Snaps/Spins

[Rcmaster199 at aol.com]

Indeed, Ron!! Earl's explanation helped me solidify some things also. This is 
a very good thread and we need more like it. The spin would be another such 
topic, and particularly what constitutes a snap entry. 

I think what Earl is saying is that elevator should be entered as fast as the 
plane is capable of. The abruptness of the elevator command induces a rapid 
wing stall. Very shortly thereafter, perhaps on the order of a tenth of a 
second later, yaw command is entered in the desired direction. And lastly aileron 
is entered
, even quicker after yaw, to roll the plane. To exit, elevator is reduced 
first, then roll and last yaw. Earl did I read you right?

The present Masters has the 1 1/2  on the 45 diagonal, and it was a first for 
me two years ago. It did take some time to learn to sequence the sticks and 
boy were they ever ugly at first. Now it is easy and fun to do as Earl states. 
And the exit is..... well.... a snap, if you pardon the pun.The neat thing 
about neutralizing yaw last, is that for the 1 1/2 snap maneuver, I hold rudder a 
little longer to get heading back, if needed. 

Plane design plays the major role in timing of the control surface inputs and 
their relative proportions. 

One more observation: rolling out the last half roll where it should be a 
snap, earns a zero based on the 15 deg/1 pt rule.

Matt Kebabjian


> Subj:Re: Snaps/Spins 
> Date:6/24/2003 8:25:29 PM Eastern Daylight Time
> From:<A HREF="mailto:vanputte at nuc.net">vanputte at nuc.net</A>
> Reply-to:<A HREF="mailto:discussion at nsrca.org">discussion at nsrca.org</A>
> To:<A HREF="mailto:discussion at nsrca.org">discussion at nsrca.org</A>
> Sent from the Internet 
> 
> 
> 
> For a non- aeronautical engineer, Earl has a great explanation about what 
> happens during a snap roll.  I tried to find fault and couldn't.  Nice job 
> Earl.
> 
> Ron Van Putte
> aeronautical engineer
> 
> 
> <A HREF="mailto:EHaury at aol.com">EHaury at aol.com</A> wrote:
> >> 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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