Forum: General F-16 forum

outlaw162 wrote:

The board used this terminology, “almost” loss of consciousness (no acronym), uniquely for the F-22 accident. It was used primarily to explain the subsequent loss of situational awareness. I don’t believe it had been used formally prior to this for the “tunnel vision effect” or gray/black out while still conscious. You’re either conscious or you’re not. This is like “almost” pregnant.

Medically, ALOC is Acute Loss of Consciousness, of which GLOC is a subset.

ALOC, curiously, is also Acceptable Level of Competence.

OL

A-LOC, meaning "Almost Loss of Consciousness," is not a new term nor uniquely attributed to the F-22 accident. Here is a link explaining it further:
<a href="http://www.datafusionlab.org/publications/papers/shender2002_almost_loss_of_consc_125.pdf" target="_blank">http://www.datafusionlab.org/publications/papers/shender2002_almost_loss_of_consc_125.pdf</a>

Also I'd have to disagree with your binary assessment of consciousness. That's like saying you're either drunk or you're not. If you've never been a little buzzed, I suggest you take it a little slower on the Jeremiah Weed. Cheers,

uncleslashy

F-16.net Sponsor

I stand corrected.

Very interesting study. I need a little time and a little Weed to digest it all.

OL

So wait...I was right? >.>

Uncleslasher:

A couple of observations and comments concerning the study…

9 subjects is a very small sample group. We do a lot of human-in-the-loop testing and would probably never use a sample size that limited to draw conclusions from. And the psychophysiology orientation of the study certainly does not lend itself to a Monte-Carlo analysis. This study might be used to warrant further investigation however.

I could not find a table listing the subject’s aviation background and experience. With the relative oxygen level monitoring that was done (as a dimensionless quantity), there was some question in my mind whether initial apprehension & possible subsequent hyperventilation might have influenced additively the resulting levels even before the actual G pulses and subsequent “syndrome” symptoms.

We’re these aviators or non-flying volunteers who might more likely be intimidated by a centrifuge (not that some aviators aren’t also)? The first line of the report uses the term aircrew and later NAVAIR volunteers, but nowhere substantiates that the nine subjects actually were aviators. It almost goes out of its way to avoid that statement.

The one female seemed to demonstrate more G tolerance than any of the males but there are no correlations ventured as to which “syndrome” symptoms were more or less prevalent with more or less tolerance. Once again, a small sample, especially since there was a lot of subjective input also.

One thing that is clear is that the acronym A-LOC has been around at least since 2002-2003. I was wrong about that & Kori has obviously done some reading. But it almost seems that this study and the F-22 accident “found” each other. I can’t find anything else anywhere referencing this. (Not that there isn’t.)

The one statement: “The primary manifestation of ALOC symptoms was a disconnection between the desire to do something and the actual ability to act upon it” is certainly occasionally true of most of us 60 year olds as well.

OL

(BTW you drink Jeremiah Weed fast because you don’t want to taste it.)

OL,

I think I caught the reference from 'Great Planed' or my ROTC class, to be honest, I don't quite remember.

OL,

The main reason for linking the study was in the introduction where it defines ALOC as "deficits in motor and cognitive function" as a result of stress that is insufficient to cause GLOC. It also notes that ALOC has been identified in centrifuge studies since the early 1980s. The purpose of the study was to try defining the cognitive and motor deficits; whether the sample size was large enough or methodology sufficiently vetted I'll leave to smarter men than myself.

GLOC and ALOC are difficult to identify for certain in CFIT cases. However, one significant difference between the two is that full GLOC results in loss of all motor function; the pilot loses the ability to make flight control inputs aside from incidental contact with the controls. In ALOC, vision is nearly gone or completely gone, but more importantly some motor function is available. Pilots (or centrifuge subjects) may be aware their vision and/or cognitive ability is going away, and that they need to do something about it, but due to mental confusion they cannot tell their hand to relax the pull. The body is still listening to its earlier commands, but the brain has lost most of its control. So a hint in CFIT cases that ALOC rather than GLOC has occurred can be continued flight control manipulation without efforts to avoid terra firma. I think of it as a TKO vs a KO in boxing or MMA.

