GE Aviation has ground-tested its Passport long-range business-jet engine, the powerplant for the Bombardier Global 7500 and new 8000, on 100% sustainable aviation fuel (SAF) for the first time.

The 17,000-19.000-lb. thrust-class turbofan was tested over several days in March at GE Aviation’s Peebles, Ohio, test site running on neat HEFA (hydroprocessed esters and fatty acids) synthetic paraffinic kerosene, the most widely available SAF today.

“Preliminary test results of the Passport engine are favorable, with the engine performing similarly to when it runs on petroleum-based jet fuel,” GE said. The passport is already approved to use SAF, including HEFA, in blends up to 50% with conventional jet fuel.

Although only limited quantities are available today, engine-makers are testing their powerplants on the fuel to ensure they can run safely on 100% SAF once sufficient volumes become available so as to maximize the life-cycle carbon reductions. Rolls-Royce first ran its Pearl 700 long-range business-jet engine on 100% SAF in early 2021.

GE is now preparing to test its Czech-developed Catalyst turboprop on sustainable aviation fuel with the goal of running the engine that powers Textron’s Beechcraft Denali on 100% SAF by mid-2023. Pratt & Whitney Canada and ATR have previously ground- and flight-tested the PW120 turboprop on 100% SAF.

Engine OEMs are also testing the fuel in their large turbofans. CFM International’s Leap 1 flew on 100% SAF on both the Airbus A319neo and Boeing 737-8 in 2021. Airbus and Rolls have test-flown Trent engines on 100% SAF and Pratt & Whitney in March ground-tested a GTF geared turbofan on the fuel. Safran is testing helicopter turboshaft engines on 100% SAF.

Synthetic kerosenes such as HEFA comprise only straight-chain paraffinic hydrocarbons and lack the cyclical-chain aromatic hydrocarbons found in fossil jet fuel that are required to ensure fuel seals work properly. Engines and fuel systems need extensive testing, and potentially modification, to run on 100% SAF.

Multiple efforts are underway to develop and approve pathways to using 100% SAF. These range from allowing two or more different SAFs to be blended to produce a drop-in replacement for conventional jet fuel in existing aircraft to developing non-drop-in fuels that would only work in future aircraft.

GE said one of its fuel experts is chairing a task force within ASTM International that is developing the industry standards supporting adoption of 100% drop-in SAF, which does not require blending with conventional jet fuel. A second ASTM task force is working on the non-drop-in fuel specification

“As our testing shows, the Passport engine … can operate on approved sustainable aviation fuel today and in the future. Our customers can be confident that the Passport engine can help meet their sustainability goals to reduce CO2 emissions in flight,” said Melvyn Heard, Passport program president.