EFATO
Yep. Nicely done.
So essentially you confirmed the Rogers (?) paper that the lowest loss of altitude, assuming certain stability conditions, is achieved by making a 45-degree banked turn at the edge of the stall. Good.
GtE, I'm still interested in your stab at doing a paper when you remove those stability conditions, and analyze a proper EFATO situation. Mark1234 found out that the best results in that situation are achieved by initially setting a 60 degree bank, pulling to the stall, and reducing the bank angle as you fly the turn and the nose drops.
So essentially you confirmed the Rogers (?) paper that the lowest loss of altitude, assuming certain stability conditions, is achieved by making a 45-degree banked turn at the edge of the stall. Good.
GtE, I'm still interested in your stab at doing a paper when you remove those stability conditions, and analyze a proper EFATO situation. Mark1234 found out that the best results in that situation are achieved by initially setting a 60 degree bank, pulling to the stall, and reducing the bank angle as you fly the turn and the nose drops.
I'm at the final stages of leading a multi-author paper analysing optimal stall recovery actions for single engined aeroplanes at the moment (5 of us as co-authors, and between us we've tested currently 12 aeroplane types, and that'll shortly be 15) - that should be done in the next couple of months and we can then agree the final wording and analysis and I can get it into the peer review.
We did this on the basis of preparing an outline test plan and analysis route, then opening the project up to participation. Several colleagues have done so - using their own flight resources, and it's been a lot of fun. Also, it's prepared conclusions that are based upon test results on 15 aircraft and brains of 5 variably experienced pilots. The best NASA have ever done on a similar project was I think 7 aeroplanes and 3 researchers.
[Hence our firmly unofficial lab slogan - "if it was easy, NASA would have done it already" !]
So, starting at Rogers' paper, I think one needs to construct algebraically a turnback that looks something like this:
(1) Engine failure, initial deceleration from Vy over a period of seconds while the pilot says "oh f********" slowly, then pitch to target turnback speed.
(2) Roll left to 45 degrees of bank whilst maintaining target turnback speed
(3) Change heading through 45 degrees.
(4) Roll right through 90 degrees to 45 degrees right bank
(5) Maintain 45 degrees right bank and target turnback speed until approaching runway centreline
(6) Reverse again to 45 degrees left bank to intercept centreline on runway track.
(7) Establish 1.3Vs and drop gear and flaps.
Each of those 7 is fairly easily modelled initially, although the model will certainly contain errors. Specifically:
(1) I have a model already for deceleration post engine failure that I published a few years ago and use for planning stall tests in certification programmes. There are standard values for reaction times, but this can also be tried in the simulator with a selection of pilots (in fact I think we might have that data already from another project).
(2) There are standard minimum requirements for achievable roll rate in the certification standards. If we assume that, it's a reasonable worst case.
(3) Standard flight mechanics
(4) As (2)
(5) As (3)
(6) Probably a bit of a guesstimate needed, but do-able.
(7) As (3)
We could then construct a test plan around that model which for a range of airframes at a safe altitude does the following:
(A) Confirm or deny 45 degrees of bank as best for height loss in the turn using a nominal fixed speed.
(B) Determine for that aircraft, the optimal speed for height loss in a turn at the optimum (hopefully 45 degrees) bank angle, and the height lost at that speed and bank angle.
(C) Validate the estimate for that aircraft of deceleration following an initial engine failure with height held for a pre-determined "Oh f**********" time.
(D) Determine height lost and time taken in accelerating to turnback speed following initial deceleration.
(E) Determine height lost and time taken to go from wings level at turnback speed to 1.3Vs with gear and flaps down.
(F) Finally and crucially, assess the actual handling difficulty in handling each part of the manoeuvre, and the manoeuvre overall, with a particular concentration on stall avoidance and runway centreline capture, using standard scales for pilot compensation and workload (Cooper Harper for the first, probably NASA-TLX for the second).
The analysis will take some time, the flying would probably take around 90-120 minutes on a single sortie for an experimental test pilot, nearer 180 minutes over 2-3 sorties for somebody not experienced in flight test ideally working with a flight test engineer in the other seat.
