hurricanemk1c 195 Posted September 4, 2008 Report Share Posted September 4, 2008 Hi all! The AAIB has released the intrim reportr of BA038, Bejing - Heathrow (14/1/08) One of the reccomendations : It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency, in conjunction with Boeing and Rolls-Royce, introduce interim measures for the Boeing 777, powered by Trent 800 engines, to reduce the risk of ice formed from water in aviation turbine fuel causing a restriction in the fuel feed system. More here : http://www.aaib.dft.gov.uk/cms_resource ... Report.pdf PDF Report! Kieran Link to post Share on other sites
mutley 4,498 Posted September 5, 2008 Report Share Posted September 5, 2008 Thanks Kieran, It's odd though because I thought these aircraft were built to cope with far more extremes in temperature than was encountered? Cheers Link to post Share on other sites
MartinW 0 Posted September 5, 2008 Report Share Posted September 5, 2008 They are, it was a bit of a freak occurrence. There must have been other factors involved. I bet they will be flying a bit lower, where it's warmer, in future when they fly over Siberia. The T7 has flown in these conditions many times before, with no incidents, there must have been something else at work in addition. Link to post Share on other sites
hurricanemk1c 195 Posted September 5, 2008 Author Report Share Posted September 5, 2008 Agreed Kieran Link to post Share on other sites
allardjd 1,853 Posted September 5, 2008 Report Share Posted September 5, 2008 The report is very well done, as is the investigation to date, though much is ongoing. I'm impressed with the report (I read every word), though one of the recommendations is classic bureaucratic CYA. The combination of low fuel temperature at takeoff, low temperatures enroute, low fuel flows throughout the entire flight after the initial climb (low climb rates in the two step climbs ensuring that) do make this flight kind of unique. If you look at each parameter singly, this flight is near the edge of the envelope on several, but is never the lone example. It appears, however, to be the only case where a single flight got into the edge of the parameter limits on two or three of the issues, and that combination may very well be the cause. Accidents and incidents are often the result of several small issues which would be innocuous in isolation, that stack up with unforeseen effects. My initial reaction, right after the accident, was that the quality of the fuel loaded in China would be the smoking gun and I'm happy for that to have been proven incorrect. One interesting point is that the blockage might possibly have existed throughout the approach. The system commanded four throttle-ups during the approach and the engine power responded correctly to the first three. They suggest that the engine pumps will draw fuel from the system downstream of a blockage for a while before a critical situation develops. That suggests a blockage far upstream in the system - the further upstream, the more fuel available in the downstream components to ride out transients. I would like to have seen this discussed further in the report. The failure of the two engines within seven seconds of one another strongly suggests a "common mode failure" in two reasonably independent systems. One factor affecting both, of course, is the environmental conditions in which they operated, further bolstering the idea of fuel system ice. Though it would be a long term fix and might possibly only be applicable to newer designs, it might be worth while to introduce a fuel heating system at the pump inlets using engine bleed air flowing in tubes. Generally ice forms most easily in fluid systems where pressure decreases suddenly, i.e. after restrictions - filters, strainers, control valves, etc. It might be possible to identify the points in the system most likely to accrete ice and introduce a moderate heating source, either electrical or via bleed air. I doubt bulk fuel heating would be needed. Interesting stuff, anyway, and I'm sure there will be more to come. John Link to post Share on other sites
allardjd 1,853 Posted February 9, 2009 Report Share Posted February 9, 2009 From AVWebFlash... Boeing, NTSB, AAIB Focus On Ice Accretion In Trent Engines Boeing Thursday notified all operators of 777 aircraft flying with Rolls-Royce Trent engines that the aircraft's fuel system is subject to compromise by ice. The notice is in agreement with both the NTSB and AAIB respectively that ice accretion in the fuel system was the cause when a Delta Airlines Boeing 777-200ER on Nov. 26 lost power while cruising over Montana at 39,000 feet and when a British Airways 777 famously crash-landed short of the runway at Heathrow on Jan. 17, 2008. Boeing's outreach included precautionary measures for flight crews piloting the aircraft through cold weather, that supersede those it issued in September (which, as evidenced by the Delta flight, did not resolve the problem). It is likely that a redesign will eventually grace the fuel system in the form of an airworthiness directive from the FAA. For now, triple-seven pilots flying with Trent engines are being asked to advance the throttles to maximum thrust before descent on flights that have maintained the same altitude for two hours. Boeing has outlined other precautionary procedures and it is likely that the FAA will make them mandatory as they did with those Boeing issued in September. Investigators of both the Delta and the Heathrow incident have a new target. Challenged by the fact that the key element in their theories would melt away before it could be observed, investigators currently believe the ice problem originates with the Trent's fuel-oil heat exchange system. If the heat generated by the exchanger is insufficient, moisture could freeze in the fuel system, blocking fuel and starving the engines. Link to post Share on other sites
hurricanemk1c 195 Posted February 9, 2009 Author Report Share Posted February 9, 2009 Hmm. So maybe an age problem with the Trent? Link to post Share on other sites
allardjd 1,853 Posted February 9, 2009 Report Share Posted February 9, 2009 Quote maybe an age problem with the Trent? Not sure I understand that??? John Link to post Share on other sites
mutley 4,498 Posted February 9, 2009 Report Share Posted February 9, 2009 Trent engine I think Link to post Share on other sites
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