737 grounded???

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BBerson

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Yes, I was referring to the jump seat pilot. A third pilot might not freeze up and can see what needs to happen from his perspective.
I read on Avweb yesterday they think the Flight Data Recorder is indicating a possible bad AOA sensor on the Ethiopia Air crash, same as Lion Air. Almost unbelievable. It might not be the sensor, could be a software glitch and nothing to do with the sensor.
 

markaeric

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I haven't seen schematics for the internals of an AoA sensor, but I have replaced them (heater failure), and judging by how many wires go to the connector, I'd assume it had redundant position sensors. So unless the vane breaks off, they seem pretty resilient. However, I have had to replace the computer modules they connect to because they failed, which then require a baseline calibration and a test flight for final calibration. Granted, the system could very well be different on a 737, and may integrate with the avionics more directly, but there's probably still plenty of places for things to fail, or maintenance to make errors. It still boggles my mind that Boeing thought one AoA sensor was sufficient input for an auto-trim system.
 

Himat

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basic piloting skills lost to automation (turn the trim off and hand fly the bucket)

Politics and dumb azzed pilots
Or pilots lost on system knowledge?;)

Know the system and operate it accordingly. As any computer, **** in and there is **** out.
 

davidb

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The AoA vanes on the Max look identical to the ones used on older models. AFAIK, there isn’t a history of those failing other than by obvious physical damage such as being struck by ground equipment. Bogus stick shaker is very rare, certainly not one every six months. Hopefully they will be able to determine what the AoA problem is. MCAS aside, bogus stick shaker is still a bad thing.
 

DangerZone

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I think it might be more accurate to say that the MCAS was designed to give the 737 MAX the same "feel" and trim requirements as earlier 737 models. This facilitated certification under the existing tyoe rating and also reduced crew training requirements. Without MCAS, the plane would be no more dangerous than any other 737 when hand-flying. Add power and you might need to retrim--nothing different there, just the magnitude of the trim.
Apparently the MCAS was installed because the Max 8 has more powerful engines with a nasty pitch up moment when power is added. At least that's what some experts said about the Max 8.

I haven't seen schematics for the internals of an AoA sensor, but I have replaced them (heater failure), and judging by how many wires go to the connector, I'd assume it had redundant position sensors. So unless the vane breaks off, they seem pretty resilient. However, I have had to replace the computer modules they connect to because they failed, which then require a baseline calibration and a test flight for final calibration. Granted, the system could very well be different on a 737, and may integrate with the avionics more directly, but there's probably still plenty of places for things to fail, or maintenance to make errors. It still boggles my mind that Boeing thought one AoA sensor was sufficient input for an auto-trim system.
Doesn't the Max 8 have two vanes with two sensors, one on each side?
 

davidb

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Apparently the MCAS was installed because the Max 8 has more powerful engines with a nasty pitch up moment when power is added. At least that's what some experts said about the Max 8.



Doesn't the Max 8 have two vanes with two sensors, one on each side?
We have been bombarded with plenty of sound bites and word smithing of the new features and reasons for the changes. The engines are physically bigger which necessitates their repositioning and results in some aerodynamic characteristics differences. There is no “nasty” pitch up moment when power is added in the normal flight regime. The new engines are slightly more powerful but the position and aerodynamic effects of the new position are the bigger factor.

The Max (and older models) do have two AoA vanes, one on each side. Vanes and sensors are two words for the same thing.
 

Voidhawk9

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There are two AoA vanes, but MCAS only took infomration from one of them (this is changing with the software fixes in the works), thus a fault in the vane or associated systems could lead to MCAS driving the stablizer to the full nose-down position unless the crew identified the stab trim issue and disabled it.
 

DangerZone

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We have been bombarded with plenty of sound bites and word smithing of the new features and reasons for the changes. The engines are physically bigger which necessitates their repositioning and results in some aerodynamic characteristics differences. There is no “nasty” pitch up moment when power is added in the normal flight regime. The new engines are slightly more powerful but the position and aerodynamic effects of the new position are the bigger factor.

The Max (and older models) do have two AoA vanes, one on each side. Vanes and sensors are two words for the same thing.
I thought a vane was the metal surface which deflects under the air stream loads, while the sensor was the electronic component which measures this deflection in increments?

There was a similar report to the one BJC posted, which showed that "Boeing engineers found that under certain conditions the 737 MAX's engines -- which are larger and located higher and closer to the front -- boost the chances that the aircraft would tilt upward too steeply -- causing the plane to stall".

