Re: Crosswind landings in 777

Date:         29 Apr 99 22:10:18 
From:         "Mark Rogers" <mmrogers@tcsn.net>
Organization: Verio Northern California's Usenet News Service
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Ken Ishiguro <kenish@earthlink.net> wrote in article
<airliners.1999.407@ohare.Chicago.COM>...
>
> There are two methods of making a crosswind landing.  One is to crab
> into the wind and track the runway centerline.  Right before touchdown
> the crab is cancelled to remove sideloads on the MLG.  The second method
> is to do a forward slip so that the slip rate cancels the crosswind
> component. (This is also called the "wing low" method).

There is really only one method in a swept wing jet.  The aircraft is
crabbed into the wind until the flare.  At that point, the nose is pointed
straight down the runway with rudder, and the unwind wing is slightly
lowered to stop the drift associated with the rudder input.  Essentially,
it's the "slip" method, just applied once the aircraft has entered the
flare.

If the slip is applied early (as in light aircraft), the aerodynamics of
the swept wing coupled with possible spoiler deployment (for roll
assistance with the aileron input) will create a significant increase in
sink rate.  Even when the slip is performed in the flare, a sink rate
develops; this is simply countered by slightly delaying when the thrust is
reduced to idle, and with a small amount of pitch.

> I am accustomed to the crabbing method being used on airliners.
> However, I noticed that the 777's were using the sideslip method.  Why
> is this method used on the 777's and no other types?  (All the 777's I
> saw landing were UA- is it peculiar to UA training)?

The same techniques are used on the 777 as any of the other airlines.
Perhaps because the 777 is so much heavier than most of the other types,
the "crabbing" method was not as readily apparent.

--Mark Rogers