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| Sailvi767
June 18, 2025, 02:49:00 GMT permalink Post: 11904851 |
Yes, while there were other complications in play, this accident was caused by a single- throttle rollback after takeoff that wasn't detected by the crew:
https://en.wikipedia.org/wiki/TAROM_Flight_371 To my way of thinking, if you are in the habit of having your hand on the TLs, you're more likely to push them up when needed. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): V1 |
| Sailvi767
June 18, 2025, 15:00:00 GMT permalink Post: 11905313 |
There has been a lot of discussion of the possibility that the crew shut down the wrong engine or misidentified some other problem as an engine failure, usually followed by an assertion that nobody would touch the engines before x feet. PPRuNe's own survey, at the top of this very subforum, found a really high base rate of wrong engine incidents:
Also, on the point about sitting on your hands to 400/1000 feet AAL, someone who has already deviated from a standard operating procedure is more likely to go on to make another mistake; that is why the procedure existed in the first place. As a memo item, here are the survey results: Q1. Have you ever shut off the wrong engine in the sim? Yes: 5.4% +0.9% No: 94.6% -0.9% Q2. Have you ever ALMOST shut off the wrong engine in the sim? Yes: 26% -1.0% No: 74% +1.0% Q3. Have you ever witnessed a colleague shut off the wrong engine in the sim? Yes: 16% +1.0% No: 84% -1.0% Q4. Have you ever witnessed a colleague ALMOST shut off the wrong engine in the sim? Yes: 45% +2.0% No: 55% -2.0% Link to original post Senior Pilot Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All) Engine Shutdown |
| Sailvi767
June 18, 2025, 22:04:00 GMT permalink Post: 11905578 |
Correct. If the flights involved needed less than 128,000 lbs of fuel the center tank would not be used. There is a scavenge system to insure the center tank remains empty when burning from the wing tanks. On the flight in question 128,000 lbs of fuel would in fact likely be close to the fuel required. The center tank might have been empty or contained a small amount of fuel. It\x92s quite possible the aircraft could have been transitioning from center tank to wing tank fuel at liftoff. With the design of the fuel system I can\x92t really see how that could be significant but I am sure it will be looked at in the investigation.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank |
| Sailvi767
June 18, 2025, 22:30:00 GMT permalink Post: 11905595 |
Never do math in public. You are correct. The center tank should have had a significant amount of fuel at takeoff. Probably at least 40,000 lbs.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank |
| Sailvi767
June 19, 2025, 11:08:00 GMT permalink Post: 11905928 |
I have to agree with you
PBL
. It is amazing that people are still arguing about the height the aircraft reached during the first 11s of the flight. It is almost measurable to the metre from the aircraft wingspan on the video. Do not mistake the power required to reach Vr within in the TORA with the power required to maintain a stable climb at V2 to V2+10 in the second and third segments. They are very different numbers, that's why Perf A is one of the dark arts of aviation! It is quite probable that this aircraft rotated below a suitable Vr speed for the weight and ambient conditions and was unable to establish a stable climb due lack of applied power. Big engines take time to spool up, your immediate future depends on how late you recognise the situation and go for TOGA.
But you ask..... How can an aircraft possibly get airborne with a stalled wing? Look at Air France 7775 . At rotate the wing was already stalled (albeit for different reasons) but the airborne profile of the aircraft was rather similar to Air India. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): TOGA V2 |
| Sailvi767
June 19, 2025, 18:28:00 GMT permalink Post: 11906250 |
Software Engineer here. IMO software glitches are more likely than mechanical failures and pilot error, and I would say increasingly more so, particularly with Boeings. I have good reasons, experience and expertise for saying this that I\x92m not going to get into here because it\x92s too long winded and will no doubt upset some people who will mistake facts for rule and let it hurt their feelings.
