Entering autos: discussion split from Glasgow crash thread
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Fortyodd2
For differing reasons, neither of those are likely to require a "large application of rudder" by the pilot.
For fixed wing pilots 'dipping in' to this conversation I will just reinforce where the similarities, and where the diffences lie.
In a fixed wing, airspeed is the thing that will keep you alive. Lack of it will kill you. In a helicopter, airspeed is usually considered largely irrelevant, it's Rotor RPM that keeps you alive.
Have a power disturbance in a FW and the pilots eyes are likely to be glued to the airspeed indicator (speed tape?) Have a power deficit in a RW and the pilot will be concentrating on rotor rpm above everything else. Even identifying a suitable forced landing site cannot override that.
Apart from a fairly large application of rudder, I cannot image that the drills you would have used on the A320 suffering an engine failure at FL 300 & 500Kts would be the same as those in a Dakota on a half mile final.
For fixed wing pilots 'dipping in' to this conversation I will just reinforce where the similarities, and where the diffences lie.
In a fixed wing, airspeed is the thing that will keep you alive. Lack of it will kill you. In a helicopter, airspeed is usually considered largely irrelevant, it's Rotor RPM that keeps you alive.
Have a power disturbance in a FW and the pilots eyes are likely to be glued to the airspeed indicator (speed tape?) Have a power deficit in a RW and the pilot will be concentrating on rotor rpm above everything else. Even identifying a suitable forced landing site cannot override that.
Last edited by Tandemrotor; 13th Dec 2013 at 12:32.
Avoid imitations
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Tandem, well put.
Baston,
I'm 100% certain that the Queen did not allow her twin engined helicopters to be EOL'd to the ground. That was reserved for single engined aircraft only, at least since the 1970s when I was trained by the RAF. The reasons should be obvious.
The only time it was allowed on twin engined helicopters was for test pilots carrying out a trial. Even then, almost two decades after the aircraft came into service, during ideal and pre-planned circumstances over the very lengthy Boscombe Down runway, they managed to bend the one (Puma) they were allowed to EOL all the way to the ground. We (the OCU) had already come up with total engine failure/EOL drills and tail rotor malfunction drills in the simulator. At least one crew said after a tail rotor pitch spider failure over the sea that the training we provided saved their lives. Had they not been privy to it, the pilot said he would have possibly shut down the engines which was the incorrect thing to do in his case.
The most important thing on any helicopter to practice is the recognition and recovery from total power failure followed by a successful autorotation. Without that the chances of a successful landing are very poor indeed.
The chances of minor damage to an expensive helicopter on landing during an EOL are relatively high. Any minor damage would mean the job stops because we don't another aircraft in reserve, nor would the insurance companies allow us to train in that way.
Fixed wing jet pilots would throw up their hands in horror if it were suggested that they be required to carry out true engines off (deadstick) landings in the actual jet airframe for training purposes. Same thing.
So simulators are used, that's the whole point of them. However, beware of taking the handling responses to be as per the real helicopter in all extreme circumstances. What happens (i.e. what is programmed in the software) is based on a a "best guess" (off model) scenario because no-one has obtained real data from the aircraft, again for what should be obvious reasons.
Baston,
All those of us who were lucky enough to train doing real engine offs from all stages of flight were very lucky as the Queen did not worry about "£6 million" aircraft as the crews were and are more valuable. At the end of the day if you end up sitting in a field in your seat surrounded by a few tons of scrap aluminium - so be it - you have survived and can let the engineers worry from then on.
The only time it was allowed on twin engined helicopters was for test pilots carrying out a trial. Even then, almost two decades after the aircraft came into service, during ideal and pre-planned circumstances over the very lengthy Boscombe Down runway, they managed to bend the one (Puma) they were allowed to EOL all the way to the ground. We (the OCU) had already come up with total engine failure/EOL drills and tail rotor malfunction drills in the simulator. At least one crew said after a tail rotor pitch spider failure over the sea that the training we provided saved their lives. Had they not been privy to it, the pilot said he would have possibly shut down the engines which was the incorrect thing to do in his case.
The most important thing on any helicopter to practice is the recognition and recovery from total power failure followed by a successful autorotation. Without that the chances of a successful landing are very poor indeed.
