding which led to your frustration and rudeness and additionally I think if you insult my knowledge of cars as well as helicopters then I have every right to demand that you justify that rudeness which you refuse to do [insulting me further instead again], so you should retract that too please.
the only person who has been wrong here is you as you have admitted yourself - what you are not capable of doing is apologising for being so damn rude, being rude again to me in response to KJ, it's outrageous !
The way you chose to address the serious points I make through insult is demeaning to you, and I think you come from a better place than that (surely?)
The relationship of weight/power/payload is key [to safety[in a helicopter]]. As long as folk like yourself will not seriously engage in discussing these issues in a serious manner, relying on some bizzare gut feel, and DISHONEST MATHS (like the squaring of 1x10^-5) then longer we'll be condemned to the dark ages.
Last edited by AnFI; 12th Aug 2015 at 08:59.
See what I mean KJ?
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As I said:
"The relationship of weight/power/payload is key [to safety[in a helicopter]].
As long as folk like yourself will not seriously engage in discussing these issues in a serious manner ...... we'll be condemned to the dark ages."
KJ?
"The relationship of weight/power/payload is key [to safety[in a helicopter]].
As long as folk like yourself will not seriously engage in discussing these issues in a serious manner ...... we'll be condemned to the dark ages."
KJ?
Perhaps you should fly in situations you are not familiar with before you bang on about maths and single engine superiority.
Try 250 nm out into the North or South Atlantic (I've done both) in the dark and see how comfortable your maths makes you feel in a single instead of a twin.
Maybe sit in a hover against a mountainside in the dark and rain with 240' of winch cable and 2 pink bodies hung underneath you and see how comfortable you and your crew are with mathematical probabilities of engine failures in a single.
Perhaps IMC with a 200' cloudbase so you can get in on ILS or PAR with several important pax in the back - I'm sure your assertion that singles are at least as safe as twins will give great comfort.
Or North Sea with 15 bears in the back in shocking weather and a high sea state that would make ditching in a single (or anything else for that matter) very difficult.
so where are your 3000 shp single gas turbines?
Try 250 nm out into the North or South Atlantic (I've done both) in the dark and see how comfortable your maths makes you feel in a single instead of a twin.
Maybe sit in a hover against a mountainside in the dark and rain with 240' of winch cable and 2 pink bodies hung underneath you and see how comfortable you and your crew are with mathematical probabilities of engine failures in a single.
Perhaps IMC with a 200' cloudbase so you can get in on ILS or PAR with several important pax in the back - I'm sure your assertion that singles are at least as safe as twins will give great comfort.
Or North Sea with 15 bears in the back in shocking weather and a high sea state that would make ditching in a single (or anything else for that matter) very difficult.
"The relationship of weight/power/payload is key [to safety[in a helicopter]].