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

The Mayday specified loss of control and engine failure.

TD, in this case, the RT call suggests we are a grand total of 1 choice, and that goes to a fair likelihood that a fleet wide grounding is in the offing. Adding system complexity dependent on sensor reliability has bitten us all in the past and will do again, and I have a bad feeling that is where we are at with this. The SSA guys will be working overtime, but this has had the hall marks of being a bad sensor/system event from the outset. Am laying bets that there will be a fleet wide grounding in the next 3-4 days, if not sooner. Inadvertent GA thrust after landing has occurred before, (had it on a B744 myself), and it is curious but straightforward to handle.

Several hundred posts ago, a link to a PPrune thread re 787 RAT deployment was posted. I am sure everyone posting has at least seen if they have read the thread....

I apologise, if my thoughts have already been posted - please delete if this is the case, I cannot find them in the main thread though

None of us know if there was no engine failure, single engine failure or double engine failure.

If RAT was deployed, we do not yet know whether it was automatic or manually deployed by a very experienced captain because "We have no power. What harm can it do now?" (Electrical power, not thrust) Would the Captain also elect to start the APU in the few seconds he had?

In the thread re 787 RAT deployment, some one states that a single engine failure, due to the small rudder size on 787-8, automatically throttles back the remaining engine as the rudder will not be able to correct the course. I am not clear about the guards around this - be they height restrictions, speed restrictions or % of power delivery. If there are any guards in the software. It may have been stated and I missed it or didn't understand.

However, as someone involved with critical software design & development, if the generators were "playing up", which is highly possible given passenger observations on previous flights, could there be a window, if the aircraft experienced a problem with say no 1 engine ( suggested in video "analysis" despite the aircraft tracking right ) whereby the loss of electrical power triggered the software to "throttle back" No 2, and that again limiting any recovery of No 1, if the generators on 2 didn't perform/react as planned. Software always has holes.

The primary flight deck screens have battery backup - but do they lose power when the main buses go offline - and/or again when the RAT delivers? Or is it seemless? Previous posts mention both scenarios but with no answer. Are there flickers, resets, reboots? All distracting at best and time limiting at worst.

I think a pertinent point posted earlier, was that the problems seems to have begun with "gear up", a lot of load on the electrically driven, hydraulic pumps.
Seemingly started, but obviously not completed.

I believe the 2 guys sitting in row 0 dealing with this, were just passengers from the moment it left the gate - for whatever reason. The mayday call, by whichever pilot - although no transcript officially published - was probably a last ditch attempt to alert ATC asap to a situation with a clear outcome. Very sad. It is bad form to point the finger before any useful facts are confirmed.

So, I suspect generator problems & a hole in the software and/or logic due to timing issues caused by generators appearing to be on/offline -maybe rapidly - restricting thrust by design..

Just commenting on the earlier acoustic analyses of RAT deployment conducted by Kraftstoffvondesibel and myself.

Firstly it will be clear that we posted our respective audio analyses about the same time. There was no collaboration I assure you, and in fact I'd been waiting all day to see if someone else with more recent or pertinent experience than me would do something. When I hadn't seen anything I spent a little time and came up with what I did, however I think Kraftstoffvondesibel's work is probably more useful than mine given their specific plot methodology and that they included a non-RAT 'control' pass. I was in the process of acknowledging this when the thread was closed; late at night for me which is why this post is now some hours on.

At the time I posted I was fairly circumspect for the reasons given but, with the similarities between our results and along with some other detail that's come to light in PM, I am now more persuaded that the acoustic print we both observed is most likely to be from a RAT (although until this is confirmed a question must necessarily remain).

FWIW, and in part answer to a later post enquiring about the noise of a RAT dropping into position, this also aligns somewhat with the survivor's apparent observation of a noise ('bang'?) prior to impact, and an earlier post by DaveReidUK stating that RAT deployment results in a 'humungous' bang.

FP.

Do not discount the mistaken early flap retraction scenario too easily. Mull on this:

PF commanded gear up on attaining positive rate of climb, fixating on the HUD.
PM mistakenly raise flap lever from 5 to Flap 1 gate. Thrust reduced to Climb Thrust. Landing gear remained deployed. Massive loss of lift misidentified as loss of thrust. If any one pilot just had a dual engine failure scenario on a recent sim ride, brain and muscle memory would jump to loss of thrust in dual engine, prompting them to accomplish the recall memory items which called for both engine fuel control switches to CUTOFF and then RUN, and physically deployed the RAT.

