Another (2nd) 737 Max 8 crash

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#2232614 8-May-2019 07:49

Dingbatt: Except the fact that MCAS is to remedy a dynamic problem caused by differently positioned engines compared to previous versions. Ballast will only fix a static load problem to adjust the balance of the aircraft. Normally only used in smaller commuter aircraft as a last resort.

Imagine having a car that always pulls to the left, as part of the design. Software corrects that. You need to hope the software never fails, and if it did, you werent in a precarious position next to the white line at high speed, etc. An aircraft runs in a 3D environment, massively more problem situations if it failed

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#2232659 8-May-2019 09:05

tdgeek:
Dingbatt: Except the fact that MCAS is to remedy a dynamic problem caused by differently positioned engines compared to previous versions. Ballast will only fix a static load problem to adjust the balance of the aircraft. Normally only used in smaller commuter aircraft as a last resort.

Imagine having a car that always pulls to the left, as part of the design. Software corrects that. You need to hope the software never fails, and if it did, you werent in a precarious position next to the white line at high speed, etc. An aircraft runs in a 3D environment, massively more problem situations if it failed

Not quite sure why you quoted me in your post, because it seems unrelated.
However, the example you state is more akin to modern fighter aircraft which are designed to be aerodynamically unstable to improve manoeuvrability and kept stable by computers and fly-by-wire technology.

If you take your analogy and link it to my post, then you would fix the car’s steering fault by making a static adjustment. Either get a wheel alignment, or chuck a bag of sand (ballast) in one of the passenger seats (in the case you use, the rear right seat).

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#2232665 8-May-2019 09:13

Dingbatt:
tdgeek:

Dingbatt: Except the fact that MCAS is to remedy a dynamic problem caused by differently positioned engines compared to previous versions. Ballast will only fix a static load problem to adjust the balance of the aircraft. Normally only used in smaller commuter aircraft as a last resort.

Imagine having a car that always pulls to the left, as part of the design. Software corrects that. You need to hope the software never fails, and if it did, you werent in a precarious position next to the white line at high speed, etc. An aircraft runs in a 3D environment, massively more problem situations if it failed

Not quite sure why you quoted me in your post, because it seems unrelated.
However, the example you state is more akin to modern fighter aircraft which are designed to be aerodynamically unstable to improve manoeuvrability and kept stable by computers and fly-by-wire technology.

If you take your analogy and link it to my post, then you would fix the car’s steering fault by making a static adjustment. Either get a wheel alignment, or chuck a bag of sand (ballast) in one of the passenger seats (in the case you use, the rear right seat).

Yes, that was my point. The 737MAX has a designed and known balance flaw, compensated by software. Why did they not counter that with ballast or moving fuselage fuel tanks, or anything to get it back in balance? They didnt. Money.

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#2232682 8-May-2019 09:41

tdgeek:

Yes, that was my point. The 737MAX has a designed and known balance flaw, compensated by software. Why did they not counter that with ballast or moving fuselage fuel tanks, or anything to get it back in balance? They didnt. Money.

I don't think that's quite correct. I think the plane is still "balanced" in terms of static weight distribution, the issue is that under high thrust, the re-positioned engines can tend to lift the nose, risking a stall. So this couldn't be corrected by shifting weight, as that would probably make it nose heavy under low thrust.

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#2232688 8-May-2019 09:57

Fred99:

tdgeek:

Yes, that was my point. The 737MAX has a designed and known balance flaw, compensated by software. Why did they not counter that with ballast or moving fuselage fuel tanks, or anything to get it back in balance? They didnt. Money.

I don't think that's quite correct. I think the plane is still "balanced" in terms of static weight distribution, the issue is that under high thrust, the re-positioned engines can tend to lift the nose, risking a stall. So this couldn't be corrected by shifting weight, as that would probably make it nose heavy under low thrust.

Ah, thanks for that.

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#2232973 8-May-2019 13:36

tdgeek:

Fred99:

tdgeek:

Yes, that was my point. The 737MAX has a designed and known balance flaw, compensated by software. Why did they not counter that with ballast or moving fuselage fuel tanks, or anything to get it back in balance? They didnt. Money.

I don't think that's quite correct. I think the plane is still "balanced" in terms of static weight distribution, the issue is that under high thrust, the re-positioned engines can tend to lift the nose, risking a stall. So this couldn't be corrected by shifting weight, as that would probably make it nose heavy under low thrust.

Ah, thanks for that.

Correcting with fuel tank positioning is fine, up to the point where you actually use that fuel, at which point the aircraft becomes progressively more unstable. This is why aircraft tend to have fuel tanks close to the CofG.

Adjusting the thrustline of the engines downward would correct the problem.

