WASHINGTON—The Air Line Pilots Association (ALPA) has called on FAA and NTSB to assist in providing information on an automated pitch-control system suspected of possibly contributing to the October fatal crash of a Lion Air Boeing 737 MAX 8.
In a Nov. 15 letter addressed to FAA Acting Administrator Dan Elwell and NTSB Chairman Robert Sumwalt, ALPA President Tim Canoll requests “immediate help and assistance in clarifying the issues” associated with the pitch-control system—a reference to the 737 MAX maneuvering characteristics augmentation system (MCAS).
ALPA represents pilots at 34 U.S. and Canadian airlines.
A function of the flight control computer, the MCAS activates when an aircraft’s angle of attack (AOA) exceeds a certain threshold based on airspeed and altitude readings, pushing the nose down to reduce the risk of a stall. The system operates only when the autopilot is off, flaps are up and during steep turns. It resets when the AOA falls below the threshold or pilots provide manual horizontal stabilizer trim commands.
Not part of previous 737 designs, the system is a feature of new MAX series airliners, Boeing has acknowledged. But the MCAS is not covered in the MAX flight crew operations manual (FCOM) or in difference training instructions for pilots of earlier 737NGs, operators have noted.
Boeing has issued an FCOM bulletin to 737 MAX operators warning that erroneous AOA data trigger automatic nose-down inputs and emphasizing that pilots follow specific procedures to keep the aircraft from descending uncommanded. The FAA mandated the action in a Nov. 7 emergency airworthiness directive.
“Some media reports indicate that the 737 MAX was designed and certified with a new automatic pitch-control system that was not on previous versions of the Boeing 737. More importantly, however, these reports indicate that information regarding the normal and non-normal operation of this system was not provided to the frontline airline employees—the flight crews and maintenance technicians,” Canoll wrote.
Lion Air flight 610—a 737 MAX 8—crashed into the Java Sea about 13 minutes after departing Jakarta’s Soekarno-Hatta International Airport on Oct. 29, killing all 189 onboard. Analysis of the flight data recorder recovered from the wreckage revealed that the aircraft experienced faulty airspeed and AOA readings on previous flights.
“We understand that this is an ongoing investigation and that additional details will be forthcoming; however, there appears to be a significant information gap, and we want to ensure that pilots operating these aircraft have all of the information they need to do so safely. [T]he lack of critical safety information being provided to the air carriers and frontline operators is concerning,” Canoll said.