1. They did a periscope surface search while "broaching" the boat so its decks were just awash; the sail and scope probably had a height above sea level at that position of about (I think) 35 feet.

2. The Japanese vessel was at that time apparently only a mile or so away; but bear in mind that it was in stern aspect. The fact that the vessel was 170 feet long means nothing if it is only twenty feet wide, viewed from stern-on.

3. I believe the vessel was white, and that weather conditions were enough to cause widespread whitecaps all around. This means (if I remember my Beaufort scale correctly) that it was greater than force 4 with wind speeds over 20 (I could be wrong about the last, though).

4. Anyone who thinks that you can do a sonar scan on the surface in choppy water and expect to differentiate a target should try it some time.

5. They did (probably) have radar which would have been atop the sail, but still very (relatively) close to the water, and depending on the sea state a less experienced radar operator could easily have missed a target in the sea-clutter IF they were using it. Submarines as a rule don't carry expert radar ops because their use of it is infrequent for obviosu reasons.

6. The visual use of periscope detection of a white hull, presenting stern aspect in choppy waters with whitecaps blowing around is a problematical proposition at best. This is especially the case if the observer is (a) hastening through a rote procedure without due real attention or (b) not a veteran observer sensitive to small anomalies. The presence of guests could not have had any contribution to the accident except possibly putting the sailors in a more social and less rigorous frame of mind contributing to (a).

A sub has no control at all over its rate or net direction of ascent once it blows ballast in a test of this kind. The entire vessel is completely in the grip of a purely physical process, bouyancy, uncontrolled as a cork popping up from the bottom of a rainbarrel.

7. One point of caution that could have been taken but which probably was not was a close supervision of the crewman's scope scan by the CO monitoring the TV monitor which shows by television what the 'scope is viewing optically. It is not a doctrinal part of the procedure but something a veteran sub commander might due out of caution and experience. However the CO did repeat the scan optically. Again, he may have been rushed by the presence of guests, feeling perhaps like a showman instead of a CO. I have seen no data indicating any other error that could have been caused by the presence of civilians on board.

8. Although (7) under most circumstances might have been a non-significant error it combined with other circumstances in this case to suddenly become highly significant.

9. My own conclusion, based on incomplete data, is that a terrible tragedy occurred due to a human error well within normal range of human error -- meaning not a bizarre or highly unusual human failing -- namely, failing to see a narrow white object among whitecaps and wind through a periscope in a (probably) single moving 360º sweep. The CO has been relieved, predictably, because he is held in absolute responsibility for the vessel regardless of all other factors; the OOD is certainly under severe scrutiny, or formal inquiry leading to a possible trial under Military Code of Law procedures. This tragedy has struck both those officers as well; the chances (in my opinion) are very high that they believed they were executing correct procedures and were performing at their normal excellent standard right up to the moment that god-awful sound penetrated the pressure hull.

Regards,

A