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Virgin Galactic Accident

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  • elaw
    replied
    Originally posted by Gabriel View Post
    I wonder if the "lock/unlock" handle just locks the "feather" handle to prevent that the "feather" lever is unintentionally moved (but moved) by the crew, or it actually mechanically locks the feather in the "normal" position
    IMHO the answer should be "both"! Given the apparent serious consequences when the system deploys at the wrong time.

    On an unrelated note: does anyone know what the criteria/rules are for when the NTSB does or does not investigate an accident such as this?

    They obviously investigate airplane accidents, but I don't think they've ever investigated one involving a NASA spacecraft, nor do I think they're investigating the recent Antares rocket failure.

    Leave a comment:


  • Gabriel
    replied
    So, this is a two-barrier system. There is a "lock/unlock" lever and another "feather" lever and you have to move both of them, in sequence, to go to the feather configuration. According to the NTSB, the first lever was moved but the second not, and per intended design the feather should have stayed in the normal position with that action alone. If that's correct, then pilot error" alone doesn't explain it (even if we narrowly look just for the immediate cause).

    I wonder if the "lock/unlock" handle just locks the "feather" handle to prevent that the "feather" lever is unintentionally moved (but moved) by the crew, or it actually mechanically locks the feather in the "normal" position to prevent a known potential failure mode that would cause the ship to go in the feather config even without touching the feather lever.

    Leave a comment:


  • Brainsys
    replied
    Originally posted by Evan View Post
    In answer to my own question, this was reportedly their only operational testbed. A number of others are being assembled but no word on when they will have another testbed to proceed.
    The report I read (sorry cannot recall the source) was that another spaceframe(?) was 65% complete and they would continue building. I guess one of the issues is that the investigators must want to see what a real cockpit looks and feels like. Something you can't always get from drawings or computer simulations. Especially if human factors are at issue here - the premature unlock.

    As for unscheduled deployment - do we presume the 'shock' around mach 1.0 may have triggered something? A reason to keep it locked till safely through that zone?

    Leave a comment:


  • Highkeas
    replied
    This site gives a good description of the planned flight trajectory for Spaceship Two. The "feathers" are used only after the vehicle has reached apogee.
    http://blogs.scientificamerican.com/...ed-tails-work/

    To rotate the "feathers" through 90 degrees then return them there must be an actuator mechanism. My guess is that this mechanism either failed or it received a premature activation signal.

    Leave a comment:


  • Evan
    replied
    In answer to my own question, this was reportedly their only operational testbed. A number of others are being assembled but no word on when they will have another testbed to proceed.

    Leave a comment:


  • Gabriel
    replied
    NTSB press conference:
    https://www.youtube.com/watch?v=vjYV...ature=youtu.be

    Main points, in chronological order:
    - The ship released normally from the mother ship.
    - The engine ignited normally.
    - The "lock-unlock" lever for the feather position was moved by the copilot from the locked to the unlocked position (confirmed by telemetry and in-cockpit video), when the speed was about M 1.0. He was not supposed to do that until they reached M 1.4 at a higher altitude (which, I presume, regardless of the higher speed, would impose lesser aerodynamic forces due to the lower air density, but this act by itself should not result in the feathers moving anyway).
    - The "feather" handle was not moved (conformed by in-cockpit video). For the feathers to be moved into the "feather" position both actions are required by design (at least as intended): That the "lock-unlock" lever is moved to "unlocked" and that the "feather" lever is moved to the "feather" position.
    - Yet, the feathers moved uncommandedly to the "feather" position (confirmed by telemetry and video from outside).
    - The ship broke apart 2 seconds later.
    - The fuel tank, oxidizer tank and engine were recovered intact with no signs of breach or burn through.

    I loved the last question: "Can this happen to another airplane?"

    Leave a comment:


  • AVION1
    replied
    Originally posted by brianw999 View Post
    Either or really. The craft is designed to go into space so this would be the most appropriate forum. More important really about all this is that another person has lost their life advancing the bounds of aviation.
    I agree with you Brian. This accident reminds me the two Space Shuttle Accidents (Columbia and Challenger) and also a reminder that Space exploration is not accident free.

    Leave a comment:


  • Alessandro
    replied
    Originally posted by guamainiac View Post
    Is it at all possible with such an engine, as opposed to a solid fuel motor, that such a slow down may cause a momentary surplus of unburnt fuel that suddenly ignites.