Standard GPS units would do a reasonable job of recording flight tracks, plus voice recorders (a dictaphone plus a tie-clip microphone stuck in the headset earpiece) can help a lot in gathering pilot comments, although I can bring a portable flight data recorder to the party.
If we could get the number of aeroplanes tested into double figures, back it up with some robust analysis, and include a few flying instructors in the authors list to make sure anything recommended is sensible and feasible. Well not only would that go well beyond Rogers' initial analysis, but we'd end up with something that could be a real benchmark in safety practice and training.
Worth doing I think. I think I'll do it and open it up to collaboration (and shared blame or glory as appropriate!); I can certainly bring three aeroplanes (a modern 4-seat low wing, a vintage high wing taildragger, a microlight) to the party and can think of a few fellow flying researchers who'd enjoy joining in. (Pilot_DAR, India-Mike, any interest in playing?)
G
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(1) Engine failure, initial deceleration from Vy over a period of seconds while the pilot says "oh f********" slowly, then pitch to target turnback speed.
(2) Roll left to 45 degrees of bank whilst maintaining target turnback speed
(3) Change heading through 45 degrees.
(4) Roll right through 90 degrees to 45 degrees right bank
(5) Maintain 45 degrees right bank and target turnback speed until approaching runway centreline
(2) Roll left to 45 degrees of bank whilst maintaining target turnback speed
(3) Change heading through 45 degrees.
(4) Roll right through 90 degrees to 45 degrees right bank
(5) Maintain 45 degrees right bank and target turnback speed until approaching runway centreline
Personally I would turn back towards the runway immediately (into the crosswind to minimize offset), and correct for the offset only at the end of the maneuver. So the teardrop shape is reversed.
Considering that you are going to lose altitude for sure during all this turning, I think that gives a better chance of making the threshold. Especially if the runway is short and you used the whole length during the take-off run. And in any case, I'd rather go off the far end of the runway at taxi speed, than undershooting the runway at flying speed.
Furthermore I think steps 1 and 2 should be combined. You drop the nose while rolling into the turn. So that by the time the nose is in the appropriate glide attitude, you are already established in the proper angle of bank and can start pitching for the turn straight away. (If you assume that this is essentially a ballistic maneuver it's relatively easy to model.)
In fact, Mark1234s experiment suggested that during this stage you can actually bank to 60 degrees, pull to the edge of the stall (not with 2G - it will be less but that's OK). Because you're not pulling 2G the nose will drop. At the time the nose has dropped to the glide attitude, you roll out to a bank angle that's sustainable, given your attitude, for the remainder of the turn. (Probably around 45 degrees.)
But I admit that that last maneuver will probably be an incredible bitch to model mathematically. And I doubt whether it would be the right technique to teach to low-time pilots in any case: If you don't roll back to a sustainable angle of bank at the appropriate time, you set yourself up for a major stall/spin accident. But that roll back might well be counter-intuitive to somebody without aerobatics/unusual attitudes experience.
Worth doing I think. I think I'll do it and open it up to collaboration (and shared blame or glory as appropriate!); I can certainly bring three aeroplanes (a modern 4-seat low wing, a vintage high wing taildragger, a microlight) to the party and can think of a few fellow flying researchers who'd enjoy joining in. (Pilot_DAR, India-Mike, any interest in playing?)
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Genghis
Out of interest we teach turnbacks in the Grob 109B in the Air Cadet Organisation as follows:
Full engine failure - adopt glide attitude and 60kts, then assess height, up to 500' land ahead, above 500' turn back towards airfield. If landing area ahead is unsuitable you can turnback when above 300'.
Partial engine failure - if above 400' or able to climb to 400' then turn back to fly a mini-circuit to airfield, if not position to land ahead.
Even in a motorglider it needs a lot of height to be successful. Having spent about 800hrs teaching this stuff in the circuit to cadets, the wind and lift/sink conditions on the day have a massive influence and make the biggest difference to success.
Out of interest we teach turnbacks in the Grob 109B in the Air Cadet Organisation as follows:
Full engine failure - adopt glide attitude and 60kts, then assess height, up to 500' land ahead, above 500' turn back towards airfield. If landing area ahead is unsuitable you can turnback when above 300'.
