https://www.reddit.com/r/aircrashinvestigation/s/6NRIuRywZ8Reddit can't embed not sure why
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For the take-off config warnings. It is correct that you would hear an audible warning that could not be shut off. So the crew would know that they were not properly configured, which reduces the likelihood of no flaps / no slats at all. However, if the performance inputs were wrong (flap setting too low, inadequate thrust in case of a derated take-off and lower V speeds), they may not have had those warnings. It is worth noting that the accidents with no flaps result in an unstable airplane straight after lift-off. In this case the aircraft seems relatively stable and is able to climb for the first few seconds after lift-off, which to me could point more to a loss of thrust scenario.
Flap/Slat position – I don't think there were no flaps at all in flight. A flap setting of 5 or 15 is barely visible for a 787. In video 1, as the aircraft flies past, it does not look like a clean wing to me. Looking at pictures of the crash site with the wing, slats are deployed. However, this could be due to the autogap function - “at high AOA, autogap fully extends the slats to increase the wing camber, thus increasing the lift and margin to stall”. Thus, may not reflect the actual setting of the flaps/slats from the start of take-off. Also some of the experts in the media don't seem to have really done their homework.
I’ve seen reports that the aircraft was in a poor condition due to the state of its cabin. I think its important to remember that cabin furnishings and cleaning has nothing to do with the aircraft’s ability to fly, and is more of a customer service aspect (although I understand it’s a poor reflection on the airline). The correct maintenance program to keep the aircraft airworthy is a separate need that airlines must demonstrate to their respective airworthiness authorities.
Most important part, I have found some more evidence which strongly indicates a dual engine failure/flameout.
The only survivor’s account in a more recent video (NDTV); He mentions that 5-10 seconds after liftoff that the plane seemed to be ‘stuck’ [I think that is referring to the obvious deceleration as seen in the CCTV video which would be fully explained by a significant loss of thrust]. Then he said that a bit later, ‘green and white’ lights came on [if correct, this would likely be the emergency lighting system, especially as he was sat at the emergency exit row with the signs close to him]. This fully tracks with a dual engine failure [the emergency lighting which would be armed at that stage of flight. would automatically switch if you lose the normal electrical system]. In this interview he does not mention the loud bang as reported earlier. The poor man is obviously in shock and I wish the media would give him some space.
The distinctive sound of the RAT. There is a noise at the start of video 1 (on the versions with the original noise), which does not correspond to engine sound. This is almost certainly the RAT, based on another video of a 787 flying past with the RAT deployed. Based on the trigger conditions of the RAT, one or both engines and the electrical system would not have been working.
I forgot to mention the landing gear retraction also (not considering the drag aspect, but the ability to even retract the gear). I think for a split second you can see the main gear starts to retract but then it stops, this is around the time that there is no longer positive climb. This would make sense in case of a dual engine failure and the switch to emergency systems means only a gravity gear extension would be possible (but no hydraulic power to actuate LG doors and retract the gear itself).
The reports of what the pilot communication with ATC was exactly, I’m not convinced is from an accurate source. But the Mayday call alone as I said before, shows the crew were aware of a desperate situation on board. And in case of a dual engine failure, they wouldn’t have had the chance to do much at that stage.
This would be unprecedented for a large commercial aircraft to have lost power completely on take-off. This is a catastrophic condition which would leave the crew with no option. The residual energy will only allow the aircraft to cross beyond the airport perimeter and inevitable crash land soon after, with no chance of return. The is why engines and aircraft have robust designs and interfaces to each other to avoid common mode failures. Independence is maintained between the two engines and their source of fuel and the engine feed system etc. Systems and their associated software that are involved in critical functions are designed to the highest Development Assurance Levels (DALs for those familiar) and have detailed safety assessments. So, it is difficult to comprehend how this may have occurred. The chances of both engines having some sort of internal failure event (same type or different) at a similar time is almost impossible [in the absence of a common external event like a bird strike, debris ingestion, volcanic ash etc...]. It is even more difficult to comprehend given the engines worked fine at the start of the take-off. And the aircraft had successfully completed a flight just before this sector with a 2-3 hour turn-aorund.
I tried to dive a bit deeper into some causes of dual engine flameout, but specific to this accident:
Fuel exhaustion >> Not in this case. There was plenty of fuel on board (massive post-crash fire)
Fuel Supply Interruption >> Unlikely for both engines at the same time as systems are redundant. 787 Fuel System has 2 pumps in each wing tank and 2 in the center tank. Engines also can suction feed if all pumps fail (available in this case as the aircraft was at ground level, suction feed will not work above certain altitudes). Something similar to BA38 but no ice in this case?
Fuel Contamination / FOD in tanks (leading to supply interruption) >> This is more likely than a pure system failure to deliver fuel to the engines. Contaminated fuel can have unexpected consequences on the fuel system and engine fuel delivery to the combustors (see Cathay Pacific Flight 780 for example)
Software bug (engine control) >> Very unlikely given this is a critical function. Numerous protections should be built for this.
External common event: Bird strike, FOD, ice, rain/hail, volcanic ash etc >> There is no evidence of fire, smoke, or debris, or backfiring from the engines (or other visible external damage). The CCTV covers a fair section of the take-off roll with not much being observed to indicate catastrophic failure.
Maintenance error >> It is difficult to think of a maintenance error that would affect both engines but is possible.
Other causes or contributing factors >> Manufacturing flaw specific to this MSN, Design flaw. Or could be really be a one in a billion occurrence that could not have been predicted.
This post has been edited by ZeneticX: Jun 14 2025, 11:32 PM 
Jun 14 2025, 05:36 PM
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