Ed 737 Max Crashes (was Shutdown caused Boeing crash.)

[a_unique_person]

My apologies if this was already answered up thread:



Did activation of the MCAS nose-down function generate a clear warning to the pilots? An audible alarm ("Anti-stall nose down trim activated"..."Anti-stall nose down trim activated") or something equivalent?



Many of the accounts I've read suggest that the pilots were, at least initially, unaware that the MCAS system had become activated and was operating the stabilizer trim "in the background." If true that appears to be a significant flaw in the design of the system.

No. MCAS is supposed to provided a little tweak to the trim to make the stick feel heavier instead of lighter so that the plane feels just like an NG in a situation approaching steal. Otherwise the engines provide aerodynamic lift that makes the feedback forces on the yoke feel lighter and fools the pilot into thinking it's less likely to stall than more likely to stall.

That is all supposed to happen without the pilot having to be aware of it.

 

[smartcooky]

turning off teh Stab Trim switches may disable the electric trim system, but the pilots can still trim the pitch using the trim wheels.

"In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds," Boeing explained to operators in a bulletin issued last November, following the JT610 accident. "The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 sec. after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated." (url=https://www.mro-network.com/airlines/faa-stays-course-planned-max-changes-no-groundings]source[/url])

This is where we get this 15 second cycle from;

I reiterate what I said earlier. Any system capable of autonomously pitching the nose down when the aircraft is at low altitude is a recipe for disaster. There is no way this should ever happen at 450 ft and V2+15 kts.

This is a flawed design

 

[Trebuchet]

I agree it's a flawed design. And I used to work there. I'm glad I don't now.

Regarding the trim wheels: When the NG was being introduced, I happened to be the Lead Engineer in charge of them and a whole lot of other stuff. There were some issues. The new display system created a pinch point between the dash and the wheel. We had to make the wheel smaller. And the new trim motor resulted in the wheel, which is directly connected to the stabilizer by a long cable, springing back when electric trim was used. It was an undamped mass on the end of a spring. We had to add a damper.
Result: Depending on the flight conditions, the force to manually trim can be extremely high. We set up a test rig and a very fit female pilot could barely move it.
As I said, I'm glad I'm no longer there.

 

[ponderingturtle]

No one suggested that.

Sure they have been, their very existence is a good example of the kind of crushing regulation that the airplane manufacturing industry face. Fortunately they are allowed to self certify and get out of all that bothersome testing with

Of course, we should expect the FAA to be far more involved in certifying commercial aircraft. But I don’t think it’s that unusual for them to do so largely via oversight, vs direct, hands on testing.

And of course those regulations have also been successfully cut back because regulation=bad!

I think that paints with too broad a brush and is way too cynical. But you’re entitled to your.opinion.

Why would Boeing be so different from GM that let a known defect kill dozens to hundreds? I mean sure GM was engaging in criminal actions but of course that doesn't really mean much when it is a company it isn't like the people deciding to let people die faced any personal consequences.

https://money.cnn.com/2015/09/17/news/companies/gm-recall-ignition-switch/index.html

"GM had already admitted that its employees were aware of the problem nearly a decade before it started to recall millions of the cars early last year. That delay is the basis behind the criminal charges.

"People were hurt and people died in our cars," GM CEO Mary Barra told employees Thursday afternoon. "That's why we're here today."

The settlement was disclosed Thursday by the Justice Department. No individual GM executives were charged in the case -- a fact that was called "grossly inadequate" by the mother of a crash victim."


Letting a lethal defect go for a decade is just what you have to expect.

 

[jeremyp]

Why would Boeing be so different from GM that let a known defect kill dozens to hundreds?

Because a few plane crashes due to a design defect is all that’s needed to destroy the commercial viability of an aircraft model. A lesser company than Boeing would probably be finished by the adverse publicity they have received from this. Even if Boeing survives (they probably will), the 737 max is probably done.

 

[Ziggurat]

Why would Boeing be so different from GM that let a known defect kill dozens to hundreds?

One of the ironies here is that Boeing got in trouble here partly because it tried NOT to let a safety defect go through, but just failed to address it properly. Had they really been indifferent like GM, they wouldn't have bothered with the MCAS system to limit angle of attack. After all, most pilots won't put the plane into a stall condition, and if they do, that's the pilot's fault. But neither plane that crashed did so because of a stall from too high an angle of attack. Had Boeing not tried to fix the stall problem with MCAS, those planes might not have crashed.

But as jeremyp suggested, the financial incentives for Boeing are different than they were for GM. Commercial jet customers aren't casual buyers. They're airlines who buy entire fleets of the same aircraft, and research their multi-million dollar purchases intensely. If there's a safety problem with an aircraft, the airlines notice quickly, and have strong incentive to simply not buy that plane at all. A car buyer might chance buying a less safe model, but airlines are risk averse.

