Abstract: A servo motor is coupled through an electric clutch to the needle on a mechanical airspeed indicator. The servo motor is controlled by a signal processor to position the needle to indicate airspeed based on a value calculated from static and pitot pressure indicated by output signals from a solid state transducer. The needle is also connected to an aneroid mechanism that positions the needle based on static and pitot pressure but which is overcome by the servo motor when the clutch is activated. The clutch is deactivated, allowing the aneroid mechanism to position the needle, if a fault is detected by the signal processor.