Snowbird crash in CYKA

[pelmet]

After the engine failure at 400 feet, look inside at the instruments to target three things during the fairly aggressive pitch down……speed(best glide), bank(45 degrees), and finally a target reciprocal heading(turn into a crosswind).

For anyone wondering, the speed at which a best gliding range is achieved in a steep turn is about 22% higher than the speed at which a best gliding range is achieved in a straight line. However the goal in a turn is not beat range but instead “minimum rate of descent per degree of turn”. There’s a mathematical analysis out there that shows the best bank angle is 45 degrees and the best speed for this just above the stalling speed in that turn, which is usually close to the same speed as the traditional “best glide ins a straight line” speed. So targeting that speed that most pilot know for their airplane, is close to optimal. My preference is to learn the pitch attitude at which the stall warning horn begins to sound, and use the on/off of the stall warning horn as an aural angle of attack indicator, as a guide.

A good way to stuff up the manoeuvre is to decide one has to make some particular spot and try to “shrink” the turn to do so. Once you have practice and understand that this fixed turn is the best you get from your aircraft and at what attitude it is achieved it becomes clearer that you do not adjust or improvise the turn according to what you see but make it as Pelmet says almost an instrument manoeuvre (even if conducting it visually). You simply assume the correct attitude, and ride it around until the field comes back into view. For a typical 70-knot 45 degree bank, a 180 takes 11 seconds, if I recall right. And those seconds seem long, until the field comes around in sight.

Once the field is in view in front of you roll out of the turn and finish the approach by lowering flaps and slipping, or not, as you might on any power-off landing.

To be honest, if I were to do such a maneuver, it would likely be if there were minimal other good options and I would not want to be close to the stall speed as I would consider it too risky, even for practice.

I should emphasize that for myself, the target isn’t necessarily the reciprocal of the departure runway. It could be the infield, parallel taxiway, roiling out early for a reasonable alternate location, etc. The reciprocal runway is only a nice option if things work out.

A self briefing/reminder of this before departure (such as stopping the turn back if it is appears to be getting too risky) seems likely to improve one’s odds of avoiding a stall/spin scenario.

[photofly]

...and I would not want to be close to the stall speed as I would consider it too risky, even for practice.

And this is where sane pilots who are happy to practice stalls in all sorts of scenarios above 2000 agl succumb to paranoia and group think. I don't know any single licensed pilot who can't handle a power off stall in a 45° bank with even a shadow of loss of control; yet suddenly, the thought of having to repeat the exercise closer to the ground turns everyone to jelly and custard.

The whole point of practicing a maneouvre at altitude is to gain confidence and understand it. When that is done, it is no more risky done at 500agl then at 3500agl.

Learning to manage risk is part of the package of being a pilot, and if you're going to think about getting the maximum performance out of your airplane to give yourself the best chance of surviving whatever emergencies life is going to throw at you, you had better get to the stage where you are confident with the approach to the stall in this scenario and no longer consider it "too risky".

[Big Pistons Forever]

After the engine failure at 400 feet, look inside at the instruments to target three things during the fairly aggressive pitch down……speed(best glide), bank(45 degrees), and finally a target reciprocal heading(turn into a crosswind).

Once the field is in view in front of you roll out of the turn and finish the approach by lowering flaps and slipping, or not, as you might on any power-off landing.

I think it is important to emphasize the aim of the turnback is not to get to the runway it is to get back to the airport environment, that is flat, level and hopefully unobstructed terrain. If you do 180 deg turn after takeoff you will be offset to one side of the runway and may be pointing at a row of hangars or other obstructions or not even be pointing inside the airport fence. I would suggest any turn back should be planned to be viable with a turn of at least 210 degrees and that amount of turn should be what is practiced. a turn of 210 degrees will usually end up with you pointing towards the middle of the airport and therefore an area likely to ensure that a controlled touchdown will not result in injuries.

[photofly]

For comparison purposes, a 70 knot turn at 45 degrees has a radius of 435 feet, so a pure 180 only displaces you 870 feet laterally; many airfields are quite a lot wider than that.

[pelmet]

...and I would not want to be close to the stall speed as I would consider it too risky, even for practice.

And this is where sane pilots who are happy to practice stalls in all sorts of scenarios above 2000 agl succumb to paranoia and group think. I don't know any single licensed pilot who can't handle a power off stall in a 45° bank with even a shadow of loss of control; yet suddenly, the thought of having to repeat the exercise closer to the ground turns everyone to jelly and custard.

The whole point of practicing a maneouvre at altitude is to gain confidence and understand it. When that is done, it is no more risky done at 500agl then at 3500agl.

