Prandtl multi probe receptacle used for TE only?

I have a Prandtl type receptacle in the fin of my ASW27. The previous owner converted to to TE probe only, by tying off the static and pitot lines behind the panel. Anything wrong with this set-up? I guess there would be more potential for leaks, at a minimum. will the extra volume of air connected in the unused tubes create any adverse effects on the TE line? I get my static from the ports on the boom about 2/3 back.

Thanks for any input.

Matt

Hi Matt!

On Wednesday, February 14, 2018 at 6:03:47 PM UTC-5, Matt Herron Jr. wrote:
I have a Prandtl type receptacle in the fin of my ASW27.
The previous owner converted to to TE probe only, by tying off the static
and pitot lines behind the panel. Anything wrong with this set-up?
I get my static from the ports on the boom about 2/3 back.

You mean a 3-way probe, right?
The probe pitot and static are better than fuselage ports (though pitot
is easily wiped out by a bug). If your instrumentation is working OK with
fuselage ports, why mess with it?

I guess there would be more potential for leaks, at a minimum.

Nope.

will the extra volume of air connected in the unused tubes create
any adverse effects on the TE line?

No, they are not connected in any way.


See ya, Dave

On Wednesday, February 14, 2018 at 3:44:59 PM UTC-8, Dave Nadler wrote:
Hi Matt!

On Wednesday, February 14, 2018 at 6:03:47 PM UTC-5, Matt Herron Jr. wrote:
I have a Prandtl type receptacle in the fin of my ASW27.
The previous owner converted to to TE probe only, by tying off the static
and pitot lines behind the panel. Anything wrong with this set-up?
I get my static from the ports on the boom about 2/3 back.

You mean a 3-way probe, right?
The probe pitot and static are better than fuselage ports (though pitot
is easily wiped out by a bug). If your instrumentation is working OK with
fuselage ports, why mess with it?

I guess there would be more potential for leaks, at a minimum.

Nope.

will the extra volume of air connected in the unused tubes create
any adverse effects on the TE line?

No, they are not connected in any way.


See ya, Dave

The three circuits are not supposed to be connected, but if there is a bad O-ring, all bets are off.
In a perfect world, your system as plumbed will work fine. If the mod was done due to crosstalk, and there is a leak in the plugged static or pitot lines, it will be erratic.
After the lines were disconnected and plugged, there's a chance nobody has leak checked them.
They're a pain to replace. I have a spare fitting for ASW27/28/29 at home, hope to never need it. Fortunately my leak was found to be two things, a bad probe and a hidden connector in the back of the panel, which Rex found instead of replacing the fitting.
Jim

On Wednesday, February 14, 2018 at 3:57:27 PM UTC-8, JS wrote:
On Wednesday, February 14, 2018 at 3:44:59 PM UTC-8, Dave Nadler wrote:
Hi Matt!

On Wednesday, February 14, 2018 at 6:03:47 PM UTC-5, Matt Herron Jr. wrote:
I have a Prandtl type receptacle in the fin of my ASW27.
The previous owner converted to to TE probe only, by tying off the static
and pitot lines behind the panel. Anything wrong with this set-up?
I get my static from the ports on the boom about 2/3 back.

You mean a 3-way probe, right?
The probe pitot and static are better than fuselage ports (though pitot
is easily wiped out by a bug). If your instrumentation is working OK with
fuselage ports, why mess with it?

I guess there would be more potential for leaks, at a minimum.

Nope.

will the extra volume of air connected in the unused tubes create
any adverse effects on the TE line?

No, they are not connected in any way.


See ya, Dave

The three circuits are not supposed to be connected, but if there is a bad O-ring, all bets are off.
In a perfect world, your system as plumbed will work fine. If the mod was done due to crosstalk, and there is a leak in the plugged static or pitot lines, it will be erratic.
After the lines were disconnected and plugged, there's a chance nobody has leak checked them.
They're a pain to replace. I have a spare fitting for ASW27/28/29 at home, hope to never need it. Fortunately my leak was found to be two things, a bad probe and a hidden connector in the back of the panel, which Rex found instead of replacing the fitting.
Jim

I agree in normal use the three lines are not connected. However, if you just insert a TE probe into the multipart receptacle then all three ports share the same flow because the TE probe doesn't go deep enough and is not stepped like the Prandtl probe.

On Wednesday, February 14, 2018 at 6:57:27 PM UTC-5, JS wrote:
They're a pain to replace.

Yup, IMHO a huge design blunder to put the O-rings in the socket
instead of on the probe. I once asked SH how to replace the O-rings,
and they said they have absolutely no idea ;-(

How to change the internal O-rings is all explained in the service section of the ESA Systems web page. That's not to say it is easy - or even possible in the case of ring 3 without removing the socket which means cutting open the fin.

The probes and sockets are produced by esa-systems in Berlin. There's an instruction on how to replace the O-rings on their website: https://www.esa-systems.com/en/suppo...i-change-them/

Now tell me again...
Why aren't the O rings on the probe?

Must be an oversupply of engineers needing to design something like this O ring insertion tool.

torstai 15. helmikuuta 2018 1.03.47 UTC+2 Matt Herron Jr. kirjoitti:
I have a Prandtl type receptacle in the fin of my ASW27. The previous owner converted to to TE probe only, by tying off the static and pitot lines behind the panel. Anything wrong with this set-up? I guess there would be more potential for leaks, at a minimum. will the extra volume of air connected in the unused tubes create any adverse effects on the TE line? I get my static from the ports on the boom about 2/3 back.

Thanks for any input.

Matt

Volume of triple pneumatic tube from tail to panel might be close to half of variometer flask volume, so answer is "maybe" even in theoretical world. But there is too many variables in pitot-static system to give you systematic answer.