Grob 103 question

On May 23, 1:00 pm, Olin wrote:
We have a G103 with an esa-systems multi function probe. The probe
serves as a static, pitot and total energy ports. The socket that it
plugs into is mounted in the vertical stabilizer and Three tubes run
forward to service flight instruments. The socket contains three o-
rings to keep the three ports separated when the probe is inserted.
These o-rings deteriorate over time of course and allow leakage
between the ports and erroneous instrument readings.

Two of the o-rings are easily replaceable from the front opening. The
third o-ring is small (~1/8" ID) and not so easily replaced as it is
deep in the socket. Wings & Wheels has a nice diagram of the socket
(type UN).

It almost looks to me like you have to dig into the vertical stab and
remove the socket and disassemble it to remove this o-ring, unless
there is a special tool or method to get it out.

Any ideas? Perhaps some of you have traveled this road before.

Thanks.

You have it correct, you cut out the tripple probe mount to do this.
Good huh? Obviously try to confirm this is really the problem before
doing all this work (i.e. a leakdown test between the rear most and
middle ports.

I always put a tape over the probe port when not in use to keep dust
out.
Club ships etc. tied out are often best left with the probles left in
them to avoid wear and tear on the O-rings (others may disagree).
The annual was just done on my glider - including cleaning the mount
and lubricating the o-rings with a very small amount of silicone (make
sure this is being done to your glider, more frequently if the probe
is inserted/removed a lot).

Darryl

On May 23, 1:27 pm, Darryl Ramm wrote:
On May 23, 1:00 pm, Olin wrote:



We have a G103 with an esa-systems multi function probe. The probe
serves as a static, pitot and total energy ports. The socket that it
plugs into is mounted in the vertical stabilizer and Three tubes run
forward to service flight instruments. The socket contains three o-
rings to keep the three ports separated when the probe is inserted.
These o-rings deteriorate over time of course and allow leakage
between the ports and erroneous instrument readings.

Two of the o-rings are easily replaceable from the front opening. The
third o-ring is small (~1/8" ID) and not so easily replaced as it is
deep in the socket. Wings & Wheels has a nice diagram of the socket
(type UN).

It almost looks to me like you have to dig into the vertical stab and
remove the socket and disassemble it to remove this o-ring, unless
there is a special tool or method to get it out.

Any ideas? Perhaps some of you have traveled this road before.

Thanks.

You have it correct, you cut out the tripple probe mount to do this.
Good huh? Obviously try to confirm this is really the problem before
doing all this work (i.e. a leakdown test between the rear most and
middle ports.

I always put a tape over the probe port when not in use to keep dust
out.
Club ships etc. tied out are often best left with the probles left in
them to avoid wear and tear on the O-rings (others may disagree).
The annual was just done on my glider - including cleaning the mount
and lubricating the o-rings with a very small amount of silicone (make
sure this is being done to your glider, more frequently if the probe
is inserted/removed a lot).

Darryl

And I forgot - Tim at Wings and Wheels normally has the ESA o-ring
kits which may be less hassle than trying to source elsewhere.

Darryl

Darryl Ramm wrote:
I always put a tape over the probe port when not in use to keep dust
out.

In my opinion, this requires a disclaimer. Nothing would ever happen to
Darryl's instruments, of course, but for the rest of us, if one has
expensive mechanical varios, one would be ill-advised to place tape or
any other airtight seals on the probe port. I don't think we need
another long thread on whether or why this is a problem, but based on
first-hand (expensive) experience, don't do it. I keep a collection of
vinyl caps (available from McMaster-Carr or any large hardware store)
that fit the probe port, each with a tiny hole in the center that I made
with a heated needle...

Marc

On May 23, 8:07 pm, Marc Ramsey wrote:
Darryl Ramm wrote:
I always put a tape over the probe port when not in use to keep dust
out.

In my opinion, this requires a disclaimer. Nothing would ever happen to
Darryl's instruments, of course, but for the rest of us, if one has
expensive mechanical varios, one would be ill-advised to place tape or
any other airtight seals on the probe port. I don't think we need
another long thread on whether or why this is a problem, but based on
first-hand (expensive) experience, don't do it. I keep a collection of
vinyl caps (available from McMaster-Carr or any large hardware store)
that fit the probe port, each with a tiny hole in the center that I made
with a heated needle...

Marc

Marc

Lets make it a concise short thread then. You got me - I'm not sure
how this would hurt a vane style (winter) vario or even a Sage vario
since all ports of the triple probe mechanism will be at the same
pressure and may all be increasing or decreasing in pressure (but at
the same pressure) due to temperature changes or altitude (towing
glider in the trailer). So what exactly causes the failure?

If you have separate TE/pitot etc. tail probes, or instruments cross
configured to say use the triple probe TE line but fuselage static
sources etc., then taping over a port I could see might cause damage -
but 1. that's not what was being discussed and 2. I'd also consider
cross configured pneumatic systems misconfigured. Single port devices
like the Altimeter should not be on the triple probe static port. I'd
be surprised if absolute pressure transducer electronic compensated
varios would have such little headroom they could be damage by this.

Still I'll give you that those plastic cups better than tape just
becasue they don't leave gummy residue and probably less prone to
falling off than a piece of tape.

Darryl

Darryl Ramm wrote:
Lets make it a concise short thread then. You got me - I'm not sure
how this would hurt a vane style (winter) vario or even a Sage vario
since all ports of the triple probe mechanism will be at the same
pressure and may all be increasing or decreasing in pressure (but at
the same pressure) due to temperature changes or altitude (towing
glider in the trailer). So what exactly causes the failure?

The relative static and pitot pressures are irrelevant, as only the TE
port is connected to a pneumatic vario, with the capacity on the other
side. Best theory I've heard (from the current owner of Sage ;^) is
that the capacity contains relatively warm air when one puts the glider
away in the early evening, which then cools at night lowering the
pressure (and tightening up the tape seal). Removing the tape in the
morning can cause a sudden influx of high pressure air, which results in
a high enough "sink" rate to bend/break delicate parts inside the vario...

Marc

On May 23, 10:29*pm, Marc Ramsey wrote:
Darryl Ramm wrote:
Lets make it a concise short thread then. You got me - I'm not sure
how this would hurt a vane style (winter) vario or even a Sage vario
since all ports of the triple probe mechanism will be at the same
pressure and may all be increasing or decreasing in pressure (but at
the same pressure) due to temperature changes or altitude (towing
glider in the trailer). So what exactly causes the failure?

The relative static and pitot pressures are irrelevant, as only the TE
port is connected to a pneumatic vario, with the capacity on the other
side. *Best theory I've heard (from the current owner of Sage ;^) is
that the capacity contains relatively warm air when one puts the glider
away in the early evening, which then cools at night lowering the
pressure (and tightening up the tape seal). *Removing the tape in the
morning can cause a sudden influx of high pressure air, which results in
a high enough "sink" rate to bend/break delicate parts inside the vario...

Marc

Oh doh, sounds good to me. I guess I'm lucky and/or just have the
elcheapo type mechanical varios. So good point.

Darryl