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Re: 180 Degree Turn

 

I have a few comments and quibbles relating to the article by Jack Dueck in the April 2008 edition of COPA Flight. As Jack's diagrams illustrate, this is not a 180 degree manoeuvre but rather anywhere from 260 to 360 degrees to get turned around and aligned with the runway.

Why use a standard rate turn? This eats up precious time and a lot of altitude and real-estate. As the article shows, it will take two minutes to do a 360 degree turn at standard rate and lose up to 1,200 feet of altitude in Jack's aircraft. A more aggressive turn (practiced at altitude before applying it to a real emergency) will lose less altitude and use less real-estate to accomplish which translates to less turning required because you won't be displaced as far off the runway centerline.
As a matter of fact, if you hold runway heading (as required by most towered airports) rather than crabbing into a crosswind to maintain runway track and turn into the wind on your turn-back, even less turning will be required with less altitude lost.

Now, I know, using a 45 to 60 degree bank angle seems scary because it is drummed into pilots that increased bank angles equate to increased stall speed, but that only applies if you are trying to complete a level turn. An aggressive turn-back manoeuvre will not result in a stall if the pilot maintains 1G in the turn while giving up altitude to maintain best glide speed and in the end lose much less altitude than if he were to do a standard rate turn as this article suggests.

Every aircraft will be different, but I have practiced this manoeuvre at altitude and lose no more than 400 feet doing a 360 degree turn using 45 degree of bank in a Piper Comanche 180 with the prop pulled back to coarse pitch to minimize drag.
Fixed gear, fixed pitch prop aircraft will have more drag and lose more altitude than this, but you won't know unless you practice it at varying bank angles to see what works best for your aircraft and then add in a fudge factor.

In most of the light aircraft that COPA members fly the best rate of climb speed will be pretty close to the best glide speed and unless a pilot aggressively pushes forward on the yoke (or stick) after an engine failure on take-off or climb-out he is not likely to get to "B" in the diagram before the aircraft hits stall speed. I believe it is of the utmost importance to emphasize the need for that aggressive push to maintain speed and hence control.

Then there's the question of whether a turn-back manoeuvre, even if done perfectly with minimal loss of altitude (say 600 or 700 feet) will even make the runway at all or end up landing short. I haven't done the math, but I believe the typical general aviation aircraft is going to have to be using at least a 3,000 to 4,000 foot runway to even have the hope of making the runway if the pilot lifts off at the 1,000 foot mark and has an engine failure at 1,000 ft AGL. As always, the wind will play a huge roll and this would be a good exercise for a flight simulator.

 

HUBERT WREN

Peterborough ON

 

ed. Your points are well taken, and I am generally in agreement with your stated comments. I do think however, that I should clarify my position with regards to the article and your comments.

1. Let's not quibble about whether the pilot proceeds through 150, or 180, or even 360 degrees in effort to get the aircraft traveling in the opposite direction to the take-off run. If and when he/she is traveling in the opposite direction, they have effectively made a 180 degree reversal to their original flight path.

2. I believe that under the pressure of an engine-out on take-off, a novice pilot should not be attempting to be aggressive in any flight manoeuvre. Any pilot under pressure should try to stay within the scope of his/her flying training and experience. Someone once said, "Under pressure a pilot's brain turns into the size of a small pea, and rolls out of one of his/her ears."

3. I believe most pilots climb out at something higher than Vy in order to provide additional cooling to the engine. I certainly agree that if flying a fast glass, high performance aircraft at Vy, anytime the engine quits you had better get that stick forward quickly because your airspeed will decay quickly in that climb attitude.

4. The intent of my comments, (that I tried to clearly convey with the flight exercise) was to establish once and for all, the idea of a turn-back on take-off after an engine failure was not at all a sure thing. And I sincerely hope pilots will try this manoeuvre at a safe altitude to see for themselves the difficulty and the questionable certainty to be expected. And then with this understanding, they can try the more aggressive approach that you recommend in a safer (higher) environment.
Again, "Under an emergency your brain will not ascend to the challenge, but descend to the level of training."

I very much value your comments. I believe this type of dialog can only add to the safety and enjoyment of our sport.

JACK DUECK EAACC