Entering autos: discussion split from Glasgow crash thread
Purveyor of Egg Liqueur to Lucifer
SP,
Can we have another thread split please. Either on autorotations or aviation secrets.
I would like to read about issues directly related to the threads title and the new developments, rather than this tittle tattle.
Thanks
By the way chopjock, if that was you in your 500 over the weekend in S. Warwickshire, please fly a little higher in future, as when your donk stops, that certainly wasnt high enough in the event of... to avoid the town, no matter how much speed you may think you can trade for height by aft cyclic.
Can we have another thread split please. Either on autorotations or aviation secrets.
I would like to read about issues directly related to the threads title and the new developments, rather than this tittle tattle.
Thanks
By the way chopjock, if that was you in your 500 over the weekend in S. Warwickshire, please fly a little higher in future, as when your donk stops, that certainly wasnt high enough in the event of... to avoid the town, no matter how much speed you may think you can trade for height by aft cyclic.
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Sadly, AF447 would prove otherwise.
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Thomas Coupling
G0ULI (golf zero uniform lima india) happens to be my radio callsign, although I admit it might be deemed unfortunate in the context of this subject. I have fixed wing flying experience and attended the scene of a fatal light aircraft crash in a professional capacity many years ago, which prompted a lifelong interest in flight safety. I was mystified as to what set of circumstances could cause an apparently perfectly functional helicopter to fall out of the sky. It would seem from the answers in this forum and information elsewhere that something such as a vortex ring formation could in theory put a helicopter in such an attitude that the engines would stop from fuel starvation and in that event, the pilot would have very little time to recover the aircraft. I never knew that the main rotor rpm had to be constrained to within such tight limits or fully appreciated that a full main rotor stall would be unrecoverable irrespective of altitude. This thread has been most enlightening, irrespective of some of the irreverent comments. I have had several opportunities over the years to take a flight in a police helicopter, I never took up the offer, although friends thought I was mad not to. I will stick to fixed wing aircraft.
G0ULI (golf zero uniform lima india) happens to be my radio callsign, although I admit it might be deemed unfortunate in the context of this subject. I have fixed wing flying experience and attended the scene of a fatal light aircraft crash in a professional capacity many years ago, which prompted a lifelong interest in flight safety. I was mystified as to what set of circumstances could cause an apparently perfectly functional helicopter to fall out of the sky. It would seem from the answers in this forum and information elsewhere that something such as a vortex ring formation could in theory put a helicopter in such an attitude that the engines would stop from fuel starvation and in that event, the pilot would have very little time to recover the aircraft. I never knew that the main rotor rpm had to be constrained to within such tight limits or fully appreciated that a full main rotor stall would be unrecoverable irrespective of altitude. This thread has been most enlightening, irrespective of some of the irreverent comments. I have had several opportunities over the years to take a flight in a police helicopter, I never took up the offer, although friends thought I was mad not to. I will stick to fixed wing aircraft.
To the decryers it is relevant to this thread. I maintain that IF the pilot was faced with a simultaneous and unexpected double engine failure, the chances of a successful entry into autorotation are fairly small due to the reaction time of someone accustomed to flying twins, and the very short time one has to get it right in a low inertia heli such as the 135. Especially if said pilot had been taught by TC to evaluate whether range, normal or short auto was required before moving the cyclic!
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Perhaps a better way of describing this "aft cyclic" thing is as my very experienced FI course instructor put it..."HOLD the attitude". That means you hold the attitude you need for what is happening with the helicopter and what you plan to do next. After engine failure at altitude in a small helicopter, when the nose will almost definitely drop or be about to, that means aft cyclic. In the hover it doesn't, and with larger helicopters with more inertia, fixed rotor systems etc...well, I'll leave that to those who have far more hours flying them than I do.
