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Virgin Galactic virgin (Findings (The unlocking of the feather during the…
Virgin Galactic 
What Happened?
On October 31 2014, the Virgin Galactic's SpaceShip2 (SS2) broke apart over the Mojave Desert during a test flight (Gander 2015), resulting in the death of the co-pilot Michael Alsbury and the serious injury of the pilot, Peter Siebold. The incident occurred after the co-pilot unlocked the crafts re-entry feathering system too early, causing the feather system to extend uncommanded, causing catastrophic structural failure (NTSB 2014).
Why it Happened?
the SS2 was equipped with a feather system that rotated a feather flap assembly to stabilise the SS2's altitude and increase its drag during re-entry to the earth's atmosphere (NTSB 2014).
The pilot was to unlock the feather system during the boost phase when the SS2 reached a speed of 1.4 Mach.
The feather was to be unlocked at this point to mitigate the hazard resulting from re-entry with the feather down due to lock failure (NTSB 2014).
The cockpit camera showed the co-pilot unlocked the feather too early, after the SS2 had reached a speed of 0.8 Mach.
According to the NTSB 2014, '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 the transonic region. As a result the feather extended un-commanded causing the structural failure'.
The hazard analysis conducted before the launch did not identify and describe hazards that could result from human errors. The analysis did not account for the possibility that a pilot might prematurely unlock the feather system. Instead, it was assumed that the pilots would correctly operate the feather system every time (NTSB 2014).
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Findings
The unlocking of the feather during the transonic region resulted in the catastrophic structural failure.
The co-pilot was experiencing high workload stress and was expected to recall tasks from memory while performing under time pressure, with vibrations and loads that he had not recently experienced. This increases the opportunity for error.
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The system safety analysis correctly identified that un-commanded feather operation would be catastrophic during the boost phase of the flight. However, the analysis was inadequate becaused it failed to identify that a single human error could lead to the unintended feather operation of the boost phase, and it failed to consider the need to more rigorously validate the effectiveness of mitigation errors.
by not considering human error, opportunities were missed to identify the design and operational requirements that could have mitigated the consequences of human error during the flight.
It was not ensured that the pilots adequately understood the risks of unlocking the feathering system early.
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There was pressure to approve the experiment permit application within 120 days, which interfered with the Federal Aviation Administrations ability to thoroughly evaluate the SS2's permit application.
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