Boeing 737 MAX - software wouldn't fix faulty airframe

nsaspook

Joined Aug 27, 2009
7,980
To inject , my other side of work over the years has been more military
In military jets, they are inherently unstable, without the computer, they can not be hand flown,

Look at the space shuttle, that was the same, no computer, impossible to control in the atmosphere above Mach 1 , "glide" slope of around 20 degrees, all but a crash.

Nothing inherently wrong with a software controlled plane,
OK, most military planes you have the chance of getting out,
unlike the shuttle or passenger planes,

But the idea that s/w can be just used to patch a problem it was not designed for, can just be outsourced to the cheapest bidder with minimal oversite / control , as seems to be the case in Boeing, is just crazy. ..

How did they ever get away with the redundant tubes sensors being an optional at cost extra ?
How did they get away with the optional readout to indicate that the sensors might be wrong as an optional at cost extra !!
This is a instance where a stable air-frame (This thread was based on the premise of faulty air-frame, that's been proven wrong several times) was destabilized by a horrifically badly designed software system and management decisions to limit pilot knowledge of how that system worked. The fix (runaway trim) was always just to turn off MCAS, keep MCAS off and manually trim the aircraft. The published FIX does exactly that with redundancy checks for proper sensor operation but the end result is still manual flying.
https://forum.allaboutcircuits.com/...uldnt-fix-faulty-airframe.158329/post-1398868
 
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andrewmm

Joined Feb 25, 2011
1,010
One other thign to remember,
yes the air frame of the 737 max , unlike mil aircraft , can be flown without the s/w addon
The reason the software was added was that Boeing wanted to avoid the cost of re qualifying a pilot on a new air frame, and argued to the FAA that with the s/w it flew like the original 737 . !! so no training needed, not even in the new software, or how to recognise it was the software that was a problem, or how to turn it off.

Technically, there was the information on how to turn the s/w off,
on about page 200 of the what to do in case of emergency paperwork all planes carry
( and Boeing also want to replace with a sw version )
 

nsaspook

Joined Aug 27, 2009
7,980
One other thign to remember,
yes the air frame of the 737 max , unlike mil aircraft , can be flown without the s/w addon
The reason the software was added was that Boeing wanted to avoid the cost of re qualifying a pilot on a new air frame, and argued to the FAA that with the s/w it flew like the original 737 . !! so no training needed, not even in the new software, or how to recognise it was the software that was a problem, or how to turn it off.

Technically, there was the information on how to turn the s/w off,
on about page 200 of the what to do in case of emergency paperwork all planes carry
( and Boeing also want to replace with a sw version )
Trim runaway is a mandatory memory item that existed long before MCAS that does turn the S/W off by killing the power. It's required for type certification that you do the procedures without the book. Trim runaway is what happened in both fatal cases. In the Lion air case the day before the fatal crash a crew did the Trim runaway memory item correctly, MCAS was disconnected when the trim power was cut, plane landed safely.
https://en.wikipedia.org/wiki/Lion_Air_Flight_610
Passengers recounted that the aircraft had suffered an engine problem and were told not to board it as engineers tried to fix the problem. While the aircraft was en route to Jakarta, it had problems maintaining a constant altitude, with passengers stating that it was like "a roller-coaster ride."[118] The chief executive officer of Lion Air, Edward Sirait, said the aircraft had a "technical issue" on Sunday night, but this had been addressed in accordance with maintenance manuals issued by the manufacturer. Engineers had declared that the aircraft was ready for takeoff on the morning of the accident.[119][120] Information later emerged that a third pilot was on the flight to Jakarta and told the crew to cut power to the stabilizer trim motors which fixed the problem. This method is a standard memory item in the 737 checklist.[121] Subsequently, the National Transportation Safety Committee confirmed the presence of an off-duty Boeing 737 MAX 8 qualified pilot in the cockpit but did not confirm the role of the pilot in fixing the problem, and denied that there was any recording of the previous flight in the CVR of Lion Air Flight 610.[122]
The next day a new crew didn't and they all died. A directive was issued telling pilots to keep trim power off.

