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| Shep69
June 20, 2025, 18:37:00 GMT permalink Post: 11907194 |
How does a non-faulty autothrottle pull power to idle at the critical time we are witnessing (i.e. just before or just after takeoff)?
I don't mean to keep asking this, but I still haven't gotten an answer. Unless the allegation is that the crew did not arm the autothrottle properly, it just doesn't make sense to me. An auththrottle malfunction makes as much sense as anything else at this point. But even if not I wonder if the low altitude capture scenario would dramatically pull off power initially assuming the aircraft was going to level off before restoring it as the aircraft slowed down. Didn`t fly the 78 but on the 777 the auththrottles were laggy sometimes. Subjects: None |
| Shep69
June 20, 2025, 19:23:00 GMT permalink Post: 11907231 |
I am specifically asking about the case without a malfunction because my understanding is that the autothrottle
explicitly
does not affect thrust between passing 80 knots on the runway and passing 400 ft AGL.
Neither does (or should?) any autopilot mode (except LNAV? at 50 feet?) be active under 400 feet. Armed yes but not actually engaged. So how would either of these things have any effect on an aircraft that's just lifting off unless they're faulty? Everything I can turn up seems very clear that the autothrottle, VNAV, etc only engage at 400 feet AGL on departure. In fact, both altitude capture incidents I've been able to turn up were only triggered when the autopilot was engaged. Why would any pilot be engaging the autopilot bare seconds after lift-off? BUT Say the MCP is mis-set to 200’ or so. VNAV never engages and the expected mode (from others; I`ve never tried it) would be SPD xxx ALT. The modes still engage regardless of whether or not the airplane is on autopilot; the autopilot itself just follows the flight director commands (and the PF certainly woudn`t follow the FD in this case). Autothrottles are independent of autopilot. And the autothrottles would initially be expected to reduce thrust to whatever value the squirrels think is appropriate to level flight. They WILL advance (how fast I don`t know) to maintain speed on auto throttle but this would be confusing. That`s the scenario I`m wondering about as well as a failure of the auththrottles themselves; it`s as plausible as anything else they engaged to reduce thrust for some wild reason. Subjects: None |
| Shep69
June 20, 2025, 21:52:00 GMT permalink Post: 11907348 |
To be clear, are you stating categorically or guessing (or neither, and I'm misreading you and you mean something else) that the 787's autothrottle will come
out of HOLD
and into SPD mode
below 400 feet
by design in response to the altitude that's set in the mode control panel, entirely by itself, without the autopilot engaged? Not that this is the way it would behave in normal flight - that this is the way it is
designed
to behave while it's in HOLD mode for takeoff?
I am actually looking for an answer from a pilot (or at least someone with an FCOM who can share any relevant passages) because nothing I have been able to look up on my own suggests that this is the case. All secondary sources I can find just say that the autothrottle is inhibited under 400 feet on takeoff, with my impression being that the crew is expected to manage thrust manually during that phase of flight. The incidents I was able to turn up involving an aircraft attempting to capture a target altitude at takeoff specifically don't help either: - G-ECOE: Flight was completely normal until the crew engaged the autopilot at 1350 feet, at which point the aircraft started diving to the target of 0 feet. However it involved a Dash 8 and not only is that not a Boeing aircraft, it doesn't have an autothrottle to begin with. Nothing to conclude from this. - F-WWKH: Again automated deviation was triggered by the crew engaging the autopilot a few seconds after takeoff as part of a test flight. However again also not a Boeing aircraft (an A330) and the selected target altitude was 2000 feet so the autopilot tried to pitch up to capture it. Not sure if anything can be concluded from this. - A6-EQI: The most relevant, being a Boeing 777, with wide speculation being that the selected altitude was left at 0 feet. However the preliminary report is very thin so there's little to go on in the way of factual information, but the problem seems to entirely have been that the pilot flying was following the flight directors without question. There's zero indication of any loss of thrust, in fact they seem to have nearly entered an overspeed condition partly due to the shallow climb angle implying that the engines were doing just fine. So it doesn't seem like the selected altitude caused the autothrottle to do anything. I am sorry if it seems like I'm banging on about this autothrottle point a bit much but as an engineer it just seems completely backwards to me. What exactly is the point of the HOLD mode or of setting those specific gates (80 knots, 400 feet) if the autothrottle can so easily come out of it? The design might as well not have it at all and just leave the autothrottle in THR REF for takeoff then - what would be the difference? I am guessing because although I flew the 777 I never tried a low altitude capture before VNAV engaged — and it`s been