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This claim is being disputed by Chesley Sullenberger who is undoubtedly a great pilot and who has actually witnessed the MCAS behaviour in a simulator: http://w

by fsh 7y ago

This claim is being disputed by Chesley Sullenberger who is undoubtedly a great pilot and who has actually witnessed the MCAS behaviour in a simulator: http://www.sullysullenberger.com/my-letter-to-the-editor-of-new-york-times-magazine/ http://www.sullysullenberger.com/my-letter-to-the-editor-of-...

WalterBright 7y ago
"These emergencies did not present as a classic runaway stabilizer problem" Since the LA and EA crews both successfully countered the runaway trim with the electric trim switches, this statement by Captain Sullenberger is inadequate. Furthermore, I have no idea what "classic runnaway stabilizer" is. When the trim starts erroneously pointing the airplane down, it's runaway trim. There is no other kind. BTW, I worked for three years on the 757 stabilizer trim system. I know what runaway trim is.
- mchristen 7y ago
  I think your definition of 'success' is flat out wrong. Where are those pilots now?
  - atdrummond 7y ago
    They did it over two dozen times on one of the flights. It's a tragedy they did not hit the cutout but that's SOP and went by the wayside.
- pdonis 7y ago
  > When the trim starts erroneously pointing the airplane down, it's runaway trim. No, "runaway trim" as it was defined for every 737 variant prior to the MAX was more specific than that: it meant the trim system would continuously adjust the trim in an erroneous direction. The continuously is key. In the 737 MAX during erroneous MCAS operation, the trim is not adjusted continuously: it is adjusted intermittently. An adjustment of a given fixed increment is made; then nothing happens. Then, a short time later, another adjustment of a given fixed increment is made; then nothing happens. Then... This presentation is not at all the same as normal runaway trim that 737 pilots are trained to deal with. So what is inadequate is not Capt. Sullenberger's statement, but yours.
  - WalterBright 7y ago
    > The continuously is key. It continuously activated and ran forcing the nose down. Your pedantism is suitable for courtroom drama, but is inappropriate when you're in command of an airplane. In fact, I suspect a judge would ridicule such an argument. I was involved in a court case once where the opposition based their case on navigating around the overly literal definitions of words. The judge ruled against them on every point. They appealed, and it went before a 3 judge panel, that unanimously ruled against them on every point. Do you seriously believe a pilot, faced with trim that kept turning on trying to dive the airplane, would not think "I need to shut off the stabilizer trim. Oh wait, I'll leave it on because it's intermittent!" ? There's a reason airplanes have not dispensed with pilots and gone fully automated.
    - pdonis 7y ago
      > It continuously activated and ran forcing the nose down. Normal runaway trim does, yes. MCAS failure does not, and did not in the incidents. MCAS only intermittently adjusted the trim. (Yes, the computer was continuously running the MCAS algorithm, but that's not visible to the pilot, and if you're going to hang your hat on that definition of "continuously" you are the one being pedantic, not me.) > Do you seriously believe a pilot, faced with trim that kept turning on trying to dive the airplane, would not think "I need to shut off the stabilizer trim. Oh wait, I'll leave it on because it's intermittent!" ? First, I have not said the pilots could not have done anything to prevent the crashes. Of course they could. But the thing they could have done was not "the runaway trim procedure". Second, the pilots were being bombarded with multiple warnings and conflicting information. Sure, it's easy to sit in your armchair and say they should have figured out that shutting off the stabilizer trim was the right thing to do (and even then they would have had to first figure out that they needed to use the manual electric trim to put the trim where it was supposed to be, since shutting off the automatic stabilizer trim would also shut off the manual electric trim). But pilots are not omniscient and they're not magicians. There are limits to what humans can figure out under the conditions those pilots were subjected to. > There's a reason airplanes have not dispensed with pilots and gone fully automated. And there's a reason that pilots are supposed to have full information about any system in the plane that they might be expected to have to override. Pilots weren't even told about the existence of MCAS until after the Lion Air crash; and even then they weren't told exactly what it did or how it worked or how an issue could arise or how the system could put the plane into an unrecoverable state. There's also a reason that the plane is not supposed to subvert the pilots' attempts to control it when it starts doing wrong things.

