This model torpedo has been recovered with three different types of warheads. Two of the warheads, designated by the Japanese as Type 91, Modification 3, and Type 91, Modification 6, are of normal design and differ mainly in the length and weight of charge. The third warhead, designated Type 3, is equipped with two exploders, one of a new type, and differs radically from the Modification 3, torpedo has a single speed and leaves a visible wake.

The physical characteristics of the torpedo are as follows:

Length Overall – With Modification 3 Warhead - 17'4".

With Modification 6 Warhead - 18'9".

With Type 3 Warhead - 18'.

Length of Warhead – Modification 3 - 4'9".5.

Modification 4 - 6'2".5.

Type 3 - 5'5".5.

Length of Airflask – 7'4".

Length of Afterbody – 5'2".5 (Including Tail).

Diameter – 17".7.

Total Weight – Modification 3 - 1800 lbs.

Modification 6 - 2100 lbs.

Type 3 - 1800 lbs. (approx.)

Charge – Modification 3 - 522 lbs. Type 97 explosive.

Modification 6 - 812 lbs. Type 97 explosive.

Type 3 - 493 lbs. Type 97 explosive.

Tail Fins – 8.

Range/Speed – With Modification 3 Warhead - 3300 yards at 42 knots.

With Modification 6 Warhead - 3100 yards at 42 knots.

With Type 3 Warhead - Range unknown at 42 knots.

Depth Setting – 6'6 to 59'4.

Exploder – With Modification 3 and 6 Warheads - Type 90, Model 2, bail, impact-inertia, in pocket on top centerline of warhead.

With Type 3 Warhead - One Type 90, Model 2, bail, impact-inertia, in pocket on bottom centerline of warhead; one "Hydroplane Exploder", bail, impact, in poc-ket on top centerline of warhead.

Operation

The Type 91, Modification 3 torpedo equipped with either Modificaion 3 or 6 warhead operates in the same manner as the Type 91, Modification 1 described on the preceding pages.

As the Type 91, Modification 3 torpedo equipped with the Type 3 Warhead, travels through the water, a small hydroplane attached to a towing cable is released from the warhead and streams above and shlightly abaft it. The drag of the hydroplane on the towing cable arms the exploder. Impact of the hydroplane with the target automatically releases if from the towing cable. The release tension on the towing cable actuates the exploder, firing the charge.

The Type 90, Model 2 exploder arms and fires in same manner as described for the Type 91, Modification 1 torpedo.

The hydroplane exploder allows the torpedo to be set at depths that will insure deto-nation under the target, rather than on the side. It should fire at the end of its run due to the release of tension on the hydroplane towing cable.

Safety Precautions

This torpedo must be considered to be dangerous if found in shallow water or on a beach. Movement of the hydroplane towing cable may explode the charge. Safety pre-cautions described under Torpedo Type 91, Modification 1, should be observed.

Figure 35 – Type 91 Modification 3 torpedo with the hydroplane exploder. This hydroplane streaming above the torpedo allows it to detonate beneath the target.