Posts about: "RAT (Deployment)" [Posts: 361 Pages: 19]

With all due respect, based on the videos released so far, it appears the aircraft had no thrust\x97even without considering the sound of a deployed RAT. I could be mistaken, of course, but a flap/gear configuration error doesn\x92t strike me as a likely cause.

In summary,

Flaps were extended, possibly flaps 5 or 15. Looks like it in the video and clearly shown post crash.

Aircraft reached a height of just over 100\x92 AGL (possibly 200\x92 if you compare wingspan to height in videos)

RAT was deployed. Seen on videos and heard conclusively.

Aircraft rotated at \x91usual\x92 spot. Comparing FR24 data from previous flights over the past week.

Aircraft took off at \x91usual\x92 speed. Comparing other flights.

FR24 data stopped being sent shortly after take off. Possibly indicating electrical fault.

Green and white flashing light reported by survivor. Possibly indicating electrical fault.

Gear bogies were at unusual angle indicating Gear selected up and then interrupted.

No smoke or flames to indicate bird strike. (Edit - still debate about this in the video above where the aircraft is behind a building)

No rudder input to indicate single engine failure.


All speculation but hopefully a pretty balanced summary from the thread so far. It would be great if there was more focus now on what might have caused above rather than talking flaps, birds, 625\x92, etc.

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?

In the take off video I think there is a subtle yaw to the right at lift off (the moment it begins being obscured by the building in the foreground). There is then a massive blast of dust on the airfield on the left side of the aircraft as it lifts off. Later video audio suggests the engines were not at full power ( or even operating - just wind noise) and that the RAT was whirring. It also shows the fuselage wheel bogies were tilted forward - so wheels up has commenced - but the gear doors are not open.

Possible sequence: right engine failure at rotation, firewalling of left engine, lift off and positive rate, gear up lever activated, wheels tilt forward, left engine failure, RAT deployed, insufficient hydraulics to Open gear doors to complete gear up sequence, ongoing dual engine failure?

The speed at which there was a complete loss of thrust and electrical power degrading to the point of flickering lights and RAT deployment suggests to me an actual engine shutdown rather than anything linked to auto thrust or fuel contamination. There are not many things which can cause an engine to shut down: LP valves, FADEC incl TCMA, crew action\x85

We're all shouting each other down with two main different theories on why the aircraft lost lift so shortly after takeoff.

1) Incorrect flap retraction causing the aircraft to lose lift and unable to recover the energy in time. (Not unheard of and plenty of reports where this has happened - albeit usually not to a crash).

2) Loss of engine thrust backed up two potential pieces of evidence that back up the RAT was deployed (apparent RAT sound, potential RAT seen on low res video).

It is impossible to know which of these is the case. Considering this summary of memory items is there the potential for a combination of both theories to have taken place?

Inadvertant flap retraction by PNF leading the PF to sense a sink and loss of lift. Pushes the thrust levers forward to the firewall and still the aircraft sinks. PF looking through the HUD and so very much 'outside focused' and doesn't realise that PNF has instead moved the flaps. PF defaults to memory items for loss of thrust on both engines before PNF can realise or communicate to PF what they've done, start switches are cut off which drops the RAT and from that point they're only heading one way. This would satisfy the strongly held belief that the RAT was extended, whilst also following the more likely initial cause of an action slip by PNF starting the sequence, rather than a dual engine failure.

Neurotypically an error in an automatic action will occur when the routine that encompasses that action is changed. Hence babies being left in back seats of cars, and probably a factor for the sterile flight deck rule. Any reason to think that might have been in play here?

I agree it is helpful to seek a consensus on some of these matters.

The most productive responses would be along the lines of:-
(1) I too have read all previous posts and agree that your summary reflects the current consensus,
(2) I too have read all previous posts and agree your summary reflects the consensus HOWEVER I challenge that consensus because... [ [i]EITHER (a) reference to previous post that merits greater credence, OR (b) new evidence supplied],
(3) I too have read all previous posts but I do NOT agree your summary reflects the consensus [explanation required].

It is not necessary for everyone who thinks (1) to say it (although some initial feedback would be useful!). However, if any of the more experienced and informed PPRuNers are thinking either (2) or (3) then it would be instructive to hear that.

FWIW, yours strikes me as a reasonable summary of the best consensus I have been able to discern (as of ~30 minutes ago). There are multiple caveats to each line item, but I presume you've deliberately left those out for the sake of readability, so I'll do the same!

The only comments I would add are:-

- It's a stretch to say the RAT is seen or heard "conclusively". Doubts have been expressed about the video quality and there are dissenting views regarding the audio. If a few more people were able to wade in on the audio point in particular, this could be very beneficial in moving the discussion forward because the presence or otherwise of the RAT is significant to several competing theories.

- On the subject of audio, I am surprised there has not been more discussion regarding engine noise. In the primary eye witness video the (alleged) RAT can be heard distinctly, as can the sounds of distant impact. If the engines were working as expected when overflying the camera and then flying directly away from it, do we really not think the engine noise would be more conclusive, i.e. louder (notwithstanding quiet engines and derated takeoffs)?

Whichever way readers are leaning in the flaps versus power loss debate, surely these two points are pivotal, and we have actual evidence available to discuss?

