The Federal Aviation Administration has moved to the next stage in returning the Boeing 737 Max to commercial service; technically it could be cleared by the end of September, but will more likely take a little longer.
The FAA has issued proposed new rules, including computer and other modifications, which will result in an Airworthiness Directive for the plane; there is a 45-day period from now for comment and change, but it is likely that after months of study, negotiation and testing that the new rules and modifications will be approved.
One issue not included in the proposed Airworthiness Directive, but which must be resolved, is what level of training or retraining will be required of pilots. The 737 Max was touted by Boeing as so like other 737s that no added training would be needed, but changes to the plane made it different enough that software was needed to make the Max behave like other 737s, and it was flaws in that system that caused two crashes and the plane’s grounding.
The training issues will be resolved separately by two agencies within FAA and in negotiations with international civil aviation authorities; that might or might not be complete within the 45-day slot.
Most of the system modifications ordered by FCC are centered on a computer system called MCAS, or Maneuvering Characteristics Augmentation System, whose function is to overcome the effects of the plane’s larger engines and keep the nose pointed at the right angle down. The plane has two ‘angle-of-attack’ sensors that tell the computer what angle the plane is headed on. There are two so that if one fails, the other will keep the plane safe, but the original software allowed a faulty sensor to override the good one, only to be overridden again—the basic cause of the crashes.
In the revised system, which will require about $14,000 per plane of computer upgrades, a flashing light panel will warn of AOA DISAGREE, ALTITUDE DISAGREE and other messages allowing pilots to follow the correct sensor. The other major change to the rules is unrelated to the software and the crashes; several wires running to control surfaces of the plane will have to be re-routed to comply with rules on separation from other systems.
