My house is in Class E sfc air space created by a small private airport 5.5 miles away. The airport is open 8a-4p Monday -Friday. So I believe in order to fly in my backyard I have to contact the airport for permission even though I will fly at 100' max and within the confines of my own property lines. Is the Class E airspace only in effect during the hours they operate? If I want to fly at 6pm one night or on weekends, times when they are closed, is it ok to just fly? Common sense tells me yes but this doesn't seem to be a common sense oriented hobby as far as some of the rules and regulations go. I don't have a drone yet and honestly, things are so confusing I'm not sure I really want one! I'm also within Class E space from two other airports but they have 700' and 1200' lower altitude limits.