Posts by user "Aerospace101" [Posts: 19 Total up-votes: 86 Pages: 1]

Misselection of flap, erroneous TO Performance data, dust = overrun, bird strikes\x85.all unlikely as none fit the evidence; the engines were very quiet.

The clearest bit of evidence is the RAT deployment. As someone else pointed out gear bogey position indicates Gear UP cycle had commenced.
So the most evidenced sequence of events was rotation, positive rate = gear Up; \x85.catastrophic Power Loss. Flickering cabin emergency lights and Loud bang reported by survivor (was this heard RAT deployment or another system?).

The 787 has some unique electrical/mechanical and air systems. Previous flight had issues (reported by passengers).

So the root cause of the Power failure must be down to when either the 787 gets airborne (weight on wheels switch) or when Gear selected Up. I wonder if any 787 drivers could elaborate on what electric/hydraulic/air systems are affected at the very point of wheels up or gear up ?
I\x92m wondering if the electrically powered cabin pressurisation system is affected at wheels up?

How is misselected flap still being discussed? Misselected flap does not cause gear retraction to cease nor cause the RAT to deploy. Both of which are (subjectively) evidenced in the videos. What is the supporting evidence for misselected flap?

Yes absolutely. 100% catastrophic loss of power when getting airborne. No evidence for bird strikes\x85no severe eng damage symptoms in the videos, no mention of birds in the mayday\x85

they\x92ve gone TO power all the way to rotate, no power issues, no eng fuel issues, but as soon as its wheels off they lose all power. That can\x92t be coincidental. TCMA certainly fits this scenario especially with ground/air logic.

I see the YouTube influencers are now shifting their speculation to the RAT deployment and loss of thrust theory.

we have to look at the limited evidence and stop
speculating on things that have no evidence yet (like the flaps). Aside from RAT deployment the other red flag here is the partial gear retraction. On the 787-8 the bogey will tilt forwards first, before gear doors opens. Not to be confused with the -9 and -10 variants where the gear doors automatically open after liftoff.
This is an important distinction because the Center hydraulics which is solely electrically pump driven (not engine) only had enough power to tilt the bogey, not open the doors.

so the question is, did the electrical failure (and loss of Center hydraulics power) happen before or after loss of thrust?

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

I’m 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’s 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’s 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’s 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’m seeing lots of social media posts which suggest the forward tilt means gear was in retraction and I don’t 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?

The RAT provides hydraulic power only to the flight control portion of the C hydraulics. Wing and tail flight controls only. Non return valves prevent power to other C hydraulic powered systems like the gear.

The RAT provides electrical power only to critical flight instrumentation (mostly Captains), navigation and communication. The same critical equipment that the Battery will provide. If all electrics was lost, the main Battery would provides standby power until RAT is fully deployed. The RAT electrical power would not be able to power C hydraulic electric pumps.

Did you not read my full post?

How does this explain the unusual forward tilt of the gear trucks as seen in the roof top video?

I appreciate some don\x92t want to speculate on the RAT deployment or APU auto start until further evidence, but the gear truck tilt is a massive clue to a non-normal hydraulic issue, most likely caused by electrical power problems since C hydraulics is only electric pump powered.

That is one conclusion (which I now suggest is unlikely), because you are assuming:

1. The hydraulic failure happened exactly when the truck had tilted forward but the split-second before the gear doors could open. That exact timing seems too coincidental.
2. The crew selected Gear Up. We have no proof of this. I speculate the crew never got as far as "Positive Rate...Gear Up" because they were already engrossed in flying the aircraft and processing their thrust problem. If an electrical problem had developed (as evidenced by the RAT deployment) the flight instrumentation would have been flickering and a flurry of silent master caution alerts would be very distracting.

I suggest it's more likely that the truck remained in a forward tilt from the takeoff run because the hydraulic failure happened prior to rotation, therefore keeping it in this unusual position. This answer does not rely on the gear lever position either. It also insinuates that their hydraulic problems occurred probably between V1 and VR. See my earlier post .

I still consider the forward truck tilt is a massive clue to a C system Hydraulic failure prior to wheels-up, which must have been caused by loss of electrics (since C is solely electrically powered), so I am still wondering if hydraulic failure happened before or after the loss of thrust.

While thinking about the consequences of a total hydraulics failure around time of rotation (caused by a suspected dual engine failure), here is a new observation. I searched the previous threads to see if anyone lese had noticed it.





In the rooftop video, as it's just approaching the treeline, there are spoiler deflections visible just behind the engines on each wing.

With a total hydraulics failure, the pilots control column using direct wiring, will only control this spoiler pair and the stabiliser. The RAT does not control this spoiler pair (hydraulically), only the most inboard spoilers pair. Its an interesting observation because it means this spoiler pair were being deflected electrically, either by the battery or RAT. But if the RAT provides emergency C hydraulic power why didn't the RAT powered spoilers deflect instead? Does this mean the RAT was unable to provide emergency hydraulic at such low airspeed?

I think this also re-affirms the critical loss of power (dual engine failure), and rules out many other theories. It tragically lost all power, both engines, all hydraulics and electrics (apart from battery and RAT).

I am wondering if anyone else has noticed other flight control deflections?

(Tried posting link to youtube but unhelpfully frames entire video)

I too watched his explanation with interest. However I believe he is not considering the possibility of C hydraulics failure prior to wheels lift-off, because I speculated this is the more likely reason the gear trucks remained in a forward tilt position, see my earlier post here . I believe the crew never got as far as calling for the Gear Up... many possible reasons for this, flickering instrument screens during the electrical switchover to battery power, flurry of EICAS messages. For any of those things happening around time of rotation, I would be advocating delaying gear up decision until safely climbing away above AA and as a crew you have chance to discuss safest course of action. Not putting the gear up shouldn't kill you.

