The FAA has issued an emergency airworthiness directive (AD) that has prompted the grounding of Cirrus SF50 Vision Jets, requiring a replacement of the aircraft’s angle of attack (AOA) sensors before operators can begin flying them again.
The AD was prompted by Cirrus reporting three incidents on Cirrus Model SF50 airplanes of the stall warning and protection system (SWPS) or Electronic Stability & Protection (ESP) System engaging when not appropriate, with the first incident occuring in November 2018 and the latest in April 2019. The SWPS or ESP systems may engage even when sufficient airspeed and proper angle of attack (AOA) exists for normal flight. The SWPS includes the stall warning alarm, stick shaker, and stick pusher. «An uncommanded pitch down may be difficult to recover from in some flight regimes with potential fatal consequences», the FAA noted. Cirrus and Aerosonic (manufacturer of the technical standard order AOA sensor) have identified the probable root cause as an AOA sensor malfunction due to a quality escape in the assembly of the AOA sensor at Aerosonic.