PTH...."the current idea of one altitude for slower piston planes and 1500'agl for turbines makes sense to me....."
I would agree, IF everyone follows this! My own war story practically led to me becoming a cliched statistic. Pattern entry into an uncontrolled field. Traffic was a cherokee in closed traffic.
The cherokee SHOULD have been at 800 AGL -the published TPA (the field was Nut Tree in northern California). I was approaching from the east, with a northbound runway in use, and had just terminated flight following with Travis Approach. My plan, and as I announced on CTAF, was to cross over the middle of the field at 1,500 AGL and then descend and turn to make a 45 degree entry to downwind once traffic was in sight.
This should have given me a very comfortable 6-700 feet clearance HOWEVER, the other cherokee was WAY above TPA and VERY suddenly, I had what seemed to be a windscreen full of another airplane! I pulled up and went to the right...he went to the left. I have NO idea how much separation we had, but to this day, I would swear I could count rivets! (In all honesty, it probably wasn't THAT close, but I sure grabbed a whole lot of seat cushion!)
(On the ground, I talked to the other guy - a CFI and his student - the CFI admitted to be flying at approximately 1,200 AGL, which is the TPA for twins, kind of blamed his student for not being more precise with his altitude control. I told the CFI that it was his responsibility to make sure his student was at the correct altitude!
)
This incident gave me nightmares for a long time afterward, and also for a very long time I gave up solo flight and always had a safety pilot with me.
So... in the approach phase, all bets are off and EVERYBODY had better have Mk1 eyeballs outside!
