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BA38 777 G-YMMM interim AAIB report published

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  • BA38 777 G-YMMM interim AAIB report published

    The AAIB have today issued an interim report to the crash landing of the 777 at Heathrow earlier this year.

    The report indicates that Frozen water in the fuel likely caused restricted fuel flow to the engines on final approach.


  • #2
    Absolute miracle that this was not a total disaster...

    Comment


    • #3
      The most pertinent of the recorded parameters were the FMV commanded and actual positions. These showed that the EECs attempted to counter the shortfall in thrust demanded by the autothrottle by commanding the FMVs on both engines to open fully: the actual position showed that this was achieved.
      That pretty much shoots a hole in my leading suspect that it was electronic in nature.

      Comment


      • #4
        Well what else could it have been......?

        The FDR shows that at the time of the accident the total fuel on the aircraft was 10,500 kg, with 5,100 kg in the left main tank and 5,400 kg in the right main tank. Following the accident, approximately 6,500 to 7,100 kg of fuel had leaked out of fractured engine fuel pipes before the spar valves were manually closed.
        After reading 21 pages of ????, I have never read so many contradictions and blame but that's not blame but further tests might need to be done but really it has never happened in 6.5 million flying hours so this is one hell of a what? and the all the temperatures readings as well.... minus something when the plane landed..... O right and I remember that day, that hour, actually I was standing on the perimeter fence within 20 minutes of the flight coming down and it was not cold or maybe the sun was shining but further tests will need to be carried out.......

        I am still not buying the report but what do I know????
        Last edited by Cargo Runner; 2008-09-04, 21:08. Reason: Finally read all the report, in detail

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        • #5
          Originally posted by Cargo Runner View Post
          Well what else could it have been......?

          Read the report. It's interesting.

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          • #6
            Originally posted by Cargo Runner View Post
            Well what else could it have been......?
            I haven’t read the whole report yet. They seem to think ice is the main probable cause. I think it also possibly could have been a fuel cavitation issue, such as fuel foaming. In any case fuel quality may have been a possible factor.

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            • #7
              No Way

              I dont buy it. Both engines at almost the same exact time ? And further, both fuel flows almost the same ?

              It had to be electrical. Something slowed the pumps down even in wide-open position.
              ASMEL-IA 1978 A&P-IA 1965 First Aloft 1954 DC-4
              Dad: B-24 Ploesti Self: U205A1 private ops Nam

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              • #8
                The report is pretty clear:

                -All aircraft systems worked as they should.
                -Fuel quality met or exceeded all required standards

                What was unique: the combination of uncommonly cold air temperature at cruise, combined with below average fuel flow rate during cruise, and above average fuel flow rate during approach. None of the parameters by themselves were unusual, however the combination was.

                Testing has reduced the conceivable failure modes to two:
                A: Water ice gradually accumulating and restricting the fuel system somewhere between the LP and HP pumps
                B: Ice formed elsewhere being released into the fuel system and causing a blockage

                So far testing has shown that under some conditions ice may form and cause restriction in the fuel flow, but the accident scenario conditions could not be replicated.
                another ADC refugee

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                • #9
                  Originally posted by ATFS_Crash View Post
                  I haven’t read the whole report yet. They seem to think ice is the main probable cause. I think it also possibly could have been a fuel cavitation issue, such as fuel foaming. In any case fuel quality may have been a possible factor.
                  I've read it and reread it and there was nothing wrong with the fuel, the report say so -

                  I am in the group of people who believe the truth will never be told or publically known about this crash - as Uncle Jay says I don't buy this either.

                  Comment


                  • #10
                    Originally posted by Cargo Runner View Post
                    I've read it and reread it and there was nothing wrong with the fuel, the report say so -

                    I am in the group of people who believe the truth will never be told or publically known about this crash - as Uncle Jay says I don't buy this either.

                    It says tests revealed nothing wrong with the fuel. Not that there was nothing wrong with the fuel.

                    Big difference.

                    Comment


                    • #11
                      I've spent the morning reading the "Interim" report.

                      It all boils down to this:
                      They found no defects that could have caused the event.
                      The engine control systems operated normally.
                      The fuel feed system was capable of delivering sufficient fuel to the engines.
                      The fuel complied with the specifications.
                      So, there was nothing wrong with the aircraft. The pilots are blameless. The airline made no mistakes. The aircraft complies with all specifications.

                      The investigation is centering on ice blocking the fuel lines. They have conducted experiments detailing how such an event could happen. There are a few problems however.

