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petehowell
10-06-2006, 11:48 PM
Hello,

I tested my Pitot static system tonight and found that my ADI Pilot will not hold Pitot or Static pressure. I was able to isolate the ADI so I know it is the guilty party. I seem to remember that might be the way it is designed.

2 questions

1) is it designed to leak?

2) will the other instruments play nice if it leaks?

szicree
10-07-2006, 12:20 AM
I've got a Trutrak ADI and couldn't get the static side to hold pressure. I contacted them and they said that I shouldn't connect my static port to the instrument and that it is designed with an internal "leak". Obviously, if it leaks, you can't have it in your static system cuz it will throw everything else off. I asked them why it even has a static port hookup and they said that was for pressurized aircraft and that the instrument is set up differently internally for those applications. I must admit this all sounds pretty lame to me still.

John_RV4
10-07-2006, 07:44 PM
Steve,
That's exactly what it says in the manual. You don't need to hook up anything unless it's pressurized.

I just got one and haven't flown with it yet but the instructions do make sense. It is it's on static port ( so to speak ).

I also got the internal GPS. I mounted the antenna on top of the roll bar temporarily. Would like to come up with a better under cowl mounting. Just have to come up with a good idea.

Later

John

szicree
10-07-2006, 10:18 PM
But wait... If it's its own static port, then what about the fact that pressure inside the cockpit may not accurately reflect that outside? Also, if you hook that thing up in a pressurized cabin, it won't be pressurized for long since the air will pass through the instrument and out the static port. Also, the instructions I got simply said that the static port hookup was optional. My unit was purchased a while back so maybe the documentation has been updated.

Jekyll
10-08-2006, 12:25 AM
Think about what it is measuring and reporting. It doesn't measure or report altitude or airspeed - just measures changes that its internal gizmos use to show you a representative gyro type presentation. As long as it can measure the change in static, be it external or internal, it will do its job. Of course, transients, such as opening or closing your vents may cause it to show a climb or descent for a short instance.

Jekyll

John_RV4
10-08-2006, 06:35 PM
Yes, it only has to measure changes.

Opening or closing the vents !! Never thought of that. I'll have to add that to my list of things to try with this unit.

I haven't come across mountain wave in some time but that's on the list of things to try (assuming I can find some).

Later

John

airguy
10-13-2006, 10:59 AM
Also, if you hook that thing up in a pressurized cabin, it won't be pressurized for long since the air will pass through the instrument and out the static port.

Not if it's a very low volume internal leakage. Any pressurized cabin will have a good number of "leaks" to atmosphere (including the dump valve), the pressurized air supply constantly flows in to keep the pressure at the desired level. You'd need to move a LOT of air out your static port to defeat a pressurization system (at least a healthy one).