noun
stalling speed
Aviation term: the minimum airspeed at which an aircraft can maintain level flight; below this speed the wing stalls.
パイロットは失速速度を下回らないように注意する。
The pilot is careful not to drop below the stalling speed.
失速 means 'stall' (loss of lift), while 失速速度 is the specific speed at which stalling occurs.
Compound of 失速 (stall) + 速度 (speed). A straightforward technical term in aviation.