But what would happen if the airspeed indicator should fail? Can you still fly the plane with confidence? Is this a reason to panic? Pull the Big Red Handle?
Airspeed indicators are very reliable but they sometimes do fail to function properly. And it doesn't take much to render one inoperative. A tiny drop of water or the remains of a bug that get inside the instrument, or a stopped-up pitot tube ... simple little things can remove the ASI from your inventory of usable instruments.