S-H safety harness (V2C)

Ray,

I know (hope) your statement was tongue-in-cheek, but it is worth a
comment. Your "spare tire" (or even your six-pack abs) won't prevent
you from submarining. Your lap belts must be and stay securely
locked down on your pelvis. I have an article from one of the auto
racing labs which shows that your pelvis can withstand 5,000 lbs of
force whereas the soft organs of your gut will be severely compromised
at less than 800. Assuming in a crash that the straps around your
middle take 50% of the load (obviously, that will depend on many
factors - crash angle, deceleration mode, etc. etc.), that still means
that anything approaching an 8g deceleration (maybe less) will be
serious trouble. Now, that's an otherwise survivable crash, so it
would be a shame to have a problem. Especially in the older,
flatter seat pans, it doesn't take an especially creative mind to
visualize the submarining that happens without a properly secured lap
belt.

Erik Mann
LS8-18 (P3)

Erik,

It was, although "butt in sling" or something similar might better
"fit" the situation. The whole point of that 5th strap is to keep the
lap belts properly positioned on the pelvis and still allow the
shoulder belts to be tight. This positioning gives the best control of
both vertical and horizontal motion. In the case of a really high g
impact in a glider I suspect restraint issues would be moot, however.

There's been a lot of research on making high speed racecar crashes
survivable; there's both interest and funding for it, very little on GA
and only a bit in gliders. The key lessons from Nascar and Grand Prix
racing are that a cockpit that maintains its integrety and a restraint
system that keeps the driver within that container are good things.
Nascar has now mandated a separate head restraint to prevent neck
injuries. These measures have made at least some 200 mph crashes
survivable.

Bringing measures of this kind to gliders would require that we be
willing to pay for them, something, according to the DG newsletter, we,
as a group, are not willing to do.

Ray Warshaw
1LK

Properly positioned lap belts control both vertical and horizontal
motion. The shoulder belts keep the torso from pivoting forward and
the crotch strap keeps the lap belts in place. Note that the crotch
strap need not actually contact your crotch to properly perform this
function. My recollection of the racecar research is that, in a
reclined seating position, a substantial portion of the force on the
shoulder belts is transfered downward and captured by the lap belts.

Ray Warshaw

I'm going to give this 5th point thing (crotch strap) a try but I'll
have to have the anchor point on the seat pan just below the stick boot
around where the factory relief tub hole is drilled. (I made a new hole
for that several inches farther aft.)

Thanks to everyone who responded by e-mail, I appreciate it very much.

~ted/2NO

Go to groups.google.com and do a search for the "Glider harnesses, 4
versus 5-point" thread back in 1998. There is some specific information
about the pros/cons of various types of safety harnesses and how to
modify existing gliders.

Chip Bearden
ASW 24 "JB"

wrote:
I had a 5th attachment point installed in my ship and it was a
considerable improvement over the 4 point original equipment harness.
The crotch strap holds the lap belts in the proper position vertically
such that, once they're tight, I don't move up or forward at all; very
nice!.

I agree absolutely with the above.

For peeing in the air you just temporaraily loosen or disconnect the
crotch strap, I find no problem in this in my Nimbus. But remember to
re-connect and tighten it again! Not too tight, though, on a long
flight, comfort is a positive flight safety factor, discomfort is the
opposite. But tighten all straps before landing!

Correctly-positioned lap-straps take the main load in an ground-impact
situation, shoulder straps prevent the body from "jack-knifing" and the
fifth (crotch) strap keeps the lap straps from riding up the body
during flight. If the latter happens, in a situation of high
longitudinal deceleration, the body "submarines" under the lap strap
and high damage or worse can be done to the lower limbs or torso.

In my opinion, all glider seats should have a five- (or six-) point
harness for the above reasons. Even more important in gliders with
reclining or semi-reclining seats.

