Out-of-calibration transponder operation

Ray Andraka wrote:
in Class G airspace, ATC radar in most cases won't illuminate your
transponder, so it won't reply anyway, so as far as ATC is concerned it
probably doesn't matter if you have it on or not. However, TCAS
equipped aircraft will interrogate your transponder, so to be visible to
them you might want to keep it on mode3/A so that it doesn't report a
misleading altitude but does return a reply.

Well, not where I live. My airport is
under Sac Intl. class C and I'm less than
10 miles away from 2 class D airports.
Beal is about 25 miles north and class C.

The transponder lamp is blinking almost
continuously whenever the transponder is
on.

Jim Stewart wrote:

Ray Andraka wrote:

in Class G airspace, ATC radar in most cases won't illuminate your
transponder, so it won't reply anyway, so as far as ATC is concerned
it probably doesn't matter if you have it on or not. However, TCAS
equipped aircraft will interrogate your transponder, so to be visible
to them you might want to keep it on mode3/A so that it doesn't report
a misleading altitude but does return a reply.


Well, not where I live. My airport is
under Sac Intl. class C and I'm less than
10 miles away from 2 class D airports.
Beal is about 25 miles north and class C.

The transponder lamp is blinking almost
continuously whenever the transponder is
on.


OK, my bad. I was thinking of the larger areas of class G in the
mountains out west, but someone else here tells me there is radar
coverage over a significant part of that too. When I flew to Taos about
10 years back, I remember there being no radar coverage once you got
below the peaks, and I was going off that limited experience.

My point though was that if your transponder is working but not
squawking altitude correctly, leaving it on but in the Mode 3/A position
still has some benefit, even if you are outside of radar coverage.