Mk 219 Mods 2-4, and AN-Mk 219 (Nose Mechanical Impact)

Bombs

Functioning

Armed condition

Fuzes used with

Arming time

Vane span, inches

Body diameter, inches

Over-all length, inches

Material

Steel, aluminum alloy, and brass parts

General: This fuze uses the "rotor system" of arming, and the operation of this sys-tem is the same in all the fuzes that use it: AN-Mk 219, Mk 221, Mk 223, and AN-Mk 228. This fuze will function on impact with water or a denser medium, provided it has been dropped from sufficient altitude to arm.

Operation: There are two stages of arming. During the first stage, the upper gear is free to rotate and the lower gear is held stationary. During the second stage, the lower gear is free to rotate and the upper gear is held in stationary.

First stage: As the bomb is dropped, the arming wire is withdrawn and the vanes begin to rotate in a clockwise direction. Since the idler gear is attached to the vane car-rier and is in mesh with the upper and lower gears, when the vanes rotate, the idler gear is caused to move about the upper and lower gears. The lower gear is attached to the hammer carrier, and is locked because the hammer carrier is resting down in the inner sleeve. Since the upper gear has one more tooth than the lower gear, the upper gear will rotate in a clockwise direction, one tooth for every complete revolution of the idler gear. The upper gear is positively attached to the arming shaft, and, in rotating, threads the arming shaft up until the head of the screw on the end of the shaft locks aganist the shaft extension nut. A collar on the shaft lifts the hammer carrier and the entire arming assembly. Simultaneously with the locking of the arming shaft and the upper gear, the hammer carrier clears the inner sleeve, freeing the lower gear.

Second stage: The lower gear has on less tooth than the upper gear; hence, as the pinion continues to revolve (now meshing with the teeth of the stationary upper gear), the lower gear and hammer carrier are rotated in a counterclockwise direction. The alin-ing lug on the hammer carrier engages the firing-pin carrier, lining up the firing-pin exten-sion with the firing pin. Further rotation causes the firing-pin carrier to engage the deto-nator carrier, lining the firing pin up with the detonator. The hammer carrier, firing-pin carrier, and detonator carrier continue to rotate through 180 degrees, until the lip on the detonator carrier engages the inner sleeve. Simultaneously, the spring-loaded detent in the striker snaps into a recess in the hammer carrier, thus locking the firing-train compo-nents in an armed position. Since the upper and lower gears are now both locked, the two copper pins securing the lower gear to the hammer carrier are sheared and the van-es rotate freely. (If the air speed is less than 300 m.p.h., the air pressure will not be suf-ficient to shear the pins, and the vanes will merely cease rotating.)

The fuze is now fully armed. On impact, the entire upper assembly of the fuze is for-ced inward. The shear wire in the arming shaft is cut as the upper part of the shaft te-lescopes into the lower part, and the shear wire through the firing pin is cut as the firing-pin extension forces the firing pin into the detonator. The detonator sets off the auxiliary booster lead-in, booster lead in, booster, and main charge successively.

Remarks: The early Mk 219, Mod 2, 3, and 4 are identical to the AN-Mk 219. The dif-ferent Mods merely indicated the manufacturer of the fuze. This was important only in that slight differences in the manufacture prevented the interchange of parts made by different manufacturers.

The internal parts are held in the fuze by a single master locking screw.

Figure 360. Nose Fuze AN-Mk 219

Figure 361. Rotor System Arming