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The scenario here is a detachment of the tail,one with the whole empennage.

Could a variant of an existing model of swept winged jet airliner be made to remain controllable, using ailerons, differential flaps, differential spoilers and differential thrust, used for pitch, roll and yaw, regulated by an appropriate autopilot program, and with no other modifications?

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Theoretically, if the Neutral Point was still aft of the C of G with the tail gone, you could still be statically stable to some degree, but without the trimming surfaces of the elevator/stab providing the pitching force-balance system to control AOA, you become statically stable about the wing's zero-pitching-moment AOA somewhere, and you are more or less a lawn dart or a bomb and will arc down until in a statically stable vertical plunge.

You are unlikely to be able to make the wing, as it is, provide the required trimming power that was being provided by the tail. You might get some pitching authority by making the existing ailerons work together as elevons, but amount of pitching/trimming power would be so limited, it would only give you some control over your impact point, like a laser guided bomb, or at best, make it possible to maintain level flight at very high speed.

For that kind of concept to work, you would need to effectively reconfigure the aircraft as a flying wing, with all of its limitations, by incorporating all of the required pitch control and trimming authority for the full flight envelope into the wing itself, which means you have to design a new one, with a different airfoil and appropriately sized elevons at the wing tips, a limited C of G range, and all that sort of thing.

Then, on to your flying wing you stick a fuselage extension with a tail surface, for which you must also add fuselage forward to balance out, and you have a kind of weird hybrid tail-less-airplane-with-a-tail, like the evil genius farmer who bred a cow-chicken hybrid to provide a unified solution to eggs and milk production.

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  • $\begingroup$ I just remembered Turkish Airlines flight 981. They were in an elevator plunge, but very nearly levelled off by increasing the powerl $\endgroup$
    – Abdullah
    May 8 at 13:13
  • $\begingroup$ But this had still the stabilizer itself, only lost the controll surfaces (or better: controll of the controll surfaces) $\endgroup$
    – tsg
    May 8 at 14:54
  • $\begingroup$ Yeah they were stuck with whatever trimming power was being provided by the stab setting and a limited amount of pitch change authority by varying wing engine thrust, where more thrust gives nose up trim. $\endgroup$
    – John K
    May 8 at 15:15
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No - though the vertical stabilizer might be worked around, the same is not true for the horizonal stablizer. Without it you will loose stability in the pitch axis so much that I doubt there will be any chance for a controlled flight on nearly all aircaft (though there is a possibility that a few ones might remain some kind of controllability)

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    $\begingroup$ Yeah, there's little pitch leverage. But I was wondering if sweep brought in enough to steer the airplane to a crash landing $\endgroup$
    – Abdullah
    May 8 at 13:08
  • $\begingroup$ Down-voted for being incorrect! $\endgroup$ Jun 1 at 13:09
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Without the Vertical Stabilizer? Probably - but it would be very difficult. Without the horizontal, on the other hand, is a no. The horizontal stabilizer works by creating lift in the opposite direction of the wings. Moving the elevators increases and decreases the amount of "upside-down" lift, which moves the Center or trimming moves the Center of Lift back and forth along the aircraft. Think of the airplane as a seesaw, the Center of Gravity is the fulcrum, and the Center of Lift is the force applied to tilt it. Assuming the nose of the plane is pointing to the left. If the Center of Lift is to the right of the centre of gravity, the aircraft will pitch down (if you pulled the right side of the seesaw up, the left side will go down.) Conversely, if the CoL is to the left of the CoG, it will pitch up. Without this stabilizer, you would have no way to move the CoL. Yeah, you can adjust the amount of lift from the wings, but you can't pitch.

Here's a great video on how the horizontal stabilizer works:

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  • $\begingroup$ Look at the old-fashioned "free-flight" model airplanes from before the days of radio-controlled models-- they nearly all have lifting tails, with obvious right-side-up airfoils on the tail surfaces. So clearly stability is possible with such an arrangement. Take the idea to an extreme and you have a "tandem wing" configuration with similar-sized surfaces in front and back, then take it even further and you have a canard configuration. $\endgroup$ Jun 1 at 7:16
  • $\begingroup$ @quietflyer It's possible if the aircraft is made for it. I can't think of a modern airliner that uses this design, and the original question was about airliners losing their tails. $\endgroup$
    – tizmataz77
    Jun 1 at 13:01
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Even if you can still control the plane without the vertical stabilizer, is not the same for the horizontal one, as said by tsg. This because the wing is instable and has the tendency to dive the plane. The function of the horizontal stabilizer is to contrast this tendency. And no matter if the plane is statically balanced because this torque is due to the asymmetry of the foil wing.

The only chance is the that liners have arrow wing configuration. In this way the more external edges of the wing are in a back position in respect to the GC, and they can have still a stabilizing effect. This is why flying wing aircraft as B2 Spirit can fly. Maybe that this effect can be enough for some aircraft but not for someone else. In any case, also if the aircraft remains stable (without doing a crazy looping), it still remains the problem controlling the height without the elevator using only the engines.

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  • $\begingroup$ You are (probably) correct that no actual/current airliner could realistically survive, but it IS possible to design one that could. $\endgroup$ Jun 1 at 13:12
  • $\begingroup$ @MikeBrockington. It could also depend on the extent of damage eg the more tail is lost the more CG moves until aircraft becomes stable $\endgroup$
    – Abdullah
    Jun 2 at 6:08
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Well, it depends on what you mean by "a variant of an existing model" and "controllable".

Technically, provided the center of mass does not shift out of range when the heavy tail falls off, a tailless swept wing can in principle be trimmed to fly straight and level. It can also be given effective controls surface.

But could "a variant of an existing model" necessarily be given suitable mass distribution or control surfaces?

Does the need to reprogram the flight software count as "controllable"?

Choose your answer accordingly.

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