Jim, you're always looking for simple DIY projects for your kitplane
articles, aren't you?

Some guys on the flyrotary list have be batting around ideas on how to
determine if the prop on a pusher is windmilling. Would a piece of
reflective tape and an optical pickup suffice?

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."