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Ethiopian Airlines B737 crashes

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Orbit v2

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This issue is a lot bigger than the simple fix that some posters here seem to think it is:


"Boeing will have to answer for the design flaw that is at the heart of the controversy surrounding the 737 Max in the coming weeks and months."
There's nothing new in that. It even says at the end:
It's not all gloom and doom for Boeing
The situation Boeing finds itself in is not insurmountable.
Aimer said Boeing's engineering team should be able to come up with an effective fix for the 737 Max.
Flight cancellations are one thing. The time for Boeing to worry will be when a lot of airlines start to cancel orders. Personally, I don't see that happening.
 

Nebuchadnezzar

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Your opinions are very much at odds with the expert ones in the article I linked.

I was referring to stall in relation to commercial aircraft. Of course there are military aircraft that push those limits to dangerous extremes and practice real life recovery.. I doubt you have ever had to recover a real commercial aircraft with passengers onboard from a stall.. apart from in a virtual reality simulator?

You’re ascribing special expertise to a the author of a German newspaper article. I don’t think it translates particularly well.

No, I have never had to recover from a stall in any large aircraft....it is an extremely rare event. However, as I said before commercial pilots practice this in their simulator checks as part of the mandatory referesher training. In my previous sim to last the detail included recovery from stalls with degraded flight control systems, with faults in 1 and then 2 flight control computers. Also carried out in different configurations, with clean wings and then with slats and flaps in various positions. Also carried out at high altitude and then low. Full Flight Simulators which we use for these checks model real life behaviour very accurately.
 
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artfoley56

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You ascribing special expertise to a the author of a German newspaper article. I don’t think it translates particularly well.

No, I have never had to recover from a stall in any large aircraft....it is an extremely rare event. However, as I said before commercial pilots practice this in their simulator checks as part of the mandatory referesher training. In my previous sim to last the detail included recovery from a stall with degraded flight control systems, with faults in 1 and then 2 flight control computers. Also carried out in different configurations, with clean wings and then with slats and flaps in various positions. Also carried out at high altitude and then low. Full Flight Simulators which we use for these checks model real life behaviour very accurately.
would be interesting if they started adding MCAS type situations to the sims without telling the pilots
 

Nebuchadnezzar

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would be interesting if they started adding MCAS type situations to the sims without telling the pilots
If simulator training had covered MCAS I think these incidents would probably not have happened.
 

artfoley56

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If simulator training had covered MCAS I think these incidents would probably not have happened.
I absolutely agree with you, however, if the pilots in the sim faced the same conditions as the lion and Ethiopian pilots (i.e, lack of knowledge of the MCAS), I wonder then what the pass rate would be?
 

riven

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I absolutely agree with you, however, if the pilots in the sim faced the same conditions as the lion and Ethiopian pilots (i.e, lack of knowledge of the MCAS), I wonder then what the pass rate would be?
Indeed. typically you would say that operator action is 0.1 i.e. a mistake one every ten years, as they are following procedures and well trained. Airline pilots are exceptionally well trained and there is a double check between captain and co pilot. So taking a higher number could be justified though 0.01 is quite difficult to attain.

However this assumes good training. And there is clearly a training question here, and this just makes my calculation worse.
 

cozzy121

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If simulator training had covered MCAS I think these incidents would probably not have happened.
Jesus wept

The pilots of Ethiopia Airlines Flight 302 apparently followed the proper steps to shut down an errant flight control system as they struggled to regain control of the 737 MAX aircraft shortly after takeoff. But according to multiple reports, data from the ill-fated aircraft’s flight recorder revealed that the anti-stall feature of the aircraft’s Maneuvering Characteristics Augmentation System (MCAS) was triggered at least three times—and at least one time after the pilots followed the correct steps to shut it down.

