TE errors

My system, a L-Nav and a Winter variometer. Both have their own capacities,
but they share a TE probe. I have begun to see some bad compensation and
getting some 'stick' thermals. Where should I start looking for leaks,
etc.?

Thanks,
Fred Blair

f.blair wrote:
My system, a L-Nav and a Winter variometer. Both have their own capacities,
but they share a TE probe. I have begun to see some bad compensation and
getting some 'stick' thermals. Where should I start looking for leaks,
etc.?

Well, the obvious thing would be to try to isolate the problem. Take
the Winter out of the system and fly with the L-NAV alone, then
vice-versa. If you see stick thermals in both cases, the leak is
someplace between the panel and the probe, or you need to start
filing/filling the end of the probe (assuming it is a Nicks type). If
you have problems with one, but not the other, the leak is somewhere
around or in the one that has the problem. If you get good compensation
in both cases, you likely have cross-flow between the two varios, and
need to move the split farther back from the panel.

Marc

If you are getting 'stick thermals' the leak is between
the instruments and the probe. The likeliest place
is where the probe plugs into the fin, failing that
it is probably somewhere in the tubing and connections
under the panel. If you have one of the screw up connectors
(four or sic tube) that connect all of the pane plumbing
to the incoming tubes, make sure the 'O' rings in it
are not perished/damaged and it is done up tightly.
The T or Y pieces that connect the tubes together
quite often crack at the corners. Sometimes the plastic
tubes harden with age and no longer make a good seal
at the connections, easiest thing is just replace the
tubing with new stuff.

If you are really unlucky, the leak could be somewhere
inside the fusilage or fin, most likely the connection
just inside the fin where the probe enters. Fortunatly
that is rare. Good luck


At 02:30 06 March 2005, F.Blair wrote:
My system, a L-Nav and a Winter variometer. Both have
their own capacities,
but they share a TE probe. I have begun to see some
bad compensation and
getting some 'stick' thermals. Where should I start
looking for leaks,
etc.?

Thanks,
Fred Blair

I agree with everything in the 2 previous replies.

The very first thing I would do is disconnect your
TE line as close to the instruments as possible, make
sure that it has no other connections to other instruments
(eg is it a 2 seater?), tape over the little holes
in the TE probe and test whether the line holds positive
or negative pressure. As Chris says a tiny leak in
that line could be from the TE tube seal or from a
connector in the line but a big leak like an open tube
would likely be the end of the tube having fallen off
the connector in the fin. In the case of an open tube
it is surprisingly easy to identify the approximate
position of the leak by using the bell end a stethoscope
on the side of the glider fuselage and fin while someone
blows into the tube. The stethoscope needs to have
a close seal to the surface to work properly.

A bit more of a problem to get pictures or a view of
the disconnected tube inside the fin to for absolute
confirmation of the right place to cut the required
hole in the fin to reconnect the tube.

(This is comes from experiences with a newly delivered
glider - tie wraps aren't the best way of holding
tubes onto connectors)

If the rear end of your system is OK then follow the
previous posters' advice about the panel end of the
system.

John Galloway

At 08:30 06 March 2005, Chris Rollings wrote:
If you are getting 'stick thermals' the leak is between
the instruments and the probe. The likeliest place
is where the probe plugs into the fin, failing that
it is probably somewhere in the tubing and connections
under the panel. If you have one of the screw up connectors
(four or sic tube) that connect all of the pane plumbing
to the incoming tubes, make sure the 'O' rings in it
are not perished/damaged and it is done up tightly.
The T or Y pieces that connect the tubes together
quite often crack at the corners. Sometimes the plastic
tubes harden with age and no longer make a good seal
at the connections, easiest thing is just replace the
tubing with new stuff.

If you are really unlucky, the leak could be somewhere
inside the fusilage or fin, most likely the connection
just inside the fin where the probe enters. Fortunatly
that is rare. Good luck


At 02:30 06 March 2005, F.Blair wrote:
My system, a L-Nav and a Winter variometer. Both have
their own capacities,
but they share a TE probe. I have begun to see some
bad compensation and
getting some 'stick' thermals. Where should I start
looking for leaks,
etc.?

Thanks,
Fred Blair

"John Galloway" wrote in message
...
I agree with everything in the 2 previous replies.

The very first thing I would do is disconnect your
TE line as close to the instruments as possible, make
sure that it has no other connections to other instruments
(eg is it a 2 seater?), tape over the little holes
in the TE probe and test whether the line holds positive
or negative pressure. As Chris says a tiny leak in
that line could be from the TE tube seal or from a
connector in the line but a big leak like an open tube
would likely be the end of the tube having fallen off
the connector in the fin. In the case of an open tube
it is surprisingly easy to identify the approximate
position of the leak by using the bell end a stethoscope
on the side of the glider fuselage and fin while someone
blows into the tube. The stethoscope needs to have
a close seal to the surface to work properly.

