Posts about: "Fuel (All)" [Posts: 345 Pages: 18]

Like pulling a fire handle, shuts the firewall shutoff valve (wing root) and hydraulics on that side.At takeoff thrust not immediately but less than 10 seconds.

As more days pass without the FAA/EASA issuing an emergency Airworthiness Directive re. the 787 Dreamliner, it does appear more likely the cause of the crash was specific to the Air India aircraft (as per speculation on fuel contamination, bad maintenance, crew error etc. etc.)

Having gone through every possible way the aircraft (or those in it) can shut down both engines, thought it would be helpful to look at what investigators have looked at/for in a somewhat similar case. Perhaps it will move the discussion to more unplowed ground.

Going through AAIB Bulletin10/2008 from the British AAIB in the BA 38 case. Before finding the exact cause, they had investigated the following with findings in quotes:

1. General aircraft examination - "no pre‑existing defects with the electrical systems, hydraulics, autoflight systems, navigation systems or the flying controls."
2. Spar valves - "Extensive testing to induce an uncommanded movement, that remained unrecorded, could not identify any such failure modes."
3. High Intensity Radiated Field (HIRF) and Electro- Magnetic Interference(EMI) - "There is therefore no evidence to suggest that HIRF or EMI played any part in this accident."
4. Fuel System - "The examination and testing found no faults in the aircraft fuel system that could have restricted the fuel flow to the engines."
5. Engines - "No pre‑existing defects or evidence of abnormal operation were found with the exception of signs of abnormal cavitation erosion on the delivery side of both HP pumps. Some small debris was recovered from the left FOHE inlet chamber but this would not have restricted the fuel flow."
6. Fuel Loading/Fuel Testing - "No evidence of contamination was found." "The properties of the sampled fuel were also consistent with the parameters recorded in the quality assurance certificate for the bulk fuel loaded onto G‑YMMM at Beijing."
7. Water in Fuel - "It is estimated that the fuel loaded at Beijing would have contained up to 3 ltr (40 parts per million (ppm)) of dissolved water and a maximum of 2 ltr (30 ppm) of undissolved water (entrained or free). These quantities of water are considered normal for aviation turbine fuel."

Knowing the history of this flight, the previous flights and the climate that day, I left out all the discussion in the report of fuel waxing/ice. That seems as irrelevant as 'vapor lock'.

I too am beginning to think this will be, as an earlier poster termed it, a "unicorn" event.

Source: Bulletin_10-2008.pdf

Bringing part of my previous question back up: I know that fuel waxing was at some point one of the suspects in the BA 38 accident, but was ruled out via testing fuel samples. However I've been unable to find any records of airliner accidents or incidents that did involve fuel waxing, which I thought most likely existed if it was a possibility the investigation was considering? Does anyone know of any such incidents?

More accidents/incidents where fuel starvation was triggered by crystalline contaminants blocking fuel lines might also be useful - I'm trying to establish a range of how quickly and under what conditions such blockages could cause a loss of thrust in both engines.

One would hope, but, whilst there has been confirmation that the EAFRs have been recovered, nothing has been reported about their state or whether they have been downloaded or examined.

If the data is readable there may be a lot of politics and reputation on how that data may be interpreted. Behind the veneer of international cooperation vested interests will be being considered, advocated and agreed.

It, unfortunately, is naive to think that politics will not have a silent presence in agreeing a press release. Boeing and GE are flagship USA companies. Air India is the flagship carrier of India.

Investigations of all types first establish what happened, then how and why, before recommendations and actions. There is a possibility that they know the what, but the how and why incur liability.

Investigators will try to establish a single source or truth. For them, that\x92s an ideal outcome. But due to the nature of investigations, the aim gets derailed as established facts versus possible/potential scenarios based on missing links of the chain are pieced together. But for sure, commercial considerations and liability wont enter into a proper investigation. The task of the investigators is to determine the how and why.

Theres a saying, and it may even have been the title of a book\x85 Lift is a gift but Thrust is a must. In this case, certainly one or both were absent.

For 2 (maybe 3 if it was a training flight) professional people, the day started with waking up, getting ready, saying goodbye to loved ones, who they believed they would see again soon in 2-3 days. Sadly, that won\x92t happen, and it\x92s the job of the investigators to find out why and liability isn\x92t a hindrance to them.

They will look at every piece of evidence and recreate the events. But it will take time.

information worthy of note is:

A) The gear was still down.
B) It would appear (due to some work by amazing members) that the RAT was indeed deployed.

Other observances:

1. Bits flying off the aircraft. (From experience of operating in this area, they like to fly kites, and waste thermals and floats around, notably plastic bags) I have no idea if that la what we see or not.

2. Generally in India, they love using their horns. So whilst you can compare the frequencies of a potential RAT to a motorbike, appreciate there would be a million horns going off too.

