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I've been doing some research for a uni assignment and I noticed that the RQ-11B uses a "deep stall landing" to get back onto the ground. What I don't understand though is how this aircraft gets into a deep stall, so far every definition of a deep stall that I've seen says that for an aircraft to be in a deep stall, the horizontal stabilisers are in the wake of turbulent air from the stalled main wings. The aircraft in question has high mounted wings and a conventional tailplane, so even in straight and level flight the horizontal stabilisers are below the dirty air from the wings and so when the angle of attack is increased, the tailplane only gets further away from this airflow.

So the main question is, is there another definition of a deep stall that doesn't need the horizontal stabilisers to be in the dirty air from the stalled wing.

This is the aircraft or rather SUAV in question

Quinnchento
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  • https://www.aerosociety.com/media/3532/4109.pdf maybe helpful – user3528438 Aug 12 '18 at 10:11
  • Your case might better be called a "fully developed stall". A deep stall is characterized by a fully stalled wing, a trim point at high angle of attack plus sufficient loss of elevator control so the aircraft cannot escape by elevator commands. A fully developed stall can always be ended by pushing the nose down. – Peter Kämpf Aug 12 '18 at 17:56

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I believe you are correct and the terminology they used was incorrect. What possibly is being described is sometimes called "mushing". Some aircraft are capable of having the airspeed bleed off until the elevator is all the way up - it then mushes with a high descent rate to the ground.

I owned a Navion that would do this. If you slowly bleed the airspeed off and add full elevator it will end up with a 500-600fpm wallowing descent and severe buffeting (full aileron may be needed as the wings rock side to side).

Several Piper aircraft are also similar such as the PA-28-140 Cherokee. The Cherokee is known to run out of stabulator during flares and can pancake onto the runway - no damage but an embarrassing hard thump.

I have flown just about all the single engine and small twin engine Cessna's and none of them will do this. They have lots of elevator and are always capable of a nose dropping full stall.

Captain "Sully" Chesley Sullenberger reported he was aware the flight computer of the Airbus A320-214 did this (US Airways Flight 1549, "Miracle on the Hudson") and deliberately held the yoke all the way back and let the aircraft mush onto the Hudson River.

jwzumwalt
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  • That makes a lot more sense, later on in the passage they described the landing a bit more. they described a 1:1 glide ratio at low speed which didn't make sense but another description of mushing I just read was ''a nose-up glide'' which sounds much more accurate. Thanks – Quinnchento Aug 12 '18 at 14:14
  • Of course, the plane didn't do what Sully had commanded. Despite his full back stick it stopped at 9.5° pitch angle due to anti-phugoid mode programming in the control laws. – TomMcW Aug 13 '18 at 05:06
  • Memories of the Piper Arrow. One could do a pseudo short field technique, slowing gradually over the fence, and at the right moment, YANK the yoke full aft and it would kiss the runway just as pretty as you please. – Walker Aug 13 '18 at 18:19
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Worth watching a video of the landing. The tail of the RQ-11 is an all moving horizontal stab, and on landing it pitches full aft, the wing clearly stalls, and it plops down at a glide slope closer to an autorotation. Reminiscent of the Spaceship One and Two. It then crashes on impact and the wing falls off, by design.

MikeY
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