Do your straps up tightly for winch launches!

[Derek Copeland]

The UK Air Accident Investigation Branch (AAIB) has
recently published a report on a fatal accident involving
a DG600 sailplane back in 2005.

The circumstances were that the DG600 took a winch
launch, and rotated into an unusually steep climb after
lift off. This was enough to slow down a slightly underpowered
winch to the extent that the glider stalled and flicked
into a spin. The pilot was killed in the ensuing crash.

The experienced pilot was the owner of the DG600 and
maintained it himself as a BGA inspector. It was assessed
from the wreckage that the glider was correctly rigged
and that all the controls were properly connected.
The only anomaly found was that the ASI static was
connected to the Total Energy probe, which might have
caused the ASI to misread. However tests showed that
this would only cause minor errors.

The shoulder straps were found to be somewhat loose
although, as the glider crashed inverted, this may
have been as a result of the crash. It was concluded
that the most likely cause of this accident was that
the pilot had not sufficiently tightened his shoulder
straps and had slid backwards up the seat, which caused
him to inadvertently pull back on the stick in the
process.

I should point out that I had a somewhat similar experience
when I took my first winch launch in a DG101 sailplane,
and was only just about able to retain control with
my fingertips at full stretch. My feet where well off
the rudder pedals! DG single seaters have a very reclined
seat position and the shoulder straps seem to be mounted
a bit too far up.

Can I recommend most strongly that you do your straps
up really tightly and set the rudder pedals at least
a couple of notches nearer for a winch launch, especially
if the sailplane has a well reclined seat. Also only
use very firm seat cushions if these are required.

Derek Copeland

[[email protected]]

Good advice Derek!

And if your seat back has adjustable 'arms', consider how those arms
will react under increased load and/or bumps, and take appropriate
steps to lock them in properly, or add support. Especially if you use a
more 'forward' position for the seat back.

Bob

Derek Copeland wrote:
> The UK Air Accident Investigation Branch (AAIB) has
> recently published a report on a fatal accident involving
> a DG600 sailplane back in 2005.
>
> The circumstances were that the DG600 took a winch
> launch, and rotated into an unusually steep climb after
> lift off. This was enough to slow down a slightly underpowered
> winch to the extent that the glider stalled and flicked
> into a spin. The pilot was killed in the ensuing crash.
>
> The experienced pilot was the owner of the DG600 and
> maintained it himself as a BGA inspector. It was assessed
> from the wreckage that the glider was correctly rigged
> and that all the controls were properly connected.
> The only anomaly found was that the ASI static was
> connected to the Total Energy probe, which might have
> caused the ASI to misread. However tests showed that
> this would only cause minor errors.
>
> The shoulder straps were found to be somewhat loose
> although, as the glider crashed inverted, this may
> have been as a result of the crash. It was concluded
> that the most likely cause of this accident was that
> the pilot had not sufficiently tightened his shoulder
> straps and had slid backwards up the seat, which caused
> him to inadvertently pull back on the stick in the
> process.
>
> I should point out that I had a somewhat similar experience
> when I took my first winch launch in a DG101 sailplane,
> and was only just about able to retain control with
> my fingertips at full stretch. My feet where well off
> the rudder pedals! DG single seaters have a very reclined
> seat position and the shoulder straps seem to be mounted
> a bit too far up.
>
> Can I recommend most strongly that you do your straps
> up really tightly and set the rudder pedals at least
> a couple of notches nearer for a winch launch, especially
> if the sailplane has a well reclined seat. Also only
> use very firm seat cushions if these are required.
>
> Derek Copeland

[Andrew Warbrick]

At 17:00 16 October 2006, Derek Copeland wrote:
>The only anomaly found was that the ASI static was
>connected to the Total Energy probe, which might have
>caused the ASI to misread. However tests showed that
>this would only cause minor errors.
>
How was this conclusion reached? I wouldn't call doubling
the ASI reading a minor error. Or did you mean that
the ASI was connected to a Prandtl tube static instead
of fuselage static?

[Doug Haluza]

Derek Copeland wrote:
> The UK Air Accident Investigation Branch (AAIB) has
> recently published a report on a fatal accident involving
> a DG600 sailplane back in 2005.
<snip>
> The only anomaly found was that the ASI static was
> connected to the Total Energy probe, which might have
> caused the ASI to misread. However tests showed that
> this would only cause minor errors.

This seems completely wrong to me. The TE probe should produce a
pressure below static equal to the dynamic pressure, so the
differential pressure to the ASI would be doubled, and the ASI would
read high by 70%. I would not consider this a minor error!

I would seriously question the test results, and the report's
conclusions based on this.

