Posts about: "Fuel Pumps" [Posts: 151 Pages: 8]

Page Links: First  1  2  3  4  5  6  7  8  Next  Last  Index Page

A340Yumyum
2025-06-12T13:55:00
permalink Post: 11899233
Originally Posted by procede
Dual engine failure due to fuel contamination?
Like the dual engine failures that occurred on every aircraft which took off before it, using the same fuel supply?

😩

2 users liked this post.
tdracer
2025-06-12T23:19:00
permalink Post: 11899828
Originally Posted by violator

Some catastrophic electrical/FADEC/engine interface failure (which I highly doubt is feasible in a modern 1309 aircraft)
About the only way that could happen would be some catastrophic software 'hole' in the GEnx-1B FADEC software. By design, the only thing the engine control really needs to adequately the engine is:
1) Fuel
2) Thrust lever position
Everything else is 'goodness'. The FADEC has its own dedicated (gearbox mounted) electrical generator (actually alternator), so even a 100% aircraft power loss wouldn't affect the FADECs ability to control the engine. It was right at takeoff - 'suction feed' would be more than sufficient if the aircraft fuel pumps failed, FMC and other aircraft inputs have only a secondary effect on the thrust setting, it's primarily determined the thrust lever position.
So there is no known way that a fault in the engine/aircraft interface could cause a large loss of thrust.

3 users liked this post.
Flysafe55
2025-06-12T23:54:00
permalink Post: 11899846
Boost Pumps?
Can someone smart on the 787 answer this: What protections and indications does the crew have if the boost pumps aren\x92t turned on? Can the engines start with them off? I know jet engines \x93should\x94 suction feed but rotation and dual flameout could be explained by pump issues.
tdracer
2025-06-13T01:30:00
permalink Post: 11899907
Originally Posted by benjyyy
The pilot is being quoted as saying to ATC:

"Mayday...no thrust, losing power, unable to lift"

I don't think a pilot with over 8000 hours experience would mistakenly diagnose that. Also corroborates with the RAT being deployed. Question is how do both engines lose thrust. Bird strike is the obvious one. Fuel contamination seems unlikely.

I see a post above showing how its possible an electrical failure can result in power loss. Passengers on the flight before this said there were issues in the cabin; lights, displays and air con was not working. Again, seems v unlikely to be related.
That post is simply wrong - if all aircraft electrical power is lost, the engines will keep running just fine (suction feed is demonstrated to be sufficient in the entire takeoff envelope, so even losing boost pumps wouldn't cut engine power).

8 users liked this post.
Alty7x7
2025-06-13T03:42:00
permalink Post: 11899963
Originally Posted by tdracer
About the only way that could happen would be some catastrophic software 'hole' in the GEnx-1B FADEC software. By design, the only thing the engine control really needs to adequately the engine is:
1) Fuel
2) Thrust lever position
Everything else is 'goodness'. The FADEC has its own dedicated (gearbox mounted) electrical generator (actually alternator), so even a 100% aircraft power loss wouldn't affect the FADECs ability to control the engine. It was right at takeoff - 'suction feed' would be more than sufficient if the aircraft fuel pumps failed, FMC and other aircraft inputs have only a secondary effect on the thrust setting, it's primarily determined the thrust lever position.
So there is no known way that a fault in the engine/aircraft interface could cause a large loss of thrust.
#3 would be the TAT and thus N1 Max on this very hot day. Nothing abrupt, but cumulative? Get hot enough and N2 limit can make hot day line steeper. But likely latched DT, which I recall was to deal with inversions. At 42C, likely used full-rated TKO. Also would be useful to know engine health, residual margins. Blast through EGT, stop at N2.
violator
2025-06-13T10:00:00
permalink Post: 11900272
Originally Posted by tdracer
About the only way that could happen would be some catastrophic software 'hole' in the GEnx-1B FADEC software. By design, the only thing the engine control really needs to adequately the engine is:
1) Fuel
2) Thrust lever position
Everything else is 'goodness'. The FADEC has its own dedicated (gearbox mounted) electrical generator (actually alternator), so even a 100% aircraft power loss wouldn't affect the FADECs ability to control the engine. It was right at takeoff - 'suction feed' would be more than sufficient if the aircraft fuel pumps failed, FMC and other aircraft inputs have only a secondary effect on the thrust setting, it's primarily determined the thrust lever position.
So there is no known way that a fault in the engine/aircraft interface could cause a large loss of thrust.
TCMA\x85?


