Anti-Spin Ideas

[BBerson]

I think high powered electric fan tip thrusters could eliminate autorotation (spin).
It's hard to do it with passive controls because the inside wing is essentially stopped. Active thrust is needed.

 

[Victor Bravo]

Although this is definitely not a discussion centered on flying wings, the flying wing research done by Al Bowers and the resulting twist distribution is relevant here.

Bowers' research led him to greatly increased twist (washout) as a method of creating proverse yaw. Twisting the wingtips to be angled downward into the up-wash developing near the tips also would reduce the local drag in that area, improving performance to some small degree. Additional side benefits of this are that the outer wing areas are operating at a much lower AoA than the root in slow flight, which would further resist tip stalls an/or spins.

I asked Al one day whether this new twist distribution would be useful or valuable on a classic Cub style wing, and he said "Yeah, that ought to work well too...".

 

[Autodidact]

Although this is definitely not a discussion centered on flying wings, the flying wing research done by Al Bowers and the resulting twist distribution is relevant here.

Bowers' research led him to greatly increased twist (washout) as a method of creating proverse yaw. Twisting the wingtips to be angled downward into the up-wash developing near the tips also would reduce the local drag in that area, improving performance to some small degree. Additional side benefits of this are that the outer wing areas are operating at a much lower AoA than the root in slow flight, which would further resist tip stalls an/or spins.

I asked Al one day whether this new twist distribution would be useful or valuable on a classic Cub style wing, and he said "Yeah, that ought to work well too...".

So how about variable washout wings? One way to do it would be to have the outer wing panels rotate around the lateral axis and the way I'm seeing it they could be interconnected with the elevators so that with up or down elevator you would get the appropriate lift distribution (BSLD) regardless of in upright or inverted flight. It seems a little backward to have the greatest lift potential (whole wing stalls at once) when in the cruise condition, though.

 

[Aerowerx]

Although this is definitely not a discussion centered on flying wings, the flying wing research done by Al Bowers and the resulting twist distribution is relevant here.

Bowers' research led him to greatly increased twist (washout) as a method of creating proverse yaw. Twisting the wingtips to be angled downward into the up-wash developing near the tips also would reduce the local drag in that area, improving performance to some small degree. Additional side benefits of this are that the outer wing areas are operating at a much lower AoA than the root in slow flight, which would further resist tip stalls an/or spins.

I asked Al one day whether this new twist distribution would be useful or valuable on a classic Cub style wing, and he said "Yeah, that ought to work well too...".

Nickel's mentions in his "Tailless Aircraft" book that one of the Horten wings would not spin. One of their top test pilots (forgot her name---would have to look it up) tried everything she could to get it to spin, but it would not. This was not only because of the proverse yaw, but from the forward CG.

 

[BBerson]

So how about variable washout wings? One way to do it would be to have the outer wing panels rotate around the lateral axis and the way I'm seeing it they could be interconnected with the elevators so that with up or down elevator you would get the appropriate lift distribution (BSLD) regardless of in upright or inverted flight. It seems a little backward to have the greatest lift potential (whole wing stalls at once) when in the cruise condition, though.

I was thinking of linking the ailerons to the elevator to provide variable washout. Both ailerons would move up with full aft stick. The aileron up movement could act only on the last bit of aft stick. Seems fairly simple. Must have been tried in past?

 

[Autodidact]

I was thinking of linking the ailerons to the elevator to provide variable washout. Both ailerons would move up with full aft stick. The aileron up movement could act only on the last bit of aft stick. Seems fairly simple. Must have been tried in past?

You would think, but I've never heard of it. Perhaps instead of entire outboard wing section rotating, you could have an aileron attached to the [thick] trailing edge of a flap; the flap would reflex with up elevator while the ailerons continue to act differentially. It seems like there was mention of something similar in Normans Brief History of the Junkers Flap paper, but I can't be sure that it was the exact same thing...

Edit: I think actual wing washout would be better; don't reflexed flaps decrease the Clmax of an airfoil?

 

[BBerson]

Sounds like a double hinged aileron.

 

[N8053H]

The best anti-spin system that can be installed for an airplane, is the person flying the airplane..

 

[radfordc]

Warning: only one of the following meets the strict requirements of the OP's question:

Some wacky ideas:

-A lightweight spin chute carried at all times. If reusable, it could also be handy as a source of drag to avoid shock cooling on descent or to steepen an approach. Obviously it would be something else added to the annual inspection.

----------
)

Not wacky at all. It's called a BRS ballistic chute. http://www.brsaerospace.com/BRS_History.html

 

[Tiger Tim]

I was thinking of linking the ailerons to the elevator to provide variable washout. Both ailerons would move up with full aft stick.

That would make landings fun; pull back to flare and dump a bunch of lift while you're at it.

 

[BBerson]

That would make landings fun; pull back to flare and dump a bunch of lift while you're at it.

