Upon detection of tha airplane by radar, I draw a 5 nm circle around my boat. When the plane nears the 5 mile radius I submerge. I'd estimate I probably begin submerging when the plane(s) are 7 to 8 miles away. I never crash dive, but just hit the "d" key at ahead 2/3, same as my surface cruising speed. I've never been detected in hundreds of submersions with that safety margin or I would have adjusted the radius. Since the plane has no reason to loiter, it does not. They don't even know I'm there. Remember the plan is to be gone before you are detected because if they detect you, they call their friends and play pin the tail on the donkey. You are the donkey and you do not have fun at their party.
I have come to radar depth when planes were still in the circle for some reason and just returned to depth for a couple of minutes. I used to search with the periscope, but found that I missed planes that way and gave them more time to spot me than if I just came up to radar depth and used the radar. It takes a little bit of time for the plane to see the submarine unless it is on direct course and I pop up in front of the plane.That hasn't happened yet, and I haven't been bombed from premature popups.
I have been bombed on approach to target at periscope depth by Ducimus' evil planes, so I know they're perfectly capable of tagging me. I don't claim my method is totally risk free, just much more risk free than staying submerged all day. Risk and war are good friends and always travel together.
But my methods are based on hundreds of successful plane evasions over sixteen cruises, not just doing the numbers. They work very well and I haven't had any reason to change them. I believe that by limiting dive times that severely you retain a valid picture of your environment at all times, enhancing your chance for survival while maximizing the number of square miles you can search for targets. This results in more enemies sunk.
As far as the enemy is concerned, a submarine hiding all day is the same as a sunk submarine: no danger for the day. Hiding is providing aid and comfort to the enemy and every bit as reprehensible as hiding on the battlefield, letting your buddies get killed while you might poke your nose out if the shooting stops. Stealth is not the same as hiding. Stealth is a tool of attack. Hiding is a tool of cowardice.
