(Mike) wrote in message . com...
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.............................


Mike,

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