Entering autos: discussion split from Glasgow crash thread
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Dear TC. On the understanding that the single engine helicopter pilot should always have their hand on the collective lever, there are going to be times when they do not for various good reasons. Should the pilot suffer an engine failure during one of these situations, then if their first action was to lower the lever they would most probably end up being a passenger until they hit the ground. It will take a period of time for the pilot to recognise and react and a further period of time to move their hand back onto the collective lever and lower it. However they will always have their hand on the cyclic, therefore able to trade airspeed for RRPM in a much shorter time scale, it has to make sense to use airspeed energy should you have it. The understanding is that this energy transfer is transient, the pilot is going to have to put that lever down, it just allows for a bit more time to do so. I would go so far as to say; ' it should be a criminal offence for a helicopter pilot not to try and use all available energy to prevent Low RPM rotor stall' DS.
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Good Grief! I have just come back after a trip away from the electric net and though I'd logged into just helicopters by mistake! Gents, there are an awful lot of quite respectable contributors to this site who appear to me, to be caught up in an never ending competition to be the 'most correct'. It's almost Christmas, why don't you all take a few days off, read what you have all actually written and come back after you have had a nice lie down!
Dick, I understand where you are coming from in your last post but consider an R22 at 80 kts with the pilot using his left hand to play with the GPS for example: the engine fails and he, having read your post, immediately flares the aircraft without lowering the lever (considering it a secondary action as he has some forward speed to trade for Nr) - the speed washes off quickly, he then gets round to lowering the lever and his next action will be to push the stick forward to prevent further speed decay - this reduces +g below 1 and the combination of forward cyclic, low Nr and reduced g causes mast bumping and MR blade strike to the fuselage - game over!
Yes, use both hands if necessary to retain/recover Nr but don't promote cyclic flare over lowering the lever - it is only valid in certain circumstances and in many others can be disastrous.
Anyone actually brave enough to try a throttle chop in the 90 kt cruise in a Robbie and delay lowering the lever because you can flare a bit? Thought not
Yes, use both hands if necessary to retain/recover Nr but don't promote cyclic flare over lowering the lever - it is only valid in certain circumstances and in many others can be disastrous.
Anyone actually brave enough to try a throttle chop in the 90 kt cruise in a Robbie and delay lowering the lever because you can flare a bit? Thought not
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Grenville
After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight.
A lot of other stuff happening will mask this however like the yaw.
And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)
And for interest my opinion is that a one size fits all is stupid for entering autorotation. Entry should be tailored to the circumstances. There are some basics to get you started (fly the aircraft, maintain NR, make a plan and follow it, get the gear down if appropriate, say something funny for the CVR) but slavishly following advice in the face of different circumstances could get you killed. AVIATE!
After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight.
A lot of other stuff happening will mask this however like the yaw.
And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)
And for interest my opinion is that a one size fits all is stupid for entering autorotation. Entry should be tailored to the circumstances. There are some basics to get you started (fly the aircraft, maintain NR, make a plan and follow it, get the gear down if appropriate, say something funny for the CVR) but slavishly following advice in the face of different circumstances could get you killed. AVIATE!
GM - or the retreating side would stall and cause pitch up and roll towards the retreating side.
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After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight.
A lot of other stuff happening will mask this however like the yaw.
And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)
A lot of other stuff happening will mask this however like the yaw.
And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)
Therefore I suggest that if one is in the cruise flying manually the instinctive response will be to "level" the aircraft (ie. apply aft cyclic), followed by a reduction in collective.
What I am interested to know is what are the current procedures for a two crew response to a double engine failure.
Flying the early twins single pilot you had to decide fairly quickly which engine had failed in a loss of power scenario, in a two crew environment responsibilities can be shared between flying the aircraft and confirming instrument readings.
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Again pilot should be flying the aircraft. Co pilot does the drills. The input on engine failure is irrelavent. You just need to do what is required to keep the aircraft attitude where you want it. Look out or in IMC at the instruments and FLY. You cannot fly by rote.
