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| U.S. EXPLOSIVE ORDNANCE |
| PART 6 - BOMBS AND BOMB FUZES |
| Chapter 20 - BOMB FUZES |
| Section 3 - NAVY-DESIGNED BOMB FUZES |
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Mk 221 and Mk 239 (Nose Mechanical Impact) (Obsolescent) |
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Bombs |
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Mk 221 |
500-lb. G.P. Mk 12 1,000-lb. G.P. Mk 13 |
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Mk 239 |
AN-standard G.P. Bombs |
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Functioning |
0.01 second delay |
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Armed condition |
When striker flange has risen more than 5/16 inch from outer sleeve, and arming wire is gone |
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Fuzes used with |
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Mk 221 |
Mk 223 |
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Mk 239 |
AN-M100 series in AN-M G.P. bombs |
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Arming time |
Approximately 150 revolutions |
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Vane span, inches |
5.3 (four vanes) |
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Body diameter, inches |
2.75 |
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Over-all length, inches |
8.5 |
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Material |
Steel, aluminum alloy, and brass |
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General: The Nose Mechanical Impact Fuze Mk 221 is essentially the same as the Mk 219, but it incorporates the following differences: |
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1. The body is longer and larger. |
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2. It incorporates a delay of 0.01 second. The delay element and percussion-type fi-ring pin are housed in the delay carrier. The delay carrier corresponds to the firing-pin carrier in the Nose Mechanical Impact Fuze Mk 219. |
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3. A protecting cap is over the head. The vanes are screwed to the vane carrier by four screws which pass through the protecting cap to the vane carrier. |
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4. The are three lock screws instead of one. |
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5. When the fuze is armed, a lock pin in the floor of the fuze body falls through an opening in the shaft extenson nut, locking the rotor and the delay carrier to the shaft extension nut, and thus preventing the parts from getting out of line before impact. |
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6. The central spindle has a shear collar and a guide pin which permit the central spindle to telescope. The Nose Mechanical Impact Fuze Mk 239 is a Fuze Mk 221 modi-fied by reducing the diameter of the fuze (extending from the booster cup to the fuze threads) from 1.875 inches (Mk 221) to 1.59 inches. The Mk 239 was designed to utilize present stocks of Fuzes Mk 221 in AN-standard G.P. bombs. |
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Operation: The operation of the Mk 221 and Mk 239 is the same as the operation of the AN-Mk 219. |
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Remarks: The delay element consists of a primer, a delay pellet of black powder, and a special detonator consists of fulminate of mercury mixture; and the auxiliary booster lead-in, booster lead-in, and booster consist of tetryl. |
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The Mk 221 will fit into the nose of the depth bomb, but the 0.01 second delay may allow the case of the bomb to be so damaged that a low-order detonation may result. Therefore, it is not recommended that the Mk 221 be used with the depth bomb. |
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Figure 362. Nose Fuze Mk 221 |
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