Stick Shaker Disagreement Threatens MAX Consensus


An apparent rift between the FAA and aviation agencies in other countries involved in the recertification of the Boeing 737 MAX appears to center on cockpit distractions during an emergency. As we reported last week, Canada is preparing to break ranks with the FAA on the final form of the recertification with its own flight test program and a supplement to the FAA-approved flight manual. Now Bloomberg is reporting the disagreement revolves around whether the pilots should be able to shut off a malfunctioning stick shaker. Transport Canada says it’s important that pilots be able to eliminate irrelevant distractions in an emergency but the FAA claims allowing pilots to shut off safety systems (a single breaker switch stops the shaking and thumping) would set a dangerous precedent. It also worries the physical act of reaching for the breaker panel could, in itself, be a potentially dangerous distraction.

In both the Lion Air and Ethiopian Airlines crashes the stick shaker on the captain’s side remained activated by a faulty angle of attack sensor even as both pilots pulled with all their strength to try to arrest the uncommanded dive. Canada’s Transport Minister Marc Garneau, a retired astronaut, attended meetings in Washington last week on the MAX. He didn’t address the stick shaker specifically but told reporters that pilots need to be able to clear extraneous factors so they can focus on the problem. “Crew workload in a very demanding environment physically is a factor that is essential to take into consideration because you have only so much time to respond,” he said.

Neither the FAA nor Boeing would comment on the apparent schism but the Canadians made it clear they will go their own way on the issue. “We won’t hesitate to take any additional steps necessary to ensure all of our concerns have been addressed before approving a possible return to service of this aircraft,” said Garneau’s Communications Director Amy Butcher. Canada also said it will be discussing its concerns with aviation officials in other countries. 

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.

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  1. So, what’s next – software that disables the stick shakers after crossing the 49th parallel northbound?
    This is moving from the ridiculous to the sublime, at supersonic speed.

    • Self fulfilling insanity. Coved-19, do you see a common thread. It’s finally coming to a head. It’s all around us. It’s not hard to see. It’s been 50 years in the making.

  2. Snide comments accomplish nothing folks.
    While Minister Garneau has a point about multiple warnings being confusing, especially things like stick shakers, how is a pilot supposed to be able to stop the events, sort through each displayed warning, decide which are real and which are false, then disable the irrelevant one(s), if any?
    Part of the issue begins with initial training in simulators and continues unabated through years of continuation training. That part is the insistence that only a single emergency occur at a time in training. Sorry, over my career, when things start to go pear shaped for real, not just the odd happening, they tend to arrive in bunches, hopefully small bunches, but bunches none-the-less. It would be helpful to the pilot crowd to start them off handling things one at a time but then build them up slowly as experience increases to having multiple things go “wrong” over reducing periods of time.
    If you “shut down” an engine, say, who can guarantee that all the appropriate relays will act correctly to have the remaining generator(s) take the load? Or, even have a single buss relay fail to switch leaving several “failed” indications? What is to prevent the remaining engine(s) from going stupid, acting up, or otherwise misbehaving? Or completely unrelated instruments or systems deciding now would be a time to dog pile on the pilot.
    An old “saw” about troubles is that they come in threes. Not saying simulator instructor generated problems should also but that is a good starting place. Look at accident or incident reports for your aircraft’s history, we they all single occurrence items? If so, great! Soldier on! But, if multiple things did occur, they could again. Train for what happened at least but nothing prevents experienced instructor from being a little inventive and challenging the crews. Note, though, that such training should be just that, training, not necessarily a graded event. That is not to say that a bad enough display on the part of the crew shouldn’t result in more training. After all, you are sending these folks out with a multi-million dollar piece of equipment and a compartment full of people that cannot drive the jet and are relying on the crew to arrive at a destination safely.

    • “Snide comments accomplish nothing folks.”
      Au contraire. The intended effect is to confront the certitude of stupidity. A useful – and sadly, necessary – exercise.

      Apparently, it’s necessary to remind our Canadian friends that pilots ALREADY have the ability to disable the stick-pushers (in-story content).

      • And few in these comments are as certain as you, YARS. Does that tell you anything?

        The way I read the article is that Transport Canada wants pilots to be ALLOWED to reach back and pull that breaker to disable a malfunctioning stick shaker and reduce extraneous distractions. The FAA believes that disabling the stick shaker or even the act of reaching back to the breaker panel to do so is dangerous, and thus should be PROHIBITED. It’s a philisophical disagreement. Both sides have merit.

  3. >>>
    In both the Lion Air and Ethiopian Airlines crashes the stick shaker on the captain’s side remained activated by a faulty angle of attack sensor even as both pilots pulled with all their strength to try to arrest the uncommanded dive. <<<

    Is this correct? Earlier reports were an uncommanded nose-down trim was the culprit, triggered by a faulty, single AOA sensor. And, by the way, who the hell tries to pull back to overcome a stick shaker?

    • The stick shaker was an erroneous indication caused by a faulty AoA sensor.

      They weren’t trying to pull back to overcome a stick shaker. That’s the whole point of what Minister Garneau is talking about. They were trying to pull back to counter the highspeed dive they were in, caused by the MCAS, all while the stick shaker was active, adding to the confusion in the cockpit and making it harder to recover from the dive. The stick shaker was just another “thing” going off and causing distraction in the cockpit, contributing nothing to solving the issues in these accidents.

    • Well, if my cockpit windows are filled with nothing but the ground rushing towards me, then heck yes I’ll pull back to overcome a stick shaker!