1 user liked this post.
Sailvi767
2025-06-13T12:34:00
permalink Post: 11900458
Originally Posted by pampel
If the fuel was cut off, how long would it take until the engines spooled down? How long would it take, given wind-milling etc, for that to result in a loss of power? I'd love to see a timeline of the flight with the fuel being cut off that is remotely compatible with the events we saw, because I don't think it's possible.
I can tell you that when a jet engine has a catastrophic failure the loss of thrust is near instantaneous. Lost a tower shaft on a 767 which killed the fuel pump, hyd pump, oil pump ect… First cockpit indication and hard yaw almost coincidental.
Last edited by Sailvi767; 13th Jun 2025 at 13:16 .

1 user liked this post.
jxksz
2025-06-13T21:33:00
permalink Post: 11900929
Something I've been wondering about this accident is the phase of the flight where the apparent power loss happened. It seems like the engines were running normally through the takeoff, until the aircraft lifted off the ground. After that the loss of power seemed to happen very quickly.

Could there be a scenario where aircraft's fuel supply is interrupted by change in aircraft's attitude (for example faulty pumps, partially contaminated fuel)? Frankly I have no idea how 787's fuel pumps operate, or if fuel contamination could happen in a way that blocks the flow only when aircraft reaches certain nose-up attitude.
andihce
2025-06-13T21:51:00
permalink Post: 11900947
Originally Posted by ams6110
Air crashes are "unlikely" a priori. Therefore I think the root cause, when determined, will be something unlikely. Best case, we learn something practical that can be mitigated in the future.
To be clear, I am talking about the probability, given this crash has happened , that a particular item could be a cause.
The probability of something (or maybe several somethings) being a primary cause of this crash is near unity. The question, what possible causes are likely?

To take a specific item of speculation that might case dual engine rollback, fuel contamination was suggested. I don't remember all the points made in this context, but some were: no other aircraft presumably using the same fuel supply had issues; why would both engines apparently fail near simultaneously?; why would they fail just after rotation?; and so on. The consensus seemed to be, not impossible, but unlikely (presumably in the sense I just described).

Accidental (or even deliberate) fuel shutoff was also suggested. Again, the consensus seemed to be, possible, but unlikely for this type, since previous ergonomic causes of such accidental shutoff had long since been addressed.
BrogulT
2025-06-14T00:49:00
permalink Post: 11901040
Originally Posted by HumbleDeer
Default setup is left tank left engine, right tank right engine. Each engine also has two redundant pumps feeding it, meaning it can operate fully and normally on one operational engine fuel pump.

Furthermore, the engines cannot run from the center tank. There's no such thing. The center tank transfers to the outer tanks, when necessary or when running low or to resolve imbalances, either automatically or manually initated by the pilot for whatever reason. The engine fuel pumps only ever draw from their respective tank.
It is as thus impossible for the center tank being empty to cause engine shutdown unless the main tanks were also empty, in which case we would: be in a lot of trouble, shouldn't be taking off, and wouldn't have a massive orange fireball.
This is contrary to what is published here and elsewhere.

https://kb.skyhightex.com/knowledge-...7-fuel-system/

Can you state the source of your information? I have no way of independently verifying what I've provided. According to that, however, the two center tank pumps are higher pressure than the L/R tank pumps and will override them if both are activated. So the center tank fuel is used first, then the L/R tank pumps. If no pumps are operating, the engines can suction fuel from their respective L or R tanks provided there's enough atmospheric pressure. The end result is still that an empty center tank cannot cause an engine shutdown absent some other malfunction.

3 users liked this post.
Sailvi767
2025-06-14T00:55:00
permalink Post: 11901047
Originally Posted by HumbleDeer
Default setup is left tank left engine, right tank right engine. Each engine also has two redundant pumps feeding it, meaning it can operate fully and normally on one operational engine fuel pump.

Furthermore, the engines cannot run from the center tank. There's no such thing. The center tank transfers to the outer tanks, when necessary or when running low or to resolve imbalances, either automatically or manually initated by the pilot for whatever reason. The engine fuel pumps only ever draw from their respective tank.
It is as thus impossible for the center tank being empty to cause engine shutdown unless the main tanks were also empty, in which case we would: be in a lot of trouble, shouldn't be taking off, and wouldn't have a massive orange fireball.
Virtually everything in this post is wrong. The 787 fuel system is almost the same as the 767. The default setup is all fuel pumps on. Each wing tank sends fuel to the left or right respective manifold. The center (main) tank pumps send fuel to both manifolds and operate at a higher pressure than the wing tanks and will feed the manifolds for each side from its left or right pump before the wing tanks. If there is fuel in the center tank it is always burned first and directly supplies the manifolds to the engines. Once the center tank is empty the wing tanks then begin supplying fuel to their respective manifolds. If any pumps are inadvertently left off you will get a EICAS message and a light in the pump switch.

