Sikorsky’s X2 technology demonstrator, a high-speed semi-compound helicopter, flew for the last time on July 14 at the company’s West Palm Beach, Fla. test center, in front of a number of the manufacturer’s military and commercial customers. The sortie took place without the central hub fairing (also known as an “aero sail”), which will not be tested in flight. Sikorsky had previously indicated that the fairing could boost the X2’s speed by 15 to 20 knots. The company’s engineers are now turning their attention to the design of the S-97 Raider prototypes, which will also feature contra-rotating main rotors and a pusher propeller.

The July flight was the 23rd test flight of the X2, which logged a total of approximately 22 hours in the air. On Sept. 15, 2010, it achieved a maximum cruise speed of 253 knots in level flight, setting an unofficial speed record for a helicopter. Sikorsky previously had indicated the maximum speed was 250 knots.

The S-97 Raider helicopter program is the follow-on program to the X2 technology demonstrator. Sikorsky research and engineering v-p Mark Miller said the program will enable the U.S. military “to evaluate the viability of a fast and maneuverable next-generation rotorcraft.” The program will produce two prototype attack aircraft with six-passenger cabins and the ability to carry armament. The target cruise speed is 220 knots.

“The X2 program also has helped to develop the next generation of Sikorsky engineers, including some who are now in key positions on the S-97 Raider program and the Firefly electric helicopter program,” Sikorsky president Jeff Pino said. Started in 2005, the X2 was a $50 million effort.