[NSRCA-discussion] 747 Snap Entry?

Tue Jul 1 18:25:31 AKDT 2008

I love the "only once" part of that. It brings up memories of an old Chuck Yeager flight sim on computer... when you did anything crazy you just got a little message at the bottom of the screen that said "Wings sheared off"

Matt
  ----- Original Message ----- 
  From: Keith Hoard 
  To: General pattern discussion 
  Sent: Tuesday, July 01, 2008 5:42 PM
  Subject: Re: [NSRCA-discussion] 747 Snap Entry?

  During initial training I was told stories about pilots that would extend the flaps to 2 degrees at altitude to increase fuel efficiency, but to do that you have to pull a couple circuit breakers to disable the leading edge devices (LED's) which are limited by Boeing from being extended above 20,000 feet.  When you do this stunt, you are risking air pressure getting up under the spoilers and causing them to float - thus negating what you're trying to accomplish.  Also, the elevator trim is controlled by the autopilot at altitude . . . if you try to trim the nose up the autopilot will kick itself off.  I could see where an unbriefed pilot resetting the LED circuit breakers at altitude could cause really hideous problems. . . but I highly doubt the Split-S (with 2 of 4??) maneuver . . . more likely a 7.5 on their Straight Flight Out followed by a Zero'd flight due to the LED's departing the aircraft.

  Besides, the flaps and trim have no effect on the CG of the airplane. . . it is a function of how the plane is loaded and the current fuel load - which by the way moves the CG forward during flight unless your S/O does something really, really wrong on the fuel panel.   My company is currently trying to load the airplanes with an aft CG for fuel efficiency.

  Now, back to the original subject. . . will a swept wing commercial transport aircraft perform a proper snap roll? . . . . My vote is "only once". . .

  On Tue, Jul 1, 2008 at 6:03 PM, Gerald Gallagher <ggall at bellsouth.net> wrote:

    I was a pilot with TWA & knew the captain that is accused of this, also a
    TWA Pilot. To this day he denies this ever happened & so do the 2 other crew
    members that were flying that 727. The loss of altitude was, according to
    the three crewmembers aboard was clear air turbulence. I believe the pilot,
    but I am prejudice.

    Jerry Gallagher

    -----Original Message-----
    From: nsrca-discussion-bounces at lists.nsrca.org
    [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
    rcmaster199 at aol.com
    Sent: Tuesday, July 01, 2008 5:47 PM
    To: nsrca-discussion at lists.nsrca.org
    Subject: Re: [NSRCA-discussion] 747 Snap Entry?

    A few of us were discussing just such an occurence recently which
    apparently happened by accident and darned near crashed the plane. Dean
    remembered the details which went something like this:

    The pilot of the 727 about 20 years ago had the plane trimmed as far
    aft as possible and had inputed a bit of flap to use fuel most
    efficiently. The co-pilot, soon after returning from a visit to the
    loo, saw the trimmed flap and flipped the switch to return the flap to
    neutral. This action immediately made the plane too tail heavy which
    made the plane do a pretty violent half snap to inverted. The pilot
    lost close to 25k feet pulling the plane out of the dive, which he did
    successfully but not before deploying the gear to slow the crate down.
    That had to be some kind of experience

    Legend has it that the pilot then went straight to loo himself to
    change his britches (G)

    Matt

    -----Original Message-----
    From: Koenig, Tom <Tom.Koenig at actewagl.com.au>
    To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
    Sent: Mon, 30 Jun 2008 10:25 pm
    Subject: Re: [NSRCA-discussion] 747 Snap Entry?

     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.
    >_______________________________________________
    >NSRCA-discussion mailing list
    >NSRCA-discussion at lists.nsrca.org
    >http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
    >
    >
    >
    _______________________________________________
    NSRCA-discussion mailing list
    NSRCA-discussion at lists.nsrca.org
    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
    _______________________________________________
    NSRCA-discussion mailing list
    NSRCA-discussion at lists.nsrca.org
    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

    _______________________________________________
    NSRCA-discussion mailing list
    NSRCA-discussion at lists.nsrca.org
    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

    _______________________________________________
    NSRCA-discussion mailing list
    NSRCA-discussion at lists.nsrca.org
    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

  -- 

  Keith Hoard
  Collierville, TN
  khoard at gmail.com

------------------------------------------------------------------------------

  _______________________________________________
  NSRCA-discussion mailing list
  NSRCA-discussion at lists.nsrca.org
  http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20080702/2785f27f/attachment.html>