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

amsm01
2025-06-15T08:54:00
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Post: 11902253
Originally Posted by bakutteh
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 switches to OFF 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\x92 imagination.😖🥴😬
(Sorry, Airbus here and not familiar with Boeing) Flap 5 to 1 reduction on the Boeing triggers autothrust reduction, is that correct? If so, are there any other conditions that need to be met for this to happen like being in some kind of takeoff mode? Just thinking whether this would have potential otherwise in other regimes to cause issues, discontinued approach perhaps.

Am slightly puzzled as to why if flap reduction triggering climb thrust is part of the standard logic (and presumably clean-up technique) then partial dual thrust loss wouldn\x92t be immediately recognised as the classic symptom of gear / flap retraction handling error? I presume Boeing pilots / air India are just as aware of this it as everyone else, strikes me as odd that one would immediately go into full dual EF mode. My instinctive reaction without knowing the Boeing would be to firewall both TLs, would this have worked in the early flap retraction logic scenario? Many thanks all
Someone Somewhere
2025-06-15T10:43:00
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Post: 11902342
Originally Posted by MaybeItIs
Originally Posted by JunkAccount
This is probably a very stupid question, but what would happen if a BPCU fault (or other cause) led to VFSGs on opposite sides of the aircraft being connected to the same 230 VAC bus?

My understanding is that the left engine VFSGs are not synchronized in frequency or phase with the right engine VFSGs. Cross-connecting them, electrically, could be quite violent from both an electrical and mechanical perspective.

Is it realistically possible that the torque shock from cross-connected VFSGs could damage their associated accessory drive trains to the extent that the associated FADEC alternators would no longer make power? In this situation, there would be a loss of aircraft electrical power due to the BPCU fault, no FADEC alternator power due to damage to the accessory drive train, and, therefore, no engine thrust.

I presume each VFSG has a frangible link to protect the accessory drive train in the event the VFSG seizes up, which ought to make this loss-of-engine-thrust scenario impossible, but presumption is not knowledge, and this is a possible failure chain that doesn't involve stacking up multiple 10e-9 events.
From my POV, this is not a silly question at all.

In fact, I have inadvertently "done" such a thing - all I did was switch the generator room light from one genset to the other. But whoever installed that cheap and nasty two way light changeover switch didn't realise that it sometimes did a make-before-break transfer. There was a BANG and everything instantly went dark. Every single circuit breaker on the switchboard tripped. To this day, I still don't understand why all the Load Circuit Breakers tripped as well as the generator output breakers, and no one has really supplied a clear answer. Of course, any inductive loads connected at the time would cause that, but simple incandescent light circuits? Would a couple of hundred meters of underground power cable have enough inductance to cause a breaker trip?

Anyway, Yes, the results were very dramatic, and these were only a pair of 10-15kVA Single Phase 230V gensets. If this happened on that plane with 225KVA(?) generators at a couple of hundred feet in the air, I'd imagine they had no chance of recovery. Could it happen? If something had been wired up incorrectly in the transfer circuits, I'd say Yes. When a fault-related transfer occurred.

Still doesn't explain what could have stopped the engines, but sheared shafts would have done it, as you say. That would be pretty strong evidence.

Now, if it's true that this plane had been scavenged for parts at some stage, all the couldn't happens probably evaporate. I'd guess...
It could do it, assuming fuses/contactors didn't vapourise first.

I expect the VFSG shafts would be designed to fuse/slip long before the main radial shaft feeding the gearbox, as noted.

But if it occurred, it would knock out not just your FADEC alternator but also the high pressure fuel pumps. Engine would stop dead near instantly.

It would partly be a question of how much interlocking is present. I guess bypassing/mis-adjusting mechanical interlocks is something poor maintenance could & would do.

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Sailvi767
2025-06-15T10:58:00
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Post: 11902355
Originally Posted by JunkAccount
This is probably a very stupid question, but what would happen if a BPCU fault (or other cause) led to VFSGs on opposite sides of the aircraft being connected to the same 230 VAC bus?

My understanding is that the left engine VFSGs are not synchronized in frequency or phase with the right engine VFSGs. Cross-connecting them, electrically, could be quite violent from both an electrical and mechanical perspective.

