Airline industry rushes to understand nuances in 737 Max systems

13 November, 2018 SOURCE: Flight Dashboard BY: Jon Hemmerdinger Boston

Airlines, unions and regulators are working to understand the 737 Max's flight systems while unions uncover seeming errors in emergency "runaway stabiliser" checklists.

The work comes amid reports that the US industry was unaware Boeing had equipped the 737 Max with a new system that has been linked to the 29 October crash of a Lion Air 737 Max 8.

"We are working at an extraordinarily positive pace to share information," says a spokesperson for the Allied Pilots Association (APA), which represents pilots at American Airlines, a 737 Max operator.

"We are looking at differences between the Max and the non-Max aircraft" in an effort to understand nuances in stall prevention and notification systems, the union adds.

The issue apparently rests with the 737 Max's Manoeuvring Characteristics Augmentation System (MCAS), which is not on earlier-generation 737s. The technology automatically trims the aircraft's stabiliser, dropping the nose, to avoid stalls, according to American Airlines memo to pilots.

However, the system can also cause aircraft to dive if computers receive incorrect angle-of-attack data – a scenario called a "runaway stabiliser". Investigators have suggested faulty angle-of-attack information played a role in the Lion Air crash.

The APA says inclusion of the MCAS systems seems to have been accompanied by slight changes in how pilots should respond to runaway stabilisers.

Pilots have long been taught that pulling back on a 737's control column can arrest that condition – a fix pilots call a "breakaway", says the APA.

Indeed, American's runaway stabiliser checklist, dated 10 July, says, "stabiliser trim commands are interrupted when the control column is displaced in the opposite direction".

But the APA has now learned that the 737 Max is apparently different.

The APA cites a 7 November memo from American to pilots, in which the airline says that pulling the control column on a 737 Max will not arrest stabiliser movement if the dive was caused by faulty angle-of-attack data. "Control column force will not stop electric trimming", the memo says.

"On the 737NG, they had this breakaway system," says the APA. "On the Max, the company note says [that] pulling up on the stick doesn't work."

The union stresses that American's checklists also tell pilots to switch off the stabiliser system, which should fix the problem.

It adds that differences between 737 Max and 737NGs are not a problem – so long as pilots know about the changes.

The APA was not the only organisation caught unaware.

Also in the dark were American, Southwest Airlines, and, reportedly, Southwest's pilot association.

"We value our partnership with Boeing, but were unaware of some of the functionality of the Manoeuvring Characteristics Augmentation System (MCAS) installed on the Max 8," American tells FlightGlobal. "The work with the FAA and Boeing is ongoing, and we will continue to keep pilots informed of any updates."

"The MCAS was not mentioned in the manuals that Boeing provided to Southwest," Southwest says in a statement. "Therefore, MCAS is not mentioned in the Southwest Max 8 manuals."

The Dallas-based carrier's pilot union did not respond to requests for comment.

Boeing declines to comment about the MCAS, saying it is working to understand circumstances related to the Lion Air crash, which killed 189 people.

"We are taking every measure to fully understand all aspects of this incident, working closely with the investigating team and all regulatory authorities involved," it says. "We are confident in the safety of the 737 Max."

Following the crash, Boeing issued a service alert and the Federal Aviation Administration issued an emergency airworthiness directive requiring airlines to revise flight manuals to specify how pilots should response to runaway stabilisers.

American and Southwest have complied with the order, they say.

The -200 did. The knob was to hold the trash bag.

That's what the 727 had. But it appears at some point Boeing replaced the mechanical trim brake with an electric system that also let opposite pitch input stop stab trimming, as in the Allied Pilots post above. So maybe Boeing took out that system in the Max. That would be a significant change. I remember the preflite first check of the day in the 727, trim one way and push the control column the other and see if the brake engaged. I guess that check is not done on current 737s.

Gleaned off Pprune:

https://leehamnews.com/2018/11/14/bo...to-the-pilots/

Interesting. I wonder if they received any kind of EICAS (or whatever is in that a/c) caution/warning about anything flight control related during the event.

“In an interview Thursday, Capt. Todd Insler, chairman of the United branch of ALPA, the Air Line Pilots Association union, broke ranks with his counterparts at American Airlines and Southwest Airlines who earlier this week publicly complained that this wasn't disclosed to pilots during training or included in the 737 MAX pilot manuals.

Insler said many systems on an airplane work in the background without the pilot's knowledge. He compared it to watching television: "I don't need to know how it works."

“The story here is not why we didn't know about (the new system), it's why the pilots didn't fly the plane," said Insler.

That view drew a sharp rejoinder Friday from Capt. Dennis Tajer, chairman of the communications committee of the Allied Pilots Association (APA), representing American Airlines pilots.

Insler said one of his pilots flew test flights on the MAX and that all of United's pilots are very capable of hand flying the plane if automated systems fail.

"If the plane doesn't do what I want it to do, I make it do so. If it's not responding, I make it respond," Insler said vehemently. "There is plenty of feedback as to how this airplane flies, more than enough inputs and opportunity to recover."

He dismissed as "speculation" the heavy discussion in the media -- largely based on a safety-warning bulletin sent out to all airlines by Boeing and a follow-on airworthiness directive by the FAA -- as to whether the MCAS system is implicated in the Lion Air accident. He said people should wait for the investigation to come up with a definitive account of what caused the crash.
Insler's suggestion that Boeing didn't necessarily have to provide pilots information specifically about MCAS supports the manufacturer's stated argument, as cited to Southwest pilots last weekend.”

I beg to differ... I need to know about any potential control surface actuation, when hand-flying or not.

The good captain above seems to forget the accident aircraft on previous flights had a split between the pilot and copilot sides on indicated air speed and the altimeter readings. I guess he could overcome those discrepancies also on a tight approach to minimums on a short runway?

It may be that perfectly good AOA, IAS, and ALT readings are going into the Central Air Data Computer (or whatever Boeing calls it) and corrupted data are coming out.

I would be very happy if Insler was flying my plane, he has taken responsibility in his life. But how many pilots today are just xbox players ? Isn't that the goal of the manufacturers to cheaper pilot costs and training and so on. They are not really encouraged to know what is going on, it's all a game. In this case a pilot might have said : "well if I wish to completely disable computation then I must also disabled STS". Which would have also disabled the new undocumented system .... working on first principles. But pilots just follow the training with no independent thoughts. Independent thought is expensive to train.

Anyway I think it is somewhat beyond this society to change course on its automation cheapening staff fanaticism, and so we need to be practical. Giving pilots access to all the AoA indicators onthe aircraft, their raw data (there are 4 I believe on the 737, 2 are on the wings) ... that would be good. And then having the concept of disabling all the computational inputs and knowing how to do that in 3 seconds flat ... which I am sure will arrive giving this accident. Also having a 3rd AoA tube outside would be good; if you have 2 and 1 fails ... that's not so much helpful when on instruments !
These 2 measures are cheap and idiot proof solutions.

btw are there any other control systems on 737 that need disabling ? Anything else ? Because pilots seem to only disabled the autopilot and navigation in the first instance.

Careful folks, possible lawyer on a fishing expedition.