Thoughts on a 1966 Cessna 172G?

[Malcolm Teas]

Ok, so this isn't quite a fabric wing bush plane I was talking about
before, but it looks to be a good IFR platform, and it's seems in good
condition so far. Yeah, it's like Dad's stationwagon, but 172s are
good well-known planes too. We're going up this weekend to take a
look up close and see what we think.

Anything special to look out for on the 172G model? It's got the flat
six O-300 engine with an auto gas STC and Mk 12 radios.

Thanks,
-Malcolm Teas

[Jim Weir]

The Mark-12s are going to be a problem. If you are talking about the original
vacuum tube design (12, 12A, and 12B) with the monster power supply sitting back
aft of the hatrack in the empennage, they are FCC illegal last time I looked
(*).

As a practical matter, the 12s have a few critical parts that are absolutely
unobtainable any more...the little Nuvistor with the plate cap in the crystal
oscillator springs to mind. The crystals are damn near 50 years old and are a
bit aged. The point being is that you will be happy with those radios just long
enough to get the airplane home.

OTOH, if they are the 12D solid state replacement radios, you will be happy with
them for quite a while.

As to the airframe, the ADs are few and relatively inexpensive to comply with.
The most expensive one that comes to mind was the nose gear fork that should
have been replaced twenty+ years ago or better.

If you have a friendly IA with the computer disk, ask them to run you a computer
printout of the AD list...they will need to know what mags are on the unit,
which prop, which carburetor, etc..

If you DON'T have a friendly IA, I will run you a list and give it to you in
pdf IF you can supply me the accessories list as above. I'd also ask the owner
for the current equipment list, check it against the current weight/balance,
then look to see what is on the airplane that isn't on the equipment list.

Jim

(*) The 12s are FCC illegal, *not* FAA illegal. The practical side of it says
that you can fly with them and use them into the NEXT millenium before you will
come up against an FCC cop. They've got better things to do like chase bandit
broadcasters and the like than mess with a radio that is a few kHz. off
frequency. -- jw




(Malcolm Teas)
shared these priceless pearls of wisdom:

->Ok, so this isn't quite a fabric wing bush plane I was talking about
->before, but it looks to be a good IFR platform, and it's seems in good
->condition so far. Yeah, it's like Dad's stationwagon, but 172s are
->good well-known planes too. We're going up this weekend to take a
->look up close and see what we think.
->
->Anything special to look out for on the 172G model? It's got the flat
->six O-300 engine with an auto gas STC and Mk 12 radios.
->
->Thanks,
->-Malcolm Teas

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[G.R. Patterson III]

Malcolm Teas wrote:
>
> Anything special to look out for on the 172G model? It's got the flat
> six O-300 engine with an auto gas STC and Mk 12 radios.

Double-check the radios. If they're the Mk-12D model, you're ok. If they *are* the
Ds, the only problem is the display. If the display starts to go, the first sign is
usually that the display goes out when you turn into a low sun or fly at night,
although the radio continues to work. There's a photosensor in the front panel, and
shining a flashlight on the sensor will brighten the display back up. Any avionics
tech can adjust the power level and correct that problem.

Actual failures of the display occur infrequently, but cost around $200 when they
happen, and the radio has to go back to NARCO for the repair.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Dan Thomas]

"G.R. Patterson III" > wrote in message >...

> Actual failures of the display occur infrequently, but cost around $200 when they
> happen, and the radio has to go back to NARCO for the repair.
>
> George Patterson

Our Avionics shop replaces the displays in those 12D's for us.