The data showed that shortly after liftoff, a crucial sensor that measures the angle that the plane is moving through the air, began fluctuating wildly on the pilot’s side, falsely indicating that the plane was close to stalling. The sensor, one of two sensors on the plane’s nose, began giving readings nearly 60 degrees different from that of its counterpart. About a minute and a half after takeoff, after the pilots had performed routine tasks like retracting flaps on the wings, the false reading appears to have set off an automated system known as MCAS, the black box data shows. MCAS is intended to prevent a stall and began rapidly pushing the nose of the craft down.
The pilots countered that by pushing electrical switches on their control wheels that adjusted the angle of stabilizers on the tail of the plane, which had been moved by MCAS. About five seconds after the pilots tried the right the plane, MCAS again engaged, moving the stabilizers to a dangerous angle in another nose-down action.
The pilots pushed the electrical switches again. Then, the report says, they followed the emergency checklist and disabled the entire stabilizer electrical system using the so-called stabilizer trim cutout.
“The first officer called out ‘stab trim cutout’ two times,” the report says. “Captain agreed and first officer confirmed stab trim cutout.”
Although that move disabled MCAS, it also forced the crew to control the stabilizers manually with wheels at their feet — a physically difficult task on a plane moving at high speed. A little under four minutes after takeoff, the first officer said the manual method “is not working.”
Soon after, the black box data indicates, the crew turned electricity back on and tried two more times to move the stabilizers by hitting the switches. But once they turned the electricity back on, MCAS engaged again, putting the plane into a dive from which it would not recover.
They followed their training, but because a computer programme relying on detective information had been given authority to override the input from the pilots control sticks, they hadn't a hope.
 
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Nebuchadnezzar

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Jesus wept






They followed their training, but because a computer programme relying on detective information had been given authority to override the input from the pilots control sticks, they hadn't a hope.

Jesus wept what? They did not have any training on MCAS.

That they carried out the correct proceedure is only part of the picture. The aircraft accelerated in level flight with full power up to or beyond its max design airspeed, 350knots. At that airspeed with the stabiliser trimmed down the aerodynamic load on the tailplane made it very difficult to manually pitch the aircraft back up. This crew were understandably overloaded by a situation to which they had no prior simulator experience of. They had read and absorbed the technical update but it seems that in whilst they had carried out the proceedure correctly they, by failing to reduce power and control the airspeed, that they failed to maintain proper control of the aircraft.

So I’ll say it again. If this crew had carried out sim training covering MCAS they probably would not have crashed. Reading a technical bulletin is not adequate. Practical experience in a simulator would have been far better.
 

artfoley56

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Jesus wept what? They did not have any training on MCAS.

That they carried out the correct proceedure is only part of the picture. The aircraft accelerated in level flight with full power up to or beyond its max design airspeed, 350knots. At that airspeed with the stabiliser trimmed down the aerodynamic load on the tailplane made it very difficult to manually pitch the aircraft back up. This crew were understandably overloaded by a situation to which they had no prior simulator experience of. They had read and absorbed the technical update but it seems that in whilst they had carried out the proceedure correctly they, by failing to reduce power and control the airspeed, that they failed to maintain proper control of the aircraft.

So I’ll say it again. If this crew had carried out sim training covering MCAS they probably would not have crashed. Reading a technical bulletin is not adequate. Practical experience in a simulator would have been far better.
but surely the blame is on boeing there for saying that the technical bulletin would be the big fix after lion air. surely they should have suggested sim time ?
 

Nebuchadnezzar

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but surely the blame is on boeing there for saying that the technical bulletin would be the big fix after lion air. surely they should have suggested sim time ?
Yes, I think the main fault lies with Boeing.

I am assuming that Ethiopian didn’t on their own initiative introduce MCAS into their simulator sessions since the Lion Air crash. I haven’t read anywhere that they did. I wonder if any airlines covered MCAS as part of their training program since Lion Air.
 

Pabilito

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Full Flight Simulators which we use for these checks model real life behaviour very accurately.
If simulator training had covered MCAS I think these incidents would probably not have happened.

You’re contradicting yourself there… “Real life behaviour” was a MCAS nose dive whereas the simulator didn’t even know about the existence of MCAS.... yet you still insist that the simulator models real life behaviour very accurately?
 

