The Sikorsky-Boeing SB>1 Defiant helicopter program will miss its first scheduled flight tests due to "minor technical issues" discovered during ground power tests, officials involved in the program revealed Wednesday. The tests were originally scheduled for this year.
While the aircraft "has been completely built," discoveries were made in recent weeks during Power System Test Bed (PSTB) testing, said Rich Koucheravy, Sikorsky director of business development for future vertical lift. Sikorsky is partnered with Boeing Co. on the project.
"We're working those fixes, and our goal will be to get the PSTB back in operation shortly...within the next week or two," Koucheravy said in a phone call with reporters. Because of the prolonged PSTB tests, the Defiant flight will be pushed back into early 2019, he said.
Randy Rotte, Boeing director of global sales and marketing for cargo helicopters and FVL, said the program must also be certified in 15 unblemished hours within PSTB -- which collectively tests the aircraft as a system -- before it's cleared for first flight.
The two officials said the unspecified, mechanical issues have not and will not impact or alter the design or configuration of the aircraft, nor should they impact the supply chain.
Program officials previously reported problems with the transmission gearbox and rotor blades.
"Those issues are behind us," Rotte said Wednesday.
The co-developers have been transparent with the Army with the delays, they said. "Only time will tell" if other discoveries during prolonged ground testing will dictate when the flight tests occur, Rotte said.
The news comes one year after Defiant's competitor, the Bell Helicopter-made V-280 Valor next-generation tilt-rotor aircraft, made its first flight.
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In October, the head of the Army's Future Vertical Lift effort said the service was not worried that the Sikorsky-Boeing SB>1 Defiant had not conducted its first test flight yet.
"We need them to fly; we need them to prove out more fully their lift-off ... technologies and some of their manufacturing technologies," Brig. Gen. Wally Rugen, director of the Future Vertical Lift, Cross Functional Team, said during the 2018 Association of the United States Army Annual Meeting and Exposition.
But, he added, "we have been in close communication with the Defiant team and understand where they are at and what they are doing."
Sikorsky, part of Lockheed Martin Corp., and Boeing Co. built the SB>1 Defiant, which is based on Sikorsky's X2 coaxial design.
The Defiant was expected to conduct its first test flight in 2017, but Sikorsky-Boeing officials predicted it would instead conduct its maiden flight in late 2018 at the Sikorsky Development Flight Test Center in West Palm Beach.
Rugen at the time said it was still too early to say whether the service will lean toward the Valor's tiltrotor or the Defiant's coaxial rotor design.
"We want the most efficient and the most capable platform," he said.