A union representing Federal Aviation Administration (FAA) airplane safety engineers who work on certifying new aircraft called Monday for substantial upgrades to the flight crew alerting systems and other changes on Boeing’s 737 MAX before the plane is allowed to return to the air.

The union’s comments came on the final day for public comment on the FAA’s proposed design changes, with more than 200 responses posted by late afternoon.

The FAA’s own technical experts argue that fixing the flawed flight control system that caused the two crashes is not enough and that Boeing must also address the serious confusion that played out in the cockpit in both emergencies.

In contrast, a submission Monday by the main airline pilot union in North America declares the FAA’s proposed design changes “an effective component in ensuring the safe return to service” and suggesting only relatively small tweaks to the current plan.

The British Airline Pilots’ Association (BALPA), representing more than 10,000 pilots in the U.K., weighed in more critically, suggesting that the MAX should have been certified as an all-new design in the first place,requiring it to meet all current requirements.

Exceptions granted

During the original certification of the 737 MAX, Boeing successfully argued to the FAA that the jet shouldn’t have to meet all the latest certification requirements governing how cockpit warnings tell the pilots that something is wrong.


The MAX was duly granted exceptions to five of the regulatory stipulations so that it could retain the legacy 737 instrument panel and crew alert system.

The FAA technical staff union argued Monday that those exceptions should be rescinded and the crew alerting system on the recertified MAX updated accordingly as a condition of the jet’s return to service.

In the Lion Air and Ethiopian 737 MAX accidents that killed 346 people, multiple warnings set off by a single erroneous sensor caused distraction and confusion for the pilots.

The union proposal would require major revisions to the instrument displays on the airplane as well as more pilot training on the revised systems, and would likely further delay the MAX’s return, which Boeing hopes will be by year end.

In early August, the FAA published its final list of required design changes to the Boeing 737 MAX and invited public comment. The comment period ended Monday and last-minute responses came in from various parties with substantial expertise.

The National Safety Committee of the National Air Traffic Controllers Association (NATCA) — a union that represents almost 700 aircraft-certification technical experts at the FAA, as well as air traffic controllers — recommended a series of additional changes to the MAX, including rescinding the crew-alerting exceptions.


The NATCA comments follow closely the critique of Boeing whistleblower Curtis Ewbank, a safety engineer who filed an ethics complaint internally at Boeing after the second MAX crash in Ethiopia and who then publicly repeated his concerns about the safety of the MAX in a letter to the U.S. Senate this summer.

On Friday, covering much of the same ground, Ewbank submitted his own comment on the FAA return to service plan.

Four fatal accidents cited

The changes the FAA plan mandates will fix the flight control system — the Maneuvering Characteristics Augmentation System (MCAS) — that activated erroneously in the two crashes and brought both planes down. It also moves some wiring to ensure proper separation of wires controlling the horizontal tail. And it switches the avionics architecture of the airplane so that it uses both flight control computers on a given flight instead of only one.

However, the FAA plan leaves the MAX’s instrument panel displays and the pilot warning systems largely untouched. Updating them would require a major remake of the 737’s human/machine interface that would be both expensive and lengthy.

In the original certification of the MAX, in arguing for the exemptions, Boeing estimated the cost of full compliance in terms of new training for pilots worldwide at more than $10 billion.

In its submission Monday, NATCA declared that argument not valid.

“The cost of the two accidents that resulted in worldwide grounding of the 737 MAX fleet has well exceeded the stated $10 billion flight crew training costs,” NATCA states.


NATCA draws attention to how a continuous “stick shaker” alert — a heavy, loud vibration of the pilot control column that indicates the plane is on the point of stalling — triggered by a single angle of attack sensor can prove a major distraction, yet cannot be canceled as the latest regulations require. This is a problem also highlighted by Transport Canada, which has asked Boeing for a fix.

There have been two other fatal accidents, on Birgenair and AeroPeru 757s in 1996, that are associated with multiple false and conflicting alerts, NATCA notes.

