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Spin Susceptible Aircraft for Testing

#1
I am a student at Virginia Tech pursuing my masters in Aerospace Engineering with a focus in dynamics and control and I am in need of a cheap platform which can be easily put into a spin. It should also be able to carry the Pixhawk PX4 autopilot platform and maybe some other small piece of gear to record measurements for analysis. Any suggestions?

I am going to use this platform to develop, implement, and test a control system which will allow for maneuvering in a spin. Such as intentionally terminating a UAS flight where an intentional spin is common; however, we may still want to direct the aircraft away from houses, etc. so control may be desired.
 

FAI-F1D

Free Flight Indoorist
#2
Ah, another control freak. ;) Welcome to the voodoo world.

Spin capability is mainly a function of having the CG far enough aft to put the aircraft into a deep stall and having a planform that starts blanking out some of your rudder area. I would suspect that some of the foam 3-D aerobatic models would have this capability. You also might be able to get the same capability from some of the lighter trainers out there by moving the CG aft. Be warned, however, that you're going to develop an extremely high sink rate in a stall and at a significant nose-down attitude, so impact damage is a serious threat. This impact damage is the reason why most vertical retrieval UAV's use a stabilized deep stall actuated by a stabilator (full flying stab) with an inflatable cushion on the belly of the aircraft. Look up "pop-up stab dethermalizer" to get an idea of what I'm talking about as well as the origins of this proven system. Do note that the deep stall actuation requires careful attention on high aspect ratio wings, as it can result in a very nasty (but recoverable) spin on those planforms. That flight regime has been known to severely damage the wings and forward fuselage on impact. It is possible to maintain some degree of forward movement in a deep stall, and the aircraft can be maneuvered, though this is seldom attempted since it is primarily a means of vertical retrieval for UAV's and uncontrolled free-flight model airplanes.
 
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AkimboGlueGuns

Biplane Guy
Mentor
#3
Someone was talking about a tail heavy versa wing tip stalling, I suspect a much more tail heavy wing would spin quite easily. If it will not mess with your experiments, you could try duckerons. Best of luck!
 

joshuabardwell

Senior Member
Mentor
#5
Someone was talking about a tail heavy versa wing tip stalling, I suspect a much more tail heavy wing would spin quite easily.
Flying wings generally won't spin, because they don't have enough mass aft of the CG. As a wing's CG moves aft, it becomes increasingly unstable in pitch, to the point where it becomes unflyable.
 

SOOFLY

Senior Member
#6
Here is clip of a wing stalling and being stuck in a flat spin. This is what my versa wing does every time if I purposely stall the wing, however it's not near this bad. I've been able to recover each time, but it is sketchy. This is the Skywalker X-8 from Hobbyking if your wanting a test vehicle.

 
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Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#8
Flying wings generally won't spin, because they don't have enough mass aft of the CG. As a wing's CG moves aft, it becomes increasingly unstable in pitch, to the point where it becomes unflyable.
heh, heh, heh . . . I've done it before . . . but yeah, she was a pitchy little . . . um, plane. The maiden was interesting, and iconic of the phrase "A nose heavy plane flies poorly, A tail heavy plane . . ."


I agree, a wing would be a bad case for this one. Ideally, for a test platform you want it to be otherwise well behaved, but easy to induce a spin, and to get a wing to spin easily you either have to power/drag it into a spin with diferential thrust or duckerons (is that really in a stall spin?!?) or trim it to perform poorly across the board.
 

AkimboGlueGuns

Biplane Guy
Mentor
#9
I think the duckerons are your best bet at getting the plane to spin, unless you are initiating a stall spin. You could also try building a FT spitfire without the undercambered tips. RC Spitfires tend to have a terrible tip stall/spin because of the eliptical wing. The undercamber prevents this, so if you remove this feature it should fly similarly to the scale spits.
 

earthsciteach

Moderator
Moderator
#10
hokie-the idea of "control" in a spin is quite interesting. Wouldn't the best scenario for control be to recover the aircraft from the spin?

If you are looking for an airplane that has a nasty stall tendency, go with something with a high wing loading, no washout and low wing configuration. The elliptical wing of the Spitfire, combined with large elevator authority, just loves to stall, particularly in high g maneuvers.
 
#11
'Spin' implies nose low, high sink rate.

Are you looking for something that will flat spin?

When I think flat spins, I think rad-jet, fun-jet, and Stryker.