Pitot static cert voided after avionics mods?

[MB65E]

Ahh, I Didn’t think so!

-Matt

[Shadrach]

14 hours ago, 0TreeLemur said:

They agreed on the ground with the same altimeter setting.  They agreed in flight with or without the alternate static source on.   Opening the alternate static source caused a little change, but less than the width of the 100' needle.  I was surprised.  The panel-mounted altimeter passed IFR cert. in May.

In my experience the difference in altitude indication between static and Alt (cabin) air is about 20’...

 

[FlyingDude]

2 hours ago, Shadrach said:

the difference in altitude indication between static and Alt (cabin) air is about 20’...

With the vents open or closed?

[Aerodon]

Seems like this might help people understand the issues:

1) A slow leak in the pitot system is not going to do much, the air in the pitot tube will constantly replace the leaked air.

2) In a non pressurized plane a static leak will affect the VSI, Altimeter and ASI.  If the leak is in the cockpit, the error will probably only be about 20' as described above.  If the leak is in the wing, maybe more?

3) Installing a G5 - you are messing with both pitot and static.  First test is to see if the static system is leakproof.  Second test is to see if the altitude on the G5 matches the other latitudes in your system, typically the altimeter and the encoder.  And then sometimes the autopilot has its own static source.  And the altitude capture might have another one.  This last one caught me out, I had a KFC autopilot that would want to capture 300 feet above the selected altitude.  I eventually worked out the transponder altitude was on an encoder.  The altimeter altitude matched this, but the altimeter 'grey code' output does not match the needles.  

Aerodon

 

 

 

 

[Bob Weber]

I was taught decades ago that you can plan on around 50' of static pressure difference between the cabin and the ambient pressure outside.

If that system holds 1000' of change for 1 minute I believe it will pass the test.