The next fatal crash was a sad sequence of events that reactivated MCAS and sealed their fate.
https://en.wikipedia.org/wiki/Ethiopian_Airlines_Flight_302
Flight 302 was a scheduled international passenger flight from Addis Ababa to Nairobi. The aircraft took off from Addis Ababa at 08:38 local time (05:38 UTC) with 149 passengers and 8 crew on board.[6] One minute into the flight, the first officer, acting on the instructions of the captain, reported a "flight control" problem to the control tower. Two minutes into the flight, the plane's MCAS system activated, pitching the plane into a dive toward the ground. The pilots struggled to control it and managed to prevent the nose from diving further, but the plane continued to lose altitude. The MCAS then activated again, dropping the nose even further down. The pilots then flipped a pair of switches to disable the electrical trim tab system, which also disabled the MCAS software. However, in shutting off the electrical trim system, they also shut off their ability to trim the stabilizer into a neutral position with the electrical switch located on their yokes. The only other possible way to move the stabilizer would be by cranking the wheel by hand, but because the stabilizer was located opposite to the elevator, strong aerodynamic forces were pushing on it. As the pilots had inadvertently left the engines on full takeoff power, which caused the plane to accelerate at high speed, there was further pressure on the stabilizer. The pilots' attempts to manually crank the stabilizer back into position failed. Three minutes into the flight, with the aircraft continuing to lose altitude and accelerating beyond its safety limits, the captain instructed the first officer to request permission from air traffic control to return to the airport. Permission was granted, and the air traffic controllers diverted other approaching flights. Following instructions from air traffic control, they turned the aircraft to the east, and it rolled to the right. The right wing came to point down as the turn steepened. At 8:43, having struggled to keep the plane's nose from diving further by manually pulling the yoke, the captain asked the first officer to help him, and turned the electrical trim tab system back on in the hope that it would allow him to put the stabilizer back into neutral trim. However, in turning the trim system back on, he also reactivated the MCAS system, which pushed the nose further down. The captain and first officer attempted to raise the nose by manually pulling their yokes, but the aircraft continued to plunge toward the ground
Pilot analysis[edit]
John Cox, a former 737 pilot and pilots' union safety representative, and Chesley Sullenberger, who successfully ditched US Airways Flight 1549 in the Hudson River, both did Flight Simulator replications of Flight 302. Cox described the rapid onset of unforeseen events as a "...breeding ground for confusion and task saturation." Sullenberger commented that "Even knowing what was going to happen, I could see how crews would have run out of time and altitude before they could have solved the problems."[93] While defending the pilots' actions, Sullenberger was also highly critical of allowing someone with only 200 hours of flight experience to be first officer.[94]
 
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nsaspook

Joined Aug 27, 2009
7,980
This has nothing to do with a anti-stall system, stalls or even normal flight control characteristics. There was a yoke pull non-uniformity at the limits of control during an emergency flight maneuver the started the sad MCAS saga (to change the column force feel, not to trim the aircraft). The plane was NEVER unstable or prone to stall because if it was, the FAA would never have approved MCAS after the fixes due to the requirement of static stability on commercial aircraft. The root cause in the video of why MCAS exists is BS.
 

andrewmm

Joined Feb 25, 2011
1,010
IMHO, it was a management error,
the aim being to maximise profits over safety,
If they put safety first , having two tubes instead of one, and having the software to detect a difference would not have been at cost options, but mandatory. The FAA taking Boeings word that that was OK, and Boeing for promoting this, just to make the 737max look cheaper than the competition is IMHO criminal.
 
Thank god it did not happen mid Atlantic or similar.

They evidently failed to extinguish flames, I'd imagine the extinguisher was blown off as well as the cowling.
How long could that have burnt before it reached all the fuel in the wings.

It had just taken off, so had a lot of fuel on board,
I'm amaze they managed to land with that load on board,
must have been very near the max landing limit ,
 
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