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Note before reading further that I'm asking this question purely on theoretical grounds, though you are more than welcome to talk about practical aspects as well.

Now, my question. It's common knowledge amongst many pilots that turnbacks are one of the least safe methods of attempting to survive an engine failure in a single engine aircraft. However, is it actually possible at all to turnback an aircraft to return to the airport perimeter or the runway? How much of it is simply pilot error in executing a possible manoeuvre, as opposed to pilots thinking that they can pull something off that is just impossible, no matter what?

For the purposes of this question, we shall assume the following:

  • there is only one runway, so a reciprocal turn is required (we shall assume 210 degrees)
  • the aircraft has a flaps up stall speed at MTOW of 75 knots
  • the aircraft has a best glide ratio of 1:12 at 100 knots

Alternatively, if you have any other information that is more akin to a real aircraft, you can use that in lieu of this information.

Sources or an explanation as to why this it is or isn't impossible would be appreciated in your answers.

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    $\begingroup$ This question is too general unless you include what altitude you're at when the engine fails, how many degrees you need to turn back to in order to line up with a runway (which could be a different one than you took off from), and how many feet you will lose in turning that far. $\endgroup$
    – mah
    Jan 9, 2014 at 11:49
  • $\begingroup$ @mah: well, if I knew exactly how much the aircraft would descend, then there'd be no point in asking, but does that help a bit? ;) $\endgroup$
    – Qantas 94 Heavy
    Jan 9, 2014 at 12:15
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    $\begingroup$ Anecdotal: When doing my PPL training in SoCal another trainee had an engine failure on takeoff, at roughly 400ft. The instructor took control and turned back and landed with a tailwind. So impossible: no. Recommended: Probably also no. I'd still opt for a safe patch in front than attempt a turnback! $\endgroup$
    – Jamiec ♦
    Jan 9, 2014 at 12:45
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    $\begingroup$ @SSumner: while turning back, you're going to be slightly to the side of the extended runway centreline (you'd just be parallel). To reach the runway itself, you need to turn more than 180 degrees to get back to the centreline before you reach the actual runway. $\endgroup$
    – Qantas 94 Heavy
    Mar 12, 2014 at 13:02
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    $\begingroup$ which is why we always turn into the prevailing crosswind. $\endgroup$
    – rbp
    Jan 13, 2016 at 13:40

10 Answers 10

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Nobody mentioned the theory so far, so I'll try to fill in.

Disclaimer: The below calculations and estimates are based on what I know about the physics involved. I don't know whether they are actually mentioned in pilot operating handbook of any aircraft.

To successfully turn back, you after climbing at best climb rate, when the engine quits you push down, execute the turn at suitably slightly higher speed to maintain the angle of attack and glide back.

The rate of climb is thrust/weight minus lift/drag, the glide rate is just lift/drag.

Glide rate in the turn is higher by factor depending on the bank angle (coordinated turn; uncoordinated turn is always worse). Calculating best glide rate turn leads to bank angle should be around 45°, speed should be about 19% higher to maintain best glide angle of attack and about 41% higher rate of descent than in straight glide. According to the article linked in the other answer, flying at just above stall speed (which is also 19% higher than in straight flight) should be better due to tighter circle despite worse lift/drag ratio.

The radius, and thus length of the turn of course depends on speed. At 110 knots (true speed, not indicated) the turn will take about 1.4 nm, at 160 knots it will already be about 3 nm. At 60 knots it will only be 0.42 nm. Since you need to maintain indicated speed, the true speed will slightly increase with altitude.

So for the turn back to be possible the plane needs to have sufficient power to climb faster than it will descend in the glide and you have to be high enough to allow for the extra gliding distance (which due to higher rate of descent corresponds to even longer straight glide).

All or most planes will have sufficient thrust at sea level to climb faster than they descend in glide. But since thrust decreases with altitude and temperature, if your departure point is high or warm enough, it may no longer be the case.

Even if the thrust is sufficient, the distance between climb and glide profile starts at zero on lift-off and will only become sufficient to cover the extra miles in the turn above some altitude. The altitude depends on many factors mentioned above.

It's not reasonable to try it without knowing what altitude is needed for it at current conditions.

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    $\begingroup$ 0.42 nm half turn very closely matches what was observed in 172 "survivable" half turn altitude of (disclaimers!) around 300 - 350 feet. Preferred, with safety margin, would be around 500 feet AGL. $\endgroup$
    – Robert DiGiovanni
    Nov 5, 2018 at 17:30
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It is "remotely feasible", you can watch this pilot story from AOPA about someone who did it. But, that doesn't mean that you or anyone else will be successful in attempting it because of the large number of variables that you mentioned. And one successful execution does not mean that it's a good idea in general.

One suggestion I've read several times is to try it yourself in the air: set the 'ground' at say 3000agl then try it out with whatever aircraft configurations you like and see what the results are. But even if you pull it off in those conditions, will you do it again in a real situation with the added stress and possibly additional weight (passengers, luggage) in the aircraft?