[Stephen]

"Derek Copeland" > wrote in
message ...
> The UK Air Accident Investigation Branch (AAIB) has
> recently published a report on a fatal accident involving
> a DG600 sailplane back in 2005.
> <snip>
> Can I recommend most strongly that you do your straps
> up really tightly and set the rudder pedals at least
> a couple of notches nearer for a winch launch, especially
> if the sailplane has a well reclined seat. Also only
> use very firm seat cushions if these are required.
>

I've had a similar "feet off the pedals experience" in a Std Cirrus when I
visited another club with a high power winch. My club, at that time, was
using reverse pulley auto tow so I'd never experienced a high acceleration
winch launch. I'm fortunate that I'm 6'3" so didn't slide too far back
before my head hit the canopy frame. I was thus able to keep my hand on the
stick.

The problem in that glider, and I suspect others, is that the shoulder
straps don't stop you sliding backwards regardless of how tight they are.
Unless the straps are attached to a point below your shoulders they can't
stop you. The other problem in the Std Cirrus is the lack of upholstery on
the seat pan, making it easy to slide on. My solution was to sit on a thin
rubber mat which stopped all movement.

Stephen

[Derek Copeland]

The ASI should be connected to a fuselage static, but
in the case of the accident glider it was connected
to some sort of double pronged European Total energy
(TE) probe in parallel with the varios.

T.E. probes produce a small amount of negative pressure
which increases with airspeed and thereby compensates
the vario for the height gains or losses associated
with speed changes. i.e converts it from a Vertical
Speed Indicator to a soaring Vario.

An ASI works by comparing pitot pressure with static
pressure, so reducing the static pressure will as you
say increase the ASI reading. However the glider had
been flown in this configuration for some time, so
the pilot would have been used to any errors produced.
The AAIB actually set up a rig with the same configuration
and found that the errors where quite small. Presumably
the high pressure generated by the pitot was much greater
than the low pressure generated by the TE probe.

If you want to be really pedantic, the shoulder straps
were actually found to be undone and too long after
the accident, but they may have slipped and then released
during the crash. There is however at least a possibility
that the pilot may have failed to secure the shoulder
straps before taking the launch.

As I have also slipped back in the cockpit of a DG
glider when I didn't quite tighten the shoulder straps
enough for a winch launch, this seems the most reasonable
explanation for this accident to me, and doesn't change
the basic recommendations.

Derek Copeland


At 11:06 17 October 2006, Doug Haluza wrote:
>
>Derek Copeland wrote:
>> The UK Air Accident Investigation Branch (AAIB) has
>> recently published a report on a fatal accident involving
>> a DG600 sailplane back in 2005.
>
>> The only anomaly found was that the ASI static was
>> connected to the Total Energy probe, which might have
>> caused the ASI to misread. However tests showed that
>> this would only cause minor errors.
>
>This seems completely wrong to me. The TE probe should
>produce a
>pressure below static equal to the dynamic pressure,
>so the
>differential pressure to the ASI would be doubled,
>and the ASI would
>read high by 70%. I would not consider this a minor
>error!
>
>I would seriously question the test results, and the
>report's
>conclusions based on this.
>
>

[Doug Haluza]

Derek Copeland wrote:
<snip>
> T.E. probes produce a small amount of negative pressure
> which increases with airspeed

Actually an ideal TE probe creates a "negative" differential pressure
exactly equal to the positive differential pressure of the pitot tube
(relative to static). If the ASI was connected to Pitot and TE (instead
of static) then the ASI would read 70% high, because dynamic pressure
is related to airspeed squarred.

> An ASI works by comparing pitot pressure with static
> pressure, so reducing the static pressure will as you
> say increase the ASI reading. However the glider had
> been flown in this configuration for some time, so
> the pilot would have been used to any errors produced.

No way he compensated for a 70% high reading.

> The AAIB actually set up a rig with the same configuration
> and found that the errors where quite small. Presumably
> the high pressure generated by the pitot was much greater
> than the low pressure generated by the TE probe.

This is not correct. Either the explanation is wrong or there was a
problem with the test.

> At 11:06 17 October 2006, Doug Haluza wrote:
> >
> >Derek Copeland wrote:
> >> The UK Air Accident Investigation Branch (AAIB) has
> >> recently published a report on a fatal accident involving
> >> a DG600 sailplane back in 2005.
> >
> >> The only anomaly found was that the ASI static was
> >> connected to the Total Energy probe, which might have
> >> caused the ASI to misread. However tests showed that
> >> this would only cause minor errors.
> >
> >This seems completely wrong to me. The TE probe should
> >produce a
> >pressure below static equal to the dynamic pressure,
> >so the
> >differential pressure to the ASI would be doubled,
> >and the ASI would
> >read high by 70%. I would not consider this a minor
> >error!
> >
> >I would seriously question the test results, and the
> >report's
> >conclusions based on this.
> >
> >

[Derek Copeland]

Wouldn't the exact effect depend on the relative areas
of the pot pitot and the usually very small holes in
the T.E. probe? The AAIB are normally very thorough
in their investigations, so I am happy to believe them,
and that this error was not the primary cause of the
accident. Neither am I recommending that you should
connect your instruments up in this way.

