Uh Oh: Boeing To Issue 737 MAX Safety Bulletin

Filed Under: Misc.

A bit over a week ago a Lion Air Boeing 737 MAX crashed while operating a domestic flight within Indonesia. Tragically, 189 people died in the crash, which is heartbreaking. Flying is such a safe form of transportation, and it’s easy to take that for granted, but events like this remind you of just how fragile life is, and how quickly things can go wrong.

As usual, it takes a while for investigators to figure out the exact cause of a crash. What made this incident even more surprising is that it involves a brand new Boeing 737 MAX, which is Boeing’s latest technology. The 737 is the most popular and one of the safest commercial aircraft in the world, so it’s particularly concerning when a brand new plane crashes.

On one hand you’d think a brand new plane would be the safest plane imaginable (in the same way you’d probably expect a new car to be safe and in perfect condition). On the other hand, a new plane also doesn’t have the experience of an older plane, and there’s no doubt that aircraft manufacturers learn things over time.

In this case it’s also possible that the aircraft as such had nothing to do with the crash, since there are plenty of other factors at play, including the potential for pilot error.

While we don’t yet know for sure that this is directly correlated to the crash, Bloomberg is reporting that Boeing is about to issue a safety warning regarding the 737 MAX, which comes in response to an investigation of last week’s crash.

According to an anonymous source, erroneous readings from a flight-monitoring system on the 737 MAX can cause the plane to abruptly dive. Under certain circumstances (including when pilots are manually flying), the 737 MAX will try to push down the nose automatically if it detects a stall is possible. It uses a variety of factors to determine this, including the plane’s angle of attack.

With this bulletin, Boeing will warn pilots to follow an existing procedure that allows them to continue flying in the event that there are erroneous angle of attack readings.

This seems like it will just be an intermediate bulletin, and like I said, we’re not yet sure if this is the cause of the Lion Air 737 MAX crash. However, it seems they recognize this is an issue, and in the interim it’s important that they have a proper procedure for pilots to follow. We’ll have to wait and see if more changes are made.

With around 200 Boeing 737 MAX aircraft in the skies around the world (and counting), this has the potential to impact quite a few planes.

Personally I’d feel comfortable flying a 737 MAX (though I’d feel comfortable flying just about any plane), but this does seem like an issue.

I’ll be curious to see how this unfolds further…

Would you have any qualms flying a 737 MAX in light of this news?

  1. Remember, the plane went through about a gazillion hours of flight testing without incident. And, it’s being flown by many other airlines without incident. What I want to know is why the problem wasn’t fixed since it happened on four flights in a row.

  2. The definition of “fake news”. A blogger rushes to post a sensational headline with incomplete and minimal information. And on a technical topic which he himself isn’t remotely an expert in to begin with. It’s not intentional, but this post is precisely how …in a very small corner of the internet…fake narratives and nonsense dominate the airways these days.

  3. In this case, the reports that I have been reading from news agencies, concerns the pitot tubes, which together with static pressure ports, provide the air-speed readings. Those malfunctioning and indicating, in this case, too low an air speed nearing the stall speed would apparently lead to the aircraft taking corrective measures. Much is unclear as to does this occur during all flight modes, auto-pilot mode, auto-throttle mode, etc. The aircraft responding without confirmation from the pilot is always dangerous. AF447 perished due to a similar incident with malfunctioning pitot ports due to ice-crystal formation on stagnation nozzles.

  4. Tend to agree with @Bob Trial that this post is a bit misleading. Boeing is literally just reminding everyone of previously published instructions on how to handle erroneous airspeed indications. It’s quite possible the pilots on Lion Air did not follow those instructions — to say nothing of the fact that airspeed indicators are critical safety equipment, so as soon as they malfunctioned, the plane should have been grounded so they could be fixed, not cleared to fly on four more flights despite the malfunction.

    Boeing isn’t responsible for operator stupidity and recklessness, but they’re right to remind everyone after the crash of the correct procedure for handling faulty airspeed readings.

  5. @Kent AF447 Went down because the pilot in the right seat was a moron. Yes the pitot tubes became blocked and they lost airspeed information. But guess what there is a checklist procedure for that. But what did this pilot who not long before had been discussing the fact that the airplane was at the top of its flight envelope do? He grabbed his side stick and pulled it full back and held it there. Now one thing that every Airbus pilot gets constantly hammered into his head is that yes you CAN stall the airplane in alternate law and guess what he was in alternate law. An airplane fault started the chain of events leading to the accident. But the accident was caused by a pilot who clearly had no business in a commercial airliner plain and simple.

