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Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 3:30 pm
by Hedley
BPF: Have no fear, I do not recommend that low-time pilots attempt either surface-level inside loops, or the turnback :wink:

However, I do take issue with claims that the turnback is aerodynamically impossible. This is simply not true.

Is the turnback wise to attempt without training? No. Would it be wise for a low-time PPL with no tailwheel experience to jump into a single seat Pitts and try to teach himself aerobatics and landings? No.

But that doesn't mean that the Pitts is incapable of aerobatics, or a successful landing.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 3:36 pm
by Big Pistons Forever
Hed

You have not answered my question.

Do you provide any specific guidance with respect to when, when not to attempt a turn with respect to the EFATO case ?

Again not looking to pick a fight, just curious.

One thing I find interesting is the majority of instructors I have talked to think my 1000 AGL prohibition on turnbacks is too conservative.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 3:48 pm
by Shiny Side Up
No one can argue whether or not a light trainer is capable of it - it certainly is.
Not all the time, not under all conditions. The math simply doesn't work, and in my experience nor does it by practice. It also isn't always the best choice even when the numbers do work. Keep in mind that I'm also not contending that it is aerodynamically impossible to make the turn safely, but that it is relevant to the climb performance / glide performance of the aircraft.

It could be that I'm a crappy unskilled pilot, hence the invitiation still stands.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 5:12 pm
by Hedley
the majority of instructors I have talked to think my 1000 AGL prohibition on turnbacks is too conservative
Given that a large percentage of the commercial pilot flight test candidates struggle with the incredibly simple power-off 180 degree landing from downwind, is your prohibition really conservative?
climb performance / glide performance
Now you're nibbling at what matters :wink:

Hint: the 210 degree descending steep turn (180 won't do it) is actually pretty simple, and doesn't require very much altitude.

What can be difficult, is making it back to the departure end of the runway, because most aircraft glide steeper (power off) than they climb at full power. Most aircraft are horrendously underpowered.

Here are some tips to help you make the runway:

1) climb at Vx (no one ever does) to 400 AGL
2) headwind helps. Yes, you will land with a tailwind. Deal with it
3) turn into any crosswind, NOT away from it, to reduce your turn radius and distance to glide
4) long runways help. 3,000 foot runway can be tricky. 10,000 foot runway is a cinch

What troubles me is that so few people understand something so simple. This isn't rocket science. There are many things that are more difficult to do in an airplane, such as a perfect, no-torque, minimal radius hammerhead with a metal prop and a short fuselage and no horizon.

My apologies if my technical position is heresy and blasphemy to the Established Order (tm). I tumble differently than everyone else, too:

http://www.pittspecials.com/movies/tumble.wmv

I am just a simple pilot and engineer who worships at the Church of the Internal Combustion Engine, where our litany is the Four Strokes: Suck/Squeeze/Bang/Blow.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 5:25 pm
by FlaplessDork
I've been successful with the turn back in training many times. Conditions have to be right and the maneuver flown to perfection. With a good tailwind you'll eat up runway and tires. That being said, the average private pilot may not pull it off and I have witnessed first hand the results of attempting the turn back. Watched a Murphy Moose come up 1/2 mile short when his engine quit.

Personally, I don't like the turnback. Survivability goes up if I go straight ahead.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 6:04 pm
by Hedley
come up 1/2 mile short
See above. His airplane did not explode with infinite G during the turnback - he had trouble making it back to the departure end of the runway.
I don't like the turnback
Then for God's sake don't do it. One of the most important lessons you can teach new pilots is that if you don't like it, don't do it, regardless of whether or not it is legal, fashionable amongst your peers, etc.
With a good tailwind you'll eat up runway and tires
If your biggest problem after an engine failure & turnback is that you flat-spotted a tire, it's still a good day.

