There have been several threads lately about problems with planes in Silent Hunter 4, especially with TMO. These posts are quickly followed by advice on how to cheat and modify the configuration files to minimize or eliminate airplanes. I'm sure that's exactly how Dick O'Kane handled the planes.... Let me flatly state that planes in SH4 and in TMO are not a problem and if you are running your sub properly they cannot ever see you and cannot ever attack you unless you are attacking a convoy at periscope depth and get VERY unlucky.
Planes are not a problem if you handle them right. You don't have to and it isn't helpful to stay submerged all day or even for an hour after sighting one. All that does is discharge your batteries so you aren't combat ready.
Remember, a submarine is a surface boat with the unique ability to submerge when absolutely necessary, and to stay submerged for the absolute minimum amount of time. With airplanes, that means about 10 minutes total per plane. Our goal is to travel at maximum fuel economy speed, 9 knots, on the surface so we have 100% charged batteries available to fight at all times.
Let me explain. First of all, this strategy needs air search radar, a pretty common thing on American submarines. When a plane is first spotted on radar, you have several minutes of decision time. Let's use them! A couple of planes just showed up. What are they up to?
I immediately draw a 5 mile radius circle around my sub. That's my danger zone. If the planes enter that zone, they can possibly see me. My goal is never to be seen by a plane, EVER. That means no John Wayne popgun ineffectually giving away my position so the pilot can call his good buddies to the party and I'm swarmed for several days. I'm not going there. If a plane can possibly see me I'm pulling the plug.
OK, we have the visibility danger circle around the sub. Now, from the position of the plane, draw two lines from the plane(s) to both outsides of the circle (tangent lines).
Not every plane is going to enter your danger zone. If it does not we want to stay on the surface. 100% battery charge at all times you know... With our "ice cream cone" chart, we can easily tell with plenty of time whether this bad guy is going to be a problem. If he stays outside the cone, we're golden. If he crosses the line to the inside it's time to initiate avoidance.
At that point our goal is to be at or below periscope depth when he crosses the circle line of our danger zone. Pick a number below 100', I always just use about 110, your mileage may differ but I haven't had a problem with that and full-blown TMO. As you cross periscope depth, start your stopwatch. When it reaches 5 minutes, press surface ("s"). Do not dawdle around at periscope depth looking for planes. He's gone. No buddies not previously spotted on radar have had time to enter your danger zone. Your combat awareness is 100%. You are safe. Just get up there and resume surface travel.
You haven't been spotted. No little flyboy buddies will be checking you out. Also, I run around at best fuel economy, about 9 knots all the time. during my plane avoidance drill I don't touch the throttle. I submerge normally, none of this crash dive silliness, because you have plenty of time. Have you ever crash dived, surfaced and reentered time compression not remembering you were at full throttle? It'll make you cranky! Don't do it. Following my procedure it can never happen.
Planes are not an issue in TMO. They are not a threat. They cannot ever see you. The only thing that can hold you down is an escort. And if you didn't follow my airplane avoidance strategy, you're not ready for them because you have low batteries. You're a dead duck. Why would you care whether you were killed by a plane or by an escort. Wouldn't you rather not be killed by either?
