Cyclic climb after entering autorotation
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Cyclic climb after entering autorotation
Hi folks -
Just read Hugh Mills' "Low Level Hell", in which he describes his first tour in Vietnam flying OH6As.
At one point he describes an engine failure due to gunfire while he was "about forty feet off the ground and doing maybe fifty knots".
His reaction to this situation was: "I dumped collective... pulled the cyclic back.. and managed to cyclic climb to about 150 feet. With that extra altitude, I was able to enter autorotation..."
He managed to land the helicopter - hard, and damaging the skids, but otherwise without incident.
I'm curious what people think of this maneuver. From my own meager experience with the R22, doing something like that would put you dangerously slow and with decaying rotor RPM as you started to drop back down. Of course - the R22 isn't an OH6, and obviously the maneuver worked for Mills, but I'm still curious.
Just read Hugh Mills' "Low Level Hell", in which he describes his first tour in Vietnam flying OH6As.
At one point he describes an engine failure due to gunfire while he was "about forty feet off the ground and doing maybe fifty knots".
His reaction to this situation was: "I dumped collective... pulled the cyclic back.. and managed to cyclic climb to about 150 feet. With that extra altitude, I was able to enter autorotation..."
He managed to land the helicopter - hard, and damaging the skids, but otherwise without incident.
I'm curious what people think of this maneuver. From my own meager experience with the R22, doing something like that would put you dangerously slow and with decaying rotor RPM as you started to drop back down. Of course - the R22 isn't an OH6, and obviously the maneuver worked for Mills, but I'm still curious.
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Do NOT try this at home. The OH6A or H500 is a very capable aircraft. It does have a very wide flight envelope and benefits from being very clean aerodynamically. It is possible for instance to roll off the power at cruise from about 10' off the ground perform a cyclic climb, turn left at the top, and continue turning through 360 degrees and land, engine off. I have demonstrated autorotations where at the lower RRPM limits and higher airspeed, you can fly the rest of a circuit from 1000' downwind, including all the square corners that would put some fixed wings to shame. The OH6/500 with all the doors removed is still cleaner than a clean B206. Also a lean OH6/500 is not much heavier empty than a 300C. It does also benefit in being a little more crashworthy than others of a similar generation - up to a point.
I wouldn't be surprised if the manouvre you describe was feasible, although it would be difficult too demonstrate without breaking something.
A power ON cyclic climb from 50 knots in a H500 produces a lot more performance than you would expect.
I wouldn't be surprised if the manouvre you describe was feasible, although it would be difficult too demonstrate without breaking something.
A power ON cyclic climb from 50 knots in a H500 produces a lot more performance than you would expect.
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Heh.
Don't worry, as I stated in my post I didn't think this would be terribly feasible in an R22. I was mainly wondering if such a maneuver was possible in the OH6, or if it was a case of a less-than-accurate memory on Mills' part.
I still can't imagine how you'd manage to autorotate successfully from 150 feet and > 30kts airspeed.
Don't worry, as I stated in my post I didn't think this would be terribly feasible in an R22. I was mainly wondering if such a maneuver was possible in the OH6, or if it was a case of a less-than-accurate memory on Mills' part.
I still can't imagine how you'd manage to autorotate successfully from 150 feet and > 30kts airspeed.
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I used to teach such a maneuver in the Cobra, it is doable and quite handy when in low level, high speed flight.
Mills is slightly off in two places:
1) where he says "I dumped collective... pulled the cyclic back.. and managed to cyclic climb to about 150 feet. With that extra altitude, I was able to enter autorotation..."
He was in autorotation when he started the cyclic flare, but with a combination of forward speed and rotor inertia, he was able to climb while in autorotation, and find a better place to touchdown.
2) where he estimates that he was at "about forty feet off the ground and doing maybe fifty knots".
The energy at 50 knots is paltry, and there is no kinetic energy to fuel such a climb. Were he at 130, the climb would be normal and nice, at 50, he wouldn't get more than a few feet up. The climb can be calculated easily, as the energy in his machine is 1/2MV squared (M is mass, V is speed), and the energy needed to climb is MGH (G is the gravitational constant, H is height). In a cyclic climb, the two must be equal (if the climb extracts all the energy, and you have zero knots at the top). For 130 knots, you get 750 feet higher, for 50 knots you get 110 feet higher. At zero, you can't autorotate, so you should calculate the climb with a residual speed of 40 knots for an OH-6.
