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Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

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Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#111

Post by manigandham »

satellite2 wrote: post #72
manigandham wrote: post #47

Earlier quoted context omitted.

It does not just pitch up randomly. It does pitch more than other 737s due to engine size and placement, but that's just the specific behavior of this plane. Stalls are not a serious problem, they're basically the first thing pilots learn to solve. And there are plenty of aircraft that are more challenging to fly. That's what training is for. The real issue is that pilots should have full understanding of the behavio…

> Stalls are not a serious problem They account for 25% of fatal accidents [1] [1] https://www.aopa.org/-/media/Files/AOPA/Home/Pilot-Resources...

The source says "the overwhelming majority of unintended stalls occur on personal flights in day visual meterological conditions (VMC) under light winds". And the commercial flights are mostly part 137 (aerial application like agriculture and fire fighting).

So to add context, stalls under commercial part 135 flights are extremely rare and even less fatal. There's almost always some other compounding issue that led to the stall instead of just basic flight maneuvering.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#112

Post by timw4mail »

corndoge wrote: post #94
weego wrote: post #87

Earlier quoted context omitted.

I 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

> 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…

Not 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.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#113

Post by chipsa »

geocrasher wrote: post #23
cratermoon wrote: post #17

Earlier quoted context omitted.

No, they are legit flaws . https://www.business-standard.com/article/international/boei...

I respectfully disagree. A news article calling them flaws does not make them a flaw. Here's the issue: At lower speeds such as you'd see during a landing approach, the throttle setting of the 737 Max directly affects its pitch. If the pilot were to suddenly reduce throttle, the nose would pitch up. This is due to the engine's more forward position. The forward position of the engines was done so that they wouldn't h…

Most airliners have the engines under the wings (and therefore under the CG). Thus, most airliners will pitch up when thrust is applied. The 737 Max has a higher thrust line (which means closer to the CG) than prior 737s. The nose will pitch up less than other 737s when applying power. The problem isn't pitching up when applying power.

The problem is that at high angles of attack, the nacelles start to produce lift, and with the more forward position, they cause a greater pitch up force than previous versions.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#114

Post by jryle70 »

martimarkov wrote: post #10
geocrasher wrote: post #3

"- 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." Indeed. This was a part failing on an aircraft in flight. It landed without incident, and was likely never in any sort of danger. Losing electric trim is an annoyance but also trims…

I agree but it’s like the galaxy phone that had the battery issue. It just killed confidence with the consumer. The investigation (and what we learned form it) into Boeing also didn’t help with confidence levels. After a few new iterations nobody talks about the battery anymore. I’m not so sure how Boeing can turn this around relatively quickly.

Southwest just placed a large order for 737MAX-7 two days ago - [0]. 100 firm orders plus 155 options. They may get a great deal from Boeing for all we know, but placing a large order during this terrible time for the airlines is a bet on the future of MAX as well as the industry recovery.

[0] - https://www.cnbc.com/2021/03/29/southwest-airlines-adds-100-...

Meta note, this relatively frequent aircraft incident gets a lot of votes here on HN, yet the Southwest's order falls off the crack. Objectivity is as scarce on HN as on any other media frequently criticized here.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#115

Post by geocrasher »

chipsa wrote: post #113
geocrasher wrote: post #23

Earlier quoted context omitted.

I respectfully disagree. A news article calling them flaws does not make them a flaw. Here's the issue: At lower speeds such as you'd see during a landing approach, the throttle setting of the 737 Max directly affects its pitch. If the pilot were to suddenly reduce throttle, the nose would pitch up. This is due to the engine's more forward position. The forward position of the engines was done so that they wouldn't h…

Most airliners have the engines under the wings (and therefore under the CG). Thus, most airliners will pitch up when thrust is applied. The 737 Max has a higher thrust line (which means closer to the CG) than prior 737s. The nose will pitch up less than other 737s when applying power. The problem isn't pitching up when applying power. The problem is that at high angles of attack, the nacelles start to produce lift,…

This sounds very plausible, but I haven't heard this before. Do you have a reference? I'm genuinely curious- not calling you out, so to speak.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#116

Post by fsckboy »

HeWhoLurksLate wrote: post #12
martimarkov wrote: post #10

Earlier quoted context omitted.

