Another (2nd) 737 Max 8 crash

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#2240950 19-May-2019 20:14

kingdragonfly: Could US pilots have saved the 737 MAX8 ? - Prof Simon

Professor Simon Holland: "I am getting a lot of YouTube comments, saying US pilots would have been able to save the Ethiopian 737 Max 8. We put this to the test."

This was pretty much what we'd discussed above.

Under the same situation using the same data as the Ethiopian pilots encountered the plane was still uncontrollable in the simulator, because they were still flying at take-off thrust.

When take-off thrust was reduced so the aircraft wasn't overspeed it was recoverable.

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#2240978 19-May-2019 21:05

sbiddle:
kingdragonfly: Could US pilots have saved the 737 MAX8 ? - Prof Simon

Professor Simon Holland: "I am getting a lot of YouTube comments, saying US pilots would have been able to save the Ethiopian 737 Max 8. We put this to the test."

This was pretty much what we'd discussed above.

Under the same situation using the same data as the Ethiopian pilots encountered the plane was still uncontrollable in the simulator, because they were still flying at take-off thrust.

When take-off thrust was reduced so the aircraft wasn't overspeed it was recoverable.

No one should ever have to fly in a plane where it is touch and go as to whether a life or death situation is recoverable or not. I find the discussions in this thread ridiculous - ie. that the travelling public's life should be solely in the hands of a pilot's innate sense of survival when thrust into a life or death emergency by the plane's manufacturer.

We should never be put in that situation in the first place. I hope Boeing pay dearly.

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#2241050 19-May-2019 23:14

dafman:

No one should ever have to fly in a plane where it is touch and go as to whether a life or death situation is recoverable or not. I find the discussions in this thread ridiculous - ie. that the travelling public's life should be solely in the hands of a pilot's innate sense of survival when thrust into a life or death emergency by the plane's manufacturer. We should never be put in that situation in the first place. I hope Boeing pay dearly.

Yes, some of the discussion in this thread is ridiculous. I'll leave it to you to figure out which parts of the discussion I'm referring to.

The point you're missing it wasn't touch and go and the outcome wasn't dependant on the pilots innate sense of survival.

It was dependant on them following pre ordained procedures which they should have been trained on and and should have been familiar with.

The crew had a discrepancy (mis-compare) between airspeed and angle of attack. They didn't follow the procedure they should have been trained for - that is set about 75% thrust and 4 degrees nose up. Instead they left take off power set and over sped the aircraft
They didn't use the electric trim to re trim the aircraft prior to switching the electric trim off which was in contradiction of Boeing's published procedures. Instead they ended up with a severely out of trim aircraft which was over speeding and thus very difficult to trim manually.

In the initial stages of the incident there was adequate time to complete these procedures without needing super human efforts and/or techniques to recover the situation.

Boeing are not the only ones with any responsibility here.

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#2241109 20-May-2019 07:34

dafman: No one should ever have to fly in a plane where it is touch and go as to whether a life or death situation is recoverable or not. I find the discussions in this thread ridiculous - ie. that the travelling public's life should be solely in the hands of a pilot's innate sense of survival when thrust into a life or death emergency by the plane's manufacturer. We should never be put in that situation in the first place. I hope Boeing pay dearly.

I hope you're never planning to fly on another commercial airliner ever again - because I don't see how you can.

It's quite appropriate that the QF72 incident has been covered extensively in the media in recent days due to the book launch, because there are incredible similarities to the MAX incidents. Like the MAX incidents it was the pilots innate survival skills that saved that A330 from being another statistic.

You want to ignore the statistics, but it's pretty clear pilot training and skill does seem to be a significant contributing factor when it comes to suitability of incidents caused by both automation and human failure in aircraft.

You're also completely ignoring the fact Airbus have had multiple issues with pitot AOA sensors and ADIRU as well that have lead to catastrophic disasters as well - AF447 and the Air NZ A320 crash are both classic examples where pilots made mistakes due to automation failures that lead to fatal outcomes.

