While you're pondering the logic of the regs insisting on VFR
transponder/altimeter data correspondance after installation or
maintenance, consider the implications of 91.411(c). This IFR
requirement considers TSOed altimeters and encoders to be tested and
inspected as of the date of their manufacture. The way I read this,
you don't have to perform the checks in 43 Appendix E on intial IFR
transponder installation, you just have to do them within 24 months
after their manufacturing date.

-John

On May 3, 5:22 pm, Eric Greenwell wrote:
Now I'm puzzled that the regs insist on IFR quality data correspondence
for the initial installation, but with no checks after that as long as
you don't change anything.

--
Eric Greenwell - Washington State, USA