At 130 knots, topping the climb at 60 knots allows you to climb almost 600 feet. At 50 knots, topping the climb at 40 knots allows you to climb about 40 feet.
Mills was wrong, or at least his memory was, but not by that much.
He was probably between 65 and 70 knots knots when he started the climb, and if he rounded out at 40 knots, he would have climbed about 150 feet.
Mills is slightly off in two places:
1) where he says "I dumped collective... pulled the cyclic back.. and managed to cyclic climb to about 150 feet. With that extra altitude, I was able to enter autorotation..."
He was in autorotation when he started the cyclic flare, but with a combination of forward speed and rotor inertia, he was able to climb while in autorotation, and find a better place to touchdown.
2) where he estimates that he was at "about forty feet off the ground and doing maybe fifty knots".
The energy at 50 knots is paltry, and there is no kinetic energy to fuel such a climb. Were he at 130, the climb would be normal and nice, at 50, he wouldn't get more than a few feet up. The climb can be calculated easily, as the energy in his machine is 1/2MV squared (M is mass, V is speed), and the energy needed to climb is MGH (G is the gravitational constant, H is height). In a cyclic climb, the two must be equal (if the climb extracts all the energy, and you have zero knots at the top). For 130 knots, you get 750 feet higher, for 50 knots you get 110 feet higher. At zero, you can't autorotate, so you should calculate the climb with a residual speed of 40 knots for an OH-6.
At 130 knots, topping the climb at 60 knots allows you to climb almost 600 feet. At 50 knots, topping the climb at 40 knots allows you to climb about 40 feet.
Mills was wrong, or at least his memory was, but not by that much.
He was probably between 65 and 70 knots knots when he started the climb, and if he rounded out at 40 knots, he would have climbed about 150 feet.
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I demonstrate to students in an R-22 that if you come in at 80 knots in an auto, when you perform a cyclic flare, you can actually climb up about 50 feet with ease and your airspeed drops to around 60 knots.
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The 44 is capable of climbing during autorotation but not by much. I've tried doing a few times while praticising autos on my own and as long as you enter the climb with some decent speed it will climb a little, although it is more an 'inflated flare' than it is a climb and it certainly doesn't climb more than 50 ft.
I can't see the use of the process outside of combat, except of course if you saw a fence at the last minute but chances are your airspeed would be too low at that stage.
What do ya'll think? Any use for it?
I can't see the use of the process outside of combat, except of course if you saw a fence at the last minute but chances are your airspeed would be too low at that stage.
What do ya'll think? Any use for it?
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Welllllll,..... I actually got tought that technique by my instructor back when I did my Hu500 transition ....he was one of them Ex US Army Fort Wolters/ Mineral Wells IP guys and I gotta tell u IT WORKS .....its the old Airspeed for Height trade and you don't need to be at 50' agl to use it ....done well it means U can get into Autorotation without losing much height at all AND/OR U can use the technique to recover Nr if things have turned out a bit wrong!!! ....but U better have your wits about you when U do it!
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You would be neglagent and quite simply dumb to try this, trying to trade a lot of speed for a bit of height at low level? There is a good chance your engine will fail when practicing Autos, then how do you plan to get your speed back?
Not reccomended practice for Commercial Aviation, and practicing in 22' and 44's, Its Cowboys like this that Increase the Insurance for all of us.
Not reccomended practice for Commercial Aviation, and practicing in 22' and 44's, Its Cowboys like this that Increase the Insurance for all of us.
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The memory of Hugh Mills has no doubt been subjected to the unpredictable influence of what Kurt Vonnegut once called the "cronosynclastic infidibulum". Any attempt to unravel Mr. Mills' experience would encounter certain time distorted memory effects that tend to frustrate normal expectations of temporal linearity and sound phsyics.
Should one neglect high humidity, gross weight, drag (open doors, guns, etc.), pilot reaction time and the like; Mr. Lappos is not far off the mark with his estimate of the height achievable in an OH-6A after an engine failure from 40 feet and 50 knots.
