Originally Posted by
ShyTorque
What's wrong with the tried and tested method of: "The correct attitude + correct power setting = correct speed?"
Having said that, at very low speeds landing away from an airfield (helicopter) I monitor the GPS groundspeed against the IAS to determine/confirm into wind or downwind on the approach.
Fully agree. That are the procedures made by the producer of the aircraft. It does not state "pull your phone and check the GPS speed for X-reference". Why? Well, every commerical pilot should be able to answer this question for himself. If it goes Ultralight/Light, why not. This things go so slow, huge stall margins, no harm to use a GPS GS there. But at airliner level it seems very unprofessionel - "children of magenta" springs to mind here. After flying "raw data" with FMC it may make perfect sense for some to use a GPS GS to figure out WHICH IAS indicator is the working one(and this is the goal of pitch/power values x-referenced for altitude, weight, configuration).
My advise, if it comes to that in real life - follow published procedures. It will keep your a** safe if you make it throught the "event"(which you should IF you follow unreliable airspeed procedures, they work like a charm(at least in Boeings and old Airbus(A300, do not know the new ones)).