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The lion air pilots had 15 mins to disable the automatic trim system and simply set the trim manually. It's turning off a switch and spinning a wheel. Manually

The lion air pilots had 15 mins to disable the automatic trim system and simply set the trim manually. It's turning off a switch and spinning a wheel. Manually setting trim is second nature to student pilots. To put it bluntly only a fool is going to start flipping switches willy nilly. Boeing has a procedure out to handle runaway stabilizer trim, and that's to flip the switches, but the Lion Air pilots did not encounter a runaway stabilizer so why would they go down that checklist and potentially add to their troubles? In the case of the cutout switches, those switches do different things on the NG and MAX (and are thus labeled differently) which potentially adds to the confusion and reduces the incentive to experiment. You're talking about counteracting a system that Boeing hid from pilots — hardly pilot error. In fact if you look at the FDR data you'll see that the pilots were able to temporarily disable MCAS with the trim buttons on the yoke. Every time MCAS trimmed down, the pilot trimmed up and was able to maintain appropriate trim. That worked, and it seemed like the plane was largely under control (until it wasn't). Meanwhile the unreliable airspeed indicators were illuminated and one of the stick shakers was going off, and there was probably an EICAS message about the elevator feel system but no actual indication of the underlying problem with AoA was given because Boeing charges extra for that. So, with the assumption that you had the stabilizer trim under control, why would you add to the significant workload by disabling the electrical control of the stabilizer?

A2017U1 8y ago
> with the assumption that you had the stabilizer trim under control, why would you add to the significant workload by disabling the electrical control of the stabilizer? I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control. > the Lion Air pilots did not encounter a runaway stabilizer What did the pilots on the four previous flights encounter? Did they not follow procedure correctly by overriding it? The trim stabiliser had to be adjusted 23 times during the the fatal flight, this is a solid fact. After a few times it should have been very apparent that there was a problem related to the automatic trim system and switched to manual. Manual trim would only get adjusted a only few times during a regular flight, it's a very basic skill and the trim wheel itself takes up a huge amount of real estate in modern cockpits. Sorry but you've written a lot of terribly inaccurate stuff here. Let's see what the report says. There are dozens of design flaws in modern aircraft, a miniscule amount are unrecoverable following procedure. The process to manually override trim on a 737 that should have been followed: https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html https://www.nytimes.com/interactive/2018/11/16/world/asia/li...
- inferiorhuman 8y ago
  I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control. Every time MCAS trimmed down, the pilot trimmed up which resulted in two things: MCAS stopped trimming down, and the stabilizer was adjusted up. That's not a runaway situation. What did the pilots on the four previous flights encounter? The previous pilots ran into MCAS trimming the stabilizer down inappropriately. They wrote it up as a speed trim (STS) failure. The crew on the fatal flight read STS and was probably thinking STS when they crashed. Unlike the undocumented MCAS inputs, STS can be disabled by moving the control column. Did they not follow procedure correctly by overriding it? There was no procedure, MCAS was undocumented. Manual trim would only get adjusted a only few times during a regular flight You're almost never going to crank the trim wheels by hand but an NG pilot may be used to having to add input to counter STS. The process to manually override trim on a 737 that should have been followed: The pilots were presented with more than just uncommanded trim adjustments, they were presented with multiple, seemingly unrelated, failures. The failed AoA measurement meant they had no idea how fast they were going (new behavior on the MAX, see the repeated queries they made to the ATC), one of the stick shakers was going off (unsure if plane is going to stall and fall out of the sky), and there was probably a warning about the "elevator feel" system on EICAS like on the previous flight. When faced only with uncommanded trim, sure, they probably would've thought STS because that's the only system Boeing bothered to document. In an ideal world the pilots would've recognized that this wasn't STS. In reality the pilots were busy triaging a variety of symptoms because Boeing did not make appropriate warning / status indications standard equipment on the MAX nor did Boeing actually document that MCAS exists (except in Brazil). The only error that the Lion Air crew made was in not being clairvoyant.

A2017U1 8y ago

> with the assumption that you had the stabilizer trim under control, why would you add to the significant workload by disabling the electrical control of the stabilizer? I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control. > the Lion Air pilots did not encounter a runaway stabilizer What did the pilots on the four previous flights encounter? Did they not follow procedure correctly by overriding it? The trim stabiliser had to be adjusted 23 times during the the fatal flight, this is a solid fact. After a few times it should have been very apparent that there was a problem related to the automatic trim system and switched to manual. Manual trim would only get adjusted a only few times during a regular flight, it's a very basic skill and the trim wheel itself takes up a huge amount of real estate in modern cockpits. Sorry but you've written a lot of terribly inaccurate stuff here. Let's see what the report says. There are dozens of design flaws in modern aircraft, a miniscule amount are unrecoverable following procedure. The process to manually override trim on a 737 that should have been followed: https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html https://www.nytimes.com/interactive/2018/11/16/world/asia/li...

inferiorhuman 8y ago
I'm struggling to see how you think having to make manual adjustments every 30 seconds is "under control". Check the flight profile, it was never under control. Every time MCAS trimmed down, the pilot trimmed up which resulted in two things: MCAS stopped trimming down, and the stabilizer was adjusted up. That's not a runaway situation. What did the pilots on the four previous flights encounter? The previous pilots ran into MCAS trimming the stabilizer down inappropriately. They wrote it up as a speed trim (STS) failure. The crew on the fatal flight read STS and was probably thinking STS when they crashed. Unlike the undocumented MCAS inputs, STS can be disabled by moving the control column. Did they not follow procedure correctly by overriding it? There was no procedure, MCAS was undocumented. Manual trim would only get adjusted a only few times during a regular flight You're almost never going to crank the trim wheels by hand but an NG pilot may be used to having to add input to counter STS. The process to manually override trim on a 737 that should have been followed: The pilots were presented with more than just uncommanded trim adjustments, they were presented with multiple, seemingly unrelated, failures. The failed AoA measurement meant they had no idea how fast they were going (new behavior on the MAX, see the repeated queries they made to the ATC), one of the stick shakers was going off (unsure if plane is going to stall and fall out of the sky), and there was probably a warning about the "elevator feel" system on EICAS like on the previous flight. When faced only with uncommanded trim, sure, they probably would've thought STS because that's the only system Boeing bothered to document. In an ideal world the pilots would've recognized that this wasn't STS. In reality the pilots were busy triaging a variety of symptoms because Boeing did not make appropriate warning / status indications standard equipment on the MAX nor did Boeing actually document that MCAS exists (except in Brazil). The only error that the Lion Air crew made was in not being clairvoyant.