a few years). But think it probably would. As one goes through 50’ LNAV engages; VNAV is normally armed prior to the EFIS check if it`s to be used (which it usually is). So in this scenario LNAV would have been engaged but since VNAV is armed but never engages my guess is that the automatics would engage in SPD/LVAV/ALT. I could be wrong. The PF would have been hand flying (and obviously not following the flight director with autothrottles engaged). HOLD is present in many other regimes of flight; all it means is that the auththrottle (right now) is not controlling the throttles and they stay where they are—and the PF can move them if desired at will. Fr` instance, when descending in FLCH or even VNAV SPD the throttles will usually be in HOLD. (To me this usually meant `hold` the throttles—and tweek them in descent as required). Thrust can be modulated to adjust rate of descent (the throttles become vertical speed levers). On altitude capture in the case of FLCH or path capture in the case of VNAV SPD (in descent) the auththrottles kick in and it becomes SPD/xxx/ALT (or VPTH or VALT as the case might be). Most everyone knew the autothrottles would not engage below 400` and that FLCH in descent at very low altitudes was not an appropriate mode — and they did not activate providing low speed protection in the case of Asiana. IIRC our throttles went into HOLD at 60 knots and stayed there until VNAV activated (THR REF—takeoff thrust). It was also possible that the autothrottles under some environmentals wouldn`t fully achieve takeoff thrust setting (EPR or N1 depending on which engines) and they could be manually moved in HOLD to achieve it. Although I don`t remember that as ever happening. But at this point it`s a guess because I never did it (MCP set at low altitude on takeoff with VNAV never engaging). Perhaps someone else has. Last edited by Shep69; 20th June 2025 at 22:05 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FCOM Preliminary Report TOGA Takeoff Roll |
| Shep69
June 20, 2025, 22:29:00 GMT permalink Post: 11907366 |
I suppose an informed guess is the best answer I can get here, short of someone having access to an actual sim or a Boeing engineer chipping in. Though I am curious that you are guessing that it
would
engage, when in the example you give to point out the autothrottle being inhibited at low altitudes (the Asiana accident at SFO) the autothrottle
didn't
engage - not even to provide low speed protection, a potentially life-and-death matter. If that accident was my only datapoint my guess would be that if it's strict enough to not engage for stall protection, it's strict enough to not engage for altitude capture.
Also to be clear I do know that the autopilot and autothrottle are independent - I have been talking about the autopilot because as I listed, in the incidents I could find where the aircraft automatically tried to capture a target altitude on takeoff, the autopilot was first engaged. So my impression was that until then the aircraft might provide guidance (like in the Emirates case) but will not actually do anything to change the thrust, pitch, etc parameters that have been set. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FCOM Parameters |
| Shep69
June 20, 2025, 22:59:00 GMT permalink Post: 11907385 |
Both the B777 and B787 have a minimum autopilot engage height of 200'. I would suggest it is often the best course of action after an engine failure to engage the autopilot at 200' to dramatically reduce the workload!
When talking about low altitude capture below the 400' VNAV engagement height, although it has been talked about, would mean (mis) setting the MCP altitude to less than 400'. I really find that implausible. You are correct though that the modes would be SPD | LNAV | ALT should this occur. All correct. The lack of autothrottle automatic activation when the autothrottles are in HOLD mode and the speed has decayed below minimum manouevring speed has been addressed. The autothrottle will now automatically activate if, when in HOLD mode, the speed decays below minimum manouevring speed with FMC software after BP4 on the B787 and after AIMS V17B on the B777. Since the Asiana accident many airlines prohibit use of FLCH below 1,000' and the lowest altitude setting when using FLCH is then, of course, 1.000' Almost fully correct, the speed when autothrottles transition to HOLD on takeoff is 80kts. on both the B777 and B787. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All) |
| Shep69
June 21, 2025, 18:58:00 GMT permalink Post: 11907986 |
I would take that post by Crossky with a grain of salt. No part of his post made sense and I can only assume he is not a 787 pilot despite claiming to be. "Fuel starvation if pumps aren't turned off, not in my manual but I read about a procedure on the Internet", it's loony stuff.
. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank Fuel (All) Fuel Cutoff |
| Shep69
June 22, 2025, 13:13:00 GMT permalink Post: 11908531 |
There is a bigger issue here. The general public are more and more concerned that Boeing is cutting corners, and perhaps that is debatable and a complex balance of "how much do you want to pay for a plane ticket" vs "how absurdly close to diminishing returns can statistical probability get when dealing with some of the most complex machines and industries humanity has ever created".