3. Some posters have spoken of the \x93startle effect\x94 like they know what they are talking about. The most startling effect of a professional flight deck during an emergency is how calm it is. There aren\x92t hands flying around everywhere. In fact:

V1 > Rotate > Positive Rate > Gear Up > Confirm FD/AP Modes is adjusted to:
V1 > Rotate > Positive Rate > Gear Up > Silence the bell (Or your SOP Variation) FD/AP modes and the PF flies the aircraft.

the next step is to identify the problem, agree on it and then perform the actions. That won\x92t happen below 400\x92.

4. There\x92s no company in the world where Pilots are being fed and watered between V1 and 1000\x92 so spilling drinks on run switches isn\x92t a thing on this departure.

5. Temperature inversion. Yes it\x92s possible and it degrades performance. However, if it\x92s present, it\x92s usually announced on the ATIS. IF other aircraft have reported it.

6. Fuel contamination. Without knowing the systems, yes it\x92s potentially possible, but it would appear no other aircraft have reported being affected by it.

I think, this accident is especially interesting to Professional Aviators and Engineers because I think none of us would ever believe that it could happen. The aircraft is highly automated, the crew have been properly trained and the operation was a regular or possibly training flight.

A query I have is, do later Gen aircraft like the 777/787/747 A330/A350/A380 constantly send Airframe/Engine data home to ops/engineering/oem\x92s. Is it likely the data is out there?

Anyway, I just wanted to post this to reassure the travelling public that Pilots don\x92t try to shut down engines before they raise the gear.

Could someone post an authoritative list of the inputs to the EAFR\x92s? By \x93authoritative\x94, I mean the actual wiring diagram excerpt of the aircraft model and engine configuration (and hopefully mod state...), that labels each input.

I\x92m confidently assuming that it will, for example, include an input monitoring the state of the input controlling the fuel shut off valves in the wing roots. But does it monitor, separately, each and every one of the switches and systems that can change the input controlling the fuel shut off valves? I'm hoping and assuming \x91yes\x92, but hope and assumptions can be unhelpful and misguided.

As we know, there are some things the pilots can do that will result in fuel shut off, but other things will result in fuel shut off without pilot intervention.

Of course, it may be that the recorded data will indicate that there was no change in the state of the inputs controlling the fuel shut off valves during the short flight. Hopefully \x96 yes hopefully \x96 that will be confirmed one way or other, soon. Along with another dozen questions....

I was struck by a comment in this or the earlier thread that I cannot now find. It was to the effect \x96 I\x92m paraphrasing \x96 that fuel shut off results in an almost immediate cessation of thrust. (Please correct my paraphrasing if I\x92m off track.) I was also struck by how quiet the aircraft was in the original video, except for the RAT. (Or was it a motorcycle? Sorry couldn\x92t resist. Just joking\x85)

Someone earlier asked how the aircraft could have kept climbing if both engines stopped very late in the take-off roll or shortly after take-off. My answer: Momentum. A bullet fired into the air loses thrust immediately after \x91take off\x92 but continues climbing for a while. And my understanding of the expert opinion on the available, reliable information is that the aircraft didn\x92t climb very far.

Spot on, there's so much fuel being sucked at that power setting, it would be super quick and presumably at near enough to the exact same time.

I assume (rightly so) that you're focused on what could cause them to fail at what appears to be the exact same time given the absence of yaw and any correcting rudder input.

One the face of it, it could only be throttle or fuel supply, with fuel supply only being able to be cut off by valves so abruptly. Any kind of blockage or similar wouldn't give such a result, even if there was a low fuel condition, short of the pickups being exactly right next to each other, presumably that wouldn't give the outcome we've seen.

tdracer explained that earlier: T/O power to sub idle on fuel shutoff only takes 1s, at most 2s.

Slamming the throttles back is a lot slower as the FCU (on a traditional engine)/FADEC spins down the engine slowly - I suppose to make sure that the airflow through the engine remains stable.

Regarding the momentum: As the first few seconds of the climb were normal compared to previous T/Os of the same flight (speed & altitude, confirmed by comparison of the RAW ADS-B data) I don't believe the engine failure happened before or on lift-off.

Salvi, just spitballing here, a low alt capture is simple to rectify, but if you’re not expecting it ( perhaps a wrong MCP alt setting) coupled with a HUD , which focuses your attention on it, not the thrust levers, and add to the mix an inexperienced F/O. I can
also see in the final moments of desperation, reaching down and turning the Fuel Control Switches, OFF-THEN-ON, in the hope that an engine will come to life, if they believed that the engine was dead. This may be the reason the RAT extended? Just thinking out loud.

A case in point is the 2013 Boeing 787 battery fires. After two thermal runaways in 52 000 flight-hours, the root cause was still unknown; however, the FAA nevertheless issued Emergency AD 2013-02-51 grounding every 787 until a modification was available. IMHO a risk where the outcome is catastrophic, even very low probability, would trigger the FAA to issue an Emergency Airworthiness Directive as per their policy.