Learning to manage risk is part of the package of being a pilot, and if you're going to think about getting the maximum performance out of your airplane to give yourself the best chance of surviving whatever emergencies life is going to throw at you, you had better get to the stage where you are confident with the approach to the stall in this scenario and no longer consider it "too risky".

Worked for me just fine from 400 feet without being on the edge of a stall. Obviously there is further performance to be maximized if one wants. I think the paranoia thing has worked well for me over the years.

[photofly]

If you maintain your wings-level best glide speed in a coordinated 45 degree banked turn without power, you are close to the edge of a stall. The fact that you might not have recognized being so is an indication that it’s not as much of an issue as you fear it is.

[pelmet]

If you maintain your wings-level best glide speed in a coordinated 45 degree banked turn without power, you are close to the edge of a stall. The fact that you might not have recognized being so is an indication that it’s not as much of an issue as you fear it is.

Thanks for your calculation that I am on the edge of a stall at 45 degree bank.

According to a table in this government link, a 45 degree bank increases the stall speed by 18%.

https://www.aviation.govt.nz/licensing- ... ll%20speed.

Looking at some notes I wrote down for a C172P, the stall speed is 44 knots. The best glide speed is 65 knots.
18% of 65 is approximately 8 knots. 44 knots plus 8 knots equals 52 knots. A full 13 knots below the stall speed(and that is at maximum weight which is rare for me although I was there on today's very enjoyable flight). So hardly on 'the edge of a stall'(which of course some people will no doubt define as much as possible in a way to try and emphasize their point).

Bottom line....I recognized that best glide speed is not on the edge of a stall at a 45 degree bank and I have no intention of trying to get any closer to the stall speed during a turnback after an engine failure. For me, that increases risk significantly.

It does bring up an interesting point though. If doing a turnback, one should keep in mind that they it would likely be beneficial to avoid pulling on the control column during the turn and if anything, be pushing a bit to slightly unload g.

[photofly]

You do have to be careful doing calculations in multiples of stalling speeds, and comparisons, to use calibrated airspeeds and then convert to indicated. Simply to multiply indicated airspeed by multiples is a rookie CPL flight test error.

The data in the POH for the 172N (suspect the P model is similar) is that in a 45 degree bank the calibrated stall airspeed varies between 59KCAS and 63KCAS (50 to 56 KIAS) according to cg and the best glide speed is 65KIAS (cg unspecified) which is about 66KCAS.

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So comparing 59-63 with 66, there isn’t as much margin as you think.

What’s happening is that airspeed indicator drops off rapidly and wrongly when the the airspeed is below 60 knots, as you’ll see in the calibration data in the POH, so the ASI wrongly gives the impression of a greater margin. You should definitely be hearing (or close to hearing) the stall horn, if you’re doing it right.

I take your point about it whether you are close to the stall depending on what you mean by close. Within five to six knots though, is pretty close, to me.

Given that the stall speed, the best glide speed, and the optimal speed for a turn are all determined only by different individual angles of attack, the airspeed for each will all scale at the same rate for different airplanes, cg positions, and weights. So the “close” relationship between the best glide and “best turn” airspeed, and its proximity to the stall airspeed, is pretty much a law of nature for all airplanes.

As to whether you should push to “unload the wing”: Well, no, not really. You should load the wing to 1.44g, neither more nor less. The g-load is determined by the bank angle only, and if you’re pulling less than 1.44g in a 45 degree coordinated turn you are accelerating downwards and not in a steady descent - and therefore pissing altitude away.

Given the stick-force-per-g figure for the 172 (I think it’s about 12lbs/g) you should be pulling back steadily with about 5lbs force through the duration of the turn, if you were trimmed for best glide wings level. Or you can trim back a bit further, instead.

However - I have always found it easier and quicker as well as more accurate simply to fix the horizon position in the right place than worry about pushing or pulling just this much or that much, or in fact whether I’m doing either, as the correct horizon position doesn’t depend on where the elevator trim is set like the elevator force does.

[pelmet]

As to whether you should push to “unload the wing”: Well, no, not really. You should load the wing to 1.44g, neither more nor less. The g-load is determined by the bank angle only, and if you’re pulling less than 1.44g in a 45 degree coordinated turn you are accelerating downwards and not in a steady descent - and therefore pissing altitude away.

I prefer 1.43g

[photofly]

Sorry, yes, 1.414g - skipped a digit!