I agree but it’s like the galaxy phone that had the battery issue. It just killed confidence with the consumer. The investigation (and what we learned form it) into Boeing also didn’t help with confidence levels. After a few new iterations nobody talks about the battery anymore. I’m not so sure how Boeing can turn this around relatively quickly.

Speaking of which, I have a friend that still runs a Note7

weren't those banned from flying on 737MAX's? (and all other aircraft)

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#117

Post by eric4smith »

BillyTheKing wrote: post #107
eric4smith wrote: post #13

I sympathize with the engineers there. It's like a bug that will not go away in some software. You think you've fixed it and all seems well and you get a good nights sleep with the gleam of satisfaction in your eyes. But the next day your manager says "That bug is still there". You incredulously do not believe that bug report and go to replicate it yourself. And surely, under some edge weird case scenario, it really…

the good old programming testing rule: the number of bugs you will find in a piece of software is proportional to the number of bugs you already found

Lol so true.

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#118

Post by hnarn »

qubit000 wrote: post #110

Boeing has lost the public trust not only in the US, but internationally. Inherent instability aside, fact remains the general perception is that Boeing retrofitted engines too large for 50yr plane design necessitating structural modifications which compromised its flight worthiness. As a result, software had to be written to compensate for this, which unbelievably, relied on input from a single sensor--iow, single p…

What has really ruined my trust for Boeing is not necessarily the incidents with the 737 MAX model specifically, but more the change in that company's culture that these incidents have made me aware of. I can recommend this video[1], but the short of it seems to be that Boeing over a period of decades has replaced its previous "engineering first" culture with what I can only describe, for lack of better wording, as the "suits taking over", with predictable results.

[1]: https://www.youtube.com/watch?v=y_zn_x2JK5Q

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#119

Post by mrguyorama »

VBprogrammer wrote: post #101
slacktide wrote: post #86

Earlier quoted context omitted.

Predicated on their assumption that the flight control laws would prevent a nose-up control input from stalling the aircraft, and not realizing that the aircraft was in alternate law. Some of the last words on the CVR from the pilot flying were “But I’ve been at maxi nose-up for a while” while the computer was shouting STALL STALL STALL in the background.

You ever have the experience when you listen to someone speak with a strong accent, you don't quite catch the beginning of a word and the whole of what they say sounds like a foreign language? I imagine that is how those poor pilots felt as their instruments screamed conflicting information at them as they tore through the skies above the mid-atlantic.

A huge problem with that incident is that as the plane got deeper into the stall, the computer decided it couldn't get an accurate idea of what was going on and STOPPED giving the stall warning. This lead to the crummy situation where pulling back on the stick made the warnings go away, despite being the exact opposite control input required.

This situation is 100% opposite of basic stall recovery, but I don't know how much that still works when you are panicking and no longer feel like you can trust your instruments or your plane

Re: Incident: American B38M near Nassau on Mar 29th 2021, pitch trim issue/failure

#120

Post by VBprogrammer »

mrguyorama wrote: post #119
VBprogrammer wrote: post #101

Earlier quoted context omitted.

You ever have the experience when you listen to someone speak with a strong accent, you don't quite catch the beginning of a word and the whole of what they say sounds like a foreign language? I imagine that is how those poor pilots felt as their instruments screamed conflicting information at them as they tore through the skies above the mid-atlantic.

A huge problem with that incident is that as the plane got deeper into the stall, the computer decided it couldn't get an accurate idea of what was going on and STOPPED giving the stall warning. This lead to the crummy situation where pulling back on the stick made the warnings go away, despite being the exact opposite control input required. This situation is 100% opposite of basic stall recovery, but I don't know h…

The phrase "the computer decided" gives way more agency to the computer than it deserves in this instance. In reality it was a simple airspeed threshold below which no one imagined the aircraft actually flying.

It was a really tragic accident with many lessons for anyone involved in the design of critical systems.

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