What is this airline thingy?

[John DeRosa OHM Ω http://aviation.derosaweb.net]

Ever seen one of these? Pictures at; http://derosaweb.net/aviation/cambridge/filter. It seems to have a large ID at one end and a much small ID at the other end.

- What is its function?
- What airline does it go with?
- Which direction should it point?

Back Story: A friend (IA/A&P) was working on the airlines of a glider. From what I gather there is a Cambridge CVS-50 installed. There is also a Winter vario installed. He removed all the airlines from instruments before noticing this hard plastic component until it was too late. Now he is lost as to what to do with it.

Thanks, John OHM Ω

[Dave Nadler]

On Friday, October 11, 2019 at 11:01:09 AM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> Ever seen one of these? Pictures at; http://derosaweb.net/aviation/cambridge/filter. It seems to have a large ID at one end and a much small ID at the other end.
>
> - What is its function?
> - What airline does it go with?
> - Which direction should it point?
>
> Back Story: A friend (IA/A&P) was working on the airlines of a glider.
> From what I gather there is a Cambridge CVS-50 installed. There is also a
> Winter vario installed. He removed all the airlines from instruments
> before noticing this hard plastic component until it was too late.
> Now he is lost as to what to do with it.
>
> Thanks, John OHM Ω

Oh dear.
Always take pictures prior to removing/disassembling stuff.
I still have a polaroid box camera I used to use for this!
But in these modern times a phone camera is excellent.
Though useless unless one takes the photos, and puts prints
in the box with the parts...
End of sermon, you can genuflect now.

Anyway, you're looking at a calibrated leak for a netto system.
Works in either direction.
But, such things only work correctly at a single weight and
a particular density altitude.
And thus are rarely seen anymore...

See ya, Dave

[John DeRosa OHM Ω http://aviation.derosaweb.net]

On Friday, October 11, 2019 at 10:06:16 AM UTC-5, Dave Nadler wrote:
> On Friday, October 11, 2019 at 11:01:09 AM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > Ever seen one of these? Pictures at; http://derosaweb.net/aviation/cambridge/filter. It seems to have a large ID at one end and a much small ID at the other end.
> >
> > - What is its function?
> > - What airline does it go with?
> > - Which direction should it point?
> >
> > Back Story: A friend (IA/A&P) was working on the airlines of a glider.
> > From what I gather there is a Cambridge CVS-50 installed. There is also a
> > Winter vario installed. He removed all the airlines from instruments
> > before noticing this hard plastic component until it was too late.
> > Now he is lost as to what to do with it.
> >
> > Thanks, John OHM Ω
>
> Oh dear.
> Always take pictures prior to removing/disassembling stuff.
> I still have a polaroid box camera I used to use for this!
> But in these modern times a phone camera is excellent.
> Though useless unless one takes the photos, and puts prints
> in the box with the parts...
> End of sermon, you can genuflect now.
>
> Anyway, you're looking at a calibrated leak for a netto system.
> Works in either direction.
> But, such things only work correctly at a single weight and
> a particular density altitude.
> And thus are rarely seen anymore...
>
> See ya, Dave

Pictures?? *I* have sworn on a stack of FAR/AIMs to take a boat load of pictures, only removing one tube at a time and carefully labeling where it went to/from. See my genuflection in http://aviation.derosaweb.net/presentations/#airlines. It is another poor soul I am trying to save from oblivion!

So assuming (!) that this will be the same instruments/glider/pilot would there be any value in replacing the netto "calibrated leak"? If so how would it be plumbed?

PS - I got a response from Gary Kammerer who said it was a "restrictor" and pointed me to a 2012 article from Dave Ellis "Variometer pneumatics – probes, tubing, restrictors, etc." that seems to point to the restrictor not being needed.

Thanks, John

[[email protected]]

I remember back in my m-nav, or was it the rico vacs, anyway using cigarette filters stuffed into the te lines to control gusts. took some testing to get it right on how dense to pack it. now I get three choices on the SN10 :)

CH

[Dan Marotta]

And you don't need to smoke any more to have filters available! :-P

On 10/11/2019 10:33 AM, wrote:
> I remember back in my m-nav, or was it the rico vacs, anyway using cigarette filters stuffed into the te lines to control gusts. took some testing to get it right on how dense to pack it. now I get three choices on the SN10 :)
>
> CH

--
Dan, 5J

[Dave Nadler]

On Friday, October 11, 2019 at 11:32:14 AM UTC-4, John DeRosa OHM Ω
> PS - I got a response from Gary Kammerer who said it was a "restrictor" and
> pointed me to a 2012 article from Dave Ellis "Variometer pneumatics – probes,
> tubing, restrictors, etc." that seems to point to the restrictor not being
> needed.

It certainly could be a restrictor - depends on the ID of the tube.
The length makes me guess its a netto leak.