The chances of minor damage to an expensive helicopter on landing during an EOL are relatively high. Any minor damage would mean the job stops because we don't another aircraft in reserve, nor would the insurance companies allow us to train in that way.
Fixed wing jet pilots would throw up their hands in horror if it were suggested that they be required to carry out true engines off (deadstick) landings in the actual jet airframe for training purposes. Same thing.
So simulators are used, that's the whole point of them. However, beware of taking the handling responses to be as per the real helicopter in all extreme circumstances. What happens (i.e. what is programmed in the software) is based on a a "best guess" (off model) scenario because no-one has obtained real data from the aircraft, again for what should be obvious reasons.
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Savoia - having had three 206 engine failures, one at night with the Alton Towers L, that scenario seems very familiar! Two were compressor blades flying out of the side, and the night one turned out to be the NR gauge, but having set myself up and fired off a flare, I just carried on. Good job I did, because at the end of the field was a set of large tower lines which we discovered the next morning. No damage to anything aside from the initial cause.
I can confirm that the aircraft behaves very differently in the real world, and the denial factor is very relevant - i.e. "this isn't fair, all my engine offs have been over large green fields!" By the time you have sorted that out you are already on your way down, and if you are longlining you are likely on the ground. With twins, this is even more critical, as you have to watch the needles more to detect a failure in the first place, and the idea is to keep it flying, so dumping the pole is less on your mind. I did my 355 conversion before I did my 350, and it was very beneficial to do EOLs in a very similar type, but this is not the case for modern aircraft.
My first priority is to DUMP THE POLE because you don't want any drag from the blades, with maybe a slight check back in the hover or a bigger one at higher speeds. Some people have indicated that they would keep a high speed on - not sure that's a good idea, as if you are over the VNE for autorotation all you will do is go down faster as the driving area of the disk will go past the tip path plane, giving you less disk area to play with.
Phil
I can confirm that the aircraft behaves very differently in the real world, and the denial factor is very relevant - i.e. "this isn't fair, all my engine offs have been over large green fields!" By the time you have sorted that out you are already on your way down, and if you are longlining you are likely on the ground. With twins, this is even more critical, as you have to watch the needles more to detect a failure in the first place, and the idea is to keep it flying, so dumping the pole is less on your mind. I did my 355 conversion before I did my 350, and it was very beneficial to do EOLs in a very similar type, but this is not the case for modern aircraft.
My first priority is to DUMP THE POLE because you don't want any drag from the blades, with maybe a slight check back in the hover or a bigger one at higher speeds. Some people have indicated that they would keep a high speed on - not sure that's a good idea, as if you are over the VNE for autorotation all you will do is go down faster as the driving area of the disk will go past the tip path plane, giving you less disk area to play with.
Phil
Shy,
My Uncle Sam drew no such distinction between singles and multi's....as i did EOL's in TH-55's, Huey's, and Chinooks. Granted, far fewer in the Chinook as EOL's were not seen to be as likely to be needed.
EOL's in civilian Helicopters are a subject that has many sides to it.
Insurance companies are all about limiting risks to their purse.
CEO's also look to maximizing the "Bottom Line".
That is why we do not do EOL's.
The next best thing is to do power recovery type EOL approaches to landing and hope that we get the Entry done right and control the descent and final stages prior to Touch Down in a proper manner.
If we arrive close to the ground in good shape, with bags of Rotor RPM, a proper pitch attitude and ground speed over a suitable site for landing.....then the odds are we shall survive the landing.
That applies to singles or twins.....and to Simulators as well.
We have to remember Simulators are not the same thing as real aircraft and can only fairly well duplicate the actual aircraft but not perfectly.
Sim's teach procedures and systems not aircraft handling per se.
My Uncle Sam drew no such distinction between singles and multi's....as i did EOL's in TH-55's, Huey's, and Chinooks. Granted, far fewer in the Chinook as EOL's were not seen to be as likely to be needed.
EOL's in civilian Helicopters are a subject that has many sides to it.
Insurance companies are all about limiting risks to their purse.
CEO's also look to maximizing the "Bottom Line".
That is why we do not do EOL's.
The next best thing is to do power recovery type EOL approaches to landing and hope that we get the Entry done right and control the descent and final stages prior to Touch Down in a proper manner.
