This is an example of hypoxia, and how insidious it can be. It is also an example of how many ways it could have been preventable (how many errors were made, or missed opportunities to prevent the mishap). It is also an example of how mishaps often occur because of multiple factors. It is also an example how small things can lead to big problems.
Please note that this is all from recollection from years ago. I am sure there are some omissions, and I suspect some inaccuracy. I am definitely not a writer. If anyone has an audio recording of this mishap or any other documentation (suitable for the public), I would appreciate if you would contact me with a copy.
This mishap occurred before we knew much about hypoxia, rather than keep this embarrassing mishap a forgotten secret; it should be remembered and used as an example to prevent further accidents. Even though this was a military mishap much of the information applies to civilian aeronautics. Since this incident was military and part of military tests, it is the best-documented case of hypoxia I know of (as related to aerospace physiology). Sometimes military, professional, and technical bureaucracy can be a blessing.
——————–
Background.
——————–
The data was a montage of the “black boxes”, radio transmissions (including the victim/test pilot, the chase pilot, and ground controller) and testimony from the chase pilot.
The mission was to conduct spin tests. I think the test subject aircraft was an F-4. To observe the spin tests, they had a chase plane. The chase pilot was a friend of the test pilot.
——————–
Narration
——————–
There is a slight delay after starting up the aircraft. The test pilot makes a radio communication that he has having difficulty closing his canopy. After several tries he finally gets the canopy closed. They taxi out and take off, and form up.
After they are probably above 20,000 feet the chase pilot radios the test pilot notifies the test pilot that he (the test pilot) missed some checkpoints on the procedure. The test pilot responded with an ambiguous radio communication, that didn’t really resolve the issue or explain why he was apparently having problems.
A little later the test pilot missed a waypoint (turn and change altitude) (deviated from the flight plan and test). The chase pilot radioed the test pilot to notify the test pilot that he missed his waypoint. Either the test pilot didn’t respond or his response was vague again and I think he still continued to deviate from the flight plan/test. The flight path was slightly erratic.
Shortly after; the test plane started a gentle turn that subtly increased; the flight path became more erratic. The chase pilot radioed the test pilot to notify the test pilot, about the test pilot’s repeated and continued deviation from the flight plan/tests. After several radio inquiries from the chase pilot, to the test pilot, the test pilot still had not responded. The chase pilot became concerned that there might be a radio problem, so he changed frequencies to try to communicate with the test pilot, and the chase pilot also alerted the ground controllers, and ground controllers tried to contact the test pilot, in case there was some condition that prevented communications from the chase plane to the test pilot. But there still was no response from the test pilot. The chase pilot tried to get along the test pilots aircraft, but by that time the test plane was in a somewhat erratic hard turn, so the chase pilot really couldn’t get close enough to see the condition of the test pilot. (The chase pilot was confused, by the maneuvers and the course the test plane was doing. They were relatively close to their waypoint, and the turns were definitely not spin tests, but he thought the test pilot might have been trying to spin the aircraft but was having difficulties).
The test plane’s erratic turn slowly became much worse. The turn became an erratic let down (and started to lose considerable altitude). The letdown became a corkscrew spin (losing altitude at an alarming rate). When the test plane started to corkscrew spin, it became obvious that the test pilot was in serious trouble. (The corkscrew spin, is definitely not the type of spin they were trying to do) (the chase pilot called just called it a spin, how personally call a corkscrew spin to differentiate it from the type of spin intended, which I think was a flat spin)
The chase pilot and ground control continued to try to contact the test pilot, with no response from the test pilot. The chase plane followed the test plane, but the test plane was diving and flying so violently, the test pilot didn’t dare get close. The chase plane and ground controllers continued to try to radio the pilot, until the chase plane notified the controllers that the test aircraft had impacted the ground. The crash was so violent there was no chance of survival.
——————–
The mechanical investigation.
——————–
I think they found a valve that had stuck in the oxygen system. The design of the valve under certain conditions would allow a pilot to breathe 100% cabin air from the oxygen mask.
——————–
My critical analysis summary.
——————–
The mishap was a result of series of combinations of pilot error, design/engineering shortcomings, systemic procedural shortcomings and mechanical failures.
——————–
My critical analysis in more depth.
——————–
1: The first clue that there was a problem, was when the test pilot was having difficulty closing his canopy. That should have given the test pilot a hint/indication of a possible problem. Instead the test pilot ignored the warning, and repeatedly forced the canopy until it closed. Evidently the reason the canopy was not closing properly, is that it was not sealing properly; even though the canopy was closed the test pilot was breathing outside atmospheric pressure. When the test pilot closed the canopy, he should have checked his cabin altimeter/differential pressure (cabin pressure gauge), the evidence suggests he did not.
2: It seems the test pilot forgot to check the condition and function of his oxygen equipment. If the test pilot had used his emergency oxygen, to pressurize his mask, the pilot would have discovered that he wasn’t breathing aircraft oxygen, he was breathing cabin air. {(On military aircraft) The normal oxygen position/selection is virtually the same pressure as the cabin, the emergency position/selection allows for a slightly higher oxygen pressure. You can feel the relatively higher pressure of oxygen in the emergency position/selection, if you are not properly hooked up, it is not properly working, or if there’s a leak, you will not feel the pressure on your face. That’s why after you put on your oxygen mask it should be procedure to select the emergency oxygen position for a couple of seconds as a pressure test, then reselect normal.}
3: When the test pilot starting missing checkpoints and waypoints, that should/could have alerted the chase pilot that there was a possible problem.
