Re: Boeing 767 main gear tilt

Date:         04 Aug 97 21:28:54 
From:         faurecm@halcyon.com (C. Marin Faure)
Organization: Northwest Nexus Inc.
References:   1 2 3
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In article <airliners.1997.1625@ohare.Chicago.COM>, mikeh@zeta.org.au
(Michael Hore) wrote:

> On the 777, the same layout is used, but as C. Marin Faure
> mentioned, the bogie is powered into a nose-up position when
> the gear is extended, which allows a better absorption of
> landing energy.  When the gear retracts, the bogie first tilts
> into a nose-down position which is similar to the normal 767
> position.  From photos (I haven't had a chance to see one
> for real yet), this repositioning happens at the same time
> as the gear doors open.

This is not quite correct.  The 777 main trucks are not powered to a nose
down postition at gear retraction but to a wheels-level position.  I have
seen this not only during the functional test cycles in the factory but on
film from our chase planes.

Also, while a rearward-slanting gear as on the 747, 777, etc. LOOKS like
it would allow a smoother landing, I'm not sure it really makes any
difference which way the gear slants.  The initial contact point is simply
the bottom of a tire hitting the runway.  If the next action is the
forward set of wheels pivoting down to contact the runway or the rear set
of wheels pivoting down to hit the pavement, I don't think it really
matters. The smoothness of a landing is determined by the pilots (or
autoland system's) ability to minimize the vertical speed of the tires
that hit the concrete, and the action of the oleo struts or whatever the
vertical shock absorbing components in a jetliner are called.  Which way
the gear happens to tilt when hanging free during the approach I don't
think makes any difference to the actual landing impact of the plane,
although an aft slant "looks right" to those of us watching from the
ground.

C. Marin Faure
  author, Flying A Floatplane