Hi Tore,
I believe the mechanical emergency operation of the hydroplanes was very sturdy and placed inside the pressurehull could take a lot of beating from depthcharging. However the system required a lot of maintenance (greasing) to stay relyable. A local 3 positions for operations of rudder and hydroplanes would be a challenge for the immediate communication and would require further instruments for immediate response to keep the vessels positions (angle) which is a combination of operation of fwd. and aft hydroplanes. I guess I would have preferred to maintain the system of a VIIC above three local emergency operations.
Thank you for your answer. Of course, emergency steering stations located locally in aft and forward torpedo rooms would be quite challenging.
Anyway, US Gato and Balao diving planes systems were operated hydraulically. The description can be found here:
http://www.maritime.org/doc/fleetsub/hydr/chap5.htm#5AAs I understand, there is no other way of controlling them than hydraulic. In case of failure of the hydraulic pumps, the only emergency recovery mode is the hand pump. It seems, that in case of damaging the hydraulic piping, the whole system is broken.
On the other hand, the hydraulically driven diving planes on type XXI U-Boats were fitted with emergency hand drive (but only aft pair).
I suppose, that it is because the aft plains have more effect on the control of the submarine than forward planes.
Here is another example - the British Oberon class submarine:
http://maritime.org/doc/oberon/hydraulics/index.htm#pg26These subs have also hydraulically operated diving planes, and it seems, that after pair has the following emergency gear - in case of damage of the hydraulic system, to the actuating piston controlling the planes can be connected high pressure air, which controls the angle of planes (or sets them to the "surface" position).
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Regards
Maciek