Derek Copeland

At 01:54 18 October 2006, Doug Haluza wrote:
>
>Derek Copeland wrote:
>
>> T.E. probes produce a small amount of negative pressure
>> which increases with airspeed
>
>Actually an ideal TE probe creates a 'negative' differential
>pressure
>exactly equal to the positive differential pressure
>of the pitot tube
>(relative to static). If the ASI was connected to Pitot
>and TE (instead
>of static) then the ASI would read 70% high, because
>dynamic pressure
>is related to airspeed squarred.
>
>> An ASI works by comparing pitot pressure with static
>> pressure, so reducing the static pressure will as
>>you
>> say increase the ASI reading. However the glider had
>> been flown in this configuration for some time, so
>> the pilot would have been used to any errors produced.
>
>No way he compensated for a 70% high reading.
>
>> The AAIB actually set up a rig with the same configuration
>> and found that the errors where quite small. Presumably
>> the high pressure generated by the pitot was much
>>greater
>> than the low pressure generated by the TE probe.
>
>This is not correct. Either the explanation is wrong
>or there was a
>problem with the test.
>
>> At 11:06 17 October 2006, Doug Haluza wrote:
>> >
>> >Derek Copeland wrote:
>> >> The UK Air Accident Investigation Branch (AAIB) has
>> >> recently published a report on a fatal accident involving
>> >> a DG600 sailplane back in 2005.
>> >
>> >> The only anomaly found was that the ASI static was
>> >> connected to the Total Energy probe, which might
>>>>have
>> >> caused the ASI to misread. However tests showed that
>> >> this would only cause minor errors.
>> >
>> >This seems completely wrong to me. The TE probe should
>> >produce a
>> >pressure below static equal to the dynamic pressure,
>> >so the
>> >differential pressure to the ASI would be doubled,
>> >and the ASI would
>> >read high by 70%. I would not consider this a minor
>> >error!
>> >
>> >I would seriously question the test results, and the
>> >report's
>> >conclusions based on this.
>> >
>> >
>
>

[Doug Haluza]

Derek Copeland wrote:
> Wouldn't the exact effect depend on the relative areas
> of the pot pitot and the usually very small holes in
> the T.E. probe? The AAIB are normally very thorough
> in their investigations, so I am happy to believe them,
> and that this error was not the primary cause of the
> accident. Neither am I recommending that you should
> connect your instruments up in this way.

No, the area of the openings would not matter, unless there was a
significant leak.

If your description is correct, then I would not assume that the
primary cause was the straps, which as you point out could not be
conclusively determined due to post impact damage. Can you check the
report again and make sure you have correctly reported the results?

[Bert Willing]

Doug,

the reading of an ASI is very rarely connected to winch launch accidents,
and certainly not in the initial climb.
Sliding back in the seat (or movement of a seatpan) during initial rotation
has already claimed a number of lives.

Bert

"Doug Haluza" > wrote in message
oups.com...
>
> Derek Copeland wrote:
>> Wouldn't the exact effect depend on the relative areas
>> of the pot pitot and the usually very small holes in
>> the T.E. probe? The AAIB are normally very thorough
>> in their investigations, so I am happy to believe them,
>> and that this error was not the primary cause of the
>> accident. Neither am I recommending that you should
>> connect your instruments up in this way.
>
> No, the area of the openings would not matter, unless there was a
> significant leak.
>
> If your description is correct, then I would not assume that the
> primary cause was the straps, which as you point out could not be
> conclusively determined due to post impact damage. Can you check the
> report again and make sure you have correctly reported the results?
>

[phil collin]

For the full report see the following URL
http://www.aaib.dft.gov.uk/publications/bulletins/september_2006/glaser_dirks_dg600_glider__bga_3445__tail_number_6 56_.cfm