Partial engine failure - if above 400' or able to climb to 400' then turn back to fly a mini-circuit to airfield, if not position to land ahead.
Even in a motorglider it needs a lot of height to be successful. Having spent about 800hrs teaching this stuff in the circuit to cadets, the wind and lift/sink conditions on the day have a massive influence and make the biggest difference to success.
Blagger - how are ACCGS teaching the Vigilant T1 turnback? - in terms of sequence of actions, headings and bank angles? I don't recall that we ever looked at it in the clearance programme at BDN, but arguably that is a CGS task anyhow.
Backpacker - you're on, although I also know one of the research Test Pilots at NLR quite well, and I imagine he'd be delighted to come and work with you if I had a chat with him.
G
Backpacker - you're on, although I also know one of the research Test Pilots at NLR quite well, and I imagine he'd be delighted to come and work with you if I had a chat with him.
G
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Genghis - in principle yes. Currently at 0 Chipmunks though due to wind damage. The flight mechanics, I think, is probably only 50% of the turn back problem. The rest is operational, environmental and human factors. I've flown perhaps half a dozen turn backs in the last three years either in FI training or club standardization flights with our FIE. Although pretty straightforward to fly success is not determined exclusively by ability or aerodynamics.
But one has to start somewhere
But one has to start somewhere
Great I-M, and I agree - hence my references to using CHR and NASA-TLX as well as the flight mechanics tasks. Cooper Harper task construction will be a really major part of getting this right, and I can foresee a fairly robust round table on that subject.
Continued sympathies on the sad and undeserved death of the chippie. If we can meet at a suitable airfield or you're heading south, we could standardise by doing my Stinson together.
G
Continued sympathies on the sad and undeserved death of the chippie. If we can meet at a suitable airfield or you're heading south, we could standardise by doing my Stinson together.
G
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Genghis
Initial action lower nose to achieve 60kts
Assess RPM + height = make decision what to do
500ft + = turnback
300-500ft = turnback only if landing area ahead unsuitable
<300ft = land ahead
Turnback 180 deg onto a close-in downwind track (if you are going to turnback rather than going ahead)
Max 30 deg AoB (although use small AoB if a partial power loss mini circuit)
Aim to turn back again to land into wind, must start final turn by 250ft (300ft for trainees), but if height loss dictates you might have to accept a downwind landing.
In all cases level the wings by 100ft minimum and accept landing area ahead.
Approach attitude and speed all times when below 400ft.
Also, Tutor procedure is initiate not below 700ft, adopt glide speed + 5kts, turn back through 180 deg using max 45deg AoB (just back towards airfield), then further turn to land somewhere on airfield (or possibly straight downwind), wings must be level by 200' MSD.
I think you should model a 180deg turn onto a close-in downwind leg, you might then land straight downwind or turn again depending on height loss and landing areas available. Often an approach to a cross wind runway or clear surface ends up being the case.
Initial action lower nose to achieve 60kts
Assess RPM + height = make decision what to do
500ft + = turnback
300-500ft = turnback only if landing area ahead unsuitable
<300ft = land ahead
Turnback 180 deg onto a close-in downwind track (if you are going to turnback rather than going ahead)
Max 30 deg AoB (although use small AoB if a partial power loss mini circuit)
Aim to turn back again to land into wind, must start final turn by 250ft (300ft for trainees), but if height loss dictates you might have to accept a downwind landing.
In all cases level the wings by 100ft minimum and accept landing area ahead.
Approach attitude and speed all times when below 400ft.
Also, Tutor procedure is initiate not below 700ft, adopt glide speed + 5kts, turn back through 180 deg using max 45deg AoB (just back towards airfield), then further turn to land somewhere on airfield (or possibly straight downwind), wings must be level by 200' MSD.
I think you should model a 180deg turn onto a close-in downwind leg, you might then land straight downwind or turn again depending on height loss and landing areas available. Often an approach to a cross wind runway or clear surface ends up being the case.
Blagger (but anybody else flying Vigilants and Tutors...) You can't just turn 180 degrees - either you're going to:
(1) turn 45 left, turn 225 right,
(2) turn 225 right, turn 45 left
A turnback has always got to involve roughly 270 degrees of heading change.
