“European regulator points out issue with Boeing 737 Max autopilot”

The EASA has drawn up a number of points that Boeing must resolve with the troubled 737 Max before the aircraft can go back into the air. This also includes an apparently identified problem with the autopilot. Bloomberg writes that based on a source.

This concerns a total of five major requirements that the European aviation regulator European Union Aviation Safety Agency has placed on Boeing, Bloomberg writes on the basis of a source who would be familiar with the information. Four of the five requirements set by EASA relate to problems that were already known, but there is also a fifth requirement that concerns problems with disengaging the autopilot in certain emergency situations. Further details on this apparent autopilot problem are still lacking; the source wished to remain anonymous, as EASA’s report is not yet public. EASA was not immediately available for comment. In addition to the five points, the European regulator would also have identified smaller issues, but these would have been classified as ‘not critical’.

The remaining four requirements address the potential difficulty for pilots to manually turn the trim wheels, the unreliability of the angle of attack sensors, inadequate pilot training procedures, and a software problem that would result in a slow or suboptimal microprocessor. As far as is known, the first three points mentioned played a role in the two fatal accidents involving the 737 Max. In October last year, a plane of this type crashed in Indonesia and in March it went wrong again in Ethiopia. A total of 346 people were killed in both crashes.

It is believed that these crashes are at least partly due to the MCAS system, which Boeing has implemented exclusively in the 737 Max aircraft. Based on incorrect data from the angle of attack sensors, the aircraft’s brain probably thought that the aircraft leaned too much backwards and that a stall situation was imminent. To prevent this, the system pushed the noses of both crashed aircraft down considerably. The pilots, who, according to previous reports, had not been trained or had not been sufficiently trained to fly this new type, turned out to be unable to get their aircraft under control in time.

The trim wheels, which are present in every 737 type, probably also played a role in this. These can be used to move the horizontal stabilizers at the tail of 737s relative to the airflow. This changes the downward pressure to make the aircraft fly stably in a straight line, or to get the nose up or down. Reuters previously reported that American and European regulators were aware of an issue with the trim system at least two years ago. Under some circumstances the angle of the nose could not be adjusted electronically via the tiller handle, but the two trim wheels in the center of the cockpit had to be operated manually, which is quite exceptional. The EASA would have approved the 737 Max anyway, because this potential issue would be adequately addressed in training for the pilots. In the end, that probably didn’t happen or not enough.