Not that familiar with the 757 but GPS displays GS. Add or subtract
winds
to
get TAS, then correct for density (divide by SMOE) to get IAS?CAS.
Heard
it
suggested you could also depressurize and use the cabin altimeter for
altitude. Or, convert cabin altitude into aircraft altitude if the
chart
is
available.
Curt

Multiple redundant systems on Commercial jets. Figure out which one is
bad
and turn it off. The standby #3 system is analog and totally separate
if
it's like a 747-400. The captain should have given control to the
copilot
in the turkish aircraft incident.



Well, that's only if you follow the flight manual and common sense.
Just discussed this one in my quarterly refresher. The discussion turned
to
"what if" you lost all airspeed and altitude indications. It was an
exercise
in making us think. It would also be a handy method to double check the
primary instruments, or to have something to do on those long overwaters.
Curt