Mk 51 Gun Director

Mark 51 Mod.2 director with Gun Sight Mark 14 Mod.6, from the wartime Ordnance Pamphlet OP 1040 for the Gun Sight Mark 14 (all mods)

A Mark 51 director controls a 40mm Bofors twin mount

The Mark 51 director was a lightweight hand-operated machine gun director developed for the US Navy in early 1942. Essentially a Mark 14 gun sight on a pedestal, the Mark 51 director was operated by a single crewman who aimed the director in train and elevation, using the associated gun sight to track the target. Gyros inside the gun sight generated the lead angle after a few seconds of smooth tracking by the operator. Mark 51 could control 1.1" and 40mm mounts, and was later adapted (with the updated Mark 15 gun sight) to control 3"/50 and 5"/38 guns as well. Mark 51 was much simpler than its preceding machine gun directors (Mark 44, Mark 45, and Mark 49), and therefore much easier to mass produce. Wartime production amounted to 14,000 directors and 85,000 gun sights, and Mark 51 equipped nearly all USN combatant ships and auxiliaries by the end of the war.

Versions

• Mark 51 Mod.1 and 2 - initial version of the director built for the Mark 14 Mod.3 or Mod.4 gun sight
• Mark 51 Mod.3 - later version designed for use with the Mark 15 gun sight, capable of interconnection to control 5"/38 mounts
• Mark 51 Mod.6 - late-war version designed for use with the Mark 15 Mod.12 gun sight as part of the larger Mk 63 GFCS

See also

• US Navy Bureau of Ordnance, Ordnance Pamphlets (OPs) (NARA RG 74)
  • OP 1119, Gun Director Mark 51 Mod.3 - 22 July 1944
• US Navy Bureau of Ordnance, Ordnance Data (ODs) (NARA RG 74)
  • OD 4424, Gun Director Mk 51 Mod 1 including Gun Sight Mk 14 Mod3 or Mod 4

References

• Friedman, N. (2014). Naval Anti-Aircraft Guns and Gunnery (Illustrated ed.). Naval Institute Press.