halls120

Yes, it does. But until we know exactly why they both crashed, speculating on the cause and pointing fingers is a waste of time.

DenverBrian

We're on an IBB. Speculation is one of the prime directives here.

My position is essentially fool me once, shame on you; fool me twice, shame on me. In 2019, when one hears of a fatal crash killing all on board, the reaction is to go "hmm, that's odd and rare." When one hears of two fatal crashes killing all on board, amazingly close together in aviation time given how rare crashes are in general, with striking similarities between the two crashes (same exact model plane, same portion of flight, very similar communications between ground and pilots, etc.)...my reaction is to say "Holy crap, there is something wrong here - not flying on that plane until they figure it out."

Virtually everything I've said in various places on this time-waster of an IBB is a variation on this theme. While others tend to pooh-pooh the whole issue as an isolated coincidence, or point fingers at everything except the plane itself, I'm comfortable in my logic that one looks at the plane first.

It's actually the incredible record of safety in the skies overall that points me in this direction.

And, most certainly, continuing to fly this model of plane while all the speculation and finger-pointing was building was the absolute 100% wrong thing to do. It actually created more people like me, who when the plane starts flying again, will avoid it. Not fewer people like me...more people like me.

ajGoes

The 7373MAXs' nose-up tendency in certain flight regimes is only indirectly related to the size of the engines. The larger engines had to be fitted further forward to allow adequate ground clearance. The particular aerodynamics of the 737MAX mean that when the airplane is flown with a high angle of attack, it tends to pitch further up. Earlier 737s don't behave that way. Boeing added the MCAS to make the MAX feel like earlier 737s.

Other airplane designs would not necessarily behave in anything like the same manner.

EWR764

We do know. The ASRS database is a matter of public record and each of the inflight occurrence reports involved the use of the autopilot... autopilot on = no MCAS. You can read all of them for yourself (and I encourage source-checking when it comes to aviation news reporting).

There was one report which didn't involve an inflight issue, but rather was a post-Lion Air complaint-fest about pilot training and manual updates. That's been a fertile source of quotations in the media but does not reference any actual in-service problems or difficulties.

We can speculate whether anything else might be out there, or have gone unreported, but as far as documented evidence, there's not much to go on.

Because I'd argue it was only filed to regurgitate a lot of the concerns raised in the post-Lion Air environment.

One could make that case that ASRS isn't the proper forum for raising those issues, but there's nothing "besmirching", from my perspective. YMMV.

I missed the complete post yesterday, as some has been deleted...but if you feel that those reported instances are relevant to the MCAS discussion I'd like to hear about it.

LarryJ

The answer is in the name. MCAS is Maneuvering Characteristics Augmentation System.

Due to several factors, the elevator pitch forces are lighter on the MAX in certain high AoA situations and steep turns. The purpose of MCAS is to provide a nose-down bias, through the introduction of nose-down stab trim, in those situations so that the control feel, i.e. maneuvering characteristics, will be more similar to the 737 NG on which many MAX pilots are dual-qualified.

This will also help in an approach-to-stall situation, but that is not its primary purpose (regardless of all the media reports and assumptions).

As far as stall protection goes, some other transport airplanes have a stick-pusher which will forcefully push the elevator to the nose-down position as a stall is approached. This is much more aggressive than the intermittent nose-down trim that the MCAS provides. The reason that those other airplanes have a stick-pusher, and the 737 does not, is that those airplanes have more adverse stall handling/recovery characteristics than does the 737. You can bet that those pilots know the procedures for quickly deactivating the stick-pusher!

Airplanes that I've flown with stick-pushers include the old Jetstream 32 and CRJ series. The DC9 had a system similar to a stick pusher but different in that it would activate, pushing the elevator towards nose-down, when the elevator doesn't respond to nose-down yoke input. This would likely be due to tail-blanking (reduced airflow over the T-Tail in high AoA situations due to the wing creating a "shadow" of low airflow over the stabilizer). The DC9s elevators were unpowered and relied on airflow to position the elevators in response to control-tab movement. The control-tabs were connected to the control wheels by cables.

Any failure is possible.

The MCAS system is designed so that it is inhibited with the autopilot engaged (the A/P doesn't need it) and when the flaps are extended (the lighter pitch response doesn't exist with flaps extended). It's certainly possible that the flap-inhibit failed but that would mean that there were at least two separate failures (the invalid MCAS trigger and the MCAS flap inhibited) occurred simultaneously. Lacking any evidence of such a dual failure, occam's razor would suggest that the simpler answer is the more likely answer. At this time, we know very little about what actually happened on the Ethiopian flight.

It sounds like we'll be getting info from the ET302 DFDR soon and hopefully that will have some answers to these questions.

