Clifford Development Announces the First Flight of a Citation S550 Modified with Williams International FJ44-3A Engines

These flights are milestones in the development of a Supplemental Type Certificate (STC) to certify Cessna Citation S550 aircraft with new engines.

Kalamazoo, Mich., July 18, 2008 – Clifford Development announced the first flights of a Citation S550 equipped with Williams International FJ44-3A engines. These flights are significant milestones in the development of a Supplemental Type Certificate (STC) to certify Cessna Citation S550 aircraft with new engines – improving performance, cost of operation and safety.

The certification aircraft lifted off from Michigan’s Kalamazoo/Battle Creek International Airport for a 30-minute first flight. The flight profile was designed to evaluate aircraft handling and engine controllability. A second flight, which evaluated all aircraft systems interfaced with the engines and aircraft response to the new more powerful engines, was completed. Clifford Development and Great Lakes Aviation pilots and test engineers piloted and evaluated the aircraft.

“These flights are a continuation of the successes that we have had at each milestone with this airplane. The first ‘power on’ went very well. The first engine runs were flawless. And, today we had two flights, during which each engine-interfaced system, including pressurization, was evaluated. It’s significant that the airplane returned without a single squawk. The entire engineering, production and flight test team has done a remarkable job during the 150 days since we removed the original engines from this Citation S550. Now, on to Mojave,” said Bruce Wilcox, chief operating officer of Clifford Development.

Clifford added, “From the start, Citation S550 operators worldwide have been very interested in our program because of our forecasted 40 percent NBAA range increase. Currently, rising fuel costs have made our re-engining programs increasingly important to operators.”

Based on computations using the NASA-developed General Aviation Synthesis Program (GASP), the Company projects that the re-engined Citation S550 will have significant performance improvements: a 27 minute time-to-climb to FL430 versus the current one hour and 47 minute step-climb profile; a 40 percent increase in NBAA range with four passengers; a 34 percent improvement in single engine climb rate; and a 20 percent improvement in fuel efficiency.

In the coming weeks, the certification airplane will move to Mojave Airport to begin 100 hours of test flights to verify performance and to meet the FAA requirements. The Company anticipates the issuance of an STC in early fourth quarter of 2008.

The Citation S550 engine conversion is priced at $2,275,000 for 2008 installations. This price includes engines, engine core credit, digital engine instrumentation, winglets, Clifford Development aircraft improvement package, installation labor and training.

About Clifford Development – Clifford Development develops STCs for the installation of new engine technologies on the world’s existing fleet of high value corporate jets. The company will fund major re-engining certification programs to enhance the safety, value and performance of corporate jets. Detailed performance data on the re-engined Citation S550 and the re-engined Citation 550 are available at More information about the Williams International FJ44-3A and Williams International’s world-class product support is available at

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