North American's PBJ
Don't call it a "Blue B-25" in earshot of a Marine!
by Randy Wilson
Copyright © 1997 by the Confederate Air Force and Randy Wilson. All rights reserved.
North American Aviation's B-25 "Billy Mitchell" medium bomber saw action with U.S. and Allied air forces almost everywhere during World War II. But mention its service with the U.S. Navy, and most think of the dramatic launch of 16 Army B-25s from the deck of the USS Hornet on April 18, 1942, in America's first strike at the Japanese homeland, lead by Lt. Col. James Doolittle. To protect the Hornet from attack and further puzzle the enemy, President Roosevelt announced that the raid had been launched from a mysterious base called "Shangri-La."
Of course, the B-25s couldn't land on an aircraft carrier or could they? On November 15, 1944, a specially modified Mitchell did just that, making arrested landings and catapult takeoffs aboard the appropriately named USS Shangri-La. But this Mitchell was a PBJ, the Navy's designation for the North American B-25 patrol bomber. Although the Navy dropped the idea of flying PBJs from carriers, they went on to see action with the U.S. Marine Corps.
For years before America's entry into the Second World War, there was a war of a different sort between the air forces of the U.S. Army and Navy. The Navy wanted long-range multi-engine land-based reconnaissance and patrol aircraft but the Army Air Corps regarded all land-based bombers as an Army operation. In late 1942, however, this situation was changed by an unusual "deal."
The Army saw Boeing's new B-29 Superfortress as a major weapon in the war with Japan, and its production would occupy Boeing's Seattle and Wichita plants, plus Bell's Marietta facilities. Boeing had another plant in Renton, but it had been built by the Navy to produce Boeing PBB "Sea Ranger" flying boats. As American forces captured island bases in the central and southwestern Pacific, the need for flying boats and seaplanes was greatly reduced. Thus, the Army proposed to trade its North American Kansas City plant, which was building B-25s, in return for the Navy's Renton plant. The deal was struck, and the sole XPBB-1 Sea Ranger built became "The Lone Ranger."
In February 1943, the first B-25C and D models were delivered to the Navy and given the designation PBJ-1C and PBJ-1D respectively. Army model letters was used to designate all subsequent PBJ variants. The Navy's Mitchells were to be used in the reconnaissance, anti-shipping and close support roles and flown by Marine Corps crews. The first Marine bombing squadron, VMB-413, was organized in March 1943, and a number of its PBJ-1s were fitted with search radars mounted in place of the lower turret.
Since most Marine Corps pilots and crews were operating single-engine fighter and attack aircraft, VMB-413 acted as a training squadron for air and ground crews in the twin-engine Mitchell. By October 1943, seven more squadrons, VMB-423, 433, 443, 611, 612, 613 and 614, had been equipped with PBJ-1s to form the first Marine Medium Bombardment Group. First to see action in the Pacific was VMB-413, which arrived in January 1944 and entered combat in March of that year.
The squadron flew its first combat missions from Sterling Island, flying both day and night bombing strikes against targets in the Rabaul and Bougainville areas. Having to develop new tactics, the Marine PBJs suffered heavy losses at first. However, the squadron's effectiveness was noted in a commendation from the Army commander of aircraft in the Solomons area (ComAirSols), Brig. General William A. Matheny:
In late 1943, newer PBJ-1Hs were delivered, fitted with a 75mm cannon mounted in the nose and additional forward-firing .50 caliber guns. These were followed by PBJ-1Js in the spring of 1944. Those H models fitted with radar had a radome in the nose, while the PBJ-1J's radar was mounted on the right wingtip, allowing either a clear bombardier nose or solid gun nose to be fitted. In addition, both models could carry eight air-to-ground High-Velocity Aircraft Rockets (HVAR) mounted under the wings. As described below, the rockets proved more effective than the slow-firing 75mm gun, which rarely got off more than 3 or 4 rounds during a pass on a target.
VMB-612, commanded by Lt. Col. Jack Cram, was selected for special training in night attacks on enemy shipping, using radar to locate and attack the targets. In addition to conventional bombs and torpedoes, the new 5-inch HVAR rockets were tried and found to be highly accurate and effective. By flying level about 300 feet above the water and correcting for wind and temperature variations, Cram's pilots learned to judge the rockets range. In one practice attack on a small island only 200 feet long by 100 feet wide, the squadron fired over 250 HVARs and scored 56 percent hits.
In November 1944, VMB-612 was stationed on Saipan, but the nearest shipping targets were near Iwo Jima and Chichi, 630 and 750 miles to the north, respectively. Cram's squadron stripped their PBJs of excess weight, including the upper turrets and cheek guns, and carrying 1520 gallons of fuel, successfully flew missions which lasted 10-12 hours.
From Saipan, VMB-612 moved to Iwo Jima in April 1945, where it could reach the coast of Japan during its nigh-time anti-shipping strikes. Cram's squadron claimed 7 ships sunk and 80 damaged during missions from Saipan and Iwo, with a loss of three PBJs in combat. On July 28, 1945, VMB-612 departed for its next base on Okinawa.
The HVAR rockets shown to be so effective by VMB-612 were an early product of the Naval Ordnance Test Station (NOTS) established at China Lake in 1943. Working with civilian scientists from the California Institute of Technology, the NOTS developed aircraft rocket weapons, including the big 11.75-inch "Tiny Tim", intended for attacks on enemy bunkers and other protected targets. Being the "rocket experts", VMB-612's PBJ-1Js were fitted with mounts for two Tiny Tims, one on each side of the fuselage, above the bomb bay doors. Cram's pilots flew three night missions with the big rockets against targets in southern Japan on August 11, 12 and 13, 1945, in the last days of the war.
Just over 700 PBJs were delivered to the Marines, 50 PBJ-1Cs, 152 Ds, 1 or 2 Gs, 248 Hs and 255 PBJ-1Js. Performance of the PBJ-1J powered by two Wright R-2600-29 1,700 horsepower engines included a top speed of around 275 mph at 12,500 feet, a cruse of 230 mph and normal range of 1,560 statute miles. Service ceiling was 20,600 feet with a normal gross weight of 34,000 pounds. A typical PBJ-1J was armed with twelve 0.50 caliber machine guns and up to 4,000 pounds of bombs, a Mark 13 aerial torpedo or 8 HVAR rockets.
Marine bomber squadrons lost 45 PBJs to all causes, along with 173 officers and men. Given the unusual reasons for choosing the Army-designed North American bomber, it is hard to imagine an aircraft more effective than the PBJ in the hands of its U.S. Marine Corps pilots and crews.
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