                      1. The quantity of water required seems to be far in excess of the water found in the fuel.
                      2. The timing of the problem affecting both engines was unlikely to be caused by ice.
                      3. If all is normal when the problem occurred, who / what do the lawyers file suite against?

                      For Uncle Jay - The high pressure fuel pumps are driven by the engines. If the engines turn, the pumps turn. they can not be slowed down or speeded up without changing the engines speed.
                      Don
                      Standard practice for managers around the world:
                      Ready - Fire - Aim! DAMN! Missed again!

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                      • #12
                        The Boost Pumps Kept Working

                        It had to be electrical. Something slowed the pumps down even in wide-open position.
                        The digital flight recorder said that all boost pumps continued to produce full pressure.

                        Comment


                        • #13
                          Originally posted by Cargo Runner View Post
                          I've read it and reread it and there was nothing wrong with the fuel, the report say so
                          I still haven’t taken the time thoroughly read and absorb the report. I often make mistakes when I skim, however I don’t think that the report says there was nothing wrong with the fuel. On the contrary it said that water was found in the fuel filter and housing. I think they disqualified/exempted the fuel from the tanks because of the firefighting efforts probably contaminated the fuel tanks; thusly there probably was water and foaming agents in one or more of the fuel tanks, which would’ve likely compromise the tests from fuel in the tanks.

                          The majority of the fuel samples that they considered to be valid exceeded the fuel specifications. Yet they seem to say there was water in the fuel filter and housing, which suggests that there was an icing or layering problem. The report seems to suggest that fuel standards and procedures be set even higher to prevent the suspected cause water and icing.

                          I don’t know what the current standards for fuel is. However at one time they were testing a coloring agent that change colors when the water contamination became significant. I think in order to prevent this type of rare mishap it might be necessary to change procedures and spend a little more money; which may not be worth it. It might be necessary to do the current tests; but after the fuel quality test has passed it might be helpful to add a drying agent to reduce the odds of icing. I can’t remember what drying agent works for commercial jet fuel, ( perhaps alcohol). That helps dissolve and disperse the water to reduce the odds that the water will accumulate and freeze. I think much like with diesel it is a very tricky and difficult thing to do economically and within environmental standards and in a way that is logistically reasonable.

                          I still think it may be possible it is some sort of electrical/or electronic problem; however this report has swayed me away from that direction because there doesn’t seem to be any significant evidence supporting those possibilities. On the contrary the evidence at this point seems to suggest it wasn’t electrical mechanical or electronic in nature.

                          Comment


                          • #14
                            That about sums it up

                            Originally posted by Dmmoore View Post
                            I've spent the morning reading the "Interim" report.

                            It all boils down to this:
                            They found no defects that could have caused the event.
                            The engine control systems operated normally.
                            The fuel feed system was capable of delivering sufficient fuel to the engines.
                            The fuel complied with the specifications.
                            So, there was nothing wrong with the aircraft. The pilots are blameless. The airline made no mistakes. The aircraft complies with all specifications.

                            The investigation is centering on ice blocking the fuel lines. They have conducted experiments detailing how such an event could happen. There are a few problems however.

                            1. The quantity of water required seems to be far in excess of the water found in the fuel.
                            2. The timing of the problem affecting both engines was unlikely to be caused by ice.
                            3. If all is normal when the problem occurred, who / what do the lawyers file suite against?

                            For Uncle Jay - The high pressure fuel pumps are driven by the engines. If the engines turn, the pumps turn. they can not be slowed down or speeded up without changing the engines speed.
                            I think you have just about summed it up right Don - the finger cannot be pointed at anything in particular.

                            The crew cannot be blamed as they seem to have done nothing unusual
                            The plane (Boeing) cannot be found to be blamed because it might affect future sales
                            The engines (Rolls Royce) cannot be faulted to work properly as this could affect sales again

                            So this is really a freak set of conditions that cannot be explained because I think it would have too many connotations.

                            The thing that really grabs me is that everyday that flight does the same journey and this one particular sector had a problem...strange

                            Comment


                            • #15
                              Originally posted by Dmmoore View Post
                              I
                              2. The timing of the problem affecting both engines was unlikely to be caused by ice.
                              Unlikely yes, but not impossible with the second scenario.


                              The second scenario is that ice had accreted throughout the fuel feed system, and was then released during an increased fuel flow demand, such as the 12,000 pph achieved during the second acceleration on the final approach. In this case the ice might then travel and be ‘caught’ in the pipework, spar valve, LP pump inlet or on the face of the FOHE, thereby causing a restriction to the fuel flow.

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