Snaps/Spins

[EHaury at aol.com]

Ron

Very good points. The rotational rate changes during snap initiation and 
stopping should not be downgraded. My point is that major track changes during 
initiation should be downgraded, as well as returning to an unstalled condition 
and rolling to finish. The latter is not a zero, but a severe downgrade!

You're the AE, take a look at my view of the snap. First the wing must be 
quickly (to maintain track) loaded to stall or very near stall. The mechanism is 
pitch input in the positive or negative direction. The pitch angle needed will 
vary with the stall characteristics of the wing, the existing load (level, 
45, vertical) and speed. Fast pitch change is definitely better! 

Just as the wing reaches stall a yaw input In the desired direction of 
rotation retracts one wing and advances the other. The retracting wing now has less 
relative airspeed and stalls (or stalls more deeply) than the advancing 
(higher airspeed) wing and rotation occurs as though a wing fell off. Again fast 
rudder input is good.

The accelerations and decels of the rotation of snaps done this way will be 
very dependent upon the roll axis inertial characteristics of the aircraft. The 
lighter the wings the better, with heavy wings making the snap unmanageable.

Enter ailerons. The ailerons contribute in a couple of ways. The upward 
traveling aileron on the retracting wing, that we wish to stall more deeply, helps 
the stall while the downward traveling aileron on the other lowers stall speed 
of this wing somewhat like a flap. Therefore less pitch and yaw to stall / 
rotate. The big benefit is that the aileron application helps overcome the roll 
inertia involved at the start and stop, making both more controllable. (Yes, 
the full scale folks use ailerons in snaps to help manage inertia also.) 

Back to the elevator. The amount of pitch needed to initiate a snap is more 
than required to maintain it (likewise yaw). If maintained at high angles 
throughout the snap the aircraft will retain some pitch and yaw upon snap exit. 
(General term is "buried snap.") If the pitch and yaw inputs are reduced after 
snap initiation to levels just sufficient to maintain the snap, the snap will be 
tighter and exits cleaner. Unfortunately, some who have the skills to achieve 
this level of control are mistakenly accused of performing an axial roll. 

Another spin control that can be used to advantage is the throttle, remember 
that the faster the wing is moving the more pitch angle is needed to effect 
stall and the more likely the track will change before stall occurs. While idle 
will get the quickest stall, the drag created during the snap will render the 
airplane a dead duck on exit. Some middle ground exists for each airplane 
design, be it faster entry or powering up during the snap to offset drag.

I agree that the snap is probably more difficult to judge than execute. 
However, it seems that it's here to stay (and it's a fun maneuver). I started this 
discussion to stimulate thought and encourage folks to think about appropriate 
judging of the maneuver. "Sticks in the corner" doesn't necessarily result in 
a good snap and the very skilled folks, who have developed techniques to make 
the snap a joy to watch, haven't all figured out a way get something that 
isn't a snap judged as such.

Earl
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