An aircraft laid, contact, drifting mine used as an offensive weapon against surface craft and designated by the Japanse as "K-2". The mine dirfts approximately 6' under the surface of the water, supported from its buoyant tail section by a short length of cable. The tail has the appearance of an oil drum floating vertically on the surface when the mine is armed. After an unknown length of time the JI scuttles itself.

The physical characteristics of the mine are as follows:

Case

Shape – Cylindrical, 14" diameter.

Color – Black.

Material – Steel.

Length (including tail) – 6'11".

Length (without tail) – 4'1".

Charge – 123 lbs. cast Type 98 explosive.

Total Weight – 300 lbs.

External Fittings

Horns – Three, switch, equally spaced around top of mine.

Suspension Lug – One, on the top center line of the mine.

Detonator Pocket – 4".25 in diameter, 180° around the case from the booster poc-ket.

Filling Plug – 3".75 in diameter, in the nose of the mine.

Soluble Plugs – Two; one on the top center line 4" from the after end of the mine and the apex of the tail.

Tail Release Mechanism – On the top center line of the mine, 2" from the after end.

Operation

As the mine is launched from the aircraft arming lanyards withdraw safety forks from the tail release and booster release mechanism. The booster is released under spring pressure and is permanently housed over the detonator while the mine is still in the air. On its initial plunge into the water, the hydrostatic switch operates, closing and locking the circuit from the battery to the horns. Positive buoyaney of the tails brings the mine back to the surface and its floats nose downward with the tail fins partly out of the wa-ter. Dissolution of a soluble plug release the mine from the tail, and the case sinks to the end of the mooring cable. The weight of the case on the cable inverts the tail and it floats base upward on the surface. The strain of the case on the cable also releases the horns, which snap outward in the armed position; and closes a horn safety switch, arm-ing the mine.

The mine fires when one of the horns is bent sufficiently to make a contact and close the circuit between the battery and detonator.

After an unknown period of time the soluble plug in the tail dissolves, flooding the float and allowing the mine assembly to sink.

Safety Precautions

Sinche the horns require only a force of approximately five pounds to bend them, it is possible that the mine may fire on striking the bottom. There are no disarming features if the mine should drift ashore; and movement of the JI on the beach may bend a horn and detonator the mine.

Figure 23 – Mine tyoe JI assembled.

Figure 24 – Type JI floating, fully armed. The buoyant tail piece supports the mine approximately 4 feet below surface.

Figure 25 – Type JI floating unarmed.