An instrument for use in a helicopter includes a performance calculator typically housed in a control unit (16) and a display unit (14). The system receives electronic indicia (44) of current altitude, air temperature, fuel on-board and engine manifold pressure, and calculates (in substantially real time) the following: (a) maximum amount of power the engine can produce at these conditions; (b) limitations set by the aircraft manufacturer on power that may be used; (c) maximum airspeed and hover weight allowed under these conditions; (d) percent power used (the "torque gauge"); and (e) amount of power remaining available. The power display unit has an arcuate series (24) of light elements fitted around the standard MP (20) gauge to provide graphic indicia (26, 28, 30) of power available for the pilot to easily see and interpret.