In 2019 I think it was, an ANA 787 had a TMCA dual engine shutdown just after landing. There was also a bug that shut down all AC power on 787s powered on for 248+ days (integer overflow causing GCU failsafe) that was supposed to be remedied on 2019. Can\x92t find any information confirming that it was implemented on all 787s. These are just two examples of software bugs. There are placed of others, and it\x92s highly likely there are ones we don\x92t know about, either in the original software or in the updates. 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) Engine Shutdown |
| Sailvi767
June 20, 2025, 13:30:00 GMT permalink Post: 11906974 |
Shutting down the wrong engine below 400 AGL is extremely rare. So rare in fact that I believe it has not happened in a jet transport class aircraft.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All) |
| Sailvi767
June 20, 2025, 13:38:00 GMT permalink Post: 11906979 |
During a flameout it takes a while before the fan has slowed down sufficiently. As long as it rotates, thrust is generated.
With full reverse thrust you know that when de-selecting reverser from idle reverse, you have to give the engines plenty of time to slow down otherwise you would get the little "kick in the back" as during deceleration you would generate instant forward thrust when the reversers are stowed. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All) |
| Sailvi767
June 20, 2025, 13:41:00 GMT permalink Post: 11906982 |
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB |
| Sailvi767
June 21, 2025, 12:31:00 GMT permalink Post: 11907707 |
It’s a possibility (as is virtually anything that doesn’t break the laws of physics) but all the training, practicing and checking would have been to emphasise SOPs, which are to leave all the engine controls where they are until you have done a proper interactive diagnosis at a safe height with the flightpath assured.
Where the meme has come from that jet pilots have to shut down engines as quickly as possible I don’t know but it is incorrect. If you left a failed engine without securing it for 5 minutes, little to no harm would come of it. Even if it was on fire (which is not necessarily flames, just higher than normal temperatures inside the nacelle) they are certified to be in this condition for some considerable time before it becomes a problem. Yes, I think the phrase “without undue delay” could be used for a fire indication but that’s a minimum of 400’AGL in Boeings and does not absolve you of all the cross-checking and CRM that should happen with an engine shutdown. This is practiced/checked at the least every 6 months in EASA land and any attempt to rush a shutdown at low level would lead to a debrief and more training/checking. To put it this way, control of the aeroplane and lateral/vertical navigation is far more important than doing stuff with a failed power plant. Something like an ET should be absolutely prioritised over engine drills. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): APU Engine Failure (All) Engine Shutdown |
| Sailvi767
June 21, 2025, 14:10:00 GMT permalink Post: 11907785 |
Fully fueled with the reported passenger load the 787-8 would have exceeded max takeoff weight. In fact the -8 would only have about 15,000 lbs of available payload with full fuel at max structural weight. In addition given the temperatures reported it’s likely the climb weight limit would be even less than the structural limit resulting in zero payload. If somehow the departure could be accomplished they would be well in excess of max landing weight at Gatwick.
Subjects: None |
| Sailvi767
June 21, 2025, 20:23:00 GMT permalink Post: 11908027 |
Do you happen to have a link to this briefing? The search results for this accident are so terribly messed up with speculation and rumours that I can't quite find it.
Asking because if there is official confirmation that the captain was the pilot flying, as well as official confirmation that he was the one who made the mayday call, is that not another clue pointing towards total loss of AC power (as opposed to thrust merely being rolled back to idle)? In the sense that only the captain's radio is on the battery bus so if he was the one making the call instead of the first officer who should have been monitoring, it could be because he was the only one in the cockpit who could. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): MAYDAY |
| Sailvi767
June 26, 2025, 21:52:00 GMT permalink Post: 11911524 |
Not quite sure if this thread is open again or not.
I wanted to bring something up. Maybe I am out of touch, but the way we have talked about this accident, we have talked about it like it were doomed to be an unsurviveable high energy crash inferno. I, at least, have been guilty of having this picture in my mind. Wasn't this a, relatively speaking, a low energy impact scenario, comparable to Air France 269, SAS 751, BA038, or a number of other accidents including things like the hudson river event, which would have been somewhat surviveable except the impact with the buildings? There looks to be more open areas in close proximity to the accident site that are as big, 150-250 meters, or larger than what either of those others had available or at least used. There have been comments of the docile trajectory of the aircraft being a sign of pilots giving up, and letting automation take over of sorts, but in reality, could it be they just did exactly the same as the crew on BA038 or SAS 751? Except the lack of luck? In connection with this, why would the recorders be so damaged it has taken them weeks to access them. It seems that kind of impact should be well within the envolope for those designs. If out of bounds or order, please delete. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR |
| Sailvi767
June 28, 2025, 12:29:00 GMT permalink Post: 11912472 |
I suspect both recorders will contain the same data. Given the radio transmission after the loss of thrust the aircraft still had at least the emergency electrical bus powered. This should have kept both recorders online. It is however possible given the 10 minute battery backup that Boeing chose to put the the recorders on another bus but that’s not the norm.