If we arrive close to the ground in good shape, with bags of Rotor RPM, a proper pitch attitude and ground speed over a suitable site for landing.....then the odds are we shall survive the landing.
That applies to singles or twins.....and to Simulators as well.
We have to remember Simulators are not the same thing as real aircraft and can only fairly well duplicate the actual aircraft but not perfectly.
Sim's teach procedures and systems not aircraft handling per se.
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BasTon and SAS,
If, during forward flight the engine(s) stops, my experience has been that we react only after the NR has decayed. The ONLY way to get it back is to flare. Lowering the lever in any helicopter will not bring the NR back,
Of course eventually the lever has to be lowered otherwise autorotative state will never be achieved.
I agree with you both. One size never fits all. However my post is about recovering lost NR, which lets be honest, is the most likely scenario in ANY total power loss event. If in the hover, in certain types, there is not a lot of hope. In others, as I explained in our 500 foot 206 throttle chop exercise, they fare much better.
However, training is about forming good habits, that will serve you well, when tired, things have gone wrong and you need a friend. This is the core relevance of Peters "Cyclic Back" approach and just maybe a feature in this accident.
NR responds to disc loading and that is what the cyclic flare does.
For the poster advocating the maintainable of "Attitude" .....well in effect that is a mild flare as the nose tries to drop. However, tired, in the dark, un expecting, it is likely you will need more than that. There is real value in Peters post and its about habit, once the power loss is recognised.
In a modern helicopter stinking along at 145 KIAS, very little speed needs to be traded for a significant gain in NR, this is utterly basic stuff BUT experience, time and time again shows that pilots simply do not react thus way. They know it, but they respond too late because it is not fully instinctive.
In the hover, I think we all adopt a more attentive attitude to a possible power loss. Especially at height. In Police Operations in UK this is substantially mitigated by the presence of the second engine. However, should we lose both engines in the hover our response has to be instantaneous as we do not have the most powerful tool for recovering our NR........AIRSPEED. Of course in the hover the lever has to dumped...fully....and completely....to the floor plate or its ENDEX. From this point onwards, lever fully down, it's a lottery based on remaining NR, height and control, and of course the characteristics of the individual type.
I think Peters post adds value to this subject more than most poster are inclined to believe. Airspeed is the most powerful energy store we may, or may not have at the point the engine(s) fail. The less we have, and the more decayed the rotor, the slimmer our chances of recovery. It's as simple as that.
DB
If, during forward flight the engine(s) stops, my experience has been that we react only after the NR has decayed. The ONLY way to get it back is to flare. Lowering the lever in any helicopter will not bring the NR back,
Of course eventually the lever has to be lowered otherwise autorotative state will never be achieved.
I agree with you both. One size never fits all. However my post is about recovering lost NR, which lets be honest, is the most likely scenario in ANY total power loss event. If in the hover, in certain types, there is not a lot of hope. In others, as I explained in our 500 foot 206 throttle chop exercise, they fare much better.
However, training is about forming good habits, that will serve you well, when tired, things have gone wrong and you need a friend. This is the core relevance of Peters "Cyclic Back" approach and just maybe a feature in this accident.
NR responds to disc loading and that is what the cyclic flare does.
For the poster advocating the maintainable of "Attitude" .....well in effect that is a mild flare as the nose tries to drop. However, tired, in the dark, un expecting, it is likely you will need more than that. There is real value in Peters post and its about habit, once the power loss is recognised.
In a modern helicopter stinking along at 145 KIAS, very little speed needs to be traded for a significant gain in NR, this is utterly basic stuff BUT experience, time and time again shows that pilots simply do not react thus way. They know it, but they respond too late because it is not fully instinctive.
In the hover, I think we all adopt a more attentive attitude to a possible power loss. Especially at height. In Police Operations in UK this is substantially mitigated by the presence of the second engine. However, should we lose both engines in the hover our response has to be instantaneous as we do not have the most powerful tool for recovering our NR........AIRSPEED. Of course in the hover the lever has to dumped...fully....and completely....to the floor plate or its ENDEX. From this point onwards, lever fully down, it's a lottery based on remaining NR, height and control, and of course the characteristics of the individual type.
