[NSRCA-discussion] Snap entry in FAI

[Bob Richards]

A spin entry and a snap are two different beasts. 
 
For a spin entry, you must gradually slow the airplane down to the stall speed while maintaining straight flight. As the plane slows, you must gradually increase the angle of attack to keep the lift constant, up until the point of the stall.
 
For a snap, you don't have time to slow the airplane down, you must initiate the snap at well above the stall speed. Any increase in angle of attack from that which is necessary for level flight will result in a corresponding increase in lift and will cause a deviation from a straight path.
 
Any manuever description that states the plane must stay on a straight path during the autorotation is flawed, IMHO. The lift of the wing does not drop to zero when it stalls. In fact, at the moment of the stall, the wing is producing near maximum lift. And, keep in mind that if done properly, the snap roll only has one wing panel stalled.
 
I had someone shoot video of my flying, and in the video was a snap roll flown straight toward the camera. I thought it was a pretty good snap roll when I flew it. In looking at the slow motion video, it was obvious the airplane was stalled and a snap roll was performed, but it was also very obvious that the path of the plane was corkscrewed. The entry and exit were on the same heading and altitude, but parallel, and displaced by at least one wingspan. This would not have been so obvious had the plane not been flown directly towards the camera.
 
JM2CW.

Bob R

--- On Mon, 6/16/08, Matthew Frederick <mjfrederick at cox.net> wrote:

It is entirely possible (and expected) that you can show a pitch change 
without a deviation in the line of flight. It requires a reduction in 
throttle combined with the application of elevator. If it wasn't possible
to 
show a pitch change without changing the line of flight we would see some 
horrible spin entries. Keep in mind, the snap and spin are essentially the 
same maneuvers with different entry speeds. Doing a proper snap according to 
the rules (both AMA and FAI from what I can see) is a matter of split-second 
timing of the control inputs. Nothing more.

Matt

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