Ethiopian 737 MAX 8 crash
03-17-2019, 06:37 AM
#281
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Originally Posted by F4E Mx
Why does the MAX aircraft need a stick shaker and this new system?
03-17-2019, 06:46 AM
#282
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Posts: 96
Originally Posted by sailingfun
The system is designed to help bring the nose down in a stall. The stickshaker should in theory keep you from ever getting into that situation.
03-17-2019, 07:25 AM
#283
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Originally Posted by sailingfun
The system is designed to help bring the nose down in a stall. The stickshaker should in theory keep you from ever getting into that situation.
03-17-2019, 07:29 AM
#284
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Originally Posted by F4E Mx
Why does the MAX aircraft need a stick shaker and this new system?
Boeing wanted to make the MAX more fuel efficient. The more efficient engines are bigger, and don't fit under the 737 wing. They had to move the engines somewhat further towards the nose, to provide enough clearance. This new engine position disrupts the CG of the aircraft.
The engineers decided that the new CG could make it difficult to recover from a stall, so they added this system to automatically pitch the plane down when it sensed a stall...unfortunately the system is only connected to one of the AOA sensors, instead of both. And the pilots cannot override the software with the flight controls...their only choice is to cut off the power, and if they do it too late, the stabilizer could be moved too far for the pilots to recover.
03-17-2019, 08:36 AM
#285
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Cliff,
Two points:
1: it's not a CofG thing. It's as 1W2A said: higher AoAs lead to a forward shift in the center of pressure, due to the position of the nacelles.
2: Once power to the pitch trim is cutoff using the pedestal switches, one merely reverts to manual trim using the big-ass trim wheel. In theory, that's the end of the problem.
See the attached link, which I found to be informative:
737 MAX - MCAS
Matt
Two points:
1: it's not a CofG thing. It's as 1W2A said: higher AoAs lead to a forward shift in the center of pressure, due to the position of the nacelles.
2: Once power to the pitch trim is cutoff using the pedestal switches, one merely reverts to manual trim using the big-ass trim wheel. In theory, that's the end of the problem.
See the attached link, which I found to be informative:
737 MAX - MCAS
Matt
03-17-2019, 08:36 AM
#286
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Joined APC: Feb 2008
Posts: 19,273
Originally Posted by atpcliff
From below is what I understand, from what I have read:
Boeing wanted to make the MAX more fuel efficient. The more efficient engines are bigger, and don't fit under the 737 wing. They had to move the engines somewhat further towards the nose, to provide enough clearance. This new engine position disrupts the CG of the aircraft.
The engineers decided that the new CG could make it difficult to recover from a stall, so they added this system to automatically pitch the plane down when it sensed a stall...unfortunately the system is only connected to one of the AOA sensors, instead of both. And the pilots cannot override the software with the flight controls...their only choice is to cut off the power, and if they do it too late, the stabilizer could be moved too far for the pilots to recover.
Boeing wanted to make the MAX more fuel efficient. The more efficient engines are bigger, and don't fit under the 737 wing. They had to move the engines somewhat further towards the nose, to provide enough clearance. This new engine position disrupts the CG of the aircraft.
The engineers decided that the new CG could make it difficult to recover from a stall, so they added this system to automatically pitch the plane down when it sensed a stall...unfortunately the system is only connected to one of the AOA sensors, instead of both. And the pilots cannot override the software with the flight controls...their only choice is to cut off the power, and if they do it too late, the stabilizer could be moved too far for the pilots to recover.
03-17-2019, 11:24 AM
#287
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Posts: 281
Seems like a bigger horizontal stabilizer with a bigger elevator or maybe replace both with a stabilator would be the definitive fix. The first would be expensive, the second really expensive, but either solution would be cheaper than what is going to be spent resolving these two accidents. Saying you are going to fix the problem by wiring in another AOA indicator and adding some more software just seems unacceptable.
When Beech was developing the King Air series throughout the years the FAA required three separate Type Certificates as the models grew and became more complex. Maybe the MAX needs to start from scratch.
When Beech was developing the King Air series throughout the years the FAA required three separate Type Certificates as the models grew and became more complex. Maybe the MAX needs to start from scratch.
03-17-2019, 11:52 AM
#288
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Posts: 2,159
Would it be logical to have the 737 max series jets flown as a separate type? Another words, pilots perhaps shouldn't cross-pollenate across the various series of B-737 aircraft. Fly the standard Guppies, or Fly the Max Guppies, but not both.
I have never been a big fan of 757 and 767 being flown as a common type. Not enough stuff in common....
I wonder why only one probe is tied to MCAS? That might be a single point of failure to a fairly critical system.
I have never been a big fan of 757 and 767 being flown as a common type. Not enough stuff in common....
I wonder why only one probe is tied to MCAS? That might be a single point of failure to a fairly critical system.
03-17-2019, 11:53 AM
#289
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Joined APC: Mar 2010
Posts: 414
Now Ethiopian Airlines have the downloads from both the CVR and the
FDR. They are looking into it and may publish the “results”: Either put the blame on Boeing and their MAX 8, or admit their pilots and or mechanics screwed up. (Or a combo)
Not sure if Boeing, the FAA and the NTSB have the data yet.
(Boeing would probably be happy to publish their innocence if indeed pilot error or bad mx caused the crash)
Something completely surprising could of course also be the cause, a bomb, a fire or a highjacking, whatever
Standing by..
FDR. They are looking into it and may publish the “results”: Either put the blame on Boeing and their MAX 8, or admit their pilots and or mechanics screwed up. (Or a combo)
Not sure if Boeing, the FAA and the NTSB have the data yet.
(Boeing would probably be happy to publish their innocence if indeed pilot error or bad mx caused the crash)
Something completely surprising could of course also be the cause, a bomb, a fire or a highjacking, whatever
Standing by..
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