The chase pilot should have asked the test pilot to check cabin altimeter/differential pressure (cabin pressure gauge), as a precautionary suggestion; as the question is productive and less likely to produce a resistive, denial, or combative reaction.
Chuck Yeager successfully detected hypoxia and intervened in a similar situation, thereby saving the pilot’s life. Aerospace physiology is part of a military training for crew that flies on high-altitude flights, part of that training is how to recognize symptoms in yourself or in other people. The symptoms can be much like alcohol, it can affect different people in different ways. Stupor, slurred speech, amnesia, feeling of well-being, overconfidence, loss of coordination, mental confusion, argumentativeness, ect…
Chuck Yeager was/is a smart cookie, he spotted a wingmen’s errors, he tried to alert is the pilot in distress, but the pilot in distress became combative, rather than to try to win an argument, Chuck Yeager used psychology, he used the pilot’s compassion to save him. Chuck Yeager made up a white lie/a diversion, Yeager said he had a flameout, which alerted the pilot in distress and fed on the distressed pilot’s sense of loyalty and compassion. So the pilot in distress followed Yeager to a lower altitude, where the pilot recovered without mishap.
http://www.youtube.com/watch?v=VnPWT5IWp74
4: When the chase pilot started to recognize that there was a problem, the chase pilot could have saved the day. The chase pilot was slow to investigate and respond. When the chase pilot started to notice there was problems he only continued to communicate by radio. Once it was clear that the test pilot was not responding to radio communications, I think the pilot should have ASP got up close and personal and take a good look at the cockpit, while continuing to try to hail the test pilot on the radio, lighting after burners might have brought the test pilot out of a stupor. If that failed the chase pilot could have possibly flown in front of the test pilots aircraft and created on the turbulence to wake the test pilot from his stupor. The most likely way to save an unconscious pilot in that condition, is also very dangerous. The chase pilot could have maneuvered his plane close enough to disturb the lift on one of the tips of the test pilot wing, to roll the aircraft. It is an old trick that the British used to use in WWII to crash buzz bombs.
Unfortunately the test pilot did not recognize the symptoms soon enough or act quickly enough. If the chase pilot would have been more alert, lucky and quicker; the chase pilot might have been able to roll the test pilots plane shortly after he lost consciousness. The maneuver may have waken the test pilot out of his stupor, either by shock, or the loss of altitude might have gotten the test pilot to denser air in time to recover.
Since the chase pilot did not recognize the symptoms and act soon enough the plane went into a turn that would’ve been too dangerous to respond.
The test pilot went into a stupor from hypoxia, without an immediate response from the chase plane (which could have given him a slight chance of survival), instead the test pilot went into stupor, then unconsciousness, possibly coma, that virtually guaranteed his death. After the pilot lost consciousness the plane eventually went into a spiraling spin, which is typical. The spiraling spin from a high performance aircraft tends to produce high Gs so even when the victim gets to a lower altitude to the thicker air where more oxygen can get to the lungs. Typically high-performance aircraft are pulling so many Gs spiraling that even though the oxygen can get to the lungs, the G force is preventing the blood/oxygen from reaching the brain.
I think when the plane started its gentle turn is when the test pilot lost consciousness. The longer a pilot remains unconscious at altitude the more unconsciousness became coma, the longer it would take for a pilot to recover. Time you often don’t have if you are in a dive.
——————–
Notes.
——————–
The design of the critical valve in this mishap is no longer used. There are new designs to prevent this from happening. Also the military has much more training and awareness programs about hypoxia. Recommended procedures were also revised to increase safety. The case of Florida 392 is used to emphasize to pilots the importance of following safety procedure.
Altitude Chamber Hypoxia Training Video
http://www.youtube.com/watch?v=m8ooGY8Jbqw
GLOC Centrifuge Training
http://www.youtube.com/watch?v=v7mrKMn47tc
Tipping the doodlebugs
A few enterprising pilots discovered that they could slide a wing under the wingtip of the “flying blowlamp” and lift it, tipping the flying bomb out of control. That quickly became a standard method of destroying the bombs
http://www.fiddlersgreen.net/AC/aircraft/V1/info/info.php
The pilot that Chuck Yeager saved from hypoxia.
http://en.wikipedia.org/wiki/Joseph_A._Walker
Effects Of Explosive Cabin Decompression On Crew (test dummy) Video
http://www.youtube.com/watch?v=EHGBQINW0B0
Please note my intention is constructive criticism to educate and create awareness for safety. I have no ill will to the deceased pilot or anyone involved.
Other then fighter most aircraft will be break apart in a dive before GLOC will be much of a factor, if a pilot blacks out.
Such as this one almost did.
Deadly day avoided at Cape airport (February 3, 2007)
http://www.semissourian.com/story/1188041.html
I’m really that not familiar with civil aviation, but I would imagine the tanks and the masks are not checked as often as they should be. I really think the oxygen system should be checked before each flight, to make sure there is oxygen in the tank, the regulators working properly, connections and mask have a good seal. I suspect that the pilots don’t check it before each flight, it seemed obvious that they didn’t in this case.
Sign In
February 3, 2007 at 10:51 pm