11 users liked this post.
Someone Somewhere
2025-06-14T03:05:00
permalink Post: 11901101
Miscellaneous comments:
Originally Posted by fdr
Many thanks. It still is a concern that the tilt has occurred but no doors have opened.
I have seen in manuals for other airliners that because the bogie tilt is by a hydraulic actuator, gravity deploying the gear means the gear doesn't tilt to landing position.

With the loss of centre-system pressure*, would you expect the bogies to tilt naturally? I.e. spring pressure holds the gear in the stowed tilt, a hydraulic cylinder pushes the gear to the landing tilt. No pressure means the gear returns to the 'stowed' tilt.

The tilt actuator is designed to be overridden when the bogie hits the ground, so perhaps it has some kind of intentional bypass and doesn't stay in place without continually applied hydraulic pressure.

If so, that would also point towards total loss of electrics and no attempt to raise the gear.

* 787 centre system is powered by two electric pumps, plus the RAT. The RAT hydraulic pump only powers flight controls, not the landing gear.


Electric loss:
Surely even total AC power loss shouldn't result in engine loss, even if the RAT doesn't come online. The FADECs have their own alternators, bare minimum flight control computers and actuators are available on battery (though probably result in some equivalent of Direct Law), and boost pumps are unnecessary at low altitude. Left/right EDPs will remain active if the engines are running at any serious speed; providing flight controls.

Poor crew reaction to ending up in direct law is possible but it's hard to see the electrical issues as a cause, not a symptom.

Originally Posted by atakacs
Interdentally I have read some reports mentioning a DVR (Digital VIDEO recorder). Is AI fitting such devices in their aircrafts ?
Anti-terrorism squad looks to be doing an excellent job (/s) and recovered a convenience-store-grade CCTV recorder, probably from somewhere on the campus it crashed into:
https://economictimes.indiatimes.com.../121823103.cms

wonkazoo
2025-06-14T07:44:00
permalink Post: 11901210
Sometimes complex sequences can have very simple causalities. A lot of complex speculation in this thread so far focused on highly technical things. Yet the basic fundamentals of powered flight have not changed (despite our attempts to do so) over the past 100 years.
  1. As a general rule it is a bad idea to run out of either altitude or airspeed or both.
  2. If you try to maintain altitude without sufficient thrust you will eventually run out of airspeed.
  3. If you have sufficient thrust you can maintain your altitude at a given airspeed, and if you have excess thrust you can maintain your airspeed and increase your altitude. If you have lots of excess thrust you can increase your altitude and increase your airspeed.
  4. If you try to increase your altitude by pitching the nose up, and without sufficient excess thrust, your speed will decay quickly, up to the point of stall, at which point you will lose any small amount of altitude you have gained and begin descending.
So…

Fact 1: The airplane stopped going up because it lacked excess thrust necessary to sustain the climb, and;

Fact 2: The airplane’s airspeed decreased constantly because they were trying to maintain either altitude or the climb, but lacked the thrust to do so, and;

Fact 3: If they had prematurely raised the flaps, the climb rate would have decreased/possibly turned negative, but the airplane would have continued to accelerate.

So where did the thrust go?

Fact 4: There is no adverse yaw seen in any of the videos, so wherever it went the loss of thrust occurred (nearly) simultaneously in both engines.

Fact 5: The only way to stop a jet engine from thrusting (sorry) is by either blowing it up or removing the fuel supply. If it blows up- like from birds trying to become a fuel source, there will be evidence. (See Jeju Air for a good example.)

Fact 6: There is (so far) no evidence of either engine blowing up. (I’m deliberately using highly technical terms here…)

Fact 7: There is unmistakably clear audible evidence of the RAT being deployed on the raw video from the right rear quarter of the airplane. Near supersonic propellor blades are an unmistakable sound- the RAT was definitively deployed no matter how much people want to argue to the contrary.

Fact 8: In the same video there is silence from the engines when they should be thundering at full (or nearly full) power. (Yes, I know that isn’t a thing- I am a simple man alas.)

