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https://ad.easa.europa.eu/ad/NM-18-33 https://ad.easa.europa.eu/ad/NM-18-33 well hold your horses there... from the FAA in their 2019 report linked above: > T
by lazystar 1y ago
https://ad.easa.europa.eu/ad/NM-18-33 https://ad.easa.europa.eu/ad/NM-18-33
well hold your horses there... from the FAA in their 2019 report linked above:
> The Boeing Company (Boeing) received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to supply or cutoff fuel to the engines. The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions. In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position. If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown. Boeing informed the FAA that the fuel control switch design, including the locking feature, is similar on various Boeing airplane models. The table below identifies the affected airplane models and related part numbers (P/Ns) of the fuel control switch, which is manufactured by Honeywell.
> If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown
- noduerme 1y agoWhat is "01 second" as quoted above? If it's 1 second, you could possibly conclude that it was intentional. If it's 0.1 second you might think it was an accident and the lock was disengaged.
- JumpCrisscross 1y agoOne second. (Runway four is frequently zero four because radios.)
- deleted 1y ago[deleted]
- mjevans 1y agoMany systems log samples at an intervale of one sample per second. I could easily envision a transition event where a bump or brush of something sufficiently toggles one switch and then a fraction of a second later the other.
- chgs 1y agoIf the time was :11 and :12 there’s between 0.01 and 2 seconds between. If they were both at :11 then it’s between 0.01 and 1 second.
- bayesianbot 1y agoBetween (0, 2)s. Apparently the times are rounded down, so it could be :42.001 and :43.999, or :42.999 and :43.001
- rnd33 1y agoThere is no electronic lock as far as I know, as many people seem to assume. It's a mechanical notch that you have to physically pull the switch past to operate it. The lock failures described in the air worthiness directive was about this mechanical stop or notch not being installed.
- sugarpimpdorsey 1y agoTotally different airplane with a totally different flight deck, designed generations apart. The fact that the manufacturer is the same is irrelevant. You are trying to draw parallels between the ignition switch in a 1974 Ford Pinto and a 2025 Ford Mustang as if there could be a connection. No.
- dvh 1y agoEntirely different kind of flying altogether
- sbuttgereit 1y agoAnd yet the preliminary report for the incident in question includes reference to that bulletin, indicates that the switches in the accident aircraft were of a very similar design and subject to advisory inspections: "The FAA issued Special Airworthiness Information Bulletin (SAIB ) No. NM -18-33 on December 17, 2018, regarding the potential disengagement ofthe fuel control switch locking feature. This SAIB was issued based on reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The airworthiness concern was not considered an unsafe condition that would warrant airworthiness directive (AD) by the FAA. The fuel control switch design , including the locking feature, is similar on various Boeing airplane models including part number 4TL837-3D which is fitted in B787-8 aircraft VT-ANB. As per the information from Air India, the suggested inspections were not carried out asthe SAIB was advisory and not mandatory. The scrutiny ofmaintenance records revealed that the throttle control module was replaced on VT-ANB in 2019 and 2023. However, the reason for the replacement was not linked to the fuel control switch. There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB." So while I agree that this being the cause sounds unlikely, referencing the switch issue is something relevant enough for the report itself.
- Emdeha2357 1y agoThere Is a connection: The same type and make of switches, which already where officially found to be prone to subtle malfunction and ought to be checked and replaced. Read the SAIB. Look at the switches. https://www.xuefeiji.org/public/uploads/weixin_mpimgs/e3/e365c260c9.gif https://www.xuefeiji.org/public/uploads/weixin_mpimgs/e3/e36... Your argument of being "totally different" flight decks or fordy ignition switches aside (ignoring that one is allowed to to drive both mentioned cars using the same license, but not two different generations of airplanes, ignoring that the biological concept of generation implies kinship), this affair reminds me of https://en.m.wikipedia.org/wiki/General_Motors_ignition_switch_recalls https://en.m.wikipedia.org/wiki/General_Motors_ignition_swit...
- briandear 1y agoYou don’t inadvertently turn off both switches. The linked SAIB was in 2018 and addresses faulty installations, not a failure after use. And preflight over thousands of flights would have detected if the switches had a failed locking mechanism. And for both to fail at once? Practically impossible. Also the recommended inspection — that was almost 7 years ago. If a major airline didn’t comply with the SAIB, that’s on them, not Boeing. There hasn’t been a single reported instance of fuel switches being accidentally switched off on any Boeing airliner — in 320 million flight hours over the past 10 years.
- barbazoo 1y agoSame manufacturer, Air India 171 was a 787-8 though.
- shoghicp 1y agoThe affected table includes these models as well: 787-8, -9, and -10
- barbazoo 1y agoThanks for pointing it out.
- ggreer 1y agoThe only affected models were 737s with the 766AT613-3D fuel control switch. The bulletin recommended that other models be inspected and any defects reported. It's unclear if any 787s were discovered to have the issue. Also the preliminary report mentions that the switches were replaced in 2019 and 2023, after the 2018 bulletin.
