Diving plane

As the planes are a long distance fore-and-aft from the hull's centre of buoyancy, they introduce a pitching moment.

If not carefully controlled, this could lead to a 'porpoising' motion whereby the planesman continually hunts for a stable combination of depth and pitch.

Earlier submarines (to World War II) used vertical folding planes perpendicular to their surface.

The depth control planes were mounted on the beam, so that they acted vertically, without the lever arm to introduce the usual pitch.

From the outset, diving planes were controlled remotely by telemotors, early servomechanisms operated electrically or by hydraulics.

For precise maintenance at periscope depth an additional shallow-depth manometer, a transparent vertical pipe, would be provided too.

The port bow plane of the Soviet-era submarine B-39
US Balao -class USS Bowfin of World War II, showing bow planes rigged upwards for stowage
Stern planes of HMS Ocelot mounted directly in the prop wake, with fixed planes above.
HSwMS Gotland from above, showing fairwater planes mounted on the sail
USS Pogy surfaced through Arctic ice, with sail-mounted planes turned vertically
Control room of U-9 with separate operator positions for fore and stern planes
Combined helm of HMS Ocelot