The really, really important point is that ALL helicopter pilots KNOW about this! You learn it from Exercise 7 of the Private Pilot's syllabus. You practice it over and over again. You re-learn it every time you convert to a new type, learning the differences (if there are any) for that type. It's not a secret in any way, in fact it's emphasised and practised to such an extent that some instructors feel it's overdone and we should do more stuff about other emergencies instead . There is absolutely no chance at all that the pilot in this accident didn't know precisely what was recommended for engine failure in his helicopter. Peter Gillies, I don't like being this hard on anyone in public, but you got that completely WRONG!!!!
Now that's sorted, can we get back to the main topic of the thread. Please!
The really, really important point is that ALL helicopter pilots KNOW about this! You learn it from Exercise 7 of the Private Pilot's syllabus. You practice it over and over again. You re-learn it every time you convert to a new type, learning the differences (if there are any) for that type. It's not a secret in any way, in fact it's emphasised and practised to such an extent that some instructors feel it's overdone and we should do more stuff about other emergencies instead . There is absolutely no chance at all that the pilot in this accident didn't know precisely what was recommended for engine failure in his helicopter. Peter Gillies, I don't like being this hard on anyone in public, but you got that completely WRONG!!!!
Now that's sorted, can we get back to the main topic of the thread. Please!
Brother bastOn speaks the Truth!
As I have said on many occasions here....
"Limitations are for NORMAL Operations"!
There is NOTHING Normal about Crashing!
....worrying about a rrpm overspeed should be the last of your worries, the more rrpm when it comes to that final - one chance only - pull up on the collective the better.
"Limitations are for NORMAL Operations"!
There is NOTHING Normal about Crashing!
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Gentlemen –
Thank you for your responses, both pro and con, regarding my emphasis on applying aft cyclic as well as collective down at the first sign of loss of power to the rotor system.
Yes, I call it the best kept secret in helicopters because very few helicopter pilots and instructors realize that not catching the rotor rpm before it drops below the point of no return is the end of the flight. The airplane equivalent is that of losing a wing in flight. Not a good way to fly.
Modern flight schools have been teaching a coordinated entry to training-type autorotations for years. Apply enough aft cyclic to restore the airframe attitude to what is was before the entry was initiated. Perfect. And in the relative sanitary situation that exists during flight instruction, with a CFI monitoring the actions of the student and demonstrating the correct performance of the maneuver, this works well. By sanitary I mean that the flight is conducted within a school atmosphere. All actions are predictable, there is a good place to land if needed, and mistakes can be caught before they turn into an emergency.
This is often not the case in the real world. If you believe that every helicopter pilot is expecting an engine failure at any moment during a flight, you are mistaken. Cyclic Back is dedicated to the hundreds, if not thousands, of helicopter pilots flying all over the world today who have never heard about Cyclic Back and are flying with earned confidence in their aircraft. And then wham. The engine quits without warning. These are the pilots I am addressing, not the freshly groomed perfectly trained pilots graduating from flight schools today.
This forum and the posts regarding the EC135 accident are excellent for the most part. The fact that Dave and his passengers contacted the roof with zero rotor rpm says something. The AAIB has already ruled out a seized main-rotor transmission or equivalent. The engines were not running on impact. So how can the helicopter end up descending with the rotor rpm going down to possibly zero?
Easy. As I said in my earlier post, allowing the rotor rpm to drop below the critical point with no engine power to bring it back into the operating range will cause this to happen every time. No exceptions. And as I said before, there is no recovery from this situation. None.
Notice how all of the flight manuals and training related publications emphasize bottoming the collective at the first sign of an engine failure. They don’t say how much or how rapidly to lower the collective. Just do it, and if the rotor tends to overspeed, pull enough pitch to keep it in the green.
Applying aft cyclic should be done the same way. Just do it. If it was not necessary, then fine. No harm done.
I smiled when I read the posts saying that Cyclic Back was not a good thing to do in a hover, high, low or otherwise. Well, duh. Of course not. Nor is it needed during a low power descent where air is already passing upwards through the rotor disc. It applies directly to the helicopter in powered forward flight, where the pilot is caught completely by surprise with an engine or drive-line failure. Or maybe the pilot is not caught completely by surprise as in the out-of-fuel non-survivable crash of an EMS helicopter in Missouri on August 26, 2011. In any case, if the cyclic is not brought back in time, the rotor rpm continues dropping and can never be stopped or recovered.
