Boeing employees surround the 10,000th 737 jet — a 737 MAX 8 built for Southwest Airlines — during a ceremony in Renton, Wash., in March 2018. (Boeing Photo)
Two optional safety features that might help pilots head off a scenario that’s at the heart of investigations into two catastrophic crashes of Boeing 737 MAX jets will be available free of charge on new airplanes, The New York Times reported.
The features are an indicator that shows pilots the readings from two sensors that monitor an aerodynamic characteristic known as the angle of attack, and a “disagree light” that flashes when those sensor readings are at odds with each other.
Spurious data from the angle-of-attack sensors are thought to have played a role in last October’s crash of a Lion Air 737 MAX 8 plane in Indonesia, which killed 189 people on board; and this month’s crash of an Ethiopian Airlines 737-8 in Ethiopia, which killed 157.
The current leading theory is that in both cases, bad data from a single sensor caused an automatic flight control system — known as the Maneuvering Characteristics Augmentation System, or MCAS — to kick in repeatedly.
MCAS was added to the 737 MAX’s control system to compensate for the aerodynamic effect of the model’s bigger engines and guard against an excessive upward lift and stall. But investigators suspect that, in the fatal crashes, the system forced the plane into a nose dive.
In both cases, pilots complained about control problems minutes into their doomed flights. Today The Wall Street Journal quoted Ethiopian Airlines CEO Tewolde Gebremariam as saying he believed the MCAS system was activated on the Ethiopian jetliner, based on what he has learned about the investigation.
Boeing says pilots can use a procedure to disengage the MCAS system in the event of a problem, but the procedure apparently did not come into play in the Lion Air or Ethiopian Airlines scenarios.
Over the weekend, Boeing brought pilots and trainers to its 737 MAX facility in Renton, Wash., to discuss potential safety modifications to the plane and test out simulations of an MCAS problem scenario. The New York Times quoted sources as saying that pilots using the simulators were able to land their virtual planes safely.
About 200 pilots, technical leaders and regulators are due to attend another session on Wednesday.
“This is part of our ongoing effort to share more details about our plan for supporting the safe return of the 737 MAX to commercial service,” Boeing said in a statement. “We had a productive session this past Saturday and plan to reach all current and many future MAX operators and their home regulators.”
Boeing is preparing to release a software update and revised training guidelines aimed at addressing the MCAS issue. Reportedly, one of the changes will involve having the MCAS system take in data from both angle-of-attack sensors instead of just one. Another change would reportedly limit the system’s ability to kick in repeatedly. The Journal said the changes have won tentative approval from the Federal Aviation Administration.
The debate over the 737 MAX safety features has touched on the plane’s hardware: Last week, The New York Times reported that the angle-of-attack indicator and the disagree light were optional features that operators had to pay extra for. But on Sunday, the Times said the disagree light would become standard on all new 737 MAX planes, and the indicator would be provided free of charge for customers who want it.