  4. Depending on the system, there are usually multiple reasons a stick shaker could erroneously activate. Not allowing deactivation of the stick shaker on a completely controllable aircraft would be a real nuisance, if not a downright safety issue. If pulling a breaker is the QRH solution in this case, I wonder how the system logic accounts for the other malfunctions? My guess is it doesn’t, so removing the ability to deactivate the stick shaker through a breaker seems like a bad idea.

  5. On some aircraft, holding the autopilot disconnect button also inhibits the stick shaker (and any automated trim commands). I was surprised to learn that this is not the case on the 737.

  6. Alex has valid points about this being a philosophical issue and that both philosophies have merit. The QRH on the airplane I currently fly has an item with the title “Stall Barrier Malfunction” which goes on to read “In the event of unwanted stall barrier actuation:” Then follows a simple five step procedure, the first two steps of which disable the entire barrier system while the remaining three steps isolate the faulty side, leave it disabled and restore the properly functioning side. There is no guidance about when to resume the final three steps in which case it may be less distracting to resume those steps after solving a different simultaneously occurring malfunction. The point here is that this particular manufacturer leaves it up to the flight crew, the FAA apparently not standing in its way. I am one who has found disabling an erroneous stall barrier system useful during the simultaneous occurrence of two malfunctions. From experience I also know that such a procedure can be distracting. It’s a beautiful thing when those up front are provided with a simple procedure and are allowed to be the judges as to which is more distracting, a stick shaker firing when it shouldn’t, or the procedure to isolate and disable it.

  7. The “philosophical” difference of opinion over the relatively minor — albeit distracting — issue of a stick shaker activating is symptomatic of larger issues. On the ultimate scale of things, it’s really a minor issue. The fact that Boeing and the FAA “wouldn’t comment” shows their cozy relationship which allowed the MCAS fiasco in the first place. We now know all the underlying issues there … ad nauseum. Large complex “electric” airplanes demand that automation simplify the workload. At what point, however, has automation gone too far? As David C points out, at what point is our dependence upon and the potential failure of automation — itself — a failure mode waiting to happen to overload the crews? Anything that distracts them just makes it worse. The FAA complains that pilots aren’t getting enough stick time to be able to hand fly their airplanes when necessary yet automation has made crews subservient slaves of same. Seems like Catch-22 to me.

    We may well have gone too far with complexity of systems that you can’t scratch, sniff or see … other than recognizing that something ain’t right when it goes bad. I was talking with Julie Clark at an event last year where she said of her time flying Airbus’ that the two most commonly heard crew comments (in those highly automated airplanes) were, “why is it doing that?” And, “what’s it gonna do next?” At some point, there has to be a way to turn all that stuff off and be able to just hand fly the airplane load shedding as much of the automation as possible. Where it isn’t possible, then super redundancy needs to ensure that the likely hood of failure is nigh on impossible. The starting point of training as well as the ultimate fall back position before things get out of hand has to be the ability to make the machine do what you want it to do. I think that the Canadians are trying to say just that indirectly? Maybe they’re the “canary in the coal mine?”

    When electrons and computers are doing 100% of the work in an airplane — vs simple mechanical systems augmented by same and able to be disconnected — we better make sure we get it right to begin with. With MCAS, Boeing didn’t no matter what their lawyers say. And THAT is why there isn’t a “consensus.” THAT’s the underlying story here … the Canadians aren’t trusting either Boeing or the FAA to get it right to their satisfaction.

  8. There’s a world of difference between complying with regulations, and building a good airplane.

    Add to this, the phenomenon that, if you ask 10 pilots (or 10 regulatory agencies, or even 10 offices of the same agency), you’ll get at least 11 different opinions about what constitutes a good airplane.

    You quickly will see the difference between between addressing the issues of Boeing’s MCAS, and re-designing a 1960s airplane, to conform with a 2020s “consensus” of what constitutes a good airplane. In engineering parlance, this is classic “scope creep.” Anyone who ever has fallen victim to – or has participated in – this practice, knows that it is endless. And oftentimes fruitless.

    The idea of building an airplane in which two independent AOA sensors EACH drive one of two independent stick-shakers is absurd on its face. And yet, the FAA approved that design, long before MCAS (also approved) ever became the fruit of a three-martini design review.

    What is the SCOPE of this certification review? Are we ensuring compliance with existing rules? Or changing the rules, in an effort to build a better airplane?

    If the latter is the case, then we COULD simply modify the EXISTING linearity-of-stick-forces requirement, to permit all-circumstances hand-flying of the aircraft. No MCAS; no MCAS issues. Right? Is that what we really want (wish that we had)? Because, since Boeing AND the FAA clearly are okay with pilots DISABLING the MCAS system, that hand-flying option ALREADY is just a switch-flip away, isn’t it? Just as the turn-off-the-stick-shakers option ALREADY is just a breaker-pull away.

    In the end, we’re talking about PILOTS’ abilities – not the vehicle’s abilities. Maybe we should concentrate on pilot training and skills, rather than attempting to mitigate the lack thereof, via layers of poorly-conceived “helpful” semi-automation. But that would be scope creep. Right?

    Do we want to build better airplanes? Or better pilots? Do we even have to choose?

    In the cases of the two MCAS crashes, it’s painfully clear that having better pilots would have overcome crappy automation. And yet the modern “consensus” is that better automation should overcome crappy pilots.

    No MCAS; no MCAS problems. No pilots; no pilot problems. Can/will we come up with an acceptable solution – between those two extremes? What’s the scope, here?