EXPLOSION IN TURRET TWO
Investigation Continued

33.            Specifically, those references appear to indicate a misplaced confidence in the degree of assurance afforded by a sampling-type approach, including the firing of a number of samples at Dahlgren.  Reference (n) suggests that a similar misappreciation may exist at working levels within HQ NAVORDSYSCOM.  We reemphasize that the sampling-type approach is normally adequate with respect to features such as those which concern functioning at the target; but it never was, is not now, and can never be acceptable with respect to defects which are potentially lethal to the fleet user – of which in-bore fuze prematures are among several notable examples.

34.       We consider the design of the ADF Mk 55-0 (and of the similar Mk 54) to be adequate with respect both to safety and to intended performance at the target.  The design could be improved somewhat by changes we have discussed with NAVORDSYSCOM staff.  But no changes could protect against certain manufacture/inspection defects such as documented in reference (j).  Thus nothing related to possible design improvements of the ADF Mks 54 or 55 can reduce the need for attention to the primary requirement for effective, responsible, and responsive manufacture and inspection.

35.       Rather than undertaking design improvements for the ADF Mks 54 or 55 it appears preferable to adopt the Mks 379 (5”/38), 395 (5”/54), and a further variant (if required) for other fleet calibers.  These fuzes incorporate an anti-malassembly feature, and also a mechanical arming delay intended to prevent primer firing until after projectile travel several hundred feet beyond the gun muzzle.  Regardless, however, of whatever sanguine hopes might attach to the appearance of such fuzes in service (some years hence at the earliest), nothing would eliminate the requirement to return to former Navy standards of meticulous manufacture and assembly, and rigorous, accountable inspection, of all ammunition and components.  This must include 100% inspection, at several successive echelons, of all features bearing on user safety.

36.       Finally with respect to ADF bore safety, although the Mks 379 and 395 are in procurement, quantities of 5”/38 and 5”/54 projectiles remain in inventory which are fitted with ADF Mk 54 (Mods).  The latter ADF is also standard in service 6”/47 HC projectiles.  Design-wise this fuze is the same as the Mk 55 except for the difference in arming spin rates.  Hence it must be recognized as essentially in the same category as the Mk 55 with respect to potential in-bore prematures resulting from manufacture/inspection derelictions.  Thus far its actual safety record seems to have been statistically somewhat better than the Mk 55, possibly due to manufacture by different contractors (KDI and Maxson).  But, as a minimum, it would appear that a substantial Mk 54 sampling program by X-ray should be initiated earliest.

37.      Certain fuze considerations paralleling those for the ADF also require recognition for the BDF.  By design these fuzes, of which the Mk 48-4 in NEWPORT NEWS 8” HC is an example, appear adequately safe against being armed and initiated in bore.  (Of course, on the basis of its design, so does the ADF Mk 55).  But the in-bore environment

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