DATA:

BOMBS USED IN

Mk 229 Mod 3

AN-Mk 230 Mods

4, 5, 6

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING TIME

OVERALL LENGTH

MAX. BODY DIAMETER

VANE SPAN

MATERIAL

Steel, aluminum alloy, and brass.

GENERAL:

The AN-Mk 230 Mod 4 and Mk 229 Mod 3 replace the AN-Mk 230 and Mk 229. The latest Mods incorporate changes which eliminate the possibility of the fuzes arming ac-cidentally when the bomb is dropped safe. The AN-Mk 230 Mod 4 and the Mk 229 Mod 3 are the same as previous Mods with the following exceptions:

(1) The fuze is sealed by a sealing cup above the detent carrier to prevent entrance of the water at any point other than the regular water.

(2) The arming mechanism which frees the arming detents operates by rotation of the detent retaining cup rather than by raising it vertically. A metal strap is fitted over the cup. These additions (1) prevent arming of the fuze in case the tail cone or arming mechanism housing is torn off the fuze accidentally upon water entry, and (2) prevent the fuze from firing from hydro-dynamic pressure which are encountered in erratic mo-vement of the bomb through the water or on re-entry after ricochet.

(3) The fuzes now have a slight oval undercut* above the fuze pocket threads to accommodate the new "O" Ring Gasket (live rubber) which has replaced the flat gasket formerly used. By using this "O" Ring Gasket, the holes for the safety rod located above the fuze threads are now sealed from water entry.

OPERATION:

The operation of the Mk 229 Mod 4 is similar to the AN-Mk 230 (refer page 249). When the bomb is released, the arming wire is withdrawn from the fuze, allowing the air stream to turn the arming vanes. The rotating vanes acting through the reduction gear, turn the arming shaft. Rotation of the arming shaft first causes the arming nut assemb-ly to rise (since it cannot turn because of two pins which project into the detent car-rier). When the two pins of the arming nut are fully clear of the detent carrier, the arm-ing nut "washer" jans under the arming shaft preventing further rising. The arming shaft than turns the arming nut assembly and by means ot the two pins, rotates the detent retaining cup approximately 85° until the two cutaway portions align themselves oppo-site the detents. The detents are then ejected, freeing the depth spring stem nut and thereby arming the fuze. (To limit the amount of water entering the sylphon bellows, the detents are prevented from jumping completely out of the detent carrier by the de-tent retaining pins which are fitted into the flange of the detent carrier). The inertia counterbalances prevent the fuze from functioning on impact with the surface of the water. After the bomb has submerged, water enters the fuze through two water ports in the body sleeve and the fuze fires at the predetermind depth setting. The use of the sealing cup above the detent carrier prevents water entry through the open end of the fuze in case the tail cone is broken off on impact.

REMARKS:

(1) DO NOT DISASSEMBLE THIS FUZE WITHOUT REINSERTING THE SAFETY PIN THROUGH THE LOWER FUZE BODY AND FIRING PLUNGER.

(2) *Eralier productions of these fuzes did not incorporates an undercut. In using the "O" Ring Gasket with these fuzes, a support ring (Steel washer, .120" thick) must be used to assure metal contact between the fuze and the fuze seat liner, thereby preventing distortion of the fuze on impact.

(3) The AN-Mk 230 Mod 5 is the same as the AN-Mk 230 Mod 4 except that the firing pin is welded to the booster cap as in the Mk 231, and the depth setting is em-phasized for 25 ft. and relaxed for 50 ft.

(4) The AN-Mk 230 Mod 6 is the same as the AN-Mk 230 Mod 4 except that the depth setting is emphasized for 25 ft. and relaxed for 50 ft.