This SAE Aerospace Standard (AS) provides guidelines for the functional, performance, qualification and acceptance testing, and documentation requirements for the components of an airborne engine vibration monitoring (EVM) system which is intended for use as a turbojet engine rotor unbalance indicating system, per FAR 25.1305 (D)(3) on transport category airplanes. For the purpose of this document, this means a system which can provide real-time flight deck displays of engine vibration caused by rotor unbalance, throughout the flight envelope, which are suitable for: a Relating to engine vibration limits (where such limits are specified) b Use in ice shedding procedures c Helping the flight crew to determine which engine has the higher level of vibration, following an engine damage event. As a minimum, the functional capability for such a system shall include the ability to compute and display vibration levels specifically related to the rotational speed(s) of the engine rotor(s).