Timeline for If Boeing used two sensors instead of one simultaneously, wouldn’t they be in the same position today?
Current License: CC BY-SA 4.0
17 events
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| Aug 11, 2022 at 23:27 | comment | added | Koyovis | @PeteP. There is validity in your argument. However, the pilots of the 2 crashed planes were trained for stab runaway, and did not recognise the MCAS behaviour as such. So something in the MCAS behaviour did not match their simulator training. | |
| Aug 11, 2022 at 10:56 | comment | added | Pete P. | It is mind-boggling that all the experts who declared that the pilots were lacking training for the new and unexpected type of runaway because Boeing "hid" the system, never bothered to run through the scenario in their head to validate it… and discover its absurdity. | |
| Aug 11, 2022 at 10:55 | comment | added | Pete P. | The question to all those experts who insisted that the pilot needs to know if the runaway is continuous or intermittent… How would you determine that? By watching and waiting— i.e. doing absolutely nothing while the nose slews towards Heaven and a stall, or towards Hades and your ad hoc gravesite—until the stabilizer either reaches the physical travel limit or stops short of it?! And then, for what do you use that little nugget of information? (while your fellow pilot stares at you with growing alarm, unsure whether you are paralyzed by shock, or you are suicidal). | |
| Aug 11, 2022 at 10:52 | comment | added | Pete P. | …There is no use for discerning whether the runaway is intermittent or continuous or what is causing it. Not only is the system not designed for quick and more in-depth fault isolation by the pilots beyond "autopilot" and "other", but the recovery procedure doesn't care; regardless of cause it is essentially: shut down autopilot… if that doesn't do it, shut down electric trim… | |
| Aug 11, 2022 at 10:51 | comment | added | Pete P. | @Koyovis The Runaway Stab Trim NNC was already in the FCOM and none of the possible causes were listed. The definition of RST: The stab moves—un-commanded—to a position it should not be. About 2–3 seconds into a RST the pilot will notice the pitch attitude deviating and will instinctively restore it using the elevator. At 4–5 seconds s/he senses that the elevator force needed to maintain pitch attitude is abnormally high and getting worse. By 6–8 seconds s/he is reaching for the electric trim to assist with the elevator force and notices that the stab is being trimmed—excessively… | |
| Aug 9, 2022 at 2:53 | comment | added | Koyovis | @PeteP. Evidently, there was a need for including the existence of MCAS in the FCOM. It caused a repeating stab trim runaway, and trim did not run away all the way. | |
| Aug 8, 2022 at 20:56 | comment | added | Pete P. | @Robin Bennett The pilots can't detect normal MCAS operation, can't control/adjust it, can't turn it ON or OFF, there is no mention of it in system fault messages, checklists or procedures. Nonnormal operation manifests as a runaway stabilizer trim, which has multiple causes and is handled without fault isolation, by the same NNC regardless of cause, and for which initial and recurrent simulator training is standard. The system is transparent to the flight crew, so no MCAS-specific flight-sim training is necessary or even possible and there is no need for its inclusion in the FCOM. | |
| Aug 5, 2022 at 7:58 | comment | added | Robin Bennett | @PeteP. I'd have thought that was obvious. Pilots should know that the system is there, that's it's vulnerable to a failure of the AoA sensor, how to recognise a failure and how to disable the system and regain control. | |
| Aug 4, 2022 at 20:57 | comment | added | Pete P. | @Robin Bennett "Boeing and the FAA also decided that the pilots didn't need to be trained on this system." Actually, Boeing and the FAA decided that there was no training for this system, i.e. no training was possible. That is why the airplane has returned to service and there is STILL no flight simulator training for MCAS. But since you think there should be—btw, you're not the only one to think so—please enlighten us with some details on what that training should consist of. | |
| Jul 19, 2022 at 23:29 | comment | added | Pete P. | The answer is seriously flawed. One of the conditions that must be satisfied for the system to activate cannot serve as "protection against false positives" of the other condition because the parameters are independent and unrelated, and completely unaware as to the validity of each other. The author of the article had no understanding of basic engineering yet attempted to conduct an accident investigation and perform engineering analysis. Also, the parameters are used as analog variables that trigger MCAS and modulate its duty cycle, not as binary discretes that merely flip MCAS on or off. | |
| Jan 28, 2020 at 0:08 | comment | added | Koyovis | @Firefighter1 Very, very good point! | |
| Jan 21, 2020 at 21:34 | comment | added | George Clooney In a Mooney | But even if they use one sensor, how can it not reject just based off the sensors differing? I know they work simultaneously, but couldn’t they have been an easy change? | |
| Jan 17, 2020 at 13:58 | comment | added | Robin Bennett | I think you can also add that Boeing and the FAA also decided that the pilots didn't need to be trained on this system. | |
| Jan 17, 2020 at 6:00 | vote | accept | George Clooney In a Mooney | ||
| Jan 17, 2020 at 4:41 | history | edited | Koyovis | CC BY-SA 4.0 |
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| Jan 17, 2020 at 0:13 | history | edited | Koyovis | CC BY-SA 4.0 |
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| Jan 17, 2020 at 0:07 | history | answered | Koyovis | CC BY-SA 4.0 |