M135, M136, M135A1, and M136A1 (Nose Clockwork Aerial Burst)

Bombs

Functioning

Armed condition

Fuzes used with

Arming time

Vane span, inches

Body diameter, inches

Over-all lenght, inches

Material

Upper part of body is aluminum alloy; lower part, cad-mium-plated steel

General: These fuzes are a combination of the Nose Clockwork Aerial Burst Fuze M111A2 and the Nose Mechanical Impact Fuze AN-M103, in which the former fuze has been assembled to a modified body and booster portion of the Fuze AN-M103. The sett-ing pin of the AN-M103 has been removed, and in its place the spring-loaded lower arm-ing pin has been inserted. The lower arming pin olds the detonator carrier out of line with the firing train until the arming wire is pulled.

The Nose Clockwork Aerial Burst Fuze M135 incorporates a time setting which can be adjusted to the nearest 0.1 second, and the fuze will fire accurately within plus or minus one second; time calibrations are made for every half second, with a 10-division vernier scale located on the non-rotating part of the fuze for setting to the nearest 0.1 second.

The M136 incorporates a time setting which can be adjusted to 0.2 of a second, and the fuze will fire accurately within plus or minus 0.3 second. The greater accuracy of the M136 is achieved by an improved clockwork mechanism. This fuze was developed to pro-vide greater accuracy, presupposing that a method can be devised for accurately mea-suring the altitude of release.

Operation: Prior to loading the fuzed bomb into the plane, the time setting is made and the time set screw tightened. The arming wire is withdrawn as the bomb is dropped, and the vanes start to rotate. The arming pin is ejected, and the time mechanism starts to operate, the lower arming pin being simultaneously ejected, allowing the spring-loaded detonator carrier to move over into the armed position. After approximately 750 feet of air travel, the safety block is released from the fuze. After the set time has expired, the firing pin will be freed and its spring will force it into the primer and detonate the bomb.

The bomb may detonate if it strikes a target prior to complete functioning of the time mechanism, provided the arming wire has been withdrawn, in which case the firing pin would shear the rather delicate levers obstruction it.

Remarks: Effective use of these fuzes in G.P. bombs presupposes that a method can be devised for accurately measuring the altitude of release.

The round knurled locking screw has been replaced in current production with a wing-nut typem and replacement wing nuts are being sent to the field. This change was made so that ordnance personnel can get a good grip on the nut and eliminate the possibility that the setting might slip and cause either premature or late functioning.

The Nose Clockwork Aerial Burst Fuze M135A1 and M136A1 are the same as the M135 and the M136, except that they incorporate a lower time limit of 10 seconds instead of 5 seconds. The minimum setting time was increased to prevent any possibilty of damage to the plane by the bomb fragments. The M135A1 and the M136A1 will replace the M135 and the M136 respectively, when available. It is recommended that a minimum setting of 10 seconds be used for all M135 and M136 fuzes now in the field.

Figure 338. Aerial Burst Fuze M135A1