The only thing I recall in the ceiling was an auxiallary valve for the negative bouyancy tank that coul be manually turned to release the entrapped air quickly to flood and with 5 tons of additional water the sub would now sink faster in a dive. This valve needed to be closed and the tank blown dry to get postive bouyancy back in the boat. The tank was often used rather than main ballast tanks as using power and forward and aft planes allowed the boat to change depth rapidly with little attitude change. Great for Torpedoe shots at short range and avoiding surface broaches.
Calculating the tanks settings changed constantly with fuel loss, torpedoe expenditure, waste, etc. But it saved a lot of compressed air which in a boat was precious. Running the turbine blowers was noisy and took time to blow the main ballast tanks. This was of course the only way to get the sub up out of the surf for surface running.
Other than a manually operated sound head I can think of no other contrivance so attached. See
http://www.maritime.org/fleetsub/sonar/chap1.htm#1A