In my opinion, at 40 feet and 50 knots a reduction of collective and straight line deceleration would prove more for more efficient at conserving rotor RPM for pitch-pull, present less time in the sights of enemy weapons, and require significantly less pilot workload to perform.
It would however make rather dull reading.
Should one neglect high humidity, gross weight, drag (open doors, guns, etc.), pilot reaction time and the like; Mr. Lappos is not far off the mark with his estimate of the height achievable in an OH-6A after an engine failure from 40 feet and 50 knots.
In my opinion, at 40 feet and 50 knots a reduction of collective and straight line deceleration would prove more for more efficient at conserving rotor RPM for pitch-pull, present less time in the sights of enemy weapons, and require significantly less pilot workload to perform.
It would however make rather dull reading.
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Autosync, who said I attempted the climb at low-level?
Thanks for that info about engines failing during autorotation, because obviously there is no way I would have already known that! I attempted the collective climb while in autorotation with hard deck of 1000 ft AGL. So if the engine failed I had lots of time to recover, thank you for your concern none the less.
My point is merely that student should perhaps be shown this to be used as an absolute last resort to avoid a fence or a wall if autorotating for real. Surely it's better to lose a bit of speed close to the ground if it means you won't hit something.
Thanks for that info about engines failing during autorotation, because obviously there is no way I would have already known that! I attempted the collective climb while in autorotation with hard deck of 1000 ft AGL. So if the engine failed I had lots of time to recover, thank you for your concern none the less.
My point is merely that student should perhaps be shown this to be used as an absolute last resort to avoid a fence or a wall if autorotating for real. Surely it's better to lose a bit of speed close to the ground if it means you won't hit something.
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Captain Eagle,
I agree. I teach the manuever to show students that should they have to auto to a parking lot, field, etc and a car, fence etc should be in front of them, with sufficient airspeed, they can autorotate over the top.
Autosync,
Simply because you do not possess the experience to perform a manuever does not mean that someone who does is a cowboy. Those who fail to remain educated and expand their experiences are the ones most likely to raise insurance rates. If you live in a box and something happens that forces you outside that box, you are going to have trouble coping.
I agree. I teach the manuever to show students that should they have to auto to a parking lot, field, etc and a car, fence etc should be in front of them, with sufficient airspeed, they can autorotate over the top.
Autosync,
Simply because you do not possess the experience to perform a manuever does not mean that someone who does is a cowboy. Those who fail to remain educated and expand their experiences are the ones most likely to raise insurance rates. If you live in a box and something happens that forces you outside that box, you are going to have trouble coping.
Food for thought:
If you enter a climb by flaring in autorotation then the aircraft will have some amount of inertia carrying it away from the force of gravity. While in the "flare" effect there is the required airflow through the disc from beneath producing an autorotative force and driving the rotor. Should you then apply forward cyclic to maintain some acceptable airspeed (which you need to complete the autorotation) you have to wait until the aircraft stops climbing from this inertia and commences a descent before you can re-establish autorotation. In addition, the application of forward cyclic will unload the rotor disc and your RRPM will reduce from coriolis effect. The net result being a potentially significant loss of RRPM, close to the ground, which in my opinion defeats any logic of doing the manouvre in the first place.
If you enter a climb by flaring in autorotation then the aircraft will have some amount of inertia carrying it away from the force of gravity. While in the "flare" effect there is the required airflow through the disc from beneath producing an autorotative force and driving the rotor. Should you then apply forward cyclic to maintain some acceptable airspeed (which you need to complete the autorotation) you have to wait until the aircraft stops climbing from this inertia and commences a descent before you can re-establish autorotation. In addition, the application of forward cyclic will unload the rotor disc and your RRPM will reduce from coriolis effect. The net result being a potentially significant loss of RRPM, close to the ground, which in my opinion defeats any logic of doing the manouvre in the first place.
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Captain Eagle, CJ Eliassen.
Are you just trying play up there with the big guns?
These guys are test pilots at the top of there game, CE you told us yourself you are 19 and now I am wondering if you are even that?
Play away all you want, just means there will be less competition for work.
