IDENTIFICATION OF ARMED FUZES.-

There are three conditions of the M904 fuze-safe, partially armed, and fully armed. You can verify the fuze conditions by looking through the two observation windows in the fuze body (fig. 1-1). To check the fuze condition, hold the fuze vertically and look through the windows perpendicular to the fuze body. Look at

Table 1-1.-LDGP and Fire Bomb Cook-Off Times

table 1-2. It shows you what you would see through the observation windows of the M904E3/4 fuze at various time settings and fuze conditions.

Also, check the M904E4 to make sure the thermal sleeve is firmly bonded to the fuze collar and is not cracked.

NOTE: If the safe condition of any fuze is in doubt, explosive ordnance disposal (EOD) personnel should be notified immediately.

Functional Description

The M904 fuze arms and functions by the rotation of the arming vane and alignment of its internal components. When the fuze is released from the aircraft, the fuze arming wire is withdrawn from the fuze arming vane, and the arming vane is rotated by the airstream. Arming vane rotation is controlled by the constant arming action of the governor in the fuze. The arming vane continues to rotate until the preselected arming delay period (2 to 18 seconds) elapses (ends). Once the arming delay period elapses, the firing train is in full alignment and ready to function.

At impact, the forward part of the fuze body drives the striker body and firing pin down into the M9 delay element. After the proper delay, the M9 delay ignites the relay, detonator, lead, and booster, which sets off the main charge.

MK 339 MOD 0 AND MOD 1 MECHANICAL TIME FUZES

The Mk 339 Mod 0 mechanical time fuze (fig. 1-2, without the option time wire), Mod 0 and Mod 1 (fig. 1-3) are used with dispenser weapons and have the following characteristics: Nose-mounted Air-enabling Detonator-safe

Table 1-2.-Indications for Determining Conditions of M904E3/4 Nose Fuzes

Figure 1-2.-Installed mechanical time fuze Mk 339 Mod 0 (without option time bomb cluster Mk 20 Mod 2 only).

Figure 1-3.-Installed mechanical time fuze Mk 339 Mod 1 (with option time wire bomb clusters Mk 20 Mods 3, 4, and 6.

The Mod 0 and Mod 1 fuzes are installed in the Mk 20 Mods 2,3,4, and 6 bomb clusters. The Mod 0 fuze without the option time wire configuration is used only in the Mk 20 Mod 2 bomb cluster. The Mk 339 Mod 0 and Mod 1 fuzes are installed in the bomb clusters during assembly by the manufacturer; therefore, the following information on these fuzes is limited.