Splitting pitot line to 2 gauges

[ken nougaret]

Hello everyone. I just installed an AV-30 in my 7. I put a tee on the pitot tube and out to the av30 and my old analog airspeed indicator. At first the old airspeed gauge bounced a little, maybe trying to show 10mph. I replaced the tee with a new and different make and it read 35mph. Still nothing on the av30 but it doesn't start reading till 40. I removed the tee and hooked pitot directly to the av30 and it worked fine. I also had to split my static line. I used the same model of tee that I had installed at first. Altitude readings are perfect. Whats going on with my pitot? I should be able to split that, right?

[PapuaPilot]

Yes, all you should need to do is split the pitot and static lines and Y them into both instuments.

Without seeing the A/S indicator and plumbing it is hard to know what might be wrong. Hopefully you didn't over pressurize the line and damage the unit.

[ken nougaret]

No. Like I said the av30 work when you hook direct, and leave the other gauge disconnected.

[Delta Whisky]

Ken - from my reading of your issue I suspect a leak at the ASI fitting or internally. When you said the ASI read around 35, was that while you were pressuring the line or in flight?

[ken nougaret]

Hi Darrel. That reading was in-flight. Both instruments work fine when individually hooked to the pitot tube. So the problem has to be a leaky tee fitting. I just find it odd that 2 different ones are leaking. A neighbor told me tonight to attach surgical tubing to the pitot tube and roll it up to increase the pressure. I'll try tomorrow.

[Delta Whisky]

Ken - I've use a syringe for the same purpose. Good luck and let us know what you find.

[avidflyer]

I have used a manometer to calibrate the ASI. It will also show you if you have a leak in the pitot line or fittings. Using a roll of 1/4" plastic tubing pushed onto the pitot tube, and having the other end blocked, and folding it up will increase the pressure by the small amounts of pressure needed. JImChuk

[ken nougaret]

Troubleshot the problem/leak down to the push-to-connect on the back of the old analog gauge. That, combined with the different tube coming out of my tee, they just didn't get along together. So I put a new straight threaded push-to-connect and no more leak down. However, the analog reads about 3 mph faster than the digital. Not a huge deal, but is a discrepancy like this common?

[Delta Whisky]

In my experience some difference is seen fairly frequently.

Is it a big deal? Well, maybe.

If you have a syringe, try running the pressure up slowly and see if the difference is the same, gets worse of if there is a cross over point somewhere between say 30 and 110. That and knowing your flying style will help with the answer.

[PapuaPilot]

Analog gauges can especially be inaccurate. The best way to have these tested is with a calibrated test box at an avionics shop.Glad you got your problem figured out.