Yes but this is not a huge problem with the airframe itself. The tendencies without MCAS are fine. The pilots just need to be trained for them.
The problem was that airlines want to skimp on the training.
The same thing happened with the engine management. Boeing doesn't want to introduce an engine warning system because it would mean pilots have to be retrained. A lot of these barriers aren't part of the physical design but the industry as a whole being extremely wary of training. Probably as a result of cheap low-cost carriers emerging.
Not saying Boeing is a great manufacturer but it's not the only issue at play.
You're missing OP's point. MCAS was flawed, but the plane would have been fine if they hadn't added MCAS. It would just have required pilot retraining (which Boeing desperately wanted to avoid). I have never seen a reliable source for the claim that the handling characteristics without MCAS would fail to meet airworthiness requirements.
I think that is unlikely. MCAS was not put in place to avoid training, it is there to fix what would otherwise be an unacceptable handling issue. It was attempting to add MCAS without training that led to all the problems (not mentioning it, using only a single sensor...), and if Boeing could have done without it, it would have done so.
the airplane did not have stable flight characteristics because of its physical design.
that’s a hardware problem.
MCAS only exists because of that hardware problem.
the fact that boeing also did not train or tell pilots about MCAS, in order to make the airplane more financially appealing by retaining the 737 type rating, is a separate (also bad) issue.
I can't agree more. The existence of MCAS is a testament that the behavior of the plane wrt. to the pitch axis is vastly different. Handling this needs training and anyone doubting that please spend a moment on what happens when this savior MCAS has to be switched off. Yes, the pilots need to be able to handle the plane without. And they have to handle the plane at that point in time in an odd flight situation, are stressed themselves and have their hands on hypersensitive engine and rudder controls. Pilots train to handle airplanes with only one engine - there is a reason for that.
Anyone doubting that Boeing needs to have its authority wrt. to airplane certifications cut should ponder what they are proposing here.
That, of course, immediately raises the question of why, then, this was not done.
There is a proximate answer that still does not get us to root causes: An MCAS failure was rated as a Major condition as opposed to Hazardous, in which case the regulations allowed (but did not, of course, require) a single source of input.
This rating was arguably justifiable for the 737 MCAS in its original form, but its power had to be increased significantly after flight testing revealed the original version to be inadequate.
As it happens, the 737 MAX airframe was not the first use of MCAS: the KC-46 also has it. Despite the fact that this system is less powerful than that which was fitted to the initial production 737 MAXs, it uses two AofA sensors. There is clearly a strong and obvious engineering case for doing so, so simply observing that Boeing did not have to do so does not exhaust the questions that should be asked.
I have seen it stated in several places that using two AofA sensors would have required a warning in the case of their being in disagreement, which in turn would require it to be mentioned in the AFM, which might have prompted a reevaluation of the no-training decision, either directly or through a reevaluation of the risk classification. Unless a smoking gun has been found, Boeing can stonewall on whether the training concern suppressed a full and objective evaluation of the risks posed by MCAS (especially after its strengthening), and thereby improperly influenced design decisions (among other issues), but the concern is obvious to everyone except those who want to avoid considering it.
From what I have understood they used MCAS so that they didn't need to reclassify the plane model and that pilots would not need to retrain for it as with the MCAS the handling would be similar to the older planes.
The actual problem might not be with the design but using workarounds to get through red tape of reclassifying and retraining pilots for a new plane
Well yes, the problems of MCAS are not that it exists (although its implementation was definitely debatable, notably the use of a single AoA sensor, and AoA sensor warnings being optional), having FBW and flight envelope correction is not an issue in and of itself.
The issues of MCAS was that it was added specifically to hide type behavioural differences with previous 737s with the specific goal of keeping the type, and thus the entire purpose of MCAS precluded training pilots on its behaviour and edge cases.
You disagree with the statement that roughly the urge to avoid recertifying pilots caused Boeing to not mention MCAS even in manuals, leading directly to these deaths? Because from my pov, Boeing introduced a new failure mode (MCAS failure leading to intermittent forcing of the nose down) without any warning to the pilots.
Now maybe the pilots' standard training should have compensated, and there are obviously maintenance or training deficiencies, but Boeing also knew good and well they were selling planes to pilots with these existing training deficiencies. And should have designed a plane to be operated by real world pilots.
MCAS in itself doesn't seem to have been the problem. The fact that MCAS relied on a single sensor (no idea how that got certified in the first place) and that pilot were not aware of MCAS and how it worked were the problems. The latter was due to Boeing trying to avoid re-training and re-certification of air crew.
I would respectfully disagree. The reason for MCAS existing in the first place is, without it, the flight characteristics of the plane are quite a departure from the standard 737 and can be rather unstable. And the only reason Boeing did that was to circumvent some regulatory restrictions around airframe certification and pilot training. So, you're right in the sense that the MCAS was poorly implemented, but it was only required in the first place because of the abnormally sized engine. Well, not so much the size but the increased size with the same airframe caused it to be moved to a different part of the aircraft.
The design of the plane was a financially motivated one and lead to the MCAS system being required in the first place. And your note on lack of redundancy and not providing additional training - surely the costs there are obvious?
Sure there is. If the design was as inept as widely reported, there’s plenty of reason to be suspicious.
Then there’s the hackiness of MCAS itself. Boeing tried to cut corners and put bigger engines on an ancient plane design that couldn’t accommodate them without deleterious aerodynamic effects.
Then, to help airlines cut corners, they slapped MCAS on it to suppress those effects and obviate the need for pilot training.
Of course, the big “problem” should be easily manageable by any pilot: an upward-pitching tendency under heavy power. If you don’t notice or can’t easily correct for that, you have no business flying a plane.
Well, yes: the plane is inherently unstable. That's why the MCAS system is there. The system itself is mostly fine, it does what it's intended to under ordinary conditions. The problem was that Boeing, in order to avoid costs to the buyer, declared that pilots did not require training on it and made the instrumentation that manages the system woefully inadequate to the task of handling malfunctions (plus the system relying on a single sensor is pretty brittle but adequate malfunction handling instruments would've mitigated that).
I think that there are two issues. MCAS was needed because the airplane wouldn't meet FAA rules without it. Fixes for things like that are not necessarily bad. Problem comes from two issues. Not wanting to require retraining meant they tried to bury the MCAS's existence to the point of not having a way to disable it and only it. And second the flight envelope problems were worse than originally expected. So they gave MCAS more control authority.
They ended up with a problem where bad inputs to the MCAS system could only be countered by disabling the electric trim motors. Once you did that the only way to fix the trim was via a manual wheel which didn't have enough mechanical advantage when the elevators were loaded. That itself was a festering problem carried forward from the original design.
I don't think the air-frame for the 737 MAX is broken, though.
I definitely agree that the MCAS system should have required two AOA sensors, and been automatically disabled when there was a disagree. I agree that Boeing should have briefed airlines and pilots about the MCAS system, the AOA disagree indicator, and potentially required new training.
It’s not like the plane was uncontrollable without MCAS, it’s more that it did not fly like a 737-NG, and so would have required extra pilot training to compensate, which would have made the plane less attractive to airlines.
The problem was that airlines want to skimp on the training.
The same thing happened with the engine management. Boeing doesn't want to introduce an engine warning system because it would mean pilots have to be retrained. A lot of these barriers aren't part of the physical design but the industry as a whole being extremely wary of training. Probably as a result of cheap low-cost carriers emerging.
Not saying Boeing is a great manufacturer but it's not the only issue at play.
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