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Aerospace engineer here. From TFA: >A component of the main electric trim system became inoperative. Our pilots ran the appropriate checklist, which included
by na85 6y ago
Aerospace engineer here.
From TFA:
>A component of the main electric trim system became inoperative. Our pilots ran the appropriate checklist, which included manually trimming the aircraft. They returned to MIA and landed uneventfully. The issue was not related to MCAS.
That statement is from the airline, not from Boeing, so I'm more inclined to trust it. Additionally, if the airline lies and it turns up on an airworthiness audit (air maintenance organizations are subject to regular audits) then the penalties are quite severe.
In any case, per the airline's statement it was an issue unrelated to MCAS. Aircraft break literally every day in a myriad of ways that are often invisible/imperceptible to people riding on that very aircraft. In this particular case it was some unspecified component of the electric trim system.
You can look up the Master Minimum Equipment List for the B737[0] and see for yourself just how granular the approved maintenance program gets for aircraft like this. Everything on the MMEL is essentially an item that can be broken and the aircraft can still take off legally. Note that this is a different (and more rigorous) standard than "can be broken and aircraft can take off/operate safely".
I don't know exactly what broke here but I suspect it is a part that has broken on 737s hundreds if not thousands of times in the past, with similar outcomes.
I merely dabble in software but to further your analogy: This situation is when you've been dreaming about that bug for weeks and you get the call from the boss thinking it has recurred but instead it turns out it was a similar-smelling failure caused by some intern's microservice not failing gracefully when confronted with a network outage that brought down the system anyways.
[0] https://fsims.faa.gov/wdocs/mmel/b-737%20r55a.htm https://fsims.faa.gov/wdocs/mmel/b-737%20r55a.htm
- worker767424 6y agoBut this doesn't feed the machine that is the 24-hour news cycle. I fully expect cable news to try to declare "more trouble for troubled plane," even though it appears to be a garden variety failure.
- weego 6y agoI think that attempts to whitewash the fact that Boeing have managed to burn the trust it spent decades building on the space of 2 or 3 years. This is the natural outcome -- until time proves otherwise again, every failure will be under a lens
- corndoge 6y ago> until time proves otherwise again, every failure will be under a lens But it's really not every failure. There were 2 other failures on Boeing airliners yesterday alone and nobody posted the other two. American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure (OP's article) Southwest B737 at Denver on Mar 30th 2021, speedbrake arming issue United B739 at Denver on Mar 30th 2021, flaps problem Day before Batik B739 at Semarang on Mar 28th 2021, hydraulic fault Aeroflot B738 at Krasnodar on Mar 28th 2021, flaps problems Day before that ANA B773 over Pacific on Mar 28th 2021, engine shut down in flight iAero B734 near Evansville on Mar 27th 2021, loss of cabin pressure Here's a 737-800 with a similar electrical trim issue recently https://www.youtube.com/watch?v=nLonztIXXWQ https://www.youtube.com/watch?v=nLonztIXXWQ You probably didn't hear about that one Like others said these aircraft fail every single day. People who read about them don't post them on HN because they're so common.
- timw4mail 6y agoNot to mention that the 737 series of planes is the most produced passenger plane in history. The odds of none of them having issues on a given day is slim.
- mypalmike 6y agoThese common imperceptible failures... Do they involve the aircraft turning around and flying an hour back to the departure airport?
- na85 6y agoThat would strain the definition of "imperceptible", wouldn't it? My point is that aircraft break all the time. Once in a while they break in such a way that they need to return to base. This wasn't an MCAS failure.
- slacktide 6y agoYes, they do. I suggest that you set avherald.com as your homepage for a week, and learn how common air turnbacks and diversions are.
- qwertox 6y agoFun comment section on that site > This girl is one of a few 757s that Delta uses exclusively for charters. Lower cycles on them. 31.5 years old and still chopping up birds. Love it. Long live the 757!! http://avherald.com/h?article=4e52aeea&opt=0 http://avherald.com/h?article=4e52aeea&opt=0
- conistonwater 6y agoOne "silly" reason why minor failures result in flying back to the original airport is sometimes that the original airport is some sort of hub for the airline with plenty of equipment and personnel for maintenance, which makes it cheaper for the airline to repair the plane specifically there compared to another airport. If you follow avherald.com even a little bit, you will notice a lot of incidents result in exactly that.
- ironmagma 6y agoThe fact it wasn’t MCAS really isn’t important. What is important is that Boeing has completely botched the development of this aircraft and this continues to be revealed to us in new ways over and over again. It’s a management issue through and through.
- trynton 6y ago@na85:"Aerospace engineer here." Appealing to authority. > That statement is from the airline, not from Boeing, so I'm more inclined to trust it .. On an unstable aircraft such as the 737 Max, if the trim fails then the nose pitches-up, precipitating a stall, unless the pilot can execute a manual trim. Which is difficult without electrical-power-assist fed to the wheel. As the wheel was made smaller to allow for bigger displays.
- lisper 6y ago> Appealing to authority. No. He is an authority. He is providing his bona fides. Not the same thing.
- deleted 6y ago[deleted]
- _ph_ 6y agoNo, to expertise. An Aerospace engineer is more qualified to correctly interpret the event report and whether this is a common problem or something related to the previous problems of that model.
- slacktide 6y agoEverything you said is false. The 737 MAX is not unstable, even with MCAS inoperative, and does not have a tendency to pitch up if trim fails or MCAS is inoperative. Source: EASA 737 MAX Return To Service report, top of page 6. https://www.easa.europa.eu/sites/default/files/dfu/B737_Max_Return_to_Service_Report.pdf https://www.easa.europa.eu/sites/default/files/dfu/B737_Max_... The trim wheel on the 737 MAX is exactly the same as the trim wheel on the 737 NG. They have the same part number. Source: my own two eyes and a 12” Mitutoyo caliper. The 737 Classic trim wheel (pre-1997) is approx 1/8” smaller than the NG and MAX trim wheel.
- Toutouxc 6y ago> On an unstable aircraft such as the 737 Max, if the trim fails then the nose pitches-up, precipitating a stall, unless the pilot can execute a manual trim. MCAS is a safety mechanism meant to suppress a very specific behavior in a very specific corner of the flight envelope where an airliner is not supposed to operate at all. Its mere existence doesn't mean that the MAX is an unstable plane. The 737 is still a positively stable airplane, just like basically all civilian aircraft. If the trim on such plane fails (gets stuck), it becomes annoying to fly, like a car that pulls to one direction. It doesn't do anything violent or sudden (the plane is trimmed correctly until the last moment) and it's possible to overcome the force with the control column and return safely.
- danaliv 6y agoFlight instructor here. This person knows what they're talking about.