The Viking 400 Series Twin Otter will soon come equipped with a Safe Flight angle-of-attack (AoA) indicator as standard equipment. The TSO’d system consists of a lift transducer, computer and a speed indexer. The speed indexer provides the pilot heads-up guidance to approach AoA. The computer provides Arinc outputs to drive low airspeed awareness and AoA displays on the primary flight display. Safe Flight’s lift transducer is a heated leading edge sensor and is cleared for flights into known icing conditions.