Thus the only possible conclusions are (cringes as he waits for fdr to rip him a new ah):
  1. The engines stopped burning, at nearly the same moment in time.
  2. As a result, the airplane stopped climbing and also began to lose airspeed in an attempt to maintain altitude.
  3. The RAT being deployed so quickly means that the ‘puters believed both engines were dead donks. (They were.)
  4. If both engines ceased burning it meant the fuel supply was interrupted. We aren’t talking flight idle here- it was lights out for both.
  5. (I am quoting someone else here) There is enough suction for the fuel to feed even if the fuel pumps are inop.
  6. The engines stopped being provided with fuel. Because something physical was placed between the tanks and the burners. And they flamed out.
The $64,000 question here (remember when that was a lot of money??!!) is simply: What stopped both engines from getting fuel?

There are a very finite number of possibilities to that answer- and I do have my suspicions, but I lack the qualification to opine on that one.

I’ll leave the rest to the more experienced folk here.

Warm regards-

dce

27 users liked this post.
SR71
2025-06-14T08:38:00
permalink Post: 11901260
Originally Posted by wonkazoo
Sometimes complex sequences can have very simple causalities. A lot of complex speculation in this thread so far focused on highly technical things. Yet the basic fundamentals of powered flight have not changed (despite our attempts to do so) over the past 100 years.
  1. As a general rule it is a bad idea to run out of either altitude or airspeed or both.
  2. If you try to maintain altitude without sufficient thrust you will eventually run out of airspeed.
  3. If you have sufficient thrust you can maintain your altitude at a given airspeed, and if you have excess thrust you can maintain your airspeed and increase your altitude. If you have lots of excess thrust you can increase your altitude and increase your airspeed.
  4. If you try to increase your altitude by pitching the nose up, and without sufficient excess thrust, your speed will decay quickly, up to the point of stall, at which point you will lose any small amount of altitude you have gained and begin descending.
So\x85

Fact 1: The airplane stopped going up because it lacked excess thrust necessary to sustain the climb, and;

Fact 2: The airplane\x92s airspeed decreased constantly because they were trying to maintain either altitude or the climb, but lacked the thrust to do so, and;

Fact 3: If they had prematurely raised the flaps, the climb rate would have decreased/possibly turned negative, but the airplane would have continued to accelerate.

So where did the thrust go?

Fact 4: There is no adverse yaw seen in any of the videos, so wherever it went the loss of thrust occurred (nearly) simultaneously in both engines.

Fact 5: The only way to stop a jet engine from thrusting (sorry) is by either blowing it up or removing the fuel supply. If it blows up- like from birds trying to become a fuel source, there will be evidence. (See Jeju Air for a good example.)

Fact 6: There is (so far) no evidence of either engine blowing up. (I\x92m deliberately using highly technical terms here\x85)

Fact 7: There is unmistakably clear audible evidence of the RAT being deployed on the raw video from the right rear quarter of the airplane. Near supersonic propellor blades are an unmistakable sound- the RAT was definitively deployed no matter how much people want to argue to the contrary.

Fact 8: In the same video there is silence from the engines when they should be thundering at full (or nearly full) power. (Yes, I know that isn\x92t a thing- I am a simple man alas.)

Thus the only possible conclusions are (cringes as he waits for fdr to rip him a new ah):
  1. The engines stopped burning, at nearly the same moment in time.
  2. As a result, the airplane stopped climbing and also began to lose airspeed in an attempt to maintain altitude.
  3. The RAT being deployed so quickly means that the \x91puters believed both engines were dead donks. (They were.)
  4. If both engines ceased burning it meant the fuel supply was interrupted. We aren\x92t talking flight idle here- it was lights out for both.
  5. (I am quoting someone else here) There is enough suction for the fuel to feed even if the fuel pumps are inop.
  6. The engines stopped being provided with fuel. Because something physical was placed between the tanks and the burners. And they flamed out.
The $64,000 question here (remember when that was a lot of money??!!) is simply: What stopped both engines from getting fuel?

There are a very finite number of possibilities to that answer- and I do have my suspicions, but I lack the qualification to opine on that one.

I\x92ll leave the rest to the more experienced folk here.

Warm regards-

dce
Post 400\x92, on the assumption VNAV engages, the Flight Control Laws command pitch to maintain speed at VNAV engagement\x85up until Acceleration Altitude. So the aircraft will NOT accelerate like you assert in Fact 3. That is not a \x93fact\x94.

