After its 737 Max was grounded due to two deadly accidents, Boeing said it was confident it could correct the problem and have the plane recertified by the FAA within months. Now, the company hopes it can get the work done by the end of the year.
Engineers thought they had almost completed the redesign of the computer software in June. They asked some test pilots to take to the simulator and see the difference.
Unfortunately, any difference was subtle. A simulated computer glitch again caused the plane to make aggressive efforts to dive – just as it had in the crashes in Indonesia and Ethiopia.
Bloomberg interviewed several people who have been briefed on the work, and they said that the system appears to need more than a patch to the existing system. Instead, the two flight computers apparently need a complete overhaul. These computers run critical instruments and the autopilot.
According to Bloomberg, Boeing has been experiencing some tension in its relations with the FAA and the European Aviation Safety Agency. The two agencies have asked the company for more complete documentation of the changes it is making to the computers. This could delay recertification further.
Redesign work focuses on MCAS but involves entire computer system
As we’ve discussed before, the problem with the 737 Max appears to be with a software system called the Maneuvering Characteristics Augmentation System (MCAS). It was thought that a malfunctioning sensor caused the MCAS to repeatedly push down the nose of the plane in the two accidents. Pilots struggled to convince the MCAS that the plane did not need to lower its altitude, and they eventually lost control. A total of 346 people were killed as a result.
Boeing thought it had only to fix a glitch with the MCAS. In October of last year, Boeing announced that it would redesign the MCAS to be less aggressive and to activate only once. It was thought this would be a relatively easy change.
Now, however, Boeing is working to modernize the dual-computer system that runs the 737 Max. Whereas many modern jets have three computers, the 737 Max only has two – and they don’t communicate. Yet even adding a single wire between the two computers could introduce new errors into the system.
In order to recertify the plane, Boeing has to be able to predict any scenario where the pilots could run into trouble and run tests to prove the scenario is within normal guidelines. While there might have been only 10 scenarios to test if the MCAS were the only thing revised, making changes to the computer system could require 100 testing scenarios.
For now, the 737 Max should remain grounded.