Re: Impossible Turnback After Takeoff

Posted: Mon Nov 22, 2010 6:24 pm
by FlaplessDork
Hedley wrote:
come up 1/2 mile short
See above. His airplane did not explode with infinite G during the turnback - he had trouble making it back to the departure end of the runway.
I don't like the turnback
Then for God's sake don't do it. One of the most important lessons you can teach new pilots is that if you don't like it, don't do it, regardless of whether or not it is legal, fashionable amongst your peers, etc.
With a good tailwind you'll eat up runway and tires
If your biggest problem after an engine failure & turnback is that you flat-spotted a tire, it's still a good day.
Maybe I didn't get my point across in my last post. Just because I have been successful when I have tried the turnback myself during my own practice, doesn't make it the safest option. I was unsuccessful quite often as well. The most successful action would be straight ahead. I only taught going straight ahead, and would only go straight ahead if the engine really quit.

Re: Impossible Turnback After Takeoff

Posted: Tue Nov 23, 2010 10:42 am
by trey kule
It seems to be the Xmas season and the mods are being very generous in their latitude, so I have self edited my post.

Re: Impossible Turnback After Takeoff

Posted: Tue Nov 23, 2010 1:50 pm
by Shiny Side Up
Hedley wrote: What can be difficult, is making it back to the departure end of the runway, because most aircraft glide steeper (power off) than they climb at full power. Most aircraft are horrendously underpowered.
This is what I'm getting at. In truth I have people try the turn-back on an occasional basis when I check them out on aircraft. Usually when they do I'll say they're usually American and come from somewhere warmer and more civilized. While there is the fact that these fellows are usually out of practice - though one was a CFI and worked traffic patrol down in San Francisco. We pull the power around 500-700 AGL on climb out, they make a magnificent turn around (though if they're American they occasionally try to put it into a spin...) and realise there's no where to go. Best glide speed, they're not making the runway. At this point I'll usually point out to them that its going to really hurt when we hit that road allowance which is perpendicular to our landing path. On the plus side its a good demonstrator for people who move here what density altitude does to performance. The other point is that if you're not intimately familiar with the terrain, people often have poor judgement on how far away they are from the runway that they're intending on gliding back to. The 172 isn't the only plane I regularly fly either though, the point is really made clear in the 150 or the Cherokee 140 where on some hot days (density altitude on the ground being up around 7-8000') you're five miles from the runway by the time you break 1000' AGL (max glide in the Cherokee is about 1:10 or so they claim) at 1000' AGL you're about 30,000' feet from the runway - think fast, can you make it back?
Here are some tips to help you make the runway:

1) climb at Vx (no one ever does) to 400 AGL
Certainly does, but how much it helps wanes pretty quickly with an increase in density alt. More importantly, most people don't do it in their usual take off. Lastly in some light planes there is no real difference between the numbers. Weight also plays a big factor in climb performance. How often do people demonstrate a turn back when they're full?
2) headwind helps. Yes, you will land with a tailwind. Deal with it
3) turn into any crosswind, NOT away from it, to reduce your turn radius and distance to glide
Ideally the take off with the headwind makes it so you extend your glide distance back and is the optimum condition for the turn back. A crosswind however hurts a lot more than one would think and is often an unknown at altitude. I don't know how many times I've seena 5-8 Kt wind on the ground with a 20-30Kt wind at around 500 AGL. Unless you're operating out of an airport with more than one runway, a majority of your take offs are going to be with some sort of crosswind component. Dealing with a tailwind on the landing is really trivial when it comes to this - unless the headwind on take off was so strong - in which case it might have been preferable to land straight ahead into it if you got lots of runway. Taking off with a tailwind though makes the turn back a definite no go unless you got lots of ashpalt to get back to - why would one take off with a tailwind one might ask? Too bad Larry isn't still here to explain.
4) long runways help. 3,000 foot runway can be tricky. 10,000 foot runway is a cinch
Maybe its just me, but a majority of the runways I use are 3,000' long or less. Some of them are even grass. Some even have interesting obstacles and a few are sloped. I don't view them as unsafe, though they certainly aren't ideal for an EFATO scenario.
What troubles me is that so few people understand something so simple. This isn't rocket science. There are many things that are more difficult to do in an airplane, such as a perfect, no-torque, minimal radius hammerhead with a metal prop and a short fuselage and no horizon.
What I take issue with when it comes to the EFATO turn back is how it is often presented as "if you only trained to do it, you can accomplish it all the time." Often pilots who have done it at one time (as demonstration or for real), will use this as proof that its a golden hammer solution and focus on the reward of doing it successfully.
My apologies if my technical position is heresy and blasphemy to the Established Order (tm).
Its not the technical position I have issue with, its all about presentation, just like Mr. Shiff. The whole story isn't being told. A lot of back-patting often goes on with how well someone pulls off this manuever and a lot of it goes to how awesome the pilot was rather than whether or not he was concious of the factors that allowed him to do it. Too often when reading about these occurances - like Mr. Shiff's - you get the idea that they really had no idea if they were going to be successful when they decided to do the manuever, it was a gamble rather than a calculated plan.