The FMA\x92s will be:

THR REF | LNAV | VNAV SPD

1 user liked this post.
RiSq
2025-06-14T11:48:00
permalink Post: 11901396
Having looked at the photos of the wings, one wing appears to have flaps and slats, the other does not.

this could be from post impact damage, but an interesting observation.

From what I can see so far, there is an electrical event that occurs.

but why and how that causes an aircraft to crash, is to be determined.

This is either going to be a very quick or very long investigation, no in-between.

My gut instinct is this is going to be a previously unexpected or unplanned failure that, whilst there was redundancy (expected) it took it all out.

although a totally unrelated incident, it reminds me of the LHR 777 with the fuel pump heaters being designed to stop ice getting into the lines. But on that exact day, conditions and variables, the very system designed to mitigate said problems, became the problem.

Luc Lion
2025-06-14T14:04:00
permalink Post: 11901512
A question for B787 pilots or mechanics.
Is it correct to assume that the EFSOV valves are actuated by the fuel flow and controlled by an electric signal coming directly from the relevant EEC. Meaning that the simultaneous closing of the 2 valves would require an improbable simultaneous failure of the 2 EEC, or that the 2 fuel switches are flipped from "run" to "cut-off" at almost the same time, feeding the same command to the 2 EEC.
And that the spar fuel valves are electrically actuated with the power coming from the hot battery bus and the signal coming from the aft electronic bay (possibly from the same control unit)?

(Note: not pretending to be a commercial pilot; just IR rated PPL).

1 user liked this post.
BrogulT
2025-06-14T14:35:00
permalink Post: 11901533
Originally Posted by MR8
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
If you read the MMEL for the 787, like most passenger jets there's a LOT of stuff that can be inop and you can still dispatch. APU, one of two center hydraulic pumps, etc. Not suprising to those if you in the industry but perhaps mildly disturbing to the rest of us. I'm wondering how much other stuff could be not working without being noticed. Specifically I'm wondering about the suction pumping of fuel on the engines. Since the normal mode is to run all of the fuel pumps, the suction pump mode is always overridden by boost pressure from the electrics. Might it be possible for wear, improper maintenence or some other issue to cause this standby suction feature to not actually work? Is it routinely tested and if so, how often? The idea here is that if the engines were not capable of sucking up fuel on their own, the airplane would be operated indefinitely without anyone knowing until one day there is a catastrophic electrical malfunction at an inopportune time. In this case, that might correspond with the cessation of the ADS-B data.

I'm asking this as a question, not claming to have "cracked the case". I'm not an aviation fuel system expert. Can anyone who is or has direct knowledge comment? The reason I thought of it is that I've seen very similar issues with diesel engine systems where the mechanical injection pump can typically suck fuel but is normally fed with pressure. An internal (or external) leak can cause it to not be able to suction fuel properly but as long as the other pumps keep it pressurized it can work forever.

2 users liked this post.
aeo
2025-06-14T15:35:00
permalink Post: 11901582
What concerns me a little bit is if indeed AC power is lost, would the suction feed inlets in the wing tanks provide enough fuel flow to maintain TO thrust?

I know the system is designed to achieve this in a situation where all of the AC powered boost pumps are lost. But what about in a real situation...

Could this cause a degradation of thrust? Even the slightest decrease..

And if the Captain(?) mentioned power loss in his Mayday. Was he referring to electrical power loss?
Sailvi767
2025-06-14T15:55:00
permalink Post: 11901596
Originally Posted by Compton3fox
Given the loads on the generators etc. at TO, I would say it won't take very long for the engine to spool down. Maybe around 5-7 seconds. Any differing opinions?
Thrust loss from a loss of fuel flow is near instantaneous.

2 users liked this post.
aeo
2025-06-14T16:02:00
permalink Post: 11901606
Originally Posted by Sailvi767
Thrust loss from a loss of fuel flow is near instantaneous.

Once the fuel LP and HP Shutoff valves are open, they stay there until commanded otherwise so an AC power failure will have no affect. They will remain in the last position at the time of the loss. They will then be on suction feed which, by design, should enable the engines to maintain their selected thrust level. They ‘should’ not suffer any loss of thrust.

Edit note: the engines have their own engine driven fuel pumps which can deliver anywhere up to and above 1,100 psi.

1 user liked this post.

Page Links: First  1  2  3  4  5  6  7  8  Next  Last  Index Page