I always think that the most dangerous Pilots out there are the ones with the shiny new Licences who think they are ready to take on the world.
Are you just trying play up there with the big guns?
These guys are test pilots at the top of there game, CE you told us yourself you are 19 and now I am wondering if you are even that?
Play away all you want, just means there will be less competition for work.
I always think that the most dangerous Pilots out there are the ones with the shiny new Licences who think they are ready to take on the world.
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Let's try to keep this civil.
coyote - yes, that effect was in the forefront of my mind when I read about this maneuver. Nick et al - is this a significant factor?
coyote - yes, that effect was in the forefront of my mind when I read about this maneuver. Nick et al - is this a significant factor?
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Coyote,
Its all about energy management. If you don't feel comfortable doing such a manuever, then I highly recommend you don't attempt it without first receiving instruction from a competent instructor. Its better to learn the limitations of your aircraft in a controlled environment then become a test pilot by trying something in the heat of an emergency.
Autosync,
Don't get so defensive and don't assume you know someones experience level because they have the confidence to perform manuevers you were never taught. Also, I know shiney new certificate holders that have more confidence, ability, and knowledge then many "big dogs". Just because you are unwilling to learn new things doesn't make those new things bad, wrong, or unsafe. In my experience, those who assume they already know everything and stop learning are the most dangerous pilots. You might want to give this some thought.
Its all about energy management. If you don't feel comfortable doing such a manuever, then I highly recommend you don't attempt it without first receiving instruction from a competent instructor. Its better to learn the limitations of your aircraft in a controlled environment then become a test pilot by trying something in the heat of an emergency.
Autosync,
Don't get so defensive and don't assume you know someones experience level because they have the confidence to perform manuevers you were never taught. Also, I know shiney new certificate holders that have more confidence, ability, and knowledge then many "big dogs". Just because you are unwilling to learn new things doesn't make those new things bad, wrong, or unsafe. In my experience, those who assume they already know everything and stop learning are the most dangerous pilots. You might want to give this some thought.
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Nick wrote: "A cyclic climb from 50 knots in autorotation would only lead to a dull thud."
Agreed. Isn't that what happened? It is doubtful that an autorotative state or equilibrium preserving sufficient main rotor RPM for a 'non-damage landing' could have been obtained if the maneuver were performed as written.
Inspection of the main rotor blades after the "thud" data point would have probably revealed little main rotor in-plane rotational damage as there would not have been significant rotational energy remaining in the system. This would have validated your hypothesis.
Unfortunately, the residual coning angle set to the main rotor blades would probably have rendered the blades less than airworthy and re-use on an aircraft in the next chapter would have been contraindicated.
I have come to conclude that the best responses to an emergency are simple. I am always amazed at the length of pilot reaction and recognition time following a non-training emergency. In the case of an engine failure (for whatever cause) delayed response consumes energy and a procedure or method used in training can become unrealistic or unreasonable in an actual emergency. Instructors should always carefully consider the ability and knowledge of a student before the introduction of advanced autorotational techniques. Continuous forced landing area evalution during flight, techniques to anticipate problems, problem recognition skills and response methods are far more valuable than advance autorotational techniques.
Few experienced helicopter pilots will advocate low speed, low level pop-ups as a realistic engine failure response. Where a forced landing area can be identified a straight line deceleration is the appropriate technique. Flying over a jungle where the nearest forced landing area was probably the biggest tree, a pop-up 'might' allow a pilot to see an appropriate landing area that might not otherwise be seen. There is a compromise in all autorotative techniques. A pop-up provides visibility at the expense of maneuver complexity.
High speed, low level pop-ups and/or level deceleration techniques are a valid skill set for military pilots who may be required to operate in that environment. It is hard to justify this training to pilots who have no compelling reason to expose themselves to the risk of either low or high speed low level flight. My first question to pilots who request this type of training from me is "What are the compelling operational requirements that require you to learn this maneuver?". When such a requirement exists serious consideration should be given to ammending the way the operational requirement so as to reduce the risk.
Agreed. Isn't that what happened? It is doubtful that an autorotative state or equilibrium preserving sufficient main rotor RPM for a 'non-damage landing' could have been obtained if the maneuver were performed as written.
