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SpaceShipTwo's Rocket Engine Did Not Cause Fatal Crash
astroengine writes It wasn't SpaceShipTwo's hybrid rocket motor — which was flying on Friday with a new type of fuel — that caused the fatal crash, the head of the accident investigation agency said late Sunday. The ship's fuel tanks and its engine were recovered intact, indicating there was no explosion. "They showed no signs of burn-through, no signs of being breached," Christopher Hart, acting chairman of the National Transportation and Safety Board, told reporters at the Mojave Air and Space Port in Mojave, Calif. Instead, data and video relayed from the ship show its hallmark safety feature — a foldable tail section designed for easy re-entry into the atmosphere from space — was deployed early, causing the in-flight break-up.
Last week saw the Orbital Sciences Antares explosion on Tuesday, this fatal Virgin Galactic crash on Friday, and a plane crash in Wichita on Thursday that killed 4 (The pilot, and 3 in the building it crashed into).
Hopefully we have some good weeks ahead to balance this.
Right, he may very well have been trying to save it by doing that. Or scrambling unsuccessfully to find the eject lever.
Supposed SOP was to unlock (NOT DEPLOY, unlock) the feather at Mach 1.4.
Logic being that if it doesn't unlock, thrust is cut and the flight aborted. Past that point you are committed to climbing at such speed that the re-entry without the feathering system could be fatal.
Actual deploy would happen only past apogee and the feather mode would stabilize the fall and give high drag before the craft enters denser parts of the atmosphere.
For some reason the deploy happened uncommanded right after unlock and Bad Things followed (any feather deploy during powered flight is pretty much instant game over as the craft will unavoidably flip due to the thrust and breakup is almost guaranteed).
Why unlock the feathers during powered flight?
Because if you get into space and find you can't unlock them, the aircraft is going to burn up on reentry. So you unlock them during powered flight. If they don't unlock, you can shut down the engines and still have enough atmosphere to control the aircraft and direct it out of its trajectory into space.
Why do this during powered flight and not before, perhaps just before the aircraft is released from its carrier?
Because the aerodynamics and stress on the aircraft at engine start are dynamic to say the least. Once under stable, powered flight there's much less risk in unlocking the feathers. The aerodynamic loads should not be high enough that they would overcome the hydraulics keeping the feathers in place after being unlocked.
The big question right now is why did the feathers deploy. The NTSB says they saw nothing to indicate the pilots had tried to deploy them; the handle used to do this was untouched based on the internal cockpit video they have.
It's way too early to even speculate that it even might be pilot error. That the unlock happened a couple seconds early should not have caused the feathers to deploy on their own. Unless the transition to supersonic speed induces stresses that could overcome the hydraulics and force the feathers to deploy and the unlock happened just before or during that transition.
We need to find out why the feathers deployed before we start blaming anyone or anything.
I'll bet the cause will be something really simple and stupid and mundane, like a technician installing a bolt or a relay upside down.
I read in Bob Hoover's book, in the 50's a number of F-86's crashed when their ailerons locked up if the wings flexed a certain amount. It was due to an aileron bolt mounted upside down. They traced the source to one technician at North American factory who, when interviewed said of course he knows how those damn bolts are supposed to go, he's been doing it that same way for 15 years, ever since before WW2!
They didn't have the heart to tell that guy how many pilots he killed.
Coincidentally in Chuck Yeager's book, he tells the story of a pilot in his F-86 squadron -- at the time Yeager was the squadron commander -- named Emmett Hatch. (Hatch was the lone black pilot in the squadron). He was coming down on approach one day, was feeling good so he did some rolls. Then his ailerons locked up, lost all control and had to eject.
The wing commander was a man named Col. Ascani, a really meticulous numbers guy who was obsessed with keeping the accident numbers down. When the Col. heard about this accident he went ballistic and poor Emmett was going to have his azz court-martialed. So when the Col. asked Yeager, "Why the hell was Hatch doing a roll down so low?"
Yeager replied, "All ours pilots do that, we do a roll on final approach to make sure we're not landing on top of somebody else." And so he saved Emmett's career.
There is an interesting counterpoint to this in victorian era railway signalling systems.
Now the operator interface for these consisted of banks of levers that worked the signals and points by means of a system of wires running over pullys, visibility from the signalboxes was not always brilliant and especially in fog keeping track of what was where was problematic.
In a fit of absolute genius it was realised that the (mechanical) logic could be implemented so as to prevent a signal being set at green if the segment was occupied and also to prevent the points in an occupied section being moved (this in an age before Turing, you will note). This was clearly a good thing, right?
Well, the signal men protested that sometimes they had to do the unusual and that they were highly experienced professionals (all the usual) and the system was modified so that a special key could be used to override the interlock logic, this key being held by the supervisors office.
So many train crashes over the following few years featured that key, that it ended up being UK practise that any collision between trains that caused a fatailty would automatically result in the signalman being arrested on suspicion of manslaughter.
It is a fine line between stopping the professional applying an override to fix a critical situation and leaving them able to tear the wings off by accident.
Regards, Dan.
Does this rocket plane really require pilots?
No, probably not... most airplanes no longer "require" pilots in the sense that computers can do the job better, cheaper, and more reliability for the most part...
The question becomes, how many passengers TODAY would get onto an airplane with no human pilots? I would, because I know better. But most people don't know any better.
For a self-driving car I'm guessing the right emergency response is 90% braking, 9% turning, 0.9% accelerating to get out of harm's way and maybe 0.1% getting creative like unbuckling and bailing because the car's going over a cliff.
Self-driving cars are likely to be far safer and more reliable than human-driven cars. But tell that to the mother of the dead child killed in a self-driving car? She doesn't care that 20,000 fewer people are dead in these new cars, she only cares that HER child is dead.
Take helicopters... Here is an odd fact for you... More people are injured and killed practice autorotations than we have engine failures in helicopters.
An autorotation is what you do when the engine quits, it lets the helicopter glide to a safe landing (sort of glide, mostly drop, but it does work).
Frank Robinson, the owner of Robinson Helicopters (who makes the R-22 which is the most common training helicopter today) has said that he would prefer that practicing for this was no longer done for most pilot training.
And he is right, fewer people would die if we simply accepted that anyone in a helicopter that lost the engine would just die with 100% certainty than by requiring helicopter pilots to keep practicing this over and over.
Fully 1/4 of helicopter pilot training is practicing for losing an engine, something that doesn't actually happen to most pilots over their entire careers. Lots of pilots are hurt during training while practicing it however.
But humans have a problem with picking any path that has a 100% certainty of death, regardless of how many people actually die on the path that is not certain.