LarryJ

In 1965, three newly-introduced B727-100s crashed in the US in a three-month period.

Those crashes weren't due to a flaw in the airplane. They were due to the procedures which were carried over from flying prop-driven airplanes which had instant power availability compared to the slow spool-up characteristics of a turbine engine. The proper procedure with a jet is to have the engines spooled up by 500' - 1000' before landing so that power will be available instantly if needed. Pilots transitioning from propeller-driven airplanes weren't always complying with that procedure.

Modern turbine engines additionally mitigate that threat by having higher in-flight idle settings which reduce the spool-up time from flight-idle. This also makes the newer airplanes harder to slow-down and descend quickly which does lead to some go-arounds when the pilots are brought in on a tighter approach than they were expecting.

JimInOhio

My memory is now quite fuzzy on this but wasn't the 787 battery issue related to ground charging of the battery? If true, that wouldn't be a flight issue, per se.

EmailKid

Um, no.

Precisely because the meltdown issue could occur in flight was why the 787 was grounded.

Same reason why LiOn batteries are not allowed in checked luggage.

DenverBrian

That's 54 years ago. I would think we've progressed somewhat in safety so that today, two in five months is far from normal. @:-)

DenverBrian

Unless MCAS is being accidentally triggered with the autopilot on. @:-)

It's interesting to me how some will claim "we simply don't know enough to make a determination" and then several posts later will claim "we know exactly how this works and there's no possible way it could ever work differently or incorrectly."

spin88

I am sure that these reports will be carefully investigated. They could be unrelated or the same programing found in the MCAS system could also be in some form in the auto-pilot (doing a noise down command from a single AoA input). Keep in mind that this is what happened on the 2010 LH A321 flight, the flight that should have alerted Boeing under a DFMEA process to plan for and have redendency on the issue of AoA sensor. The big picture though is that (a) these reports supported the grounding of the MAX to figure out what the hell was going on after two - what appeared to be related crashes - but (b) they at most suggest that the automated systems on the MAX need to be (1) reprogrammed, (2) have more redundancy, and (3) when they override any pilot's manual input need to be part of the training.

IMHO, Boeing cut some serious corners with the MAX. It really undermines my faith in their management and engineers that they did what they did with the MCAS to avoid having to train pilots more fully and then did such a ham handed job (single AoA sensor) of design. However, I have no doubt that what they put out as the "fix" will fix the problem, and we will not see any more MCAS crashes on the MAX.

EWR764

There is no evidence at all of this ever occurring, even after the close scrutiny the type has come under since Lion Air, and certainly after the grounding. In fact, I don't think it's even something under consideration in the broadest sense.

Is that observation directed at me? Because I don't think I've ever made any such a conclusory statement in connection with this matter.

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One confusing issue is the fact that MCAS keeps being called "autopilot" in the news media, which is incorrect. It's an automated flight control system, but it augments manual flight. There's simply no purpose for MCAS when autopilot is engaged.

When autopilot is engaged, my understanding of the systems architecture is that the flight control computer considers two channels to identify an indicator disagree before sending inputs to various actuators.

Why this same level of redundancy wasn't implemented in the MCAS system, I can't, for the life of me, understand.

I'm pretty much with you until you get to their point where you suggest that the referenced ASRS entries support a grounding of the 737MAX. Each report involve different phases of flight, different systems, different failure modes and different presentation of anomalies. If those 19 entries (some of which have nothing to do with flight control, like failure to abort an unstabilized approach, inop wifi, incorrect FMC entries, etc.) are sufficient to support a grounding of the 737MAX, then I'm sure you can find some common threads in the 2400+ other 737 Classic/NG ASRS reports in the same period of time that would "support" the grounding of the rest of the fleet...

BF263533

And about 10 years before that the cabin width of the 707 wss being set carrying over to the 1960s 737. Today's 737 is like a 95 year old on his 3rd heart transplant. You can only extend the life of something so long before it gives out.

Newman55

I fail to see how the cabin diameter of an aircraft means anything to this discussion. If you think mechanics on the current generation of 737 is similar to what was designed in the 1960s, then I guess we should discuss the safety of current A320 family.

radonc1

When my wife was flying a lot for business, the DC-10 was having some "issues" like crashing, and there was anxiety over it's airworthiness. But 6 months after they fixed the problem (cargo door, I believe) she was flying on it without a concern.
I suspect that while you may avoid the 737 Max from now on, most people will put this behind them and fly whatever plane is sitting at the gate. In fact, I suspect that if you asked a plane load of passengers, less than 10% of them would even know what model of plane they were on, and fewer would have chosen the specific model they were flying on.

So I think that, as in 1983, once the fix is done and the planes are flying, most will forget about this unfortunate series of tragedies and move on. It is how most of us deal with life.