    @Lucky I agree with others that you’ve jumped the gun on this one on the basis of quite fragmentary information. I would note that Airbus on the 320 series had to issue an Emergency AD a while back because of a problem with the ADRs that could cause the aircraft to pitch down uncontrollably. It was (and is) certainly a serious concern but no accidents resulted from it because crews that ran into this problem did what they were supposed to do and worked the problem without losing aircraft control. Unless and until Boeing issues the AD we don’t know if this is a serious issue or not.

  6. @121Pilot – in complete agreement with you. Not speculating as to the final reason for the crash, just giving information on a similar event. Regardless, I stand corrected by @DC since the latest news point to the AoA. Clearly I have been following the US elections more closely in the last 24 hours.

  7. A new car is safer than an old car? A new plane is safer than an old plane? Lucky, I love you and the blog but WTF are you talking about? Mechanical issues and defects can affect any complex piece of machinery at any time. I’m no expert but from the battery issues with the 787 and no this, why does it feel like Boeing keeps launching new products with fairly serious issues?

  8. Reuters has a very detailed article about this.

    That said, not all airlines report the technical issues/incidents they’re having with their planes and so we don’t really know how many B737Max have had the same or similiar issues. How many incidents did it take for the Dreamliner to be grounded?!

    Given how that plane apparently nose-dived it’s abit hard not fault a technical failure here. Given Indonesian airlines’ poor safety records, it’s easier for most people to just blame the pilots for this crash.

    And again, while hasn’t the rest of the plane been found yet if the waters are just 35-40m deep at the site of the crash?

  9. @Neil S.

    The Boeing 787 is a game-changer with its focus on electronics over hydraulics (hallelujah). I am not surprised that teething issues were encountered on such a shift in the fundamentals of aviation technology. There are several issues with all new aircraft (the A350 included), but aren’t highlighted as much since these aircraft are based on more “common” technology. There is always resistance to the “new.”

    Example – this went unnoticed: https://www.reuters.com/article/us-airbus-a350-safety-idUSKCN1B40OX

  10. You said your comfortable flying a 737 MAX. That contradicts what you said in your review of AA’s MAX 😉

  11. Many are asking why the plane was not fixed after this happened earlier. 2 reasons – it was a new plane still under warranty and hence Boeing made the decision on fixes and second Boeing knew the plane had a problem and had devised a standard procedure to follow when the plane misbehaved so as per them no fix was needed. Now Boeing is sending out a bulletin saying basically “Please read the fine print. The fine print says the 737 Max can make suicidal dives and there is a procedure to get the computer out of suicide mode. So not our problem”
    Fix the fucking problem Boeing instead of covering your ass with fine print.

  12. Lucky you say a new plane is safer than an old plane. Thats wrong. In Engineering we are very clearly taught that manufacturing defects either show up in the first 10% of life or after 80% of life. A middle Aged plane is the safest plane. The 737-Max is still new and not all kinks have been figured out. There is a reason early adopter airlines are given big discounts. They are basically beta testers. I wouldn’t fly on a 737-Max till this issue is figured out. There are only 200 of these planes flying so not that it will cramp my travel in a big way.
    And a design where in manual mode the computer overrides the captain and does a suicide dive is just stupid coding.

  13. @Prabuddha the issue is you can’t fix that. Basically the only way to fix it would be to shut off the automatic recovery system which would lead to an increase in stall related crashes (pilot error). Instruments can fail on aircraft regardless or age. The pilots are trained on how to deal with that. Boeing is reminded pilots of how to deal with it.

  14. What blows my mind is that pilots and planes are rushed through to service. The occasional mishap is just the cost to be paid in the overall progress of aviation. Why then are we spending hundreds of billions against terrorism. The occasional loss should be treated as cost of business as well.

    The western industrial, security, political complex is strong.

  15. Even with false altitude or speed readings, the aircraft was at 3,000 feet with X load factor.

    Assuming erratic auto pilot or false readings, 3,000 feet is 2 minutes off the ground. It doesn’t take a genius to realise that this is perhaps one of the MOST dangerous parts of flight.

    3/4 throttle, pitch up 15 degrees, and get through the cloud.

    Once you’ve aviated, and navigated, ask ATC for a radar FL.

    Call me a cynic but this demonstrates perhaps the issue of training pilots on a simulator from day 1.

    Give me an ex fighter any day.

