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<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff size=2>Whoa
Whoa-- I just got out my book and looked. NOWHERE does it use the word "before"
or "prior". It says</FONT></SPAN></DIV>
<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff size=2>"Snap
Roll is the <STRONG>simultaneous</STRONG>, rapid autorotation in the pitch, yaw
and roll axes of flight...."</FONT></SPAN></DIV>
<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff size=2>I'll
grant that it then goes on to talk about an "initiating break", I don't think
that precludes that break in pitch occuring simultaneously with rudder induced
yaw and roll. Especially since the opening definition uses the word
simultaneous.</FONT></SPAN></DIV>
<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=690025400-14042004><FONT face=Arial color=#0000ff size=2>Just
because the nose breaks up doesn't mean the airplane is stalling either. I don't
think my Focus will stall if I just pull back hard on the elevator, it just does
a tight loop. But kick full elevator and rudder, it certainly does stall (and
snap) then! </FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> discussion-request@nsrca.org
[mailto:discussion-request@nsrca.org]<B>On Behalf Of </B>David
Lockhart<BR><B>Sent:</B> Tuesday, April 13, 2004 1:20 PM<BR><B>To:</B>
discussion@nsrca.org<BR><B>Subject:</B> Snaps<BR><BR></FONT></DIV>
<DIV><FONT face=sans-serif size=2>Interesting discussion RE
snaps.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </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><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </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>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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