[NSRCA-discussion] Snap

[Jim Woodward]

Adam, Nat,

Great comments.  I personally think a small part of the total issue is that
for the majority of pattern pilots the snap roll is more of a theoretical
problem and maneuver encountered few time, and without the expectation of
making the total maneuver as "precision" as it can get.  With the US Nats
change this year to having F07 on Wednesday, I am (and I'm sure a lot of
other FAI pilots) are practicing the sequence quite a bit and it has 4
maneuvers with 5 snaps in the sequence (positive and negative, 1 or 1.5
revolutions).  So, for this particular sequence, the pilot must do
everything you can to retain every point of the whole maneuver.  The more
you practice it, the better you can become with wind correcting, snapping
within the geometry of the maneuver, and at the different airspeeds in that
portion of the maneuver.  So, the tendancy (again, my thinking here), is for
this class to basically converge on the style snap roll that will allow you
to "retain" the most points for the total maneuver, potentially judged by
folks with instruction or opinions like what we've seen here:  Pilot must
show me a pitch break, Pilot must demonstrate to me...  When I hear someone
say this particular sequencing of the snap - it sounds more like, '...
looking for pilot to fly off line, then snap, then correct back to line.'  I
think that keeping up with the pilots fast fingers and fast responding
airplane, while applying the "must see X before Y" criteria would be
difficult for judges.  Also, I think Nat Penton's description from earlier
in the post hits the nail on the head.  

Thanks,
Jim W




-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Adam Glatt
Sent: Tuesday, July 04, 2006 2:26 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Snap

Bob, my personal experience tells me that such a snap roll is only 
possible with little to no elevator, and decent amounts of aileron and 
rudder.  This shouldn't be a great surprise to anyone who has thought 
about the control inputs we prescribe to perform a snap.  Elevator input 
causes the plane to pitch, and pitch causes the plane to displace from 
its former path, whether the wing is stalled or not.  Rudder causes the 
plane to yaw, but yaw is much less effective at causing the plane to 
displace from its former path.  Rudder during a roll forces the tail and 
nose to rotate around the flight path.  What two things can a judge or 
pilot look for during a roll to determine if it is a standard roll, 
barrell roll, or a snap roll?  The first is the tail being at an angle 
that isn't the flight path and then not rotating around the flight 
path.  The second is the CofG staying on a rather straight path.

A stalled wing (due to elevator application) produces a ton of lift.  
That lift is going to drastically move the CofG off the previous flight 
path.  This is why I advocate and practice very little elevator 
deflection during a snap.  Meeting the rules requires strong elevator 
application to begin the snap, and it also _requires_ releasing most of 
that elevator during the rotation.

Of course, this is all just talk and typing.  Most important is to 
ensure your snaps don't tempt judges to whip out the big zero.  And that 
you can hit wings-level every time.  Jeez, I better keep practicing...

-Adam

Bob Richards wrote:
>
> */Nat Penton <natpenton at centurytel.net>/* wrote:
>
>     When the stall occurs lift only diminishes, it does not go to zero.
>
> Agreed, and therefore the CG of the plane can't travel a straight line.
>  
> The "break" will cause the the wing to go through its maximum lift 
> AOA. That alone will cause the path to deviate. Once "stalled" the 
> wing is still lifting, 3D flying proves that.
>  
> I recently flew a plane that was being video taped, and performed 
> several snap rolls coming straight towards the camera. When the 
> playback was slowed down, it was apparent the plane was NOT following 
> a straight path. The plane obviously stalled, and autorotated, but the 
> path was a spiral.
>  
> I would like for someone to produce a video of a snap roll, flown 
> straight towards or away from the camera, where the CG stayed on a 
> straight path.
>  
> Bob R.
>  
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