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