Embraer Executive Jets recently conducted flight tests on two of its aircraft using 100 percent sustainable aviation fuel (SAF). The Brazilian airframer flew its demonstrator Phenom 300E and its prototype Praetor 600 at its U.S. headquarters in Melbourne, Florida, at the end of September after a year of preparations.
As a safety measure, both of the twinjets—which have separate fuel tanks supplying each engine—flew with one engine running on conventional jet-A while the other used unblended SAF.
“That’s one of the reasons that we did it on the 300 and 600 and not on the 100,” explained Alvadi Serpa Jr., the manufacturer’s director of product strategy and competitive intelligence. “On the 100, we don’t have the ability to segregate the left from the right side, so the day we go for the 100, it's going to be all in."
The logistics for the test involved many industry partners, according to Serpa Jr. The fuel was produced by World Energy in Paramount, California, and delivered by World Fuel Services. Embraer was required to purchase an entire refueler load of approximately 8,000 gallons.
This necessitated special permission from the Melbourne Airport Authority to bring it on the field because the 100 percent SAF—which is not yet approved by ASTM—is technically classified as a chemical product, not a fuel. “We got the fuel in the June, July timeframe in Melbourne," Serpa Jr. told AIN, adding that it was required to rent a pair of fuel tankers for the test—“one to work as a reservoir to hold the fuel before using it in the airplane and then another one for defueling so we wouldn’t mix the products.”
One of the noted drawbacks of 100 percent SAF, and the primary reason it requires blending with conventional jet fuel, is its lack of aromatic compounds. These are needed to help seals in the fueling system swell and eliminate leakage. Serpa- Jr. noted that the trucks—which had previously held jet-A but were cleaned thoroughly before receiving the SAF—began to leak, requiring the company to replace all the O-rings in the valves prior to the test program.
For the tests, Embraer also partnered with the engine makers for both aircraft (Pratt & Whitney Canada in the case of the Phenom 300E, and Honeywell for the Praetor 600) and the respective fuel systems providers (Safran and Parker). “They engaged and accepted the challenge and became real partners in the venture, which made the process much easier,” said Serpa-Junior.
The first phase of the campaign was ground testing, after which the fuel systems were flushed with jet-A and the O-rings were replaced. After no objections were raised, phase two of flight testing was accomplished, with the seals and valves again replaced.
“All removed parts were sent to the engineers and labs for examination,” stated Serpa Jr. “That’s ongoing because it has been only two or three weeks now, and we hope to have the results in the near term.”
In the meantime, he believes the test was a success. “We are confident that the fuel will work, because of the feedback we got from the pilots,” he said, adding that they were very satisfied with the performance of the airplane. “They did not see any change in performance, they didn’t see any degradation whatsoever, so it was positive.”
Serpa Jr. concluded with a prediction: "I think there will be a day when we’re going to have [100 percent SAF] approved with an ASTM stamp, and then it's going to be just another fuel."