Re: barrel roll in 727 ?!!

From:         marzuola@great-gray.owlnet.rice.edu (Steven Joseph Marzuola)
Organization: Rice University
Date:         08 Aug 96 12:11:46 
References:   1
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 : On 29 Jul 1996, Ian Kershaw wrote:
 :
 : > Tex Johnson, test pilot at Boeing rolled the prototype 707 over Seattle
 : > in from of asembled crowds watching the power boat races. The maneuver
 : > actually has the plane in a 1g state all the way round.

I was told early in my piloting days that a pilot intentionally rolled
a 747 at night while crossing the Atlantic with a load of passengers,
on a bet with his co-pilot, and nobody in back ever noticed.  Whether
anybody would actually do this, I sincerely doubt.  But for years I
wondered whether it was possible.

The topic of such a 1g roll arose sometime a year or two ago in
another newsgroup.  I put pencil to paper, and did what I believed was
all of the math necessary to answer the question: How much altitude
would an aircraft lose during a "true 1g roll"?  The answer is, the
same as it would lose during a free fall during the same length of
time, i.e. 1/2*g*t^2.

However, somebody else pointed an omission on my part, and we
determined that the downward velocity at the end of the roll would
also be the same as that at the end of a free fall, that is, g*t.
Furthermore, this speed will always increase.  It will be impossible
to stop the downward motion without applying *more* than 1g.

Playing with it some more:

Given a aircraft, initially in level flight, that undergoes a 360
degree roll, while keeping its fuselage essentially horizontal: It is
impossible to execute this maneuver so that a passenger inside always
feels between 0 and 1g, pulling her/him straight "down" (to the floor
of the plane), without eventually colliding with the ground.

I can dig up and post my calculations (just a little calculus).

In summary, whatever Tex Johnson did, he experienced either negative
g's or positive g's greater than 1, or both.

Any comments?



--
Steve Marzuola (marzuola@owlnet.rice.edu)
               The race is not always to the swiftest, nor the contest
               always to the strong, but that's the way to bet.