  16. Any ATP’s out there have thoughts about flight controls that, according to this post, are able to ‘lock out’ the pilot’s inputs? I hadn’t known that was a ‘thing’ and I find it way scarier than instruments malfunctioning. As a passenger, I think there’s a lot of good reasons to want a real live human being, with lots of training, in control of the aircraft.

  17. “Personally I’d feel comfortable flying a 737 MAX“ – unless it’s an AA 737MAX, they’ve gone to great lengths to ensure no one is comfortable on that plane.

  18. @Liam I’m not current on any Boeing products but my knowledge of them and Boeings in general is that the pilot always has the final word on what the airplane does. Various systems are there to assist when a problem is detected but they can be overridden. The Airbus FBW system in normal law does prevent the pilot from doing certain things like stalling the airplane or going beyond certain pitch and bank limits for example. In Alternate law (Which you get to when things aren’t working properly) certain protections remain but you CAN stall the airplane. Once you get to direct law (the last step down the ladder) it full manual control of the aircraft. There are ways to get to direct law via pilot action so if needed the pilot retains the ability even in the Airbus to be the last and final word on aircraft control.

  19. To answer your question, I won’t fly one until they get to the bottom of this. This safety bulletin or whatever it is, seems woefully inadequate if the suggestion is to get out the checklist procedures while the aircraft is in a forced dive at 5000 feet in order to manually disable the automatic system. Is there enough time at this altitude to perform these corrective actions?

    Regardless of what the investigation finds, whether it be equipment, design or crew failure or a combination of all three, I just hope they work fast and don’t take the usual two years of investigating, risking the lives of countless passengers in the interim or worse another disaster.

  20. @BobTrial and all those who think this is much ado about nothing seem not to understand that the Indonesian National Transportation Safety Committee has determined from the Black Box that Lion Air flight 610 actually experienced this sort of erroneous Angle of Attack (AOA) data while auto-pilot was disengaged as a result of the false airspeed readings. As such, its quite a big deal, not at all jumping the gun to note with concern the language of the directive from Boeing:

    Boeing would like to call attention to an AOA failure condition that can occur during manual flight only.

    This Bulletin provides specific instructions to flight crews dealing with erroneous AOA data as experienced in the Lion Air flight, which causes the pitch trim system to create uncommanded nose down stabilizer movements lasting up to 10 seconds, and how to stop it by disconnecting the stabilizer trim system.

    Not a big deal? I think that’s an ridiculous and uninformed point of view. Uncommanded nose down is a very big deal, especially at 5,000 feet while trying to turn back to the runway. This seems to be part of the cascade of errors which lead to the loss of the flight.

  21. I will simply avoid Max before it goes more stable. Announcement from FAA has indicated something already.

  22. The over reliance on automation is leading to pilots who are not able to handle things when automation fails. its not just a question of taking manual control. In this case you have to fight the planes computer by using another computer the electric trim before you can unplug both and take manual control. Given that this will probably happen only once in a pilots flying career and these planes are being used as puddle jumpers for 1 hr flights I think this level of automation and the required simulator training to deal with automation failures is overkill. Lion would be better served by flying planes with lesser automation.

    Any aircraft manufacturer which can come up with a modern transport plane which is not hyper automated and hyper optimized and can be flown with simple inputs instead of needing to play with a computer has a ready market with LCCs who are just flying within a 2-3 hr range and dont really need autopilot.

  23. It’s unbelievable , one of the very first jets to buy the farm with pitot tubes was a TWA 727
    around the Boston area with very few people on board !

    Almost 50 years later we are still back at square one with the very same issue !
    Pilots are not adequately trained to in this area !

  24. @Prabuddha that is crazy talk. Automation is one of the biggest factors in avaition safety. Why do you think there has been such an increase in air safety? I get what you are saying but the number of accidents is insignificant to the number in the 60s or 70s.

  25. Pilots and automation don’t mix well. How many oops or almost accidents have happened by pilots with thousands of hours? Maybe they need more sim time with as many oh shit moments as possible, so it would be second nature?

  26. Err John, what basis do you have to make that claim?

    It’s quite possible the pilots on Lion Air DID follow those instructions. Unless you have some basis to make a claim, the starting point is that rules are followed, not just assuming a person must be in the wrong.

  27. I always treat all new aircraft launches with skepticism. Hence, I waited for a year before flying on the A350 – especially after hearing of multitude of initial problems with the aircraft. Regimented testing just does not expose an aircraft to the type of handling and environments it will experience in its practical life.