After what's happened in recent months I regard the MAX as now being one of the safest aircraft in the sky and would happily fly on one. It scares me that other aircraft out there that have not had every aspect of their flight control system inspected with a fine tooth comb as a result of incidents meaning they could easily have flaws as simple as the MAX did.

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#2244686 24-May-2019 16:05

Technofreak:
In the initial stages of the incident there was adequate time to complete these procedures without needing super human efforts and/or techniques to recover the situation.

Boeing are not the only ones with any responsibility here.

American Airlines union: blaming pilots for Boeing 737 Max crashes 'inexcusable'
Allied Pilots Association says jetmaker’s anti-stall software forced plane into such an aggressive dive pilots could not recover

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#2244692 24-May-2019 16:15

The maximum amount of pitch-up caused by the engine geometry change was presumably well established by flight tests.

Why wasn't the MCAS system limited to being able to apply no more than that amount of nose-down trim, rather than being allowed to run away to the stops?

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#2244956 24-May-2019 20:01

dafman:

American Airlines union: blaming pilots for Boeing 737 Max crashes 'inexcusable'
Allied Pilots Association says jetmaker’s anti-stall software forced plane into such an aggressive dive pilots could not recover

There's politics at play here, plus without seeing what was actually said rather, than just reading the headlines, it's impossible to put these headlines into any context without knowing exactly what each organisation actually said. Your quotes are meaningless on their own.

To say "jetmaker’s anti-stall software forced plane into such an aggressive dive pilots could not recover" is baloney. The flight immediately prior to the fatal Lion air crash was recovered from exactly the same situation. The question that should be being asked in this case is, How was the aircraft despatched without the MCAS fault being repaired? By the way it's not anti stall software either.

I'm not sure anyone with any proper industry experience has heaped all the blame on the pilots, that would be inexcusable. Likewise all the blame cannot be heaped onto Boeing like some people have tried to do, that is inexcusable too.

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#2244960 24-May-2019 20:09

DonH:

The maximum amount of pitch-up caused by the engine geometry change was presumably well established by flight tests.

Why wasn't the MCAS system limited to being able to apply no more than that amount of nose-down trim, rather than being allowed to run away to the stops?

The MCAS was designed to limit the amount of nose down trim it. However every time the electric trim switches on the control column were activated the MCAS was "reset" and would drive again for the prescribed time, assuming the inputs that triggered the MCAS were still present.

I'm not sure about this point but it's also possible the MCAS would drive trim again anyway, if the situation it was designed to correct was still present, which was effectively the case with the faulty AoA sensor inputs.

Either way correct application of the Boeing procedures would have allowed them to regain control. The correct procedures weren't followed.

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#2247056 28-May-2019 13:57

Technofreak:

... However every time the electric trim switches on the control column were activated the MCAS was "reset" and would drive again for the prescribed time, assuming the inputs that triggered the MCAS were still present

...

I don't see that as a valid condition. MCAS had one job - to compensate for increased AoA under certain conditions, thus making the aircraft feel similar to previous versions. It was not a general anti-stall or AoA correction system. It should have assumed that if the AoA was still excessive after MCAS activation it was either deliberate or, at the least, the pilot's problem to solve.

People hear what they see. - Doris Day

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#2247220 28-May-2019 15:49

DonH:

I don't see that as a valid condition. MCAS had one job - to compensate for increased AoA under certain conditions, thus making the aircraft feel similar to previous versions. It was not a general anti-stall or AoA correction system. It should have assumed that if the AoA was still excessive after MCAS activation it was either deliberate or, at the least, the pilot's problem to solve.

I'm not an aircraft designer nor do I suspect you are either. So I cannot see how either of us can determine whether or not it was a valid condition.

The MCAS wasn't to compensate for increased AoA, it was there to compensate for what happened at high AoA, the same AoA that other models operated at at certain stages of flight.

Using AoA as the trigger, MCAS was designed to mimic the same elevator control forces as previous models. At high angles of attack the position of the engines and the airflow over the engine nacelles created a pitching up moment making the elevator up forces lighter than other models (in fact making control forces lighter when they would normally be getting heavier), thus making it easier to over pitch the nose of the aircraft. The pitching up moment also didn't comply with design rules.