Bert Willing wrote:
> Doug,
>
> the reading of an ASI is very rarely connected to winch launch accidents,
> and certainly not in the initial climb.
> Sliding back in the seat (or movement of a seatpan) during initial rotation
> has already claimed a number of lives.
>
> Bert
>
> "Doug Haluza" > wrote in message
> oups.com...
>> Derek Copeland wrote:
>>> Wouldn't the exact effect depend on the relative areas
>>> of the pot pitot and the usually very small holes in
>>> the T.E. probe? The AAIB are normally very thorough
>>> in their investigations, so I am happy to believe them,
>>> and that this error was not the primary cause of the
>>> accident. Neither am I recommending that you should
>>> connect your instruments up in this way.
>> No, the area of the openings would not matter, unless there was a
>> significant leak.
>>
>> If your description is correct, then I would not assume that the
>> primary cause was the straps, which as you point out could not be
>> conclusively determined due to post impact damage. Can you check the
>> report again and make sure you have correctly reported the results?
>>
>
>


--

Phil Collin
Partner Manager
T: 0870 861 0 300
E:
W: www.voicehost.co.uk

[Derek Copeland]

Looking at the diagram of the instrument layout in
this glider, it would appear that the total energy
tube was connected to the fuselage statics and then
in turn to all the pressure instruments. I would guess
that effect of the total energy tube on the ASI would
therefore be greatly reduced due to leakage through
the normal static holes.

Derek Copeland


At 10:06 18 October 2006, Phil Collin wrote:
>For the full report see the following URL
>http://www.aaib.dft.gov.uk/publications/bulletins/september_2006/g
>>laser_dirks_dg600_glider__bga_3445__tail_number_65 6_.cfm
>
>
>
>Bert Willing wrote:
>> Doug,
>>
>> the reading of an ASI is very rarely connected to
>>winch launch accidents,
>> and certainly not in the initial climb.
>> Sliding back in the seat (or movement of a seatpan)
>>during initial rotation
>> has already claimed a number of lives.
>>
>> Bert
>>
>> 'Doug Haluza' wrote in message
>> oups.com...
>>> Derek Copeland wrote:
>>>> Wouldn't the exact effect depend on the relative areas
>>>> of the pot pitot and the usually very small holes
>>>>in
>>>> the T.E. probe? The AAIB are normally very thorough
>>>> in their investigations, so I am happy to believe
>>>>them,
>>>> and that this error was not the primary cause of the
>>>> accident. Neither am I recommending that you should
>>>> connect your instruments up in this way.
>>> No, the area of the openings would not matter, unless
>>>there was a
>>> significant leak.
>>>
>>> If your description is correct, then I would not assume
>>>that the
>>> primary cause was the straps, which as you point out
>>>could not be
>>> conclusively determined due to post impact damage.
>>>Can you check the
>>> report again and make sure you have correctly reported
>>>the results?
>>>
>>
>>
>
>
>--
>
>Phil Collin
>Partner Manager
>T: 0870 861 0 300
>E:
>W: www.voicehost.co.uk
>
>
>
>
>

[Nyal Williams]

This is somewhat analagous to reported accidents by
Cessna pilots on takeoff; if the adjustable seats
are not properly locked in their rails the seat can
slide backward, making it impossible to push the yoke
forward.

Perhaps we need a two-point attachment for each of
the shoulder straps -- the one above the shoulders
that already is in place and which keeps the body from
being thrown forward, plus a second one from be bottom
of the seat pan, and which would prevent the body from
moving upward and aft. This second strap could also
protect against cranial collision with the canopy.


Anyone for seven-point harness?

At 09:30 18 October 2006, Bert Willing wrote:
>Doug,
>
>the reading of an ASI is very rarely connected to winch
>launch accidents,
>and certainly not in the initial climb.
>Sliding back in the seat (or movement of a seatpan)
>during initial rotation
>has already claimed a number of lives.
>
>Bert
>
>'Doug Haluza' wrote in message
oups.com...
>>
>> Derek Copeland wrote:
>>> Wouldn't the exact effect depend on the relative areas
>>> of the pot pitot and the usually very small holes
>>>in
>>> the T.E. probe? The AAIB are normally very thorough
>>> in their investigations, so I am happy to believe
>>>them,
>>> and that this error was not the primary cause of the
>>> accident. Neither am I recommending that you should
>>> connect your instruments up in this way.
>>
>> No, the area of the openings would not matter, unless
>>there was a
>> significant leak.
>>
>> If your description is correct, then I would not assume
>>that the
>> primary cause was the straps, which as you point out
>>could not be
>> conclusively determined due to post impact damage.
>>Can you check the
>> report again and make sure you have correctly reported
>>the results?
>>
>
>
>

[Bert Willing]

I guess we just need to secure the shoulder straps properly ? ...

