[NSRCA-discussion] 747 Snap Entry?

[John Gayer]

Tom,
You can do a slow roll in a 747 training  simulator. I've never done it 
without at least 1000' altitude loss. Done slow rolls in 
747,787,737,DC-10,MD-11,MD80/90 simulators and others. They will not 
hold knife-edge, although I've never really taken the time to set up a 
simulator with minumum weight or less, aft CG and see exactly what they 
are capable of. I don't believe there is enough side-force generated to 
support the weight.when in knife-edge and the roll-coupling is ferocious.
Typically, there is a crash program in these sims which need to be 
disabled, at least for my flying, motion system off is also a good idea.  :)
Did your trip to the states come off? I don't recall hearing anything 
about it.
Cheers
John
Koenig, Tom wrote:

> 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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>>
>> 
>>
>>    
>>
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