boltonblue

or stated simply it's awfully hard to fix something that's working.

engifineer

Which is a direct fault of the airline or the crew at that point. A faulty component may be the fault of the mfgr but knowing about it and allowing the same plane to fly the next day is totally on the airline.

engifineer

It is an intermittent failure. That does not mean repeatable by those troubleshooting. Troubleshooting an intermittent issue is the hardest thing in the world. Repeatable in that sense means I can make the issue happen every time, so I can methodically troubleshoot. That is not the case here from what I am reading. It has happened three times out of ALL flights made on this aircraft. I believe there have been close to 9000 flights on this aircraft? That means this issue has happened on much less than 1% of them. And then do that math on how many actuation's of this system in specific scenarios there have been on each flight. That is such a small number that making it happen on demand is near impossible until the root cause is found and that is hard to find without repeat ability. I have managed teams through troubleshooting issues many times and this is a very difficult scenario.

And they do not want (nor are they allowed) to just throw in a software fix. On any safety critical system in a regulated industry there is a lot of effort that has to go into unit testing, verification testing and review of any code change made before it can go into production. This is to prevent a quick change from having un-intended effects on some other part of the system and causing yet another large issue. There is simply no such thing as a quick fix in software for something like this. I have and still do deal with this in medical devices and systems. To put it in perspective, the unit testing alone on one device has taken 500+ hours so far, with probably another 100 to go. And THEN we get to spend a couple of months verifying said software before it can be released. And this is on something much less critical than a device that carries people to 40,000 ft And if we make one code change, a big chunk of all that testing has to be repeated.

Now yes, once they knew there was an issue with something, they should immediately ground the planes. That is a different issue all together.

dlq04

In the end, I suspect 99+% of crashes are due to pilot error. Be it lack of training, lack of experience, etc.

tof

Based on news reports I've seen (and which so far confirm Coz's highly educated guesses) crashes were due to failed sensors compounded by ill-trained pilots simply not shutting off the auto trim. Of course news reports of necessity tent to greatly oversimplify things. Coz made it sound like it was a bit more complicated than that.

cosmomiller

It is tempting to blame pilot error in many crashes, however, the devil is in the details. If an engine fails on takeoff and the plane crashes (planes are certified to fly with an engine failure) do you blame the pilot for the crash? Look at the American Airlines DC-10 taking off in Chicago that experienced not just an engine failure, but the entire engine mounting failed, rotating up and over the wing taking with it critical hydraulics. The first officer was flying and received a lot of coaching from the Captain but the plane stalled and went in. Without knowing the extent of the damage that occurred, the window of recovery was extremely narrow. It was beyond the skill level of the pilot to save the airplane. Do you blame the pilot? It is true that systems and engines have become extremely reliable but engineered man made systems can behave and fail in unanticipated ways. The results are dumped into a pilot's lap and if he/she is not successful, it is easy to say "pilot error" from the luxury of Monday morning.

As far as repair goes, the airplane now self reports. You can select self tests for any system from cockpit displays, MCDU for short. I can see how a single test might not reveal a fault when none is detected except any failure is also recorded. If some part reports a single failure and then later reports it is operating, it MAY be permissible from the manufacturers instruction that you may continue or may continue to operate with a failed system but have so much time (specified) to repair it or replace it. Perhaps, just perhaps, that is what happened for Lion. Maintenance is well documented and detailed. Pilots have manuals that mirror maintenance requirements and at the same time detail actions, if any, pilots are required to do in any given situation.

Automation can be a good thing. You need to monitor it and understand what it is doing and how you interact with it to achieve desired results. It is a lot like the pilot monitoring (PM) the pilot flying (PF) to ensure he/she is flying the correct path. Sometimes when things are not going the way you want, you disconnect the magic and just fly the plane. In this case (737Max) disconnecting the magic and flying the plane did not give the pilots the desired result. The plane was fighting them and they did not know why because they were not informed as they should have been. If they had the "extras" (angle of attack gauge) they would have known the correct AOA but still would not have known that the one sensor was driving the plane to react in an unknown manner.

Personally, I like to fly and keep my perishable "stick and rudder" skills honed. When I am the PF and take off, I manually fly until around 18-20K feet. On approach I click off the autopilot AND auto thrust during downwind or arrival procedure depending on weather and cockpit workload. In conditions of very low visibility (zero zero essentially) we let the plane fly itself to touchdown and rollout. That is a CAT III landing. That being said, it is still possible during manual flight to have automatic systems trigger under certain conditions. I can manually fly the plane and approach a stall. The automatic systems will kick in. I need to know how, when, and why those can occur. If a system incorrectly makes an input and in my opinion threatens safety, I need to know it is actually occurring and take actions to overcome it.

Here is video with an American Airlines 737 Max pilot discussing the plane.

https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FLVOwxV9dVmg&data=02% 7C01%7C%7Cc937eb586044480f00a408d6aca58157%7C84df9 e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636886224164 893840&sdata=YVXUegeoCODdgwnFJLg64RWPWf9AgYLuXF48H sEl3Ro%3D&reserved=0

dlq04

"In conditions of very low visibility (zero zero essentially) we let the plane fly itself to touchdown and rollout." I had no idea this could be done.

jukngene

boltonblue

It's not just that you can reproduce the very low probability error, but also were you looking at the right things to be able to see the problem.
I've chased problems that took weeks to find, only to see absolutely nothing interesting or related to the failure.
The only value in the effort being that you know what NOT causing it.

There is also the problem of adding test equipment literally suppressing the problem.
Replicate the problem, woo hoo.
put a probe on to see it and magically it goes away.
take it off and it's back. Sometimes that is the only way you can infer the failure mechanism.
Sometimes it leads you down the path of finding a very similar but entirely unrelated problem.

NEVER EVER assume there is only one problem!!!

Matt_in_VA

I could not agree more. In February of 1980 I was flying in the right seat of a Bonanza A-36 from Cincinnati, Ohio to Woodbridge, VA on a rainy night. We were at 9K feet and the cloud cover was broken. At one point the moon was shining through the clouds at about the two O'Clock position. One's eyes wanted to think that if that is "UP" I must be in a left hand banking turn. The attitude indicator told the real story. Years later when I heard on the radio about JFK Juniors demise I came to the conclusion in minutes that he flew the plane into the water. As he was NOT qualified to fly in the weather conditions that he flew into.