The European Aviation Safety Agency, which is conducting its own independent review of Boeing's grounded 737 MAX, is not satisfied with a key detail in Boeing's fixation to the jet. It wants Boeing to do more to improve the integrity of the sensors that failed in the two deadly crashes in Indonesia and Ethiopia, killing 346 people.
And it is demanding that Boeing in flight tests demonstrates the stability of the MAX during extreme maneuvers, not only with Boes's recently updated flight control system, but also with that system turned off.
This was among the disclosures in a presentation Tuesday to the European Parliament by Patrick Ky, Executive Director of the European Union Aviation Safety Agency (EASA). Ky listed what appear to be stricter EASA requirements than the requirements of the United States counterpart, the Federal Aviation Administration (FAA).
Boeing has publicly stated that they are hoping for FAA approval for MAX in October so that it can return to passenger service in the United States this year.
Foreign regulators usually follow the FAA's leadership. But after the MAX crashes revealed deficiencies in the FAA certification process, it is no longer safe.
One of Ky's slides quoted a letter EASA sent to the FAA on April 1
The first condition is: "Design changes proposed by Boeing are EASA approved (no delegation to FAA)."
The second is that EASA completes a "further and broader independent review" of the aircraft, in addition to the specific design changes to the aircraft control system. who went on high altitude traffic on the crash flights.
If the FAA moves ahead and clears MAX to fly while EASA holds on later, it would create a unique non-compliance with worldwide regulation that would seriously complicate the schedules of many airlines flying internationally.
FAA approval will only apply to US airlines flying domestically. European airlines flying MAX, such as Norwegian Air, require EASA approval.
And it would put Boeing in a very difficult position if the FAA says MAX is safe to fly while others withhold approval.
Both MAX crashes were initiated by faulty sensors measuring the aircraft's Angle of Attack, the angle between the oncoming airflow and the wing. This error then enabled a new flight control system – a software known as the Augmentation System (MCAS) – which, on each of the crashes, repeatedly pressed the nose of the jet.
Although Boeing has updated MCAS to take input from both Angle of Attack sensors on the MAX instead of just one, and will not work if they disagree, Ky EASA indicated this is insufficient.
One of his slides states that while Boee's proposal has improved the Angle of Attack system, there are "still no appropriate answers to the Angle of Attack's integrity issues."
And EASA wants rigorous flow tests that prove MAX's safety with or without MCAS.
Boeing engineers designed the original MCAS to smooth the feel of the ride in the pilot's hands during certain extreme high-speed turns and stall maneuvers.
Before MAX is cleared to fly passengers again, both EASA and FAA will require flight tests of the new updated software. In addition, Ky said, EASA will require Boeing to demonstrate the stability of the jet in flight tests that include high-speed turns and stall maneuvers with MCAS turned off.
The latest requirement should go a long way to satisfying a nagging public concern about MAX. On the Internet, many Boeing critics have expressed concern that the jet "itself is unstable" with engines that are too large, and that a "band-aid" software is not good enough to fix it. The EASA requirement to fly safely without MCAS should prove otherwise.
On Wednesday, the FAA declined to clarify whether the EASA requirements are stricter or in line with its own.
"We will not comment on specific details of ongoing discussions," the FAA said in a statement. "The FAA has a transparent and collaborative relationship with other civil aviation authorities as we continue our review of software changes on the Boeing 737 MAX … Each government will make its own decision to return the aircraft to service based on a thorough safety assessment."
An FAA security official, who requested anonymity because he spoke without agency approval, said that the US regulator has been working through the MAX approval process, looking for system failures "with a fine tooth comb, which they never have before. "
" People know that maybe it was something they should have caught the first time, "he said. "They want to make sure it doesn't happen again."
Still, the official was not aware of any long-standing concern at the FAA with the Angle of Attack sensor system. He said the software and system changes Boeing has proposed have been anything but agreed in the FAA, and that only the level of pilot training that will be needed remains undetermined.
While US pilots have said they are satisfied that some computer-based training is adequate, foreign regulators may require full flight simulator training. The FAA official said that both EASA and India's aviation regulator, the Directorate-General for Civil Aviation, have so far agreed to agree to computer-based training alone.
Ky & # 39; s presentation confirms that for EASA, the amount of pilot training required before MAX flies passengers is still "a work in progress."
Ky said that EASA provided to Boeing and the FAA in July a list of significant technical problems, which include system failures that were not adequately monitored; forces needed to move the manual trim wheel too high; and a risk of crew confusion in some failure cases, particularly an Angle of Attack single failure at takeoff.
A slide showing the "latest status" in the process indicates that the pilot training and the Angle of Attack system are still in play.  In a statement Wednesday, Boeing declined to comment on discussions with regulators. "We continue to work with the FAA and global regulators to address their concerns about safely returning MAX to service," the company said in a statement.
On Tuesday, Alexandre de Juniac – head of the International Air Transport Association, the global trading group representing the world's airlines – told Reuters in Chicago that "with 737 MAX we are a little concerned … because we do not see the normal unanimity of international regulators that should be the case. "
"We see a discrepancy that is harmful to the industry," de Juniac added, urging regulators to make changes to the single certification process "collectively," according to Reuters.
Ky's parliamentary presentation on the same day, also briefly quoted by Reuters, made that discrepancy.