As I said in a previous post, every day that passes without a EAD suggest the cause was was specific to that aircraft (fuel contamination, maintenance failure, crew error - pick you own theory)

Yes and no. As the investigating teams are not issuing running updates (and neither should they) we don\x92t know what stage of the process they have got to - the DFDRs might still be in a lab somewhere with a team of experts working out how to get the data out without compromising it. Or they could have the data but be none the wiser as to the cause(s) of the accident - Jeju comes to mind.

Given that there are >1,100 787s in service, you would be losing a significant part of the World\x92s air transport infrastructure if you grounded them. Also, if you\x92re still nowhere near understanding what caused it, how would you \x93unground\x94 the fleet if you don\x92t get answers for some time? It\x92s obviously something rare/unique, given the 14 years of operation without such an accident, so statistics should be on your side if you did nothing until you had more surety as to where the problem(s) lay?

Additionally, the lithium-ion batteries in the 787 design required compliance with "Special Conditions" in order to gain type certification. The addition of the Special Conditions at least strongly suggests that FAA's certification process brain-trust had maintained some vigilance with regard to the batteries once the type started operating, i.e., given their newness.

At this time, the fault or flaw at the root of this accident and how that fault or flaw worked through aircraft components and systems has not been identified publicly. It might not even have been identified .... I'm not convinced that separating "what" from "how and why" as a semantics exercise is enough to conclude the Annex 13 officials know the root cause yet. Maybe they do, maybe not.

And if they do not, then the contrast with the situation where FAA was, it seemed, keeping a close eye on battery issues in particular, is relevant.

I am a software engineer, I find it alarming that the power control unit had the ability to command all AC generator control units to effectively shut down - regardless of that being the side-effect of a bug, or an ability of the system to call on in appropriate scenarios.

Integer overflow is a specific type of issue common to many systems, but like you said - it is something that should be found with robust QA and analysis. The ability to shut down all generators at once from a single source seems like a risky design decision to me and I agree with your point about different software on 2 or more redundant sub systems.

My theory is that this was an accepted risk because the engine-driven fuel pumps would be more than enough in most phases of flight to keep the engines running, and you would still have 2 engines for redundancy. The APU would also restore AC power in lets say 30 seconds and you would then have electric fuel pumps as well.

I think there are several factors that could explain how loss of all AC power during takeoff could lead to a crash:

• The crash happened within 30 seconds - possibly too short for the APU to start, and the RAT doesn't power the AC electric fuel pumps
• The engine driven fuel pumps even if sufficient in level flight may have struggled during rotation - has Boeing tested an actual takeoff with only EDP feeding the engine while the fuel tanks are rotating and in extreme environments, or, have they only tested this statically?
• The takeoff was hot and heavy - combined with the landing gear stuck down and reduced thrust from loss of electric fuel pumps could this be enough?

Actually, according to tdracer , each channel of the FADEC gets just one throttle resolver input, as the two resolvers are on separate wiring looms. So, the FADEC is using the dual channel feature to handle erroneous throttle position inputs. However, according to the patent at least, each channel can trigger TCMA and cut the fuel supply independently. So now we're down to only needing only one erroneous throttle signal per engine. Or one wrong interpretation of a signal, e.g. value clipping where you shouldn't (shortcircuit -> idle), some integer overflow etc.

So, from my understanding, if there is an issue with some of the throttle position sensors, the FADECs will detect a disagreement and keep the high thrust -> assume safe is "fly", whereas one of the TCMA channels might read or misinterpret throttle position close to idle. As the thrust doesn't decrease, at some point the upper bound of the falling TCMA thrust contour will be breached and the engine will be shut down.

@syseng68k
Consensus here is, that both engines where stopped by a closing fuel cut off valve, wich yields a fast loss of N2. The generators then shut down very quick as does the thrust in a few seconds. This is supported by the quick RAT extension which allowed the crew to control the flight. The APU did autostart too. A thrust changed with the thrust leaver to idle is much slower and would not result in the dramatic change in performance. Thrust set to idle will not engage the RAT since the electric generators would still work. So a thrust leaver changed to idle or any intervention by Autothrust (AT) would not yield to the RAT extension. Something or someone activated a fuel cut off. How and why that happened is the big question, the investigators have to answer.

A naive glider pilot question: if fuel cut off was (inconceivably) selected, would both fuel control levers have been flipped downwards from Run to Cutoff? And if they were then immediately flipped back to the Run position, how much time would have been needed to achieve enough thrust to maintain altitude?

The fuel cutoff switches can't be "flipped" in either direction; they have to be lifted over a detent and then moved, a very positive action.

The simplest answer: Lo Lvl Alt Cap; Thrust to Idle; Startle Factor; Inappropriate Memory Items : ( RAT deployed; insufficient time for Eng relight.

As an ex-tp, I would consider those cut-off switches a danger, and they should have guards either side of each.
Shirtsleeves/watches etc. can get caught, lift switch.
Very poor design. Would not pass `military-muster.`