[NSRCA-discussion] 747 Snap Entry?

[Koenig, Tom]

 Hey John,

Out of interest.....has anyone ever attempted a snap in an airliner???

I have heard of a captain doing a slow roll in a 747....but a snap? Is
it possible?? What does a simulator do when pushed to such limits ( I
know a simulator cant snap BTW...well, I assume any way LOL!!)

Tom

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of John
Gayer
Sent: Tuesday, 1 July 2008 11:42 AM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Snap Entry

Actually a snap can occur without any aileron input...but I challenge
anyone to show a pattern ship doing a snap roll on a 45 degree downline
without ailerons.

The approach snap can occur with only the use of elevator and it
involves one wing panel stalling before the other. Try an approach with
crossed controls(aileron/rudder with some power. pull the nose up
gradually and see which wing drops. It will be the wing with the aileron
trailing edge down. This is contrary to what we see in a pattern snap
roll which always snaps in the direction of the aileron deflection thus
indicating the lack of any stalled condition

John

seefo at san.rr.com wrote:

>Just to stir the pot a little further..
>
>I'm not sure a contemporary pattern plane can generate enough pitch
rate to reach critical angle of attack and properly perform a snap roll.
I think it's far more likely that we're seeing nothing but a heavily
yawed aileron roll, with the pitch break only being shown to judges to
convince them there is actually a stall happening, when in fact there is
not. 
>
>If a snap cannot occur using ONLY elevator and rudder, then the wing is
not stalling. Aileron inputs into a snap actually inhibit flow
separation, as the inboard wing angle of attack is drastically reduced,
and the outboard wing AoA is drastically increased. 
>
>But since there is no way to actually determine what is happening
aerodynamically on an F3A airplane, the best a pilot can do is fly the
airplane to what the judges expect to see based upon the rules. It
really doesn't matter what the control inputs are if the airplane LOOKS
like it's doing the right maneuver.
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