Boeing Co. is preparing to send a safety warning to operators of its new 737 Max jets in response to the investigation of last week’s fatal crash off the coast of Indonesia that left 189 dead, said a person familiar with the matter.
The bulletin from Boeing will alert airlines that erroneous readings from a flight-monitoring system can cause the planes to abruptly dive, said the person, who asked not to be named discussing details of the manufacturer’s plans. Boeing will warn pilots to follow an existing procedure to handle the problem, the person said.
The warning is based on preliminary findings from the accident involving a Lion Air jetliner, the person said. Under some circumstances, such as when pilots are manually flying, the Max jets will automatically try to push down the nose if they detect that an aerodynamic stall is possible, the person said.
One of the critical ways a plane determines if a stall is imminent is a measurement known as angle of attack, which is a calculation of the angle at which the wind is passing over the wings.
The Lion Air 737 Max 8 dove into the Java Sea on Oct. 29 minutes after takeoff, nosing downward so suddenly that it may have hit speeds of 600 miles an hour before slamming into the water. The pilots radioed a request to return to Jakarta to land, but never turned back toward the airport, according to Indonesia’s National Transportation Safety Committee and flight-track data. The committee said they were dealing with an erroneous airspeed indication.
Indonesia’s transport ministry has scheduled a briefing at 12:30 p.m. in Jakarta on Wednesday to share updated information on the Lion Air accident.
It wasn’t immediately clear if the airspeed issue had any connection with the angle-of-attack matter. A spokesman for Chicago-based Boeing couldn’t immediately be reached for comment.
In a statement Nov. 5, the Indonesian transportation-safety committee called on the U.S. National Transportation and Safety Board and Boeing “to take necessary steps to prevent similar incidents, especially on the Boeing 737 Max, which number 200 aircraft all over the world.” The committee is charged with finding the cause of the crash.
While additional details of the bulletin aren’t known yet, the warning is the first concrete action to come out of the accident investigation. Boeing has an existing procedure that allows pilots to continue flying in the event that angle of attack readings become erroneous.
The Chicago-based planemaker has delivered 219 Max, the latest and most advanced 737 jets, since the new models made their commercial debut last year with a Lion Air subsidiary. Boeing has more than 4,500 orders for the airliners, which feature larger engines, more aerodynamic wing and an upgraded cockpit with larger glass displays. The single-aisle family is Boeing’s biggest source of profit.
Aircraft and engine manufacturers routinely send bulletins to operators noting safety measures and maintenance actions they should take, most of them relatively routine. But the urgency of a fatal accident can trigger a flurry of such notices.
After an engine on a Southwest Airlines Co. plane fractured earlier this year over Pennsylvania, killing a passenger, CFM International Inc. issued multiple bulletins to operators of its CFM56-7B power plants.
In addition, aviation regulators such as the U.S. Federal Aviation Administration and the European Aviation Safety Agency often follow such actions by mandating that carriers follow the bulletins.