I think Peters post adds value to this subject more than most poster are inclined to believe. Airspeed is the most powerful energy store we may, or may not have at the point the engine(s) fail. The less we have, and the more decayed the rotor, the slimmer our chances of recovery. It's as simple as that.
DB
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I've never had an engine failure in a single, but I've had 3 double engine failures in twins. Luckily all of them were by day and I was not flying over built-up areas or particularly hostile terrain. All were in older aircraft with relatively low cruise speeds by today's standards (90 - 110 its). In 2 instances I was IMC at the time of engine failure. In all 3 cases I simultaneously applied enough aft cyclic to stop the nose from dropping and Nr from decaying and lowered the lever to enter autorotation. I don't seem to remember losing very much height at all during entry to auto and (once VMC) I was able to decide what sort of auto I wished to do to and was luckily enough to land the aircraft and myself undamaged.
For many years, and well before the days of simulators in which to practice these things, I was asked by students why I always insisted on doing autorotations when flying a twin as the possibility of a double engine failure was so remote as to to be discounted :roll eyes:.
In later years I often used to practice engine off landings (or touch-down autos as our trans-Atlantic brothers often call them) in a variety of twins such as the Bell 212 and the Twin Squirrel (as I found it little different from doing them in the single Squirrel
).
I was lucky and have survived my career in aviation to beyond my best-before date so far despite my lack of co-ordination and skills (or so my basic rotary instructor always told me
), but some days no matter how lucky or skilled the pilot he (or she) may just find that the grim reaper has just come calling.
For many years, and well before the days of simulators in which to practice these things, I was asked by students why I always insisted on doing autorotations when flying a twin as the possibility of a double engine failure was so remote as to to be discounted :roll eyes:.
In later years I often used to practice engine off landings (or touch-down autos as our trans-Atlantic brothers often call them) in a variety of twins such as the Bell 212 and the Twin Squirrel (as I found it little different from doing them in the single Squirrel
). I was lucky and have survived my career in aviation to beyond my best-before date so far despite my lack of co-ordination and skills (or so my basic rotary instructor always told me
), but some days no matter how lucky or skilled the pilot he (or she) may just find that the grim reaper has just come calling.
Last edited by soggyboxers; 13th Dec 2013 at 18:48.
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Sorry for being late into this discussion - been away doing FW sim data gathering.
For those who don't know Pete Gillies - he's an exceptionally experienced helicopter pilot and instructor, and his knowledge on autorotations is based on years of observation and experience. And a gentleman to boot.
He knows whereof he speaks.
For those who don't know Pete Gillies - he's an exceptionally experienced helicopter pilot and instructor, and his knowledge on autorotations is based on years of observation and experience. And a gentleman to boot.
He knows whereof he speaks.
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Helicopter energy
These discussions of how to best deal with a loss of power are interesting.
I suggest the reason for what seem to be substantial differences of opinion simply reflect that helicopters are more complex than fixed wing aircraft.
In a fixed wing aircraft, you can trade speed for height, adjust attitude, alter power, and perhaps deploy devices to vary lift and drag (not all independent), and that's about all.
In a helicopter, there's an additional energy store in the rotor to take into account, and a wider range of relative wind values can be experienced, vertically and in azimuth. The lift/drag on the rotor can be changed quickly, with attitude changing in response. There's a significant gyroscopic effect too, restricting acceleration and attitude.
With a three-ton helicopter, the kinetic energy in a 10-m diameter, 200-kg rotor at 200rpm (~2MJ), scales with rpm-squared and matches the kinetic energy for a forward speed v~75 knots and the potential energy gained from dropping h~200 feet. The important energy quantities involved in this case are all comparable in size, and the best way to trade them can clearly be debated.
A very plausible answer seems to require "it depends". The importance of maintaining a store of energy in the rotor is clear, but there are different ways to achieve that: exchanging height, forward speed, or by reducing rotor drag.
I suggest the reason for what seem to be substantial differences of opinion simply reflect that helicopters are more complex than fixed wing aircraft.
In a fixed wing aircraft, you can trade speed for height, adjust attitude, alter power, and perhaps deploy devices to vary lift and drag (not all independent), and that's about all.