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#2233351 8-May-2019 21:46

frankv:

Adjusting the thrustline of the engines downward would correct the problem.

That's not an option either as the thrustline needs to be at the optimum for cruise flight or there-a-bouts.

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#2238650 15-May-2019 21:32

kingdragonfly: Rogue Boeing 737 Max planes ‘with minds of their own’
60 Minutes Australia

"Liz Hayes investigates the disaster of Boeing’s 737 MAX jetliner. Why two supposedly state-of-the-art and safe planes crashed killing 346 people; why pilots now fear flying the 737 MAX; & whether Boeing could have averted the catastrophes."

I had a look at this documentary today, I didn't watch all of but I also read comments on an aviation site from some who had watched the whole thing. I saw enough to realise it wasn't going to be a balanced presentation of the facts and decided not to waste my time watching the whole thing.

From what I did watch I couldn't help thinking the producers had decided which side of the story they wanted to tell before they started making the documentary. Some of it was quite good apparently but there are some glaring deceitful anomalies.

In the bit I watched there was no mention of the Cut Out switches and how they should have been used to stop the trim operating automatically. The audience were left thinking there was no way of over coming the trim system.

I didn't see this but apparently the pilot in the video "fumbled" his way through the QRH to find the procedures for a faulty trim. These procedures are "memory items" a pilot shouldn't have to thumb through the QRH to know what to do, and nor would any competent pilot do so.

To portray that the trim can take control of the aircraft and cannot be over ridden and that fumbling through the QRH as being the norm is down right deceitful.

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#2238738 16-May-2019 06:59

From http://flash.avweb.com/eletter/4337-full.html

An old-school technique tested by a U.S. flight crew in a 737 simulator might have helped the Lion Air and Ethiopian Airline crews had they known about it. Colloquially referred to as the “roller coaster,” the procedure requires the aircraft experiencing an out-of-trim condition to descend with reduced elevator input so that the horizontal stabilizer (used as pitch trim in the 737) could be “unloaded” enough to be manually adjusted. Then elevator inputs are resumed to arrest or slow the descent, and the procedure repeated until the aircraft is back in trim.

As reported by Aviation Week, the simulator crews set up the accident scenario from the Ethiopian Airlines flight and were able to demonstrate that despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually without this special procedure. “Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn,” said the report.

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#2238740 16-May-2019 07:13

frankv: From http://flash.avweb.com/eletter/4337-full.html
An old-school technique tested by a U.S. flight crew in a 737 simulator might have helped the Lion Air and Ethiopian Airline crews had they known about it. Colloquially referred to as the “roller coaster,” the procedure requires the aircraft experiencing an out-of-trim condition to descend with reduced elevator input so that the horizontal stabilizer (used as pitch trim in the 737) could be “unloaded” enough to be manually adjusted. Then elevator inputs are resumed to arrest or slow the descent, and the procedure repeated until the aircraft is back in trim. As reported by Aviation Week, the simulator crews set up the accident scenario from the Ethiopian Airlines flight and were able to demonstrate that despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually without this special procedure. “Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn,” said the report.

My understanding is that they were unable to recover in the simulator due to the fact the aircraft was significantly overspeed which is something we know from the early days of the investigation. Had they not been flying so fast recovery would have been a lot easier.

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#2238741 16-May-2019 07:14

Technofreak:

kingdragonfly: Rogue Boeing 737 Max planes ‘with minds of their own’
60 Minutes Australia

"Liz Hayes investigates the disaster of Boeing’s 737 MAX jetliner. Why two supposedly state-of-the-art and safe planes crashed killing 346 people; why pilots now fear flying the 737 MAX; & whether Boeing could have averted the catastrophes."

I had a look at this documentary today, I didn't watch all of but I also read comments on an aviation site from some who had watched the whole thing. I saw enough to realise it wasn't going to be a balanced presentation of the facts and decided not to waste my time watching the whole thing.

I watched 2/3 of it then turned it off. It was not a balanced documentary.

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#2238820 16-May-2019 09:55

sbiddle:

frankv: From http://flash.avweb.com/eletter/4337-full.html
An old-school technique tested by a U.S. flight crew in a 737 simulator might have helped the Lion Air and Ethiopian Airline crews had they known about it. Colloquially referred to as the “roller coaster,” the procedure requires the aircraft experiencing an out-of-trim condition to descend with reduced elevator input so that the horizontal stabilizer (used as pitch trim in the 737) could be “unloaded” enough to be manually adjusted. Then elevator inputs are resumed to arrest or slow the descent, and the procedure repeated until the aircraft is back in trim. As reported by Aviation Week, the simulator crews set up the accident scenario from the Ethiopian Airlines flight and were able to demonstrate that despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually without this special procedure. “Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn,” said the report.