What is not clear is how often ALOC occurs since its definition is subjective. It begins and ends somewhere between full consciousness and complete unconsciousness, and effects are different for different people. I can guess that it occurs more often than GLOC, and that it is more easily recovered, but I have zero data to back that up. Any Flight Physiologists out there care to weigh in on the subject? Or safety dudes? Is ALOC a reportable safety incident?

uncleslashy

I think I'm in ALOC most of the time.
fisk

I was a safety dude for many years and as I posted earlier, I've never heard of the A-LOC terminology. To the best of my knowledge that acronym is not used in USAF flight safety documents. Reportable events include physiological events as stated below in AFI 91-204 (Safety Investigations and Reports):

"Physiological Events. Report episodes of abnormal physical, mental or behavioral conditions or symptoms. See AFMAN 91-22X for specifics."

The Human Factors Analysis and Classification attachment to AFI 91-204 contains the following:

"Adverse Physiological States are factors when an individual experiences a physiologic event that compromises human performance and this decreases performance and results in an unsafe situation.

PC301 Effects of G Forces (G-LOC, etc)
Effects of G Forces (G-LOC, etc) is a factor when the individual experiences G-induced loss of consciousness (GLOC), greyout, blackout or other neurocirculatory affects of sustained acceleration forces."

Note that G-LOC is defined but A-LOC is not.

AFI 91-223 (Aviation Safety Investigations and Reports) lists the following specific reportable events:

"1.3.1.1. Physiological Events. Report episodes of abnormal physical, mental, or behavioral conditions or symptoms which occur during or after flight. ... The following events must be reported:
1.3.1.1.1. Aircrew or passenger decompression sickness from evolved gas (bends, chokes,
skin, neurological, or neurocirculatory manifestations).
1.3.1.1.2. Aircrew loss of consciousness or incapacitation in-flight.
1.3.1.1.3. Aircrew hypoxic (altitude) hypoxia (suspected, probable, or definite).
1.3.1.1.4. Aircrew trapped gas disorders (ear, sinus, teeth, or abdominal).
1.3.1.1.5. Aircrew or passenger symptoms or health effects caused by toxic, noxious, or irritating
materials such as smoke, fumes (including carbon monoxide) or liquids.
1.3.1.1.6. Aircrew G-induced loss of consciousness.
1.3.1.1.7. Aircrew spatial disorientation of any type (including visual illusion) resulting in an unusual aircraft attitude.
1.3.1.1.8. Any medical condition, event or physical injury directly resulting from performance of flight activities that an aeromedical professional determines is significant to the health of the aircrew.
1.3.1.1.9. Aircrew degraded operational capabilities or retinal damage caused by military or commercial lasers."

Looks like "other neurocirculatory affects of sustained acceleration forces" aren't reportable unless loss of consciousness or incapacitation occurs. However, safety officers have the option to report any hazardous occurrence that has a high potential for becoming a mishap as a High Accident Potential event.

Just one last input and a couple of things about this whole ALOC “syndrome” concept as defined (not to dispute it as a concept)…

Flying T-37’s two and sometimes three flights a day for four years involved a lot of days of multiple contact flights. On each of these flights, most of the syllabus acro requirements (loop, split S, Cuban 8, cloverleaf, Immelmann, etc.) as well as “high speed” dive recoveries were performed. Depending on student ability or lack of, sometimes over and over. No G-suit was worn in the T-37.

Even though the G levels were lower, very often during each of these maneuvers, especially just riding while the student commanded the G’s, I experienced temporary tunnel vision and loss of vision to varying degrees, but never loss of consciousness, nor did any student. This vision impairment could occur four or five times or more on a single flight, flight after flight, day after day. I truly don’t recall ever experiencing any of the symptoms of the ALOC “syndrome” nor did I notice them in a student, i.e., and I quote:

“Physical symptoms included tingling, twitching, uncontrollable hand movements, hearing loss and transient paralysis. Cognitive deficits included confusion, amnesia, delayed recovery, a “vacant feeling” and difficulty in forming words. Surprise, concern and pleasant feelings were some of the emotional signs.”

