Pitot static test

[Treekiwi]

I've searched the forums and think I know the answer to this but the tech doing my pitot static test has different thoughts.
He says the leak down test has to be done at 10,000 feet, but everything I read, both here and other references, says 1000' above field elevation.
Can the avionics gurus chime in?
Thanks
Stephen

 

[Avionics Systems]

You are correct, 1000 feet above ambient, maximum leak allowed is 100 fpm. Realistically if we have an airplane here leaking close to 100 fpm we are going to look and find out why.

 

[RVDan]

Ref part 23, section 23.1325 for non pressurized airplanes the pressure differential requirement is 1000 ft.

 

[Treekiwi]

You are correct, 1000 feet above ambient, maximum leak allowed is 100 fpm. Realistically if we have an airplane here leaking close to 100 fpm we are going to look and find out why.

Thanks so much for this info. After tracking down leaks in my system, I passed the test with flying colors, even though the tech insisted on doing it at 10,000'
I'm also confused about the requirement in Part 43 Appendix E that requires an altimeter case leak test at 18,000'.
How does that fit into the whole picture, and does it only apply to analog altimeters, or does it include EFIS's etc?
Cheers, trying to learn the ins and outs of all this.
Stephen

 

[Walt]

An AHRS does not have a “case” with the associated baro knob and case O rings, so it’s not applicable.

 

[Treekiwi]

An AHRS does not have a “case” with the associated baro knob and case O rings, so it’s not applicable.

Thanks!
So is the case tested usually performed at every pitot/static test (24 months)?

 

[Walt]

Thanks!
So is the case tested usually performed at every pitot/static test (24 months)?

On an analog altimeter yes. Generally remove analog altimeters and test on the bench.

 

[blaplante]

There's a lot of local interpretation on this. I agree with Walt's understanding, but I know of more than one shop that insists on pulling the entire system up to over 10,000' (non-pressurized aircraft). On an IFR cert., if that makes a difference.

 

[Walt]

There's a lot of local interpretation on this. I agree with Walt's understanding, but I know of more than one shop that insists on pulling the entire system up to over 10,000' (non-pressurized aircraft). On an IFR cert., if that makes a difference.

With glass/ahrs systems you obviously can't remove stuff and run it on the bench, so I do bring the system up to 20K (pitot/static/aoa) to check altimeter accuracy, no other way to do it, as long as my test box can cope with the system leaks there's no issue.

If the system leaks too much to do that, then the only alternative is connect directly to the ahrs, which I have done many times.

 

[Treekiwi]

With glass/ahrs systems you obviously can't remove stuff and run it on the bench, so I do bring the system up to 20K (pitot/static/aoa) to check altimeter accuracy, no other way to do it, as long as my test box can cope with the system leaks there's no issue.

If the system leaks too much to do that, then the only alternative is connect directly to the ahrs, which I have done many times.

It's interesting, because when the tech performed the tests up to 20,000, all my altimeters were within 15-20', but then it failed the leak test at 10,000'.
Everything passed once I sealed some leaks in the system, so it's kind of academic at this point, but I did want to understand more about how this all works. Thanks for your responses.
Stephen

 

[Brantel]

To add to Walt’s post…. If you take a Garmin AHRS to high altitudes without also taking the AOA port and the pitot port there with you, you will most likely permanently damage the differential pressure transmitters in the AHRS.

 

[BobTurner]

It's interesting, because when the tech performed the tests up to 20,000, all my altimeters were within 15-20', but then it failed the leak test at 10,000'.
Everything passed once I sealed some leaks in the system, so it's kind of academic at this point, but I did want to understand more about how this all works. Thanks for your responses.
Stephen

With glass/ahrs systems you obviously can't remove stuff and run it on the bench, so I do bring the system up to 20K (pitot/static/aoa) to check altimeter accuracy, no other way to do it, as long as my test box can cope with the system leaks there's no issue.

If the system leaks too much to do that, then the only alternative is connect directly to the ahrs, which I have done many times.

As Walt says above, as long as the vacuum pump in his test rig can pump faster than any leaks, he can determine altimeter accuracy.
For the leak test he turns the pump off, and watches the altitude drift down as air leaks into the system (ideally zero, but some leakage is allowed).