What were the bow and stern planes?

These were small wing-like structures at the front and back of the boat that move up and down. They were used to change and maintain depth while moving through the water. The bow planes were rigged up to the side of the boat when on the surface. (The starboard bow plane on the USS Pampanito is visible from the pier.) The stern planes were always rigged out and were protected by guards. They were under water and not normally visible.

The bow planes were normally used for small changes in depth. Perhaps the captain or officer of the deck wanted to see something farther away. That meant that the periscope needed to be higher. They couldn’t just raise the periscope or the officer wouldn’t have been able to reach the optics. Instead, they decreased the depth, raising the whole submarine.

Stern planes put an angle on the boat, up or down. Stern planes were used for larger changes in depth, for example from periscope depth (63 feet or so) to 300 feet. That way, the forward motion of the boat generated the change more quickly. It was similar to an aircraft taking off or landing.