I bought what was generally considered to be a very nice 1978 Grumman Tiger. It has an Aspen PFD and is GPS/WAAS equipped. So far I have put about 20 hours on it over the last 18 months. The last time I flew (6 months?), I discovered the ALT breaker didn't stop alternator from charging, pulling the Aux Audio Breaker did.
When I started looking into it, I found other wiring problems, 3 breakers not carrying a load were left in the airplane after old equipment was removed. Wires were run to new breakers installed in odd places to power new equipment.
There were old wires with insulation cracking off. Mis-wired circuits (somebody's better idea for a start circuit). Undocumented mystery wiring for unknown removable equipment. There were undocumented lighting parts that looked like somebody's old Heath kit. Most original lights were gone, original dome light with no on/off switches (INOP), glareshield lights that cut out after 5 minutes. In one area, the original wiring was working out of the crimped pins an original connector. There were many original radio wires that were cut and half removed still tied up under the instrument panel.
With the addition of the approved instrument modifications (generally well done), a lot of the original wiring diagrams are now obsolete. Unfortunately how new breakers were actually connected and what the loads on those breakers were was not apparent on any drawing.
Supposedly electrical loads were calculated with the various changes but there were no copies of an Electrical Load Analysis in the records. When I started working up my own wiring diagrams, I could see many of the wire size selections were incorrect for the breakers used.
Breakers keep wires from becoming a fire hazard, a breaker has to trip before a shorted wire can become hot enough to start a fire. It does you no good to use a 35A current protected switch to supply power using 20 GA wire. It also does you little good to install a breaker at the device being powered because the wire to the breaker is unprotected.
I also didn't like the current protected switches because you don't get an indication it if it does trip. The entire avionics master switch and bus aren't shown in the AMM diagrams or in the POH diagrams. It's there in the plane though, almost certainly installed with the Garmin which was conformed by a Garmin dealer on a 337 after the original undocumented installation.
Wires were rats nested everywhere. Grounds were attached everywhere. There were no places to secure the wiring added over the years, most of it was just suspended by the connectors. Small parts like the antenna coax splitter were just kind of wedged in the rats nest of wires.
Most of the STC records came with the airplane, but not all. There is a lot of typical aging aircraft stuff. I find new minor issues under almost every panel I open for the first time. I pulled back the side wall panel and found a cracked static line. Often it's just small stuff like edge grommet peeling and wires chafing. Several fairings and plastic parts need some TLC too. After 35 years, this ship needed more than another quickie line repair.
I still have most of the tools I used when I worked as a full time A&P. I'm an airline Engineer and have access to technical data and excellent contacts for advice.
My biggest problem is finding the time to drive to the field and work on the plane. I give it one day a weekend. That's the pace I can sustain without upending higher priorities in my life. I expect to be flying again in the spring.
I never really wanted a project plane and I knew an out of production airplane would present challenges. None of the problems are insurmountable.
My capacity planning was hugely unrealistic, but I'll definitely be flying soon and I'm really happy with how things are turning out. I will need a very thorough flight refresher.
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