by fsh 7y ago

WalterBright 7y ago

"These emergencies did not present as a classic runaway stabilizer problem" Since the LA and EA crews both successfully countered the runaway trim with the electric trim switches, this statement by Captain Sullenberger is inadequate. Furthermore, I have no idea what "classic runnaway stabilizer" is. When the trim starts erroneously pointing the airplane down, it's runaway trim. There is no other kind. BTW, I worked for three years on the 757 stabilizer trim system. I know what runaway trim is.

mchristen 7y ago
I think your definition of 'success' is flat out wrong. Where are those pilots now?
- atdrummond 7y ago
  They did it over two dozen times on one of the flights. It's a tragedy they did not hit the cutout but that's SOP and went by the wayside.
pdonis 7y ago
> When the trim starts erroneously pointing the airplane down, it's runaway trim. No, "runaway trim" as it was defined for every 737 variant prior to the MAX was more specific than that: it meant the trim system would continuously adjust the trim in an erroneous direction. The continuously is key. In the 737 MAX during erroneous MCAS operation, the trim is not adjusted continuously: it is adjusted intermittently. An adjustment of a given fixed increment is made; then nothing happens. Then, a short time later, another adjustment of a given fixed increment is made; then nothing happens. Then... This presentation is not at all the same as normal runaway trim that 737 pilots are trained to deal with. So what is inadequate is not Capt. Sullenberger's statement, but yours.
- WalterBright 7y ago
  > The continuously is key. It continuously activated and ran forcing the nose down. Your pedantism is suitable for courtroom drama, but is inappropriate when you're in command of an airplane. In fact, I suspect a judge would ridicule such an argument. I was involved in a court case once where the opposition based their case on navigating around the overly literal definitions of words. The judge ruled against them on every point. They appealed, and it went before a 3 judge panel, that unanimously ruled against them on every point. Do you seriously believe a pilot, faced with trim that kept turning on trying to dive the airplane, would not think "I need to shut off the stabilizer trim. Oh wait, I'll leave it on because it's intermittent!" ? There's a reason airplanes have not dispensed with pilots and gone fully automated.
  - pdonis 7y ago
    > It continuously activated and ran forcing the nose down. Normal runaway trim does, yes. MCAS failure does not, and did not in the incidents. MCAS only intermittently adjusted the trim. (Yes, the computer was continuously running the MCAS algorithm, but that's not visible to the pilot, and if you're going to hang your hat on that definition of "continuously" you are the one being pedantic, not me.) > Do you seriously believe a pilot, faced with trim that kept turning on trying to dive the airplane, would not think "I need to shut off the stabilizer trim. Oh wait, I'll leave it on because it's intermittent!" ? First, I have not said the pilots could not have done anything to prevent the crashes. Of course they could. But the thing they could have done was not "the runaway trim procedure". Second, the pilots were being bombarded with multiple warnings and conflicting information. Sure, it's easy to sit in your armchair and say they should have figured out that shutting off the stabilizer trim was the right thing to do (and even then they would have had to first figure out that they needed to use the manual electric trim to put the trim where it was supposed to be, since shutting off the automatic stabilizer trim would also shut off the manual electric trim). But pilots are not omniscient and they're not magicians. There are limits to what humans can figure out under the conditions those pilots were subjected to. > There's a reason airplanes have not dispensed with pilots and gone fully automated. And there's a reason that pilots are supposed to have full information about any system in the plane that they might be expected to have to override. Pilots weren't even told about the existence of MCAS until after the Lion Air crash; and even then they weren't told exactly what it did or how it worked or how an issue could arise or how the system could put the plane into an unrecoverable state. There's also a reason that the plane is not supposed to subvert the pilots' attempts to control it when it starts doing wrong things.