Personally I'd like to see some numbers on that - though we already do have some. Every crash where we can see someone turned back and didn't make it is where someone gambled and lost - whether you think that it was just because they weren't trained/practiced enough in doing it, or whether they had no chance of gliding to the runway from their position, it matters not. Of those who were successful it would be interesting to see of that number how many actually had previously practiced the manuever or made any sort of climb/turn/glide figure.

Re: Impossible Turnback After Takeoff

Posted: Wed Nov 24, 2010 3:19 pm
by JAHinYYC
I attended the inaugural flight instructor refresher course offered at Seneca College in the Fall of 2007 along with 20 or so instructors of various classes (I-IV).

One of our evenings was spent doing scenerio based training exercises using thier nifty suite of flight simulators.

One of the exercises was the engine failure and turn back scenerio. With a swarm of TC Inspectors watching each of us strapped on the Bonanza sim they had. The deal was you took off in the sim and climbed runway heading. At an altitude of the pilot's choosing (told to the sim operator in advance) the engine would fail and you were supposed to turn 180 degrees and dead stick it to the runway.

My first attempt was straight ahead climb out to 800' when the engine died, I pulled the prop full coarse and turned. Still landed short of the departure end.

Believe it or not the second attempt was worse climbing to 1200' with a 15kt headwind.

I heard that only one guy made it back to the runway that evening.

I don't understand why you would take a relatively simple forced approach scenerio and introduce the possibility of a stall spin at low level by trying to turn back.

Re: Impossible Turnback After Takeoff

Posted: Wed Nov 24, 2010 3:40 pm
by HavaJava
JAHinYYC wrote:I pulled the prop full fine
You mean full course?

Re: Impossible Turnback After Takeoff

Posted: Wed Nov 24, 2010 7:34 pm
by cgzro
I don't understand why you would take a relatively simple forced approach scenerio and introduce the possibility of a stall spin at low level by trying to turn back.
No matter what a pilot decides to do he or she should be able to make evasive turns at or near stall without spinning and I'd hope that a well trained pilot's decision not to turn back is not based on a fear of a stall spin but rather on rational assessment of the best within gliding distance option.

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 6:21 am
by Hedley
Odd. I found it quite easy on the Seneca college Bonanza sim to do a successful turnback, when I did the instructor refresher course there.

I am NOT advocating that every yahoo out there attempt the turnback for real. What I am asserting is that is aerodynamically possible, if the maneuver is flown optimally, which is rarely done.

As far as stall/spin during the turnback ... I am fascinated that you didn't have any problem with it, in your many attempts in the sim. This is because angle of bank is not inherently evil, as so many instructors teach. It's all about the wing, and it's angle of attack to the relative wind.

Since you are not attempting to maintain altitude during the turnback, you can actually use lots of bank . As I mentioned earlier, I frequently use 90 degrees of bank, sideslipping on final, and my airplane does not explode with infinite G as is taught, because I am not attempting to maintain altitude, and the ball is not in the center.

One very simple maneuver I perform at airshows is sustained knife-edge flight. Drive down the runway with 90 degrees of bank, and altitude is maintained this time. Again, frowns may appear, because I am not experiencing infinite G as is taught, even though I am maintaining altitude with 90 degrees of bank. Hint: the ball is NOT in the center.