Unless, I suppose, you can take advantage of a howling crosswind.
What you've described really seem to be outfield landings, somewhere on the airfield - rather than back onto the runway which is surely what a turnback is about. A turn onto a downwind leg is a glide circuit, not a turnback.
In my opinon
G
(1) turn 45 left, turn 225 right,
(2) turn 225 right, turn 45 left
A turnback has always got to involve roughly 270 degrees of heading change.
Unless, I suppose, you can take advantage of a howling crosswind.
What you've described really seem to be outfield landings, somewhere on the airfield - rather than back onto the runway which is surely what a turnback is about. A turn onto a downwind leg is a glide circuit, not a turnback.
In my opinon
G
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Genghis - A turnback (in the RAF anyway) is a manoeuvre to return to the airfield because the landing area options ahead are unsuitable. It is not soley focussed on a downwind landing on the runway. The airfield is a known environment, flat, with limited obstacles etc.. where you have better options for a forced landing than the terrain ahead. The subsequent landing could be anywhere on the airfield, it may be downwind on the runway but that would depend on a host of factors on the day. Most of the real SEP turnbacks I have known have resulted in a landing on the grass outside of the runway surface.
So am I, and it might be viable to open this up for wider participation.
I'm at the final stages of leading a multi-author paper analysing optimal stall recovery actions for single engined aeroplanes at the moment (5 of us as co-authors, and between us we've tested currently 12 aeroplane types, and that'll shortly be 15) - that should be done in the next couple of months and we can then agree the final wording and analysis and I can get it into the peer review.
I'm at the final stages of leading a multi-author paper analysing optimal stall recovery actions for single engined aeroplanes at the moment (5 of us as co-authors, and between us we've tested currently 12 aeroplane types, and that'll shortly be 15) - that should be done in the next couple of months and we can then agree the final wording and analysis and I can get it into the peer review.
Genghis - A turnback (in the RAF anyway) is a manoeuvre to return to the airfield because the landing area options ahead are unsuitable. It is not soley focussed on a downwind landing on the runway. The airfield is a known environment, flat, with limited obstacles etc.. where you have better options for a forced landing than the terrain ahead. The subsequent landing could be anywhere on the airfield, it may be downwind on the runway but that would depend on a host of factors on the day. Most of the real SEP turnbacks I have known have resulted in a landing on the grass outside of the runway surface.
Typical light aeroplane, best glide 70 kn, so we fly the turnback at 75, using 45 degrees of bank, you get a 300 metre turn diameter.
Vigilant 60 knots, 30 degrees of bank, you get a 340 metre turn diameter.
Higher performance - try a Piper Arrow: 79kn best glide, so 84 turnback speed, 45 degrees of bank, gives 380m turn diameter.
To some extent, most aeroplanes at most airfields you are going have to turn beyond 180 degrees and then correct roughly back onto the runway heading. Apart from a big military airfields, most times and places, 300 metres likely to be well outside the airside perimeter.
So, I think that a 270 degree total heading change is realistic. This is what Rogers used in his paper.
My increasingly distant recollection of Bulldog, Tucano and Hawk practices is that turnbacks were always trained back onto the runway also.
G
If you are a proficient aerobatic pilot who practices regularly this is no big deal. However at the risk of sounding arrogant, if you are the average PPL with less than 250 hours total time who flies 15 to 20 hours a year, this is a recipe for a low altitude stall/spin accident, and those are almost invariably fatal, a sad fact confirmed by the accident statistics........
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Hi Genghis, you're right - I accept that more than 180deg will generally be required in SEP types, I just think that a 270deg total is quite a demanding base requirement. What I'm trying to get at is that in real world situations I think the most likely scenario is that following an EFATO, the aircraft will be turned back towards the airfield and the eventual landing area will be somewhere across the airfield / runway departed on. For example, at Wellesbourne, a departure on Rwy 18, EFATO, turnback to right, would (at best) result in a landing somewhere on the grass to the left of Rwy 05. A likely heading of perhaps somewhere around 020? Perhaps a total turn of around 225deg? I just think that excessive low level turning would be overly demanding in real life and will make the model results very pessimistic about success.
