Crouch Strap story

I sent the following to our magazine nine months ago and didn't receive an
acknowledgement or receipt. I guess it was not suitable for them so I
thought I would share it with ras to maybe provoke some safety discussion.

efb10-11-03-rev.6-5-04

You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on this.
The role of the crotch strap is significant and worthy of mention.

The last half dozen gliders I've had I added a crotch strap (usually
available from Wings & Wheels), which easily clicks into the bottom, front
or 5th slot of the standard Gadringer belt hardware. I secure the other end,
which terminates with the belt into a triangular link, with a quarter inch
hole that I bolt to the seat pan with a large "wood" washer behind the seat
pan. My gliders are Experimental category so this is legal.

I always heard that the main purpose of a crotch strap was to keep the lap
belt across the upper thighs and prevent it sliding up to the stomach area.
I have since learned better.

It of course depends on the direction of the accident loads and the
direction of the inertia of the body as to how all restraint straps come
into play.

Many glider accidents involve "dropping in" vertically wherein the tailbone
(in the L-1, L-2 area) or higher are damaged so the belts don't help much.
You seldom see accidents with lap belt overload, but it happens. I have a
sad memory of helping remove a dead friend from an inverted Ventus cockpit
where the lap belts on both sides had pulled lose from the seat pan.
Fortunately rare but it happens.

In my "incident" the nose of the glider hit hard ground at about a 60 plus
degree angle. The "load" was about along the longitudinal axis of the
glider. Since in our modern gliders (ASW-28 in my case) we recline (sit
supine), the inertia of my body was toward the nose with only the crotch
strap to resist. Actually Waibel designed the seat pan to take some of this
forward load against the bottom of the thighs. In this seating the knees are
bent more upward.

The nose of the glider (along with my feet) was crushed in a calculated
energy-absorbing manner. Thank you Gerhardt Waibel! I think his design and
the crotch strap saved my knees.

I was conscious and lucid until the helicopter dropped me off at the
Medical College of Georgia Trauma Center.

After that I really was not with it for a couple of weeks, but after that
time I suddenly noticed that my groin area was still quite swollen. I
realized that my crotch area had sustained a significant load and that all
things considered had kept my body from moving more forward and no doubt
helped minimize the leg/knee damage. I had no shoulder strap or lap belt
marks or soreness.

Since my guess is that a significant number of glider accidents impose loads
and body reactions similar to mine, I recommend a crotch strap. Trying to
distribute the load to the pelvic area by wearing an athletic "cup" may be
good for some flights, but for some flights there are other disadvantages.
Many contest pilots regularly wear a male external catheter and I don't
think both would work. With just the crotch strap I always had to be
careful that the strap was adjusted somewhat to the right, was not too
tight, and did not interfere with the flow from the catheter that was to the
left.

I suggest reading Chip Bearden's posting which appeared in the
rec.aviation.soaring newsgroup on Nov.20 1998 which outlines a more complex
but better seat belt design.

I hope this discussion will create more thought about glider accident
safety.

Ed Byars

You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on this.
The role of the crotch strap is significant and worthy of mention.

Dr. Byars, thank you for this interesting and important feedback based on real
world experience.

The standard line from the German manufactures is that a crotch strap is not
needed because the submarining hazard has been taken care of through use of the
"H point" when locating the anchoring point of the lap belts. This system
locates the lap belt a bit further forward than in older designs with the aim
being to get the lap belt lower on your hips. This is supposed to prevent it
from being pulled out of place when tightening the shoulder harness. It does,
but I believe the lap belt has to be tightened to an un-necessary degree to get
anywhere near the effect the "H point" is credited with bringing about.

My experience is that the "H point" is not adequate to keep the lap belt from
being pulled up when tightening the shoulder straps. This is especially true
when flying out west in strong lift at high speed. A crotch strap helps keep
you from bouncing around thus providing more comfort and better control. The
difference is security in the cockpit is dramatic. I normally retro fit a
crotch strap to my gliders and feel a lot safer and more comfortable with its
use. This holds true even with my Genesis which used the "H point" system to
locate the lap belt anchor points.

Robert Mudd

"Robertmudd1u" wrote in message
...
You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on
this.
The role of the crotch strap is significant and worthy of mention.