Anyway, no matter how complex the new 737 Max 8 is, this could not be an excuse for poor flying skills. These seem to be more likely the cause than Boeing engineering or design.
 

markaeric

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If Boeing expected pilots to be able to fly the MAX with MCAS disabled in the stressful event of an emergency without requiring additional training, then maybe perhaps those pilots could also fly that plane without MCAS in a non-emergency. Seems like an unnecessary feature that bit them in the ass and is at least partially to blame for hundreds of deaths.
 

markaeric

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I thought a vane was the metal surface which deflects under the air stream loads, while the sensor was the electronic component which measures this deflection in increments?
Technically speaking, correct, but the terms might be used interchangeably to describe the AoA module which includes all those parts.
 

BJC

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Just an observation: Having taught Root Cause Analysis, plus having performed scores of root cause analyses, I have observed that most people are ready to pronounce event cause without any real, relevant data or data analysis. And, they are almost always evenly divided between those who immediately blame the people / person (pilots, in the 737 events) or the equipment / design / dumb engineers / evil management.

If anyone of us were involved in the analysis of one of the 737 crashes, it would be totally inappropriate for that person to discuss the event or post comments about it. Certainly, discussing those events here is legitimate, but readers must keep in mind that posts here are mostly speculative as to cause. Comments by HBAers with direct experience are welcomed and instructive, but they should not, without lots af additional data and data assessment, lead one to assume a root cause.


BJC
 

Vigilant1

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If Boeing expected pilots to be able to fly the MAX with MCAS disabled in the stressful event of an emergency without requiring additional training, then maybe perhaps those pilots could also fly that plane without MCAS in a non-emergency. Seems like an unnecessary feature that bit them in the ass and is at least partially to blame for hundreds of deaths.
Again: The best explanation is that MCAS did not necessarily give the MAX safer handling qualities. It was designed to give the MAX handling qualities like the older 737s so the plane didn't need to go through a clean-sheet certification process and so crews could fly it without going through a more lengthy training and checkride process. In retrospect, maybe this was a bad decision. Tens of thousands of flight here in the US and European countries with no MCAS related crashes.
Safety is very important, but it isn't the only concern. Aft facing passenger seats would becsafer, but we don't have them. A third pilot on the flight deck would improve safety. Shoulder harnesses for passengers. Bubble wrap. But low costs also contribute to safety. Even with the 737Max problems, a passenger is still over 120 times as safe, per passenger mile, on that plane yhan as a passenger in a car on a US highway. Cheap airfares encourage people to fly.
Boeing will get this fixed. Every day of delay (by Boeing or regulators) is another day of reduced availability of airline seats, additional flight cancellations, and incrementally higher prices (less supply of seats to meet demand). Every passenger who drives is at greater risk. They will just be "small" car crashes that kill or maim a few people, so they won't make headlines.
 

markaeric

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Vigilant1,

I get that, but if handling is so different, how is it reasonable to expect pilots to fly the aircraft without specific training in the event that the MCAS needs to be disabled? I'm not suggesting that the MAX has inherently unsafe flying characteristics. It just seems strange that as long as it's natural characteristics are augmented by a special system (which can fail) to make it handle like an older version avoids the need for pilots to get a new type rating, yet they would have to cope with those different handling characteristics should augmentation be disabled. I'm not arguing for or against a new type rating; I just don't see the logic behind the system when pilots might have to cope with flying the plane without it anyway.

Earlier this morning, I read a report in the Wall Street Journal that claimed the pilots of the Ethiopian crash had started following the emergency procedures to the point where they disabled electric trim and begun manually retrimming (don't know how much), then stopped following the procedures, re-enabled electric trim which led to further runaway.
 

Arthur Brown

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If only a thousand people die on the roads today it's a good day for the insurance companies, but the media will always make a months news out of 1000 deaths in the air even once every ten years!

However IMO the issue is that pilots with too much simulator time and too few type ratings in a career were let down by calling a 737-nnn MAX just a 737 for ease and cheapness. Somewhere in their career most pilots will get an "instruments don't match" sim simulating a blocked pitot tube or the like. Somewhere soon there needs to be a "The computer has just lost it" sim
 

bmcj

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Your point on jack screw loading was not lost on me, and I suspect that most of the members here understood what you were saying.
 
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