Nor did any other instructor ever make reference to this. Students were more likely to hyperventilate toward degraded consciousness than to “G” themselves that way.

This whole “syndrome” concept just doesn’t ring true for me. If there was a “syndrome” associated with this type of repeated G loading, it was “sore-neck” syndrome at the end of the day. Take it for what it’s worth. Other pilots may disagree. Anyway…

Situation: Auto-GCAS equipped aircraft pilot “ALOC”’s. Pilot’s hand remains on the stick making cognitively impaired inputs that could, but would not necessarily recover the aircraft unless continued.

Could this cause the GCAS 1.5 second timer to reset initially and then be restarted at a point where an additional 1.5 seconds would place the aircraft in an unrecoverable position using a GCAS programmed 5G pullout?

OL

(I grayed out a lot more in the T-37 than I ever did in the centrifuge or F-16 at higher G)

Red out was described to me as the result of large negative g causing one's lower eyelid to move up over the iris, thus blocking vision and appearing red from the inside of the eyelid. There are no muscles to pull the lower lid down, so it rides up freely under the effect of negative g.

A-Loc is necessary while using the straining maneuver that helps to prevent G-Loc...

otherwise you may wind up with a soiled flight suit. Embarassed

Just one more last input...

I always thought it was the busted capillaries in the eyeballs from prolonged excess (2-3) negative G and the fact that your eyes looked red to someone else (or to you in a mirror) that resulted in the term “redout”.

Under negative G, the once oxygenated blood that entered the brain becomes deoxygenated blood in the brain and some or most is trapped by the foot to head force and can’t be returned to the heart through the veins and can't be replaced by new oxygenated blood. This can eventually result in blackout or unconsciousness just like insufficient flow to the brain under positive G. But the deoxygenated blood trapped in the brain under pressure can also in rare cases cause a stroke.

In any case negative G’s make me nauseous.

Take two aspirin and call me in the morning.

OL

i guess so if u down a hill and then back up one really quickly- but the activities that i meant earlier are like after sprinting for an extended period of time and i guess getting off the couch quickly, but that is not really all that rigorous

Salute!

I go with exfltsafety-dude and OL.

Whatever happened to "grey out", "black out", etc?

Pull a bit harder than you're ready for and you "grey out" when O2 to eyes dimishes. Brain still working fine. Pull even harder and you can't see at all! Can hear and function a bit, but not completely in "la-la" land like the guys in the Viper that showed us no sierra "g-loc" in those early years. Was in back seat on one of those, and it was maybe the third or fourth one we witnessed.

G-suits help keep blood from pooling down in your lower extremities, so you don't have to grunt and groan and clench as much, but they still have their limits. In the Viper we learned to clench upper body muscles and neck muscles to actually "pump" blood up to the eyes and brain. So after a year or two we had student studly giving we dinosaurs in the back seat a really tough time, heh heh. We also pre-inflated our gee suits using the test button just before the merge.

later,

Gums sends...

A friend of mine just passed on this testimony from a recent close call he had. I would categorize his situation as ALOC in lieu of a better term to capture that he was still awake but the body was not responding.

On the last set-up I went for the "no switch" option, which basically corresponds to a 9000' BFM set-up and turn circle entry. I started the turn easy on the Gs, 3-4Gs for about 5 seconds, and then I increased the Gs and went up to 8.7Gs. My AGSM is audible on the tapes, with a good interval between breaths. I got my usual "you're above 7.5Gs" ques which include colours fading and some bright spots in my eyes, so I decided to ease off the Gs. The fact is that when I did there were about 5 seconds in which the jet is just flying straight and even though I can see the other jet in front of me still turning and I can feel the stick in my hand (so to speak), my brain is telling my hand to roll wings level and pull up nothing is happening. It was some scary sh*t.

Forum: General F-16 forum

A-lock vs g-lock