Nebuchadnezzar

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You’re contradicting yourself there… “Real life behaviour” was a MCAS nose dive whereas the simulator didn’t even know about the existence of MCAS.... yet you still insist that the simulator models real life behaviour very accurately?
My post was response to you questioning the value of simulator practice of recovery from stalls. Full Flight Simulators match the handling characteristics of the aircraft very accurately. Stalls are not “almost always catastrophic”.....in fact the opposite is the case....stalls in themselves are generally not catastrophic. The fact that several of the disasters that have occurred over the past number of years involved stalls is not the point....these stalls were secondary effects of other conditions.

MCAS doesn’t affect the handling characteristics of the aircraft....it is just software which acts through the existing flight control computers and subject to the existing flight control laws. It has no effect upon the aerodynamics of the aircraft. The repositioning and different size, shape and power of the new engines does. MCAS makes a control input to the tailplane....that same control input can be made by auto trim or manually by the pilots. The response of the aircraft or simulator to that same control input would be exactly the same regardless of the source of that control input.
 
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Orbit v2

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Isn't it the case as well that the simulators mostly haven't been updated for the MAX? If the plane was supposed to have the same flight characteristics as the NG, maybe there was a reluctance to invest in that.. A question on that point. Is a simulator for the MAX a completely new machine or do you have a generic 737 simulator that can be configured to operate like different versions? From a software point of view, that is clearly feasible but there are differences in cockpit layout - therefore, hardware differences that might be hard to simulate. Even the Max has some small differences I understand ...
 

Nebuchadnezzar

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Isn't it the case as well that the simulators mostly haven't been updated for the MAX? If the plane was supposed to have the same flight characteristics as the NG, maybe there was a reluctance to invest in that.. A question on that point. Is a simulator for the MAX a completely new machine or do you have a generic 737 simulator that can be configured to operate like different versions? From a software point of view, that is clearly feasible but there are differences in cockpit layout - therefore, hardware differences that might be hard to simulate. Even the Max has some small differences I understand ...
I am not sure about that. I know that with the Airbus A320 family the same simulator can be used for the classic A320 or the NEO variants. All that is required is a change over of sofware.
 

Pabilito

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My post was response to you questioning the value of simulator practice of recovery from stalls. Full Flight Simulators match the handling characteristics of the aircraft very accurately. Stalls are not “almost always catastrophic”.....in fact the opposite is the case....stalls in themselves are generally not catastrophic. The fact that several of the disasters that have occurred over the past number of years involved stalls is not the point....these stalls were secondary effects of other conditions.
A stall shortly after take off would most likely be catastrophic with no altitude to recover, do you disagree?

MCAS doesn’t affect the handling characteristics of the aircraft....it is just software which acts through the existing flight control computers and subject to the existing flight control laws. It has no effect upon the aerodynamics of the aircraft. The repositioning and different size, shape and power of the new engines does. MCAS makes a control input to the tailplane....that same control input can be made by auto trim or manually by the pilots. The response of the aircraft or simulator to that same control input would be exactly the same regardless of the source of that control input.
I know all that but you’re missing my point.. I was trying to point out that simulators only know what they are programmed to know about the real life system they are simulating..

They don’t possess any awareness of their own internal limitations nor do they know about the bugs and design flaws within the target real life system they are simulating. They are fundamentally limited to simulating just the typical day to day circumstances that they were programmed to be aware of … certainly not the exceptional coincidental circumstances that have tended to lead to accidents.. Simulators are every bit as susceptible to error as aircraft are.
 

Orbit v2

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A stall shortly after take off would most likely be catastrophic with no altitude to recover, do you disagree?
I would say a stall straight after take off is unlikely, unless caused by engine failure. It's more likely to happen after a period of stable flight when something happens which pilots don't notice and which causes a gradual loss of airspeed or change in attitude. At take-off, engine power, plane attitude, control positions tend to be at well known positions and pilots are concentrating on maintaining this.
I know all that but you’re missing my point.. I was trying to point out that simulators only know what they are programmed to know about the real life system they are simulating..

