The salient "hypothesis" has to do with many hours of flight through very cold temps, in this case very cold temps. 038 flew at 38k for some time, and had poured most of its fuel through the engines by the time AT requested high thrust at short final. This high thrust value was attained and maintained for many seconds, so conclusion 1: the narrowest part of the fuel passage even if it was partially occluded by ice, was sufficient to provide fuel for the thrust selected.
Evidence was noted of cavitation concurrent with interruption of fuel flow, suggesting the fuel passage was plugged sufficient to cause rollback, hence conclusion 2: Ice had collected at some point upstream of HP pumps, Preventing flow, though 1.03 and 1.02 epr were noted. The engines continued to run.
Photographic evidence of surface accumulation of "Ice" on the interior of the fuel line was noted post test. Ice packed around the entry port of the HE was also demonstrated.
Hypothesis: Ice accumulation was allowed by a combination of factors suggesting that it was allowable quantities of water contamination of fuel building up over long hours of cruise flight that was responsible for the "plug at the face" of the FOHE which prevented fuel flow.
Having lain dormant as "sticky Ice" right up to throttle refusal, how did it arrive at the Inlet matrix? A number of possibilities come to mind. Warming temps at let down? Sudden increase of flow, lessening of hydraulic pressure? Vibration of pylon tree and FOHE on the shroud at first Increase? Since it was AT throttling up, my 'guess' is that extreme vibration associated with high thrust shook loose the Ice that choked the flow that prevented normal operation. Similar quantities/temps. caused the seeming "simultaneous" loss of power that was initially so startling, but that in hindsight seems reasonable enough.
These are questions that come to mind without assigning any mysterious characteristic to the fuel. Were these tested? Were they assumed? Look, either it is mysterious and more work (much more) needs to be done, or it is actually a straightforward case of a very rare combination of unlikely factors combining to cause starvation.
The major portion of the body of work done by the investigators is misleading, insufficient, inconclusive, and patronizing. The Chinese Fuel could have been crap, but it was shown that in spec fuel was found remaindered in 038. The Trent may need a more thorough re-engineering relative to fuel system (to include the airframe), including HP prior to FOHE, Bypass, Recirculating Spill, etc. How would anybody know? Because Boeing and FAA say so? They've not addressed this. Personally, I like the 757 for my trips to Hawaii.
The bolding is not meant to be aggressive, but I needed something stronger than italics, this is a very frustrating accident.
Then there's DELTA. What if cavitation had caused both FOHE cannisters to collapse over the Rockies?
bear
Last edited by bearfoil; 11th Feb 2010 at 18:57.