Inspection of the main rotor blades after the "thud" data point would have probably revealed little main rotor in-plane rotational damage as there would not have been significant rotational energy remaining in the system. This would have validated your hypothesis.
Unfortunately, the residual coning angle set to the main rotor blades would probably have rendered the blades less than airworthy and re-use on an aircraft in the next chapter would have been contraindicated.
I have come to conclude that the best responses to an emergency are simple. I am always amazed at the length of pilot reaction and recognition time following a non-training emergency. In the case of an engine failure (for whatever cause) delayed response consumes energy and a procedure or method used in training can become unrealistic or unreasonable in an actual emergency. Instructors should always carefully consider the ability and knowledge of a student before the introduction of advanced autorotational techniques. Continuous forced landing area evalution during flight, techniques to anticipate problems, problem recognition skills and response methods are far more valuable than advance autorotational techniques.
Few experienced helicopter pilots will advocate low speed, low level pop-ups as a realistic engine failure response. Where a forced landing area can be identified a straight line deceleration is the appropriate technique. Flying over a jungle where the nearest forced landing area was probably the biggest tree, a pop-up 'might' allow a pilot to see an appropriate landing area that might not otherwise be seen. There is a compromise in all autorotative techniques. A pop-up provides visibility at the expense of maneuver complexity.
High speed, low level pop-ups and/or level deceleration techniques are a valid skill set for military pilots who may be required to operate in that environment. It is hard to justify this training to pilots who have no compelling reason to expose themselves to the risk of either low or high speed low level flight. My first question to pilots who request this type of training from me is "What are the compelling operational requirements that require you to learn this maneuver?". When such a requirement exists serious consideration should be given to ammending the way the operational requirement so as to reduce the risk.
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Rich Lee Wrote "High speed, low level pop-ups and/or level deceleration techniques are a valid skill set for military pilots who may be required to operate in that environment. It is hard to justify this training to pilots who have no compelling reason to expose themselves to the risk of either low or high speed low level flight."
Cars, wires, fences, walls, poles, people, animals, bushes, trees, rivers, terrain, etc etc.. All of these are reason to know the performance limitations of your helicopter. Or do you suggest that a pilot just run into something and destroy the helicopter and cause potential injury to themselves when a safe landing could be performed with a cyclic climb? Maybe where you live all the ground is flat and there is always a nice flat open field available, but here the ground is rarely flat. Should a pilot have to land uphill, a cyclic climb is required to match the climbing terrain and prevent the thud of which you speak.
I do many things that other pilots consider unsafe because I know things they do not. For example, I hover at 15 feet in an R-22. #1, I have been taught successful hovering autos from this height, and #2, over 90 helicopters have been destroyed by dynamic rollover and none have been damaged from an engine failure in a hover.
So just because you think its unsafe and you are unwilling to learn something new, does not make it unsafe. I wouldn't attempt a no flare auto, but that doesn't mean I think it is unsafe. I simply wouldn't feel comfortable performing the manuever without a great deal of instruction.
Regards,
C.J.
Cars, wires, fences, walls, poles, people, animals, bushes, trees, rivers, terrain, etc etc.. All of these are reason to know the performance limitations of your helicopter. Or do you suggest that a pilot just run into something and destroy the helicopter and cause potential injury to themselves when a safe landing could be performed with a cyclic climb? Maybe where you live all the ground is flat and there is always a nice flat open field available, but here the ground is rarely flat. Should a pilot have to land uphill, a cyclic climb is required to match the climbing terrain and prevent the thud of which you speak.
I do many things that other pilots consider unsafe because I know things they do not. For example, I hover at 15 feet in an R-22. #1, I have been taught successful hovering autos from this height, and #2, over 90 helicopters have been destroyed by dynamic rollover and none have been damaged from an engine failure in a hover.
So just because you think its unsafe and you are unwilling to learn something new, does not make it unsafe. I wouldn't attempt a no flare auto, but that doesn't mean I think it is unsafe. I simply wouldn't feel comfortable performing the manuever without a great deal of instruction.
Regards,
C.J.
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CJ,
You hover 15 feet in an R-22? If I have learned one thing in life it is that spinal injury can cause you to lose all feeling in your penis. That is an unacceptable risk to me.
