View Full Version : G-LOC

May 19th 04, 06:15 AM
Hi everyone,

I'm writing about a G-LOC I experienced last Monday 05/17/04 to
inform and prepare other aerobatic pilots.
Last Monday at about 3:15 PM I departed ENW airport in an EXTRA 300L
to the west to practice my sequences for the 2004 intermediate
category,at 4500 ft ( about 3700' AGL ) I leveled off and continued
west toward my practice box,
the first run after the 'acro' checklist went ok except some drifting
north east due to strong winds aloft ( about 25 -30 kts ),
the second run was the same sequence of the 2004 known,this time I
decided to start on the west edge of the box to allow for
drift into the middle, dive to box wing wag and start,after the second
maneuver comes the one turn spin, a dive straight down on the
power and start pull into the half loop ...................
I'm waking up from a sleep ??? everything is white and quiet,I know
something is wrong but can't figure out what,
the only thing I'm thinking now is that I have to take control of the
aircraft before the crash. then comes the engine noise back trough
my ears,and about two seconds later visual cues, fortunately I wake up
still holding the stick,nose high attitude approaching a stall at
about 5000'.
first I'm confused and disoriented recovering the aircraft,and
believed I just fainted,something I never experienced before,
I turn the aircraft immediately to ENW thinking I'm going through some
medical emergency,but then I realize
that I'm up here in the aircraft for a reason and not just flying
trough,and then it hits me, I survived a G-LOC.a G induced
lost of consciousness.
I have been flying aerobatics since 1997, am in perfect health,37 yrs
old,commercial and a CFI, and always try to keep high level of
safety,read books about aerobatics,and not afraid to ask for
instruction and inputs from more experienced pilots.
I did grayout and blackout many times before early enough to ease the
back pressure and recover.the only thing I didn't know before is that
in some cases you enter the G-LOC without any early notice.
In general I'm use to quick pulls of 8 G's sometime 9 G recorded and
about -4.5G's. the problem here is of course the duration of the G
although I can't recall anything from after the spin which is in par
with the US NAVY tests done on subjects concluding amnesia is one of
the symptoms
after a G-LOC, I don't think that pull to the half loop had more than
5 G's in it.
The scary part about that US NAVY study is the claim that it took
pilots about 15 seconds to recover from a G-LOC,in some cases even 30.
After a minute of thoughts, I had the choice of going back to land,or
to continue,as I was trained some years ago as a paratrooper in the
military,after each accident we
immediately got loaded up on a C-130 to skydive again before fear
takes over. you bet the next half loop was at least twice wider.
After talking to a friend,which is an experienced acro and airshow
pilot,few more factors could have contributed to the ordeal ,
Dehydration, Monday was a hot day with only few sips of diet Pepsi.
Food, my first meal of the day took place later after landing.Fatigue,
try being married
with kids get up to work,and later rush trough traffic 45 minutes to
the airport and not being tired. Workout, well after a long break,I'm
back to the gym again,
after all we sometimes get a second chance, three is unheard-of.

Good and safe flying.


Dave Swartz
May 19th 04, 04:40 PM
(Mike) wrote in message >...
> Hi everyone,
> I'm writing about a G-LOC I experienced last Monday 05/17/04 to
> inform and prepare other aerobatic pilots.
> Last Monday at about 3:15 PM I departed ENW airport in an EXTRA 300L
> to the west to practice my sequences for the 2004 intermediate
> category.............................


Figure 3 in this years Intermediate known can easily result in G-LOC
if you do not start preparing for the pull for the looping portion
early enough. Susceptibility to G-LOC is greatly increased when you
experience a period of negative or even zero G's immediately prior to
pulling positive G's.

A perfect example of the effect is to compare a common loop to an
"interrupted loop". If you execute a normal loop where you load say 6
G's at the bottom you will most likely have no tendency for G-LOC. If
you execute the same manuever (using the same speeds and G forces
during all segments of the manuever) but hessitate for 30 seconds at
the top of the loop (while holding speed constant by reducing
power)you could easily experience G-LOC at the bottom of the second
half loop even though you use exactly the same G loading.

Our circulatory systems work well in a 1 G upright world but are not
well designed for aerobatics. The regulation of heart rate and
pressure reponds with a delay of 10's of seconds. If you subject
yourself to zero G or negative G's for several 10's of seconds, you
heart will automatically reduce its ouput. When you move from this
condition to a positive G condition where increased blood pressure is
required to get blood to your brain, the heart will EVENTUALLY be
commanded to increase its output for the new condition.
Unfortuneatly, this is done with a delay of 10's of seconds, leaving
you vulnerable to G-LOC. This is one of those times where you must
physically strain your muscles (neck, abdomen, upper legs) to restrict
blood from leaving your head. Begin the straining a few seconds
before starting the pull to assure that you have maximized your
restriction of blood flowing from your head.

Dave Swartz
Fort Lauderdale, Florida