  28. Can someone explain to me why anyone in their right mind would design a system whereby information from one sensor (in this case, the AoA sensor) corrupts the information coming from other independent systems (airspeed, altitude, and indeed even seemingly groundspeed)?

    The equivalent in a car would be to allow the external temperature sensor to mess with the speedometer reading and the fuel gauge reading. Oh, and also allowing it to floor the throttle!!!

    If airspeed and altitude readings remain unaffected, the pilot is surely going to have a much better view of what the plane is doing and what has gone wrong.

    The pilots had no chance here given the changes in design in the 737Max, and the fact the automation adjusting the trim whilst the cockpit was giving spurious stick shaker and aural warnings that distracted from the real issue.

  29. i have a flight booked on a united 737-MAX-9 in a few weeks. Do people think this is safe? Is there any way to get out of this flight and get my money back from united for this reason?

  30. I finally had a chance to read both Boeing’s Operations Manual Bulletin and the FAA Emergency Airworthiness Directive. Here is my takeaway:

    -Boeing’s bulletin is full of lawyer speak – they are busy trying to deflect blame and avoid admission of fault
    -they used words such as “existing procedures to address this condition” to make it sound like the flight crew was at fault because they did not follow “existing procedures”
    -runaway trim and trim cut-out is an “existing procedure” that I’m sure all flight crews have practiced in the simulator. However, “this condition,” referring to erroneous AOA data, is very different from “runaway trim.”

    Since Boeing is trying to be vague and deflect blame, I will offer my take:
    -What Boeing doesn’t say is “we changed the design in the Max so that condition A would trigger condition B. It didn’t do that in the NG, only in the Max. Use “existing procedures” to fix condition B.
    -Oh and we hadn’t thought of the fact that our design change in the Max would lead to condition A triggering condition B. Oops.

    FAA is more blunt and to the point:

    AD Requirements
    This AD requires revising certificate limitations and operating procedures of the airplane
    flight manual (AFM) …

    The FAA document then shows the new pages to be added to the airplane flight manual, including one section on certification limitations, and another section on operating procedures

    I’m sure Boeing’s design change was well-intended. However they hadn’t thought of this particular unintended consequence.

    Now that the additional manual sections are published, I’m sure all Max crews have read and discussed it, so hopefully this won’t ever happen again. I would not be surprised if the design is revised in the future, or reverted to NG’s design (i.e. the airplane won’t repeatedly try to dive into the ground with bad AOA data)

  31. This must serve as a reminder to all that this B737 MAX 8 aircraft (and most other passenger aircraft using fly-by-wire) is controlled by computer, using both sensor and human input at various times. The fundamental design problem in the B737 case appears to be the possibility that the flight computer can override human input when flying in manual mode. This is serious stuff. This essentially is saying that if any or all non-human inputs (sensors) or a coms interruption occurs such that the flight computers set a severe dive in process, it’s not possible for the pilot to override (unless he constantly holds pressure on the yoke disengage button, or carries out a difficult 2-button procedure to disengage auto control of the elevator…all in a possible weightless or negative G state, with stick-shaker and stall warning going)….this is fundamentally unsafe. At all times, the pilot of an aircraft must have the final say in its control, not the flight computer. It must be remembered that pilots have an innate 6th sense about many characteristics of the aircraft, just as you may have a rough idea of the speed you car’s going when the speedo isn’t working. Most B737 pilots would be able to safely fly and land their aircraft in manual mode when the instruments aren’t working. The computer should NEVER override this fact.

  32. I have a flight on u/a
    737 MAX -9
    Haven’t heard about the 9’s?
    It was the series 8 that crashed – Lion Air
    My flight is set for 1/20/19
    Ca- Guatemala.
    Im scared of taking that overnight trip now – and I’ve never been scared before
    Should I take it ?
    I think I should wait till more info comes out?
    What do you guys think ???

  33. March 16th 2019
    This is possibly a classic case of MARKETING execs beating down ENGINEERING execs for extra profit. They appear to have possibly skirted rules for launching new planes by hiding major 737 design changes which apparently included moving now heavier engines forward with respect to centre of gravity which caused flight problems which they perhaps attempted to remedy with angle of attack sensors and software. The need for additional pilot training appears to have been an after thought or possibly more sinister if they were downplaying design changes to skirt the regulations. This is what happens when you get a big BULLY Marketing exec who beats down safety conscious engineering people and the CEO turns a blind eye. This happens fairly often in the pharmaceutical industry when they boost sales with off label tales to physicians.

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