Posts by user "compressor stall" [Posts: 12 Total up-votes: 0 Pages: 1]

compressor stall
June 12, 2025, 09:23:00 GMT
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Post: 11898927
Originally Posted by logansi
I just saw the crash video, and I'm convinced I can't see take off flaps set
What\x92s a Dreamliner do on takeoff if flaps are selected up instead of gear?

Subjects: None

compressor stall
June 13, 2025, 06:26:00 GMT
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Post: 11900060
Re fuel contamination. Shouldn’t the engines be feeding from separate tanks at that point? What are the odds of simultaneous Engine Failure? (Basing that on there is little yaw or wing drop to the live)

It’s years since I looked at it. I thought it was in the FARs explicitly but I can only find CFR 25.1309 states the safety analysis for equipment systems and installations that would be likely encompass this.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All)  Fuel (All)

compressor stall
June 14, 2025, 04:00:00 GMT
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Post: 11901123
Originally Posted by bcpr
Ex petroleum lab technician and tank farm sampler here. We would occasionally get fuel samples from crashed aircraft to test for contamination. One test was for water and sediment/microorganism sludge.

In this accident, fuel contamination continues to be dismissed as a cause, because no other aircraft have reported issues. But there has been no discussion regarding the airport's fuel storage, transfer, or filtration systems. Water and sediment naturally settles at the bottom of fuel storage tanks. If this aircraft received fuel drawn from the bottom of a storage tank, in the absence of a proper filtration system, it\x92s possible that it was contaminated. The next aircraft may have received fuel from a different storage tank with good fuel.

Fuel contamination is certainly a valid theory. The main thing working against it is that it would seem from the aircraft's flight path is that both engines failed at exactly the same time and lost thrust simultaneously. The chances of this are non zero, but remote. I say that as there appears to be no yaw, or other controlling of the aircraft - either by pilot or automation - that would suggest an asymmetric thrust scenario, even for a few seconds.

Yes, Jetstar had the biocide issue but did not immediately hit both engines within seconds of each other.

It's my understanding that both engines draw fuel from independent sources during that time (which may be fed from a common source (eg central tank). But again, the odds of both failing at the exact same instant is low, but not zero.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All)  Engine Shutdown  Fuel (All)

compressor stall
June 14, 2025, 05:12:00 GMT
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Post: 11901139
Originally Posted by BugBear
""The chances of this are non zero, but remote. I say that as there appears to be no yaw, or other controlling of the aircraft - either by pilot or automation - that would suggest an asymmetric thrust scenario, even for a few seconds.""

Look again at the initial video. The heading of the a/c is definitely right of centerline. Look at the background as the fuselage points right, and the aircraft "drifts" left. Something's up, either an input yaw to counter a cross, or asymmetric thrust. Not a lot, but noticeable. It diminished as the a/c disappears.....So, not an exact simultaneous loss of thrust, but almost certainly a single cause. Can't see the Rudder, nor the orientation of the gear, either or both could cause the slight yaw I see.
Yes, I can see that now too, although I wonder if it's just yawing into the wind normally - normally the METAR is in the first three posts after an accident

I don't have the perf data, but I'd be surprised if a heavyish (but probably not at MTOW) 787 would climb like that for the next 5 seconds or so on one engine with the gear out.


edit - found the METARs on page 2. Wind 10 mins prior 250/7 which would give 2-3 kts R wind. Not a lot admittedly, but it was consistently from the direction into which an aircraft would yaw to maintain RWY TRK.

Last edited by compressor stall; 14th June 2025 at 05:25 .

Subjects: None

compressor stall
June 17, 2025, 11:26:00 GMT
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Post: 11904221
If it's fuel supply issues...

I understand that the 787 is able to feed both engines from a common centre tank on takeoff. Most other aircraft feed each engine independently from each side until a safe(r) stage of flight.

\xa7 25.953 Fuel system independence. Each fuel system must meet the requirements of \xa7 25.903(b) by\x97
(a) Allowing the supply of fuel to each engine through a system independent of each part of the system supplying fuel to any other engine; or
(b) Any other acceptable method.

\xa7 25.903 Engines.....
(b) Engine isolation. The powerplants must be arranged and isolated from each other to allow operation, in at least one configuration, so that the failure or malfunction of any engine, or of any system that can affect the engine, will not\x97
(1) Prevent the continued safe operation of the remaining engines; or
(2) Require immediate action by any crewmember for continued safe operation.

I'd be interested in any history or understanding as to why Boeing went with the common tank approach on takeoff?

Last edited by compressor stall; 17th June 2025 at 11:42 .

