Thwarting Japanese Torpedo Planes

Type 6 Mark 4 Mod 3 Airborne Radar

Production: About 2000. Available from 1942-8 and Installed on a number of G4M “Betty”, H8K “Emily”, and B5N “Kate” aircraft, particularly after 1944.

Wavelength 200 cm
Pulse length 10 microseconds
Peak power 3 kW
Range 75 nautical miles (130 km)
Antenna Various; see description below
Display A scope
Weight 240 lb
110 kg

The antenna configurations seems to have varied with platform. The installations on multi-engine aircraft used a four-element Yagi antenna in the nose for the transmitter and two reflected dipoles on the wings for the receiver. On torpedo bombers, where a nose antenna was impractical, a fuselage dipole array was apparently used instead. The fuselage dipole array had the significant weakness that it could not search the area head ahead of the aircraft, so that aircraft equipped with the radar had to approach a target obliquely to maintain radar contact.

The radar was plagued by corona discharge at high altitude and by sea return. The Yagi antenna was less susceptible to this effect.

At his ornate palace in downtown Tokyo, Emperor Hirohito, impeccably attired in formal clothing, was ready to receive a delegation of generals, admirals, and top government officials. Formal dress was reserved for special occasions. Hirohito, the father of six, customarily shuffled about the long halls and high-ceilinged rooms of the sprawling palace clad in old casual clothes, scuffed shoes, and in need of a shave. It was October 11, 1944.

Escorted into Hirohito’s presence, the visiting delegation, subdued and with hats in hand, confessed their “failures” to the introverted emperor, who for nineteen years had been struggling to make a success of the throne he had inherited at age twenty-five from his father.

Although the Allies were closing in on Japan, the warlords assured Hirohito that the bleak picture would soon be reversed. A high-level official in the Foreign Office of the Soviet Union, supposedly an ally of the United States and Great Britain, had tipped off the Japanese ambassador in Moscow that the Americans were preparing to invade the Philippines. At that time, a plan code-named Sho-Go 1 (Operation Victory) would inflict a crushing defeat on the fleet and army of General Douglas MacArthur, the delegation told the emperor.

In the early-morning darkness of October 20, a mighty armada of seven hundred U. S. ships slipped into Leyte Gulf in the central Philippines. On board the cruiser Nashville was Douglas MacArthur, perhaps America’s most popular general on the home front, who had been run out of the Philippines by overwhelming Japanese forces in the spring of 1942.

At 8:00 A. M., warships offshore loosed a thunderous barrage; then assault troops of Lieutenant General Walter Krueger’s Sixth Army stormed ashore on Leyte, a large, mountainous island.

Forty-eight hours later, Admiral Soemu Toyoda, chief of the imperial Combined Fleet, was at his headquarters in the Naval War College putting the final touches on Sho-Go I. His planning was aided by a flagrant American security lapse-an uncoded radio message picked up by Japanese monitors gave Toyoda the deployment of the 221 U. S. warships operating in and around the Philippines.

Toyoda was convinced that a new secret radar development by Japanese scientists would result in colossal damage to the invasion fleet. Installed in the cockpits of Japanese torpedo planes and used for aiming the lethal “fish” radar had been created with a frequency below the lowest frequency of the electronic jammers in the U. S. fleet. Therefore the pilot could aim and fire his torpedo unencumbered by the jamming of his radar by the Americans.

Only a few hours after the decisive battle of the Pacific war had erupted at Leyte Gulf, General MacArthur was in a barge returning to the Nashville from an inspection ashore. As the little craft burrowed through the green waters, someone shouted, “Look!” and pointed a finger toward the sky. A Japanese torpedo plane flew low over the barge and headed for the light cruiser Honolulu. Called the Blue Goose by her crew, the ship was standing by for instructions to bombard targets onshore.

The Blue Goose had led a charmed life. She had been involved in many battles and escaped unscathed each time. Incredibly, she had never lost a man due to accidents or enemy action.

Soon after zooming past MacArthur’s barge, the Japanese plane dropped its torpedo into the water; the torpedo raced directly for the Honolulu. No American knew that this was one of the aircraft equipped with the low-frequency radar, so the electronic jammers on the ship failed to blur the pilot’s aim.

There was an enormous explosion, and the Blue Goose shook violently. Lady Luck had finally turned her back on the cruiser: sixty officers and sailors were killed, and scores of others were wounded.

Japanese torpedo-plane attacks continued and became a menace to the fleet. So an urgent plea was sent to the Pentagon near Washington, D. C., asking for help. The request was promptly turned over to the General Electric Company (GE), whose scientists plunged into the task of developing a countermeasure for the Japanese torpedo-plane radar.

Although a creation of this intricacy, even in wartime urgency, would customarily take many months, in a near-miracle, the GE specialists developed a new low-frequency design within twenty-four hours. Fifty of these devices were turned over to the navy in only a weeks time from the original request.

Within hours, the devices were on an airplane bound for the Pacific, where they were installed on ships around the Philippines while what came to be known as the Battle for Leyte Gulf was still raging.

Soon reports began arriving at the Pentagon that told of the success of the equipment. When the ships turned on the new electronic jammers, Japanese torpedo planes often were seen wavering from their courses and finally turning back, unable to find the targets on their blurred radar screens.

American warship skippers authorized operators of the electronic jammers to paint a small Japanese flag on their transmitters after each successful action of this type.

It had been the greatest naval engagement ever fought with regard to the number of ships and airplanes involved on both sides and the magnitude of the ocean surface covered -almost twice the size of the state of Texas. The Japanese Fleet had been virtually destroyed.

Playing a key role in the American victory had been the behind-the-scenes effort of the GE scientists in their amazingly rapid development of a countermeasure against the new-type radar in the Japanese torpedo planes.

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