There would be immediate loss of thrust with the engine taking time to recover , if at all, at such low airspeed!
The rest is left for Ppruners’ imagination.😖🥴😬

Further to the audio analysis of a deployed RAT; given an audio print, known noise source [RAT] frequency, location of a receiver and relative location + direction of moving object, and using the principles of doppler effect etc, it should be possible to calculate [ground]speed of a passing aircraft.

Thus, having been informed that the source frequency of a RAT is 145Hz (thank you that person - please ID yourself if you wish), and with regard to the [assumed] RAT acoustic print available for AI 171 we are close to being able to determine an approximate airspeed during descent (given the video from which we get this acoustic data appears to start during the descent).

There are several variables in play here that we don't know exactly (the positions of observer and aircraft, height agl of observer and aircraft etc), and some I will ignore for the moment (effect of air temperature/pressure for example) but if one makes an educated assessment from the visual cues in the video I calculate an initial relative airspeed of circa 120kn. Necessarily this is an extremely rough number, in fact the range (making various positional assumptions etc) appears to be between ~100kn to ~150kn, but if it turned out be either side of this I wouldn't be completely surprised.

As with the initial audio analysis to determine whether a RAT was deployed or not I offer this for those to whom this sort of data may be important. Not sure if it's of any real use or not, and I wouldn't hang your hat on it, but here it is in case it assists. Should it matter I expect some sort of corroboration could be obtained by making an assessment of vertical speed from the variously available videos and extrapolating from there.

My previous caveats over veracity of source data etc remain.

FP.

I'm sure it's not the case, but if an attempt was made to raise the gear with the pins still fitted, you would see the main gear doors open as part of the normal gear retraction sequence.

This applies equally to a normal gear retraction: the centre hydraulic pumps must have stopped very early for the trucks to be in that position on an "interrupted" gear retraction, with the main gear doors still closed (and presumably locked). Seems unlikely.

The tilt and stow positions are definite hydraulically achieved positions of the truck positioner actuator. I don't think the actuator is spring-loaded to the stow position on the 787, though perhaps they move that way given my earlier statement...

Alternate extension appears to rely on the truck positioner remaining in its previously "positioned" state - stowed - where it has been sitting cold, unloved and unpowered since the gear was previously retracted. Like other Boeing types, the wheel well has some bars to stop the truck moving while it's up and stowed.

It's remotely possible the main gear priority valves may have prevented more gear movement in the absence of good hydraulic pressure - however this wouldn't stop the nose gear from operating, so not likely.

I keep reading this theory and I'm baffled. You think the PF is going to attempt a dual engine shutoff and relight during the initial climb based on a hunch that the engines have quit, all without even a sideways glance to see what N1 is or a short word with the PM?

No evidence of engine failure

No evidence of RAT deployment from a poor image.

No evidence of electrical failure.

The teams of lawyers in the UK representing 53 grieving families will be working over the weekend to sign up said families to a class action.

​​​​​​​This is going to get messy.
​​​​​​​

No evidence of engine failure - Depends how you look at it, the sinking and inability to remain airborne points towards a possibility

No evidence of RAT deployment from a poor image - There absolutely is, you're not following fully I'm afraid. There's a brilliant video by Juan Brown where he compares the sound of the plane passing with that of an American 787 on final with the RAT deployed. Identical sound. The image is not conclusive but I'd wager a bet on it.

No evidence of electrical failure - Except, mention of flashing lights inside cabin moments before by the sole survivor and (sorry old boy) - The RAT ;-)

The teams of lawyers in the UK representing 53 grieving families will be working over the weekend to sign up said families to a class action - Well....

​​​​​​​This is going to get messy. - Agreed
​​​​​​​

Dont be afraid. I am following along. There is no evidence. Can you vouch for the authenticity of the audio recording? I cannot see a RAT in that image only a blur.

I tell you what I am watching closely, the words and subtle meaning in the press conference of Civil Aviation Minister, Shri Ram Mohan Naidu, who has set up a “special high level committee” to oversee the investigation of this “incident.

A little odd given they have the DGCA and AAIB in place, dont you think?

