NTSB Hits Design of SpaceShipTwo in Crash Report
The aircraft was destroyed and the copilot died in the October 2014 crash. NTSB concluded the possibility that a single human failure could cause the suborbital rocket to crash was not considered.
The National Transportation Safety Board's July 28 hearing on the Oct. 31, 2014, crash of Virgin Galactic's SpaceShipTwo concluded that Scaled Composite LLC's failure to consider and protect against human error and the copilot's premature unlocking of the spaceship's feather system as a result of time pressure and vibration and loads that he had not recently experienced caused the crash.
The crash during a rocket-powered flight killed the copilot and seriously injured the pilot and spread debris across a five-mile areas near Koehn Dry Lake, Calif. The launch was operating under an experimental FAA permit; Scaled Composite had developed the vehicle for Virgin Galactic so the latter could provide commercial space suborbital excursions.
But the vehicle's feather system, which operated to stabilize its attitude and increase drag during reentry into Earth's atmosphere, was designed to be activated at 1.4 Mach, at an altitude of about 46,400 feet. "However, a forward-facing cockpit camera and flight data showed that the copilot unlocked the feather just after [the vehicle] passed through a speed of 0.8 Mach. Afterward, the aerodynamic and inertial loads imposed on the feather flap assembly were sufficient to overcome the feather actuators, which were not designed to hold the feather in the retracted position during the transonic region. As a result, the feather extended uncommanded, causing the catastrophic structural failure," the board found.
In its hazard analysis, "Scaled did not account for the possibility that a pilot might prematurely unlock the feather system, allowing the feather to extend under conditions that would cause a catastrophic failure of the vehicle structure. Instead, Scaled assumed that pilots would correctly operate the feather system every time because they would be properly trained through simulator sessions and would follow the normal and emergency procedures for a given situation. However, this accident demonstrated that mistakes can occur even with a flight crew member who had extensive flight test experience and had performed numerous preflight simulations during which the feather was unlocked at the proper speed of 1.4 Mach. Lack of human factors guidance for commercial space operators. Scaled did not emphasize human factors in the design, operational procedures, hazard analysis, and simulator training for [the vehicle]," the board concluded.
One of the board's findings was that the Federal Aviation Administration Office of Commercial Space Transportation's evaluations of Scaled Composites' initial and first renewal of the SpaceShipTwo experimental permit application "were deficient because the evaluations failed to recognize that Scaled Composites' hazard analysis did not meet regulatory requirements to identify hazards caused by human error."