Pop Quiz: what is the wing's AOA as I drive down the runway at a constant altitude with 90 degrees of bank? Am I flirting with a stall/spin?

PS: my apologies if I am not taking enough of a "motherhood and apple pie" approach. As an engineer and airshow pilot, I am far more technically interested in what an airframe is aerodynamically actually capable of, rather than preaching established dogma. You probably don't want to know how I deal with turbulence, either.

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 8:21 am
by . ._
I found this video.

Nice job!


Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 9:33 am
by trampbike
Hedley wrote: Pop Quiz: what is the wing's AOA as I drive down the runway at a constant altitude with 90 degrees of bank? Am I flirting with a stall/spin?
Wings are at 0 degree AOA, hence they produce no lift, otherwise you would be turning.
I guess you could stall the fuselage in some conditions, but I don't know if any airplane has enough rudder authority.

Hedley wrote: You probably don't want to know how I deal with turbulence, either.
I do.

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 9:35 am
by Big Pistons Forever
Hed

There is plenty of AOA in your knife edge pass it just is not in the usual place :wink:

The issue to me is part of a tougher problem set. What you as the instructor can do is ultimately meaningless, the only thing that matters is what the student can do. I think I am a reasonably good stick but I also have 30 + times the number of flying hours of the CPL student. I think it is reasonable to conclude that threre are going to be manoevers which I can competantly execute every time, but are beyond the experience and judgement of a low(er) time pilot.

So the question I struggle with is "what is the point that a pilot could move from a rote response (ie no turn back below 1000 ft AGL under any circumstances) to a more nuanced approach that allows for increased pilot skill and judgement".

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 9:39 am
by Hedley
Wings are at 0 degree AOA
Excellent!
hence they produce no lift
Yes, but that is only true because they are (rare) symmetrical wings.

Bonus question: What would happen if you tried to fly an aircraft with a flat-bottom wing (eg Pitts S-1C or S-1D) in knife edge flight? Hint: Look at the Cl curve.
deal with turbulence
I do.
Sorry, I am sure I have already crossed the line with the Powers That Be (tm) over my position on the turnback, and have said too much. Telling the truth in public is a very dangerous and expensive habit.

In the context of what has been mentioned in this thread, you can probably figure it out on your own.
what is the point that a pilot could move from a rote response
Excellent question. At the risk of more public heresy, the answer does NOT lie in total flight time. 10,000 hours of straight and level time, spent on autopilot, is NOT going to improve the skills and judgement required for the turnback.

Many years ago, I was shocked to learn that the Russian aerobatic pilots, who generally always kick our *sses in the Unlimited Category at the World Aerobatic Championship (WAC), only practice 40 hours before the WAC.

Now, 40 hours doesn't sound like very much, does it? Heck, a Canadian can't get his PPL in 40 hours, let alone get good enough to win in Unlimited at the World level. What's the difference?

Good training is the difference. Those Russian pilots would fly 120 twenty minute flights of a carefully critiqued unlimited category aerobatic sequence.

Speaking of training ... ever seen an F-18 at a Canadian airshow? Food for thought: even though he is capable of performing low-altitude aerobatics in a fighter jet, the F-18 demo pilot probably doesn't have enough hours in his logbook to fly a King Air straight and level in the civilian world. Hm.

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 10:50 am
by trampbike
Hedley wrote: Bonus question: What would happen if you tried to fly an aircraft with a flat-bottom wing (eg Pitts S-1C or S-1D) in knife edge flight? Hint: Look at the Cl curve.
I guess you would have to push foward a little bit on the stick

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 11:50 am
by JAHinYYC
HavaJava wrote:
JAHinYYC wrote:I pulled the prop full fine
You mean full course?
(embarassed)

Yes. That is what I meant.

Re: Impossible Turnback After Takeoff

Posted: Thu Nov 25, 2010 11:56 am
by HavaJava
Lol, no worries...I'm embarrassed for spelling "coarse" wrong!