Is it realistically possible that the torque shock from cross-connected VFSGs could damage their associated accessory drive trains to the extent that the associated FADEC alternators would no longer make power? In this situation, there would be a loss of aircraft electrical power due to the BPCU fault, no FADEC alternator power due to damage to the accessory drive train, and, therefore, no engine thrust.

I presume each VFSG has a frangible link to protect the accessory drive train in the event the VFSG seizes up, which ought to make this loss-of-engine-thrust scenario impossible, but presumption is not knowledge, and this is a possible failure chain that doesn't involve stacking up multiple 10e-9 events.
What you suggest might be plausible. I had a tower shaft snap on a 767. The engine quits immediately. You lose fuel flow, oil pressure, generator and hydraulic pressure instantly. That could account for the gear not coming up. In a normal shutdown or flameout hydraulic pressure is maintained for a considerable period of time and windmilling will provide some pressure. I would have expected the gear to move further up in the retraction cycle. Tie this in with claimed electrical issues and the concept is at least interesting.

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old dawg
2025-06-15T11:03:00
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Post: 11902361
Retired engineer here. Following my post a while ago on the avionics electrical system I have read all the posts and also noticed mention of the hydraulics system.
Returning to my original source, which is Book 1 Introduction to B787 Avionic/Electrical, I read on p. 96 that the RAT will deploy if any of three conditions are met.

https://fliphtml5.com/quwam/qhdw/Boo...ics_Electrical

These conditions for deployment of the RAT specifically are:
Loss of both engines
Loss of power to the instrument buses
Loss of all three hydraulic systems

The latter one may be worth a close look because it would appear that problems took place when the wheels left the runway and I assume there was a change of states in various sensors. I surmise these sensors are different from the engine systems where both commands and power are needed to force a change of state in, say, fuel pumps. Is it the same for thrust control?
It says there are three hydraulic systems but is there a common reservoir? I'm not an expert in that field but google tells me that B787 has a bootstrap reservoir system which I understand to mean that a pressure of 5000 psi is maintained using a piston arrangement.

At this point think timeline, and changes of states.
There is an operational change when the wheels leave the ground. The associated sensors would send that data to the CCS. What was sent? Maybe the CCS read Hydraulic L + Hydraulic R + Hydraulic C = incorrect or fail, which would trigger deployment of the RAT. What would the electrical and control system do then? More importantly what exactly did all the systems do on this aircraft following such an event.
Was there a problem with the fluid in the hydraulics? Does hydraulic fluid ever 'go off' in very hot conditions. Or maybe there wasn't as much fluid in there than there should have been? How would hydraulics systems be compromised if indeed that was the case.
All speculation - but forensic system analysis is a bit like that.
Finally - what was the noise the survivor heard? Was it before or after the lights flickered? It may have been a bit of the airframe hitting something and snapping.
The survivors in the doctor's hostel heard a noise too which may be jet engines running. They would know the difference between that and other noises being close to an airport. Need a timeline for everything here.
Apologies for the long post. Just my thoughts.
RIP to all who didn't survive.

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Someone Somewhere
2025-06-15T11:16:00
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Post: 11902370
Originally Posted by old dawg
Retired engineer here. Following my post a while ago on the avionics electrical system I have read all the posts and also noticed mention of the hydraulics system.
Returning to my original source, which is Book 1 Introduction to B787 Avionic/Electrical, I read on p. 96 that the RAT will deploy if any of three condions are met.
Maybe the URL will work this time

https://fliphtml5.com/quwam/qhdw/Boo...ics_Electrical
These conditions for deployment of the RAT specifically are:
Loss of both engines
Loss of power to the instrument buses
Loss of all three hydraulic systems

The latter one may be worth a close look because it would appear that problems took place when the wheels left the runway and I assume there was a change of states in various sensors. I surmise these sensors are different from the engine systems where both commands and power are needed to force a change of state in, say, fuel pumps. Is it the same for thrust control?
It says there are three hydraulic systems but is there a common reservoir? I'm not an expert in that field but google tells me that B787 has a bootstrap reservoir system which I understand to mean that a pressure of 5000 psi is maintained using a piston arrangement.

