Sikorsky resumed test flights of its S-97 experimental compound helicopter last month with a second aircraft. The program was grounded after the first S-97 technology demonstrator sustained a hard landing and was substantially damaged at Sikorsky’s test facility in Jupiter, Florida, last August. The S-97 features a rigid coaxial main rotor system and an aft thruster and is designed to achieve forward speeds of up to 240 knots. The first S-97 had achieved a forward speed of 150 knots during a truncated flight test campaign. Sikorsky plans to fly the second S-97 to 200 knots by this summer’s end.

While the final NTSB report on last year’s accident is pending, Sikorsky blamed it on a “complex interaction between the ground, the landing gear, the flight controls system and the associated pilot interactions.” The company said it had subsequently made the necessary changes to the flight control software to prevent similar occurrences.

Sikorsky is building the S-97 both as a technology demonstrator for the Army’s Joint Multi-Role, Future Vertical Lift (FVL) program and as a possible candidate for a yet-to-be-defined FVL light aircraft. In that role, Sikorsky has conceived of the S-97 in four possible configurations; MH-97 troop assault and special operations; AH-97 reconnaissance and light attack; search and rescue; and RQ-97 autonomous reconnaissance and attack. For the FVL main competition, Sikorsky is partnering with Boeing to develop a larger version of the S-97, the SB-1 “Defiant,” which it hopes to fly later this year to eventually compete with the Bell V-280 tiltrotor. Sikorsky reported in April that it had achieved significant technical milestones related to the SB-1’s development including fashioning solutions to complex transmission issues related to power distribution between the main rotors and the thruster. 

According to the U.S. Department of Defense, the FVL program is designed to find a replacement for the Army’s Sikorsky UH-60 Black Hawks and the Bell UH-1 operated by the U.S. Marine Corps. The program ultimately could result in deliveries of as many as 4,000 aircraft by 2030 under a contract potentially worth $100 billion and include significant foreign military sales.