What isn't debatable is that MCAS was part of an initiative to save on regulatory and training costs. It was designed entirely because a regulatory environment existed where you could extend the fuselage to the point where you needed to mount engines in a way that would essentially make this no longer the same type, and probably not something that any aircraft designer would design fresh. Boeing, like everyone else, played within that framework, but Boeing didn't execute properly and the public optics are that they cut corners on top of cutting corners. I agree that engineering is all about tradeoffs but I don't think anything is "no longer an issue" because we had 2 disasters within a couple of years and learned from mistakes. There is an issue somewhere, maybe a systemic corporate issue, a PR issue, or just a Boeing issue - the Air India crash has the potential to make it far bigger. I also think that saying \x91cutting corners\x92 is an unjustified indictment. They didn\x92t IMHO. What WAS wrong was not making it clear how the system operated and that it could be triggered by a single AOA probe failure. And making it clear that the crew handles it just like any other runaway trim scenario. So to me it was mostly a training issue. IF \x97 and it\x92s a big IF \x97 this accident was caused by an FAA requirement to automatically cut engines with engine runaway due unresponsive throttle (which isn\x92t needed in the first place with FCS and fire handles available) then the primary culpability lay with the regulatory entity (FAA) requiring more silly boxes on airplanes. Without zero thought towards unintended consequences. But at this point it\x92s wayyyyyyy too early to do any Boeing Bashing based on an accident none of us have any clue as to the cause. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FAA |
| Shep69
July 12, 2025, 19:12:00 GMT permalink Post: 11920764 |
If anyone believes both guarded switches flipped to OFF by accident, one after the other in under a second, I\x92d genuinely like to hear the cockpit ergonomics that make that plausible. Because from where I sit, it doesn\x92t happen unless someone means it, or at minimum, fails to follow any known SOP.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Switch Guards |
| Shep69
July 13, 2025, 13:42:00 GMT permalink Post: 11921331 |
I agree with sabenaboy.
The subject of pilot suicide is not distasteful, but for many it is taboo. I understand this. Many historical accidents caused by pilot incompetence could well have been quickly labelled as suicide, only for their errors to show up in the subsequent investigation. Looking for a rational explanation is a normal way to go, and suicide is not rational in most peoples' eyes. However, this tragic event looks highly probable to have been caused by a deliberate action. And shutting off the fuel controls immediately following rotation is impossible to justify as an accidental move. I remember calling the German Wings accident as a likely suicide event as soon as I heard about it. Nevertheless I was open to hostility and recriminations on this website for quite a few days, once my carefully-worded contribution was not deleted. I do wonder if any further information can be gleaned from the FDR, which has not already been shared. I hope so. And of course, the CVR contents require further analysis. Nobody in their right minds takes any pleasure, woke or not, from learning of a suicide, particularly one that involves the death of many innocent people. Mental impairment is a huge and not well understood spectrum. Sometimes it\x92s dark and criminal; sometimes it\x92s long term disease related (Alzheimer\x92s, etc), sometimes acute (stroke), sometimes chemical and mental imbalance developing over a shorter time period (like the US Captain who had a paranoid like episode inflight, or the jumpseater in the US trying to shut down both engines but restrained by crew). In many cases it\x92s impossible to see coming and doesn\x92t even have to involve criminal/homicidal/psychotic intent. It can simply be a stroke or episode which causes confusion and someone to start grabbing at switches best left untouched \x97 perhaps while thinking he is doing the correct actions. So one can not ignore the possibility that a crew member suffered some sort of cognitive episode resulting in shutting off the FCS; perhaps thinking he was back in the chocks for a few minutes. And then forgetting he\x92d done it. These events may be exacerbated by the huge stigma associated with a pilot attempting to seek counseling or mental health help (even for a relatively small problem which can untreated develop into a much larger one). Out of fear of repercussions of falling into that medical \x91black hole\x92 and trying to get re-certified for even minor mental health glitches. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR FDR Mental Health |
| Shep69
July 14, 2025, 19:47:00 GMT permalink Post: 11922454 |
Upfront: Sorry for my initial post on the topic, like some other people in this thread it obviously touches a nerve and was rightly removed for exceeding the rules of civil discussion.