UNDER ALL CIRCUMSTANCES (no exception whatsoever) - LOWER THE COLLECTIVE FIRST IN THE EVENT OF A TOTAL ENGINE(S) FAILURE.
TC,
While I agree with much of what you write, are you really advocating lowering the lever when in a low hover or hover-taxi (ie 5' or so for a single)? I always understood the correct actions to be to maintain lever position until it was time to cushion (at which point the lever goes up not down!). This has certainly been practised many times over many years with successful results. Is this not a significant exception to your rule?
TOTD
Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.
Exactly how many Dual Engine failures have ever occurred on the North Sea?
Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.
it was also not representative of an actual simultaneous Dual Engine Failure.
Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!
Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused?
Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.
How long can you maintain a Zero G condition? Seconds or Minutes?
So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.
Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.
Exactly how many Dual Engine failures have ever occurred on the North Sea?
Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.
it was also not representative of an actual simultaneous Dual Engine Failure.
Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!
Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused?
Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.
How long can you maintain a Zero G condition? Seconds or Minutes?
So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.
Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.
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Crab. You do not need to bleed off a great deal of airspeed at 80kts to gain a lot of RRPM (energy). You can see the effect quite well in an R22' if you switch the gov off, reduce the RPM to 95% at 80kts and just apply aft cyclic. The RPM increases quickly and by a good amount, however it is transient and will decay again. Not scary and useful to see. No need for large cyclic inputs, no low 'g' no need to be dramatic. DS
Dick, I agree - in a benign, pre-briefed and planned scenario and with a steady Nr. From a no-notice engine failure with rapidly decaying Nr I suspect things would go more as I suggested, especially without an experienced pilot at the helm.
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Crab. I have had an engine failure in an R22. As it happens I was at 80 kts. The application of aft cyclic worked a treat, entry into auto un dramatic, did not need to increase IAS for my 65 kt auto IAS. No low 'g' I'm still here ( sort of). DS
Gipsey: You have already confused the abbo's and newbies with your incorrect disc response description (Grenville for one). Crab got to you before I did 
Which now means someone like me/crab/RotorIP/SAS/ eta l have to come back on here wasting our time re-iterating what has been siad time and time and time again.
Once more mon amie (and because there is either misunderstanding or confusion with all these suggestions on entering auto):
ALWAYS ALWAYS ALWAYS LOWER COLLECTIVE FIRST - you will never ever go wrong. It is a "slavish" statement. It is a "rote" technique but it is.....wait for it...... TRUE Trust me when I say that in every single alternative view thrown at this thread, be it whatever reason or excuse, there is always an alternative to positioning the cyclic during entry to an auto, there is also time to positioning the cyclic too.
There is NO alternative to selcting down collective and so very little time.
Which brings me onto Dick Sanford. [Hello Dick, we have met professionally - you came and did a safety audit for me on my police air wing many years ago???].
Dick - I'm not 100% certain of this, but I believe you were not military? It is burned into the mind of every single mil pilot in the UK (especially) to be milli seconds away from the collective at any one time. Mil pilots have no truc with anyone who use their hands to wander around the cockpit. (a) there are NO circumstances to leave the collective unattended for more than a couple of seconds and only then to even contemplate taking your hands off the lever is seen as a cardinal sin.
Same goes for cyclic but to a lesser degree. Complex systems in complex cockpits invariably find themselves being manned by two pilots. Less complicated cockpits with one pilot (like the SPIFR EC135) are designed to minimise dextrous demands in the office - I might suggest.
Which now means someone like me/crab/RotorIP/SAS/ eta l have to come back on here wasting our time re-iterating what has been siad time and time and time again.
Once more mon amie (and because there is either misunderstanding or confusion with all these suggestions on entering auto):
ALWAYS ALWAYS ALWAYS LOWER COLLECTIVE FIRST - you will never ever go wrong. It is a "slavish" statement. It is a "rote" technique but it is.....wait for it...... TRUE Trust me when I say that in every single alternative view thrown at this thread, be it whatever reason or excuse, there is always an alternative to positioning the cyclic during entry to an auto, there is also time to positioning the cyclic too.