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And there is the rub. At a moment of high stress induced by the engine failing you have to fly the aircraft right at the edge of its envelope at an altitude that leaves no margin for error.
GENERAL WARNING to the readers of this thread.
Be advised that we are currently discussing theoretical scenarios at the edge of what an airplane is capable of doing. Unless you are extremely proficient in flying at the edge of the envelope, DO NOT try the techniques mentioned here in a for-real EFATO scenario.
If you want to practice these, do so at a safe height and with an instructor on board.
And there is the rub. At a moment of high stress induced by the engine failing you have to fly the aircraft right at the edge of its envelope at an altitude that leaves no margin for error.
If you are a proficient aerobatic pilot who practices regularly this is no big deal. However at the risk of sounding arrogant, if you are the average PPL with less than 250 hours total time who flies 15 to 20 hours a year, this is a recipe for a low altitude stall/spin accident, and those are almost invariably fatal, a sad fact confirmed by the accident statistics........
If you are a proficient aerobatic pilot who practices regularly this is no big deal. However at the risk of sounding arrogant, if you are the average PPL with less than 250 hours total time who flies 15 to 20 hours a year, this is a recipe for a low altitude stall/spin accident, and those are almost invariably fatal, a sad fact confirmed by the accident statistics........
But, at a first look, what N did was show that Rogers' figure of 45 degrees bank angle for minimum height loss per degrees of turn seems to be correct. That in itself is a useful conclusion because it gives a bank angle that *probably* should be used by a pilot who is sharp enough and positioned well to fly a turnback. It is however only a part of a much bigger problem.
G
Happy to do my part for the R182. I'd expect the results for the non-retractable 182 to be substantially different (worse).
Some other thoughts/comments...
1. Re Backpacker's caveat/disclaimer: according to a thread over on the Cessna Pilot's Association, there are quite a lot of fatalities even WITH an instructor on board. So I think that should be "...with an instructor who has extensive experience with this manouevre". (I still don't really understand WHY - it requires precise flying but nothing extraordinary. Not something for a 100hr PPL but a CPL/FI with a few hundred hours should be able to do it safely).
2. I flew mine with a teardrop, i.e. initial turn of <135 degress heading back for the departure end of the runway, then another small (<45 deg) turn to align with the runway. The shape described by Genghis will leave you further from the runway end. Which would be good if you were a bit higher - when I tried it at 800' on a 4000' runway, I was way too far down the runway and did not land.
3. I'm a bit puzzled by the reaction time issue. Even 2.4S strikes me as a lot, and certainly 4S. If you're flying a Robinson 22 (heli) and the engine stops, you most certainly don't have that long before the rotor stalls and you plummet earthwards. But people do survive for-real engine failures in them. (Admittedly quite a few haven't). Part of it I think is being "wired for failure". (For example there's a spot where I know perfectly well that the engine will "fail" when I'm flying the heli, and my reactions are correspondingly good. The goal of course is to be that good no matter when). On take-off, good training is to be expecting it to suddenly get quieter. The one time it did happen to me, I was pointed back to the nearest airport in a LOT less than 4S. (It was only a brief engine hesitation and I was at altitude).
4. I respect Mark1234's experimental results, but I'd also say that for a repeatable, survivable technique, going initially to 60 degrees is (in my plane anyway) a LOT harder than 45. I was losing 10 knots on the initial roll then finding it hard not to pick up a 10 knot surplus (i.e. gaining 20 knots) as the nose dropped. It was quite uncomfortable - for someone with no acro experience or not *extremely* comfortable with the handling of the plane, it could be terrifying.
Some other thoughts/comments...
1. Re Backpacker's caveat/disclaimer: according to a thread over on the Cessna Pilot's Association, there are quite a lot of fatalities even WITH an instructor on board. So I think that should be "...with an instructor who has extensive experience with this manouevre". (I still don't really understand WHY - it requires precise flying but nothing extraordinary. Not something for a 100hr PPL but a CPL/FI with a few hundred hours should be able to do it safely).
