Yesterday, I attended a FAA safety seminar where the topic was
maintenance issues. I walked away with a few surprising nuggets of
information. These issues have been discussed here in the past and some
of the information posited here disagreed with what the FAA said. So, I
thought it would be useful to list them here.

Now, before everyone flames me and tells me I'm an idiot, these are not
my opinions, they are the opinions of the Safety Inspectors at
Washington - Dulles FSDO.

Manuals:
You must have current service manuals to do any (including preventative)
maintenance on your bird. That includes all service letters. A few
pilots grumbled that certain companies will not send the service letters
to the owners. The Safety Inspector said that didn't matter. Missing a
service letter makes the manual out of date and unusable.

Parts:
You must buy the parts from an aviation source. Someone brought up that
landing lights can be bought cheaper at automotive supply stores than
from aviation outlets at a fraction of the cost. The FAA wouldn't hear
of it. It does not matter if the part is made by the same company with
an identical part number, if you didn't get it from an aviation source,
then it is not an airworthy part. The Safety Inspector gave three
examples, the light bulb above, an alternator belt, and an air filter.

I guess that the alternator belt part number you would get in a
automotive store has fewer layers of material in it than the one
approved for aviation. The belts were the same dimensions, but there
was an extra layer in the aviation belt, but they both had the same part
numbers.

The air filter from some airplanes also fit some automobiles. Same Fram
part number. The Inspector used this as a uncertainty example. Are the
parts exactly the same, who knows?

I was going to ask him how do we know that we're getting approved parts
from aviation houses if the manufacturers use identical part numbers for
aviation approved and non approved parts. But by the end of this
discussion, he was getting kind of ticked by all the questions, so I
took a pass.

Logs:

All preventative maintenance must be logged, including updating the
database on your GPS unit. So, if you have updated your GPS database
and did not log it, you're not airworthy. This one caught a lot of pilots.