Oh well the bus driver has almost got it right.
Rod the Con,
I have got it exactly right, it is your reading and comprehension that is the problem, not to mention your writing.
As a "bus driver", I will back my experience in producing and tuning high performance race engines of the "old school" variety any day, against you.
And I certainly wouldn't knowingly let you anywhere near any aeroplane (or any other machinery) that I owned or controlled.
OK, so the last detectable upward motion rotating forward, and the last detectable upward motion rotating backward, then split the difference. thanks, I just couldn't get what you were trying to describe the first time.
A Squared,
Take it from somebody with a lot of relevant engineering experience, what I described will be more accurate in determining TDC than that described by Rod. Incomprehensible as it may seem to him, some/most "bus drivers" have other qualifications, and in this case, quite extensive experience -- with the silverware to show for it.
Tootle pip!!