CONSTRUCTION. The outer casing consists of a thin sheet steel cylinder with a single running the entire length of the case. Two sheet steel strengthening bands are fitted externally to the steel cylinder. Each strengthening band is secured in position by a nut and bolt. A cardboard cylinder within the steel cylinder forms a lining for the pyrotechnic composition. A cylindrical wooden block is housed in the upper portion of the cardboard cylinder. The wooden block, cardboard cylinder, and a steel cylinder are secured toget-her by means of three small panel pins. A pressed steel cover cap fits over the upper portion of the cardboard cylinder and wooden block protruding beyond the steel cylinder. The cover cap is designed to permit entry of the fuze body but engages the flange on the upper portion of the fuze body. The cover cap is secured to the cardboard cylinder and wooden block by means of three panel pins. (See fig. 91.)

The steel housing for the arming vane is secured to the cover cap by means of two nuts and screws, the screws being fitted with distance pieces. The wooden block is counter-sunk at two points to accommodate the screw heads. The flanged portion of the arming vane housing has eight vent holes. The lower cylindrical portion of the housing has a slot for observing the position of the arming spindle of the fuze; it is also recessed at two points on the lower surface to permit the housing to fit over and engage the upper sur-face of the projecting lugs of the fuze. The upper cylindrical portion of the housing is drilled at four points for housing the safety wire; it also has a recess for accommodating the arming wire attachment lug on the arming vane. The arming vane consists of a circu-lar sheet steel plate, two segments of which are bent over in opposite directions at an angle 45°. Ten inches of light steel cable is secured to the arming vane and the arming spindle of the fuze. The arming vane is a loose fit within the arming vane housing. The steel cable is stowed below the arming vane, the latter being retained in position by the safety wire.

The fuze is a normal (67) fuze fitted with a bakelite gaine case filled with gun-powder. It is believed that a bursting charge is incorporated in the lower portion of the pyrotechnic filling in order to discourage attempts to extinguish the target marker on the ground.

OPERATION. On release from the aircraft and sebsequent opening of the container, the safety wire is withdrawn presumably by means of a static cord. Alternatively the safety wire may be withdrawn prior to stowing the marker in the container. The current of air passing through the vent holes in the arming vane ejects the arming vane. By reason of its shape, the arming vane is rotated as the missile falls. This rotation unscrews the ar-ming spindle of the fuze thus permitting the clockwork mechanism of the fuze to func-tion.

The missile falls to the ground and once the pressent delay on the fuze has expired, the gunpowder in the gaine case is ignited. The resulting flash ignites the pyrotechnic com-position and ejects the cover cap, fuze, and arming vane housing.

The pyrotechnic filling burns with a strong greenish flame for approximately 3 1/2 minu-tes. A slight explosion occures when the bursting charge is ignited.

Figure 91 – Mark 3 Single Unit Ground Marker (Green)