Mk 229 Mod 3 (Obsolete) and AN-Mk 230 Mods 4, 5 and 6 (Tail Hydrostatic)

Bombs

Mk 229 Mod 3

AN-Mk 230 Mods 4, 5, and 6

Functioning

Armed condition

Fuzes used with

Arming time

Over-all length, inches

Body diameter, inches

Vane span, inches

Material

Steel, aluminum alloy, and brass

General: The Tail Hydrostatic Fuzes AN-Mk 230 Mod 4 and Mk 229 Mod 3 replaces the AN-Mk 230 and Mk 229. The latest Mods incorporate changes which eliminate the possibility of the fuzes arming accidentally 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 ex-ceptions:

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

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 (a) prevent arming of the fuze in case the tail cone or arming-me-chanism hosuing is torn off the fuze accidentally upon water entry, and (b) prevent the fuze from firing from hydro-dynamic pressures which are encountered in erratic move-ment 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 ac-comodate the new O-ring gasket (live rubber) which has replaced the flat gasket former-ly used. By use of this O-ring gasket, the holes for the safety rod located above the fuze threads are now sealed from water entry.

Operation: In operation, the Tail Hydrostatic Fuze Mk 230 Mod 4 is like the AN-Mk 230. When the bomb is released, the arming wire is withdrawn from the fuze, allowing the air stream to turn the arming vanes.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 as-sembly to rise (since it cannot turn because of the two pins which project into the de-tent carrier). When the two pins of the arming nut are fully clear of the detent carrier, the arming nut "washer" jams under the arming shaft, preventing further rising. The arm-ing shaft then turns the arming nut assembly and, by means of the two pins, rotates the detent retaining cup approximately 85°, until the two cutaway protions align themselves opposite the detents. The detents are then ejected, freeing the depth-spring stem nut and therby 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 counterbalance prevent the fuze from functioning on impact with the surface of the wa-ter. After the bomb has submerged, water enters the fuze through two water ports in the body sleeve, and the fuze fires at the predetermined 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: Do not disassemble this fuze without reinserting the safety pin through the lower fuze body and firing plunger.

Earlier productions of these fuzes did not incorporate an undercut. In using the O-ring gasket with these fuzes, a support ring (steel washer, 0.120 inch thick) must be used to assure metal contact between the fuze and the fuze-seat liner, thereby preventing dis-tortion of the fuze on impact.

The Tail Hydrostatic Fuze AN-Mk 230 Mod 5 is the same as the AN-Mk 230 Mod 4, ex-cept that the firing pin is welded to the booster cap as in the Mk 231, and the depth setting is emphasized for 25 feet and relaxed for 50 feet.

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 feet and relaxed for 50 feet.

Figure 367. Tail Hydrostatic Fuze AN-Mk 230 Mod 4