All in all, based on everything I've read and been told, it's called the impossible turn for a reason. My training anecdote from an instructor was a local pilot flying with his son who tried it, made the turn but stalled out, crashed on the runway, made it out of the aircraft but then had to watch his son burn to death in the wreckage. That sort of story makes a landing in a field or even a street seem very attractive, which was exactly my instructor's intention.

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There's a very good discussion of the "impossible turn" at the following link:

http://www.nar-associates.com/technical-flying/impossible/possible.html

It goes into an AIAA study using a flight simulator with new and experienced pilots and it shows that while it's technically feasible, pilots need to train for it and be very strict with their bank angle.

There's a lot of detail in the link that's hard to summarize, but the gist is that most untrained pilots fail and crash in a simulator, so unless you've practiced it, it's not worth trying.

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    $\begingroup$ Probably one of the best comments in that link is: "The final element of CAAPP is Planning. Before you pull onto the runway and apply takeoff power you should have planned what you are going to do if the engine quits." Flying isn't about reacting to issues. It's about planning for them before they happen, in case they do. $\endgroup$
    – Shawn
    Jan 9, 2014 at 16:18
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The reason that we are trained to simply not turn back is the same reason we memorize and drill the instant action items in emergency checklists. When the stuff hits the fan, you don't have time to think about all the possibilities of your actions. Your initial response time is critical to a successful outcome. Especially when you're already low and slow. And in an actual emergency situation, your chances of responding correctly are severely diminished if you have to think about what you're doing. You should KNOW what you'll do before it happens.

$V_1$ cuts in a multi-engine aircraft are a great example of making an instant decision that may seem counter-intuitive. If an engine stops before you hit $V_1$ speed, you abort. Otherwise, you know for a fact that once you reach $V_1$ speed, you will continue that takeoff, even if one of your engines fail. You'll deal with the emergency in the air, where it's safer and you have time to run the drill. Turning back to the airport falls into the same category. Turning back may seem attractive, but if you're still in takeoff phase, your chances of success are much smaller if you try a tight bank in a slow, low aircraft.

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Interesting question, especially as I'm learning to fly just now.

My pre-flight abort briefing with the CFI is that if we lose power below 700ft AGL, we're going to land on a suitable field 20° off the nose (after pitching for best-glide speed, 68kts in our plane). However, above 700ft AGL, I'm being taught that we are going to pitch for best-glide and turn to the airport and land at "any available runway". The plane we're flying is C172S and we have never tried this at the airport, but in the air we did 360° turns with idle engine and 68 kts with only about ~300ft lost altitude. I was truly surprised about that.

I'm still uneasy about returning to the field, though.

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  • $\begingroup$ For my local airport, 700 ft AGL is roughly traffic pattern altitude. (Traffic pattern altitude there is actually 715 ft AGL if you nail it exactly.) At one point, my instructor pulled the throttle to idle around the threshold on the downwind leg and basically said "oops, the engine died, now what do you do?". I turned an immediate base and we got down just fine. Climbout is obviously not exactly the same, but 700 ft of altitude in the traffic pattern is plenty of altitude to get down in a controlled manner such that the humans as well as the airplane itself are all in reusable condition. $\endgroup$
    – user
    Jun 15, 2018 at 11:16
  • $\begingroup$ @Marko I'd have to ask what your rpm setting was and what type of turn did you do? Altitude loss for a full 360 is more like 700 feet with no power and landing downwind will give you much higher ground speed. I would specifically go over this with your instructor. Number 1 is to survive the landing. Engine out very low please fly straight ahead into the wind. 300 feet is slightly more than 4 tractor trailers lined up. In a 172 that will give you around 1/2 mile to glide straight, less if you are turning. $\endgroup$
    – Robert DiGiovanni
    Nov 5, 2018 at 10:04
  • $\begingroup$ Something to think about, landing from 1000 feet AGL is only a half turn, usually into the wind. A higher idle rpm setting will give a nice flat "power on" approach to landing, but don't be fooled! This is not "engine out". If idle is high, you could add in some flap to make it more realistic, but practice at a safe altitude. $\endgroup$
    – Robert DiGiovanni
    Nov 5, 2018 at 10:22
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It is not only remotely feasible it is very possible. One of our club members departed a sea-level airport and reached 6,500 feet altituce when the engine quit. He turned back and landed on the runway he departed from. He actually landed long and over-ran the runway.

Now try that at 500 feet above runway altitude and you won't be able to make it.

So where you are when the fan stops is important, as is your skill level. Get with a CFI and practice this!

