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Potentially Dangerous Evolutions Never Done After THRESHER

A friend - upon receiving a copy of the final draft of WHY THE USS THRESHER (SSN 593) WAS LOST - has gone to sub vets to identify evolutions approved for use in 1963 but not thereafter. Although only one of these tests could have played a role in the loss of THRESHER, both are examples of potentially very dangerous evolutions then permitted..

Below are two responses:.

Another discontinued test after THRESHER: go to test depth, hover and then disconnect the clutch. See if hull flexures inhibited clutch performance. Fine, unless the clutch would not reconnect, then you were at test depth with no propulsion as the EPM (the "outboard motor") could not be extended at depth.

Another stunt we no longer do on sea trials. The Crash Dive. Left over from WWII. Get up to standard speed, open the vents and time how long to submerge. As PXO PARCHE, I was allowed to ride TUNNY sea trials out of Pascagoula, as she was the ship ahead of us. So TUNNY got set, up to speed, popped the vents, but the stern planesman put full dive on the sternplanes, the propeller was lifted out of the water, the main engines tripped on overspeed, and the ship took a 20 degree down angle. The angle was too extreme for operators to get to and reset throttles. Hurtling through 400 feet, the Captain, Denny Sloan, ordered emergency blow. TUNNY did not reach test depth, but soon after things settled on the surface, Admiral Rickover appeared in Control and simply said “We will not do that again”. This Crash Dive test was removed from all sea trials from that point forward.

Not during the writer's testimony before the THRESHER Court of Inquiry (COI) was there any discussion of THRESHER's post-overhaul, deep-dive test agenda nor has the writer seen such discussion in any COI documentation.

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