NTSB Calls for Checks of Collins AHRS in more than 7,000 Airplanes
The NTSB has sent a letter to FAA Administrator Marion Blakey recommending that the Rockwell Collins AHC-85 attitude heading reference system (AHRS) computers in more than 7,000 regional airliners and business jets be tested to ensure the units won’t fail during aggressive pitch and roll maneuvers. The Safety Board action stems from a March 2001 incident in which the crew of a Comair EMB-120 Brasilia lost control in icing at 17,000 feet and subsequently experienced near simultaneous failures of the pilot’s and copilot’s EADI displays. The NTSB later determined that the screens “blacked out” because of a loss of data from the AHRS computers. The crew was able to regain control after breaking out of the clouds at 10,000 feet. No one on board was hurt in the upset, but there was severe damage to the airplane’s tail (the EMB-120 rolled inverted three times before recovery). The Safety Board noted that the loss of AHRS data may “inhibit the recovery of an airplane, especially during an upset when attitude indications are most critical.” Testing by Collins after the incident showed the AHRS computers failed before reaching their tolerance of 128 degrees per second of roll. Collins manufactured the AHC-85 computers between 1985 and 2000. A spokeswoman for the Cedar Rapids, Iowa avionics maker said the company has started consultations with the FAA to determine what, if any, action should be taken as a result of the Safety Board’s recommendation.