 

[smartcooky]

Because a few plane crashes due to a design defect is all that’s needed to destroy the commercial viability of an aircraft model.

Commercial jet customers aren't casual buyers. They're airlines who buy entire fleets of the same aircraft, and research their multi-million dollar purchases intensely. If there's a safety problem with an aircraft, the airlines notice quickly, and have strong incentive to simply not buy that plane at all.

Case in point: The DC-10

Pilots will tell you that the DC-10 was a great aircraft, a pleasure to fly and has an overall safety record that compares favourably with other similar aircraft types. However, some serious design flaws, safety issues and catastrophic hull losses early on pretty much put this aircraft on the back foot, and it never recovered from its reputation as "Death Cruiser 10"

1972 - American 96 (Cargo Door blew out - A/C landed safely)
1974 - Turkish 981 (Cargo Door blew out - A/C lost - 346 fatalities
1979 - American 191 (Engine fell off - A/C lost - 273 fatalities
1979 - United 232 (Engine failure cut all hydraulic lines to empennage control surfaces - A/C lost - 111 fatalities

As a result, airlines were not interested in buying, and they haven't been built since 1988. You pretty much only see them in Cargo service now. KC-10 tankers are still used by the USAF and, AFAIK by the Dutch Air Force.

 

[Puppycow]

We know manufacturers don't really care be they Boeing or GM, they are happy to have customers die as long as it does not result in bad press.

But it will result in bad press, and lawsuits.

This is one of those cases where everyone's interests are aligned. Nobody (among the manufacturer, the airline, and the passengers) wants the plane to crash, because that is a very bad outcome for all three. Therefore it is in Boeing's interest to make sure that its planes are safe. They have had a very good safety record overall, these 2 recent crashes excepted.

 

[ponderingturtle]

But it will result in bad press, and lawsuits.

This is one of those cases where everyone's interests are aligned. Nobody (among the manufacturer, the airline, and the passengers) wants the plane to crash, because that is a very bad outcome for all three. Therefore it is in Boeing's interest to make sure that its planes are safe. They have had a very good safety record overall, these 2 recent crashes excepted.

And how is that different from from GM? They don't want their cars to crash but they also are on record for simply not caring about the deaths involved? The market will clearly resolve the situation and they clearly shouldn't have been charged with those felonies(the company of course no actual people would ever be blamed for something like this).

 

[TurkeysGhost]

And how is that different from from GM? They don't want their cars to crash but they also are on record for simply not caring about the deaths involved? The market will clearly resolve the situation and they clearly shouldn't have been charged with those felonies(the company of course no actual people would ever be blamed for something like this).

The difference is the consumer and the regulatory environment. A major plane crash will be investigated such a thorough way that is not comparable to what happens when a fatal car accident occurs. Also, Boeing sells planes mostly to other large businesses that are going to engage in much more diligence than the typical car shopper. Simply put, GM has some reasonable hope of keeping a defect secret, where Boeing does not. If the defect is serious enough to cause a real problem, it's in Boeing's interest to fix it before their customers find out the hard way.

 

[ponderingturtle]

The difference is the consumer and the regulatory environment. A major plane crash will be investigated such a thorough way that is not comparable to what happens when a fatal car accident occurs. Also, Boeing sells planes mostly to other large businesses that are going to engage in much more diligence than the typical car shopper. Simply put, GM has some reasonable hope of keeping a defect secret, where Boeing does not. If the defect is serious enough to cause a real problem, it's in Boeing's interest to fix it before their customers find out the hard way.

See the problem is the excess regulation. Just what our president is fighting against!

 

[Ziggurat]

The difference is the consumer and the regulatory environment. A major plane crash will be investigated such a thorough way that is not comparable to what happens when a fatal car accident occurs.

In addition, mechanical failures in cars don't generally lead to fatal crashes, because usually when a car stops working, it simply stops. An airplane can't stop until it reaches the ground, and if it does so in an uncontrolled manner, then everybody dies. So there's a lot more fault tolerance in cars than in planes, just by the nature of what they do.

 

[Fast Eddie B]

So there's a lot more fault tolerance in cars than in planes, just by the nature of what they do.

 

[jeremyp]

And how is that different from from GM? They don't want their cars to crash but they also are on record for simply not caring about the deaths involved? The market will clearly resolve the situation and they clearly shouldn't have been charged with those felonies(the company of course no actual people would ever be blamed for something like this).

People don’t refuse to get in cars simply because a couple of them have crashed. There have recently been a few well reported crashes involving Teslas, but I have not heard of anybody saying “they are too dangerous, I wouldn’t bet seen dead... scratch that last word ... in a Tesla”. However, I’ve seen many messages on the various forums I frequent in which people have said “I’ll never travel on a 737 MAX” or “I’ll never travel on an airline that uses the 737 MAX” or even “I’ll never travel on a Boeing 737”. This last is especially irrational, since the NG has a pretty good safety record as far as I know.

