The pilot and gunner altimeters display the helicopter height above sea level in feet. The altimeters are supplied power by the dc essential bus and protected by the ALTM circuit breaker. The altimeter does not provide altitude reporting. The altimeters are connected through piping to static pressure ports to sense atmospheric pressure. An external adjustment knob is provided to make compensation for variations of prevailing barometric pressure. The altimeters are equipped with vibrators to eliminate pointer sticking due to friction error. The vibrators are operated by 28Vdc through the ALTM circuit breaker.