On August 2, a Sikorsky’s S-97 Raider test flight helicopter experienced a hard landing caused by issues with the flight control software as the aircraft was hovering at the Sikorsky Development Flight Center in Palm Beach County near Jupiter, Florida.
At the time, the S-97 was preparing for an expansion of its flight envelope with the intention to reach 220kts (407km/h). The two test flight pilots were slightly injured in the incident, according to a National Transportation Safety Board (NTSB) preliminary report into the incident. The aircraft’s retractable landing gear was significantly damaged.
In a conference call for the press, Chris Van Buiten, vice president of Sikorsky Innovations, said the company was “fully committed to the program”. It will be returning the Raider program to flight testing in 2018 after the NTSB investigation is over.
Van Buiten said the “complex interaction between the ground, the landing gear, the flight control system, and the associated pilot interactions” as the fly-by-wire Raider transitioned from operating on the ground to flight were the possible source of the problems.
“We have been able to reproduce the event in our simulator and we are confident in operating with the NTSB to get to the root cause and fully understand the issue,” said Van Buiten.
Based on the X2 demonstrator, Sikorsky’s Raider made a first flight on May 22, 2015. The two aircraft share technologies such as rigid coaxial main rotors and a variable-pitch pusher propeller, the latter is used to increase speed and its maneuverability.
Van Buiten said, “The flight control software issue has nothing to do with the X2 technology itself. Remember the Raider is an all-composite fuselage, aircraft-retractable landing gear, crashworthy seats, crashworthy fuel system, and we’re just delighted with how all of those systems behaved in the event.
“The landing gear sustained significant damage, but the flight crew sat in the cockpit, shut off the engines, shut off the electrical system, just checked things out, routinely opened the egress doors, climbed out of the helicopter, walked up to the test crew and started talking about the event.”
Sikorsky has been using the Raider as a ‘risk reducer’ for the Sikorsky-Boeing SB-1 Defiant due to the latter’s flight software. Analysis is continuing as to whether the Defiant’s flight software needs modification.
Sikorsky has more than 30 industry partners and suppliers on the Raider program, and Van Buiten said it is keeping them updated on the investigation and the program’s development “within the confines of the NTSB-releasable information.”
Sikorsky was in the process of expanding the Raider’s flight envelope at the time of the incident, having recorded over 100 hours of ground runs and 20 hours of flight testing on the aircraft.
September 14, 2017