Impressive amount of pitfalls you've discovered already. I'd say you've got
the right mindset to make this go. I did basically the same thing, although it was on
a certified aircraft (PA-28-180). I had to write up all of the approved data (AC43
for wire types, sizes, gauges, and install manuals consulted, etc) and get a field
approval through the FSDO. My mechanic helped with all the paperwork and approved the
installation. Comments below:

: 1) KX-175B 720 ch com,
: 2) KY-195B 720 ch com (essentially a com-com that fits a 170-175 tray,
: same pinouts - think of it as a mechanical flip-flop com)
: 3) A KLN-89B IFR GPS (terminal, enroute and non-precision approach capable)
: 4) KN-75 Glideslope Rec
: 5) AT-50A Transponder

: I have since acquired pinouts for all, and the install manuals for the
: 175 and the 89B.

You may need to get install manuals for some of them. Try to make friends by
ordering some components from avionics places... you may need to order connectors, or
pins or something.

: What I DONT have is education, training and textbooks appropriate for
: avionics technicians. I've got novice to above novice ability regarding
: this, but consider myself a quick learner and critical thinker.

: So.. things I want to check/verify:

: 1) The KX-175B TSO is still acceptable for use in the US, and uses 720
: channels. It does not contain a glideslope reciever nor a "converter".

True.

: 3) The 175B, by not having a converter, requires either an indicator
: that has an integral one, such as the KI 201,204,208,209 or 214... or
: requires an external converter such as the KN-72. The 208/9A series, I
: belive, has the converter but also can be driven by GPS. The GPS is
: otherwise incompatible with indicators that have the internal converter
: (except for the 208A and 209A).

I think I recall hearing that on the 208/209. You could also go with a 206
or the old KNI-520 for the GPS and get the external converter for it for the 175.

: 4) If paired with the KN-72, then the 175B can drive any of the other
: indicators, including mid continent, collins, stec, ARC and the
: applicable non-converter king products. The GPS can drive these
: indicators in a stand-alone setting. This is a key item for me that I am
: not sure of, as I am currently shopping for indicators, and the new cost
: of some of them can exceed what I've spent on panel ($1600) so far.

We got almost all of our stuff via ebay.

: 5) What is the name for the scheme that the KX-175B uses to drive the
: glideslope reciever - 10 or more wires that are each associated with a
: specific MHZ or KHZ range? I've seen 2x5 arinc, slip code and other
: terms used and havent specifically associated them with what they are
: supposed to mean.

: 6) What is name of the scheme that the KX 175B uses to drive a DME
: reciever, keeping in mind the same comments as above. This appears to
: be different that the glideslope wiring scheme, with 8 wires that appear
: to be some sort of parralel binary scheme.

Don't know about these specifics, but I would think that there's only one
set... I don't know if there are isolation issues (diodes, current draw, etc) like
transponders/encoders can have.

: 9) How many folks out there who've added GPS's to their panel have "the
: works" done.. interface it to the altitude encoder, air data unit, your
: fuel manager or the OBS resolver on your CDI. I've flown behind many
: rental planes with King GPS in them, that had none of this done, but
: flew in ONE very nice A36 that came from the factory with the GPS
: integrated nicely into the stack. Folks that have done this interface,
: did you have interference with the xpnder that was also getting data
: from the encoder? Did you have to use diodes or a second encoder or
: leave it unconnected?

Our setup did not include an IFR-certified GPS... rather a VFR GPS/COM
(KLX-135). Since it wasn't that big of a deal, I wired up the altitude encoder for
the transponder to it as well. I did need to add the diodes. Also, some encoders
(Narco in particular) are bad about the low-voltage logic level. In my mechanic's
plane (I did the wiring to install his IFR GPS in his personal plane), the addition of
diodes caused the logic to be intermittent on the GPS. The additional voltage drop of
Si diodes was problematic... a logic '0' wasn't low enough to be a '0' all the time.
A different encoder and unusual diodes worked.

: 11) I started wiring both of the radio trays (175 and 195) for eventual
: upgrade to dual nav-com, glideslope and DME capability before I came to
: possess the GPS. How many out there have both DME and GPS, and use their
: DME regularly despite GPS being an acceptable substitute?

I've got a KNS-80 VOR/LOC/GS/DME/RNAV installed and I use it all the time. My
primary "Direct-To" instrument is the GPS, but I cross-check on the VOR and DME all
the time. Much quicker to dial up 116.8 on a DME than twirling through 'P-S-K' on a
friggin' GPS. I don't know if the additional utility gained out of a *pure* DME would
be worth the expense, weight, or complexity in channeling it up with the NAV, though.

: 12) Panel space considerations will likely rule out a panel mount DME if
: ever acquired, until or unless the 175 and 196 are replaced by slimline
: radios down the road. What is the appropriate designation for a King
: remote mount DME (and indicator) that would fit in this situation, and
: is the remote unit fairly light/compact or is it essentially a heavy
: transplant from a bizjet? (truth is, will likely not use it, but I want
: to keep the options and eyes open if it comes along).

Since it sounds like you've got all your equipment already, you'll probably
want to go with what you've got. I highly recommend the KNS-80 for its functionality
and cheapness used these days... Lots of bang for the buck. Ours is paired with a
thin KY-197 COM for a "super nav-com" combo... Also, the same converterless head
will work with the GPS. For the record as well, I believe the KX-165 also works with
a converterless head.

: 13) With upgrades in mind, who all is flying behind a KLN-94 (a direct
: slide in replacement for the 89B) and whats your feedback on it, as
: compared to the KLN 89 and 90 series GPS.

Never flown IFR with an IFR GPS.

: 14) Back to indicators... do all of the CDI's out there have OBS
: resolver outputs on them, or only specific brands? or only specific
: models of said brands? I am understand OBS resolvers to be the the
: ability of the GPS to read what radial the OBS is set to.

I'm not completely sure, but I think there are a couple of newer kinds. We
ended up with a KNI-520 on our KNS-80, but the KI-206 would also have worked AIUI.

: 15) Thinking ahead for when I get an AP. If I understand properly, the
: nav radio's (or GPS) drive the indicators, and the indicators drive the
: Autopilot with left/right info derived from the nav source. So, in
: theory, if the above is correct, when adding an autopilot that can take
: steering commands from the nav suite, its usually just a matter of
: adding the wires to the CDI (and switching, for multiple sources).

I'm not too familiar. I think when I was helping my mechanic rewire his
that's all it used.

: If Im wrong about something, I know without a shadow of a doubt this
: group will let me know. This is actually one of the harder tasks I've
: come across in partnering in this aircraft. While there are all sorts of
: DIY things that pilots can do from a mechanical/maintenance/building
: standpoint, there is not much Do-it-yourself stuff out there for
: avionics. I even obtained a fairly recently published book that claimed
: to be aimed at people like me - doing our own installs, but there wasnt
: much substance there except a rehash of good workmanship techniques
: (grounding, shielding, etc) and basic theory of operation. I dont even
: think I SAW the words gray code, slip code, 2x5 arinc, etc...let alone
: anything technical.

Tell me about it. Getting the official information is the most difficult part
for DIY. Once you do, it's not too difficult. Very careful practices need to be used
for materials, bundling, stress relief, support, chafe prevention, soldering, head
shrinking, etc to do a good aviation-worthy reliable job.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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