OP 1664 - U.S. Explosive Ordnance (Vol. 2); Part 6 - Bombs and Bomb Fuzes; Chapter 20 - Bomb Fuzes; Section 3 - Navy-Designed Bomb Fuzes: AN-Mk 224 (Athwartship Hydrostatic) (Suspended from use)

U.S. EXPLOSIVE ORDNANCE

PART 6 - BOMBS AND BOMB FUZES

Chapter 20 - BOMB FUZES

Section 3 - NAVY-DESIGNED BOMB FUZES

AN-Mk 224 (Athwartship Hydrostatic) (Suspended from use)

Bombs	Depth Bombs Mks 17, 29, 37, 38; AN-Mks 17 Mod 2, 41, 44, and 47
Armed condition	When jump-out pins are out, fuze is partially armed. Arming is completed at 12 - 15-foot depth of water when primer and detonator are aligned with firing pin.
Functioning	Water pressure at depth set for 25, 50, 75, 100, or 125 feet of water
Fuzes used with	AN-M103, AN-Mk 219, or Mk 221 in nose, and Mk 229 in tail in 650-lb. depth bombs
Over-all length, inches	Pistol assembly - 6.9; booster extender assemblies - 9.9
Body diameter, inches	3.6
Material	Bronze, brass, steel, and aluminum

General: This is an athwartship fuze and is assembled in three subassemblies: pistol, booster, and booster extender. The pistol is marked for the depth at which it is set, and contains the firing mechanism and the detonator sliders. The desired depth setting is made by inserting in the proper firing-pin spring and auxiliary spring if necessary, with settings of 25, 50, 75, 100, or 125 feet possible. The following tabel shows the springs to use for the various de depth settings:

	Depth	Spring Color
	25 feet	Yellow
	50 feet	Black
	75 feet	Black and green
	100 feet	Yellow and red
	125 feet	Black and red

The yellow and black springs, as selected, actuate the firing pin and, in addition, serve a depth-controlling purpose. Green and red springs are auxiliary depth-control springs and do not actuate the firing pin. The booster extender fits into the opposite end of the transverse tube in the depth bomb.

Operation

Action in booster extender: As the arming wire is pulled, the jump-out pin is forced out by its spring, and water enters the assembly as the bomb becomes immersed. The water expands the bellows until it overcomes the pressure of the spring acting against the locking slide. The booster spindle and the locking slide are held together by the lock-ing balls between them. When the water pressure has forced the piston, locking slide, and the spindle inward sufficiently for the locking balls to slip into the enlarged groove in the fuze body, the entire booster extension is free to move the remaining inch toward the pistol. The hollow-cone shaped slider aligner, bearing inward against the L-shaped primer and detonator sliders, forces them inboard against their springs, thus lining up the explosive train.

Action in pistol: As the water pressure increases and overcomes the tension of the firing and auxiliary depth springs in the piston, the bellows extend and the base of the hydrostatic piston moves down over the firing pin guide piece. This action compresses the firing and auxiliary depth springs; and, when the enlarged part of the hydrostatic pis-ton comes opposite the locking balls, they are forced out by the spring pressure, freeing the firing pin to be forced against the primer. The L-shaped primer and detonator sliders will have been lined up with the firing pin by the action of the slider aligner.

Remarks: If the booster extender fails to function properly and force the slider aligner over the primer and detonator sliders, the fuze cannot function. The slider aligner which holds them in the armed position is prevented from returning to the unarmed position by the locking slide, which locks after the locking balls are forced out from the spindle in the extender.

Figure 365. Athwartship Hydrostatic Fuze AN-Mk 224