European regulators on Tuesday moved a step closer to letting the Boeing 737 MAX fly again, publishing a proposed airworthiness directive that should see the aircraft cleared for flights in Europe by early January after being grounded for nearly two years following two deadly crashes.
The European Union Aviation Safety Agency (EASA) directive includes some extra requirements in addition to those proposed last week by the U.S. Federal Aviation Administration (FAA) — highlighting the gap the MAX crisis has opened between the regulators.
The publication of EASA’s directive opens a 28-day public consultation period, after which the agency will review the input and then approve the aircraft for flight.
EASA said the step signals “its intention to approve the aircraft to return to Europe’s skies within a matter of weeks.”
Although there will be no software or technical differences between MAX aircraft operated by U.S. airlines and those in the 32 countries governed by EASA rules, on the jet’s return to service two procedural differences will be in place.
Furthermore, EASA formally confirmed it is working with Boeing on additional design changes that will be implemented on the MAX later.
“EASA made clear from the outset that we would conduct our own objective and independent assessment of the 737 MAX, working closely with the FAA and Boeing, to make sure that there can be no repeat of these tragic accidents, which touched the lives of so many people,” said EASA Executive Director Patrick Ky in a statement.
The main immediate procedural change mandated by EASA involves the “stick shaker,” an alert that warns the flight crew of a possible stall by making the pilot’s control column vibrate vigorously and noisily. In the two MAX crashes, this warning was set off erroneously by a false angle-of-attack sensor and added to the confusion in the cockpit throughout both flights.
EASA’s directive explicitly allows flight crews to intervene to silence the stick shaker if they realize it’s a false alarm. This will have to be done by pulling a circuit breaker in an overhead panel.
Transport Canada has also said it wants this requirement on the MAX’s return to service. Boeing will have to make clear to pilots which breaker to pull and include it in the training and flight manuals.
The FAA expressly rejected this option in the U.S. directive, arguing that the upgraded flight controls make it unnecessary and that having the pilot reach back and up to pull the circuit breaker panel created additional risk of distraction.
EASA also mandates, for the time being, that MAX crews should not use the aircraft’s autopilot for certain types of high-precision landings.
More significantly, EASA said it is working with Boeing to introduce further design changes on the MAX that will be added later “to further enhance the safety of the aircraft.”
EASA said Boeing has agreed to further bolster the redundancy of the aircraft’s angle-of-attack sensor system. This means Boeing must add a third check on the two physical sensors fitted to the exterior of the plane’s fuselage. This will likely be an indirect, “synthetic” software calculation of the angle of attack based on parameters such as the aircraft’s weight, speed, inertial position and GPS signal.
EASA has said it wants this change made by the time the largest MAX model, the 737-10, enters service, which means within a couple of years.
And EASA said Boeing has also agreed to conduct “a human factor assessment of its crew alerting systems within the next 12 months, with the aim of potentially upgrading these to a more modern design approach.”
When the FAA originally certified the MAX it granted Boeing exemptions from the latest crew alerting system safety standards. That decision was heavily criticized after the crashes, including in an internal ethics complaint by Boeing flight controls engineer Curtis Ewbank.
Regulators around the world grounded the MAX in March 2019, after the crash of an Ethiopian Airlines jet. That happened less than five months after another MAX flown by Indonesia’s Lion Air plunged into the Java Sea. A total of 346 passengers and crew members on both planes were killed.
Investigations into the accidents revealed a primary cause in both cases was a software function program known as the Maneuvering Characteristics Augmentation System or MCAS. EASA said its probe began with a review of the MCAS but went far beyond.
EASA said one “fundamental problem” of the MCAS, which was intended to make the aircraft easier to handle, was that many pilots did not even know it was there.
“I am confident that we have left no stone unturned in our assessment of the aircraft with its changed design approach,” Ky said.
“Each time when it may have appeared that problems were resolved, we dug deeper and asked even more questions. The result was a thorough and comprehensive review of how this plane flies and what it is like for a pilot to fly the MAX, giving us the assurance that it is now safe to fly.”
