Virgin Galactic SpaceShip Two crashed?

[MartG]

KTF said:

If it only takes a matter of seconds to go from mach 1 to 1.4, maybe the pilot was slightly too quick to pull the unlock lever?

Possible instrumentation fault - did he think they were already at mach 1.4 ?

[MartG]

Scuffers said:

the rocket that failed last week was SFA to do with NASA

they are a private company using Russian rocket motors built in the 70's and recently refurbished, checked and tested by a US company.

Fixed that for you

[Scuffers]

MartG said:

Scuffers said:

the rocket that failed last week was SFA to do with NASA

they are a private company using Russian rocket motors built in the 70's and recently refurbished, checked and tested by a US company.

Fixed that for you

LOL! pedants matter!

http://en.wikipedia.org/wiki/NK-33 - "built in the late 1960s and early 1970s"

http://en.wikipedia.org/wiki/NK-33#Antares - "it has a stockpile of 23 1960s and 1970s era engines"

so, basically we are talking about at best, 40+ year old Russian rocket motors that have been cleaned up and re-wired.

[KTF]

Pprune forum said:

Dynamic pressure is greatest at transonic flight (Max Q), then reduces as the aircraft goes supersonic and accelerates past Mach 1.2.

So for safety, the feathering mechanism must be locked when flying through this region. Otherwise, the aerodynamic forces can twist SS2 into feather mode.

Which is what apparently happened.

[Eric Mc]

Fits in very well with all the comments made so far.

Thanks for posting that - it all makes sense.

The trouble at the moment is that we have three interesting threads running on PH on the accident - one here, one in the "Science" forum and another in "Planes, Boats, Trains" forum. It's hard keeping track of them all.

[-Z-]

The raw footage from earlier test flights including feathering is fascinating:

http://m.youtube.com/watch?v=1ZVDuRS7Jy8

[davepoth]

Scuffers said:

kind of implies the device is automatic, once the pilots enable it, and for whatever reason, it triggered when enabled.

IIRC (and it was a long time ago) the idea behind it was that even if everyone onboard was incapacitated for some reason, the craft would re-enter the atmosphere safely and stably. After Mach 1.4 the air acts to keep the feathers in position, meaning that it doesn't have to be locked to fly safely, so the idea is that once that speed is passed nobody really needs to fiddle with the controls.

[hidetheelephants]

I'm surprised if the wing lock doesn't have any interlocks on it, to have such a control without them seems like an accident waiting to happen. If it's not supposed to occur unless the speed is over M1.4 then there ought to be an interlock preventing it.

[Scuffers]

hidetheelephants said:

I'm surprised if the wing lock doesn't have any interlocks on it, to have such a control without them seems like an accident waiting to happen. If it's not supposed to occur unless the speed is over M1.4 then there ought to be an interlock preventing it.

Why it's not a prototype test pilots supposed to know this stuff

[-Z-]

hidetheelephants said:

I'm surprised if the wing lock doesn't have any interlocks on it, to have such a control without them seems like an accident waiting to happen. If it's not supposed to occur unless the speed is over M1.4 then there ought to be an interlock preventing it.

There was an interlock. It was a manually operated one (to prevent erroneous activation?) that was, possibly, incorrectly operated.

I'm guessing most test craft would have manually operated systems to reduce the chance of immature software causing a foul up. Also even if the intention is to automate, how do you where to set the parameters until you test it manually?

[davepoth]

-Z- said:

There was an interlock. It was a manually operated one (to prevent erroneous activation?) that was, possibly, incorrectly operated.

I'm guessing most test craft would have manually operated systems to reduce the chance of immature software causing a foul up. Also even if the intention is to automate, how do you where to set the parameters until you test it manually?

That's not an interlock. An interlock would stop the manual operation from happening until it is safe for it to happen; a common one at a factory is to stop a rotary saw from being switched on until the safety guard is down and locked.

you are correct that test craft tend to have fewer safety features and less automation than finished craft while the limits are worked out. That's why test pilots are usually the best of the best - they know when not to press buttons.

[MartG]

Scuffers said:

hidetheelephants said:

I'm surprised if the wing lock doesn't have any interlocks on it, to have such a control without them seems like an accident waiting to happen. If it's not supposed to occur unless the speed is over M1.4 then there ought to be an interlock preventing it.

Why it's not a prototype test pilots supposed to know this stuff

As I suggested earlier, maybe their instrumentation was showing faulty readings, and they thought they were already over Mach 1.4 - wouldn't be the first time a blocked pitot has caused a crash

[hidetheelephants]

Scuffers said:

hidetheelephants said:

I'm surprised if the wing lock doesn't have any interlocks on it, to have such a control without them seems like an accident waiting to happen. If it's not supposed to occur unless the speed is over M1.4 then there ought to be an interlock preventing it.

Why it's not a prototype test pilots supposed to know this stuff

Are you from the 1950s? This is basic human factors engineering, the lack of which was the cause of thousands of otherwise preventable deaths in air disasters in the 50s/60s/70s. 'Test pilots supposed to know this stuff', or even 'pilots supposed to know this stuff', and the inevitable 'must be pilot error', was the nonsense sold by aircraft manufacturers and other responsible organisations, until the likes of David Beaty forced them to recognise how stupid they were and why lots of people were dying pointlessly.