We stopped by the mechanic doing the annual inspection on our 182. The interior is all removed, and all the inspection panels are open. This photo is behind where the rear seats and luggage compartment is. It shows the battery, and the computers used to run the glass panel screens.
Lots of wires and hoses in the aircraft. Once the mechanic has inspected the airframe he moves to the engine. Of course compression checks, and inspect the 12 spark plugs, mags, and everything else. Step by step, inch by inch, document everything. The battery for ELT (Emergency Location Transponder) is date coded so it gets replaced.
One thing for sure when he is done, we have a good annual inspection. The same guy did the 2 172s we leased. He said he found things that were not looked at in 5 years or more on those aircraft and we don't even have possession of them anymore. We returned them in way better shape than when we picked them up.