Yeah, it might work well. No float. Just flare at 1 foot and stick it down with full aft stick.
It would only move the ailerons up on the last bit of aft stick. That last inch or so that kills pilots.

 

[TFF]

Spin chutes have been used plenty; mostly jet fighters during testing. They do have to be ejectable. Bombardier crashed one of their planes during a certification test flight when the plane entered a stall/spin and they deployed the chute, but it was accidentally cut away after deployed.

 

[henryk]

Nickel's mentions in his "Tailless Aircraft" book that one of the Horten wings would not spin. One of their top test pilots (forgot her name---would have to look it up) tried everything she could to get it to spin, but it would not. This was not only because of the proverse yaw, but from the forward CG.

BKB1-A was spin und tuck resist!

 

[rdj]

Just out of curiosity, have there been any studies of spin behaviour in aircraft that use spoilers for roll control instead of ailerons? I wonder if they're easier or harder to spin and/or to recover?

Also, most spin recovery techniques are about breaking the roll/yaw coupling by using rudder to break the yaw coupling (after neutralizing the ailerons). Could spoilers be used instead to break the roll coupling (basically by dumping lift on the unstalled wing)?

Lastly, there are regular spins, and then there are flat spins (usually entered after a misapplication of power). Are any of the anti-spin technologies mentioned in this thread, and actually present on aircraft (like the wing fences), effective once a spin has gone flat? If not (and that's what I suspect) are there any technologies short of a 'chute that could help extricate an aircraft from a flat spin? BBerson's electric fan wingtip thrusters are one possibility I suppose.

 

[Himat]

BKB1-A was spin und tuck resist!

From inverted flight too?
To make an airplane resist entering spin from "normal" uppright flight is doable. What is difficult is to make an airplane resisist entering a spin from all attitudes, typical from "unusual" attitudes.

 

[Sockmonkey]

Would a rudder that can function as an airbrake assist in spin prevention/recovery?

 

[Tiger Tim]

Just out of curiosity, have there been any studies of spin behaviour in aircraft that use spoilers for roll control instead of ailerons? I wonder if they're easier or harder to spin and/or to recover?

I'm not aware of any studies but I have a bunch of time on roll spoiler equipped planes. Spoilers won't drop a wing at the stall the way ailerons will, in fact you can steer the airplane around in a stalled descent like a much more stable falling leaf. If you stall and clomp down on a rudder pedal, I have it on good authority that it will drop into a spin. The fellow who did it said it spun and recovered just like a Cessna 150.

 

[BBerson]

The Helio interceptor blades are effectively spoilers, combined with short ailerons and slats. Sort of complex.
But I think the Helio is or almost is stall proof.
NASA uses rocket thrusters for getting out of locked spins.
So electric tip thrusters could be linked to the ailerons and come on with aileron use automatically to prevent the yaw before the spin starts. They could also provide thrust for takeoff.

 

[BBerson]

The outboard cuff (with abrupt end) is the best that NASA came up with, I think.

View attachment 62616

 

[REVAN]

Nickel's mentions in his "Tailless Aircraft" book that one of the Horten wings would not spin. One of their top test pilots (forgot her name---would have to look it up) tried everything she could to get it to spin, but it would not. This was not only because of the proverse yaw, but from the forward CG.

The Bell-Shaped Lift Distribution (BSLD) has a lot of benefits. It's not just better from a stall-spin perspective, it's better for performance and efficiency as well. A plane doesn't have to be a flying wing to benefit from a BSLD.

Prandtl wrote his famous paper on lifting line theory and identified the elliptical lift distribution as having the least amount of induced drag for a given span. That paper revolutionized aeronautical engineering. The problem is that this conclusion wasn't correct when applied to aircraft, and several years later Prandtl wrote another paper that identified what was wrong with the elliptical lift distribution. In this second paper, he identified, what was later to become known as the BSLD, as the optimized lift distribution for an aircraft to produce the least drag and have the best performance.

The problem was that by the time this second paper was written, WW-II had begun and the concept of the BSLD didn't really get out of Germany and disseminated to the rest of the world. The Horten brothers in Germany were the only ones that really paid attention to Prandtl's second paper and applied the BSLD to their flying wing designs with great success. However, Germany lost the war, and the Horten designs were scrapped. During the war, massive aviation industries were built on technology that predated the concept of the BSLD, and once that non-optimal technology was entrenched, it was there to stay for a very long while. To this day, a surprising number of people in aviation still believe that the elliptical lift distribution is the optimized lift distribution to strive for. They don't realize that the elliptical distribution is only optimal to use on something that doesn't fly.

So, a BSLD will make planes fly more efficiently and at the same time improve the yaw stability of the wing. It is a win-win from an aerodynamic perspective.

I sometimes wonder what airplanes would look like today, if Prandtl had gotten his second paper out a few years before WW-II had begun?