Do your straps up tightly for winch launches!

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.

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.

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.

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?

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?

For the full report see the following URL
http://www.aaib.dft.gov.uk/publicati...ber_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

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/publicati...ptember_2006/g
laser_dirks_dg600_glider__bga_3445__tail_number_ 656_.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

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
roups.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?

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
groups.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?

"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