fendant:
FWIW and from a Boeing POV - Indicated Airspeed (IAS) on the Primary Flight displays (T-panel in old money) is from the pitots..
GPS ground speed and/or Inertially derived ground speed is usually available to be displayed somewhere if you need it, but it's probably not going to be in your instrument scan and obviously doesn't match IAS 1:1 at altitude, though they can give indications of a trend.
Last edited by wiggy; 25th May 2011 at 09:33.