Posts by user "dragon6172" [Posts: 10 Total up-votes: 23 Pages: 1]

Originally Posted by The Nutts Mutts

The more i watch that video it really looks to me like it used the entire length of the runway before finally struggling into the air without enough airspeed to maintain flight, crashing nose-high just seconds later.

Originally Posted by culzean12

The only thing that is clear from the footage is that the gear remains down. Which has led to the theory that the loss of lift is a result of the flaps being raised by mistake.

However a deployed RAT would be compelling evidence of dual engine failure or shutdown.

Another explanation for the gear remaining down could be startle/distraction caused by engines rolling back at around rotate or liftoff.

Originally Posted by EDMJ

In this video of a 787 take-off, first the inner main landing gear bay doors open, and then the bogies tilt downwards. In the first video of the crash, the bogies appear to be tilted downwards but said doors remain closed?

Originally Posted by gav_20022002

As for the dust on rotation:
I’m inclined to go with wingtip vortices, looks like a 45m wide runway with 7.5m shoulders giving the sealed surface a 60m width. The 787 has a 60m wingspan so if he’s bang on the Centreline then the wingtips are right on the edge of the sealed surface. I’ve seen all kinds of aircraft including 737’s and even Q400’s lift dust off the edge of a 30m wide runway with 7.5m shoulders, A330’s on a 45m runway with 7.5m shoulders lift dust and debris up and they were no where near the end. Pretty sure there were data points posted earlier that shows they rotated with 4000ft remaining.

Not a professional pilot but I’ve possibly spent more time than most physically on runways in my line of work including a lot of displaced thresholds and sitting on the centreline observing aircraft come and go

Originally Posted by Capn Bloggs

Plane crash near Ahmedabad..


Was explained a couple of pages back: 60m wingspan, 45m runway, wingtips overhanging the dirt.

Originally Posted by syseng68k

FrequentSLF: I would be more suspicious of the hardware that feeds TCMA. Rad Alt sensing could be in error, but possibly more likely is the hardware that senses weight on wheels. May be position sensing microswitches, or perhaps gear oil pressure, but would assume redundancy, eg: two sensors per leg, then some sort of voting logic on the sensor set to find faulty hardware.and make a decision. Doubt if the software is at fault, but is there a delay between sensor output, and command to shutdown the engines ?. Alluded to doubts upthread, but I think the post was deleted. Question: Should TCMA really have the absolute power to auto shutdown engines at all, without some sort of confirmation ?.

Originally Posted by Aerospace101

I previously speculated the forward truck tilt was proof the gear had been selected UP and the retraction sequence was interrupted.

I\x92m not so sure now and believe there is a different conclusion from this non-normal gear position.

In normal retraction sequence the gear doors open almost instantaneously after the forward truck tilt. It does seem coincidental the tilt was completed while no indication of the doors opening is visible on the rooftop video, which would suggest hydraulic failure at that exact moment; this precise timing of interruption in the retraction sequence feels unlikely. So is there a more likely answer for the forward truck tilt that does not involve movement of the gear lever?

I suspect it\x92s more likely that C hydraulics lost power prior to rotation, as a consequence the truck could not tilt rearward during rotation as it normally should. Therefore it\x92s probable it always stayed in a neutral or forward tilt position from the take off run until we see it in the rooftop video. If the gear was behaving normally, and the crew had omitted to retract, it should be hanging rearwards. Watch any 787-8 takeoff video and you can see at rotation all 4 main wheels stay on the runway as the aircraft rotates. Just after wheels up they tilt rearwards. It\x92s a very subtle position change.

If the gear was always in a neutral or forward truck tilt position then this undermines the theory that retraction sequence was interrupted. It insinuates the C hydraulic and electrical failure happened prior to main wheels lift off.

For this reason I believe we cannot assume that gear UP was selected nor that retraction was interrupted. I\x92m seeing lots of social media posts which suggest the forward tilt means gear was in retraction and I don\x92t believe it was now.

I think the truck tilt position is key to understanding the timeline of system failures and whether the automatic RAT deployment was triggered by power failures or engine(s) failure. The question remains, did loss of center hydraulics happen before or after loss of thrust?

Originally Posted by tdracer

You'd be half right (or if you prefer, half wrong). Each channel of the FADEC has its own thrust lever position resolver. In other Boeing aircraft, there is a single resolver per engine, with dual electrical coils (i.e. electrically isolated but mechanically connected). But in order to go for full compliance with a (in my opinion) rather extreme FAA position regarding 'single failures' and 25.901(c), the 787 thrust lever actually has dual load paths, feeding to different thrust lever resolvers for each channel.

Originally Posted by bbofh

Most pundits have identified the gear-tilt as evidence that only the centre electrically-driven pump can do the gear-tilt if the engines' other two hyd systems are suddenly both in QUIT mode (which accords also with the instant RAT deployment and loud noise heard by the sole survivor) - and an ensuing transition from climb-out to a deadly sinking and commensurate attitude change for speed maint.

Originally Posted by OldnGrounded

Thanks. Do we know that these are monitored by TCMA for air/ground state and if so, do we know the logic used to make a determination based on those inputs? Alternatively, do you know where we should be looking for those answers?

Originally Posted by OldnGrounded

Thanks again. Yes, I checked the MMEL too. It also says that the aircraft may be dispatched with one of two TCMA functions operational.

Originally Posted by Xeptu

It doesn't have to be both engines. The loss of one engine with the gear down will still produce the same outcome.
That still doesn't explain the bogies stowed position for retraction unless there was a total hydraulic failure, which could only occur if the aircraft was despatched with an unserviceable hydraulic system on the live engine side. Which in any case would be a no no.