"Nyal Williams" > wrote in message
...
> This is somewhat analagous to reported accidents by
> Cessna pilots on takeoff; if the adjustable seats
> are not properly locked in their rails the seat can
> slide backward, making it impossible to push the yoke
> forward.
>
> Perhaps we need a two-point attachment for each of
> the shoulder straps -- the one above the shoulders
> that already is in place and which keeps the body from
> being thrown forward, plus a second one from be bottom
> of the seat pan, and which would prevent the body from
> moving upward and aft. This second strap could also
> protect against cranial collision with the canopy.
>
>
> Anyone for seven-point harness?
>
> At 09:30 18 October 2006, Bert Willing wrote:
>>Doug,
>>
>>the reading of an ASI is very rarely connected to winch
>>launch accidents,
>>and certainly not in the initial climb.
>>Sliding back in the seat (or movement of a seatpan)
>>during initial rotation
>>has already claimed a number of lives.
>>
>>Bert
>>
>>'Doug Haluza' wrote in message
oups.com...
>>>
>>> Derek Copeland wrote:
>>>> Wouldn't the exact effect depend on the relative areas
>>>> of the pot pitot and the usually very small holes
>>>>in
>>>> the T.E. probe? The AAIB are normally very thorough
>>>> in their investigations, so I am happy to believe
>>>>them,
>>>> and that this error was not the primary cause of the
>>>> accident. Neither am I recommending that you should
>>>> connect your instruments up in this way.
>>>
>>> No, the area of the openings would not matter, unless
>>>there was a
>>> significant leak.
>>>
>>> If your description is correct, then I would not assume
>>>that the
>>> primary cause was the straps, which as you point out
>>>could not be
>>> conclusively determined due to post impact damage.
>>>Can you check the
>>> report again and make sure you have correctly reported
>>>the results?
>>>
>>
>>
>>
>
>
>

[Bill Daniels]

"Nyal Williams" > wrote in message
...
> This is somewhat analagous to reported accidents by
> Cessna pilots on takeoff; if the adjustable seats
> are not properly locked in their rails the seat can
> slide backward, making it impossible to push the yoke
> forward.

That brings back nightmares. I had a Cessna 180 seat come off badly worn
tracks on takeoff. Somehow, I was able to scramble into the right front
seat before crashing.

Bill Daniels

[Nyal Williams]

Bert, I think you must not have read all this thread;
it was pointed out that shoulder strap connections
are too high and, while preventing the upper body from
going forward, do not prevent an upward and aft movement.
With current setups, no amount of tightening will
prevent this for short/small persons.


At 14:42 19 October 2006, Bert Willing wrote:
>I guess we just need to secure the shoulder straps
>properly ? ...
>
>'Nyal Williams' wrote in message
...
>> This is somewhat analagous to reported accidents by
>> Cessna pilots on takeoff; if the adjustable seats
>> are not properly locked in their rails the seat can
>> slide backward, making it impossible to push the yoke
>> forward.
>>
>> Perhaps we need a two-point attachment for each of
>> the shoulder straps -- the one above the shoulders
>> that already is in place and which keeps the body
>>from
>> being thrown forward, plus a second one from be bottom
>> of the seat pan, and which would prevent the body
>>from
>> moving upward and aft. This second strap could also
>> protect against cranial collision with the canopy.
>>
>>
>> Anyone for seven-point harness?
>>
>> At 09:30 18 October 2006, Bert Willing wrote:
>>>Doug,
>>>
>>>the reading of an ASI is very rarely connected to winch
>>>launch accidents,
>>>and certainly not in the initial climb.
>>>Sliding back in the seat (or movement of a seatpan)
>>>during initial rotation
>>>has already claimed a number of lives.
>>>
>>>Bert
>>>
>>>'Doug Haluza' wrote in message
oups.com...
>>>>
>>>> Derek Copeland wrote:
>>>>> Wouldn't the exact effect depend on the relative areas
>>>>> of the pot pitot and the usually very small holes
>>>>>in
>>>>> the T.E. probe? The AAIB are normally very thorough
>>>>> in their investigations, so I am happy to believe
>>>>>them,
>>>>> and that this error was not the primary cause of the
>>>>> accident. Neither am I recommending that you should
>>>>> connect your instruments up in this way.
>>>>
>>>> No, the area of the openings would not matter, unless
>>>>there was a
>>>> significant leak.
>>>>
>>>> If your description is correct, then I would not assume
>>>>that the
>>>> primary cause was the straps, which as you point out
>>>>could not be
>>>> conclusively determined due to post impact damage.
>>>>Can you check the
>>>> report again and make sure you have correctly reported
>>>>the results?
>>>>
>>>
>>>
>>>
>>
>>
>>
>
>
>

[Martin Gregorie[_1_]]

Nyal Williams wrote:
>
> Perhaps we need a two-point attachment for each of
> the shoulder straps -- the one above the shoulders
> that already is in place and which keeps the body from
> being thrown forward, plus a second one from be bottom
> of the seat pan, and which would prevent the body from
> moving upward and aft. This second strap could also
> protect against cranial collision with the canopy.
>
Just be wary of where the shoulder straps attach in the glider. If they
are anchored below shoulder height there's no problem.
ASW-19/Pegase/ASW-20 and Libelle are OK from this respect, as are Juniors.