At this point think timeline, and changes of states.
There is an operational change when the wheels leave the ground. The associated sensors would send that data to the CCS. What was sent? Maybe the CCS read Hydraulic L + Hydraulic R + Hydraulic C = incorrect or fail, which would trigger deployment of the RAT. What would the electrical and control system do then? More importantly what exactly did all the systems do on this aircraft following such an event.
Was there a problem with the fluid in the hydraulics? Does hydraulic fluid ever 'go off' in very hot conditions. Or maybe there wasn't as much fluid in there than there should have been? How would hydraulics systems be compromised if indeed that was the case.
All speculation - but forensic system analysis is a bit like that
Three hydraulic systems, each with their own reservoir, pumps, and accumulators. Engine bleed air (I think; some newer aircraft have a semi-permanent nitrogen charge) keeps a few tens of PSI of positive pressure in the reservoir to prevent pump cavitation; loss of this is not an emergency.

Left and right hydraulics have an engine driven pump that will keep turning as long as the engine is turning unless explicitly disabled.

Low reservoir levels are both a maintenance check and something that will raise an EICAS warning.

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medod
2025-06-15T11:34:00
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Post: 11902390
Originally Posted by lighttwin2
There are a few comments along the lines of "it is incredibly unlikely that..." this is selection bias in reverse. Something incredibly unlikely has happened, and it's contained in this sample set.

To summarise some known facts about the TCMA system:

1) TCMA will shut down an engine if:
  • It believes via multiple redundant sensors indicate the aircraft is on the ground
  • It detects engine power in excess of that set by the thrust levers - subject to a margin to account for engine performance variation - that is determined to be a runaway condition
2) In 2019 an ANA pilot was able to confuse the TCMA by rapidly moving the thrust levers into reverse, to forward and back into reverse again. This caused both engines to shutdown.

3) Since then the TCMA should have been updated/fixed (and indeed the software will have been updated by SB since the a/c was delivered, to detect a wider range of runaway conditions)

And speculation:

4) It may be possible - given the close timings - that a TCMA activation occurred as the a/c was leaving the ground, with kinetic energy and spool down time getting the a/c from the ground to its peak height

In the recent BA LGW incident the PF reduced thrust to idle at V1, then added thrust back, then committed to a RTO. I wonder if something similar could have occurred:
  • In error, PF reduces power to idle at a speed approaching V1
  • Engines begin reducing power, but n1 reduces more slowly than the TCMA system is expecting (perhaps because the TCMA margin is calculated when the a/c is stationary, but at 170kt a turbofan will spool down more slowly due to the ram air / windmill effect)
  • TCMA detects a runaway condition - while a/c is on the ground - and cuts off fuel via the relay circuit
  • PF decides to commit to takeoff and rotates, not knowing that TCMA has already activated
  • 10-15s after rotation, n1 has now dropped below minimums for electrical generation. Electrics fail, final transponder signal is sent, and RAT is deployed
Obviously this should not be possible, and there are other possibilities.
If TCMA cut fuel flow while still on the runway the aircraft would have been decelerating from the moment it lifted off, which is not what the ADS-B data indicates. The kinetic energy in the rotating parts of the engine wouldn't add much speed to the aircraft as the engines run down with no more energy being added via fuel.

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SteinarN
2025-06-15T11:54:00
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Post: 11902404
Originally Posted by Someone Somewhere
It could do it, assuming fuses/contactors didn't vapourise first.

I expect the VFSG shafts would be designed to fuse/slip long before the main radial shaft feeding the gearbox, as noted.

But if it occurred, it would knock out not just your FADEC alternator but also the high pressure fuel pumps. Engine would stop dead near instantly.

It would partly be a question of how much interlocking is present. I guess bypassing/mis-adjusting mechanical interlocks is something poor maintenance could & would do.
I have been really wondering what single point of failure could take out both engines simultaneously as seems to be the case here. One single main bus contactor closing in error seems to possibly be such a single point fault.
Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load.
So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error.
So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks?