Part of our company is our Part 141 flight school in operation since 1980. During that time we have given initial, advanced and recurrency flight training to helicopter pilots of all levels of skill and experience, and we have repeatedly seen high-time professional pilots either do nothing with the cyclic, or worse yet, push it forward, when power was quickly reduced to idle. And the majority of recurrency training has been with law enforcement and military- trained pilots.
Oh, and the noises heard by some witnesses to the crash of the EC135 could have been caused by one or both engines attempting to reignite during the descent.
Finally, this: If you have access to the July 2013 issue of Aviation International News, look for an article about Cyclic Back in the letters to the editor section of the magazine.
Thank you, gentlemen, for allowing me to contribute my thoughts to this perplexing and very unfortunate accident.
Pete Gillies
Thank you for your responses, both pro and con, regarding my emphasis on applying aft cyclic as well as collective down at the first sign of loss of power to the rotor system.
Yes, I call it the best kept secret in helicopters because very few helicopter pilots and instructors realize that not catching the rotor rpm before it drops below the point of no return is the end of the flight. The airplane equivalent is that of losing a wing in flight. Not a good way to fly.
Modern flight schools have been teaching a coordinated entry to training-type autorotations for years. Apply enough aft cyclic to restore the airframe attitude to what is was before the entry was initiated. Perfect. And in the relative sanitary situation that exists during flight instruction, with a CFI monitoring the actions of the student and demonstrating the correct performance of the maneuver, this works well. By sanitary I mean that the flight is conducted within a school atmosphere. All actions are predictable, there is a good place to land if needed, and mistakes can be caught before they turn into an emergency.
This is often not the case in the real world. If you believe that every helicopter pilot is expecting an engine failure at any moment during a flight, you are mistaken. Cyclic Back is dedicated to the hundreds, if not thousands, of helicopter pilots flying all over the world today who have never heard about Cyclic Back and are flying with earned confidence in their aircraft. And then wham. The engine quits without warning. These are the pilots I am addressing, not the freshly groomed perfectly trained pilots graduating from flight schools today.
This forum and the posts regarding the EC135 accident are excellent for the most part. The fact that Dave and his passengers contacted the roof with zero rotor rpm says something. The AAIB has already ruled out a seized main-rotor transmission or equivalent. The engines were not running on impact. So how can the helicopter end up descending with the rotor rpm going down to possibly zero?
Easy. As I said in my earlier post, allowing the rotor rpm to drop below the critical point with no engine power to bring it back into the operating range will cause this to happen every time. No exceptions. And as I said before, there is no recovery from this situation. None.
Notice how all of the flight manuals and training related publications emphasize bottoming the collective at the first sign of an engine failure. They don’t say how much or how rapidly to lower the collective. Just do it, and if the rotor tends to overspeed, pull enough pitch to keep it in the green.
Applying aft cyclic should be done the same way. Just do it. If it was not necessary, then fine. No harm done.
I smiled when I read the posts saying that Cyclic Back was not a good thing to do in a hover, high, low or otherwise. Well, duh. Of course not. Nor is it needed during a low power descent where air is already passing upwards through the rotor disc. It applies directly to the helicopter in powered forward flight, where the pilot is caught completely by surprise with an engine or drive-line failure. Or maybe the pilot is not caught completely by surprise as in the out-of-fuel non-survivable crash of an EMS helicopter in Missouri on August 26, 2011. In any case, if the cyclic is not brought back in time, the rotor rpm continues dropping and can never be stopped or recovered.
Part of our company is our Part 141 flight school in operation since 1980. During that time we have given initial, advanced and recurrency flight training to helicopter pilots of all levels of skill and experience, and we have repeatedly seen high-time professional pilots either do nothing with the cyclic, or worse yet, push it forward, when power was quickly reduced to idle. And the majority of recurrency training has been with law enforcement and military- trained pilots.