Some gliders need careful checking because the exact seat arrangement
matters: Some of the early Discii, those fitted with a padded ply seat
back pivoted on a horizontal rod about half way up, have the strap
anchors set too high and you can float up slightly no matter how tight
the straps are. I think the straps run over the top of the seat back
which stops them pulling down on your shoulders quite hard enough.
However, the later models with a shaped glass fibre seat back that
pivots at the bottom don't show this problem.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Bert Willing]

Nyal, I do have read this thread.
If the attachment point of the shoulder straps are too high, a thin layer of
foam or rubber on the seat pan is all what's needed.
Having double attachment points on the shoulder straps is big means to solve
an easily solved problem - you go through a certification loop, you need to
think about egress restrictions and all this stuff.

"Nyal Williams" > wrote in message
...
> Bert, I think you must not have read all this thread;
> it was pointed out that shoulder strap connections
> are too high and, while preventing the upper body from
> going forward, do not prevent an upward and aft movement.
> With current setups, no amount of tightening will
> prevent this for short/small persons.
>
>
> At 14:42 19 October 2006, Bert Willing wrote:
>>I guess we just need to secure the shoulder straps
>>properly ? ...
>>
>>'Nyal Williams' wrote in message
...
>>> This is somewhat analagous to reported accidents by
>>> Cessna pilots on takeoff; if the adjustable seats
>>> are not properly locked in their rails the seat can
>>> slide backward, making it impossible to push the yoke
>>> forward.
>>>
>>> Perhaps we need a two-point attachment for each of
>>> the shoulder straps -- the one above the shoulders
>>> that already is in place and which keeps the body
>>>from
>>> being thrown forward, plus a second one from be bottom
>>> of the seat pan, and which would prevent the body
>>>from
>>> moving upward and aft. This second strap could also
>>> protect against cranial collision with the canopy.
>>>
>>>
>>> Anyone for seven-point harness?
>>>
>>> At 09:30 18 October 2006, Bert Willing wrote:
>>>>Doug,
>>>>
>>>>the reading of an ASI is very rarely connected to winch
>>>>launch accidents,
>>>>and certainly not in the initial climb.
>>>>Sliding back in the seat (or movement of a seatpan)
>>>>during initial rotation
>>>>has already claimed a number of lives.
>>>>
>>>>Bert
>>>>
>>>>'Doug Haluza' wrote in message
oups.com...
>>>>>
>>>>> Derek Copeland wrote:
>>>>>> Wouldn't the exact effect depend on the relative areas
>>>>>> of the pot pitot and the usually very small holes
>>>>>>in
>>>>>> the T.E. probe? The AAIB are normally very thorough
>>>>>> in their investigations, so I am happy to believe
>>>>>>them,
>>>>>> and that this error was not the primary cause of the
>>>>>> accident. Neither am I recommending that you should
>>>>>> connect your instruments up in this way.
>>>>>
>>>>> No, the area of the openings would not matter, unless
>>>>>there was a
>>>>> significant leak.
>>>>>
>>>>> If your description is correct, then I would not assume
>>>>>that the
>>>>> primary cause was the straps, which as you point out
>>>>>could not be
>>>>> conclusively determined due to post impact damage.
>>>>>Can you check the
>>>>> report again and make sure you have correctly reported
>>>>>the results?
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>>
>
>
>

[Tim Ward[_1_]]

"Nyal Williams" > wrote in message
...
> This is somewhat analagous to reported accidents by
> Cessna pilots on takeoff; if the adjustable seats
> are not properly locked in their rails the seat can
> slide backward, making it impossible to push the yoke
> forward.
>
> Perhaps we need a two-point attachment for each of
> the shoulder straps -- the one above the shoulders
> that already is in place and which keeps the body from
> being thrown forward, plus a second one from be bottom
> of the seat pan, and which would prevent the body from
> moving upward and aft. This second strap could also
> protect against cranial collision with the canopy.
>
>
> Anyone for seven-point harness?

I've been reading this, and I wonder if you couldn't just sew some straps to
the back side of the existing straps, then bring those down to a rectangle
of ballistic cloth that would lay on and more-or-less cover the seat back
and seat pan.
The higher the nose rotates, the more your weight would tend to squeeze the
ballistic cloth between your parachute and the seat back.

