Re: Boeing 767 main gear tilt

Date:         01 Aug 97 04:04:16 
From:         air-admin@chicago.com (Author's name withheld by request)
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In article <airliners.1997.1584@ohare.Chicago.COM>,
François Airault <fairault@compuserve.com> wrote:
>> The gear tilt "toe down" in order to stow more efficiently.  This allows
>> the main gear well to be shorter, making the cargo holds longer.  This is
>> goodness since longer cargo holds carry more revenue stuff.  A small side
>> benefit is that a shorter gear well makes the airplane slightly lighter
>> and stiffer.
>
>Is this a fact, or are you assuming ? My recollection from the type
>rating is that the gear is hydraulically (normal) or mechanically
>(standby, by the inner doors) untilted while retracting. Looking at the
>767 wheel well, it actually seems that the gear is stowed straightened,
>with the truck parallel to the centerline. In addition, calling the 767
>main gear "short" and "light" is a rather stem way of putting it. It is
>a very complicated design, and the tilted truck is only part of it. I'm
>only curious to understand why (ok, VERY curious now that I have done
>some digging, to no avail).

Gosh, thanks for pointing that out.  I had not actually worked that
program and this was from a conversation with one of the old(er) guys.
I, too, looked up a diagram of the gear stowed and had a talk with a
(different) old engineer.  As it turns out, the 747 gear (a program I
have worked on) stows at an angle.  The 767 stows parallel to the keel
beam.  This is for two reasons, one positive, one negative.  Stowing
parallel to the keel beam gives a slightly longer gear (going with the
rule taller gear is better than shorter gear, all else being equal).
Putting the trucks in at an angle would not have shortened the gear well
because it would not have been enough to drop a full frame bay.  Nothing
happens structurally unless it can drop a full frame bay.  Caveat: all of
this can (and will) change if the size of the tires change significantly.

BTW, there is a hydraulic truck tilt actuator on the 767, for those who
were wondering.

I still stand by my characterization of the 767 gear as relatively
light and simple.  Look at a B-52's gear if you want to see something
really ugly, or one of those commuter tuboprops where the gear retracts
into a nacelle.  Ick!

--
(Author's name withheld by request)