There was much discussion on this a few years ago on this newsgroup. A
report by a German Automotive engineer criticised the glider crotch
strap for the alleged possibility of damage to the testicles in an
impact. German manufacturers and others "took fright" and then refused
to fit five-point harnesses. This position has fortunately now been
reversed as a result of subsequent tests and reports by aviation
experts.

I and others such as Doctors Peter Saundby and Tony Segal in the UK
became involved. As an ex military pilot used to riding on ejection
seats with 5-point harnesses, I always thought that in a glider
life-or-death impact, sore balls for a few days (if indeed that
happened, which is questionable) were a better alternative to becoming
a paraplegic or dead. Dr Saundby, an experienced glider pilot and
military pilot and flight surgeon and the BGA Medical Advisor, pointed
out that the crotch strap was there, not so much to take load, but to
hold the load-bearing thigh straps in their correct position before
impact.

Dr Segal was able to carry out glider cockpit drop-tests in
co-operation with a number of other organisations such as the UK
Ministry of Defence R&D agency (now QintetiQ). These used old cockpits
and instrumented mannikins. The results were very much in favour of
having that crotch strap, for the reasons above. The Segal tests were
reported in UK magazine Sailplane and Gliding and a longer official
report was also published. Someone may be able to dig up the
references.

So, anyone with a reclining seat glider and only a four-point harness,
I would seriously consider carrying out an officially-approved mod to
fit that crotch strap!

Ian Strachan
Lasham Gliding Centre, UK

Ian and others across The Pond,

I'd very much be interested in seeing the reports mentioned. Heck, I'd
even be willing to pay for a copy (a novel idea I know). If anyone is
willing to take this on, please contact me directly.

Erik Mann
LS8-18 (dedicated "6-pointer")

I wandered around the web sites for Schroft, Gadringer, Davis and
Pacific Scientific today. For aircraft, they only appear to offer 3, 4
or 5 point harnesses. None of them offered 6 point harnesses for
aircraft. Schroft does indeed make 6 point harnesses, but these
harnesses are intended for motor racing and only carry FAI
certification, not LBA or FAA certification.

Wouldn't it be a violation (in the USA) of some FAR to fly a type
certificated aircraft with a safety harness that didn't carry either
FAA or LBA certification?

-John

TTaylor at cc.usu.edu wrote:
I think if you purchase most of the Schroth belts made with the fifth
point space you can convert it to six point without being concerned
about violating the FAI certification for a standard airworthiness
aircraft. The main part of the belt will carry the correct id. I
would do it that way if I was worried about airworthiness certificates.
In the experimental category you have a little more latitude to use
the FAI approved belts.

I have been reading this thread with interest.

I (part) own a Nimbus 2c and have experienced problems with the very
high attachment point of the shoulder straps resulting in smashing the
canopy with my head!

(See http://www.hart.wattle.id.au/alice/a...ce27jul02.html for
the details and photos)

Whilst a 5 (or 6) point harness will stop 'submarining' under the lap
strap (which hasn't appeared to be a problem) it does nothing for the
problem caused by having the attachment point of the harness so high (at
the shoulder level and only just behind the shoulder at that.

This position means that even with the straps cinched up tight, my upper
body can still lift considerably when I hit turbulence. In order to
avoid hitting the canopy hard, I must use a very prone seating position.

If anyone with a Nimbus 2 has found a way of overcoming the poor design
of the strap attachment points, I'd love to hear. We have searched for a
better solution in vain!

--
Robert Hart
+61 (0)438 385 533 http://www.hart.wattle.id.au

Robert,

Read my first note above, 6 point completely fixed the problem.
Shoulder harness is only to stop the upper body going forward, lap
belts hold you down. Once I put a 6 point in my Nimbus 2 I never
touched the canopy again. I fly some of the most rugged ridge in the
world and if it will work here it will work in any environment. I used
a Schroth system that was very easy to design the modification. I like
the Profi II-6 HANS FAI system. It can be adapted to gliders very
easily. It will be the first modification I will make to my Ventus B
this year.

Tim
Logan, UT, USA
Ventus B