Tim Ward

[Nyal Williams]

[Nyal Williams]

Bert,

As I lay awake this morning before getting up, I began
to understand your reasoning, and you might be quite
right. A thin layer of foam or rubber could provide
enough friction across the whole back or the 'chute
and against all of the slippery surface of the seat
pan/back rest and grip enough to prevent sliding.
This would probably work if the straps are really snug.
It is not a matter of spacing but of a large area of
friction.

My notion was to put the entire force against the shoulders
and straps; if this were the case the strap attach
points would have to be lower and/or a fifth attach
point in the crotch area to prevent strap movement
aft.

Best,

Nyal




At 08:00 20 October 2006, Bert Willing wrote:
>Nyal, I do have read this thread.
>If the attachment point of the shoulder straps are
>too high, a thin layer of
>foam or rubber on the seat pan is all what's needed.
>Having double attachment points on the shoulder straps
>is big means to solve
>an easily solved problem - you go through a certification
>loop, you need to
>think about egress restrictions and all this stuff.
>
>'Nyal Williams' wrote in message
...
>> Bert, I think you must not have read all this thread;
>> it was pointed out that shoulder strap connections
>> are too high and, while preventing the upper body
>>from
>> going forward, do not prevent an upward and aft movement.
>> With current setups, no amount of tightening will
>> prevent this for short/small persons.
>>
>>
>> At 14:42 19 October 2006, Bert Willing wrote:
>>>I guess we just need to secure the shoulder straps
>>>properly ? ...
>>>
>>>'Nyal Williams' wrote in message
...
>>>> This is somewhat analagous to reported accidents by
>>>> Cessna pilots on takeoff; if the adjustable seats
>>>> are not properly locked in their rails the seat can
>>>> slide backward, making it impossible to push the yoke
>>>> forward.
>>>>
>>>> Perhaps we need a two-point attachment for each of
>>>> the shoulder straps -- the one above the shoulders
>>>> that already is in place and which keeps the body
>>>>from
>>>> being thrown forward, plus a second one from be bottom
>>>> of the seat pan, and which would prevent the body
>>>>from
>>>> moving upward and aft. This second strap could also
>>>> protect against cranial collision with the canopy.
>>>>
>>>>
>>>> Anyone for seven-point harness?

[Bill Daniels]

I've been following this thread with interest. Sholder straps anchored high
on the seat back prevent the pilot from moving up and forward but are less
effective in preventing up and back movements as might be encountered in a
winch launch or turbulence.

I like Nyal's original suggestion of two additional vertical straps located
between the pilots sholders and the sholder strap anchor points holding down
the sholder straps. The next time I have my glider out of the trailer, I'm
going to look carefully at this possibility. I think it would only require
straps and buckles attached to the landing gear frame - simple, cheap and
likely to be highly effective. Thanks Nyal!

Bert's suggestion of a "friction pad" behind the pilots's back to anchor the
additional straps is somewhat problematic since I would want the solution to
work for both winch launch and for negative G "bumps" encountered in
turbulence. In a negative G scenario the friction pad idea is less likely
to provide an anchor.

Bill Daniels


"Nyal Williams" > wrote in message
...
> Bert,
>
> As I lay awake this morning before getting up, I began
> to understand your reasoning, and you might be quite
> right. A thin layer of foam or rubber could provide
> enough friction across the whole back or the 'chute
> and against all of the slippery surface of the seat
> pan/back rest and grip enough to prevent sliding.
> This would probably work if the straps are really snug.
> It is not a matter of spacing but of a large area of
> friction.
>
> My notion was to put the entire force against the shoulders
> and straps; if this were the case the strap attach
> points would have to be lower and/or a fifth attach
> point in the crotch area to prevent strap movement
> aft.
>
> Best,
>
> Nyal
>
>
>
>
> At 08:00 20 October 2006, Bert Willing wrote:
>>Nyal, I do have read this thread.
>>If the attachment point of the shoulder straps are
>>too high, a thin layer of
>>foam or rubber on the seat pan is all what's needed.
>>Having double attachment points on the shoulder straps
>>is big means to solve
>>an easily solved problem - you go through a certification
>>loop, you need to
>>think about egress restrictions and all this stuff.
>>
>>'Nyal Williams' wrote in message
...
>>> Bert, I think you must not have read all this thread;
>>> it was pointed out that shoulder strap connections
>>> are too high and, while preventing the upper body
>>>from
>>> going forward, do not prevent an upward and aft movement.
>>> With current setups, no amount of tightening will
>>> prevent this for short/small persons.
>>>
>>>
>>> At 14:42 19 October 2006, Bert Willing wrote:
>>>>I guess we just need to secure the shoulder straps
>>>>properly ? ...
>>>>
>>>>'Nyal Williams' wrote in message
...
>>>>> This is somewhat analagous to reported accidents by
>>>>> Cessna pilots on takeoff; if the adjustable seats
>>>>> are not properly locked in their rails the seat can
>>>>> slide backward, making it impossible to push the yoke
>>>>> forward.
>>>>>
>>>>> Perhaps we need a two-point attachment for each of
>>>>> the shoulder straps -- the one above the shoulders
>>>>> that already is in place and which keeps the body
>>>>>from
>>>>> being thrown forward, plus a second one from be bottom
>>>>> of the seat pan, and which would prevent the body
>>>>>from
>>>>> moving upward and aft. This second strap could also
>>>>> protect against cranial collision with the canopy.
>>>>>
>>>>>
>>>>> Anyone for seven-point harness?
>
>
>

