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During a tailslide (a flight regime where the relative airflow over the aircraft is from the tail towards the nose; i.e., an attack angle between 90º and 270º; i.e., the airplane is moving tail-first), the airflow over the aircraft’s control surfaces is in the opposite of the usual direction, causing deflections of the aircraft’s flight control surfaces to produce motions opposite those that would be produced in forward flight (for instance, in a tailslide, applying up elevator will cause the nose to pitch down, and left rudder will yaw the nose right).

Given that:

  • modern fighter aircraft use computerised fly-by-wire control systems instead of the mechanical linkages used in pre-21st-century fighters;
  • fighters are optimised for extreme maneuverability to the extent that a tailslide would be very easy to enter;
  • intentional tailslides could easily occur during combat maneuvering, or - even more likely - during an airshow;
  • and the control reversal inherent in a tailslide, like all types of flight control reversal, could easily kill an unwary pilot;

do modern fighters, during a tailslide, automatically reverse the commanded direction of flight control surface deflections relative to the direction that would be used in normal flight (for instance, applying down elevator rather than up if the pilot pulls back on the yoke in a tailslide)?

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While the reversal of flight controls does happen, it is transient in nature, and in virtually all cases if you let the aircraft "fly" itself it will pitch down and recover.

Only aircraft with thrust to weight ratio of at least 1 to 1, and thrust vectoring of some sort if a jet, will be able to maintain the nose high attitude.

Prop aircraft are a different story as they essentially "hang" from the prop if the engine can develop enough power to do that.

Recovering from a tail slide is not like recovering from a stall or spin, you can't really use flight controls for anything until the aircraft develops enough airspeed for them to be effective, and in 100% of the times I have been in one, by that time the relative wind is normal and not reversed.

The exception is in prop aircraft where the prop wash against the rudder and elevator does provide some control effectiveness, but not reversed.

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    $\begingroup$ Good answer. I will add that the pilot will never "fly" the airplane backwards in the conventional sense of the term. Such a situation is considered a departure from controlled flight, and aircraft specific training will direct the pilot to hold controls in some (likely neutral) position until oscillations stop, and hopefully the aircraft ends up nose low with increasing forward airspeed from which a normal recovery can be made. $\endgroup$ – Michael Hall Feb 15 at 19:26
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    $\begingroup$ There is no difference between prop and jet aircraft (or aircraft with pusher props, for that matter) in this regard—since the thrust axis is constant relative to the aircraft, the position of the engine along the axis has no effect on stability. You may also note that helicopters are actually unstable in both pitch and roll. $\endgroup$ – Jan Hudec Feb 15 at 21:42
  • $\begingroup$ This answer seems to be focused on an unintentional tailslide - I was more thinking of something to aid with control during an intentional tailslide (such as during an airshow or a dogfight). $\endgroup$ – Sean Feb 16 at 3:56
  • $\begingroup$ @sean Only thrust vectoring will do what you are thinking of, but I may be wrong. $\endgroup$ – Juan Jimenez Feb 16 at 12:19
  • $\begingroup$ @JanHudec you bring up a very interesting point in that I was assuming the desired answer was only in the context of fixed wing aircraft. On helos a tailslide would be a totally different animal, no? :) $\endgroup$ – Juan Jimenez Feb 16 at 12:20
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No.

Two main reasons.

First, no fighter aircraft is optimised (or even designed for) tailslides. They even lack basic sensors to measure air data (airspeed, angle of attack) in such conditions. Those that can do tailslide, do it as a stunt rather than as a useful manoeuvre. It's been speculated about a lot, esp. since Su-27 and MiG-29 became known, but all potential use cases put forward were highly theoretical. Even today, a dogfight is largely about energy management, and by performing a tailslide you expend most of your energy...

Second, if you think about it, you don't want to reverse controls. When you pull the stick/yoke, what you really want is not 'nose up' but rather 'go up' (if we start off the level flight), or more accurately, to create a positive load. In a tailslide, this means 'tail up'! Which will be served with the same elevator sense (provided there is enough 'negative' airflow, and, of course, much less efficiently). The same for rudder. The only control you may want to reverse is ailerons.

If you develop enough negative airspeed, your statically stable aircraft (in pitch) will probably become unstable and may require a different kind of control, but that's another story. Practical designs are even farther from this condition.

That said, modern FBWs may reverse controls, and they do it in less exotic situations. Perhaps the most practical example is ailerons reversal in near- and post-stall regime. In such conditions, FBW may start issuing 'opposite' commands to the ailerons, or even do something more sophisticated like driving a single aileron or coupling the roll command with rudder, all in order to provide 'conventional' controllability even after stall. If the flight control system treats tailslide as stall, you may have the reversal you asked for; but I don't know real FBW designs to such level of detail to affirm that.

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