A bit more of a problem to get pictures or a view of
the disconnected tube inside the fin to for absolute
confirmation of the right place to cut the required
hole in the fin to reconnect the tube.

(This is comes from experiences with a newly delivered
glider - tie wraps aren't the best way of holding
tubes onto connectors)

If the rear end of your system is OK then follow the
previous posters' advice about the panel end of the
system.

John Galloway

At 08:30 06 March 2005, Chris Rollings wrote:
If you are getting 'stick thermals' the leak is between
the instruments and the probe. The likeliest place
is where the probe plugs into the fin, failing that
it is probably somewhere in the tubing and connections
under the panel. If you have one of the screw up connectors
(four or sic tube) that connect all of the pane plumbing
to the incoming tubes, make sure the 'O' rings in it
are not perished/damaged and it is done up tightly.
The T or Y pieces that connect the tubes together
quite often crack at the corners. Sometimes the plastic
tubes harden with age and no longer make a good seal
at the connections, easiest thing is just replace the
tubing with new stuff.

If you are really unlucky, the leak could be somewhere
inside the fusilage or fin, most likely the connection
just inside the fin where the probe enters. Fortunatly
that is rare. Good luck


At 02:30 06 March 2005, F.Blair wrote:
My system, a L-Nav and a Winter variometer. Both have
their own capacities,
but they share a TE probe. I have begun to see some
bad compensation and
getting some 'stick' thermals. Where should I start
looking for leaks,
etc.?

Thanks,
Fred Blair

One thing I'd use a vacuum test and not risk blowing the tube off the end
that's good!!!

Peter.

At 21:00 06 March 2005, Peter Seddon wrote:

'John Galloway' wrote in message
...
I agree with everything in the 2 previous replies.

The very first thing I would do is disconnect your
TE line as close to the instruments as possible, make
sure that it has no other connections to other instruments
(eg is it a 2 seater?), tape over the little holes
in the TE probe and test whether the line holds positive
or negative pressure. As Chris says a tiny leak in
that line could be from the TE tube seal or from a
connector in the line but a big leak like an open
tube
would likely be the end of the tube having fallen
off
the connector in the fin. In the case of an open
tube
it is surprisingly easy to identify the approximate
position of the leak by using the bell end a stethoscope
on the side of the glider fuselage and fin while someone
blows into the tube. The stethoscope needs to have
a close seal to the surface to work properly.

A bit more of a problem to get pictures or a view
of
the disconnected tube inside the fin to for absolute
confirmation of the right place to cut the required
hole in the fin to reconnect the tube.

(This is comes from experiences with a newly delivered
glider - tie wraps aren't the best way of holding
tubes onto connectors)

If the rear end of your system is OK then follow the
previous posters' advice about the panel end of the
system.

John Galloway

At 08:30 06 March 2005, Chris Rollings wrote:
If you are getting 'stick thermals' the leak is between
the instruments and the probe. The likeliest place
is where the probe plugs into the fin, failing that
it is probably somewhere in the tubing and connections
under the panel. If you have one of the screw up connectors
(four or sic tube) that connect all of the pane plumbing
to the incoming tubes, make sure the 'O' rings in it
are not perished/damaged and it is done up tightly.
The T or Y pieces that connect the tubes together
quite often crack at the corners. Sometimes the plastic
tubes harden with age and no longer make a good seal
at the connections, easiest thing is just replace the
tubing with new stuff.

If you are really unlucky, the leak could be somewhere
inside the fusilage or fin, most likely the connection
just inside the fin where the probe enters. Fortunatly
that is rare. Good luck


At 02:30 06 March 2005, F.Blair wrote:
My system, a L-Nav and a Winter variometer. Both have
their own capacities,
but they share a TE probe. I have begun to see some
bad compensation and
getting some 'stick' thermals. Where should I start
looking for leaks,
etc.?

Thanks,
Fred Blair

One thing I'd use a vacuum test and not risk blowing
the tube off the end
that's good!!!

Peter.

Yes I agree. It didn't occur to me that anyone would
think of applying a lot of positive pressure to a sealed
or almost sealed system. The simplest first step is
just to use gentle oral suction and stick your tongue
over the end of the tube to see if it keeps a seal.
However if you find almost no resistance and there
is clearly a disconnected tube somewhere then blowing
hard enough to make a sound that can be picked up by
a stethoscope along the fin and tailboom is the easiest
way I know to narrow down the site of the disconnection.
In our case I could clearly hear that the the tube
was disconnected at the top of the fin.

John Galloway

This article from borgelt will answer most questions:
http://www.borgeltinstruments.com/Leaks.pdf

Walter

Seems to be a good procedure,
thank you
Walter