Use of Rudder for Airliners
peterw...@hotmail.com
The final report on the crash of AA flight 587 concluded that
overly aggresive use of the rudder by the crew brought the
aircraft to a yaw angle and rudder deflection where the aerodynamic
force on the vertical stabilizer caused it to break off, putting
the aircraft out of control. Various articles by Peter Garrison
and others state that the exact envelope of safe operation of
the rudder and stabilizer are not made very clear by the aircraft
manufacturers and that many airliner pilots are not in fact
aware of just what that envelope is.
During the public discussion on this issue, one pilot wrote
in a in a letter to the editor (might have been in AWST)
that as far back as the DC-3 pilots had been aware that you
couldn't just throw in full rudder deflection on an
airliner as if it were a Gypsy Moth. The stabilizer/rudder is
an airfoil, and it will break when subjected to a certain force.
This force in turn is a function of several parameters, most
importantly dynamic pressure or indicated airspeed, yaw angle,
and lift coefficient (determined by the rudder angle; I have
heard that full rudder deflection increases the lift coefficient
by about 50 percent). How difficult would it be to set up a
simulator with accurate information about the behaviour of an
airliner at extreme yaw angles so as to teach pilots to
recognize and avoid situations where they are verging on
stabilizer failure?
Thank you,
Peter Wezeman
anti-social Darwinist
"Forty gallons; not enough to measure, really."