Best replacement for old Cessna navcom?

How do you feel about having only one ILS (remember it's a nice toasty old
one at that... No known problems but more likely to fail than a nice new
box)

Best,
-cwk.

"Newps" wrote in message
news:xV_pb.81587$ao4.245079@attbi_s51...


Tom S. wrote:


But is that DME substitute legal for approaches/departures marked "DME
Required"?

Yes.

What about if the GPS system is having a bad hair day?

What if the VOR is out of service?

"Colin Kingsbury" wrote in message
news
Because a topic like this never gets too old

1979 172 with original Cessna (RT-385 IIRC?) radios, the NAV frq display
on
the #1 box failed and the partners now finally agree it's not worth
repairing.

I've got a 78 with the same radio. Three years ago the display driver died
(also had a few segments burned out). The total tab including changing a
few electrolytic caps that were drying out (resulting in low audio volume)
was about $175. The radio operates very well now. This was the second time
in over 20 years it was in the shop....not great...but not too bad either.
So is it really not worth repairing?

Of course a new panel would be very nice....

John Severyn
LVK
N24495

Because a topic like this never gets too old

1979 172 with original Cessna (RT-385 IIRC?) radios, the NAV frq display on
the #1 box failed and the partners now finally agree it's not worth
repairing.

I'm contemplating two options:

1. Replace with a slide-in replacement like the TKM series, which will get
me a new box and standby freqs (woo-hoo!) Anybody here have those, or
suggest others? Advantage here is v. low cost to install versus something
like a KX-155 upgrade which would require rewiring, etc.

2. Replace with an IFR GPS/Com. This addresses ADF/DME, but costs us one
VOR. I don't think people will go for buying a second nav/com as well so it
needs to be a one-box upgrade.

Current stack has 2x Nav/Com, 1x ADF, 1x Mode C, Audio panel w/ marker
beacon, and an M1 Loran, all original equipment. The audio panel's getting
fussy and the ADF won't lock on to the lower-powered beacons until you're on
top of them. If it was up to me I'd yank it all but I've got 4 other guys
who fly less and almost never fly IFR so they're less picky.

Best,

Hi,

I had a similar dilemma with an upgrade to factory original '76
Cardinal (with a "NavPack II", no less!) I think this comes down to
what you are trying to accomplish: if you simply want to rectify a
current problem, you have two choices: get another RT-385 ($500-700,
may not be the end of it, though) or an MX-385 ($1500 but will likely
last a while). If you are using the current situation as an excuse to
gain more capability (nothing wrong with that !), then you have to go
to an IFR GPS, KX-155's won't let you do an approach or go direct any
more than the old ARC radio. Now you are talking some serious dough,
however: your -385 may channel a remote glideslope, so that will have
to be re-done or moved around to the #2 spot. Otherwise, your "one
box" is basically starting to look like a Garmin 430, a $10K+ venture.
Legal hair splitting aside, in practical terms, the GPS does fully
replace ADF/DME, but you definitely want to keep a VHF glideslope for
now, the GPS won't get you as low when it counts.

I ended up replacing both RT-328T's with newish MX-300's I bought on
ebay, net cost after selling the cores was about $1100 for both units,
but this was perhaps an unusually good deal. If I had the $$$ I would
go the GPS/Com route, but *I* honestly don't need the capability right
now, I don't fly regularly anywhere that's only served by a GPS
approach, and cross-country flight around here usually means terrain
where the airways represent the only sane route in IMC anyway. But if
you fly over to grandma's every Sunday and the airport only has a GPS
approach, the cost/benefit equation changes significantly, no doubt
about it.

Martin

"Newps" wrote in message
news:xV_pb.81587$ao4.245079@attbi_s51...


Tom S. wrote:


But is that DME substitute legal for approaches/departures marked "DME
Required"?

Yes.

What about if the GPS system is having a bad hair day?

What if the VOR is out of service?

Kinda hard to require a DME, then, wouldn't ya think?

Colin Kingsbury wrote:

How do you feel about having only one ILS (remember it's a nice toasty old
one at that... No known problems but more likely to fail than a nice new
box)

The vast majority of GA planes only have one ILS now.

