5 ms·

Do you have something I can read on that "may"? I don't disagree that the throttles weren't moved, but the part about it maybe having saved them is new informat

Do you have something I can read on that "may"? I don't disagree that the throttles weren't moved, but the part about it maybe having saved them is new information.

sokoloff 7y ago
I'll give you the short explanation and then an article reference supporting. That might give you other terms to further research. The trim is driven by a jackscrew. That jackscrew is driven by a mechanism in the cockpit (a large double wheel near each flight crew station). At low and moderate airspeeds, the jackscrew turns relatively easily. At high airspeeds and low elevator deflections (meaning "when the aircraft is approximately in trim"), the jackscrew turns relatively easily. At high airspeeds and high elevator deflections, the forces on the tail make the jackscrew difficult to turn due heavy forces. This would be the case where the aircraft is trimmed heavily nose down and the crew is holding large amounts of up elevator to compensate. (You're basically cranking the tail into a different position against the air loads on it.) Slowing the airplane down would almost surely have helped the crew by reducing these loads. If you're going too fast (information the crew had available to them both in cockpit and confirmed by radio after they inquired while fighting), 94% N1 is not where you want the engines set. It's not a popular or comfortable position to look into the actions of the crew and find areas for improvement in light of the fact that they were dealt a very difficult situation that morning. Even with that, it appears that they correctly diagnosed the root of the issue, correctly disabled the electric trim [memory item on the checklist], for some reason left the engines at takeoff power [possibly just overlooked them, though overlooking engine power setting is like overlooking breathing to pilots], and when even knowing it was part of the problem, they correctly re-enabled the electric trim system in order to help them manage the situation, they then failed to command continuous nose up electric trim [which would have cut out MCAS and given them assistance in trimming the aircraft nose up]. The only reason to have the malfunctioning electric trim back on is to command nose up trim. Why turn it on, immediately command nose up, then stop and leave the faulty system engaged? That crew was so close to saving the aircraft that it's frustrating as a pilot and a human. Slight adjustments to the above sequence and they're rightly heroes alongside Captains Sullenberger and Haynes. https://www.reuters.com/article/us-ethiopia-airplane-procedures-explaine/explainer-ethiopia-crash-raises-questions-over-handling-of-faults-on-boeing-737-max-idUSKCN1RG2PP https://www.reuters.com/article/us-ethiopia-airplane-procedu...
- EdwardDiego 7y ago
  Thanks for the detailed reply mate, really appreciate it :)

Do you have something I can read on that "may"? I don't disagree that the throttles weren't moved, but the part about it maybe having saved them is new information.

sokoloff 7y ago

I'll give you the short explanation and then an article reference supporting. That might give you other terms to further research. The trim is driven by a jackscrew. That jackscrew is driven by a mechanism in the cockpit (a large double wheel near each flight crew station). At low and moderate airspeeds, the jackscrew turns relatively easily. At high airspeeds and low elevator deflections (meaning "when the aircraft is approximately in trim"), the jackscrew turns relatively easily. At high airspeeds and high elevator deflections, the forces on the tail make the jackscrew difficult to turn due heavy forces. This would be the case where the aircraft is trimmed heavily nose down and the crew is holding large amounts of up elevator to compensate. (You're basically cranking the tail into a different position against the air loads on it.) Slowing the airplane down would almost surely have helped the crew by reducing these loads. If you're going too fast (information the crew had available to them both in cockpit and confirmed by radio after they inquired while fighting), 94% N1 is not where you want the engines set. It's not a popular or comfortable position to look into the actions of the crew and find areas for improvement in light of the fact that they were dealt a very difficult situation that morning. Even with that, it appears that they correctly diagnosed the root of the issue, correctly disabled the electric trim [memory item on the checklist], for some reason left the engines at takeoff power [possibly just overlooked them, though overlooking engine power setting is like overlooking breathing to pilots], and when even knowing it was part of the problem, they correctly re-enabled the electric trim system in order to help them manage the situation, they then failed to command continuous nose up electric trim [which would have cut out MCAS and given them assistance in trimming the aircraft nose up]. The only reason to have the malfunctioning electric trim back on is to command nose up trim. Why turn it on, immediately command nose up, then stop and leave the faulty system engaged? That crew was so close to saving the aircraft that it's frustrating as a pilot and a human. Slight adjustments to the above sequence and they're rightly heroes alongside Captains Sullenberger and Haynes. https://www.reuters.com/article/us-ethiopia-airplane-procedures-explaine/explainer-ethiopia-crash-raises-questions-over-handling-of-faults-on-boeing-737-max-idUSKCN1RG2PP https://www.reuters.com/article/us-ethiopia-airplane-procedu...

EdwardDiego 7y ago
Thanks for the detailed reply mate, really appreciate it :)