In a helicopter, there's an additional energy store in the rotor to take into account, and a wider range of relative wind values can be experienced, vertically and in azimuth. The lift/drag on the rotor can be changed quickly, with attitude changing in response. There's a significant gyroscopic effect too, restricting acceleration and attitude.
With a three-ton helicopter, the kinetic energy in a 10-m diameter, 200-kg rotor at 200rpm (~2MJ), scales with rpm-squared and matches the kinetic energy for a forward speed v~75 knots and the potential energy gained from dropping h~200 feet. The important energy quantities involved in this case are all comparable in size, and the best way to trade them can clearly be debated.
A very plausible answer seems to require "it depends". The importance of maintaining a store of energy in the rotor is clear, but there are different ways to achieve that: exchanging height, forward speed, or by reducing rotor drag.
Originally Posted by soggyboxers
I've never had an engine failure in a single, but I've had 3 engine failures in twins.
Having had three 206 engine failures, one at night with the Alton Towers L, that scenario seems very familiar! Two were compressor blades flying out of the side, and the night one turned out to be the NR gauge, but having set myself up and fired off a flare, I just carried on. Good job I did, because at the end of the field was a set of large tower lines which we discovered the next morning. No damage to anything aside from the initial cause.
For those unfamiliar with the Towers operation, John Broome (the original developer of Alton Towers) was pretty much a workaholic and in the winter months there was little hope of arriving back at Tilston Hall (John's residence) before dark. The Colonel had the Schermuly flares fitted to the craft and had begun discussing the need to upgrade the operation to a twin. Eventually a Bell 222 was bought but this was some years after the Colonel's departure.
I had always wanted to fire-off one of those flares but .. the Colonel would have none of it. Was it of help during your forced landing? Have never seen one in operation.
Soggy: Bravo amico! Presumably you were flying those 'early twins' with insufficient power to remain aloft?
Ah yes the TwinEcureuil, in a practice (throttles to idle) engine-off landing. Especially with high skid gear. One must be on ones toes!
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My memories of auto-rotating a Whirlwind on the short pre-Harrier course at Shawbury have well faded, so could someone (patiently) explain the aerodynamics whereby it has been said that a stalled rotor disc could bring itself to a standstill? Surely even stalled there is still a rotational force on the blades which would keep the disc turning if air is passing through the disc (ie heli falling)? AAIB were, it seems, presumably deliberate in stating that neither main or tail rotors were rotating at impact, which is a concept I find hard to grasp.
Normal autorotation, lift vector is inclined slightly forward (relative to the blade) so it pulls the rotors round and has enough oomph to overcome the gearbox frictional losses, oil & hydraulic pumps, tail rotor drive etc. this all despite a significant positive pitch remaining on the blades with the lever fully down.
If the angle of attack (being dependant on the blade pitch angle, vertical speed and the forward speed ie rpm) exceeds the critical value, then the blade stalls. Now the lift vector is much smaller but also inclined well aft (relative to the blade), so as to drag the blades and make them slow rapidly. The increased rate of descent increases the angle of attack, as does the slowing. Unlike a FW you can't just pitch the nose down to recover because the blades are pointing in all directions.
If the angle of attack (being dependant on the blade pitch angle, vertical speed and the forward speed ie rpm) exceeds the critical value, then the blade stalls. Now the lift vector is much smaller but also inclined well aft (relative to the blade), so as to drag the blades and make them slow rapidly. The increased rate of descent increases the angle of attack, as does the slowing. Unlike a FW you can't just pitch the nose down to recover because the blades are pointing in all directions.
My memories of auto-rotating a Whirlwind on the short pre-Harrier course at Shawbury have well faded, so could someone (patiently) explain the aerodynamics whereby it has been said that a stalled rotor disc could bring itself to a standstill? Surely even stalled there is still a rotational force on the blades which would keep the disc turning if air is passing through the disc (ie heli falling)? AAIB were, it seems, presumably deliberate in stating that neither main or tail rotors were rotating at impact, which is a concept I find hard to grasp.
In the meantime .. take a look at this, from 18:50 onwards:
Hopefully someone will pipe-up with an aerodynamics explanation of the physiscs behind why, if you allow Nr to decay too far below the bottom of the green, it becomes unrecoverable.