172 airframe stuff: cracked horizontal stabilizer front spar,
caused by people pushing down on the stab to maneuver the airplane.
Cessna strongly discourages that practice. The cracks will radiate
from the lightening hole, and can be seen when the covers between the
fin and stab are removed.
Worn rudder hinges. The rudder pedal springs (which might be
busted, by the way) pull on the rudder horn and because of the swept
tail, downward on the rudder as well, wearing the hinge bracketry as
well as the bushings. The rudder swings a bit in the wind, and with a
bit of grit in there, the wear can be pretty bad. Grab the bottom of
the rudder, both sides at the horn cutout, and pull straight back and
up some.
Worn trim tab hinge. Cracked plastic tip fairings. Seat tracks,
seats, rollers, and locking mechanisms on these airplanes are cheap
and prone to wear. An AD against that. World's largest civil aviation
lawsuit ($450 million or so) due to those tracks.
Firewall/nosegear damage from hard/incompetent landings. Bent
tail tiedown ring from tail strikes, and perhaps a damaged bulkhead at
that point. Broken fuel tank retaining straps. Worn flap tracks, and
especially worn flap support arms from the roller edges cutting into
them. Makes for flap failure.
Corrosion in the wings and tail from birds nesting in them,
especially in the wing's leading edge near the landing light window.
They get in through the holes at the aileron cutout and enjoy a
lighted but secure home. Mouse nests in the headliner and belly.
Sounds bad, but there are far worse airplanes. The 172 was a good
design overall.

Dan

[Malcolm Teas]

Jim Weir > wrote in message >...
> The Mark-12s are going to be a problem. If you are talking about the original
> vacuum tube design (12, 12A, and 12B) with the monster power supply sitting back
> aft of the hatrack in the empennage, they are FCC illegal last time I looked

Thanks Jim and GR. I got lucky. Turns out they're the TKM MX 12
NAV/COMM with glideslope, it's an OEM replacement for the old Mark 12s
I gather. I got that from the panel picture and matching with catalog
pictures. There's two radios, which is always nice.

The transponder appears to be a Narco AT 155 or very simiilar (again
judging from pictures). The intercom was replaced in February.
That's it for the electronics, no DME, GPS, or even ADF.

The VOR heads are older as they've got the blue and yellow areas on
the bottom of the dial.

> As to the airframe, the ADs are few and relatively inexpensive to comply with.
> The most expensive one that comes to mind was the nose gear fork that should
> have been replaced twenty+ years ago or better.

Nice to hear! I want to get a good look at the log books this weekend
and will check that.

> If you have a friendly IA with the computer disk, ask them to run you a computer
> printout of the AD list...they will need to know what mags are on the unit,
> which prop, which carburetor, etc..

Ok, working on getting the info. I'll be able to get it this weekend
definately. I'm told it's all up to date except for the pitot-static
inspection which has lapsed.

> If you DON'T have a friendly IA, I will run you a list and give it to you in
> pdf IF you can supply me the accessories list as above. I'd also ask the owner
> for the current equipment list, check it against the current weight/balance,
> then look to see what is on the airplane that isn't on the equipment list.

Ok, I'll check on the equipment. I think I know someone locally, if
that doesn't work out I'll email you. I appreciate the offer! I
would need to find someone to do a pre-buy with around here in any
case.

-Malcolm Teas

[Malcolm Teas]

(Dan Thomas) wrote in message >...
> "G.R. Patterson III" > wrote in message >...
>
> > Actual failures of the display occur infrequently, but cost around $200 when they
> > happen, and the radio has to go back to NARCO for the repair.

> ...

> 172 airframe stuff: cracked horizontal stabilizer front spar...

Great stuff! Thanks folks, I'm printing this all out to take with me
Saturday. Also I found the AD listing on the FAA website, but am not
that familiar with them. It'll be a starting point at least. I do
plan to do a pre-buy with a qualified A&P if my own check of the plane
looks good.

-Malcolm Teas

[Malcolm Teas]

(Malcolm Teas) wrote in message >...
> Anything special to look out for on the 172G model?...

Ok, I went to look at it this weekend. Nice overall, but the
stabalizer was replaced and logged, but the damage to the rudder was
not logged. Even in the annual two months ago. The damage was clear
that it was longer ago that that.

A few other issues: one radio inop for example. But nothing that
couldn't be dealt with.

But, for a plane advertised with NDH, it's not a good sign to find
obvious damage.

Thanks for the advice!
-Malcolm Teas