A project by the UK's Ministry of Defence (MoD) to achieve the world's first test flight using 100% synthetic jet fuel, supplied by South African coal-to-liquids and petrochemicals major Sasol, had to be abandoned late last year.
This emerged at a recent conference on alternative energy held by the Royal United Services Institute in London, reports British aerospace journal Flight International.
The MoD hoped to be able to fly a Royal Air Force (RAF) Lockheed TriStar aircraft fuelled only by the Sasol jet fuel. On paper, nearly all RAF aircraft can employ Sasol's 100% synthetic jet fuel.
This follows from the amendment in April last year of military jet fuel specification Defstan 91-91 by the UK's standards authority and the MoD. Only a few small training aircraft are excluded.
However, to date, no aircraft has actually flown using the 100% synthetic fuel. Hence, the plan for a test flight.
However, before such a flight could take place, it was necessary to obtain the approval of all the relevant authorities, oil companies, and the airframe, engine, and ancillary equipment manufacturers.
There appears to have been a slip-up in this process, as a key company, Marshall Aerospace, declined to approve the test.
"At very short notice, we were asked to clear the use of Sasol for RAF TriStar use [sic]," the company told Flight. "The short timeframe required unfortunately made it impractical to pull together all the required approvals."
Although designed and built by Lockheed (now Lockheed Martin), all TriStars were designed and built as civil airliners.
The RAF bought nine TriStars second-hand, from airlines, and had them converted into air-to-air refuelling tankers (while retaining their transport capabilities). These conversions were designed and carried out by Marshall Aerospace, which consequently is the design authority for them.
It is believed that Marshall did not have the necessary time to approve the use of the Sasol fuel in the TriStar fuel management system.
Nevetheless, "if the decision is made to take this option forward on a permanent basis, Marshall would be very happy to conduct the activity, recognising the potential environmental benefits Sasol would bring to the fleet".