Made Jet-A1 for 14 years.
There were 66 samples of fuel drawn from this aircraft after the accident and the AAIB have reported that no contaminants were found other than traces of water. Chinese N03 Jet Fuel complies with the Spec for Jet-A1. In order for JetA1 to meet spec it has to pass 38 tests. If organic fats were present they would have been detected in at least three or four of the tests.
Some of the tests, e.g. density, are set with pass rates between upper and lower limits. If the results fall between the values then the spec for that test is met. Other results have to meet maximum or minimum values e.g. Flast point or Freeze point, if these minimum values are met or exceeded then the test is a pass.
When fuels exceed the values set then the quality of the fuel is not impaired.( The fuel producer just wastes money in the fuel production as they get the same price for it whether is meets or exceeds the spec. In my experience we played safe with Jet A-1 and never tried to be clever achieving a perfect blend, it was almost always better than spec.) In order to meet all the spec requirements some of the results will exceed the spec and this will vary from batch to batch. The Certificate of Quality is only issued if all tests have met or exceeded the minimum requirements.
Jet 1 is stored in tanks, pumped and transfered in it own dedicated pipework and was not in my days physically connected to any other pipework. Even drain valves had lead seals on them to demonstrate to an Inspector that the Jet A-1 containment system had not been disturbed. The seals were numbered with the refinery inspector's number on one side and a Government seal on the other. The small number of people who could fit these seals were registered and issued with their own seal compression tongs
The problem here is the management of water in an aircraft/ engine combination which was susceptable to any ice formation at low temperatures. There did not seem to be any fuel temperature control, the pilot got what the airframe produced in the climate in which he flew.The unlagged/non heat-traced pipe run from the fuel header out to the exposed FOHE and back to the engine being a cold section of the fuel system under discussion. The first time I saw the FOHE inlet tube
sheet I mistook it for a filter screen. I await the modifications to this system with interest. Like many of you I do feel it seems a long time coming. The final report? I am happy to wait for this.