I do not think it terms of safe and unsafe. I think in terms of risk benefit. I do not hover high in an R-22 because the risk of paralysis to me does not justify a reduction in dynamic rollover risk. Perhaps this is my background. In over 34 years of flying I have had six non-test related engine failures in various aircraft but not one dynamic rollover accident.
I am one of the people who define and validate the height velocity curve and have done so on many helicopters. I have personaly performed over 10,000 touchdown autorotations both with and intentionaly without engine in various civil and military training scenarios. I cannot think of an autorotation technique I have not evaluated or performed or taught. Flare, no flare, pitch pull, no pitch pull, zero speed, high speed, straight-in, high rotor, low rotor, min descent, max glide, 180, 360 and multiples.
My opinion about risk is not predicated on a data set of 1 location. There are many flat areas here in Arizona. Some suitable for landing, others not. There are also mountains and one of the largest canyons in the world. We even have cars, wires, fences, walls, poles, people, animals, bushes, trees, rivers, terrain, etc here. I have flown over a few and with the exception of take-off and landing, I try to do so at a minimum risk altitude. There are few places or types of terrain in the world where I have not flown helicopters.
I do not suggest that pilots run into things and am surprised you would draw that conclusion from my opinions. I suggest that they fly at a height and speed and over a path where extraordinary skill or knowledge will not be required to land in the event of a power failure.
Please note that the term "unsafe" is yours, not mine. I said it is difficult to justify the risk. I have spent my whole life learning how to fly helicopters and I continue to learn so I do not understand why you suggest I am unwilling to learn. I even learn how to do "unsafe" things, but I have also learned when the benefit justifies the risk. Helicopter flying is like that.
Your reasoning seems flawed to me in that you accept risk that I will not; but we all define risk individually. However when I read that you do things other pilots consider unsafe you remind me of the soldier on the parade field who complained because he was the only one marching in time to the drum.
Intelligence is the flower of discrimination. There are many examples of the flower blooming but not bearing fruit.
You hover 15 feet in an R-22? If I have learned one thing in life it is that spinal injury can cause you to lose all feeling in your penis. That is an unacceptable risk to me.
I do not think it terms of safe and unsafe. I think in terms of risk benefit. I do not hover high in an R-22 because the risk of paralysis to me does not justify a reduction in dynamic rollover risk. Perhaps this is my background. In over 34 years of flying I have had six non-test related engine failures in various aircraft but not one dynamic rollover accident.
I am one of the people who define and validate the height velocity curve and have done so on many helicopters. I have personaly performed over 10,000 touchdown autorotations both with and intentionaly without engine in various civil and military training scenarios. I cannot think of an autorotation technique I have not evaluated or performed or taught. Flare, no flare, pitch pull, no pitch pull, zero speed, high speed, straight-in, high rotor, low rotor, min descent, max glide, 180, 360 and multiples.
My opinion about risk is not predicated on a data set of 1 location. There are many flat areas here in Arizona. Some suitable for landing, others not. There are also mountains and one of the largest canyons in the world. We even have cars, wires, fences, walls, poles, people, animals, bushes, trees, rivers, terrain, etc here. I have flown over a few and with the exception of take-off and landing, I try to do so at a minimum risk altitude. There are few places or types of terrain in the world where I have not flown helicopters.
I do not suggest that pilots run into things and am surprised you would draw that conclusion from my opinions. I suggest that they fly at a height and speed and over a path where extraordinary skill or knowledge will not be required to land in the event of a power failure.
Please note that the term "unsafe" is yours, not mine. I said it is difficult to justify the risk. I have spent my whole life learning how to fly helicopters and I continue to learn so I do not understand why you suggest I am unwilling to learn. I even learn how to do "unsafe" things, but I have also learned when the benefit justifies the risk. Helicopter flying is like that.
Your reasoning seems flawed to me in that you accept risk that I will not; but we all define risk individually. However when I read that you do things other pilots consider unsafe you remind me of the soldier on the parade field who complained because he was the only one marching in time to the drum.
Intelligence is the flower of discrimination. There are many examples of the flower blooming but not bearing fruit.