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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

#81

Post by slacktide »

stryker7001 wrote: post #45

So if the situation came, where the plane was at the edge of its flight envelope and needed to use MCAS (or whatever its called now), it wouldn't have been able to use it, causing the plane to stall? Thats a lot more serious then.

Nope. “The EASA flight tests confirmed that MCAS was needed to provide full compliance but also that the loss of this function does not preclude the safe flight and landing of the aircraft; i.e. the 737 MAX remains stable following the loss of the MCAS function.”

https://www.easa.europa.eu/sites/default/files/dfu/B737_Max_...

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

#82

Post by sharken »

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.

For starters they can reiterate what has been said here, that a common error occurred and not the original MCAS problem.

Not being open about it will have the opposite effect.

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

#83

Post by jiofih »

Toutouxc wrote: post #69
trynton wrote: post #58

Earlier quoted context omitted.

@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 bigg…

> 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 posi…

An out of whack MCAS that pushes the nose down, to a point where you can’t overcome it with the trim control, technically puts it into the “unstable” category, doesn’t it?

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

#84

Post by onethought »

trynton wrote: post #58
na85 wrote: post #20

Earlier quoted context omitted.

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 airwor…

@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 bigg…

Not a 737 Pilot. Can the pilot not just push the nose back down with the stick?

How difficult is a manual trim? Can one pilot not hold the stick while the other trims?

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

#85

Post by Toutouxc »

stryker7001 wrote: post #45

So if the situation came, where the plane was at the edge of its flight envelope and needed to use MCAS (or whatever its called now), it wouldn't have been able to use it, causing the plane to stall? Thats a lot more serious then.

The plane doesn't really NEED to use MCAS. Systems like MCAS or Speed Trim and others do not make the planes flyable, they make them predictable. Aerodynamically, even the 747 or the A380 are normal planes operating on the same principles as the tiny Cessna 172, they're just much bigger, fly faster and react a lot slower.

Airliners are packed with systems that make them dull and predictable to fly, because things can break on a sunny day over Texas, but also at midnight in the rain over the Atlantic, and the last thing you want your pilots to care about when they're stressed out, disoriented and working through complicated checklists is whether this particular plane has a weird tendency to pitch up at these particular conditions.

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

#86

Post by slacktide »

bonzini wrote: post #76
dghlsakjg wrote: post #60

Earlier quoted context omitted.

Almost every airplane except the absolute most basic have trim controls for flight surfaces, especially the elevator. Even little two seat Cessnas get trim controls. Trim is changed for each phase of flight. Electric trim is just a motor spinning the manual trim control. Most airliners will be doing constant trim adjustment. If you want a real change of pace check out Airbus’ control system. It does a lot more interv…

AF447 was definitely pilot error, not realizing that the aircraft was stalling.

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.

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

#87

Post by weego »

worker767424 wrote: post #25
na85 wrote: post #20

Earlier quoted context omitted.

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 airwor…

But 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.

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

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

#88

Post by jrockway »

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...

Seems like the vast majority of cases there are personal aircraft not piloted by ATPs. General aviation is what it is. Certainly there are airline pilots that don't recover from stalls successfully (Colgan Air Flight 3407's crew), but there are confounding factors like sleep deprivation. Personally, I worry a lot more about sleep deprivation than particular subsystems of jetliners. You can easily kill two airliners worth of people in a few seconds when you read back "hold short of runway 31R" and then just barel onto it because you're not alert.

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

#89

Post by brainwipe »

trynton wrote: post #58
na85 wrote: post #20

Earlier quoted context omitted.

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 airwor…

@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 bigg…

Appealing to authority is when you say:

"I am X, believe what I say on trust..."

...without giving any further evidence, logic, reasoning or demonstration of that experience. The commenter demonstrated in detail, gave things to look up and specified limits to his knowledge. Appeal to authority doesn't apply here.

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

#90

Post by slacktide »

onethought wrote: post #84
trynton wrote: post #58

Earlier quoted context omitted.

@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 bigg…

Not a 737 Pilot. Can the pilot not just push the nose back down with the stick? How difficult is a manual trim? Can one pilot not hold the stick while the other trims?

If the airplane is slightly out of trim, yes, but it is tiring. If it is grossly out of trim, then it may require full effort with both arms.

Similarly, if the airplane is slightly out of trim, manual trim adjustment is no big deal and does not require a lot of force or attention. If the airplane is grossly out of trim, the air loads can prevent manual movement of the trim wheel. Boeing previously provided guidance in the Quick Reference Handbook to briefly relax elevator control inputs while adjusting trim if this occurs, but that guidance was apparently removed many years ago. Was colloquially referred to as the roller-coaster maneuver, sounds like great fun for the folks in back.

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