Beautiful, but late…

It might come as a surprise to many that when Japan attacked Pearl Harbor on Dec. 7, 1941, Japan not only had an outstanding carrier air force but also probably the most effective long range, land-based bomber force in the world at that time.

These twin engine, long range bombers ranged across the Pacific wreaking havoc on Allied installations and warships through much of 1942, but by the end of that year they began to rapidly lose their effectiveness.

The reason the Japanese bomber force lost out was because its virtues – long range and good bomb load – were achieved by eliminating self sealing fuel tanks and most defensive armament. Once Allied fighters appeared in force, they began to decimate these bombers, which quickly became named “Type 1 Lighters.”

The Japanese leadership watched the heavy losses in their lightly armored bomber force with dismay and, at the same time, saw the four engine American B-17 Flying Fortresses operating over Japanese territory with close to impunity. The message was clear – what Japan needed to continue its land-based bomber operations was a new, tough four engine bomber similar to the B-17.

Several Japanese aircraft companies began to develop such an aircraft, but the most promising was the Nakajima design, which the company began to work on in February 1943. The bomber, the G8N1 Renzan (Mountain Range), was powered by four 2,000 horsepower Nakajima Homare 24 radials with turbosuperchargers, which were expected to give it a top speed of more than 300 knots and a cruising speed of more than 200 knots. With a ton of bombs it would have a range of more than 4,000 miles and a service ceiling of about 30,000 feet.

While this performance was impressive, the most important part of the G8N1 was its defenses – a full suite of armor for the crew, self sealing fuel tanks and very heavy defensive armament. This consisted of three power-operated turrets in the dorsal, ventral and tail positions, each with two Type 99 20 millimeter cannons providing almost twice the punch of the standard American bomber turret with twin .50 machine guns. The Renzan also carried two Type 2 .50 machine guns in a power-operated nose turret, and single Type 2 .50 machine guns in the left and right waist positions.

The completed Renzan was a beautiful aircraft – a mid wing monoplane with a single rudder, tricycle landing gear and a laminar flow wing. When its flight tests began in October 1944, it showed good performance, except for minor problems with the turbosuperchargers, but by then its time had long passed as Japan was now on the defensive. Additionally, the whole program was severely hampered by a shortage of materials, in particular aluminum, brought about by the U.S. Navy submarine blockade. The program was also severely stressed when U.S. Navy carriers began to attack airfields on the Japanese home islands.

The Navy crews’ reports of a new four engine bomber to U.S. intelligence resulted in the G8N1 being given the Allied code name “Rita,” and at least one of the prototypes was shot down by marauding Navy Hellcats. In the end, the total production of the G8N1 – including prototypes – amounted to just seven aircraft, of which only four were flown. One was converted to a missile carrier for the Okha (“Cherry Blossom”) rocket powered kamikaze, but no test flights were made.

After the war, the fourth prototype was shipped to the United States for a brief evaluation, still in the “burnt orange” color scheme the Japanese used on experimental aircraft.

When compared to the American B-17G, the Rita was about the same size but much heavier and with much more power – 8,000 horsepower to the B-17’s approximately 4,000 horsepower. This extra power gave the Japanese aircraft roughly the same performance, though the B-17G had a heavier bomb load.

Also, by the time the first G8N1 was flown, the B-17 was old technology, replaced by the much more advanced B-29, which began combat operations over Japan while the first prototypes of the Renzan were being tested.

For questions or comments, contact Dr. Michel at marshall.michel@ramstein.af.mil.