Post by Don Johnstone Prevalence of G-induced loss of consciousness (G-LOC)in the United
Kingdom Royal Air Force (RAF) was found to be 19.3% in 1987. With the
introduction of the Typhoon, a fourth generation aircraft, the prevalence
of G-LOC has been re-assessed to determine the effectiveness of current G
tolerance training. Method: A survey was sent to 4018 RAF aircrew,
irrespective of their current role. Information was requested on G-LOC,
role and aircraft type, experience, and attitudes toward G-LOC prevention.
Results: Responses were received from 2259 (56.2%) individuals, 882 (39%)
of whom were current fast jet aircrew. At least one episode of G-LOC was
reported by 20.1% of all respondents. In front line aircraft, prevalence
of G-LOC among the 882 fast jet aircrew who responded was 6%. In the whole
group, G-LOC was reported most commonly in aircrew under training (70.9%),
and was most prevalent in training aircraft (77.4% of G-LOC events). At
the time of the G-LOC, 64% of aircrew had less than 100 h total flying
time. G-LOC was reported most frequently between +5 to +5.9 Gz, and
“push-pull” maneuvers were associated with 31.3% of G-LOC events.
G-LOC was reported most frequently between +5 to +5.9 Gz.
Studies have shown that prone positioning has little effect, the only
remedy is a G suit and training, not often found in gliders.
The USAF require F16 pilots to demonstrate an ability to withstand a
maximum of 9 Gz and this can only be achieved through training and the
wearing of a G suit.
I am left wondering how sufficient acceleration could be maintained in a
LS6 to load the aircraft, in controlled flight, to sustain 9 G or indeed
more than 6G, ignoring that the pilot is going to become rapidly
unconsious if it were to be achieved. I am at a loss to understand why
anyone would want to do that anyway.- Hide quoted text -
- Show quoted text -
At the time (many years ago) I was active and current in F-4s, and we
had to undergo centrifuge training to identify G-LOC causes and
prevention. Centrifuge was with a G-suit, and gradually ramped up to
determine relaxed G tolerance, G-tolerance with proper straining
maneuver and G-suit, and time of useful consciousness at 9 Gs while
performing a tracking exercise in the centrifuge (simple video game
type thing). At the time (I was in my late 30s, smoked, partied, NOT
a marathon runner!), I could function at 4 to 5 Gs relaxed, 6 Gs with
simple straining, and 20 - 30 seconds at 9 Gs with everything working
(tight G-suit, straining, breathing, etc). 9 Gs is rough, and the
penalty of any relaxation was immediate GLOC (fun to watch the "fit"
skinny non-smoking runners pass out at 8 Gs!).
I'm surprised about the comment that position had little effect - that
goes counter to my experience and to the physiology of G-effects on
the human body. Bloody boffins, probably asked the wrong questions...
The thing about G-LOC is that it is not so much a matter of the peak G
load, but is more a function of the rate of onset of the Gs. If you
are expecting the Gs, then you can prepare; but a snatch pull to 5 Gs
when not expecting it (which happened frequently when you were in the
back seat of an F-4, for example, looking in the radar or checking 6)
could definitely put you in a world of hurts!
But Gs is like any physical activity - you have to do it a lot to
maintain your acclimitization. I enjoy acro up to 3-4 gs nowadays,
but would not like to try 5 sustained anymore! Fortunately, glider
acro is not only low peak but also short sustained Gs.
My LS6 has a pretty small elevator but at redline is real sensitive in
pitch, I think the instantaneous G that could be generated with a hard
pull would not be good for the airframe, to say the least! And it's
the instantaneous G that is what is going to break the wings, not the
sustained G (which is always going to be low in a glider).
Cheers,
Kirk