Oh, and the noises heard by some witnesses to the crash of the EC135 could have been caused by one or both engines attempting to reignite during the descent.
Finally, this: If you have access to the July 2013 issue of Aviation International News, look for an article about Cyclic Back in the letters to the editor section of the magazine.
Thank you, gentlemen, for allowing me to contribute my thoughts to this perplexing and very unfortunate accident.
Pete Gillies
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Yes, I call it the best kept secret in helicopters because very few helicopter pilots and instructors realize that not catching the rotor rpm before it drops below the point of no return is the end of the flight
Just a numbered other
Absolutely Shy Torque.
That was drummed in to me very early on in helicopter training, and passed on to my students later on.
I can't imagine any uk military trained helo pilot not knowing this, and would expect his civilian counterpart to be similarly aware.
It ain't called critical RPM for fun.
That was drummed in to me very early on in helicopter training, and passed on to my students later on.
I can't imagine any uk military trained helo pilot not knowing this, and would expect his civilian counterpart to be similarly aware.
It ain't called critical RPM for fun.
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PeteGillies, you are quite unbelievable. You're talking, in the main, to a bunch of very well qualified and experienced pilots here, not complete rookies who know nothing whatsoever about helicopters. You're being condescending to the point that I wonder....are you for real?
Finally, please don't assume we're all "gentlemen"; some of those of the other gender have been flying helicopters for quite a long time.
Finally, please don't assume we're all "gentlemen"; some of those of the other gender have been flying helicopters for quite a long time.
Well in PG's defence I have been caught out by a recently trained pilot who entered a practice autorotation in an EC225 (aircraft, not Sim) by flooring the collective without moving the cyclic. We didn't even take the engines back to idle! Anyway, after I had scraped myself off the cockpit roof I just had time to grab the collective as the disc "bit" and the Nr went wild with the Nr gauge rotating nearly as fast as the rotors! I yanked up the collective and caught it right on the max transient power off Nr limit, above which it would have been head change time.
Others have been less aggressive with the lowering but still unaware that they should move the cyclic back when doing this from the cruise. So his point is valid and whilst you can poo poo it if you know it already, you should be aware that there are some professional pilots out there who don't know it. I know that for a fact!
And don't forget that quite clearly our own TC doesn't know it, nor presumably do his students.
Others have been less aggressive with the lowering but still unaware that they should move the cyclic back when doing this from the cruise. So his point is valid and whilst you can poo poo it if you know it already, you should be aware that there are some professional pilots out there who don't know it. I know that for a fact!
And don't forget that quite clearly our own TC doesn't know it, nor presumably do his students.
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HC, the comment to which I said "rubbish" was not about what the pilot does in the simulator, it was about an alleged basic flaw in theoretical knowledge and training. Read my post again and look at the relevant quote from PG. I stand by that response. If what he says is true, there is a basic flaw in the way that pilots are trained in the USA.
That apart, from my own time instructing on rotary wing and fixed wing, both in the air and in the sim (I ran an RAF helicopter simulator project some twenty years ago), what a pilot knows and what he does on a particular aircraft type may not be quite the same thing - at least, not until he's had a few goes at it. That's what training is actually for - to get used to the best way to fly a particular aircraft type, not to see how bad they are when they begin the training session!
That apart, from my own time instructing on rotary wing and fixed wing, both in the air and in the sim (I ran an RAF helicopter simulator project some twenty years ago), what a pilot knows and what he does on a particular aircraft type may not be quite the same thing - at least, not until he's had a few goes at it. That's what training is actually for - to get used to the best way to fly a particular aircraft type, not to see how bad they are when they begin the training session!
I don't know what they are trained to do, but it seems that not long after qualifying they have either forgotten it or never knew. Whether it is relevant that many of our pilots now train in the USA, I don't know.
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Could trying to gain even a tiny bit of height to clear the top of this building cause a rotor stall?
