AN-M103AN-M139A1, AN-M140A1, M139, M140
U.S.N.B.D. - UNITED STATES - BOMBS AND FUZES; PYROTECHNICS
SECTION III - BOMB FUZES

DATA:

  

ARMY-NAVY NOSE FUZE

 

  

AN-M103A1

BOMBS USED IN

 All G.P. bombs except Mk 4

 

 Mod 4. The depth bomb for

 

 land targets, chemical,

 

 frag. and incendiary bombs.

(Service)
  May be used in S.A.P. for

 

 

 frag effect, but result not

MECHANICAL IMPACT

 

 too consistent.  

FUNCTIONING

 Instantaneous or .1 sec.

 
  delay alternative settings.  

ARMED CONDITION

 When safety discs are out.  

FUZES USED WITH

 AN-M100 Series normally.  

ARMING TIME

 Instantaneous setting, 330 vans revolutions.

 

 .1 sec. delay setting, 220 vans revolutions.

VANE SPAN

 6" (2 vanes)

MAX. BODY DIAMETER

 2.7"

OVERALL LENGTH

 7" (with booster)

MATERIAL

Cadmium plated steel with some brass parts

GENERAL:

The AN-M103 is being replaced by the AN-M103A1 which differs in that the striker block has been drilled and tapped to accomodate an arming screw of a greater diame-ter. The hole for the arming screw joins that of the arming stem. In this way it is pos-sible for the collar on the arming stem, under pressure of the arming stem spring, to bear against the base of the widened arming screw. In the earlier production of the AN-M103A1, a threaded sleeve was fitted and staked to the original arming screw of the AN-M103 to form the new widened arming screw. In the later productions, the widened arming screw is a single solid piece. In other respects the AN-M103 and AN-M103A1 are similar.

The purpose of modifying the AN-M103 as described above is to eliminate the possi-bility of accidental detonation in crash landings, and thus make it safe for carrier usage. In some cases during crash landings, upon initial impact, the vane cup and head of the AN-M103 were sheared off, allowing the arming stem to jump out, and the slider to align itself below the firing pin. On subsequent nose impact the fuze fired. The AN-M103A1 increases the safety primarily because the arming stem cannot jump out on accidental shearing of the vane cup assembly, as the arming screw overlape the arming stem collar.

OPERATION:

The operation of the AN-M103A1 is the same as that of the AN-M103 except that in the former, the arming stem, in addition to bearing against the internal gear, has its collar bearing against the arming screw. As the arming screw moves out, the arming stem follows it until the arming stem collar bears against the setting pin for delay action, or top of cavity for instantaneous action. In the event of a crash landing, if the vane cup and head of fuze shear off, the arming stem is held in place by the arming screw; hence, the slider cannot move over and the fuze will not fire.

REMARKS:

Air Travel to arm the AN-M103A1 is the same as the AN-M103. This may be explai-ned by the fact that the AN-M103 has 28 double threads per inch on the arming screw while the AN-M103A1 has 14 single threads per inch.

AN-M103AN-M139A1, AN-M140A1, M139, M140