He indicates they are to report within three months.

It is now 48 hours since the EAFR was recovered. A small group of people know the answer NOW.

1. The original video, not the video of a video, has the distinctive audio signature of a deployed RAT.

2 That video shows something dangling down where the RAT is located.

3. There are no typical engine sounds heard.

4. The flaps are extended in that video, and the slats at least are extended in the wreckage pictures.

5. There was no tail strike, so you would conclude that the performance figures were at least close to the actual mass and thrust required.

6. Given the above, and the straight flight path without rudder deflection which ends in a crater instead of Gatwick, you pretty much have all the evidence you need to conclude that there wasn’t sufficient thrust and that what little thrust there may have been was symmetrical.

7. While there are many things common to both engines, the most frightening are a system failure and inappropriate crew action. Oh, and some previously unheralded MX action.

Three firm pieces of evidence RAT deployed.

Auditory

Visual

Survivor statement

And, oh by the way, the A/C reported "Power Loss", implying loss of thrust on both sides. Which, ALSO, would drop the RAT.


High certainty at this point that RAT deployed. So you're back to wondering about the loss of thrust-- the big hole in the cheese.

I guess it all depends on what you mean!

If the fuel supplies were cut off, causing the engines to stop, is that engine failure ? I'd say not, nothing wrong with the engines until they impacted the buildings etc.

No evidence of RAT deployment - but you're specifically restricting "the evidence" to a blurry amateur video. That alone is not great evidence, but why does that video exist at all? When they lift the relevant section of fuselage, RAT deployment or not is going to be fairly apparent. And Circumstantial evidence is still evidence, no?

No evidence of electrical failure? Do you know that from the downloaded Flight Data?

I think there is uncertainty about contents of mayday call. Most media mention the word mayday with no reference to thrust etc. I wonder if conjecture has become fact.

A thrust reduction is not an engine failure. Engine shutdown due to an action of crew (or inaction) is not a failure.

There is no evidence of an electrical failure. What evidence? A surviving passenger thought he saw flickering lights? Give me a break.

The word evidence in English has a very specific meaning.

Look for the simplest explanation here and then ask why the worldwide B787 fleet is still flying with no urgent inspection requirements from Boeing or GE. Think about that "evidence".

If the photo of the flaps deployed at the accident site is actually F1 not F5 or if the flaps were pushed out during impact, then this is certainly plausible. I will look for the photo but it's in the thread somewhere. Others are stating they see a gap between the wing and the flap as an argument for the flaps deployed at F5. This was after the decent started..

However, I think their reaction would likely be to apply more power. I know mine would be. But anything is possible!

To me, the last sentence of (7) in Australopithicus' post nails it and here's why: We already know that this aircraft was cannibalized for spares as was apparently customary at AI and then brought back into service. The problem with this MX culture is that you lay yourself open to the "law of unintended consequences", such as replacing something with a part or pcb/software version that looks right and fits/works but may not perform as designed either physically (think Air Transat - Azores) or software wise (think the "roll back" bug). It isnt necessarily a problem if there is decent paperwork accompanying and authorising this "borrowing" but you can be sure that the investigation will want to see traceability paperwork.

No evidence of engine failure - Not true. No engine noise on video where you would expect TO or TOGA power to be in use. Mayday call stating No Power

No evidence of RAT deployment from a poor image . - You can argue Not from the Image but...: 2 independent audio analysis of the video audio shows the sound comes from a deployed RAT plus JB's video. Plus the guys who live in SEA having heard 100's of RATs deployed during test flight have stated that the sound is a RAT.

No evidence of electrical failure . - Not true. Reported cabin emergency lights going off, FR24 feed stopped just as in the 737 South Korea incident in December. APU intake door partially open at crash scene, suggesting an APU autostart.

Now you can call into question the above evidence but to state there is none, is simply not true.

Yes indeed. I strongly leant toward the incorrectly set AAI and VNAV capture and level off as the a/c reportedly reached max alt of 625ft or about 450ft AGL. Even with startle factor, recovery should have been quite possible. The video I have seen (not the video of the video) clearly shows the RAT deployed and you can hear the whine of the turbine and virtually no engine noise . This complicates it for me as there is no logical reason to deploy the RAT in the VNAV/level off scenario.