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"Yes, I call it the best kept secret in helicopters because very few helicopter pilots and instructors realize that not catching the rotor rpm before it drops below the point of no return is the end of the flight"
Many pilots and training facilities will find this statement insulting.
What you say is certainly not reflective of my experience in the UK. During my private and commercial licence training and the instruction I've received during annual checks etc (at various training facilities around the UK) I never found instructors to be as naive as you suggest or training to be as weak as you suggest.
I think your advice, whilst well founded, is too generalised across aircraft types and flight emergency scenarios and you should adapt it a bit.
It sounds a bit like your motivation is to create a niche about which to write a book.
Many pilots and training facilities will find this statement insulting.
What you say is certainly not reflective of my experience in the UK. During my private and commercial licence training and the instruction I've received during annual checks etc (at various training facilities around the UK) I never found instructors to be as naive as you suggest or training to be as weak as you suggest.
I think your advice, whilst well founded, is too generalised across aircraft types and flight emergency scenarios and you should adapt it a bit.
It sounds a bit like your motivation is to create a niche about which to write a book.
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Back in the 70's I experiences 3 engine failures in single engine helicopters, 2 in a Bell 47 and 1 in a Bell 205. I have tried reliving those incidents but all I can confirm is lowering the collective. What I did wth the cyclic was automatic, slight nose down from the hover, reduced airspeed with the night failure and turned to avoid obstacles in the 205. All different. cyclic movements.
One was during a 100 ft hover while observing a gunnery shoot along a tree line, another during night cross country training and the third in the 205 on finals to a helipad.
What I'm trying to say is you cannot fly the aircraft by numbers, with the correct training you will react instinctivly, and by the time you breathe out you will be set up either for landing or continued flight.
One was during a 100 ft hover while observing a gunnery shoot along a tree line, another during night cross country training and the third in the 205 on finals to a helipad.
What I'm trying to say is you cannot fly the aircraft by numbers, with the correct training you will react instinctivly, and by the time you breathe out you will be set up either for landing or continued flight.
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No matter what the fuel gauges were reading, the cause of this crash was not fuel exhaustion.
There are some things you have to practise until they are instinctive. No thinking. For an aeroplane: Too slow, nose down. Others I call "mantras". One is: If the engine stops? Think: Turn the fuel on. Silly? Read the light aircraft crash reports.
Surely the first thing a student rotary-wing pilot learns is the wings must move to fly. Certainly a fixed-wing student pilot knows. No rotor rpm in a helicopter is the equivalent of an aerodynamic stall in a tail-heavy aeroplane?
Peter Gillies' discussion. I am not surprised it created a furore. But the proof of the pudding is in the eating. This aircraft was not autorotating when it went through the roof.
Faulty gauges. Was the pilot misled into thinking it was fuel exhaustion when it was fuel starvation? That is, unregistered "hidden" fuel in the main tank but none in the supply tanks. Faulty gauges and faulty pump at the same time?
There are some things you have to practise until they are instinctive. No thinking. For an aeroplane: Too slow, nose down. Others I call "mantras". One is: If the engine stops? Think: Turn the fuel on. Silly? Read the light aircraft crash reports.
Surely the first thing a student rotary-wing pilot learns is the wings must move to fly. Certainly a fixed-wing student pilot knows. No rotor rpm in a helicopter is the equivalent of an aerodynamic stall in a tail-heavy aeroplane?
Peter Gillies' discussion. I am not surprised it created a furore. But the proof of the pudding is in the eating. This aircraft was not autorotating when it went through the roof.
Faulty gauges. Was the pilot misled into thinking it was fuel exhaustion when it was fuel starvation? That is, unregistered "hidden" fuel in the main tank but none in the supply tanks. Faulty gauges and faulty pump at the same time?
Mr Gillies: I have to read and re-read your posts to fully grasp your message and I am going to suggest that there is a disconnect caused by translation between the american and english language. 
[Does that sound condescending too?].