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Kraftstoffvondesibel
2025-06-15T11:56:00
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Post: 11902405
Originally Posted by Stivo
Am I understanding that you are saying that the noise on the video identified as a RAT has a Doppler shift that matches plausible values for height and speed? That seems pretty conclusive to me that it is a RAT.
Correct. That was the original purpose of the calculation. In addition to the sound itself having the measurable harmonic signature from other rat videos.
What this plot also does however is tell you the speed if you know the height or height if you know the speed.

The iphone used to film this were pictured somewhere, knowing the iphone model, and thus the characteristics of the camera, and the dimensions of the airplane it wouldn't be impossible to calculate height from the video imo.

Just throwing it out there if anyone sees the use and feels the call.

My personal amateur speculation still centers around the cut off switches.
I have spilled coffee and sweet tea over complex electro/mechanical switches/panels before(large format audio consoles with 8000 buttons) and seen unexpected things happen.

I am sure the switches are spectacularly well built, but they are in close proximity and thus prone to the same external factors.
Does anyone know if these two cut-off switches in such close proximity has the exact same installation, or they differentiated in some way that makes a freak failure mode in one not neccesarily affect the other the same way?

Last edited by Saab Dastard; 15th Jun 2025 at 21:36 . Reason: Unwarranted speculation removed

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The Brigadier
2025-06-15T12:18:00
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Post: 11902422
There's some possible fuel contamination mechanisms which would only affect one aircraft

- The fuel truck’s water-absorbing “monitor” element breaks up, the first aircraft after the break gets the bead slug; later uplifts may be clear once the hose is flushed. The beads jam metering valves almost immediately.
- After pipe maintenance, the first few hundred litres can carry residual cleaning surfactant that strips protective films and causes filter-monitor “soap lock”.
- Biofilm growth happens inside one aircraft’s wing tanks when it sits in humid conditions or does short hops with warm fuel. On the next flight the biofilm shears off, blocks strainers,

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Ted633
2025-06-15T13:09:00
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Post: 11902451
Originally Posted by BrogulT
Is the ability of an engine to run using only suction feed ever actually checked or tested during operations or maintenance procedures?
Originally Posted by tdracer
A flight test (at least one - it's often duplicated) is performed as a basic part of aircraft/engine certification. One engine with all boost pumps off and on 'suction' feed - the other engine with normal aircraft boost pump operation (for what should be obvious reasons). Start, taxi, takeoff, and climb in that configuration until the test engine quits due to fuel starvation as a result of the engine fuel pump cavitation (done using "unweathered" fuel - once fuel has been at altitude for a period of time (hours or more - i.e. 'weathered'), most of the dissolved gases in the fuel have vented off, and suction feed works far better - often up to cruise altitudes).
I don't think this test is ever done during normal operations or maintenance (at least not on purpose) as it is very abusive to the engine driven fuel pump - the sort of cavitation that this causes rapidly erodes the pumping surfaces (it's SOP to replace the engine driven fuel pump after such a test).
This is a regular test during maintenance at my airline (British operator of 787s)
Carried out as part of a 12k check.

Fuel level in the wing tanks made to be between 3100 kg & 3400kg. Engines are started, APU shut down and boost pumps are selected off.
As long as the engines keep running, it\x92s test passed. (Just have to remember to fire the APU back up before shutting the engines down!)

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scifi
2025-06-15T13:23:00
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Post: 11902465
Seems to be funny that no-one has mentioned the Battery, which because of its age could have failed either Short-circuit or Open-circuit.
Maybe some Boeing Electro Techs, could explain what role the battery has in this circumstance.
The simultaneous failure of both engines points towards an electrical problem, unless the high temperature had adversely affected the fuel flow.
Someone Somewhere
2025-06-15T13:43:00
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Post: 11902481
Originally Posted by Skyscraper1995
Sorry I am not a pilot but I did spend three years filming a TV series at Boeing for pBS/Channel 4 about the design and construction of the 777, and my response is not a technical one anyway. Do airfields have high definition video coverage of all takeoffs and landings? If so, they should be public domain and there would not be hundreds of posts about grainy over-magnified smartphone footage. If they don't, a 6-cam setup on each runway (3 either side of runway, one back, one across and one forward) could record continuously to hard disk or cloud. If airfields don't have this, shouldn't it be made mandatory?
This discussion happened after Jeju. I note that one of the video sources here is actually leaked (camera-pointed-at-screen) airport CCTV. Do not mistake airport CCTV not being publicly available for it not existing.