[CpnCrunch]

Just to be clear for PPL and CPL students the SOP is EFATO below 1000 AGL the SOP is immediate pitch down to establish the attitude which will hold best glide speed and turn only enough to avoid the worst obstacle. I do not teach turn backs to PPL and CPL students. I have never taught the turn back exercise but I suppose could one day if asked. The student would have to have to be a 5 percenter with respect to general handling skills before I would consider it.

I don't feel this is the best advice. Taking YYJ as an example, my SOP is to land straight ahead under 500ft (about 435ft AGL), or turn back above 500ft. I just tried a few examples in FSX today, and at 400ft it's very easy to land and stop just beyond the end of the runway on the grass. At 500ft you'll end up in the water if you try that. But: doing a 180 degree turn at 35 degrees of bank from 500ft it's very easy to land on the grass in the middle of the runways, and that shouldn't tax the average PPL. I don't think the ground-rushing effect at 400ft AGL is any worse there than during the base-to-final turn, or a precision 180.

[AirFrame]

I don't feel this is the best advice. Taking YYJ as an example, my SOP is to land straight ahead under 500ft (about 435ft AGL), or turn back above 500ft. I just tried a few examples in FSX today, and at 400ft it's very easy to land and stop just beyond the end of the runway on the grass. At 500ft you'll end up in the water if you try that. But: doing a 180 degree turn at 35 degrees of bank from 500ft it's very easy to land on the grass in the middle of the runways, and that shouldn't tax the average PPL.

At YYJ, you also have diagonal runways on either side of you when you depart from any runway. I departed from 09 for a local flight and found I had a spiked EGT reading. I turned crosswind and called the tower to say I was changing to a circuit to a full stop they asked if I had a problem, I told them I had an unexpected high temperature reading, and they offered me 32 for landing. My initial reaction was to fly a normal circuit like everyone else, but I quickly decided that since I had made the decision to return to the airport, it was silly to fly farther than I needed to do that. I accepted, cut power, and continued the turn around to line up on 32. I don't think I got more than 500' up, and was never above flap speed so I just put all flaps out on my turn to line up with 32. I did end up touching down about half way down 32, with a slight tailwind, but had no trouble stopping in the remaining distance. I don't recall if any traffic was redirected to make room for me or not.

(and it just turned out to be a failed EGT probe)

[Aviatard]

If you’re going to lose power x seconds after takeoff, I’d rather have the extra height from a best rate climb, than be lower and closer from a best-angle climb.

And thw extra 15 knots or so of airspeed will really help in those seconds of deciding what to do - you’ll lose a chunk of extra height getting to a best glide speed from Vx than from Vy. In fact in most airplanes best glide is slower than best climb rate, so if you’re prompt with a pitch adjustment you don’t need to lose any height at all, losing the engine at Vy.

But I haven’t done any sums to prove that that’s the better option.

It might also depend on how much runway a particular type uses on takeoff; if you start your climb at midfield then you have a distance advantage “getting over the fence” on the way back vs an aircraft that breaks ground right at the departure end of the runway.

You might find this report interesting:

http://jeremy.zawodny.com/flying/turnback.pdf

[photofly]

You might find this report interesting:

http://jeremy.zawodny.com/flying/turnback.pdf

That's the paper which leads me to believe that a 45° bank turn, just above the stalling speed, is optimum. From the conclusion section:

The model shows that optimum conditions for returning to the
departure runway result from climbing at V_max , executing a gliding turn through a 190-220 
heading change, using a 45 bank angle at 5% above the stall velocity in the turn using a
teardrop shaped flight path.

[Big Pistons Forever]

The model shows that optimum conditions for returning to the
departure runway result from climbing at V_max , executing a gliding turn through a 190-220 
heading change, using a 45 bank angle at 5% above the stall velocity in the turn using a
teardrop shaped flight path.

On speed and you are a hero, get as little as 3 knots slow ( 5% of a C 172 stall speed) and you have the classic stall/spin turnback fatal accident......

[photofly]

The model shows that optimum conditions for returning to the
departure runway result from climbing at V_max , executing a gliding turn through a 190-220 
heading change, using a 45 bank angle at 5% above the stall velocity in the turn using a
teardrop shaped flight path.

On speed and you are a hero, get as little as 3 knots slow ( 5% of a C 172 stall speed) and you have the classic stall/spin turnback fatal accident......

No, you don’t.

As long as you keep the ball centred, a power-off accelerated stall means little more than that you descend a little faster than you need to. Given that you’re short on altitude, that should be avoided, but it doesn’t lead to catastrophe. Relax the back pressure to recover the normal rate of descent.

You won’t spin unless you grossly misapply the rudder, just like you don’t spin out of a wings-level power-off stall unless you grossly misapply the rudder.

