chronically low vacuum indication

[GeorgeC]

I spent far too much time last night looking for o-ring NPT fittings, with hose barbs, in aluminum. Unobtainium, it seems.

 

[Dan Thomas]

I spent far too much time last night looking for o-ring NPT fittings, with hose barbs, in aluminum. Unobtainium, it seems.

Which is why I have sometimes seen NPT non-O-ring fittings with a short length of aluminum tubing on them, and the hose clamped to the tubing.

There are no NPT O-ring type fittings. The O-ring fittings use a straight non-tapered thread. NPT means National Pipe Taper.

What you need are these:




All from https://www.wicksaircraft.com/c/aircraft-automotive-fittings/aircraft-fittings/an-ms-fittings/

Aircraft Spruce would also have them. Various sizes. Stupidly expensive.

 

[GeorgeC]

Are clamps required on suction hoses? If so, can zipties be substituted?

 

[Bell206]

Are clamps required on suction hoses? If so, can zipties be substituted?

Clamps.

 

[GeorgeC]

I only saw one hose going to the gauge.

I only saw one hose because there was only one hose hooked up. I pulled the gauge off and one of the ports had some kind of horrible jb weld repair done to it. The other port was just missing entirely. Sigh.

You do not want to pull existing hose off. Cut it instead.

You are correct. Also, barbed nylon connectors are awful.

 

[GeorgeC]

So that others do not repeat my mistake:

"[Nylo-Seal] N Tubing is rated to 1000 lbs. and is excellent for instrument lines and other low pressure applications."

Sounds great. But wait, there's more! The NSR flavor tubing has an smaller bend radius, so it must be even better! And it's cheaper than aeroquip! Quick, buy some!

...except that it's 3/8 OD, not 3/8 ID, and it's much more rigid than aeroquip.

Womp womp.

 

[GeorgeC]

Got to watch that the controls don't foul the hoses, and with straight fittings the hoses might be in the way. They can snag the controls and make the flight way too exciting.

I replumbed the path from the left venturi-AI-filter today, being careful to check the yoke for interference.

The funny thing? The yoke banged into the original nylon elbows on the DG. I guess those will be coming out for now...



Next week, suction gauge.

 

[Dan Thomas]

The funny thing? The yoke banged into the original nylon elbows on the DG. I guess those will be coming out for now...

I wonder if the elevator control system is properly rigged. That can bring the yoke up against instruments like that. How far away from the firewall does it stop when pushed full forward?

 

[GeorgeC]

How far away from the firewall does it stop when pushed full forward?

I didn't bring a measuring tape, but it looked like a couple inches.

New gauge is in + gutted the plumbing to the right venturi. Should be able to replumb the rest next week and get it signed off.

 

[GeorgeC]

Back in the green at 5" of mercury.