Dr. Byars, thank you for this interesting and important feedback based on
real
world experience.

The standard line from the German manufactures is that a crotch strap is
not
needed because the submarining hazard has been taken care of through use
of the
"H point" when locating the anchoring point of the lap belts. This system
locates the lap belt a bit further forward than in older designs with the
aim
being to get the lap belt lower on your hips. This is supposed to prevent
it
from being pulled out of place when tightening the shoulder harness. It
does,
but I believe the lap belt has to be tightened to an un-necessary degree
to get
anywhere near the effect the "H point" is credited with bringing about.

My experience is that the "H point" is not adequate to keep the lap belt
from
being pulled up when tightening the shoulder straps. This is especially
true
when flying out west in strong lift at high speed. A crotch strap helps
keep
you from bouncing around thus providing more comfort and better control.
The
difference is security in the cockpit is dramatic. I normally retro fit a
crotch strap to my gliders and feel a lot safer and more comfortable with
its
use. This holds true even with my Genesis which used the "H point" system
to
locate the lap belt anchor points.

Robert Mudd


After reading Ed and Robert's posts, I intend to install a crotch strap in
my Nimbus. At the very least, it will let me get the shoulder straps REALLY
tight without pulling the lap belt up too high.

When you are riding 10 - 15 knot mountain thermals with a stiff carbon wing
you just can't be strapped in too tight.

Bill Daniels

"Robertmudd1u" wrote in message
...
You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on
this.
The role of the crotch strap is significant and worthy of mention.

Dr. Byars, thank you for this interesting and important feedback based on
real
world experience.

The standard line from the German manufactures is that a crotch strap is
not
needed because the submarining hazard has been taken care of through use
of the
"H point" when locating the anchoring point of the lap belts. This system
locates the lap belt a bit further forward than in older designs with the
aim
being to get the lap belt lower on your hips. This is supposed to prevent
it
from being pulled out of place when tightening the shoulder harness. It
does,
but I believe the lap belt has to be tightened to an un-necessary degree
to get
anywhere near the effect the "H point" is credited with bringing about.

My experience is that the "H point" is not adequate to keep the lap belt
from
being pulled up when tightening the shoulder straps. This is especially
true
when flying out west in strong lift at high speed. A crotch strap helps
keep
you from bouncing around thus providing more comfort and better control.
The
difference is security in the cockpit is dramatic. I normally retro fit a
crotch strap to my gliders and feel a lot safer and more comfortable with
its
use. This holds true even with my Genesis which used the "H point" system
to
locate the lap belt anchor points.

Robert Mudd


After reading Ed and Robert's posts, I intend to install a crotch strap in
my Nimbus. At the very least, it will let me get the shoulder straps REALLY
tight without pulling the lap belt up too high.

When you are riding 10 - 15 knot mountain thermals with a stiff carbon wing
you just can't be strapped in too tight.

Bill Daniels

In article , Robertmudd1u
writes
You may be interested in my latest crotch strap experience.

I'm still analyzing my June 2003 accident and the cause. More later on this.
The role of the crotch strap is significant and worthy of mention.

Dr. Byars, thank you for this interesting and important feedback based on real
world experience.

The standard line from the German manufactures is that a crotch strap is not
needed because the submarining hazard has been taken care of through use of the
"H point" when locating the anchoring point of the lap belts.

This system
locates the lap belt a bit further forward than in older designs with the aim
being to get the lap belt lower on your hips. This is supposed to prevent it
from being pulled out of place when tightening the shoulder harness. It does,
but I believe the lap belt has to be tightened to an un-necessary degree to get
anywhere near the effect the "H point" is credited with bringing about.

Quite. If you could predict exactly when you were going to crash, and
correctly tighten up your straps beforehand, this might work. But with
sometimes hurried field landing decisions the "pre-prepared crash
scenario" is just not realistic. Also, from other postings in this
thread, the four point harness does not seem to be very good in high
turbulence.

My experience is that the "H point" is not adequate to keep the lap belt from
being pulled up when tightening the shoulder straps. This is especially true
when flying out west in strong lift at high speed. A crotch strap helps keep
you from bouncing around thus providing more comfort and better control. The
difference is security in the cockpit is dramatic. I normally retro fit a
crotch strap to my gliders and feel a lot safer and more comfortable with its
use. This holds true even with my Genesis which used the "H point" system to
locate the lap belt anchor points.