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank

compressor stall
June 17, 2025, 11:47:00 GMT
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Post: 11904234
Originally Posted by EDML
Actually the engines are fed by all tanks during take off. (L engine: L wing tank + Center tank (if filled) / R engine: R wing tank + Center tank (if filled)).
Due to the fuel pressures of the feed pumps (that are all running) the center tank fuel is used first. In case the pump in the center tank fails or the center tank is empty the fuel from the wing will be used w/o any switch over taking place as the wing feed pumps are already running.
Thanks for the clarification.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank  Fuel (All)

compressor stall
June 22, 2025, 07:07:00 GMT
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Post: 11908309
Originally Posted by Icarus2001

Also that the DGCA wants THREE managers removed from their positions at Air India. Unconnected to this accident however.
Imagine Qantas being told by CASA to do a similar thing, or BA by the CAA, amazing stuff.
It's either 2 things....
1. That happens from time to time and its the way things are done in India and it's only newsworthy now by association (not causation), or
2. The DGCA need to be seen to be doing something, and that's some low hanging fruit in an otherwise vacuum of information.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): DGCA

compressor stall
July 13, 2025, 22:10:00 GMT
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Post: 11921721
Originally Posted by BrogulT
I agree that deliberately crashing a passenger airliner is something more than ordinary suicide. IMO it goes way beyond a despondent person that just doesn't consider the effect on their family or those that might be affected or injured when they crash their car or jump out of building. A pilot who does this is murdering a bunch of innocent people who trusted them to keep them safe. We don't have to explain it to know that it happens and whatever psychological state that causes it is real. And I think there is probably a big difference between someone that commits such an act without trying to create a plausible cover-up (Germanwings) vs someone who tries to make it look like an accident (FDX 705) or someone who may just be making some sort of point (MH370).

.
I had a discussion with an elderly relative who has a history of mental illness and was literally pulled back from the edge at times in her life. She is public in media about her journey now.
I opined - like you - of the apparent selfishness of the German wings event. Why do it and take so many others with you?
her reply was along the lines of, \x93When you\x92re in that space you have no awareness of your impact on others. They just don\x92t exist\x94.
It was an eye opening conversation.

Subjects: None

compressor stall
July 14, 2025, 01:01:00 GMT
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Post: 11921815
Originally Posted by Lookleft
For me the prelim report just reveals an unintended consequence of relying on muscle memory to carry out an action that has been performed multiple times without confirmation. It happens a lot but rarely with such a tragic consequence. I have turned the ignition switch to Normal during an engine start when asked to set the park brake during a pushback. There have been multiple occasions where an A320 park brake was set when a flap setting was commanded. On more than one occasion the flaps have been raised when "gear up" was commanded. This may not have been the first time the FCO switches have been selected but definitely the first time it wasn't picked up early enough to reverse the action.
.
There has been discussion about sim instructor muscle memory translating to the live cockpit. We of course do not know if that has any relevant to this yet, but I believe that is a hazard of training in an environment (eg FFS) that has psychological impacts on the candidate by design.

When running a sim, on repo', setup or end of session I never let any candidate push any buttons or do any actions that would not be considered not part of a normal flow that would normally be conducted at that point. On a reposition to a threshold, I might get the candidate to cycle the FDs or LSK in the MCDU once we are lined up and visuals back but that's about it. Everything else, start lever reengagement, flap resets etc are all off limits to the candidate and I brief as such.

Furthermore when I do the odd simulator in seat instruction exercise and do OEM prescribed "non normal" training (like a "gear up" -> Flap react incorrect selection) I will clench my non operating hand or squeeze my toes until they hurt and consciously tell myself I am about to do something incorrect... then do the (incorrect) action. That is my way of - hopefully - preventing muscle memory habits.

Last edited by compressor stall; 14th July 2025 at 01:35 .

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Muscle Memory  Preliminary Report

compressor stall
July 14, 2025, 06:18:00 GMT
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Post: 11921886
Originally Posted by beamer
What is it about these guys pushing out these videos wearing their uniforms...' I was a Captain'.....that seems so irritating !
Originally Posted by Mrshed
He is of course incorrect in stating a 10 second delay between CVR statement and FC switch to RUN.
Exactly. Here we have a captain who reminds us repeatedly of such, whilst denigrating reminding us that another aviation blogger who has a different theory is not a captain, but quietly praises another captain with impossibly shiny bars (Brasso perhaps?).

Nevertheless he glosses over / ignores the fact that the crew comments are not time stamped, and as such you cannot base much on the time delta until the switches were returned to their normal position. It could be 1 second or 9. I wonder why the decision was made to omit that time stamp in the Prelim Report.

Last edited by compressor stall; 14th July 2025 at 06:28 .

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR  Preliminary Report  RUN/CUTOFF

compressor stall
July 14, 2025, 06:54:00 GMT
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Post: 11921899
Look at 5.06 in the video, he simulates the CVR comments immediately after the cutoff and times the gap until they are switched back on. He may be right, but that timeline has no more validity than the CVR comments being 1 second before the switches are turned back on again, which could paint a very different picture (inadvertent or mechanical).

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR  Fuel (All)  Fuel Cutoff Switches

compressor stall
July 14, 2025, 07:08:00 GMT
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Post: 11921908
Originally Posted by sabenaboy
Ok, agreed. we can't know when these words were said, but I think it's reasonable to assume it was somewhere in the 10 sec gap.
The point he's trying to make is that this 10 sec delay is consistent with his assumption that it was all premeditated by the captain.
Yes, that is clearly what he is trying to make. The point I make is this: that point rests almost entirely on the CVR conversation happening very shortly after the switches are activated and there being a long pregnant pause before they are switched back. Had the cutoff been inadvertent (mistaken action by PM or mechanical) and it took them 8 seconds to work it out (which is quite reasonable under the circumstances), the switching of them back on 2 seconds later could equally be an entirely consistent timeline.

The report has not identified who said those words and when. I find this curious as it's pretty easy to count back the seconds from the end of the CVR recording or forward the application of full power.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR  Fuel (All)  Fuel Cutoff Switches