[Tango Eight]

On Friday, October 11, 2019 at 11:32:14 AM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> On Friday, October 11, 2019 at 10:06:16 AM UTC-5, Dave Nadler wrote:
> > On Friday, October 11, 2019 at 11:01:09 AM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
> > > Ever seen one of these? Pictures at; http://derosaweb.net/aviation/cambridge/filter. It seems to have a large ID at one end and a much small ID at the other end.
> > >
> > > - What is its function?
> > > - What airline does it go with?
> > > - Which direction should it point?
> > >
> > > Back Story: A friend (IA/A&P) was working on the airlines of a glider..
> > > From what I gather there is a Cambridge CVS-50 installed. There is also a
> > > Winter vario installed. He removed all the airlines from instruments
> > > before noticing this hard plastic component until it was too late.
> > > Now he is lost as to what to do with it.
> > >
> > > Thanks, John OHM Ω
> >
> > Oh dear.
> > Always take pictures prior to removing/disassembling stuff.
> > I still have a polaroid box camera I used to use for this!
> > But in these modern times a phone camera is excellent.
> > Though useless unless one takes the photos, and puts prints
> > in the box with the parts...
> > End of sermon, you can genuflect now.
> >
> > Anyway, you're looking at a calibrated leak for a netto system.
> > Works in either direction.
> > But, such things only work correctly at a single weight and
> > a particular density altitude.
> > And thus are rarely seen anymore...
> >
> > See ya, Dave
>
> Pictures?? *I* have sworn on a stack of FAR/AIMs to take a boat load of pictures, only removing one tube at a time and carefully labeling where it went to/from. See my genuflection in http://aviation.derosaweb.net/presentations/#airlines. It is another poor soul I am trying to save from oblivion!
>
> So assuming (!) that this will be the same instruments/glider/pilot would there be any value in replacing the netto "calibrated leak"? If so how would it be plumbed?
>
> PS - I got a response from Gary Kammerer who said it was a "restrictor" and pointed me to a 2012 article from Dave Ellis "Variometer pneumatics – probes, tubing, restrictors, etc." that seems to point to the restrictor not being needed.
>
> Thanks, John

I don't think it's a netto leak. I've made a few of those. IIRC the tube ended up about 3.5 - 4" long, 0.012" ID. I used on an original Schuemann Compensator (remember those?) when I found one that was still serviceable, about ten years ago, but you should be able to adapt to any capacity style vario. IIRC (and without thinking hard about it) if using a TE probe, you would connect the leak between static port and the flask, vario goes between flask and TE probe.

Side note: modern pressure transducer based electronic varios like to be on pneumatic circuits without leaks, without large capacities and without any flows to speak of. Sharing a TE probe with one (and only one) mechanical vario may be done with reduced performance of the electronic vario. Sharing static with any mechanical instrument generally goes bad, don't do it. Sharing the pitot with one ASI can be done in a pinch, it is the least critical of the three.

best,
Evan Ludeman

[Dave Nadler]

On Friday, October 11, 2019 at 2:07:11 PM UTC-4, Tango Eight wrote:
> I don't think it's a netto leak. I've made a few of those.
> IIRC the tube ended up about 3.5 - 4" long, 0.012" ID.

I think you're right, trying to recall last time I saw one decades ago...
Don't know why a restrictor would be that long though.

> Side note: modern pressure transducer based electronic varios like to be
> on pneumatic circuits without leaks, without large capacities and without
> any flows to speak of. Sharing a TE probe with one (and only one)
> mechanical vario may be done with reduced performance of the electronic
> vario. Sharing static with any mechanical instrument generally goes bad,
> don't do it. Sharing the pitot with one ASI can be done in a pinch,
> it is the least critical of the three.

Any mechanicals on pitot, static or TE will definitely upset the SN10C...

[[email protected]]

Regarding the problems arising from sharing pitot, static, and TE across mechanical and transducer-based instruments:

I can see why the flow generated by anything using a capacity would be large enough to cause trouble. My gut feeling is that flow into or out of an altimeter or a mechanical ASI would be too small to matter.

If these instruments are impactful, what’s a workaround for a situation where finding truly separate pitot and static sources for the mechanical instruments is impractical? I’ve seen experimental gliders with digital altimeters, but I suspect a TSO’d option would be hard to come by, and I don’t think I’ve ever seen a (modern) sailplane without a mechanical ASI.

Would T’ing off static and pitot lines somewhat further than the traditional 6 inches from the instruments do enough to mitigate the effects?

Genuinely curious about this.

Neiman

[Tango Eight]

On Saturday, October 12, 2019 at 10:18:14 PM UTC-4, wrote:
> Regarding the problems arising from sharing pitot, static, and TE across mechanical and transducer-based instruments:
>
> I can see why the flow generated by anything using a capacity would be large enough to cause trouble. My gut feeling is that flow into or out of an altimeter or a mechanical ASI would be too small to matter.
>
> If these instruments are impactful, what’s a workaround for a situation where finding truly separate pitot and static sources for the mechanical instruments is impractical? I’ve seen experimental gliders with digital altimeters, but I suspect a TSO’d option would be hard to come by, and I don’t think I’ve ever seen a (modern) sailplane without a mechanical ASI.
>
> Would T’ing off static and pitot lines somewhat further than the traditional 6 inches from the instruments do enough to mitigate the effects?
>
> Genuinely curious about this.
>
> Neiman

If you want good instrumentation, it starts with good sources. Fin mount triple probe is the reliable standard for vario sources. Use the nose pitot and side statics for basic instruments (as usually specified by the manufacturer).

T8

[[email protected]]

It looks like a flow restrictor that was placed in the total energy line to slowdown a nervous needle on mechanical vario’s like the Schumann , back when we didn’t have good TE probes.
JJ

[AS]

On Sunday, October 13, 2019 at 10:52:21 AM UTC-4, wrote:
> It looks like a flow restrictor that was placed in the total energy line to slowdown a nervous needle on mechanical vario’s like the Schumann , back when we didn’t have good TE probes.
> JJ

It does! When I was a kid, we made these flow restrictors ourselves by heating laboratory glass tubes and then drawing them apart while blowing air through it to keep it from closing off. Out of ten trials, we would get maybe one or two good ones, which we places into slightly larger tubes and siliconed them in to keep them from breaking. Eventually, we would get decent TE compensation for our club gliders.

Uli
'AS'