Robert, I entirely agree with you and Ed Byars that a fifth (crotch, if
you like) strap is invaluable in a number of situations.

In my military flying, a five-point harness was normal and I spent many
hours wearing one, normally as part of Martin Baker ejection seats of
various types.

Turning to gliding, some 10 years ago another pilot at Lasham ordered a
German glider and wanted 5-point harnesses fitted during build. The
maker refused to fit them "because it has been shown that the fifth
strap is dangerous". When pressed, they quoted a report done by a car
(automobile) test organisation in Germany on five-point harnesses that
suggested that some damage might occur to the crotch area in the case of
a severe impact. Possible damage to the male genitals was also
mentioned, and this seems to have had a major impact (no pun intended!)
on people's thoughts about the fifth strap.

However, my view was that in a major crash, if the fifth strap caused
some soreness afterwards but prevented "submarining" of the body under
the lap straps, then it could reduce damage to the legs or even save the
life of the pilot. It is all very well raising emotional points about
sore genitals. The real point IMHO is in a crash in which life is at
stake or there is the possibility of the pilot becoming a paraplegic.
What is the best option to minimise these awful results in a critical
"life-or-death" crash situation?

To put it crudely, would you rather have a sore crutch for a short
while, or be dead, or in a wheelchair for the rest of your life? In any
case, the "sore crutch" effect may not be there after all, see the next
para.

I was supported in my view by Dr Peter Saundby, the medical advisor to
the BGA, a qualified flight surgeon and an RAF jet pilot himself. He
pointed out that an important function of the fifth strap was to keep
the major load-bearing lap straps from riding up too high, even if they
had slackened off during flight. The lap straps then stood a good
chance of taking the large crash loads for which they are designed, and
any tendency to "submarine" under them would be minimised.

Peter and I were able to interest Dr Tony Segal, a UK glider pilot and
graduate of the UK Aero Medical (Flight Surgeon) course with the RAF at
Farnborough. Tony had already made glider crash tests using redundant
cockpit sections. He then managed to interest the UK Defence Evaluation
and Research Agency (DERA) in the crashworthiness of four and five point
harnesses. Tests were carried out at the UK Defence site at Farnborough
using instrumented human dummies seated in mock-ups of glider cockpits
and the impact test track of the Centre for Human Sciences (CHS) at
Farnborough. The glider cockpit was modelled around a Nimbus 3.

An unclassified report was published. This was also presented to the
gliding scientific organisation OSTIV during their meeting at Bayreuth,
Germany, in August 1999 and no doubt will be available in full from
OSTIV (OSTIV = Organisation Scientifique et Technique Internationale de
Vol a Voile).

As far as I know, this paper is probably the most definitive recent work
on the subject and would probably answer most of the points raised in
this thread. Here are some details:

Title:

Four and Five Point Glider Seat Harnesses - Static and Dynamic Tests

Authors

Dr Anthony M Segal, Lasham Gliding Society, UK
Leslie P Neil, Senior Engineer Impact Protection, UK DERA
Graham A Reece, Instrumentation Engineer, UK DERA
Philip G Murtha, Impact Test Track Engineer, UK DERA

The paper is 20 pages long but para 5b is worth quoting in full (QRF =
Quick Release Fastening, that is, the harness release box)::

"5 b) Observations After the Impact Test

When a 5 point harness was being tested, both with the harness tight and
with the harness slack, the lap straps remained in the correct position
over the hip bones. The QRF also stayed in the correct position.

When a 4 point harness was being tested, both with the harness tight and
with the harness lose, the lap straps were seen to have moved up over
the abdomen until they were jammed tightly under the lower rib margin.
The QRF had moved upwards until it was in the epigastrium (the "pit of
the stomach"). This is very serious, because severe, even fatal injury
may be caused to the internal organs in the upper abdomen.

THIS IS CONSIDERED TO BE THE MOST IMPORTANT FINDING OF THE ENTIRE TEST.

