EASA today issued a Transport Canada airworthiness directive (AD) for Bombardier CRJ700 and CRJ900-series regional jets equipped with certain part number Thales angle-of-attack (AOA) transducers, devices that provide information for the aircraft's stall warning, stick shaker and stick pusher functions.
"The heating capability of several AOA transducer heating elements removed from in-service aircraft has been found to be below the minimum requirement," the AD states.
Transport Canada had also discovered that "a large number" of the transducers repaired in an approved maintenance facility were not correctly calibrated.
"Inaccurate calibration of the AOA transducer and/or degraded AOA transducer heating elements can result in early or late activation of the stall warning, stick shaker and stick pusher by the stall protection computer," the AD states.
The directive calls for operators to replace inaccurately calibrated transducers and periodically check the in-rush current on the others to verify heating capability.
The directive comes one day after EASA issued an AD requiring replacement of certain of Thales-made pitot tubes on Airbus A330 and A340 aircraft in wake of the Air France A330 crash on 1 June. The US FAA tomorrow will issue a similar pitot directive for US-registered aircraft.