Posts about: "RAT (All)" [Posts: 683 Pages: 35]

Presumably a dual engine shutdown under TMCA (i.e. similar to the ANA incident) would cause the RAT to deploy.

Obviously difficult to envisage what could cause an TMCA activation on both engines simultaneously given the safeguards in place (weight on wheels etc). However maybe the time delay from an erroneous TMCA activation on the runway/at rotation would lead to a loss of power 10 seconds later.

Having now heard the sound of the RAT from another video to compare the crash video to, I am convinced it\x92s deployed in the crash video, and I can\x92t see anything else other than a catastrophic power failure being the cause.

As to what has caused that, no idea, very sad.

Who are the posters....

There have been a number of posts going back to the idea that non pilots are posting and cluttering the topic. Sure, this is a pilot's forum, but for myself, I have certainly learned from non pilots, so I don't presume to discount the information from a person about aviation, just 'cause they are not a pilot.

That said, knowing that posted information is from a type qualified pilot is extra good. If a poster is a type qualified pilot, they are welcomed to say so in their post, as some have here. If you have other relevant experience, you're welcomed to present that too, even if you're not a pilot (I think of the poster who has heard many RAT deployments - 'cause he's around the Boeing factory flight route!)

We are trying to encourage compliant, value added conversation here, so it is not PPRuNe's objective to limit discussion without cause...

Question is why both engines lost power . Foreign object ingestion , contaminated fuel or both cutoff levels operated ? We do not know .

Any autothrust discussion is misleading since every pilot in that situation will firewall the levers whatever thrust reduction was selected for TO . the same is true for the RAT discussion- if enough hydraulic pressure was generated or not . The plane pitched up last second so there obviously was control until the end . Of course , without energy pulling alone will not bring you anywhere .

Why did both engines fail the same second as they would be cut off ???

I was thinking the same thing.

The "gear-up" places additional load on the hydraulic pumps and the result of that is step increase of load on the generators. Was this the trigger of the failures?

Let\x92s be careful about absolutes. Emirates 521 and Turkish 1951 are both examples of crews not firewalling the thrust levers despite low energy. The late pitch up could be due to the onset of a stall not an order from the crew.

TCMA is function which can reduce thrust on both engines simultaneously. It had done so in error in the past resulting in an AD. It uses air/ground logic so that it only operates on the ground, however note that at the point of thrust loss the gear is still down without any movement of the gear or doors. I would expect gear retraction to start before that height. Could we imagine an air/ground logic fault inhibiting gear retraction and allowing TCMA, which triggered (for whatever reason!) causing dual thrust loss? I would expect this to be in the realms of a combination of failures shown to be extremely impossible, but\x85

Firstly, I don\x92t think an inadvertent selection of flaps up caused this accident. I think it\x92s a red herring that seemed plausible initially but it is not consistent with the RAT being deployed, and the evidence for the RAT is strong.

To answer your broader question though, how could such an error happen? It happens because us simple humans learn how to do actions to the point where we don\x92t have to think about them anymore. This allows us to effectively automate routine tasks and save our brains for more novel tasks. The problem arises when we trigger the wrong automatic action in response to a cue. You ask for gear up, I know I need to select the gear up, I know where the gear handle is and what it looks and feels like, yet something goes wrong in the wiring of my body and instead, the flap-up automatic action is run. It\x92s run before I have consciously thought about it.

Sound far fetched? Well it has happened numerous times. I\x92ve seen someone do exactly that, select the flap instead of the gear, and there are incident reports publicly available. All modern passenger jets have a similar layout of the flap lever and the gear lever with the gear looking like a wheel and the flap looking like a wing, yet this error can still happen.

Have you ever gone to put something in the fridge that should\x92ve been put in the cupboard? I\x92d bet that most people have made that weird error at some point in their lives, and yet the fridge doesn\x92t look like the cupboard and they\x92re nowhere near each other.

The gear is required to be retracted within 12 seconds even on one engine. The fact that it wasn't means it was either not selected or there wasn't engine driven hydraulic pressure to do it.
Out of interest about when did the RAT include a hydraulic pump, not that it would be sufficient to retract the gear anyway.

The problem with the flap handle/gear handle mix-up theory is that it would appear in the original video that the gear up sequence has started based on the main gear leading axle pointing downwards, which is the first thing that happens (hydraulically) when the gear handle is moved.

