Reading FAR 91.411 Altimeter System & Altitude Recording Equip. Tests & Inspections (concerning IFR operations)

[mike20papa]

So .. the 24 month periodic testing & inspecting is stated in paragraph 1 -

(1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;

Then .. in paragraph 3 (c) it says - 

Altimeter and altitude reporting equipment approved under Technical Standard Orders are considered to be tested and inspected as of the date of their manufacture. 

So any opinion on this - what appears to be an exclusionary statement to the 24 mo. testing in 3 (c)?

[Bunti]

My understanding is for example about the altimeter: You can go to a company (usually an avionics shop) who is able and allowed to do the altimeter test up to a specified maximum operation altitude. Or, you can buy a new or overhauled altimeter. If you buy a new altimeter, the static system still needs to be checked because it was opened during the replacement of the altimeter. But there is no need to test the altimeter. The altimeter test is good for 2 years after the time of manufacture.  

When I bought my overhauled altimeter, it came with a brand new test certificate. 

[EricJ]

Another way to look at that is that if you put in a "new" altimeter that's been sitting on a shelf for a year, you'll need another cert within at least a year of installation.   The manufacture date of the altimeter drives, not the installation date.

 

[N201MKTurbo]

1 hour ago, mike20papa said:

So .. the 24 month periodic testing & inspecting is stated in paragraph 1 -

(1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;

Then .. in paragraph 3 (c) it says - 

Altimeter and altitude reporting equipment approved under Technical Standard Orders are considered to be tested and inspected as of the date of their manufacture. 

So any opinion on this - what appears to be an exclusionary statement to the 24 mo. testing in 3 (c)?

If you are thinking that a TSO instrument is exempt from inspection, you are mistaken. All this says is that it is considered inspected when it is manufactured. In reality it is meaningless because the reg says the system must be inspected. So when you put it in a plane it becomes part of that system. Most of the failures found during the inspections are system related. loose and leaking fittings mostly.

[Bunti]

My understanding of the regs is that you have to do a leak test of the static system when you put in a new altimeter. The 24 months altimeter calibration  and test up to max. altitude has not to be done until 24 months since production or 24 months since calibration / test at the bench of the manufacturer / overhauler have been elapsed.

But this discussion leads to no real value. In my opinion the whole system including all altimeters should be checked and recalibrated at the same time to make sure they are all good for 24 months. It does not make sense that 1 altimeter is due earlier than the other. The only benefit from the regulation is, if your altimeter is broken and the shop replaces the altimeter with a new or overhauled one outside of the normal static/altimeter 24 months check interval, they only need to do a leak test of the system and the new altimeter needs first time rechecked after 24 months since production or overhaul/certification have elapsed. Some shops can replace an altimeter and leak check the system. But they cannot do the full 24 months test / calibration due to lack of certified and calibrated testing equipment.

So, for example, if your static / altimeter test is still good for another year and your altimeter fails, it would be a wise idea to replace it by an altimeter which has a minimum remaining time of one year until it needs to be tested again. If it has only half a year remaining, it makes sense to do the complete system and all altimeter test at the install of the new one or wait half a year and do it then.  If the installer has the certified equipment to do a full test of the whole system, including the transponder and the encoder, I would do it at install.

 

 

[MB65E]

I was recently asked by a fed for not only the 91.411/.413 but also 91.217! 
Seems they are checking for .217 now as well. 
-Matt