"Colin Kingsbury" wrote in message link.net...

1979 172 with original Cessna (RT-385 IIRC?) radios, the NAV frq display on
the #1 box failed and the partners now finally agree it's not worth
repairing.

1. Replace with a slide-in replacement like the TKM series, which will get
me a new box and standby freqs (woo-hoo!)

No question this would be the cheapest alternative.

I have a TKM 170B (slide-in replacement). I know others who have
slide-in replacements for the Cessna TKM radios.

Generally we're happy with it. It is lower-power than our KX170B;
ATC will lose our tranmissions on the MX at distances where we're
fine on the KX. The nav radio is fine.

Caveat: our other nav/com is the same wiring harness. Thus we were
able to swap slots and determine that the antenna and wiring harness
were not problematic. If you can do this, fine. If you can't, I
would try to get your avionics guy or a fellow Cessna owner to loan
you a radio and test the wiring/antenna splitter etc.

I know people who say the TKM radios are junk, and I think actually
their problem is elsewhere in the system. Don't overlook the issue
that you ARE reusing the wiring/antenna etc.

2. Replace with an IFR GPS/Com. This addresses ADF/DME, but costs us one
VOR. I don't think people will go for buying a second nav/com as well so it
needs to be a one-box upgrade.

There's no question that this would get you the most increase in
capability. Depending upon where you fly, an approach certified
IFR GPS is a real boon. And, if your ADF is flaky, this might even
be the most cost-effective alternative, better than repairing/replacing
the ADF AND the nav.

The GPS can serve as a 2nd VOR just fine -- it will give you more
precise identification of intersections as well as a legal substitute
for DME and NDB.

The flaky audio panel might be a wiring issue. Again, if you can
find someone w/ the same make and model, simplest thing to do is
to swap it. While yours is out, just look it over with a multitester
for signs of bad connections etc. Hit the pins with tuner cleaner
and reseat a few times.

A little TLC definately improves the performance of old avionics.

Cheers,
Sydney

"Colin Kingsbury" wrote in message link.net...
From what I can tell a GNS-430 (even used) installed will cost around double
what a GNC-250xl or UPSAT setup would go for.

One thing to consider with UPSAT is how the AFM is written.

The UPSAT line reads "the user must verify that approach data is current"
The Garmins AFAIK read "the database must be current"
Pricy little distinction there.

The only thing I don't like about going this route is losing the second LOC.

The IFR GPS isn't a bad backup for the loc in practice. Slap "nrst"
and choose the LOM or intersection. Input the FAC. Make sure your CDI
is set to the most sensitive setting. It's not quite as sensitive as
the LOC becomes near DH but it's a good backup.

Cheers,
Sydney

In article wW_pb.79471$275.229001@attbi_s53, Newps
writes:

Not that much. You'll be able to unload the ADF and Loran to people
stuck in the 70's on ebay without much problem.


My shop at G Force (KCAK) gave me a good trade in and saved me the trouble of
selling them.

Chuck

Snowbird wrote:
: I know people who say the TKM radios are junk, and I think actually
: their problem is elsewhere in the system. Don't overlook the issue
: that you ARE reusing the wiring/antenna etc.

Having seen the inside of one, I can say that they are built more
like personal computers than middle-aged avionics (like a KX-170B). The
old King units are solid, well-potted inside, and built with bullet-proof
guts. Their breakage problems are typically dried up caps, cold solder
joints from thermal cycles, and physical wearing of switches, etc. The
TKM radios have standard ribbon cables, connectors, DIP chips (often
socketed)... all of which makes them cheap to build. In a high-vibration
environment, however, that can potentially cause more problems with
fatigue, chafing, and oxidizing of sockets, in addition to the problems
with the old brick-sh!thouse radios.

That said, I think you're right that most people with bad
experiences with slide-in replacements had bad wiring to begin with.
That's the most likely culprit of most avionics problems.

-Cory

--
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* - learn what you don't know, *
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I know people who say the TKM radios are junk, and I think actually
their problem is elsewhere in the system. Don't overlook the issue
that you ARE reusing the wiring/antenna etc.

Avionics shops also regularly badmouth TKM, for obvious reasons...