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SpaceShipTwo Pilot Was Unaware Co-Pilot Had Unlocked Brakes
LOS ANGELES (AP) — The pilot of the Virgin Galactic spaceship that tore apart over the Mojave Desert didn’t know his co-pilot had prematurely unlocked its brakes, despite protocol requiring the co-pilot to announce the step. Pilot Peter Siebold told the National Transportation Safety Board that he wasn’t aware co-pilot Mike Alsbury unlocked the brakes before the rocket was done accelerating. Seconds later, SpaceShipTwo began to disintegrate. (losangeles.cbslocal.com) More...
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I know SS2 is an extreme example, but AFR447 also demonstrated that ineffective communication amongst flight crew can have disastrous consequences.
Very much so....
A couple of comments. First, "brakes" is a misleading term in this context. Should at least be "airbrakes". The feathering system is to add drag on reentry from space to keep the speed down so the composite airframe doesn't overheat on re-encountering the atmosphere. That would cause it to delaminate, resulting in the loss of the craft and its occupants.
Next, the feathers need to be unlocked within a narrow window during the burn. The book calls for them to wait until Mach 1.4 but feather unlocking capability has to be confirmed before reaching a certain speed, because as noted, the feathers must work on reentry. If the unlocking fails during this ascent window, the flight has to be aborted.
Now it appears the feathers were unlocked at Mach 1.04, still in the transonic buffeting range. The changing and unpredictable airflow in that range may have overcome the actuators' ability to hold the feathers in position till actual deployment is commanded. The reason for the "early" unlock is still not known, could be a faulty Mach reading, could be cockpit vibration made it hard to read the display (hybrid motors tend to set up harmonic vibrations), could be PE.
On top of all that, although neither the nitrous tank nor the motor chamber apparently ruptured/exploded, some photos seem to indicate there may have been some sort of failure in the plumbing. That would've overpressured the airframe and caused a rapid disassembly. So the jury's still out.
One more point, there's no ejection system, just personal chutes. The surviving pilot found himself in midair after the cabin disintegrated around him -- at 50K feet, without a pressure suit, and (apparently) without O2. He's lucky to still be with us.
Next, the feathers need to be unlocked within a narrow window during the burn. The book calls for them to wait until Mach 1.4 but feather unlocking capability has to be confirmed before reaching a certain speed, because as noted, the feathers must work on reentry. If the unlocking fails during this ascent window, the flight has to be aborted.
Now it appears the feathers were unlocked at Mach 1.04, still in the transonic buffeting range. The changing and unpredictable airflow in that range may have overcome the actuators' ability to hold the feathers in position till actual deployment is commanded. The reason for the "early" unlock is still not known, could be a faulty Mach reading, could be cockpit vibration made it hard to read the display (hybrid motors tend to set up harmonic vibrations), could be PE.
On top of all that, although neither the nitrous tank nor the motor chamber apparently ruptured/exploded, some photos seem to indicate there may have been some sort of failure in the plumbing. That would've overpressured the airframe and caused a rapid disassembly. So the jury's still out.
One more point, there's no ejection system, just personal chutes. The surviving pilot found himself in midair after the cabin disintegrated around him -- at 50K feet, without a pressure suit, and (apparently) without O2. He's lucky to still be with us.
Well done MF Thank you. Your comments are very illuminating esp. the 1.4 vs 1.04!
While I don't take issue with your comments nor analysis, I do think you're underestimating the people on this site. Most are pretty intelligent professional pilots with a sprinkling of talented, inventive and smart maintenance professionals. I would pit most of them with aeronautical engineers in discussions.
I think every one here understands that brakes is a shortened version of the term, and the feathering system was pretty well defined in the article. The rest of what you write is redundant to the article as well other than the pilot surviving free fall from
fl 50.0.
It's obvious that the investigation is in it's rudimentary stages as the first order of business is to interpret the information from the black boxes which I'll remind you are not black at all. I mentioned in a posting below that NTSB has not yet but will listen to the CVR tapes, which may or may not be tapes, next week. That information should solve many questions and bring new ones to the table, which table is non-existent.
I think every one here understands that brakes is a shortened version of the term, and the feathering system was pretty well defined in the article. The rest of what you write is redundant to the article as well other than the pilot surviving free fall from
fl 50.0.
It's obvious that the investigation is in it's rudimentary stages as the first order of business is to interpret the information from the black boxes which I'll remind you are not black at all. I mentioned in a posting below that NTSB has not yet but will listen to the CVR tapes, which may or may not be tapes, next week. That information should solve many questions and bring new ones to the table, which table is non-existent.
Were we looking at the same article? None of the details in my post are in the skeletal mass-media article linked above, nor in any of the posts below. The feathering system is unique to SS1 and 2 and doesn't have any precise counterpart in airbreathing aircraft, so I felt some details might be helpful. Clarity and specificity are good things, wouldn't you agree?
I'm well aware that many posters here are professionals with the training and expertise you cite, and that's one reason I don't submit idle, speculative posts. Here my intention was to provide information not found in the article or in these comments, at a level that wasn't disrespectful to this readership -- let alone condescending, as your reply comes pretty close to being.
One of *my* areas of expertise is hybrid rocket motor design, and there's considerable discussion in other forums related to VG's motor design and testing decisions -- but that, I did indeed deem "off-point" in this forum.
I make no pretense of being a mindreader and have no way of determining what posters or readers may already know, except for the contents of the posts themselves. I'm well aware that the NTSB investigation has only begun, which is precisely why I noted that "the jury is still out". I offer no apologies for my post.
I'm well aware that many posters here are professionals with the training and expertise you cite, and that's one reason I don't submit idle, speculative posts. Here my intention was to provide information not found in the article or in these comments, at a level that wasn't disrespectful to this readership -- let alone condescending, as your reply comes pretty close to being.
One of *my* areas of expertise is hybrid rocket motor design, and there's considerable discussion in other forums related to VG's motor design and testing decisions -- but that, I did indeed deem "off-point" in this forum.
I make no pretense of being a mindreader and have no way of determining what posters or readers may already know, except for the contents of the posts themselves. I'm well aware that the NTSB investigation has only begun, which is precisely why I noted that "the jury is still out". I offer no apologies for my post.
Once again MF...you're right on target!
As I continue to watch/learn I am a bit surprised at the apparent "tenderness" of the airframe components. My area of knowledge is the RF4-C "Phantom". The slowest one I ever flew easily attained mach 2.37 and you could readily maneuver at that speed with absolutely no fear of structural problems; and that included use of the speed brakes. I realize you addressed this in your third sentence....this is just a comment.
As I continue to watch/learn I am a bit surprised at the apparent "tenderness" of the airframe components. My area of knowledge is the RF4-C "Phantom". The slowest one I ever flew easily attained mach 2.37 and you could readily maneuver at that speed with absolutely no fear of structural problems; and that included use of the speed brakes. I realize you addressed this in your third sentence....this is just a comment.
I appreciate the language you chose in your post. I'm a student pilot. What you wrote allowed me to understand and kept it very basic. Thank you! Anthony