Retired engineer here.
I have looked at the electrical systems on the B787 and this is my source. Book 1 Introduction to B787 Avionic/Electrical. Tried to post the URL but was unable to do so as I haven't made many posts.
I wonder if there may have been some kind of complex fault in the electrical system that day. The incoming flight passengers reported faults with the air conditioning and IFE. The electrical power system block diagram is on p. 84 mentioning engine generated power and the RAT which, if deployed, feeds a backup power bus. There is a power limit on the RAT system of 10kVA which probably isn't enough to retract the undercarriage (correct me if I am wrong). The main electrical system is 235V ac from the engines which is converted to DC using ATRU units (Auto Transformer Rectifier Unit) - see p. 95. These systems get very hot so there is a liquid cooling system called PECS. If there were malfunctions in ATRU units that may explain the air conditioning issues on the incoming leg. So, what exactly triggered the deployment of the RAT?. I'd be looking at the whole electrical network and not just the engine generation systems. The emergency lighting system (p. 146) is called WELS (Wireless Emergency Lighting System). The survivor mentioned that was flickering. Power/control systems cutting in and out. Those lights would be battery backed and would stay illuminated if the primary power/control permanently ceased. Just a few thoughts for consideration.

This was handled in this PPrune thread:
ANA 787 Engines shutdown during landing
and in AvHerald:
https://avherald.com/h?article=4c2fe53a&opt=0

Just to clarify one point: the ANA B787 was powered with RR Trent 1000 engines while the Air India had GEnx-1B67 engines.
So, the Air India thrust failure may still have its source in the TCMA system, however, if it's the case, the logical path must be somewhat different than for the thrust reversers of the ANA airplane.

Just remembered this video of a787 with its RAT deployed. You can certainly hear it. A lot of people said you could hear it in the AI video but I couldn\x92t.

A long while ago I posted on the Rumour thread about a ban on drinks on the flight deck sent to a BA, A350 mid Atlantic. It was prompted by 2 separate instances of uncommanded unrecoverable engine shut downs due to drink spills across the fuel cut off switches. It was widely mocked by the professional pilots on here until proven to be absolutely factually correct. If we are into speculation why not a drink left on the flight deck tips on aircraft pitch up and spills across both fuel cut-switches. Just sayin

Hutch

Jump to 1:48 in this video (if the link doesn't automatically put you there): You can't hear that RAT sound at the very beginning of the flypast?

Former Boeing Engineer, actually worked on this specific airplane prior to delivery. To me this all comes down to if the RAT was actually out. If not, lots of different factors people have already debated and likely some sort of pilot error that I'll let the pilots on this forum debate.

If the RAT did come out, then we are looking at simultaneous dual engine failure basically at V2 which is so improbable (without bird strikes or purposeful actions) that it is basically impossible. This is a 330 Min ETOPS aircraft. I saw no rudder deflection or yaw indicating 1 engine failed first and then they shut down the second one on accident.

Only two realistic options for me in that case are:
1. cutoff of the engines by the pilots. Either on purpose or accidental.
2. maintenance actions by the Air India ground team that caused issues with the engine system or power generation system.

2 is the only one I haven't seen mentioned here and I say this as a no longer Boeing employee. We STRUGGLED with AI during the EIS. They were notorious for just parking airplanes and then using them as spare parts and then screaming for help when they had to go back and get the planes ready to fly again.

Still think 1 is much more likely but will just throw out that 2 since there were complaints from previous flights about IFE and AC which to me speaks to issues with the power generation possibly being neglected.

I'll tell you what you can absolutely hear in that video as well: the engines. Now go to the crash video and compare.

No, it really isn't. For one thing if they retracted flaps, their speed would have increased, however distance and time tells us that their speed substantially decreased from takeoff to impact. Hardly possible with less flaps, descending, and take off thrust.

Compare the video with a normal plane flyover. The lack of engine noise, and propellor like sound of the RAT is so blindingly obvious I don't know how people are still going over the flaps thing.

Yeh I mean it's pretty conclusive, the sound is exactly the same. And there's clearly no engine noise in the crash video.

Confirmation bias is a very strong thing though. Once some people have put a theory out there on the internet they really really don't want to accept it might be wrong. Or form some that maybe the plane was at fault rather than being able to scapegoat a couple of dead guys.

Why on earth would their speed increase if they inadvertantly retracted the flaps?! If flaps are inadvertantly selected up without the required airspeed, the nose would have to be raised to compensate for the loss of lift from the flaps in order to maintain a rate of climb/avoid a sink, which would have the secondary effect of reducing airspeed... It's genuinely frightening the level of technical knowledge on this forum.

Not yet seen a response to my question about which engine parameters are recommended by the FDR and what is the sample rate.
Hopefully you might be able to answer this.
Many thanks.
I am a retired gas turbine engineer who worked on safety systems and assessments and assisted on a number of accident investigations (military fast jets) and would be interested to know this.