Originally Posted by SteinarN
I have been really wondering what single point of failure could take out both engines simultaneously as seems to be the case here. One single main bus contactor closing in error seems to possibly be such a single point fault.
Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load.
So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error.
So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks?
We'd need to know the impedance/available fault current of the generators. 50x would be unusually high in an industrial setting.

VFDs are for frequency conversion to drive the motors (CAC/pumps/engine start). They won't be carrying the full generator load for galleys and anti-ice; that will be handled by cross-ties, which is a big black box on the 787.

Fast fuses can be faster acting than circuit breakers, but are one-shot. I'm not sure how fast-acting and effective the generator contactors/controllers are; conventional ACBs/MCCBs will blow open magnetically under sufficient fault current regardless of what the trip unit or close coil commands.

I wouldn't really expect electrical reconfiguration to happen on climbout, and I wouldn't expect it to be the first time this contactor gets used since maintenance - everything should get a good workout during sequential APU/engine starts.

Originally Posted by syseng68k
No system would be designed to parallel two frequency wild generators. The output from each would be rectified to dc and conditioned before application to the load, but could be paralleled at dc level if required for redundancy. These are quarter megawatt generators, where an out of phase connection could shear drive shafts, destroy the drive train, or worse.
Not designed to parallel, but you still need to switch each generator on/off buses and tie or separate buses.

In a very simple main-tie-main arrangement you can close any two of three breakers and still keep the sources separate. It gets much more complicated when you have ten different sources.

I suspect the 'large motor power centre' might parallel the rectified output of some generators.

Originally Posted by LTC8K6
I no longer believe in the no flaps / flaps raised early theory.

I think this was a major electrical failure most likely due to the engines quitting.

The 787 is far more heavily dependent on electrical power to run it's systems than previous Boeing planes.

It requires about 1.5 megawatts of power according to Wiki. 5X more than previous designs.

Things that were done by engine driven pumps/compressors and engine bleed air are all done electrically on the 787.

Flight controls that were moved hydraulically or pneumatically are moved by electric actuators. Etc.
The 787 flight controls remain almost entirely hydraulic except for stab trim and two spoiler pairs. The centre system is now electric- or RAT-only with no ADP backup. Left and Right systems are still driven by EDPs and will remain pressurised as long as there's fluid and the engines turn.

1.5MW is the figure for all six generators; only four can be used at once.

There's no indication they had any flight control issues.

Originally Posted by scifi
Seems to be funny that no-one has mentioned the Battery, which because of its age could have failed either Short-circuit or Open-circuit.
Maybe some Boeing Electro Techs, could explain what role the battery has in this circumstance.
The simultaneous failure of both engines points towards an electrical problem, unless the high temperature had adversely affected the fuel flow.
Battery is essentially unused in normal operations other than to start the APU and keep the clocks running. It's there for emergencies (like after the engines fail). And yes, been discussed.

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Blake777
2025-06-15T13:54:00
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Post: 11902489
Originally Posted by The Brigadier
There's some possible fuel contamination mechanisms which would only affect one aircraft

- The fuel truck\x92s water-absorbing \x93monitor\x94 element breaks up, the first aircraft after the break gets the bead slug; later uplifts may be clear once the hose is flushed. The beads jam metering valves almost immediately.
- After pipe maintenance, the first few hundred litres can carry residual cleaning surfactant that strips protective films and causes filter-monitor \x93soap lock\x94.
- Biofilm growth happens inside one aircraft\x92s wing tanks when it sits in humid conditions or does short hops with warm fuel. On the next flight the biofilm shears off, blocks strainers,
However\x85Cathay Pacific flight 780 from Surabaya to Hong Kong (2010) suffered just such a fuel contamination incident. This did not lead to immediate total engine shutdown. The function of the engines seriously degraded as the problems compounded during the flight, which reached the ground safely in Hong Kong both by dint of good fortune and serious skills of both Captain and Copilot. The aircraft did not drop out of the sky 20 seconds after leaving the ground.

