"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