redundant airspeed indication
Just a wayward thought from an engineer. We know GPS is not accurate enough to be used as a backup airspeed indicator because it tracks ground speed rather that airspeed. the two are often vastly different. Might it be possible to derive a backup airspeed indication by looking at the doppler shift of weather radar returns? After all, the cloud droplets are suspended in the same air mass that the aircraft is flying through. This would only work when there were echo returns present, but then again those are the times when pitot tubes are likely to be fouled by ice.