airspeed

I can understand relying on airspeed instead of GPS-measured groundspeed, because airspeed is important.

For example, the ability to convert engine shaft horsepower to usable thrust is very poor at zero airspeed.

The loss of airspeed from extracting energy out of the wind stream is more dangerous than gliding.

What is impressive about the An-2 is its super-slow stall speed (the minimum airspeed necessary for flight).

Yep, the forward airspeed needed to generate lift is relative to the aircraft, not to the ground.

Take for instance the Air France 447 crash: the first problem was freezing of pitot tubes to measure airspeed.

Of course, you gotta keep a real close eye on your altitude and airspeed doing that.

Because you might want to give the user information about the flight (altitude, airspeed, cameras...).

Full size planes just torque roll uncontrollably when they get near zero airspeed.

Below that indicated airspeed you pull back on the throttle or you're going into a turn at best or more likely a spin.

Then use the GPS to create an estimate of airspeed, but put usable speed on the display so the pilot doesn't loose control.

You can over-G an F-16 at 4G depending on airspeed and loadout.

AF447 was flying in "alternate law" with limited (or maybe no) automation capability due to iced over airspeed pitot tubes.

Even a few dozen bytes worth of data every minute about current position, heading, airspeed, heading and speed of the wind is enough to reduce this theoretical "huge distance" (that is much smaller than what people have to deal with without tracking data) to a relatively small cone that can be searched effectively.

"but what would happen if one engine were at 0% and another 100%" Part of earning your multi-engine cert is memorizing all manner of different airspeed limits for that kind of situation.

To address a crosswind taking you off course, you simply turn ("crab") into the wind, but the airplane stays coordinated and you sum the aircraft airspeed vector with the airmass vector and adjust until your ground track is taking you where you want to go, even though the nose of the airplane isn't pointing straight along the ground track.