Not that this applies to modern craft but .. in some of the early helicopter prototypes the blades actually 'snapped-off' when the Nr decay became excessive.
As far as my awareness of 'modern' craft is concerned, what I understand is that the 'driving' portion of the blade used in autorotation is simply incapable of recovering the lost inertia of a 'stalled' or sufficiently slowed rotor and, even it it were, the airflow over the blades would have to be 'just so' in order to get them rotating again and which positioning of the airframe relative to the desired airflow would be impossible to control in a 'free-falling' aircraft.
Just a numbered other
Apologies TC, just one more.
Indeed Bast0n, I remember well my one and only complete EOL in a Wessex 5 when you heaved both speed selects on me.
Not sure the Queen agreed with your methods though
Indeed Bast0n, I remember well my one and only complete EOL in a Wessex 5 when you heaved both speed selects on me.
Not sure the Queen agreed with your methods though
Now we are getting somewhere with excellent posts from Savoia and Paco. Other very experienced helo drivers are also in agreement with the statement:
At an EOL entry gate, the mantra should be to lower collective first to prevent Nr from decaying further and adjust cyclic second to maintain attitude.
If this tactic became second nature, it would serve you well, time and time again.
NOW: A more experienced pilot (and I'm sure most pilots think they are more experienced
) will have either been taught or at least shown the spectrum of entry gates so that they will have covered nearly all eventualities.
And this means engine(s) failure from 50 feet/high speed right across to a high hover. The former will demand that the collective should be lowered at the same time as the cyclic selected aft. The hover will demand collective ONLY and NO cyclic aft whatsoever. So we have a sliding scale of cyclic position ARE WE ALL AGREED? the message I am making is that Mr Gillies or whatever - shouldn't go around preaching to the NON converted (ab initio's) that
first - is the way to go. Because here, he is categorically and utterly wrong. He is also wrong when he believes that this is the best kept secret (what is all that bollox all about?????).
I have been privileged in my early training to have been taught by the finest military Instructors in the UK. (Tri Service)CAT A1 Instructors. I went on to become an A2 Instructor and flew single engine a/c for many thousands of hours. I have carried out several hundred EOL's to the deck. I have even carried out EOL's in Sea Kings before that evolution was deemed too expensive by HM!! I know what it is like to 'lose' an engine in every conceivable configuration known to man
And I know (a) There are no secret's in aviation - people have died discovering them all. (b) ALL EOL's without exception require the pilot to THINK collective first and cyclic second. The choice after that is yours based on the flight mode you are in.
At an EOL entry gate, the mantra should be to lower collective first to prevent Nr from decaying further and adjust cyclic second to maintain attitude.
If this tactic became second nature, it would serve you well, time and time again.
NOW: A more experienced pilot (and I'm sure most pilots think they are more experienced
) will have either been taught or at least shown the spectrum of entry gates so that they will have covered nearly all eventualities.And this means engine(s) failure from 50 feet/high speed right across to a high hover. The former will demand that the collective should be lowered at the same time as the cyclic selected aft. The hover will demand collective ONLY and NO cyclic aft whatsoever. So we have a sliding scale of cyclic position ARE WE ALL AGREED? the message I am making is that Mr Gillies or whatever - shouldn't go around preaching to the NON converted (ab initio's) that
AFT CYCLIC
I have been privileged in my early training to have been taught by the finest military Instructors in the UK. (Tri Service)CAT A1 Instructors. I went on to become an A2 Instructor and flew single engine a/c for many thousands of hours. I have carried out several hundred EOL's to the deck. I have even carried out EOL's in Sea Kings before that evolution was deemed too expensive by HM!! I know what it is like to 'lose' an engine in every conceivable configuration known to man
And I know (a) There are no secret's in aviation - people have died discovering them all. (b) ALL EOL's without exception require the pilot to THINK collective first and cyclic second. The choice after that is yours based on the flight mode you are in.
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When a wing (or rotor) stalls, the airflow becomes very turbulent and the net result is pure drag with no lift at all. The rotor (or wing) is effectively at right angles yo the direction of airflow. You need to be able to reduce the angle of the airflow across the wing or rotor to enable it to function as a lifting device again and for that you need engine power to overcome the drag.
