EASA: still no ‘appropriate response’ over B737 MAX AoA integrity issues

The head of the European Aviation Safety Agency has told legislators that there is as yet ‘still no appropriate response’ to the problems regarding the Boeing 737 MAX’s anti-stall software.

In a presentation before the European Parliament on September 3, EASA executive director Patrick Ky stressed that in order for a return to service of the aircraft which was at the centre of two fatal accidents, EASA has stipulated that  Boeing must meet four conditions:

  • EASA approves the design changes Boeing submits;
  • an ‘additional and broader design review’ is completed by the agency;
  • the investigations into the two MAX crashes are satisfactorily completed and understood;
  • all crews that fly on the MAX are adequately trained.

Ky argued that, unlike the Federal Aviation Administration (FAA) which has come under fire for delegating too much design authority to Boeing, his agency would not have delegated the safety assessment of the MAX’s Maneuvering Characteristics Augmentation System (MCAS). “This would not happen in our system because, in fact, compared to the FAA, we have a very structured way of delegating tasks to our industry,” he said.

The decision by the European regulator to ground the aircraft was taken on 12 March, two days after the second crash, as a data driven, precautionary measure.

Ky reported that his agency had undertaken an “unprecedented level of effort” on the MAX, including interviewing 20 multi-disciplinary experts, holding two to three virtual meetings with Boeing every week, and reviewing more than 500 documents.

EASA’s requirements for flight/simulator evaluations were communicated to Boeing on May 22 and covered 70 test points, covering normal operations where MCAS was activated and abnormal operations featuring Angle of Attack (AoA) failures, stabiliser runaway and inoperative MCAS. These simulator evaluations were performed in June and July.

It has since found that significant technical issues include a lack of exhaustive monitoring of the system failures resulting in stabiliser runaway; too high forces needed to move the manual trim wheel in case of a stabiliser runaway; too late disconnection of autopilot near stall speed in specific conditions; too high crew workload and risk of crew confusion in some failure AoA cases especially single failure at take-off. These findings were communicated to Boeing and FAA in July.

The lack of an “appropriate response’ to the problems regarding the Boeing 737 MAX’s anti-stall software should, said a US aerospace expert Dr Michael Dreikorn, be a big concern for airlines and investors alike, as this has been the fundamental focus of the suspect MCAS investigation. “EASA has proclaimed, they will make their own determination of safety when it comes to the 737 MAX. Which means, even if the FAA gives Boeing the green light with what has been proposed as a fix, as of today, EASA is not buying it and a global return to flight date still carries a big question mark,” he said.

EASA’s Ky said the agency’s next major milestones would feature a safety assessment of the new design changes proposed by Boeing, including operational procedures; a human factor evaluation and functional tests of the new software.

One full week of flight testing on a modified 737 MAX at a Boeing flight test centre would also examine MCAS operations in nominal behaviour, flights without MCAS including high speed turns and stall, a scenario of stabiliser runaway with uncommanded MCAS activation, manual trim wheel forces and an approach to stall with autopilot engaged. Crew training requirements, in particular using computer based training and simulator would be examined. The agency said it would also need to coordinate with its member states on actions before allowing the aircraft to return to service.

In recent weeks, regulators are said to have been working in tandem on recertification, which could take place as early as next month.

EASA Patrick Ky presentation