2. I flew mine with a teardrop, i.e. initial turn of <135 degress heading back for the departure end of the runway, then another small (<45 deg) turn to align with the runway. The shape described by Genghis will leave you further from the runway end. Which would be good if you were a bit higher - when I tried it at 800' on a 4000' runway, I was way too far down the runway and did not land.
3. I'm a bit puzzled by the reaction time issue. Even 2.4S strikes me as a lot, and certainly 4S. If you're flying a Robinson 22 (heli) and the engine stops, you most certainly don't have that long before the rotor stalls and you plummet earthwards. But people do survive for-real engine failures in them. (Admittedly quite a few haven't). Part of it I think is being "wired for failure". (For example there's a spot where I know perfectly well that the engine will "fail" when I'm flying the heli, and my reactions are correspondingly good. The goal of course is to be that good no matter when). On take-off, good training is to be expecting it to suddenly get quieter. The one time it did happen to me, I was pointed back to the nearest airport in a LOT less than 4S. (It was only a brief engine hesitation and I was at altitude).
4. I respect Mark1234's experimental results, but I'd also say that for a repeatable, survivable technique, going initially to 60 degrees is (in my plane anyway) a LOT harder than 45. I was losing 10 knots on the initial roll then finding it hard not to pick up a 10 knot surplus (i.e. gaining 20 knots) as the nose dropped. It was quite uncomfortable - for someone with no acro experience or not *extremely* comfortable with the handling of the plane, it could be terrifying.
Which is why in a full research programme we need to include a reaction delay, and assess the ease of maintaining the best speed and bank angle, and ease of stall avoidance, and the overall pilot workload. With other things.
But, at a first look, what N did was show that Rogers' figure of 45 degrees bank angle for minimum height loss per degrees of turn seems to be correct. That in itself is a useful conclusion because it gives a bank angle that *probably* should be used by a pilot who is sharp enough and positioned well to fly a turnback. It is however only a part of a much bigger problem.
G
But, at a first look, what N did was show that Rogers' figure of 45 degrees bank angle for minimum height loss per degrees of turn seems to be correct. That in itself is a useful conclusion because it gives a bank angle that *probably* should be used by a pilot who is sharp enough and positioned well to fly a turnback. It is however only a part of a much bigger problem.
G
An unexplored and IMO equally interesting scenario is the best way to do a turnback with say 1/3 available power, not enough to sustain level flight but enough to greatly reduce your sink rate. Off the top of my head my thought would be a teardrop with an initial 45 degree turn to one side followed by a 225 degree turn back to final with lower bank angle (30 deg ?) which would reduce the sink rate in the turn would be best. The 225 deg turn could be modified if you were too high (what I believe would be a likely outcome) by extending the flight path through the runway centre line and then turning back in.
Thoughts ?
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GENERAL WARNING to the readers of this thread.
Be advised that we are currently discussing theoretical scenarios at the edge of what an airplane is capable of doing. Unless you are extremely proficient in flying at the edge of the envelope, DO NOT try the techniques mentioned here in a for-real EFATO (Engine Failure After Take-Off) scenario.
If you want to practice these, do so at a safe height and with an instructor on board.
BP - Very well said. I baled out of this thread a few days ago, and in my last post I advocated what you have just stated, but I am concerned about some of the points I am reading here. Every type, every situation, every type of weather, every type of pilot, what sort of day you are having/have had, all have a great bearing on 'the turnback', the decision, the 'emergency'. All of this debate is theoretical.
Be advised that we are currently discussing theoretical scenarios at the edge of what an airplane is capable of doing. Unless you are extremely proficient in flying at the edge of the envelope, DO NOT try the techniques mentioned here in a for-real EFATO (Engine Failure After Take-Off) scenario.
If you want to practice these, do so at a safe height and with an instructor on board.
BP - Very well said. I baled out of this thread a few days ago, and in my last post I advocated what you have just stated, but I am concerned about some of the points I am reading here. Every type, every situation, every type of weather, every type of pilot, what sort of day you are having/have had, all have a great bearing on 'the turnback', the decision, the 'emergency'. All of this debate is theoretical.
All of this debate is theoretical
And also had a couple of interesting and enjoyable flights. Not much theoretical about all that.