Subjects: None |
| Sailvi767
June 29, 2025, 14:02:00 GMT permalink Post: 11913050 |
I see nothing in the video’s to suggest the aircraft was out of control. It was gliding almost exactly as you can expect from an event starting with the gear down and flaps at 5. As the aircraft nears the ground it appears there is a bit of flare to break the rate of descent. That is exactly what you would expect the pilots to do and their only course of action with a dual engine failure at low altitude.
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) |
| Sailvi767
June 30, 2025, 00:40:00 GMT permalink Post: 11913309 |
An admittedly approximate assessment of the airplane's lift-over-drag capability, considering other conditions (head wind, ground effect, actual airspeed vs that required to maximize L/D, etc.) suggests that the engines were providing some thrust in order for it to get as far as it did. Note that simple calculations based on conversion of energy, e.g. velocity and height, to distance are even more approximate in this scenario.
Subjects: None |
| Sailvi767
June 30, 2025, 01:49:00 GMT permalink Post: 11913322 |
OK, from my standpoint as a curious observer, what would their options be? They don't have engines to provide thrust, they don't have altitude to lower the nose and gain speed, and they don't have the speed to pull the nose up and extend the glide? All while trying to troubleshoot the same problem we've collectively taken 2 weeks to not understand. What would you do?
Subjects: None |
| Sailvi767
June 30, 2025, 18:47:00 GMT permalink Post: 11913841 |
Thanks but I want to separate the RAT issue from the engines/thrust issue.
Its possible that the RAT was deployed for other reasons, prior to the engines losing thrust. So, leaving the RAT out of the equation for a bit, do we think there is a sound of engines TRYING to run? Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment) |
| Sailvi767
June 30, 2025, 18:57:00 GMT permalink Post: 11913849 |
I found descriptions on the systems of the 787 were easily discovered online, and while I have no hands-on experience of aircraft related matters, I do have experience in wider electrical theory and maintenance.
THRUST Asymmetry PROTECTION. "For an engine-out condition, Thrust Asymmetry Protection (TAP) reduces thrust on the operating engine to ensure there is sufficient rudder for directional control. TAP reduces thrust when the airspeed decreases below approximately V2 on a takeoff or below approximately VREF on a go-around. Once speed is increased above V2/VREF, TAP increases thrust." From what we know so far, it does seem the engines were not producing sufficient thrust, during a period when it would also be crucial to maintain electrical output for the electro-hydraulic systems and critical electrical loads. Reduced electrical output could explain the failure of the gear to complete retraction, maybe caused by a generator failing at the worst possible moment. If there was an EFATO, the ability of the remaining generators to provide sufficient power might become questionable, as is highlighted with the load shedding system. Other features which are unique to the 787 could be contributing factors in explaining the accident. It is known the 787 will generally employ an extended take-off roll, and a relatively higher V1 and Vr, and also climb out less steeply than other aircraft. Using more of the runway would reduce the margin for aborted take offs. With the evident lack of thrust early in the climb out, and failure to retract the gear, if V2 had not been maintained, the TAP system would have reduced thrust even further. Manually increasing thrust will be inhibited. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EFATO Engine Failure (All) Generators/Alternators Takeoff Roll V1 V2 |
| Sailvi767
June 30, 2025, 23:52:00 GMT permalink Post: 11913954 |
Except:
The longer this takes the more crew actions or lack thereof become the centerpiece of the investigation. More then 1,100 787\x92s have been delivered and flying the last 14 years. Hundreds fly every single day. Not a whisper from any of the aviation authorities worldwide. No emergency AD\x92s..nothing. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank Electrical Failure |