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BrogulT
2025-06-15T14:21:00
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Post: 11902500
Originally Posted by tdracer
As I've posted several times, in this business you 'never say never' - but the chances that both engines fuel pumps were deteriorated to the point where they could not adequately provide suction feed fuel to keep the engines running is very, very remote.
OK I can accept that two bad pumps are unlikely but what I originally wanted to know was when the suction-feed system--as a whole--is ever tested. Your answer as I understand it is effectively "never". So then I'd ask what other parts of the system are there--check valves, tubes, fittings etc--that have to work properly in order to get fuel to the engines without electric pumps? The engines are lower than the tanks so it really is suction-augmented gravity feed, but are there any points where a leak could air-lock the system? Is the fuel feed to the pumps via a standpipe going through the bottom of the tank or via a loop that enters from the top of the tank? There have been cases before where mechanics have systemically misassembled things.




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MarineEngineer
2025-06-15T14:25:00
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Post: 11902503
Originally Posted by Kraftstoffvondesibel
Correct. That was the original purpose of the calculation. In addition to the sound itself having the measurable harmonic signature from other rat videos.
What this plot also does however is tell you the speed if you know the height or height if you know the speed.

The iphone used to film this were pictured somewhere, knowing the iphone model, and thus the characteristics of the camera, and the dimensions of the airplane it wouldn't be impossible to calculate height from the video imo.

Just throwing it out there if anyone sees the use and feels the call.

My personal amateur speculation still centers around the cut off switches.
Doesn't need to be a suicidal jump-seater, I have spilled coffee and sweet tea over complex electro/mechanical switches/panels before(large format audio consoles with 8000 buttons) and seen unexpected things happen.

I am sure the switches are spectacularly well built, but they are in close proximity and thus prone to the same external factors.
Does anyone know if these two cut-off switches in such close proximity has the exact same installation, or they differentiated in some way that makes a freak failure mode in one not neccesarily affect the other the same way?
Unless the distance from the phone to the aircraft is known, it is impossible to calculate the height.
adfad
2025-06-15T16:31:00
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Post: 11902614
Can anyone help with my theory - I'm an electronics and software engineer, but not a pilot.
My understanding of the infamous and previously fixed 787 issue was that the PCU software would trigger a shutdown of all AC generators (or rather their respective control units) after 248 days of continuous power due to an overflow of a software counter, and that this was fixed in software alone.

Hypothetically , if the PCU software triggered this state during takeoff, what would happen? I know the engines may continue running with engine-driven fuel pumps, but I also understand this doesn't work in all situations and perhaps during rotation with a high fuel demand and fuel tanks not horizontal this could be an issue? What does everyone here think it would look like if all AC generators were shut down, in terms of engine performance - would you expect there to be a reduction in thrust? With the gear stuck down would that be serious enough?

Engineless
2025-06-15T17:15:00
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Post: 11902643
Originally Posted by FullWings
I think it needs to be said again that pretty much anything can happen to the aircraft systems and the engines will carry on running - this is by design as they have independent FADEC and power supplies and at sea level fuel will get through without boost pumps. You could almost saw the wing off the fuselage and the engine would still produce thrust, TCMA notwithstanding.

We don\x92t know yet what actually triggered the RAT from the relatively short list but every item on it means there is a serious/critical failure(s). The flight path suggests that it was a double engine failure or shutdown (commanded or uncommanded) as anything else should have left the aeroplane in a poor state but able to climb away .
Firstly, I've read through this whole thread - thank you Admin & Mods for your considerable efforts to clean things up.

Secondly, as a (now ex) glider pilot who remains extremely interested in aviation in most of its forms, this discussion has been an education and thought-provoking, as it so frequently is whenever I lurk here (usually without logging in). Thank you all for sharing your knowledge, expertise and thoughts.