The purpose of practice at altitude is to be able to recognize and approach the stall without actually stalling. It’s considerably easier than (level flight, powered) slow flight, which every private and recreational pilot can manage.

What you cannot do is try to rudder it through a flat turn. Again the purpose of practice at altitude is to make sure that your steep gliding turn is coordinated.

[Big Pistons Forever]

On speed and you are a hero, get as little as 3 knots slow ( 5% of a C 172 stall speed) and you have the classic stall/spin turnback fatal accident......

No, you don’t.

As long as you keep the ball centred, a power-off accelerated stall means little more than that you descend a little faster than you need to. Given that you’re short on altitude, that should be avoided, but it doesn’t lead to catastrophe. Relax the back pressure to recover the normal rate of descent.

You won’t spin unless you grossly misapply the rudder, just like you don’t spin out of a wings-level power-off stall unless you grossly misapply the rudder.

The purpose of practice at altitude is to be able to recognize and approach the stall without actually stalling. It’s considerably easier than (level flight, powered) slow flight, which every private and recreational pilot can manage.

What you cannot do is try to rudder it through a flat turn. Again the purpose of practice at altitude is to make sure that your steep gliding turn is coordinated.

I guess that is where we will have to agree to disagree. The turnback means in a high stress emergency you have to fly nearly perfectly. I honestly think that if you look at the experience level of pilots in turn back fatal accidents, I think many of the pilots could fly a good coordinated on speed turn back when practicing at altitude. Unfortunately that practice did not translate to success when you pretty much have to fly perfectly or you risk loosing control of the aircraft or aircrafts flight path with very little time or altitude to recover.

As I have said before I worry about negative learning and that practice at altitude does not IMO, necessarily translate into success when you have to do it for real. The penalty for trying the turn back and messing it up will be severe, as I readily admit, can going straight ahead after an EFATO. The difference is a much higher probability that you will hit under control if you just push the nose down only turning with a moderate bank angle enough to avoid the worst obstacle if the engine fails right after takeoff. The accident data is clear. The airplanes attitude and speed when it hits is the primary determinant of no fatalities. It is more important than what you hit.

[photofly]

On speed and you are a hero, get as little as 3 knots slow ( 5% of a C 172 stall speed) and you have the classic stall/spin turnback fatal accident......

No, you don’t.

As long as you keep the ball centred, a power-off accelerated stall means little more than that you descend a little faster than you need to. Given that you’re short on altitude, that should be avoided, but it doesn’t lead to catastrophe. Relax the back pressure to recover the normal rate of descent.

You won’t spin unless you grossly misapply the rudder, just like you don’t spin out of a wings-level power-off stall unless you grossly misapply the rudder.

The purpose of practice at altitude is to be able to recognize and approach the stall without actually stalling. It’s considerably easier than (level flight, powered) slow flight, which every private and recreational pilot can manage.

What you cannot do is try to rudder it through a flat turn. Again the purpose of practice at altitude is to make sure that your steep gliding turn is coordinated.

I guess that is where we will have to agree to disagree. The turnback means in a high stress emergency you have to fly nearly perfectly.

That's not a characterization I agree with. You have to fly 'ok', and avoid a couple of obvious errors, but "nearly perfectly"? No, I don't think so.

As I have said before I worry about negative learning and that practice at altitude does not IMO, necessarily translate into success when you have to do it for real.

Right. But one doesn't only practice it at altitude. One works through the manoeuvre at altitude until it's smooth, then one practices it at a realistic height, after takeoff, as a planned manoeuvre, without an emergency. I did describe both those elements, when you asked me how one might learn such a manoeuvre, and they're both important. So when an emergency happens one is both competent with the manoeuvre itself and how to apply it down low without panic.

What we disagree about, I suppose, is to what extent a pilot (even a low time pilot) should expect to expand and improve their competences. Flying when everything is working fine isn't the challenge of being a pilot, is it? Being in charge of an airplane means one must learn to make the most of the situation one finds oneself in when those circumstances are less than ideal. That's a moral imperative, not a "wouldn't it be nice if." It's a responsibility - to ones self, and ones passengers, which is not met in this circumstance by trimming for 70 and climbing in the back with the baggage. PIC is pilot-in-command, not passenger-in-command, after all. In good times, and in bad.

[CpnCrunch]

No, you don’t.

As long as you keep the ball centred, a power-off accelerated stall means little more than that you descend a little faster than you need to. Given that you’re short on altitude, that should be avoided, but it doesn’t lead to catastrophe. Relax the back pressure to recover the normal rate of descent.