 

[William Parcher]

Sensor damaged by a foreign object on Ethiopian Airlines 737 MAX triggered fatal crash: Sources

The Ethiopian Airlines Boeing 737 MAX, which crashed in March and killed 157 people, suffered a damaged angle-of-attack sensor upon takeoff from a bird or foreign object, triggering erroneous data and the activation an anti-stall system -- called MCAS -- sending the pitch of the plane downward and ultimately crashing into the ground, two aviation sources familiar with the investigation told ABC News.

As the jet was nose diving, the Boeing 737 MAX pilots did not try to electronically pull the nose of the plane up before following Boeing's emergency procedures of disengaging power to the horizontal stabilizer on the rear of the aircraft, according to the sources.

One source told ABC News that they manually attempted to bring the nose of the plane back up by using the trim wheel. Soon after, the pilots restored power to the horizontal stabilizer.

With power restored, the MCAS was re-engaged, the sources said, and the pilots were unable to regain control and the plane crashed.

The preliminary findings in the crash investigation are expected to be released by transportation officials in Ethiopia on Thursday morning.

Earlier Wednesday, Boeing released a statement that said, "we urge caution against speculating and drawing conclusions on the findings prior to the release of the flight data and the preliminary report."...

https://abcnews.go.com/Politics/dam...y?id=62139860&cid=clicksource_77_null_bsq_hed

 

[smartcooky]

Sensor damaged by a foreign object on Ethiopian Airlines 737 MAX triggered fatal crash: Sources

https://abcnews.go.com/Politics/dam...y?id=62139860&cid=clicksource_77_null_bsq_hed

Well if this is true, then that 100% confirms my view that this MCAS system is a deeply flawed design.

There is no way that one failed sensor should ever put an aircraft in danger of crashing. Whoever designed such a system, and whoever approved such a system for flight needs to be brought to account.

FWIW, I think the whole idea of an autonomous anti-stall system is madness. Stalls and potential stalls should be managed by the pilots.... that is what they are there for.

 

[a_unique_person]

Well if this is true, then that 100% confirms my view that this MCAS system is a deeply flawed design.

There is no way that one failed sensor should ever put an aircraft in danger of crashing. Whoever designed such a system, and whoever approved such a system for flight needs to be brought to account.

FWIW, I think the whole idea of an autonomous anti-stall system is madness. Stalls and potential stalls should be managed by the pilots.... that is what they are there for.

Airbus prevents stalls. They aren't supposed to happen. MCAS is not supposed to prevent stall but activates when there is a high AoA that is nearing a stall to give the MAX the same "feel" to the pilot as the NG. Hence, no training is required in the Sim to move from the NG to the MAX.

 

[smartcooky]

Airbus prevents stalls. They aren't supposed to happen. MCAS is not supposed to prevent stall but activates when there is a high AoA that is nearing a stall to give the MAX the same "feel" to the pilot as the NG. Hence, no training is required in the Sim to move from the NG to the MAX.

In the the case of MCAS it points the bloody sharp end downwards... autonomously, regardless of pilot input. Unacceptable IMO, and doubly so at 450 feet and V2 +15kts on climbout.

It would be barely more acceptable if, after the MCAS has pointed the nose down, ANY manual effort by the pilot to pull the nose up, whether by trim wheel or yoke input, automatically trips MCAS out and leaves it tripped out until it is manually reset by the pilot

 

[a_unique_person]

In the the case of MCAS it points the bloody sharp end downwards... autonomously, regardless of pilot input. Unacceptable IMO, and doubly so at 450 feet and V2 +15kts on climbout.

It would be barely more acceptable if, after the MCAS has pointed the nose down, ANY manual effort by the pilot to pull the nose up, whether by trim wheel or yoke input, automatically trips MCAS out and leaves it tripped out until it is manually reset by the pilot

Yes, that is how it changes the feel of the yoke, by pointing the nose down. An ugly hack and not well implemented.

 

[Fast Eddie B]

FWIW, I think the whole idea of an autonomous anti-stall system is madness. Stalls and potential stalls should be managed by the pilots.... that is what they are there for.

To be fair, all pilots are trained in recognizing and ways to avoid stalls almost from the very beginning of their training. Wings are designed so that the stall begins at the wing root and progresses outwards, allowing the ailerons to remain effective for roll control even when the inboard portion of the wing is stalled. Most, but not all, small aircraft have some sort of stall warning systems to aid the pilot in that regard.

But large jets with swept wings are much less forgiving. Hence the need for more sophisticated warning systems. It can be a horn or light, followed by a stick shaker and then a stick pusher in some planes. If one wing stalls first, the plane can enter a spin - recoverable in most small planes but possibly not in a large jet.

Anyway, it’s hardly fair to automatically blame the pilots for not “managing” the perceived stall warnings properly.