Static Check

PaulR · #1 09-08-2011, 09:27 AM

Folks, I am in the process of tracking down a static leak before I rivet on the final skin. I'm using a combination of SafeAir and Stein "push to connect" fittings a tubes. Last evening I came to the conclusion that my 2" UMA Altimeter is the main culprit. I found one more leak that I believe was caused by a tube not cut square and it's not leaking now.

My Dynon holds very steady but the backup altimeter drops rather rapidly. My question is, is that normal? Shouldn't it hold as steady as the Dynon? It was brand new 2 years ago and only recently hooked up.

Also, what is the spec on the allowable leakdown?

Thanks

TCONROY · #2 09-08-2011, 09:59 AM

Neither altimeter should descend more than 10 feet in about 30 seconds. Sounds like you have a large leak. Start at the static port and work your way back, testing each fitting joint. Leaks can be a real bugar to find!

AltonD · #3 09-08-2011, 10:00 AM

100 ft per minute.
Paul, I am off until the 20th. I am going to SC this weekend, but other than that, I am availabe to help. Just let me know.

To test my static system before the IFR cert, I used a turkey injector with some surgical tubing. It wokred great.

I had two leaks: Air around the Safeair ports between the skin and the port. This was really a testing issue with the way they hook up the machine to test the system. The second leak was my pitot tube.

The third leak was my brain. I was trying to meet a 100ft per hour requirement instead of the per minute spec. When I finally went for the cert, I passed with flying colors, all the way to 22K ft.

http://www.vansairforce.com/communit...ad.php?t=69849

fl-mike · #4 09-08-2011, 10:03 AM

I found plastic NPT fittings (at the back of instruments) to be leak-makers.
Switched to brass and the leaks went away.

orchidman · #5 09-08-2011, 10:55 AM

Quote:

Originally Posted by PaulR

.... Last evening I came to the conclusion that my 2" UMA Altimeter is the main culprit. .....

I had to send my new 2" Altimeter back to them for repair. Once fixed, the system was tight.

PaulR · #6 09-08-2011, 12:17 PM

Thanks Al for the note. I'll email you in a minute.

I've checked everything individually from the static port through all the insturments. The ONLY leak is at the altimeter. It's a UMA that I bought new. Any suggestions on where to send it?

Oh yes, I've tried a straight brass connector to the hand vacuum pump I'm using to eliminate the possibilty that it was caused by the push to connect fitting.