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

What\x92s a Dreamliner do on takeoff if flaps are selected up instead of gear?

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.

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.

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.

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?

Thanks for the clarification.

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.

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.

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.

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.

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).

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.