There is NO alternative to selcting down collective and so very little time.
Which brings me onto Dick Sanford. [Hello Dick, we have met professionally - you came and did a safety audit for me on my police air wing many years ago???].
Dick - I'm not 100% certain of this, but I believe you were not military? It is burned into the mind of every single mil pilot in the UK (especially) to be milli seconds away from the collective at any one time. Mil pilots have no truc with anyone who use their hands to wander around the cockpit. (a) there are NO circumstances to leave the collective unattended for more than a couple of seconds and only then to even contemplate taking your hands off the lever is seen as a cardinal sin.
Same goes for cyclic but to a lesser degree. Complex systems in complex cockpits invariably find themselves being manned by two pilots. Less complicated cockpits with one pilot (like the SPIFR EC135) are designed to minimise dextrous demands in the office - I might suggest.
Getting messy, too many colours!
I in green now
Originally Posted by HeliComparator
Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.
Exactly how many Dual Engine failures have ever occurred on the North Sea? One that I can think of, another one where the failures were not simultaneous. If you are trying to say that it's rare and improbable then I quite agree, but nevertheless this is the circumstance we are considering.
Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.
it was also not representative of an actual simultaneous Dual Engine Failure. Correct, with an actual simultaneous dual engine failure the Nr would likely be pretty low before the collective was lowered due to pilot reaction time.
Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!
Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused? Of course when the g came on, the increase in rpm is exactly what is needed. But the problem is that the effect is delayed by have low g for the first few moments of the recovery into auto. The pilot's inevitable delay in entering auto is bad enough and will quite probably result in the Nr getting perilously low. Add to that a pilot reaction that does not initially get an autorotative flow going, ie one that allows further Nr reduction after the recovery is initiated, and it could lead to the Nr becoming unrecoverably low. Let's also remember that the issue is blade stall, so if there is a period of zero g, lowering Nr, then aft cyclic is applied (with a bit of reaction time) to correct zero g, initially a poor response to the cyclic due to low g, then as the g starts to come on the cyclic really "bites" and well over 1g is produced. Whilst this would normally be a "good thing" as you say, to restore the Nr, in fact low Nr + high disc loading = increased propensity to stall, so those actions might make the unrecoverable Nr somewhat higher than it might otherwise be. Even if the blades don't stall, whilst you might get the Nr back you will get more than you bargained for as the Nr shoots way over the max transient Nr. If you are used to flying metal bladed helicopters, you will be amazed at how fast the Nr can rise on a plastic bladed helicopter under g loading.
Set against all that is leading with the cyclic to maintain 1g, and it all goes swimmingly well!
Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.
How long can you maintain a Zero G condition? Seconds or Minutes?
I suppose if you really tried and didn't care about recovery, you could put the heli into a ballistic dive and hold zero g for as long as the heli could stand the speed increase. You would end up in a vertical dive but I suppose would run out of fwd cyclic fairly quickly if nothing else gave way.
But practically speaking I am only talking about a few seconds. Any Nr loss greater than that arising from pilot reaction time is to be avoided, maintaining 1g+ (for which you have to lead with the cyclic) minimises that. Just lowering the collective makes it a whole lot worse.
So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.
Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.
Perhaps "messy" actually describes a situation where transient effects were causing variations in the Rotor RPM which would only be "normal" considering the loss of drive from the Engines, the shift from the Rotors being driven by the engines to an autorotative descent, shifting airspeeds and aircraft attitudes, and change in Tail Rotor Torque demand?
I in green now
Originally Posted by HeliComparator
Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.
Exactly how many Dual Engine failures have ever occurred on the North Sea? One that I can think of, another one where the failures were not simultaneous. If you are trying to say that it's rare and improbable then I quite agree, but nevertheless this is the circumstance we are considering.
Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.
it was also not representative of an actual simultaneous Dual Engine Failure. Correct, with an actual simultaneous dual engine failure the Nr would likely be pretty low before the collective was lowered due to pilot reaction time.
Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!
Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused? Of course when the g came on, the increase in rpm is exactly what is needed. But the problem is that the effect is delayed by have low g for the first few moments of the recovery into auto. The pilot's inevitable delay in entering auto is bad enough and will quite probably result in the Nr getting perilously low. Add to that a pilot reaction that does not initially get an autorotative flow going, ie one that allows further Nr reduction after the recovery is initiated, and it could lead to the Nr becoming unrecoverably low. Let's also remember that the issue is blade stall, so if there is a period of zero g, lowering Nr, then aft cyclic is applied (with a bit of reaction time) to correct zero g, initially a poor response to the cyclic due to low g, then as the g starts to come on the cyclic really "bites" and well over 1g is produced. Whilst this would normally be a "good thing" as you say, to restore the Nr, in fact low Nr + high disc loading = increased propensity to stall, so those actions might make the unrecoverable Nr somewhat higher than it might otherwise be. Even if the blades don't stall, whilst you might get the Nr back you will get more than you bargained for as the Nr shoots way over the max transient Nr. If you are used to flying metal bladed helicopters, you will be amazed at how fast the Nr can rise on a plastic bladed helicopter under g loading.
Set against all that is leading with the cyclic to maintain 1g, and it all goes swimmingly well!
Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.
How long can you maintain a Zero G condition? Seconds or Minutes?
I suppose if you really tried and didn't care about recovery, you could put the heli into a ballistic dive and hold zero g for as long as the heli could stand the speed increase. You would end up in a vertical dive but I suppose would run out of fwd cyclic fairly quickly if nothing else gave way.
But practically speaking I am only talking about a few seconds. Any Nr loss greater than that arising from pilot reaction time is to be avoided, maintaining 1g+ (for which you have to lead with the cyclic) minimises that. Just lowering the collective makes it a whole lot worse.
So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.
Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.
Perhaps "messy" actually describes a situation where transient effects were causing variations in the Rotor RPM which would only be "normal" considering the loss of drive from the Engines, the shift from the Rotors being driven by the engines to an autorotative descent, shifting airspeeds and aircraft attitudes, and change in Tail Rotor Torque demand?
TOTD: well spotted and congrats on spotting that (unless you have been speaking to Crab earlier who commented the same elsewhere).
This is indeed an area which requires careful deliberation (on the ground before it goes per shaped for real) regarding a response from the pilot.
I think it was mentioned by a previous poster that each a/c is different when it comes to its characteristics during an engine failure.
I could write a book on donks stopping because of this but I have got to go and watch paint drying shortly so I won't...but in brief:
"generally" if the donk stops @ 5 ' taxiing or in the hover, you will probably hit the deck before you know what the f*ck has happened. Any higher and an element of check down on the collective is fed into the equation to reduce the amount of decaying Nr such that the final raising of lever to absorb the landing is less exciting to bystanders. From 30-40 feet and higher, almost all helos will require a slight check down on collective to slug the decaying Nr before the big armpit up movement of collective. In all situations, you will be pleased to note that no aft cyclic was used in the making of any of these simulations
This is indeed an area which requires careful deliberation (on the ground before it goes per shaped for real) regarding a response from the pilot.
I think it was mentioned by a previous poster that each a/c is different when it comes to its characteristics during an engine failure.
I could write a book on donks stopping because of this but I have got to go and watch paint drying shortly so I won't...but in brief:
"generally" if the donk stops @ 5 ' taxiing or in the hover, you will probably hit the deck before you know what the f*ck has happened. Any higher and an element of check down on the collective is fed into the equation to reduce the amount of decaying Nr such that the final raising of lever to absorb the landing is less exciting to bystanders. From 30-40 feet and higher, almost all helos will require a slight check down on collective to slug the decaying Nr before the big armpit up movement of collective. In all situations, you will be pleased to note that no aft cyclic was used in the making of any of these simulations