Clifford Development Announces FAA’s Issuance of an Unrestricted STC for the Citation 550 & S550

Final STC certificate covers modification of the 550 and S550 Cessna Citation Series aircraft using Williams International FJ44-3A engines.


KALAMAZOO, MI – Clifford Development announces that the FAA has issued the final supplemental type certificate (STC) ST02661CH which covers modification of the 550 and S550 Cessna Citation Series aircraft using Williams International FJ44-3A engines. This is the first STC issued to cover both Cessna Citation aircraft and it was issued with no operational limitations or restrictions. Certification flight tests document significant speed, range and direct operating cost improvements with this STC, which is available for installation at four Clifford service centers.

"Our entire team of engineers, technicians, flight crews, suppliers, and our shareholders are to be congratulated. This certification comes at a time when increased operating efficiencies and reduced environmental footprints are paramount. With its 35 percent reduction in average trip fuel consumption and noise reduction greater than Stage 4 standards, this STC transformation vaults the eight-passenger 550 and S550 into a completely new jet category," says Jim Clifford, Chief Executive Officer of Clifford Development.

In addition to the engine modification, Clifford Development certified 35 improvements as part of this STC, including: an Ametek digital engine display, heavy duty BFG brakes, and a dual FADEC system certified to July 2007 FAA standards. With this modification, the typical Citation 550's empty weight will be reduced by 250 pounds.

"The list of improvements will be important to every operator," says Clifford. "But the performance stands out. Of the dozens of pilots who have flown this airplane, each has raved about the performance. When they walk away from the airplane after their first flight, they smile from ear to ear."

Based on certification flight test data, the Company reports that the re-engined aircraft have significant performance improvements: less than 27-minute time-to-climb to FL430 versus the current one hour and 30 plus minute step-climb profile; a 50 plus percent increase in NBAA range with four passengers; and a 15 plus percent increase in max cruise. The Williams FJ44-3A engines are thermodynamically rated at 3000 pounds (with a takeoff flat-rated thrust of 2820 pounds versus the original engine’s 2500 pounds rating).

Clifford Development has appointed Great Lakes Aviation, Kalamazoo, MI; Threshold Aviation, Chino, CA; Central Flying Service, Little Rock, AR; and Stevens Aviation, Greenville, SC, as service centers.

Three customer airplanes have been delivered. The first delivery was a 550, which now has more than 250 hours of operation. The second delivery was an S550 airplane that now has more than 60 hours. The third aircraft, also an S550, will depart for South Africa the first of the year, after its crew completes Flight Safety training.

The new STC is being updated to allow Williams Engine information to be displayed on the Rockwell Collins 3-display Pro Line 21 IDS system.

Clifford summarized the certification programs for the 550 and S550 with the comment that, "In life, the typical price of more power is less efficiency. This is one of those rare and happy exceptions to the rule. Our customers will have significantly lower operating costs, significantly improved performance and greater safety margins."

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