The safety of the Boeing 737 MAX was assessed by Boeing itself. Neither the regulator nor the pilots knew about its features

The safety assessment of the new Boeing-737 MAX aircraft control system was actually carried out by Boeing itself, and not by the regulator, the US Federal Aviation Administration (FAA). This is what led to the fact that the critical mode stabilization system (MCAS), the work of which probably provoked both crashes of aircraft of this type, came into operation with dubious design solutions and hidden features, according to the Seattle Times .

More. Boeing engineers and FAA specialists spoke to the publication about the problems of MCAS even before Ethiopian Airlines' second Boeing-737 MAX crash on March 10, which killed 157 people. Also before the disaster, the newspaper informed the regulator and the company about the details of the publication and requested comments.

In 2015, the FAA was in a hurry to certify the Boeing 737 MAX because the American aircraft was almost a year behind its European competitor, the Airbus A320neo, Seattle Times writes. Due to a lack of funding and manpower, the FAA increasingly shifted the writing of safety reports to Boeing specialists for subsequent approval, and at some point the MCAS safety report got into this mountain of paper.

According to the Seattle Times, in a report written by Boeing developers:

the possible angle of deviation of the aircraft stabilizer for a dive by the MCAS system is four times underestimated;
it is not stated that the system can be reactivated after each pilot reaction. This did not allow assessing the real risk of the aircraft going into a dive;
the threat of incorrect operation of the system is lower than "catastrophic". However, even with a "dangerous" threat level, the MCAS system should not have relied on data from a single sensor.

Boeing had a good reason not to focus on the features of the new aircraft , notes the Seattle Times. One of the key marketing advantages of the Boeing 737 MAX is the rapid retraining of pilots from the previous generation Boeing 737 NG, saving airlines "millions of dollars" in retraining. It essentially boils down to an hour of familiarization on the tablet screen, even without flying on a flight simulator.

It is for this (and the acceleration of certification) that Boeing has gone to the lengths to break its longstanding tradition of keeping the pilot in complete control of the aircraft. One of the objectives of MCAS was to make the Boeing-737 MAX behave like a Boeing-737 NG, despite the significantly larger and far forward engines.

Only after the Boeing-737 MAX crash of the Indonesian airline Lion Air on October 29, 2018, did the FAA learn that the system, bypassing the pilot, could shift the stabilizer not by 0.6 degrees, as in the report, but by as much as 2.5, moreover, to do this several once. In addition, it turned out that she relied on data from one angle of attack sensor, which was faulty on the crashed plane. “None of the engineers knew about the new limits,” said the FAA specialist.

Many pilots only became aware of the existence of MCAS after the first crash . Boeing assures that the disaster would not have happened if the pilots had followed the standard recommendations for “stabilizer departure”, thereby disabling the automation.

The problem is that the behavior of the aircraft when the stabilizer leaves is different from what MCAS gave, and the pilots of Lion Air could not understand what was really happening. Worse, the activated system did not allow to simply “pull out” the aircraft with the helm. As a result, having compensated for the deviation of the stabilizer by the system about 20 times and never turned off the automation, the pilots lost control over the aircraft.

Last week, as the similarities between the two crashes came to light and Boeing-737 MAX flights were suspended worldwide , the company promised:

improve MCAS software so that it takes into account data from two angle-of-attack sensors;
limit the deflection angle of the stabilizer by the system;
make the system trigger once;
include a description of MCAS in pilots' manuals.

“The proposed changes are fully consistent with what the aviation safety experts have told us. They spoke to the Seattle Times before the Ethiopian disaster.

Boeing said the Boeing-737 MAX was FAA-certified and deemed safe under procedures, while comments to the newspaper were "misinterpreted." The US Department of Transportation has launched an investigation into the certification of the aircraft, writes The Wall Street Journal.

Sergei Smirnov