Point is the gear truck tilt is a clue of a C hydraulics failure, but we cant determine if hydraulics failed prior to wheels off runway or prior to gear doors opening in retraction sequence.

Loss of only C hydraulics is not enough to auto deploy the RAT.

No, very unlikely the pilots lost all control. In a total power failure (hydraulics and electrics) the pilots can control roll (by a specific spoiler pair) and pitch through the stabiliser. All electrically powered through wiring direct to control column.

It's possible the RAT was not providing correct power in the last moments, remember RAT provides Hydraulic (C system flight controls only) and Electrics. The evidence is the spoiler pair deflection behind the engines prior to impact. See earlier post . . That specific spoiler pairing is only controlled by electrical power (directly connected to pilot control column). We should see other flight control deflections if the RAT was powering hydraulics. In the final moments I would speculate the flight controls had only emergency electric power from the battery.

Very subjective, and I agree it it could look like a slotted gap between the wing and flaps, except the shadow is confined to exactly where that spoiler pair is located. You don't see it where the rest of the flap is. It would be good to hear other opinions about what we are seeing here . Is it wing, flap, gap or spoilers?


I don't understand your point here. The RAT hydraulic powers very specific flight controls like the stab, rudder, outboard ailerons and one specific pair of spoilers - the inboard most spoilers. Have a look at this schematic (at 3:55) youtu.be/DFbOLNduutI?si=siPnQ9oHMbLgp64K&t=235 (not publishing link as it fills the frame). The spoiler pair I mentioned above (visible in the video) are only powered by L hydraulics and electrical. Assuming L hydraulics was lost by dual engine failure, then this spoiler pair can only have been electrically powered...hence the conclusion it's either powered electrically by the Battery or electrically powered by the RAT. That spoiler pair is not connected to the RAT hydraulics.

I thought this was a very good point. There are some detailed posts discussing the TCMA patent including this post . Is it possible the TCMA software functioned exactly as specified, and the issue is input data into TCMA?

In a total electrical failure, when the system switches to emergency battery power, how are input variables like rad alt and wow switches processed? (these were inputs someone mentioned on the 747-8, have the TCMA inputs been identified yet?)

I speculate the gear truck forward tilt is a symptom of a C hydraulic failure caused by a total electrical failure around the time of VR. Once they got 10 deg nose up on the rotation, with a total electrical failure, could the FADEC receive erroneous rad alt or wow inputs, and how would TCMA handle these inputs in the transition from ground to air logic?

What is baffling is the simultaneous nature of the suspected dual engine shutdown. There is no obvious asymmetry, with the flight path or rudder movements. If the engine fuel control switches had been manually cut one at a time, there should have been some visible flightpath change or flight control response. Something happened to both engines at exactly the same time.

For those postulating the RAT was not deployed, what counter explanations do you have for the following clues?

• Distinctive RAT sound in the rooftop video, audio analysis here .
• RAT visible in rooftop video, example in this image .
• APU door open suggesting auto APU start, suggestive of a full electrics failure (one of the criteria for auto RAT deployment)
• Loss of ADSB data suggestive of a full electrics failure (one of the criteria for auto RAT deployment)
• Unusual gear forward tilt position, suggestive of hydraulic failure and/or full electrics failure (one of the criteria for auto RAT deployment).
• Loss of all thrust, ie dual engine failure (one of the criteria for auto RAT deployment)

The 787-8 gear goes through the following movements on TO:

1. During rotation all 4 main wheels on each gear truck stay on the runway, the gear acts as a pivot point for the rotation. Effectively the gear truck is in a forward tilt as it is no longer parallel to the fuselage.
2. Once As the wheels lift off the runway, the trucks tilt rearward (this is the normal extended gear in air position, like on approach)
3. When the pilot commands gear up, the gear retraction sequence begins, specific to the 787-8, the gear trucks tilt forwards first, instantly followed by the gear doors opening.

See this post which discusses the forward tilt is either caused by process (1) or process (3). I suggest (1) is more likely than (3).

The issues with the "they shut down the wrong engine" theory:
1. No asymmetry evidence with flight path deviation. No roll, no yaw effects
2. No rudder inputs visible.
3. No crew should be doing memory items below 400ft. Boeing requires each crew member confirm together memory item switch/control selections.
4. Non-normal gear truck tilt position, a one engine failure should not affect the C hydraulics. As per (3) gear would be selected Up before any memory actions.

The evidence so far is an almost simultaneous dual engine failure, which rules out alot of other theories.

The gear tilt position is not definitive evidence crew had selected gear up. I've speculated another cause for this non-normal gear tilt is that C hydraulics failed around time of rotation. This would explain the gear remaining in the forward tilt position. There are reasons why the crew may have not selected gear up, see earlier post. Therefore we cannot determine wow or air/ground logic from an assumed gear retraction.

Without going round the hamsterwheel again does anyone have an actual reference for this? Because I've gone back through each of tdracer's very informative posts about this see here and there is a discrepancy in the two points he makes below in adjacent posts. Is tdracer talking about the same HPSOV valves? Can anyone confirm that with both AC power loss and and a temporary DC power loss there are no critical engine related shutoff valves that will fail safe (unpowered) in a closed position?