Cheeses
The latest advisory has deflected thinking on this thread into the mechanics of the Trent powerplant. But in reality its another cheese situation all over again, and the three relevant Cheeses are: temperature profile, fuel quality, and powerplant design. Only two of these, realistically/sensibly, can we change.
FE Hoppy and I, and one or two others way back at the beginning of 2008 said that the fuel will have had a role, and in the last few days Airfoil Mod and Spilko have reiterated that thought.
Blocking at least one hole in the cheese (Trent 800 FOHE redesign) takes care of the issue at least on the surface. But I would be more comfortable if someone could compare the performance with the current Trent powerplant flying the same temperature profile with fuels from from, say a European or a US refinery, compared to RP-3. (Jet Fuel #3, even when on spec and meeting Jet A-1 spec, can sometimes be, like Russian fuel, different compositionally to 'traditional' Jet A/A-1, if there can be said to be such a thing).
There was a statement in this thread some time ago referring to the fact that the behaviour of Jet fuel under extreme low temperature conditions was being shown to throw up some surprises in the testing following the incident, indicating that our knowledge may not be as good as we thought. Well, yes. I have said in an earlier thread why the recovered fuel may not be fully representative of the loaded fuel and in the final report I would like to see the GC/MS curves of the retention sample vs the recovered sample as well as the usual tests that define on-spec Jet fuel so we can have an educated guess at understanding the role that the fuel played - or not.
One thing I dont understand is a constant lack of reference to the retention sample. The AAIB report says that "It was estimated that the fuel uplifted in Beijing at the start of the accident flight might have contained up to 70 ppm of dissolved and entrained (suspended) water". Why estimate? Use the value that was in the retention sample which you will have analysed... or do you not actually have a valid retention sample?"
But, more generally, why should we bother? Surely if we block one cheese hole by fixing the Trent issue we can pack up and go home because the issue is fixed whether there is loads of water in the fuel or not?
The answer is we should bother because over the next five years we will see a proliferation in biofuel-based and Gas-to-liquids (GTL) based Jet A/A-1 blends some of which have known issues related to low temperature performance. The kinds of research that is now being conducted following the BA 038 incident is badly needed to ensure we can reliably predict performance and compatibility issues with, and better testing for, drop-in biojet blends which will prevent a similar incident. We need to confirm that the current testing regime - which has been in place with only a few modifications since before most of us were born - is sufficiently protective in current operational situations and with the diverse range of fuels that are about to enter the mainstream.
Can we afford not to block the second hole in the cheese by fully understanding the role that fuel played in the incident and the implications for different fuels that will be with us within a decade? That is why we must fully support the establishment of a joint FAA-EASA research and testing program that is a recommendation of Interim report 2.
Pinkman
Last edited by Pinkman; 15th March 2009 at 00:24.