Statements like:
are bordering on the ridiculous. If you really have to broadcast this detritus please qualify it by pointing it at your fellow american pilots and not us europeans. Because, believe me - every professional pilot I have ever met has this ingrained in their DNA.
Reading back, I think we can reach an understanding as it is down to semenatics and also the way you have phrased it:
.
The correct (global) way to enter an auto after engine(s) failure is to lower the collective first (not dump it as HC keeps referring in all of his posts), followed by and this is the seminal point MAINTAINING attitude. The time frame between lowering of collective and cyclic input may be minimal but it is always done in this strict order: collective 1st and cyclic 2nd.
Some may say - ah, got you: To maintain attitude always requires aft cyclic. NOT the case...it all depends on where your LZ is.
Now if you don't believe me then take a look at DAPT's link to the FAA web site and read up on engine failures/autos. This is what the Feds are recommending to all their pilots:
.
.
.
I think I now know where you are coming from PG, you simply have to be more succinct about what you mean and how you post it [
].
And no more silly remarks about the bleedin bloody obvious re Nr decay.
[Does that sound condescending too?].Statements like:
very few helicopter pilots and instructors realize that not catching the rotor rpm before it drops below the point of no return is the end of the flight. The airplane equivalent is that of losing a wing in flight. Not a good way to fly
Reading back, I think we can reach an understanding as it is down to semenatics and also the way you have phrased it:
Thank you for your responses, both pro and con, regarding my emphasis on applying aft cyclic as well as collective down at the first sign of loss of power to the rotor system
The correct (global) way to enter an auto after engine(s) failure is to lower the collective first (not dump it as HC keeps referring in all of his posts), followed by and this is the seminal point MAINTAINING attitude. The time frame between lowering of collective and cyclic input may be minimal but it is always done in this strict order: collective 1st and cyclic 2nd.
Some may say - ah, got you: To maintain attitude always requires aft cyclic. NOT the case...it all depends on where your LZ is.
Now if you don't believe me then take a look at DAPT's link to the FAA web site and read up on engine failures/autos. This is what the Feds are recommending to all their pilots:
At the instant of engine failure, the main rotor blades are
producing lift and thrust from their angle of attack (AOA)
and velocity. By lowering the collective pitch, which must be
done immediately in case of an engine failure, lift and drag
are reduced, and the helicopter begins an immediate descent,
thus producing an upward flow of air through the rotor
system. This upward flow of air through the rotor provides
sufficient thrust to maintain rotor rpm throughout the descent.
Since the tail rotor is driven by the main rotor transmission
during autorotation, heading control is maintained with the
antitorque pedals as in normal flight
Several factors affect the rate of descent in autorotation:
density altitude, gross weight, rotor rpm, and airspeed. The
primary way to control the rate of descent is with airspeed.
Higher or lower airspeed is obtained with the cyclic pitch
control just as in normal powered flight. In theory, a pilot
has a choice in the angle of descent varying from a vertical
descent to maximum range,
producing lift and thrust from their angle of attack (AOA)
and velocity. By lowering the collective pitch, which must be
done immediately in case of an engine failure, lift and drag
are reduced, and the helicopter begins an immediate descent,
thus producing an upward flow of air through the rotor
system. This upward flow of air through the rotor provides
sufficient thrust to maintain rotor rpm throughout the descent.
Since the tail rotor is driven by the main rotor transmission
during autorotation, heading control is maintained with the
antitorque pedals as in normal flight
Several factors affect the rate of descent in autorotation:
density altitude, gross weight, rotor rpm, and airspeed. The
primary way to control the rate of descent is with airspeed.