In your original post you asked this question;

Why wasn't the MCAS system limited to being able to apply no more than that amount of nose-down trim, rather than being allowed to run away to the stops?

My answer was that's exactly what the MCAS was designed to do, apply only a predetermined amount of nose down trim.

Why it was reset by activation of the trim? I don't know, but I'd guess there was a very good reason why the designers made it work this way. The fact MCAS was reset by trim activation wasn't the sole reason these aircraft crashed. In my opinion it is one small factor that may have contributed.

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#2247242 28-May-2019 16:18

Technofreak:

...

Why it was reset by activation of the trim? I don't know, but I'd guess there was a very good reason why the designers made it work this way. The fact MCAS was reset by trim activation wasn't the sole reason these aircraft crashed. In my opinion it is one small factor that may have contributed.

True, I'm not an aeronautics engineer. Nor do I play one on TV.

We differ in our opinion of its (MCAS) contribution to the crashes. I see the intention of MCAS being to provide intuitive behaviour, but the repeated application of trim resulted in non-intuitive behaviour of the aircraft, increasing the load on the pilots. But I'll need to re-read the relevant docs, I've arrived at the other side of the chicken vs egg view than you.

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#2247249 28-May-2019 16:34

Seeing a bit of arm-chair toward pilots vs system opinions - Not sure if it went un-noticed or just plain ignored, but the 60mins video has a pilot, in the sim. Explaining the issue in detail. And how his attempts to over-ride were ignored due the reset mentioned. Every 5 second cycle

10-on. 5 off. And one has to remember at no point where the procedural process to totally disable it given (or an alarm light to indicate it was happening) other than discovery it was less at cruise conditions.

https://youtu.be/aO7_indbfME?t=105

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#2247252 28-May-2019 16:41

Oblivian:

Seeing a bit of arm-chair toward pilots vs system opinions - Not sure if it went un-noticed or just plain ignored, but the 60mins video has a pilot, in the sim. Explaining the issue in detail. And how his attempts to over-ride were ignored due the reset mentioned. Every 5 second cycle

10-on. 5 off. And one has to remember at no point where the procedural process to totally disable it given (or an alarm light to indicate it was happening) other than discovery it was less at cruise conditions.

https://youtu.be/aO7_indbfME?t=105

There were some very dodgy segments in that 60 minutes programme. It certainly wasn't a balanced presentation of the facts,

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#2247254 28-May-2019 16:44

DonH:

True, I'm not an aeronautics engineer. Nor do I play one on TV.

We differ in our opinion of its (MCAS) contribution to the crashes. I see the intention of MCAS being to provide intuitive behaviour, but the repeated application of trim resulted in non-intuitive behaviour of the aircraft, increasing the load on the pilots. But I'll need to re-read the relevant docs, I've arrived at the other side of the chicken vs egg view than you.

I've arrived at my conclusions through my own flying experience, reading various articles and what other pilots have written about these events.

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#2247655 29-May-2019 11:40

Technofreak:
DonH:

True, I'm not an aeronautics engineer. Nor do I play one on TV.

We differ in our opinion of its (MCAS) contribution to the crashes. I see the intention of MCAS being to provide intuitive behaviour, but the repeated application of trim resulted in non-intuitive behaviour of the aircraft, increasing the load on the pilots. But I'll need to re-read the relevant docs, I've arrived at the other side of the chicken vs egg view than you.

I've arrived at my conclusions through my own flying experience, reading various articles and what other pilots have written about these events.

I've arrived at my conclusions through reading various articles, videos and what other pilots have written about these events. Personally, I hold blame against Boeing, not the pilots. Boeing are culpable in two major areas (1) by developing software designed to control a plane's flight under certain circumstances, but (initially) keeping this a secret. (2) Boeing's refusal to advise Max 8 grounding following first crash was inexcusable (as they would have been aware that MCAS was a likely contributor).

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