Virgin Galactic crash: co-pilot unlocked braking system too early, inquiry finds

The violent crash of Virgin Galactic’s SpaceShipTwo was caused by a combination of human error and inadequate safety procedures, a nine-month investigation by the National Transportation Safety Board has found.

SpaceShipTwo disintegrated within seconds during a test flight in the Mojave desert on 31 October, after a premature repositioning of the vehicle’s twin tail wings.

The vehicle was equipped with a “feathering system” to reduce its speed and stabilize its descent on return to earth, but the NTSB found that co-pilot Michael Alsbury – who died in the crash – unlocked the feathering system before the space plane had reached the right speed during the test flight.

Alsbury unlocked the feathering system at Mach 0.92 instead of at Mach 1.4, the intended speed. At that speed, lift from the horizontal tails exceeded the feather actuator’s ability to prevent a rapid aerodynamic extension of the feather system. The feather extended rapidly without further pilot action or mechanical malfunction.

Pilot Peter Siebold, who survived a 10-mile fall back to earth, was seriously injured in the accident.

NTSB investigator Katherine Wilson suggested Alsbury might have unlocked the system too early to prevent the flight from being aborted. The feathering system had to be unlocked by Mach 1.8 at the latest, or else the flight would have been aborted.

The NTSB said Scaled Composites, the manufacturer of SpaceShipTwo, did not consider the possibility of a pilot unlocking the feathering system too soon, and so did not build safeguards to prevent the accident.

On Tuesday, NTSB reiterated safety measures recommended to Scaled Composites.

Virgin Galactic had previously completed safety measures, including a modification to the feather lock system with an automatic mechanical inhibit to prevent unlocking or locking the feather during safety-critical phases of flight, and a change to the checklist and call-outs the pilots undergo before unlocking the system.An external review team is assessing the safety of Virgin Galactic and the Spaceship Company’s engineering, flight test and operations as well as SpaceShipTwo.

Following the crash in November, Sir Richard Branson said that his dream of commercial space tourism may have ended with the explosion that consumed Virgin Galactic’s test craft above California’s Mojave desert.

In a statement, Virgin Galactic said it had begun “safety reviews and a vehicle improvement program prior to the accident” in preparation for the launch of SpaceShipTwo’s commercial service.

“After the flight test accident, Virgin Galactic assumed full responsibility for the completion of the flight test program and is getting ready for commercial service.”

“Although we will never forget the tragic loss of Michael Alsbury, with the investigation completed, Virgin Galactic can now focus fully on a strengthened resolve to achieve our goals,” Virgin Group founder Branson said in a statement.