Following the impact test, with a 4 point harness, the shoulder straps
were seen to be hanging loosely between the seat back and the pilot
dummy's shoulders. This was due to the upward movement of the lap straps
and the QRF."

Finally, the conclusion includes the following words:

"A 5-point harness is superior to a 4-point harness in an accident
impact situation and also under conditions of negative-g. This is
especially so if the harness is slack."

It also goes on to say: "It is recommended that the 5th strap be
designed to avoid injury to the crotch of the pilot. This design of
strap should be fitted to new gliders and be retro-fitted (where
structurally feasible) to gliders in current use".

-------------------------------

The above seems pretty conclusive to me and in my syndicate glider we
had a fifth (crotch) strap fitted in the rear cockpit. We were told
that in the front cockpit there was not a proper hard point to which a
fifth strap could be fixed. Maybe with some minor structural
strengthening it could be, this thread has reminded me that we ought to
investigate it.

--
Ian Strachan
Lasham Gliding Centre, UK

In article ,
says...

Finally, the conclusion includes the following words:

"A 5-point harness is superior to a 4-point harness in an accident
impact situation and also under conditions of negative-g. This is
especially so if the harness is slack."

It also goes on to say: "It is recommended that the 5th strap be
designed to avoid injury to the crotch of the pilot. This design of
strap should be fitted to new gliders and be retro-fitted (where
structurally feasible) to gliders in current use".

-------------------------------

The above seems pretty conclusive to me and in my syndicate glider we
had a fifth (crotch) strap fitted in the rear cockpit. We were told
that in the front cockpit there was not a proper hard point to which a
fifth strap could be fixed. Maybe with some minor structural
strengthening it could be, this thread has reminded me that we ought to
investigate it.

Tony Segal published a later article, which concluded six point
harnesses were superior to five point harnesses. It was published in
S&G, but I'm not were I can look at the article for the date.

--
-------
Eric Greenwell USA

Tony Segal published a later article, which concluded six point
harnesses were superior to five point harnesses.

I'll bet they are but does this not provide two more straps to un-fasten when
the need for a quick egress arises? Or am I missing something?

Robert Mudd

It is possible to make a 6 point harness that simply falls away when
released. Some were trialled in Europe and the UK I believe . The plusses
for a six point harness outweighed the negatives by a long way! I was trying
to get hold of one but they appear to not have been able to get them
certified.
It is very difficult to innovate in the aviation industry without spending
vast amounts of money and I think this vital innovation may have fallen foul
of this.

Perhaps DG offers this as an option? They seem to be the only real
innovaters left on the soaring scene.

Ian


"Robertmudd1u" wrote in message
...
Tony Segal published a later article, which concluded six point
harnesses were superior to five point harnesses.

I'll bet they are but does this not provide two more straps to un-fasten
when
the need for a quick egress arises? Or am I missing something?

Robert Mudd

"Robertmudd1u" wrote in message
...
Tony Segal published a later article, which concluded six point
harnesses were superior to five point harnesses.

I'll bet they are but does this not provide two more straps to un-fasten
when
the need for a quick egress arises? Or am I missing something?

Robert Mudd

Hi Robert....
All the belts on my SCHROTH harness disconnect when the release is
punched on the buckle/latch. The operating mechanism's are very user
friendly and are meant to be operated by excited people wearing gloves
who are probably on fire. I wouldn't be worried in the least about the
possibility
of entanglements. All connections happen at the buckle/latch, one place to
hookup
and/or release. ABSOLUTELY BULLETPROOF and completely reliable. If I were
to hazard a guess, I'd bet that the motorsport standards exceed the TSO for
aircraft
belts by a very wide margin.
Scott Correa

Further to my posting yesterday I have identified the
6 point harness in our Std Cirrus as as Luke PRO6F
designed for single seat race cars.

See:

http://www.lukeracing.co.uk/rec.php?cat=17

Flying with it today was the most comfortable I have
ever been in a glider as I felt totally secured with
the lap strap held low and no tendency to slide forward
in the seat pan with the lap strap rising as happens
in so many gliders. Even a deep seat pan like the
front seat of a Duo comes nowhere near in terms to
achieving that feeling.

It may be non approved but I really don't care as the
benefits for comfort and safety are so clear cut.

John Galloway