[Bert Willing]

The only solution for "negative g-bumps" are properly located and secured
lap straps.

"Bill Daniels" <bildan@comcast-dot-net> wrote in message
...
> I've been following this thread with interest. Sholder straps anchored
> high on the seat back prevent the pilot from moving up and forward but are
> less effective in preventing up and back movements as might be encountered
> in a winch launch or turbulence.
>
> I like Nyal's original suggestion of two additional vertical straps
> located between the pilots sholders and the sholder strap anchor points
> holding down the sholder straps. The next time I have my glider out of
> the trailer, I'm going to look carefully at this possibility. I think it
> would only require straps and buckles attached to the landing gear frame -
> simple, cheap and likely to be highly effective. Thanks Nyal!
>
> Bert's suggestion of a "friction pad" behind the pilots's back to anchor
> the additional straps is somewhat problematic since I would want the
> solution to work for both winch launch and for negative G "bumps"
> encountered in turbulence. In a negative G scenario the friction pad idea
> is less likely to provide an anchor.
>
> Bill Daniels
>
>
> "Nyal Williams" > wrote in
> message ...
>> Bert,
>>
>> As I lay awake this morning before getting up, I began
>> to understand your reasoning, and you might be quite
>> right. A thin layer of foam or rubber could provide
>> enough friction across the whole back or the 'chute
>> and against all of the slippery surface of the seat
>> pan/back rest and grip enough to prevent sliding.
>> This would probably work if the straps are really snug.
>> It is not a matter of spacing but of a large area of
>> friction.
>>
>> My notion was to put the entire force against the shoulders
>> and straps; if this were the case the strap attach
>> points would have to be lower and/or a fifth attach
>> point in the crotch area to prevent strap movement
>> aft.
>>
>> Best,
>>
>> Nyal
>>
>>
>>
>>
>> At 08:00 20 October 2006, Bert Willing wrote:
>>>Nyal, I do have read this thread.
>>>If the attachment point of the shoulder straps are
>>>too high, a thin layer of
>>>foam or rubber on the seat pan is all what's needed.
>>>Having double attachment points on the shoulder straps
>>>is big means to solve
>>>an easily solved problem - you go through a certification
>>>loop, you need to
>>>think about egress restrictions and all this stuff.
>>>
>>>'Nyal Williams' wrote in message
...
>>>> Bert, I think you must not have read all this thread;
>>>> it was pointed out that shoulder strap connections
>>>> are too high and, while preventing the upper body
>>>>from
>>>> going forward, do not prevent an upward and aft movement.
>>>> With current setups, no amount of tightening will
>>>> prevent this for short/small persons.
>>>>
>>>>
>>>> At 14:42 19 October 2006, Bert Willing wrote:
>>>>>I guess we just need to secure the shoulder straps
>>>>>properly ? ...
>>>>>
>>>>>'Nyal Williams' wrote in message
...
>>>>>> This is somewhat analagous to reported accidents by
>>>>>> Cessna pilots on takeoff; if the adjustable seats
>>>>>> are not properly locked in their rails the seat can
>>>>>> slide backward, making it impossible to push the yoke
>>>>>> forward.
>>>>>>
>>>>>> Perhaps we need a two-point attachment for each of
>>>>>> the shoulder straps -- the one above the shoulders
>>>>>> that already is in place and which keeps the body
>>>>>>from
>>>>>> being thrown forward, plus a second one from be bottom
>>>>>> of the seat pan, and which would prevent the body
>>>>>>from
>>>>>> moving upward and aft. This second strap could also
>>>>>> protect against cranial collision with the canopy.
>>>>>>
>>>>>>
>>>>>> Anyone for seven-point harness?
>>
>>
>>
>
>