RAF ditches attemps to fly 100% synthetic fuel on TriStar

By Aimée Turner

The UK Ministry of Defence's efforts to fly non-crude oil derived 100% synthetic fuel were ditched last year after one of its partner design authorities expressed concerns over using the drop-in alternative.

All Royal Air Force aircraft, apart from a few small training types, can now use 100% synthetic fuel after the UK standards setting body and the MoD amended jet fuel specification DEFSTAN 91-91 last April. This approved aircraft to fly on South African fuels pioneer Sasol's 100% synthetic jet fuel from coal, nine years after its 50% blend secured approval.

No-one has flown the 100% synthetic jet fuel as yet, as commercial production would require expensive changes to Sasol's refinery, so the only experiences to date have been tests to prove it is fit for purpose. However, the MoD wanted late last year to be the first to conduct a flight trial using the fuel with one of the RAF's fleet of nine Lockheed TriStar tanker/transports.

© Royal Air Force

Most airframe, engine, ancillary equipment manufacturers, authorities and relevant oil companies have all participated in the approval process of the Sasol blend, and it had been thought that consent from Marshall Aerospace, the sister design authority for the RAF's TriStars, would be a formality.

But a senior source within the MoD attending the recent Alternative Energy conference at the Royal United Services Institute in London explains: "The project team which manages the TriStar said they would be happy to do it if there was no problem from the design authorities Rolls-Royce and Marshall Aerospace. Rolls gave consent, but Marshall cited its concerns over materials capability basically the fuel management system rather than the engine itself."

The source adds: "In this field, more effort must go into securing engagement from the whole community of stakeholders, not just the airframers and engine makers."

Marshall Aerospace says: "At very short notice we were asked to clear the use of Sasol for RAF TriStar use. The short timeframe required unfortunately made it impracticable to pull together all the required approvals." However, the company adds that "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."

The RAF expects its TriStar fleet to log up to 11,500 flight hours a year until the type's planned retirement in 2014-15. The aircraft, along with 14 Vickers VC10s, will be replaced by 14 modified Airbus A330-200s under the MoD's £13 billion ($18.5 billion) Future Strategic Tanker Aircraft private finance initiative deal with EADS UK-led AirTanker.