Historical Perspective

Frontiers August 2015 Issue

HI STORICAL PER SPECTIVE Starring role North American’s legendary B-25 Mitchell bomber turns 75 by Michael Lombardi It was one of the most daring raids of World War II . On April 18, 1942, just four months after the attack on Pearl Harbor, 16 B-25 bombers took off from the U.S. Navy aircraft carrier Hornet to attack the Japanese homeland. Named for its commander, Lt. Col. James “Jimmy” Doolittle, the Doolittle Raid over Tokyo and other cities in Japan did little damage to the industrial targets that were hit. But the effect on the national will of both countries was significant. The raid gave a much needed morale boost to Americans in the wake of the painful blow inflicted on the U.S. Navy at Pearl Harbor, and it placed doubt in the minds of Japanese war planners. It also marked the combat debut of North American Aviation’s B-25 Mitchell, which would go on to be one of the most versatile, successful and produced medium bomber of the war. The design of the B-25 began with the North American NA-40, a light bomber prototype that competed against the Douglas DB-7 (A-20). The NA-40 did not lead to a production contract but did serve as a basis for design studies that were initiated in March 1939 in response to the Army Air Corps wanting a medium bomber. In September 1939, North American, a Boeing heritage company, was awarded an initial order for 184 of the bombers, which had been named “Mitchell” in honor of Army Air Corps Gen. William “Billy” Mitchell, a military aviation pioneer and outspoken advocate for U.S. air power. On Aug. 19, 1940, 75 years ago this month, pilot Vance Breese and co-pilot Roy Ferren took the B-25 up on its first flight. 10 Boeing Frontiers Although designed to be a conventional level-flight bomber, the B-25 would go on to excel in the low-level attack role. U.S. Army Air Force Maj. “Pappy” Gunn and North American Aviation field service representative Jack Fox worked together to field-modify B-25s into a weapon that would be effective against enemy shipping and airfields, mounting multiple .50-caliber machine guns in the nose. The modification was so devastating to enemy shipping, in particular during the battle of the Bismarck Sea, that the concept made its way back to the North American factory, where engineers designed a production version designated B-25G. This model went a step further, with a 75 mm cannon, the same used on an M-4 Sherman tank. Further modifications resulted in the B-25H, which had a lighter version of the 75 mm cannon and four .50-caliber guns in the nose as well as twin .50-caliber machine gun pods mounted on either side of the forward fuselage. Adding the firepower of the twin guns in the top turret, the B-25H had an accumulated forward firing power of a 75 mm cannon and 10 .50-caliber machine guns and four more guns in defensive positions. It was the most heavily armed airplane of World War II . The next and final production version was the B-25J, which was built to fly both level-bombing and strafing roles that traded the difficult-to-aim 75 mm cannon for additional machine guns. It had a total of 14 forward-firing machine guns. North American first produced the B-25 at the Los Angeles plant where all A through C models were built, as well as all G and H models. Ground was broken in March 1942 for a second B-25 assembly plant in Kansas City, where all B-25D and B-25J models were built. The B-25 saw combat in every theater of World War II , from the South Pacific to Russia, and from the deserts of North Africa to the skies over Europe. They were operated by the air forces of America’s allies, including Great Britain, Canada, Australia, the Netherlands, the Soviet Union and China. And 700 of the land-based bombers were acquired by the U.S. Navy. In all, North American built 9,817 B-25s between 1940 and 1945. By the end of the war the Douglas A-26 Invader was replacing the B-25 as a medium attack bomber, but the B-25 continued to serve long after the war as VIP transports and training aircraft, many modified by Hughes Aircraft. They served with the U.S. Air Force until 1960. n michael.j.lombardi@boeing.com Illustration: (Above) A B-25H Mitchell bomber cutaway. Boeing Photo: (Right) B-25Cs on North American’s ramp at Mines Field (present-day Los Angeles International); following the Doolittle Raiders, these B-25s would be some of the first to see combat in World War II . Boeing


Frontiers August 2015 Issue
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