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Dave:<br>
Everybody who is going to be judging snaps should have your essay
tattooed to the inside of their eyelids! Great!<br>
Now, I don't necessarily have the stature to enter this discussion, but
I have been able to observe something that is directly relevant.<br>
Several years ago at the TOC, there was a maneuver that called for a
double snap roll to the right, right in front of the judges. Easy to
observe for us spectators, too. Everybody (and I do mean exactly
that, everybody) except one competitor had their airplane offset to the
right by one wingspan. Repeatedly this happened, until one competitor
came up and did his double snap AND kept the same upline; his airplane
didn't offset to the right! As can be imagined, it soon came to the
attention of the other competitors, who were mystified as to how he
could do this so well. Finally, one of them said: "I see how he's
doing it!"<br>
And, next flight, (it was in the knowns, of course) the observant one
was also able to keep the same upline, also. It developed that the key
was to apply a little left rudder Immediately before the right
snap(s). Almost impossible to see, but it kept the snaps in the
correct plane. (No pun intended! Honest!) <br>
Hope I'm not muddying the water here, but it showed me that it IS
possible to do.<br>
<br>
Bill Glaze<br>
<br>
David Lockhart wrote:<br>
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<div><font face="sans-serif" size="2">Interesting discussion RE snaps.</font></div>
<div> </div>
<div><font face="Arial" size="2">The way the snaps are currently
defined (correctly I think) requires the aircraft to be stalled in
pitch prior to any rotation in yaw and roll. The break is a required
element of the maneuver (not unlike other maneuvers). As with any
maneuver, I believe it is the pilots responsibility to clearly
show/demonstrate all elements of a maneuver. If a stall is not
demonstrated at the point of entry into a spin, the maneuver should be
scored zero. If a snap does not have a break on the entry, it should
also be scored zero.</font></div>
<div> </div>
<div><font face="Arial" size="2">It is not likely that a good break
and snap entry will occur using a snap switch/button - unless
the elevator servo is much faster than the other servos. What helps
define the break on the entry of the snaps is very fast application of
the elevator input and a very fast elevator servo - lots of throw also
helps (I have used as much as 30 degrees of throw on some planes for
some snaps). The result is a very rapid change in the pitch attitude
of the plane (like the definition says) with very little displacement
in track. If the airplane is truly stalled at the time of rudder (and
aileron) application, the change in track in yaw will be minimal, if
any. It is not easy to get a modern day pattern plane to perform a
nice snap - as has been noted, they are very stable in pitch, generally
have fairly small elevators, very light wing loadings, and generally
have control throw setups that lack the authority to initiate a clean
break. Most pattern planes I see on the flightline quite simply won't
break cleanly because they lack the elevator throw to do so.</font></div>
<div> </div>
<div><font face="Arial" size="2">If the plane displaces from the
entry track during the break and then resumes a parallel track after
the snap, that is ok (and actually required depending on ones
interpretation of the FAI book). If the track of the plane does change
slightly during either the break or after the snap, this can be
downgraded - and the downgrade could be minimal to the point of not
reducing the maneuver score due solely to the change in track. A "10"
is not a flawless maneuver, it is a maneuver which is perfect or
contains flaws that are not substantial enough to warrant downgrading
to a 9.5 (or 9 in FAI).</font></div>
<div> </div>
<div><font face="Arial" size="2">The rotation rate of the plane
during the snap depends on many factors - including design parameters
of the plane (wingspan being a biggy) and the pilot technique. In
general, the greater the break (deeper the stall), the slower the
rotation of the plane will be. If the left/right wings are stalled
equally at the break, the rotation rate is largely determined by the
amount of rudder applied (which accelerates one wing panel forward and
the other aft resulting in asymmetric lift which causes the rotation
about the roll axis). The same airplane that does not break cleanly in
pitch (reduced throw, poor technique) will likely break in yaw -
meaning the wing panel accelerated forward by application of the rudder
never does actually stall, and the wing panel accelerated aft does
stall and the asymmetry in lift again results in rotation about the
roll axis. The difference between these two scenarios is that the
first contains the element of the break and is a scorable snap. The
second scenario does not contain the element of the break and should be
scored zero.</font></div>
<div> </div>
<div><font face="Arial" size="2">What is interesting to note (and
I've many witnesses to this at the practice field), is that the
difference in the rotation rate of the snap is not effected noticeably
by the amount of aileron used - 10 degrees or 15 degrees of aileron
throw result in the same rotation rate - IF the snap was entered from a
stalled condition. If I substantially reduce the elevator throw (and
the break becomes very, ahem, questionable), the amount of aileron used
has a dramatic effect on the rotation rate. </font></div>
<div> </div>
<div><font face="Arial" size="2">The entry speed of the plane is not
a judging criteria. With proper setup and technique, the airplane can
be made to break in pitch at virtually any airspeed (with commensurate
increases in stress at higher speeds) - but the break is usually slower
and easier to judge at lower speeds.</font></div>
<div> </div>
<div><font face="Arial" size="2">For several years at the US NATs, I
received comments from both pilots and judges regarding the crispness
of my snap entries and the easily visible cone of the nose/tail during
the snap. Many of the pilots suggested I should "back off" the snaps
and exaggerate the break less to make them easier to do (even tho I
rarely missed an exit). In general, my scores on maneuvers containing
snaps were not very good (relative to other maneuvers in the flight).
Since that time, I have "toned" down the snap entry and the snap itself
- the break is now much less defined and harder to see, and the snap
itself is much more axial, and the rotation rate is faster (and after
adapting, I miss the same number of exits - none on a good day
<G>). My scores have generally increased - my conclusion is that
very few judges are either capable of seeing the break, looking for the
break, understand the break, or have the confidence to downgrade (to
zero) a snap which does not demonstrate a break. I believe both styles
of snaps I flew are within the rulebook definition - but one scores
better than the other - I guess I'll continue to fly the style that
scores better, even tho I think it is the style that is harder to judge.</font></div>
<div> </div>
<div><font face="Arial" size="2">And, if I've offended any of the
aerodynamic purists out there with my oversimplification of the
dynamics of a snap, my apologies - I didn't think additional detail
about the aerodynamics were of help in this discussion.</font></div>
<div> </div>
<div><font face="Arial" size="2">Regards,</font></div>
<div> </div>
<div><font face="Arial" size="2">Dave Lockhart</font></div>
<div><font face="Arial" size="2"><a href="mailto:DaveL322@comcast.net">DaveL322@comcast.net</a></font></div>
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