Posts by user "njc" [Posts: 8 Total up-votes: 13 Pages: 1]

Originally Posted by Magplug

Speaking as a B787 Captain..... There is so much rubbish and stupid suggestion being written here.

This aircraft was airborne for a grand total of 22 seconds, half of which was climbing to no more than 150' aal.

- No Flaps? Due to the setup of the ECL it is physically impossible to go down the runway without some sort of take-off flap set. The T/o config warning would have been singing it's head off. Despite assertions to the contrary I have seen no video clear enough to detect a lack of flaps.

- RAT out? Almost impossible, I have seen no quality footage that definitively witnesses the RAT being out. Those who think they car hear a RAT type noise might be listening to a motorcycle passing or similar. It takes a triple hydraulic failure or a double engine failure to trigger RAT deploment. They happily went through V1 without a hint of rejected take off so as they rotated the aircraft was serviceable. These are big engines, they take a long time to wind down when you shut them down. I have never tried it however engine failure detection takes 30s or for the aircraft to react and they were not even airborne that long.
- Flaps up instead of gear? The B787 flaps are slow both in and out. Given that the 'Positive rate' call is not made the second the wheels leave the ground, a mis-selection of flaps up would not cause any loss of lift for at least 20 seconds, by which time they had already crashed. I believe the gear remained down not because of mis-selection but because of a major distraction on rotate.

Discounting the impossible, two hypotheses remain:

1. Invalid derate set through incorrect cross-checking. Trundling down the runway takes very little power to reach Vr. It is only when you rotate that you create more drag and discover that you do not have sufficient thrust vs. drag to sustain a climb. Or....
2. Put 200' as the altitude target in the FCU. Immediate ALT capture and all the power comes off. PF is still hand flying trying to increase pitch but is already way behind the aircraft.

It could be after this that Boeing are forced to review the B787 practice of exploring the very edges of the performance envelope.

Originally Posted by mechpowi

Would it be possible to determine from the video audio wheter the fan noise (RPM) maches with a normal take off? I know that\x92s a long shot and I\x92m already very impressed by your work, thank you for sharing it.

Originally Posted by aeo

- The bogie could be explained by the Flap/Slat priority valve giving priority to the flaps if the PM suddenly realised his mistake and quickly put the flap lever back to the TO position and then selected the gear lever to UP. Those systems are both heavy hitters and would’ve sucked the life out of the CTR hydraulic system pumps.
- There is no way loss of AC (alleged RAT deployment) could've caused a spool down of both engines. Think QF A380 incident in SIN - The entire #1 engine wiring harness in the wing was completely severed and yet it continued (by design) to run at its previous thrust setting. They had to shut it down using a fire truck!
- History and design would dictate that a big 180 minutes ETOP’s twin such as the 787 having a dual engine failure or significant power loss at such a critical phase of flight would be a billion to one chance at best. Only the Airbus A400 had a software issue causing all 4 engine fuel shutoff valves to close causing it to crash killing the flight test crew - But this was during its development and flt testing.
- Wide body twin’s delivering in the region of 60,000 to 115,000 lbs of thrust at TO rarely , if at all, flame out from multiple bird strike(s) like the baby Bus’s and Boeing’s. If anyone has seen the frozen chickens at TO power video would know what I’m talking about. And the Fan Blade being ‘blown off’ as well. In both cases the engine was was able to maintain full TOGA thrust for significantly longer than the AI aircraft.

Originally Posted by Sailvi767

Thrust loss from a loss of fuel flow is near instantaneous.

Originally Posted by MaybeItIs

I'm still sticking with "Major Electrical Fault" as my most likely cause, and this adds to my suspicions.
[snip]
Anyway, there MUST be ways that the redundant power supplies can be brought down, simply because, to have a critical bus powered from a number of independent sources, there must be "controls" of some sort. I don't know how it's done in the 787, but that's where I'd be looking.

As there is a lot of discussion already about how the bogies are hanging the wrong way suggesting a started but failed retraction operation, and it's now confirmed that the retraction would normally have taken place at about the point where the flight went "pear shaped", I'm going to suggest that the two things are connected. More than that: I'll suggest that the Gear Up command triggered the fault that caused both engines to shut down in very short succession. Nothing the pilots did wrong, and no way they could have known and prevented it.

Originally Posted by BugBear

If #2 failed and #1 got pulled, how bout dat

Originally Posted by Ornis

Given it was close to the ground at the time of failure, is it possible a problem raising the gear could allow automation to cut fuel to both engines? (According to this thread, TCMA uses weight on wheels and radar to decide if aircraft is airborne.)

Originally Posted by tdracer

The 'good' news is that even a cursory check of the FDR will indicate if TCMA activated, so we'll soon know.

Originally Posted by Screamliner

So one thing to keep in mind, the RAT can be deployed manually, but also comes automatically when certain conditions arise, everybody here is assuming it\x92s only on dual engine failure but there are 4 more conditions that trigger the RAT

Originally Posted by Stivo

Am I understanding that you are saying that the noise on the video identified as a RAT has a Doppler shift that matches plausible values for height and speed? That seems pretty conclusive to me that it is a RAT.