    It also sounds like they have a very basic problem with cockpit ergonomics if such a control fell so readily to hand. A friend of mine worked on part of the instrument placement for a B-1 component and if it was looked at by one it was looked at by 20 engineers before the pilots got to tear it apart so as to avoid such errors.
    Well, their budget is a tad bigger than this project.

    Leave a comment:


  • guamainiac
    replied
    Is it at all possible with such an engine, as opposed to a solid fuel motor, that such a slow down may cause a momentary surplus of unburnt fuel that suddenly ignites.

    It also sounds like they have a very basic problem with cockpit ergonomics if such a control fell so readily to hand. A friend of mine worked on part of the instrument placement for a B-1 component and if it was looked at by one it was looked at by 20 engineers before the pilots got to tear it apart so as to avoid such errors.

    Leave a comment:


  • Evan
    replied
    Originally posted by guamainiac View Post
    It looks like the engine continued on unless that is a smudge or distortion
    The early report today suggests that they configured it for the glide while still accelerating under thrust and apparently this caused the airframe to fail. There is something like an unlock lever and a deploy lever and the copilot deployed the unlock lever and then the configuration deployed without the second lever being touched. Part pilot error, part system malfunction, apparently. I guess the good news is that the engine and fuel were not at fault and the system malfunction should be fairly easy to fix.

    Does anyone know if this was their only 'spaceworthy' airframe?

    Leave a comment:


  • Highkeas
    replied
    Yesterday's NTSB briefing is available here:
    https://twitter.com/NTSB
    Give a description of the "feather" system.

    Leave a comment:


  • Brainsys
    replied
    More from The Register:

    “About nine seconds after the rocket engine ignited, the telemetry data showed us that the feather parameters changed from lock to unlock," Hart explained. "In order for this action to be commanded by the pilots, two actions must occur: the lock/unlock handle must be moved and the feathering handle must be moved to the feather position."

    According to Hart, cockpit video showed that co-pilot Michael Alsbury manually unlocked the feather system but didn't then select feather mode on the feathering handle. However the tail booms nonetheless folded upwards and the craft cracked up.

    “Approximately two seconds after the feathering parameters indicated that the lock/unlock lever was moved, the feathers moved toward the extended position, even though the feather handle itself had not been moved," Hart went on. "This occurred at a speed just above approximately Mach 1.0. Shortly after the feathering occurred, the telemetry data terminated and the video data terminated."


    More here: http://www.theregister.co.uk/2014/11..._tragic_crash/

    If it were caused by an unscheduled deployment then the cause (software or mechanical) should be straightforwardly fixable. Unlike a dodgy rocket motor. That may make it more likely that the programme is technically recoverable. Though whether the market in rich superstars has been smashed with the airframe is another matter.

    Leave a comment:


  • Alessandro
    replied
    Originally posted by Brainsys View Post
    The BBC is reporting "Air safety chief Christopher Hart said the "feathering" device, designed to slow the craft on re-entry, activated without a command from the pilots. But he said it was too soon to confirm any possible cause of the crash.

    Looking back at the photos the 'wings' do seem far out compared with the recessed configuration on release. While that could be the effect of an explosion the bits that fell to earth don't seem to have suffered too badly from burn marks.

    So it might not have been the motor. Shows the danger of jumping to 'obvious' conclusions. Time will tell.

    http://www.bbc.co.uk/news/world-us-canada-29876154
    Too violent shaking and the component couldnīt withstand it?

    Leave a comment:


  • Brainsys
    replied
    The BBC is reporting "Air safety chief Christopher Hart said the "feathering" device, designed to slow the craft on re-entry, activated without a command from the pilots. But he said it was too soon to confirm any possible cause of the crash.

    Looking back at the photos the 'wings' do seem far out compared with the recessed configuration on release. While that could be the effect of an explosion the bits that fell to earth don't seem to have suffered too badly from burn marks.

    So it might not have been the motor. Shows the danger of jumping to 'obvious' conclusions. Time will tell.

    http://www.bbc.co.uk/news/world-us-canada-29876154

    Leave a comment:


  • Gabriel
    replied
    Originally posted by brianw999 View Post
    Either or really. The craft is designed to go into space so this would be the most appropriate forum. More important really about all this is that another person has lost their life advancing the bounds of aviation.
    Gotcha. Had missed the "space" part of this forum.

    Leave a comment:

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