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Poor Pilot Training Blamed For Virgin Galactic Crash
astroengine writes: SpaceShipTwo co-pilot Michael Alsbury was not properly trained to realize the consequences of unlocking the vehicle's hinged tail section too soon, a mistake that led to his death and the destruction of the ship during a test flight in California last year. Responsibility for the accident falls to SpaceShipTwo manufacturer Scaled Composites, a Mojave, Calif., company owned by Northrop Grumman Corp, the National Transportation Safety Board (NTSB) determined at a webcast hearing on Tuesday (PDF). Poor oversight by the Federal Aviation Administration, which oversees commercial spaceflights in the United States, was also a factor in the accident, the NTSB said.
If there was a criteria for safe unlocking of the hinged tail section then why wasn't it interlocked until the criteria was satisfied?
A bigger error here is reliance on operator training. It's the least reliable form of ensuring a certain outcome.
From the report:
The unlocking of the feather during the transonic region resulted in uncommanded feather operation because the external aerodynamic loads on the feather flap
assembly were greater than the capability of the feather actuators to hold the assembly in the unfeathered position with the locks disengaged.
So maybe the copilot thought that he was preparing for the future feathering operation by unlocking it, and he did not think he was initiating the feathering. Usually an "unlock" switch is only a permissive, and it does not initiate the actual operation.
It's interesting as the unique tail section was actually touted as a "safety feature" by the company. I'm not necessarily saying it can't be the case, but like any feature, even a safety feature (see: exploding airbags), defects or improper use can cause more harm than in it's absence.
The moveable booms are intended to provide a fail-safe mechanism for positioning SpaceShipTwo during the fiery re-entry into the atmosphere. Scaled pilots were well aware of what could happen if they unlocked the feather too late, but training about its early release were ignored, accident investigations found.
It's a bit strange, as it seems like such a fundamental error - not some obscure feature that could be overlooked. What pilot would say to himself "Hey, I know I'm supposed to unlock the tail at time X, but what the hell, why not just do it now?" It seems really strange that they wouldn't have precise procedures for this, since it's such a critical part of the entire design.
It's a hard way to learn a lesson like this.
Irony: Agile development has too much intertia to be abandoned now.
That's pretty standard for all aviation training. Flying is easy, much easier than driving in a lot of ways. Not killing yourself is a lot harder. That's why pilots have reams and reams of checklists covering pretty much every conceivable problem that can happen. Similarly when training in a simulator, the operators can pretty much throw the book at you to see how you react to losing all your instruments and a wing while flying through a thunderstorm.
NASA's generic rulebook is over 2000 pages long and is well worth a flick through if you're a space geek http://www.jsc.nasa.gov/news/c...
It appears that unlocking it just allowed dynamic forces outside the craft to move the feather without being commanded to. The external forces simply overcame the mechanical system that was holding it retracted. A transonic slipstream exerts a hell of a force.
In my view this is a dual failure- a failure by the pilot who (apparently) wasn't trained on when not to unlock the system, and an engineering failure as well- it seems a common-sense thing to lockout potentially (or positively) fatal mis-operations. I'm sure that one or more existing sensors could have been used to prevent unlocking the feather if current conditions could/would cause a catastrophe.
And yes, I'm playing Monday-morning quarterback, and yes, I have the benefit of hindsight, but still- foreseeing the "what could go wrong" possibilities is what good engineering is all about.
Just cruising through this digital world at 33 1/3 rpm...
You're an experienced test pilot of a rocket powered ship and you have to be specifically trained to anticipate the effects of slamming on the brakes while traveling at supersonic speed?
As touched on in a comment above, he didn't deploy them, he unlocked them. As I understand it, he unlocked them too early, so the deployment mechanism was unable to prevent them from deploying under the stress of supersonic flight at relatively low altitude.
You want to unlock them early, because, if you can't unlock them, you can still cut the engine and glide back. You don't want to unlock them too early, because this happens.
No laws were broken. There is no way to levy a fine. The NTSB is not in the business of fining individuals or organizations for violating rules or laws. That's the job of the FAA and other various agencies that oversee road vehicles, trains, and boats.
The NTSB does their best to identify the probable cause(s) of the incident, what factors led up to that incident, and, most importantly, what measures to take to prevent any future incidents. It's up to agencies, like the FAA in this case, to implement suggestions from the NTSB.
In this case, most of the blame appears to fall on the FAA.
It appears that deploying the feather was a multi-step operation. The flap covering the feather is unlocked, then the flap is opened, then the feather is deployed. The pilot probably knew that the feather could not be deployed at the speed they were going, but did not know/understand that the flap could not stay closed if unlocked at the speed they were going. Thus, the pilot unlocked the flap, and from there, whatever other latch that made step 2 work broke, the flap opened and the feather deployed on its own.
Maybe the button will be renamed "Remove Restraints Holding Feather Flap Closed During Transonic Region".
I have read the NTSB Executive Summary. As far as I have seen, the full report has not yet been made available.
The claim made by the report is the accident was the result of human error because one of the pilots unlocked the feather prematurely and that the actuators that control movement of the feather were overcome by aerodynamic forces (while going through trans-sonic speeds) and the feather moved. Deploying the feather is a two-step process, unlocking, which one pilot can do, and commanding it to move, which require both pilots to take action.
What I didn't see in the Executive Summary was whether Scaled Composites expected the actuators to be able to control movement of the feather while the vehicle was going trans-sonic.
Just after the accident, there were statements attributed to Scaled that the actuators should have been able to hold the feather in position after it was unlocked. If the people working on and with the vehicle thought this, how could it be human error for the feather to be unlocked when it was?
If it turns out that those earlier statements were incorrect and Scaled knew that it was a bad idea to, say, unlock while going through trans-sonic, then the Executive Summary should have indicated that. I just find it odd that it doesn't say anything about what Scaled had communicated to its pilots about the capabilities of the actuators for the feather once it was unlocked.
In this case, most of the blame appears to fall on the FAA.
I would expect that it's classified as some sort of "Experimental" vehicle at this point, for which the usual rules do not apply. So I doubt the FAA has much to do with it either.
Even so: given the known design of the craft, how could he possibly NOT know that unlocking the tail section prematurely was dangerous? I mean, seriously. "Oh, sure, let's just let it flap in the breeze at a few thousand miles per hour. No big deal."
Sheesh.
I would expect that it's classified as some sort of "Experimental" vehicle at this point, for which the usual rules do not apply. So I doubt the FAA has much to do with it either.
No, TFS has it correct. It's classified as "Commercial Spaceflight," and the Federal Government deliberately moved jurisdiction from NASA to the FAA.