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  • $\begingroup$ Your CFI should definitely be going over this in training. My guideline was always along the lines of if you are in the takeoff phase (low and still in the pattern) it's easy: don't try to turn back. If you're in the departure phase (climbing out of the pattern) then lower the nose, first and foremost, and make the decision. The important thing is to FLY THE AIRPLANE. $\endgroup$
    – Shawn
    Jan 10, 2014 at 18:10
  • $\begingroup$ That said, I've never had a full power loss on takeoff. I have had a partial power loss on takeoff as I was climbing out. I didn't have enough power to keep climbing without getting very slow, but I wasn't losing altitude when level. I was high enough to clear the trees, so I announced what I was doing over the radio and circled around the pattern at a couple of hundred feet. Made a semi-normal landing and taxied straight to the maintenance hangar. It wasn't much fun. $\endgroup$
    – Shawn
    Jan 10, 2014 at 18:17
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    $\begingroup$ Yes, trying this from 6,500 ft. is quite different than 500 ft. My instructor pulled the engine to idle at about 600 ft and told me to attempt the turn-back just so that I'd have a feel for what happens. In case you're wondering, what happens is that the plane slams into the side of the hill on which the runway sits. Needless to say, once that outcome became apparent, full power was applied and I climbed back up to the pattern. $\endgroup$
    – reirab
    Nov 29, 2014 at 19:04
  • $\begingroup$ As far as engine failure 'in the patten,' though, landing from the downwind without power is quite possible in the Cherokee that I've been flying. One of the first few times I practiced this, I actually didn't descend quickly enough and had to go around to keep from overshooting the runway. $\endgroup$
    – reirab
    Nov 29, 2014 at 19:06
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The answer is yes and no. If at a sufficient altitude, a return to the airport is feasible. If a suitable landing spot is in front of you that is the best option. You MUST know your aircrafts limitations and your skill level to determine when it is safe to return to the airport.

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  • $\begingroup$ Welcome to aviation! I think you meant to say "If at a sufficient altitude..."? Any more specific details you can give about how to determine how much altitude is required would be great, although your overall point about limitations is certainly correct. $\endgroup$
    – Pondlife
    Jan 9, 2014 at 19:53
  • $\begingroup$ @Pondlife - A safe altitude would be individual to the plane you are flying and the conditions you are flying in. There's really no hard and fast rule. That's why the "land ahead" guideline exists. Too often, what happens is that the pilot will panic and try to bank the aircraft around in a situation where it's already nose-high and losing airspeed. That's a very quick way to demonstrate the stall/spin recovery methods that I talked about in the other post. :-| $\endgroup$
    – Shawn
    Jan 9, 2014 at 23:31
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There are two factors which none of the answers above capture:

  1. Don't stall/spin the airplane. This is the #1 risk factor.

  2. Where are you relative to the end of the runway when the engine fails? If you have taken off in the first 500 ft of a 5,000 foot runway, and you lose a lot of altitude in a successful 180-210 degree turn, you will still be able to land on the last 4,500 ft, and maybe even need to slip if there's a strong enough tailwind. If its a short runway with an overrun or airport protection area, you might land short but without any substantial obstacles. If you took off from a sandbar in a river, you will probably find yourself wheels down, but in the drink.

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Apart from the actual physical feasibility discussed in other answers the main risk is a stall situation during the turn.

Winch-launching of gliders is a situation where "power loss" in form of a rope-break is quite common and the reaction to this situation is one of the most importand drills during your training.

Apart from the initial speed and AoA recovery, the decision to turn or not is rather crucial, but when turning you have to take utter care of your speed to avoid stalling. This may be even worse for motor pilots, because you might want to keep banking with a "normal" horizon reference as usual, which can be a bad idea if you are lacking the necessary power to sustain that.

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  • $\begingroup$ Turning back is also trained for with tow-launched gliders. It's been too long for me to recall, but the threshold for a safe turn-back on rope break was quite low (200 AGL?). The keys to success were immediate response, a fairly aggressive bank angle, and keeping airspeed up to keep the AoA in limits. $\endgroup$
    – Wayne Conrad
    Aug 13, 2014 at 15:51
  • $\begingroup$ @WayneConrad not sure if that is part of the curriculum in Germany (it wasn´t for me). Do you mean 200ft or 200m AGL? In any case, airspeed equals life (does not really translate so well). $\endgroup$
    – yankeekilo
    Aug 14, 2014 at 14:31
  • $\begingroup$ 200 ft AGL, but that's just a guess. My glider training was a long time ago. $\endgroup$
    – Wayne Conrad
    Aug 14, 2014 at 14:34
  • $\begingroup$ with zero wind: land ahead below 200ft, 200-500 turn back, 500+ make an abbreviated pattern. add 50ft for each 10kts of headwind. remember, if there is a crosswind, TURN INTO THE WIND. $\endgroup$
    – rbp
    Jan 26, 2015 at 14:30
  • $\begingroup$ I've seen gliders practice "rope breaks" from well below 200', turning back to land on the runway, downwind. $\endgroup$
    – quiet flyer
    Nov 5, 2018 at 6:06
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I have an older friend who flew single-engined de Havilland Vampire jets in the Air Force in the 1950's. He told me once that they used to practise engine failures after take off by pulling vertically into an Immelmann, then landing on the runway they'd just taken off from in the opposite direction.

Thinking about it now, they'd be landing downwind which would add to the fun and games.

Anyway assuming it's true (and I have no reason to doubt him), it's pretty damn cool!

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