The 757 is an older Boeing plane, no longer produced, but with similar alerting to the 737. In both those accidents, the stick shaker was going off warning that the plane was slowing to a stall while at the same time an overspeed warning indicated the plane was going too fast. This was also the case on the Ethiopian Airlines MAX that crashed.

“Based on a history of four fatal accidents in the last 24 years, the alerting design should be upgraded,” NATCA states.

NATCA also reiterates another recommendation previously raised by Ewbank, which is that the warning light on a MAX instrument panel indicating that the jet’s autothrottle is disconnected is too similar to a different warning related to airspeed and has no audio backup warning. This design isn’t permitted under the latest safety regulations.

Separately, NATCA recommends revising the instructions to pilots of how to use the manual wheel in the cockpit to counter movement of the horizontal tail if it pushes the jet’s nose down uncommanded by the pilot.


NATCA says the procedure as now rewritten by Boeing is lacking because it fails to specifically tell the pilots that before they hit the cutout switches to kill electrical power to the motor moving the tail, they first need to use the thumb switches on the control column to get the tail back to a near neutral position.

Failing to do that can leave the horizontal tail so far out of position that the aerodynamic forces on it make the manual wheel too heavy to move.

Data from the Ethiopian Airlines ET302 crash suggests this is what happened on that flight, with the pilots immediately hitting the cutoff switches to stop MCAS, but then finding it impossible to move the manual wheel to get the nose back up again.

NATCA’s comments, representing the FAA’s own safety engineers, add weight to the warnings sounded by Ewbank, first internally and then publicly.

In Ewbank’s comment on the FAA plan, he outlined the need to prevent faulty readings from the MAX’s angle of attack sensor triggering multiple conflicting warnings and called for Boeing to “conduct a holistic evaluation of flight deck human factors and crew alerting, at least ensuring all alerts comply with regulations.”

“If automation is reacting to erroneous data and taking control away from the crew, if there isn’t sufficient backup data available to the crew to use, or even worse, if there isn’t aerodynamic control authority available for the crew to control the airplane, safety cannot be assured,” Ewbank wrote.


“The 737 operates in some scenarios at reduced safety margins compared to modern aircraft,” he added.

In a separate submission, the Air Line Pilots Association (ALPA), representing nearly 63,000 pilots flying for 35 airlines in the United States and Canada, supports the planned FAA airworthiness directive (AD).

“ALPA believes the proposed AD includes relevant and effective mitigations that address the issues identified with MCAS,” ALPA wrote. It adds that enhanced training and revisions to the pilot checklists will enable MAX flight crews “to quickly and adequately respond to various scenarios.”

Noting that there is “still room for improvement,” ALPA then lists a few suggested changes to pilot alerts and checklists.

Like NATCA, the union has some concern about the difficulty in moving the wheel that manually swivels the horizontal tail. ALPA suggests the checklist specify that turning it may require the effort of both pilots and asks Boeing for a redesign to ensure this scenario is extremely improbable.

And again mirroring the concern of others about the problem of the stick shaker going off erroneously, ALPA asks the FAA to include a procedure in pilot training for the flight crew to “quickly identify and pull the associated stick shaker circuit breaker after the alert is confirmed erroneous so that crews may remove the nuisance.”


This falls well short of the alerting system changes called for by NATCA.

The BALPA pilot union submission criticizes the FAA certification process in a general way, without demanding specific changes to the MAX.

It faults the FAA’s original certification of the MAX as a derivative model, instead of as an all-new design that would have required more scrutiny and additional pilot training.

“It is strongly felt that all future substantial aircraft design changes should result in certification as a new type with a commensurate level of training required for pilots,” BALPA wrote.

Agreeing with the position of European aviation regulator EASA, BALPA states that unlike the FAA plan to use two angle of attack sensors on the MAX, “it would be preferable for the system to utilize three.”

BALPA also said Boeing should never have used software — MCAS — to correct the MAX’s handling characteristics. Such deficiencies “should not be masked” by software but “instead should require aerodynamic re-design from the outset,” BALPA states.