This answer, and the Wikipedia article on push-pull configuration both claim that aircraft with push-pull configuration are easier to fly in the event of engine failure, because the thrust provided by remaining engine would remain in the centerline.

However, lot of aircraft with push-pull configuration seem to be relatively small ones, so I am wondering how gyroscopic effects would affect the handling of the aircraft in the event of engine failure.

I found this answer comparing WWI era FB19's to F16's. But as I said before, lot of push-pull reconfigured aircraft probably have less mass and much slower than F16, so the calculations in that answer may not apply.

So my question is, is there any noticeable handling difficulties in push-pull configured aircraft, when an engine fails?

  • $\begingroup$ I'm confused @Krumia, are you asking about purely gyroscopic effects, or other effects? If it's other effects you need to make that clear. $\endgroup$ – GdD Jul 30 '18 at 8:56
  • $\begingroup$ @GdD: I'm asking specifically about gyroscopic effects. $\endgroup$ – sampathsris Jul 30 '18 at 9:46

Gyro precession effects from a propeller are minimal when at flying speed and making modest pitch and yaw motions, where the precession is mild and there is lots of aerodynamic damping. You don't really notice it. Propeller slipstream over the rudder has a much bigger effect, which a lot of people may confuse with precession.

You have to make large sudden pitch or yaw motions at low speed, like when taking off a taildragger with a very large propeller. If you raise the tail suddenly at low speed, precession of the propeller will make the airplane swing noticeably. Or, with aerobatic airplanes that make extreme pitch and yaw motions and where precession will have an effect that has to be taken into account (as well as putting massive stresses on the crank at the prop flange).

For wing mounted engine twins, the effects of offset thrust are the main limitation, with a minimum control speed that is usually well above the stall and below which the airplane will roll over. Centerline thrust aircraft avoid this problem for obvious reasons. In any case, I don't believe gyro precession is a factor at all in a Cessna 337, on either engine, or on a regular twin for that matter because the pitch and yaw rates you generate aren't enough to create significant precession effects that could affect controlability.

In the end though, with piston twins, gyro precession is the least of your problems. The biggest one is the fact that the loss of 50% of thrust leaves you with almost no performance reserve. Wing mounted engines leave you with a somewhat more dangerous situation due to the ability to lose complete control well above the stall by dropping below minimum control speed, but even with center line thrust, the single engine performance is so marginal that if you are at gross weight and above sea level and it's hot, you are going down anyway. Yes there is no Vmc limit, but you are still faced with having to maintain minimum speed for performance and chances are you are still going to crash land eventually and you may ending up stalling and spinning it the regular way if you panic trying to will the plane to fly, just like a regular twin.

For this reason I don't believe center line thrust aircraft have all that much better a safety record following engine failures than regular twins.

  • $\begingroup$ Aren't all multiengine aircraft required to have powerful enough engines to provide them with a large performance reserve even in single-engine flight? $\endgroup$ – Sean Sep 20 '18 at 3:06
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    $\begingroup$ The large performance reserves of jets are largely a function of the huge amount of power required to go fast so that 50 percent of thrust is plenty for a decent climb. Turboprops are kind of in between and have passable climb on 50 percent thrust. Piston aircraft don't have as large a speed range and 50 percent gives maybe only a 5-10 percent margin over the minimum required for level flight. A DC-3's single engine rate of climb is 300 fpm at gross - at 59F at sea level. A piston twin that can do 500 fpm single engine at gross is a pretty high powered machine. $\endgroup$ – John K Sep 20 '18 at 12:13

One could look at the NTSB records of the Cessna 337, a front & rear engine push-pull 6-seat aircraft, vs that of another comparable sized twins with engine mounted wings, such as a Piper PA-30, and try and draw some conclusions.

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    $\begingroup$ That would be a useful exercise. My own belief is from some long ago articles in Flying Magazine where they used to discuss multi engine safety a lot, with the most interesting thing being that from pure statistics, a single is actually safer than a low powered twin from a "chance of dying" perspective. Anyway, they had written about the 337 and how it didn't seem to have an accident rate much better than any other twin. Similar to the Ercoupe, the stall proof "safety plane" that ended up with no better an accident record that most other light planes. $\endgroup$ – John K Jul 30 '18 at 21:39

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