- deleted 1y ago[deleted]
- rnlkh 1y agohttps://ad.easa.europa.eu/blob/NM-18-33.pdf/SIB_NM-18-33_1 https://ad.easa.europa.eu/blob/NM-18-33.pdf/SIB_NM-18-33_1 Here is the full SAIB on the Boeing fuel control switches. This report lists the part 4TL837-3D as the switch used on 787s, and is the part mentioned in the preliminary report on the accident. The SAIB does single out the part 766AT613-3D, but that's for suggesting a replacement for it as 766AT614-3D. Per the Honeywell catalog for 4TL837-3D, if is a Snap Action toggle switch. The base model doesn't have a locking mechanism, which is available as an option
- lazystar 1y agostill, it at least shows that there's been issues with the locking mechanism in the past. inadvertently bumping something that was assumed to be locked is a simpler theory; i find it hard to believe that a murder suicider would take this route, when the china nosedive option is easier, faster, and has a higher chance of success.
- tekla 1y agoThey don't mention the locking mechanism being disabled
- cosmicgadget 1y agoIs it easy to inadvertantly move both switches in such a scenario?
- sandspar 1y agoThe switches are spring-loaded, notched in place, and have a rubber knob on the top. A pilot must squeeze the knob, remove the switch from its ON notch, press the switch, click it into the OFF notch, then release the knob. Doing it accidentally is impossible.
- raphman 1y agoHere's also a video showing operation of the switches: https://www.youtube.com/watch?v=33hG9-BCJVQ https://www.youtube.com/watch?v=33hG9-BCJVQ
- lysace 1y agoNo.
- mdavid626 1y agoWell, can you move it back, when accidentally activated?
- VBprogrammer 1y agoIn older turbine aircraft this would cause a hot start or worse. It would be interesting to know what the FADEC systems do in this case.
- joshAg 1y agoat least one of the pilots did. according to the preliminary report, the switches were only in the cutoff position for 10 seconds before being switched back to the run position and the engines started to spin up again
- the__alchemist 1y agoYes, and it restarts the engines, but it takes on the order of seconds; too long at that altitude. One of the pilots did that, but it was too late.
- TylerE 1y agoMore like 30 seconds. Just throttling an already running engine up from idle (which is quite a bit above zero throttle in most respects) takes seconds.
- alvah 1y agoTurbines take a while to spin up again, it's not like start/stop in a car.
- stetrain 1y agoThey were moved back to the run position 10 seconds after being switched off, and the engines were in the very early stages of restarting by the time of the crash. It was too late.
- sillysaurusx 1y agohttps://www.youtube.com/live/SE0BetkXsLg?si=LPss_su3PVTAqGCO https://www.youtube.com/live/SE0BetkXsLg?si=LPss_su3PVTAqGCO Both of these extremely-experienced pilots say that there was near zero chance that the fuel switches were unintentionally moved. They were switched off within one second of each other, which rules out most failure scenarios. If it was an issue with the switches, we also would have seen an air worthiness directive being issued. But they didn’t, because this was a mass murder.
- chrisandchris 1y ago> If it was an issue with the switches, we also would have seen an air worthiness directive being issued. I do not trust these air worthiness directives 100.0%. The 737 Max also required two catastrophic failures before it was grounded.
- decimalenough 1y agoThe issue with the 737 MAX became evident within months of the plane's launch. By contrast, the Dreamliner has accumulated over a decade of flying history across over 1000 aircraft with precisely zero fatal accidents.
- sgt101 1y agoAbsence of evidence isn't evidence of absence. The fact that the pilots denied that they had shut the switch (one asking the other why they had done so and the other denying it), and that they restarted the engines should be taken into account. Ok, murder suicide is definitely on the table but I would want to see some other reasons for believing that this is so.
- jon_smark 1y agoSorry to nitpick, but for a good Bayesian, absence if evidence is evidence of absence. If you want the aphorism to be technically correct, you should say "absence of proof is not proof of absence". A note on the terminology: "evidence" is a piece of data that suggests a conclusion, while not being conclusive by itself. Whereas "proof" is a piece of data that is conclusive by itself.
- darth_avocado 1y agoOne would assume a toggle like that would come with blaring alarms and blinking lights… right? Right?? Edit: It also seems like the engine cutoff is immediate after the toggle. I wonder if a built in delay would make sense for safety.
- lazide 1y agoLow altitude, stall, and impact with terrain certainly will. And with how low and slow they were during takeoff, those would have been going off almost instantly.
- cjbprime 1y ago> I wonder if a built in delay would make sense for safety. (Presumably delaying the amount of time before a raging engine fire stops receiving fuel would also have an impact on safety?)
- russdill 1y agoThese switches are operated at startup and shutdown. So pretty much daily. By pilots and likely maintenance crews. Such a defect with not to unnoticed for long
- 0_-_0 1y agoIt could have been unimportant to them
- deleted 1y ago[deleted]