After two crashes of Boeing 737 MAX airplanes caused by faulty readings from a single angle of attack sensor, the Federal Aviation Administration (FAA) has cautioned airlines, aircraft maintenance companies and manufacturers they need to carefully maintain the sensors, according to an online report on the Seattle Times.
The FAA reportedly said in a notice, “It is imperative that all operators are aware of the criticality of AOA sensors and the potential for damage during normal operations, maintenance procedures, servicing procedures, and any other procedures around an aircraft.”
The angle of attack is the angle between an airplane’s wing and the oncoming air flow. According to the report, an angle above about 14 degrees is considered too high and will cause the air stream flowing around the contours of the wing to suddenly detach from the wing surface. This could cause the plane to lose lift and begin to fall—a condition known as stalling, the article said.
According to the report, the FAA notice recommends that all personnel involved “review current procedures identified in their appropriate operational, maintenance, or servicing manuals … around AOA sensors.”
The notice reportedly suggests that the failure of the AOA sensors on the Lion Air MAX in Indonesia last October and then the Ethiopian Airlines MAX in March is one focus of several independent reviews of the crashes. Both crashes together accounted for 346 deaths.