[chazking]

Recently, I had the 24 month transponder & pitot/static test performed. All went well with the transponder.

After tightening static fittings, the static test (set @ 29.92 inHg & +1000 AFE) ended with 35' loss (vs 100') and was within tolerance. But, repeatedly the pressure (in the pitot) would not hold (probe drain hole was covered).

Having reviewed VAF & other sites as well as contacting avionics shops, there is varying opinion on the pitot side of this test. One shop says for the IFR test, only the static is required by regulation. And, there appears to be some gray in the regs (which I've read several times!) .

While holding pressure on the pitot side (for 1 min) was the stated purpose, how does that relate to the static test?

The IFR test was run two years ago without issue. Nothing has changed with the pitot / static system over the past two years.

I'm looking for direction on the pitot side of this test. Is it required?

Enquiring minds want to know.

 

[Walt]

There is no requirement in the CFR's to check the pitot system on an IFR check and there are no leak "limits".
Pressurized aircraft will specify a limit in the maintenance manual but again no limit in the CFR's on pitot systems.
Per 43-13 (no MM specs available) standard leak rate for pitot systems should not exceed 10 knots in 1 min with system pressurized to 150 knots but 43-13 is an advisory circular not a reg.

 

[bruceg]

Pitot Leak

The avionics shop I use did the check with all items installed and said they could not take the static system to 20,000 ft if there was a big pitot leak. He did try it but the test rig aborted the test.
If the pitot system was leaking when the test rig had the pitot and static at high altitude would the ASI be overdriven? Could this be a limitation of this particular test gear?
Anyway, he wanted to see a pitot leak of around 1 or 2 knots per minute at 100 knots before performing the test. He also mentioned that a pitot leak would affect static system pressure and the altimeter test since those pressures are present on opposite sides of the ASI diaphragm.

 

[Walt]

Like everything else there can be more than one way to skin a cat.

However, if the shop is just is just hooking up to the pitot-static system and checking everything together they can't perform the altimeter tests as called out in the regs which calls for an "altimeter" leak check at 18K feet (not too many static systems will have a leak rate of less than 100 ft/min at 18K which is the limit).

If you have analog instruments you HAVE to do the altimeter separately as there is a hysteresis test that calls for a 5K/per min descent test which most VS indicators won't like.

I do glass panels with my test equipment hooked directly to the air data box because the 18k leak test requirement must still be done.
I do all analog altimeters by removing them and running them (and encoder if you have one) on the bench. I find lots of altitude encoders out of limits and I suspect the reason is because many shop don't pull them which means you can't calibrate it.

Doing the job the way I do is both safer for your instruments and me (I can't afford to buy you new ones), it also eliminates the pitot system from the testing process. I could give you an IFR cert with a totally open pitot system, I don't usually even check the pitot system unless you ask for it as its not part of the IFR cert.

Now on a pressurized aircraft its a different story as you have to run both pitot and static systems to a much higher level for the static system leak check (depends on service ceiling) so this requires both systems to have leak rates within limits (MM limit for pitot).

 

[chazking]

Update - 08 Apr 14

Walt .. The shop that did the sign-off connected directly to the ports on the AFS5600. Every reading was within 20ft of spec. No prob with sign-off.

They were very experience with experimentals .. It took less than 2 hrs