The so-called 70-50 rule has popped up a few times recently on the internet. I thought it would be useful to look at this rule, explain how to interpret it properly, point out some less-helpful interpretations, and share a bit of history behind it. I use the rule frequently myself—though not rigidly.
I applied full left stick and pulled back. I swear I could hear the engine of the other airplane as it passed the belly of mine. After I realized that we had missed each other, I looked around and could see only black and no horizon.
A recent magazine article on the subject of aerobatic flight got me to thinking about what the regulations actually say. While looking for information, I ran across a recent (2012) legal opinion from an FAA counsel that left me more confused than enlightened.