Description
These signals are employed as follows:
To determine the drift of the plane from which the signal was dropped.
To mark the initial point of contact with a submarine.
To mark an object to which an aircraft desires to call attention of a surface vessel.
To determine the wind direction before landing.
To mark the landing deck on aircraft carriers for night landings.
To mark the location of the surface of the water for emergency night landings.
The Night Drift Signal AN-Mk 4 has an ogival shaped, die-cast nose with a lug on one side so that the signal will turn and not strike the bottom in shallow water, while the Night Drift Signal AN-Mk 5 Mod 1 has a Hat die-cast nose. In both cases the die-cast nose contains a water-impact fuze. The bodies of both signals are made of hollow wooden cylinders, with one end tapered, on which the tail assembly is mounted.
The pyrotechnic mixture is formed into pellets approximately four inches long and 1.25 inches in diameter, with a 0.022-incli hole eon- centric with the longitudinal axis through which the delay fuse passes. One pallet is used in the AN-Mk 4, and three pellets are used in the AN-Mk 5 Mod 1. The pellets are enclosed in a pyrotechnic tube to keep the hygroscopic material from absorbing moisture through the wooden body. Originally, pure tin was used for this purpose; but in recent lots lead and zinc have been substituted. The nose end of the signal is closed with a paraffin-treated sealing disc, while the tail is sealed with a metal cap.
These signals may be used for day signals, but under certain conditions observation is difficult. The Mod 2 is a moisture-proofed version of the Mod 1.
Functioning
When launched from aircraft, the drift signal falls nose down. On impact with the surface of the water, the paraffined paper sealing disc is broken and the water drives the firing pin up against the primer. The flame from the primer ignites the time fuse which runs the length of the hole through the center of the pyrotechnic pellets in order to give the drift signal enough time to return to the surface and right itself. The time fuse ignites a length of quick match which, in turn ignites the starting mixture and then the pyrotechnic pellets. The gases evolved by the pellets break open the pyrotechnic tube and force out the cap which seals the discharge tube in the tail. A bright (lame 12 to 15 inches high and a white smoke are produced. These are visible for six to seven miles on a clear night.
See Also
Aircraft Float Light Mk 6 Mods 0-2
Source(s)
OP 1664, Volume 1 - US Explosive Ordnance (1947)
USNBD - Bombs and Fuzes, Pyrotechnics (1945)
TM 9-1904, Ammunition Inspection Guide (1944)
