Transponder requirement confusion

Quick (hopefully) question to a confusing part of the FARs. With my new (to
me) solid-state transponder, I'm now willing to power it up for even local VFR
flights. Before, I would only turn on my KT-76 if I needed to (VFR advisories, IFR,
Class B/C operation) since I knew the cavity tube had a finite number of hours before
it died. Now that I read through the transponder requirement carefully, it appears
that that's not allowed. Google groups appear to contain previous usenet arguments
regarding this, but the answer's still not quite clear. In particular:

FAR 91.215(5)(c)
(c) Transponder-on operation. While in the airspace as specified in paragraph (b) of
this section or in all controlled airspace, each person operating an aircraft equipped
with an operable ATC transponder maintained in accordance with ??91.413 of this part
shall operate the transponder, including Mode C equipment if installed, and shall
reply on the appropriate code or as assigned by ATC.

"Controlled" airspace also includes Class E... so if you have one (and it's
within the 2-year test), you *have* to turn it on? ... but you aren't *required* to
have one?

If so, that's a very unclear requirement from most colloquial references on
equipment requirements...

Curious...
-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

In article ,
wrote:

Quick (hopefully) question to a confusing part of the FARs. With my new (to
me) solid-state transponder, I'm now willing to power it up for even local
VFR
flights. Before, I would only turn on my KT-76 if I needed to (VFR
advisories, IFR,
Class B/C operation) since I knew the cavity tube had a finite number of
hours before
it died. Now that I read through the transponder requirement carefully, it
appears
that that's not allowed. Google groups appear to contain previous usenet
arguments
regarding this, but the answer's still not quite clear. In particular:

FAR 91.215(5)(c)
(c) Transponder-on operation. While in the airspace as specified in paragraph
(b) of
this section or in all controlled airspace, each person operating an aircraft
equipped
with an operable ATC transponder maintained in accordance with ??91.413 of
this part
shall operate the transponder, including Mode C equipment if installed, and
shall
reply on the appropriate code or as assigned by ATC.

"Controlled" airspace also includes Class E... so if you have one (and it's
within the 2-year test), you *have* to turn it on? ... but you aren't
*required* to
have one?

If so, that's a very unclear requirement from most colloquial references on
equipment requirements...

The really dumb part of that requirement is that terminal radar doesn't
see below a given altitude at a given distance. Our local site (900 MSL)
cannot see aircraft with transponders on below (5000 MSL) at airports 40
south of the radar site. It gets really exciting when they are
controlling you into that airport on an instrument approach.

In article
,
john smith wrote:

The really dumb part of that requirement is that terminal radar doesn't
see below a given altitude at a given distance.

but a TCAS II equipped aircraft can see you.

--
Bob Noel
Looking for a sig the
lawyers will hate

"Bob Noel" wrote in message
...
but a TCAS II equipped aircraft can see you.

...which gives you plenty of reason to leave the thing on. In fact, it is
reason enough that significant numbers of glider people are installing some of
the new low-drain units, even though there is no FAA requirement.

Vaughn

: ...which gives you plenty of reason to leave the thing on. In fact, it is
: reason enough that significant numbers of glider people are installing some of
: the new low-drain units, even though there is no FAA requirement.

My big beef was just the finite lifespan of the old cavity tube units. As long as it's solid
state like my new unit, there's really no reason NOT to turn it on. Maybe I was just ultra-sensitive
to the cavity thing since I had to replace two of them with low power.

The other beef is how vague the FAR is.

-Cory


--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:

The other beef is how vague the FAR is.

What's vague. If you're in controlled airspace and you've got
a transponder, it's supposed to be on.

wrote in message
...
"Controlled" airspace also includes Class E... so if you have one (and
it's
within the 2-year test), you *have* to turn it on? ... but you aren't
*required* to
have one?


Yes, I don't have a transponder so I don't have to turn it on. I have gotten
requests to turn on my transponder which I reply 'Slant X-Ray'...

In article ,
Bob Noel wrote:

In article
,
john smith wrote:

The really dumb part of that requirement is that terminal radar doesn't
see below a given altitude at a given distance.

but a TCAS II equipped aircraft can see you.

Only if you have a Mode-S transponder.

john smith wrote:

but a TCAS II equipped aircraft can see you.

Only if you have a Mode-S transponder.

Nope, all they need is mode C.

wrote:
john smith wrote:

but a TCAS II equipped aircraft can see you.

Only if you have a Mode-S transponder.

Nope, all they need is mode C.

Actually, they don't even need mode C, now that I think about it.
You get different levels of service depending on what the target has.

If they've got Mode A you'll get an callout.
If they've got Mode C then you'll get an RA (climb / descend)
If they've got Mode S and they've also got TCAS, the two TCAS's
will boogie with each other to coordinate the RA.

So really mode S by itself does nothing for TCAS II unless you've
also got a TCAS as well.