[PSUBS-MAILIST] Vanguard class sub (UK) unintended depth excursion

[Jon Wallace via Personal_Submersibles]

 As Dan mentioned, for psubbers, not diving in water deeper than your sub's capability is good advice and we have this concept codified in the PSUBS operating guidelines section 4.1.2 paragraph 2.  Using multiple sensors for either backup or a weighted result between them is also a good idea except could be an expensive option given the price of some sensors.  A pressure transducer of mediocre accuracy for example is going to be in the $150 each range.
What kind of protocol for verification of a single sensor would be effective?  The only thing I can think of for depth would be tying a marked rope to the vessel and comparing the pilot's observation to surface observation.
Jon

    On Monday, November 20, 2023 at 11:57:50 AM EST, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Just read an article about an incident with a British Vanguard Class submarine that had an incident where it went far too deep, apparently as a result of faulty instrumentation. Engineers became aware of the sub's depth when they observed some backup depth instrument(s) and rectified the situation before it became a castastrophe.

Just wanted to prompt some discussion here, because PSubs don't necessarily employ robust backup systems, and at minimum, we should endeavour to ensure that all critical instrumentation is periodically calibrated to some reference standard to ensure accuracy, and also periodically verified in order to have some mechanism in place to detect malfunctioning instruments.

Backup instrumentation is a great method to achieve the latter (instrument verification), but comparing the primary and backup instruments needs to be part of SOPs. Where backups don't exist, some means of functional verification should at least be employed, if not per dive, then perhaps per trip?

This was a military sub that was almost lost because of an easily avoidable problem.

FWIW.

Sean

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