TC: I am in support of your view. (See also the H-19 video above for the 'old school' and proven [for those aircraft at that time] autorotational teaching method).
However, I am sympathetic to HC's perspective in that (I think) we may (to some extent) be talking 'autorotational semantics' in that even among us 'collective first' types .. there is (or so I believe) a recognition that cyclic control is 'intuitive' and which may translate into simultaneous or even 'cyclic first' responses according to the specific profile of the craft's entry into autorotation .. if indeed that makes sense.
One thing is certain (as several have pointed-out) and it is that there are certain scenarios in which one would decidedly not apply aft cyclic first. The same however cannot be said with regard to pitch.
However, I am sympathetic to HC's perspective in that (I think) we may (to some extent) be talking 'autorotational semantics' in that even among us 'collective first' types .. there is (or so I believe) a recognition that cyclic control is 'intuitive' and which may translate into simultaneous or even 'cyclic first' responses according to the specific profile of the craft's entry into autorotation .. if indeed that makes sense.
One thing is certain (as several have pointed-out) and it is that there are certain scenarios in which one would decidedly not apply aft cyclic first. The same however cannot be said with regard to pitch.
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Savoia - the rotorbursts were purely down to bad maintenance - the one I managed to get on to a small island in some Loch or other on the Fort William run hadn't been comp-washed for a couple of years. The other one over Manchester airport (Kilroe's) was also bad maintenance, but there was a lot else wrong with that aircraft as well - I believe Dollar charged over £30K to put everything right after the ambulance conversion that was done in Blackpool. You can imagine that I took an early interest in what engineers were doing (or not doing) to my machines!
Actually, the flares were helpful - you need to punch the first one off inside the first 1000 feet, then the second around 400 because they take time to deploy. They stopped using them on the Gazelles in the Army because they would occasionally fire off when you pushed the transmit button - Eurocopter electrics again!
I've taught hover autos from 50 - 100 feet (powerlines) in the 206*, and you do need a slight check back on the cyclic in those cases otherwise the beast will gain speed all by itself, when you really should be doing a vertical** - to this day, even at the top of the avoid curve, I would probably do a vertical rather than try to gain speed, flare, etc.
*Don't try this at home without proper supervision! Especially not in anything that's not a 206 (big blades, robust construction). Naturally, the collective going down takes priority.
**In the same vein, if you try to take off vertically, but do nothing with the cyclic, you will find the machine gaining some airspeed high up by itself - you need a check back in that situation as well.
WRT your earlier comment, the driving portion of the disc has a lot to do, and it only really covers about a third of the swept area. It's easy to see why, if the blade RPM gets too low that it has more work to do with less ability. In point of fact, the driving area is really windmilling, because it is driving the tail rotor and other hangers on. The only parts that are truly in autorotation in the proper sense of the word (zero torque) are the neutral points between the driven, driving and stalled areas.
Phil
Actually, the flares were helpful - you need to punch the first one off inside the first 1000 feet, then the second around 400 because they take time to deploy. They stopped using them on the Gazelles in the Army because they would occasionally fire off when you pushed the transmit button - Eurocopter electrics again!
I've taught hover autos from 50 - 100 feet (powerlines) in the 206*, and you do need a slight check back on the cyclic in those cases otherwise the beast will gain speed all by itself, when you really should be doing a vertical** - to this day, even at the top of the avoid curve, I would probably do a vertical rather than try to gain speed, flare, etc.
*Don't try this at home without proper supervision!
Especially not in anything that's not a 206 (big blades, robust construction). Naturally, the collective going down takes priority.**In the same vein, if you try to take off vertically, but do nothing with the cyclic, you will find the machine gaining some airspeed high up by itself - you need a check back in that situation as well.
WRT your earlier comment, the driving portion of the disc has a lot to do, and it only really covers about a third of the swept area. It's easy to see why, if the blade RPM gets too low that it has more work to do with less ability. In point of fact, the driving area is really windmilling, because it is driving the tail rotor and other hangers on. The only parts that are truly in autorotation in the proper sense of the word (zero torque) are the neutral points between the driven, driving and stalled areas.
Phil
Last edited by paco; 13th Dec 2013 at 16:39.