You won’t spin unless you grossly misapply the rudder, just like you don’t spin out of a wings-level power-off stall unless you grossly misapply the rudder.

The purpose of practice at altitude is to be able to recognize and approach the stall without actually stalling. It’s considerably easier than (level flight, powered) slow flight, which every private and recreational pilot can manage.

What you cannot do is try to rudder it through a flat turn. Again the purpose of practice at altitude is to make sure that your steep gliding turn is coordinated.

It depends on the plane. You don't need to misapply the rudder on a C150 to enter a spin...even the slightest yaw will cause a wing drop during the stall.

With a 45 degree turn there is a lot of back pressure required, as you mentioned above. There are a lot of ways in which airspeed can decrease quickly if you're not paying attention. Practicing at altitude is quite different from doing it a few hundred feet off the ground when you're trying to avoid hangars, trees, etc. and trying to land somewhere reasonable, along with the stress of the engine failure. Yeah you can increase airspeed to give a margin over the stall, but still a lot of backpressure required for 45 degree turn, and possibility that airspeed could drop rapidly. For that reason I think it's better to just do a 35 degree turn, which is a lot less risky in this situation.

[photofly]

35 degrees works too, and you don't lose a lot of extra altitude. The radius of turn is about 40% bigger, though. That may be good, or bad, depending.

You don't need to misapply the rudder on a C150 to enter a spin...even the slightest yaw will cause a wing drop during the stall.

While I don't question your own experience, my experience of the difficult-to-fly C150 is that it, too, is not more particularly prone to spin entry than other slow single-engine types. It's certainly not more difficult to maintain in slow flight, which is all we are talking about here.

There are a lot of ways in which airspeed can decrease quickly if you're not paying attention.

I prefer to fly the attitude rather than fuss about exactly how much back pressure. If you fly attitude, then you're ahead of any airspeed excursions.

[CpnCrunch]

35 degrees works too, and you don't lose a lot of extra altitude. The radius of turn is about 40% bigger, though. That may be good, or bad, depending.

Radius is 23% bigger (comparing 45 degrees at 70kt vs 35 degrees at 65kt).

While I don't question your own experience, my experience of the difficult-to-fly C150 is that it, too, is not more particularly prone to spin entry than other slow single-engine types. It's certainly not more difficult to maintain in slow flight, which is all we are talking about here.

A 150 certainly a lot more liable to drop a wing in a stall than a 172, and that's not just my experience. The 172 has a much larger amount of washout, so it would be quite odd if you experienced a similar stall characteristics on it to a 172.

I prefer to fly the attitude rather than fuss about exactly how much back pressure. If you fly attitude, then you're ahead of any airspeed excursions.

You still need to look at your airspeed.

[photofly]

You still need to look at your airspeed.

I take your point, but you can do quite well with just attitude and the stall warning horn on/off. That compensates for weight and cg automatically too. How much time do you spend looking at the ASI practicing slow flight?

[CpnCrunch]

I take your point, but you can do quite well with just attitude and the stall warning horn on/off. That compensates for weight and cg automatically too. How much time do you spend looking at the ASI practicing slow flight?

If the stall warning is such a panacea in this situation, why are there still so many stall/spin accidents after engine failures?

[photofly]

I take your point, but you can do quite well with just attitude and the stall warning horn on/off. That compensates for weight and cg automatically too. How much time do you spend looking at the ASI practicing slow flight?

If the stall warning is such a panacea in this situation, why are there still so many stall/spin accidents after engine failures?

One can equally well ask why isn’t the airspeed indicator such a panacea. I mean, there it is in front of you, all you have to do is look at it.

But are there that many such accidents? And how many is that many, anyway? Are there any at all, among pilots who are properly prepared?

If there are among the unprepared, it may be because the stall warning horn doesn’t (as yet, as far as I know) reach out from behind the instrument panel and give your nuts a hard squeeze when your angle of attack rises too high. You actually have to listen for it, listen to it, and understand what it’s telling you, which is the point of practice, isn’t it?

[Squaretail]

If there are among the unprepared

If they’re unprepared, it’s usually because they were taught wrong. Two vectors here, first every once in a while an enterprising instructor decides that power is the first action to get out of a stalling situation, and we’ll if there is no power, we’ll then all is lost. Second, I see a lot of stall training that is incredibly timid that doesn’t show students actual stalls, but recoveries at the “approach” to the stall. The horn might squeak, stick goes forward. Slow flight is taught minimally at the barest indicating of the regime. The idea one may have to fly the airplane with the horn on constantly and maybe louder than they have ever previously experienced would be a terror to pilots trained in such a manner, since they have also been taught that the stall itself is instant death.