This is my attempt to shed a bit of light on why I find pushing theories of suicide very objectionable at this point in time. Let's actually run some numbers here. https://www.boeing.com/content/dam/b...df/statsum.pdf gives us a nice statistic over the last 20 years and also has this little tidbit: "965 million departures since 1959. 63% of those departures were on Boeing airplanes. (609 million on Boeing airplanes)" For the last 20 years I'd eyeball an average of between 20-25 million departures per year. So 400-500 million flights in just 20 years. Maybe let that sink in for a moment. We have doubled the total number of flights in the 20 years since 2005. In that timeframe we have: Nov 2013, LAM 470, 33 fatalities, confirmed by CVR Mar 2015, Germanwings 9525, 150 fatalities, confirmed by CVR There are additionally these: Mar 2014, MH370, 239 fatalities, no final report, no information available Mar 2022, CES5735, 132 fatalities, no final report, media reports claiming pilot suicide, strong counter by the investigating agency: "CAAC has previously said speculation surrounding the crash had "gravely misled the public" and interfered with accident investigation work." Both confirmed cases in that time have a very clear pattern that does in no way resemble the Air India Crash. Even beyond that timeframe no confirmed pilot suicide involved any measures against discovery by the departed. There is speculation regarding Silk Air 185 because the CVR failed to record the relevant part of the accident, but it is firmly in the "debated" category. But we can ignore all of that. Even if we put any theoretically possible Pilot Suicide into the equation one fact remains: The actual likeliness of pilot suicide has not changed. There were 2 confirmed prior to 2005 and 2 after and 2 suspected prior to 2005 2 and after. And that is despite a higher sensitivity and a more stressful job as well as significantly increased environmental stress factors. Obviously we are talking about, statistically speaking, numbers too small for analysis, but all of this is actually well within expected parameters. The recent years have seen a focus on mental health in general in many countries worldwide, and mental healthcare availability is growing in most countries. And here the US is a great example as far as aviation goes: https://casten.house.gov/media/press...tion-committee With this bill whose merit can be assessed by the people supporting it: " The legislation is endorsed by the Pilot Mental Health Campaign, Air Line Pilots Association, Airlines for America, the National Air Traffic Controllers Association, National Flight Training Alliance, the National Business Aviation Association, and NetJets Association of Shared Aircraft Pilots (NJASAP)." Summing up I would like to point out that there are good indications that there are no mental health issues involved here. Taking the aforementioned accidents as reference the issues were usually quite obvious once any kind of scrutiny was placed on the individuals involved. The individuals also made little to no effort of concealment in all confirmed cases and while the absence of evidence can be interpreted as indicative of successful concealment it is not proof and cannot be treated as such. Especially when it is documented that the overwhelming majority of suicides do not involve any element of concealment, and the psychological mechanisms at work commonly preclude any thought about what happens after, as far as medical study of the issue is concerned. This does not mean it does not happen, cases of concealment attempts or even partial successes are well documented, but it is a lot less prevalent. In this case estimates range mostly from between 10% to 30% of all suicides being misreported as unintentional injury with massive variation depending on multiple factors like country, ethnicity, gender, sexual identity, etc. In final conclusion: Anyone can make mistakes. It is possible one or both of these pilots made a mistake. It is also possible that a combination of bad luck lead to an alignment of the holes. In my opinion the inability to receive urgently required medical support is as much a hole in the Swiss Cheese as the worst maintenance or design error imaginable. We know from the previous discussions in all threads on this Accident and the report itself that the pilots were flying their aircraft until they ran out of time and airspace. One cannot demand more from a human being, no matter what the final cause is ultimately determined to be. ANY Boeing pilot who grabs for the FCSs immediately after takeoff has SOME type of mental health issue. It might be suicidal, it might be cognitive, it might be a stroke, it might be some type of blood interruption to the brain, chemical imbalance, drug reaction, or whatever. It’s not a simple mistake. I’m not saying it’s necessary deliberate or homicidal (which it could be) but there is some type of impairment there. Everyone knows the consequences of shutting off a FCS or pulling a fire handle. The switches aren’t easily confused with others. Bumping them doesn’t cause them to go to cut off. And have dire consequences if actuated at the wrong time. I guess there might theoretically be a way to snag them with loose clothing (like having a very frayed sweater with holes in the sleeve putting one’s arm in a really strange place) somehow and while pulling to free it manage to pull them out and down but I’m going to put this in the asteroid hitting earth category. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR Fuel (All) Fuel Cutoff Switches Mental Health Parameters |
| Shep69
July 16, 2025, 00:30:00 GMT permalink Post: 11923361 |
No pilot is expecting to see the FCSs in cut off right after rotation. And is busy flying. So I can see it taking a bit to be recognized and acted upon. There\x92s also the disbelief factor for the person remedying the situation. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Dual Engine Failure Engine Failure (All) Fuel (All) Fuel Cutoff Switches |