- Gear bogies: I'm not sure a consensus has yet been reached regarding the angle of the bogies. (I am not personally qualified to comment on this - I am purely saying I don't see a clear consensus just yet among those who are)

- Mayday call: I don't recall seeing a confirmed source for the widely reported mayday. Others have brought this up in the thread but nobody appears to be able to confirm one way or the other. If accurate, its contents are informative. Am I right to presume that you have left it out of your summary due to a lack of confirmation?

The only other way the RAT can be deployed is manually, using the p/b on the overhead panel. Almost certainly this is a highly unlikely action given time & distractions. But it is one possibility that needs examination and elimination in the data.

I don\x92t give credence to any of his recollections. I do find the recorded sound of the RAT quite compelling after watching some other videos of a deployed RAT and hearing from the chap who hears them fly over while testing them every day. The photo of the section of wing in the wreckage with flaps still extended also puts paid to the other main theory, in my mind.

Thanks for the response. All great points you raise.

I simply forgot to mention the Mayday. I think there are enough sources to suggest one was made but I\x92m slightly wary of its content.
The recording and rebroadcast of RT exchanges is illegal in India as it is in the U.K. so we can\x92t be sure until its official release.

Gear bogies - This was also mentioned by Juan Browne/Blancolirio as something to focus on, that\x92s probably what swayed me on this.

I was initially in the gear up/flaps up camp but I\x92ve been impressed by the testimonies of others here, particularly by the poster who\x92s heard hundreds of these overhead and the several videos shared for comparison.

As you say, hopefully we can put most of these topics to bed now (unless there is contradictory new evidence) and focus instead on where Occam\x92s razor points us.

Why the need to make the two theories fit in such a convoluted manner? Inadvertent flap retraction was theorised because people assumed that was most likely to have caused the loss of lift - hardly anyone believed dual engine failure was possible. Now we know that the loss of lift was indeed almost certainly caused by a loss of engine power, why all these awkward attempts to reverse engineer it to still fit the flap retraction theory? People need to realise they are only trying to make the flap retraction theory fit because of cognitive biases. If we had all been told immediately, there was dual power loss and the RAT deployed, no-one would even be considering flaps. Its confirmation bias of past assumptions, that's all.

As has been said many times as well, the landing gear retraction process appears to start as the bogies tilt, and then suddenly stops. Which rather suggests they did pull the gear lever. Based on the videos and the amount of speed the plane lost in the very brief sequence ovents, I'd say that the plane lost power a lot earlier than it would have in your theory.

In my opinion ( and we all know the cliche about opinions ), there are only two plausible explanations.
1. Dual engine failure/damage due to multiple bird strikes somewhere immediately after V2 and liftoff.
Given the suddenness of the situation the gear could well have been overlooked by the PM who would be checking out the engine parameters only at this point in time. Flaps were in 5 position. No doubt about that.
Take off thrust used was for Optimum thrust
( meaning minimum thrust for take off given runway and environmental conditions ). That accounts for the full runway length being used. This is policy. That means minimum thrust used for take off to meet 2nd segment climb gradient at almost MTOW.
Loss of total thrust, RAT may or may not have deployed. At 650, AMSL no chance of any relight or turn back. Rest is history.
This also corresponds to the thud heard by the survivor about 30 seconds after takeoff.

2. Loss of thrust in only one engine and degraded performance in the other. Again, due to bird strike. Thereby not allowing even level flight.
Gear staying down could have been overlooked by mistake OR left down intentionally forseeing an impending ground contact by PIC and trying to minimize damage to his airplane.
Eitherways it added to additional drag and if anything, only accelerated the process of ground contact.
Given the above conditions safe flight would have been close to impossible. If not completely impossible. He neither had the airspeed not the altitude to make a 180 or even look for a safer place to put her down.
Refer the last Concorde flight/crash.

A very very sad day for aviation indeed \x85 🙏

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.

How would 'all the power come off' at 150ft AAL when the Autothrottle would still be in HOLD mode (until 400ft) and therefore be unable to move?

And should't a genuine B787 captain know this?

No argument on the flaps.

The engines, however: yes they take a long time to wind down fully , but they don't take long to stop providing thrust if you shut them down or cut the fuel (or indeed have a bird strike). I don't understand why you consider a loss of thrust to be an impossible hypothesis.

There's also a still image above which appears to show a deployed RAT; that's even if we discount the sound track, which might indeed be something else than a RAT, and ignore the sound of the crash being clearly audible despite the lack of engine noise earlier in the video.

People should be made to read this before posting!

Please read this thread first before asking a question, it has been answered several times.
Yes, the RAT will deploy automatically in the event of a loss of both AC Busses, both engines or all hydraulics.
It can be deployed manually via a guarded push button switch on the overhead panel.

Combining all the bits and pieces of info from this thread so far, IMO we can theoretically sequence it thus using the video from the left:

00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.

if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?

with condolences to the families and people affected.

EVERY RAT automatically deploys under the right conditions usually loss of all electrics or all engines. The C-5\x92s RAT dropped when 3 generators \x93in a row\x94 (1,2,3 or 2,3,4). I can\x92t remember the Global but I thinks its loss of both AC generators.