They don’t possess any awareness of their own internal limitations nor do they know about the bugs and design flaws within the target real life system they are simulating. They are fundamentally limited to simulating just the typical day to day circumstances that they were programmed to be aware of … certainly not the exceptional coincidental circumstances that have tended to lead to accidents.. Simulators are every bit as susceptible to error as aircraft are.
That's not true at all. Simulators have often been used to diagnose the cause of accidents.
 

cozzy121

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Looks like the FAA is doubling down in their backing of the 737max

Wonder if other Aviation agencies in Europe or China will disagree?


review by a U.S. Federal Aviation Administration panel into Boeing Co’s grounded 737 MAX aircraft found a planned software update and training revisions to be “operationally suitable,” the agency said Tuesday, an important milestone in getting the planes back in the air.....
The draft report from the Flight Standardization Board (FSB) appointed by the FAA, which includes pilots, engineers and other experts, said additional training was needed for MCAS, but not required to be done in a simulator. The board said ground training “must address system description, functionality, associated failure conditions, and flight crew alerting.” The public has until April 30 to make comments.
The panel evaluated the software update to MCAS for “training and checking differences determination,” the report said. “The MCAS system was found to be operationally suitable.”
 

Nebuchadnezzar

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A stall shortly after take off would most likely be catastrophic with no altitude to recover, do you disagree?



I know all that but you’re missing my point.. I was trying to point out that simulators only know what they are programmed to know about the real life system they are simulating..

They don’t possess any awareness of their own internal limitations nor do they know about the bugs and design flaws within the target real life system they are simulating. They are fundamentally limited to simulating just the typical day to day circumstances that they were programmed to be aware of … certainly not the exceptional coincidental circumstances that have tended to lead to accidents.. Simulators are every bit as susceptible to error as aircraft are.
It depends on a range of factors. However, even in that scenario it’s not necessarily catastrophic but it certainly is more critical than at higher altitudes. Landing and approach is probablably the highest risk....with engine power low and the aircraft already descending....for example Turkish Airlines crash at Amsterdam, flight 1951.

My point is that simulators do model the handling of the aircraft acurately except in extreme cases(not typical stalls) where the ‘aircraft’ is well outside the flight envelope.....eg AF447 once it had entered its deep stall condition. I tried to recover from the this condition in the simulator and the ‘aircraft’ did not behave as I believe it would have in reality. In these extreme cases the simulator does not model reality well.

Also, MCAS behaved as designed. As far as we know the crash was not caused by a problem in the software.
 
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Nebuchadnezzar

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Looks like the FAA is doubling down in their backing of the 737max

Wonder if other Aviation agencies in Europe or China will disagree?

The Canadians disagree, Transport Minister....

It's not going to be a question of pulling out an iPad and spending an hour on it," he said. "Simulators are the very best way, from a training point of view, to go over exactly what could happen in a real way and to react properly to it.
Canada transport minister wants simulator training for 737 MAX fix
 

Pabilito

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My point is that simulators do model the handling of the aircraft except in extreme cases(not typical stalls) where the ‘aircraft’ is well outside the flight envelope.....eg AF447 once it had entered its deep stall condition. I tried to recover from the this condition in the simulator and the ‘aircraft’ did not behave as I believe it would have in reality. In these extreme cases the simulator does not model reality well.
It seems we are making more or less the same point that simulators can model aircraft behaviour within the normal range of expected circumstances or flight envelope as you describe it, however they can’t really be relied on outside of that. There are far too many variable factors at play in extreme chaotic accident situations for a computerised model to predict an outcome with any degree of certainty.

Where we appear to disagree is whether the MAX airframe is an inherently flawed one and if it should be allowed to fly again.

Also, MCAS behaved as designed. As far as we know the crash was not caused by a problem in the software.
While the MCAS may have operated as designed, it’s functional spec and implementation were obviously the work of amateur engineers which in my opinion warrants a separate investigation apart from the main accident investigation .
 
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