To my mind the above post (especially the sentence I highlighted) is amongst the best (and most succinct) summary of what the pilots likely faced, with little to no time to resolve the situation. I cannot imagine those last few seconds and my heart goes out to them, the passengers and the many loved ones left behind. If there is any good that can come of this, it is that the cause is found quickly, with no bias, and steps are taken to ensure the same holes in the cheese cannot happen again.

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adfad
2025-06-15T17:16:00
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Post: 11902645
Originally Posted by Screamliner
When we see the video, the airplane is still climbing / flying straight and level (not losing altitude), yet we hear what we think might be the RAT, I can't imagine that they had the kinetic energy to do this with no engines. if they had dual engine failure, they would have been a brick, Hot and High, no thrust, flaps 5, zero chance.
How long does it take for an engine to fail in terms of thrust output - what does thrust over time look like for various failure scenarios - e.g., no electrically powered fuel pumps, or contaminated fuel, or thrust set to idle or other issues?

The original mobile video (not the copy from someones phone screen) clearly sounds like a RAT but what does the engine itself sound like - is it idle or reduced in some way?

What is the minimum amount of thrust that would need to be lost to stop climbing and sink back down - it took 30 seconds from leaving the ground to impact from the CCTV and the first 15 was climbing.

I would look carefully at the fact that the PCU still has the technical ability to tell all AC generator control units to turn off via software, as proven in the documented and fixed 248-day software issue.

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fdr
2025-06-15T18:58:00
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Post: 11902721
Originally Posted by matiagr
The biggest news site in Greece claims to have the results of a kind of preliminary report from India AAIB which say that as the plane rotated, the pilot's seat malfunctioned (broken pin) and went suddenly far back forcing the captain to accidentally lower the thrust lever as he already had his hand on it and despite the co-pilots effort to help increase the thrust it was already to late to avoid the stall. I dont believe they would have posted something as serious as this without any credible source cause they are supposed to be a serious news outlet but you never know when stupidity takes over validity. Source is the protothema dot gr site
I will wager that this is absolute nonsense. The effect of pulling the power levers back to idle at rotate would be readily countered by pushing them back up again. The engines are still delivering thrust, it is a function of N1, not the lever. The lever commands where the thrust level will end up, the N1 gives the thrust output. The acceleration/thrust characteristics of these engines is not like a J52 or JT3D etc.

The proposition that is floated is that the pilot does not pull back on the control column, which he is holding onto with both hands as his seat slides backwards like a caricature of a bad Cessna 180 seat rail, that is plainly obvious from the pitch attitude of the aircraft, yet grabs lustily a double handful of thrust levers and holds onto those until meeting Ganesh in the next life?

Greek papers appear to be as rigorous and incisive in their cognition as the Daily Telegraph. Golly.

Seats: electric.
RAT deployment... presumably the hapless pilot doesn't grab the control column, or the thrust levers, just grabs both fuel control switches instead????

Do any reporters bother to read what they write?

9 users liked this post.

Stivo
2025-06-15T19:23:00
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Post: 11902745
Originally Posted by fdr
I will wager that this is absolute nonsense. The effect of pulling the power levers back to idle at rotate would be readily countered by pushing them back up again. The engines are still delivering thrust, it is a function of N1, not the lever. The lever commands where the thrust level will end up, the N1 gives the thrust output. The acceleration/thrust characteristics of these engines is not like a J52 or JT3D etc.

The proposition that is floated is that the pilot does not pull back on the control column, which he is holding onto with both hands as his seat slides backwards like a caricature of a bad Cessna 180 seat rail, that is plainly obvious from the pitch attitude of the aircraft, yet grabs lustily a double handful of thrust levers and holds onto those until meeting Ganesh in the next life?

Greek papers appear to be as rigorous and incisive in their cognition as the Daily Telegraph. Golly.

Seats: electric.
RAT deployment... presumably the hapless pilot doesn't grab the control column, or the thrust levers, just grabs both fuel control switches instead????

Do any reporters bother to read what they write?
I think it\x92s made up nonsense, but it is at least worth noting that pulling back to idle and pushing back with the wheels still on the ground is a potential TCMA trigger.

2 users liked this post.