My understanding is that they were unable to recover in the simulator due to the fact the aircraft was significantly overspeed which is something we know from the early days of the investigation. Had they not been flying so fast recovery would have been a lot easier.

Right. But, of course, the reason they were overspeed was the excessive nose-down trim due to MCAS.

For me, the key thing is: "despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually".

So, even if the Ethiopian airlines crew had followed the new procedures, they still wouldn't have been able to recover. i.e. the new procedures were inadequate, and should have included the "roller coaster" process. And I'll speculate that the reason the Ethiopian crew stopped following the published procedures was because they recognised that they weren't workable.

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#2238832 16-May-2019 10:06

frankv:

sbiddle:

frankv: From http://flash.avweb.com/eletter/4337-full.html
An old-school technique tested by a U.S. flight crew in a 737 simulator might have helped the Lion Air and Ethiopian Airline crews had they known about it. Colloquially referred to as the “roller coaster,” the procedure requires the aircraft experiencing an out-of-trim condition to descend with reduced elevator input so that the horizontal stabilizer (used as pitch trim in the 737) could be “unloaded” enough to be manually adjusted. Then elevator inputs are resumed to arrest or slow the descent, and the procedure repeated until the aircraft is back in trim. As reported by Aviation Week, the simulator crews set up the accident scenario from the Ethiopian Airlines flight and were able to demonstrate that despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually without this special procedure. “Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn,” said the report.

My understanding is that they were unable to recover in the simulator due to the fact the aircraft was significantly overspeed which is something we know from the early days of the investigation. Had they not been flying so fast recovery would have been a lot easier.

Right. But, of course, the reason they were overspeed was the excessive nose-down trim due to MCAS.

Incorrect. The reason they were overspeed was because they were still at takeoff thrust. The official report does not give a reason for this, but to quote one media article

The engines remained at full take-off power as the airline’s youngest-ever but highly-experienced captain, a 29-year-old with 8,122 hours of flying time, and his 25-year-old co-pilot, with 361 hours, flew the aircraft out of its initial climb.

That would be an unusual step in a regular flight, according to the experts and five current and former pilots interviewed by Reuters, most of whom were not authorized to speak publicly. “You would never, ever have full power for the whole flight,” said Hart Langer, a veteran former senior vice president for flight operations at United Airlines.

The reason the engines continued at full take-off power was not given in the report. But it is not part of a usual procedure for pilots dealing with the loss of key information such as the sensor data, the four experts said.

The Ethiopian Airlines statement suggested the crew left the throttles at take-off power because they intended to continue to climb and were hampered by the nose-down commands of MCAS.

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#2238913 16-May-2019 10:45

frankv:

sbiddle:

frankv: From http://flash.avweb.com/eletter/4337-full.html
An old-school technique tested by a U.S. flight crew in a 737 simulator might have helped the Lion Air and Ethiopian Airline crews had they known about it. Colloquially referred to as the “roller coaster,” the procedure requires the aircraft experiencing an out-of-trim condition to descend with reduced elevator input so that the horizontal stabilizer (used as pitch trim in the 737) could be “unloaded” enough to be manually adjusted. Then elevator inputs are resumed to arrest or slow the descent, and the procedure repeated until the aircraft is back in trim. As reported by Aviation Week, the simulator crews set up the accident scenario from the Ethiopian Airlines flight and were able to demonstrate that despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually without this special procedure. “Keeping the aircraft level required significant aft-column pressure by the captain, and aerodynamic forces prevented the first officer from moving the trim wheel a full turn,” said the report.

My understanding is that they were unable to recover in the simulator due to the fact the aircraft was significantly overspeed which is something we know from the early days of the investigation. Had they not been flying so fast recovery would have been a lot easier.

Right. But, of course, the reason they were overspeed was the excessive nose-down trim due to MCAS.

For me, the key thing is: "despite following procedures in place after the Lion Air crash, they were unable to add enough nose-up trim manually".

So, even if the Ethiopian airlines crew had followed the new procedures, they still wouldn't have been able to recover. i.e. the new procedures were inadequate, and should have included the "roller coaster" process. And I'll speculate that the reason the Ethiopian crew stopped following the published procedures was because they recognised that they weren't workable.

I don't think the procedures were exactly new, just a re-emphasis of existing procedures. The procedures were entirely workable. The Ethiopian pilots didn't follow the procedures in place after the Lion Air crash correctly nor other procedures for misleading speed information.

Leaving take off thrust set was one of the main factors for the aircraft to overspeed which in turn made it much more difficult to make manual trim changes.

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#2240867 19-May-2019 17:31

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."

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