Higher or lower airspeed is obtained with the cyclic pitch
control just as in normal powered flight. In theory, a pilot
has a choice in the angle of descent varying from a vertical
descent to maximum range,
Pilots should practice autorotations with varying airspeeds
between the minimum rate of descent to the maximum glide
angle airspeed. The decision to use the appropriate airspeed
for the conditions and availability of landing area must be
instinctive
between the minimum rate of descent to the maximum glide
angle airspeed. The decision to use the appropriate airspeed
for the conditions and availability of landing area must be
instinctive
Cyclic input has a great effect on the rotor rpm. An aft cyclic
input loads the rotor, resulting in coning and an increase in
rotor rpm. A forward cyclic input unloads the rotor, resulting
in a decrease in rotor rpm. Therefore, it is prudent to attain
the proper pitch attitude needed to ensure that the desired
landing area can be reached as soon as possible,
input loads the rotor, resulting in coning and an increase in
rotor rpm. A forward cyclic input unloads the rotor, resulting
in a decrease in rotor rpm. Therefore, it is prudent to attain
the proper pitch attitude needed to ensure that the desired
landing area can be reached as soon as possible,
I think I now know where you are coming from PG, you simply have to be more succinct about what you mean and how you post it [
].And no more silly remarks about the bleedin bloody obvious re Nr decay.
TC well done for downloading the FAA doc - I baulked at 20 mB and an .exe file!
Anyway, it is interesting:
By lowering the collective pitch, which must be
done immediately in case of an engine failure, lift and drag
are reduced, and the helicopter begins an immediate descent,
thus producing an upward flow of air through the rotor
system.
Note my different emboldening to yours. The statement is reasonably true when flying at modest speeds, or even flat out in a Bell 47! However it fails to take account that at high speed (by which I mean a modern heli doing 150 kts) the small pitch change that results from the collective being lowered has a huge impact on the g loading. Yes it makes the helicopter descend rapidly, but it does not produce an upward flow of air through the rotor system, at least in the short term.
So in fact that document is wrong, probably outdated from the days when helicopters max speed was not that high - the technique probably worked then.
You say to maintain the attitude, yes I can go with that, certainly better than just dumping the collective. But a slight pitch nose up will result in less reduction of Nr compared to maintaining the attitude. My point is that this last thing is the most critical, especially in a twin where double engine failures and the need suddenly and unexpectedly to have to enter auto is a much less than once in a lifetime event. There is a good chance of being stunned into inactivity for a moment.
First priority is to keep the rotor rpm in a flying range. If you fail at that first hurdle, you can forget a landing zone.
Yes, once that is in hand, the second and much lower priority is to choose a good landing site and try to make it. But if you get that bit right, but not the first priority, you are wasting what little remains of your life.
Put simply, flaring the aircraft slightly increases your chances of surviving the unexpected auto entry and that is all that matters. (all this of course from cruise flight)
Anyway, it is interesting:
By lowering the collective pitch, which must be
done immediately in case of an engine failure, lift and drag
are reduced, and the helicopter begins an immediate descent,
thus producing an upward flow of air through the rotor
system.
Note my different emboldening to yours. The statement is reasonably true when flying at modest speeds, or even flat out in a Bell 47! However it fails to take account that at high speed (by which I mean a modern heli doing 150 kts) the small pitch change that results from the collective being lowered has a huge impact on the g loading. Yes it makes the helicopter descend rapidly, but it does not produce an upward flow of air through the rotor system, at least in the short term.
So in fact that document is wrong, probably outdated from the days when helicopters max speed was not that high - the technique probably worked then.
You say to maintain the attitude, yes I can go with that, certainly better than just dumping
the collective. But a slight pitch nose up will result in less reduction of Nr compared to maintaining the attitude. My point is that this last thing is the most critical, especially in a twin where double engine failures and the need suddenly and unexpectedly to have to enter auto is a much less than once in a lifetime event. There is a good chance of being stunned into inactivity for a moment.First priority is to keep the rotor rpm in a flying range. If you fail at that first hurdle, you can forget a landing zone.
Yes, once that is in hand, the second and much lower priority is to choose a good landing site and try to make it. But if you get that bit right, but not the first priority, you are wasting what little remains of your life.
Put simply, flaring the aircraft slightly increases your chances of surviving the unexpected auto entry and that is all that matters. (all this of course from cruise flight)