Driving down New Highway, which skirts the perimeter of Farmingdale, Long Island’s, Republic Airport, on the still-warm, crystal-blue Labor Day morning in 2006, and glimpsing the tails of the World War II B-24 Liberator, B-17 Flying Fortress, and B-25 Mitchell bombers, I had once again realized that the Collings Foundation’s annual Wings of Freedom fleet rotation, more than any other year, had transformed the general aviation field into an early-1940s pocket of time, a hub of medium and heavy bomber operations.
The aircraft intended for my mission, the North American B-25 Mitchell registered 130669 “Tondelayo” and wearing its drab olive-green livery, had been the third parked on the ramp of the American Airpower Museum, both an historical and symbolic position relative to the two heavier, longer-range aircraft which had been preceded it driveway bollards edinburgh.
Resulting from a 1938 Air Corps requirement for a twin-engined, medium-range bomber which could fulfill niche roles its larger, quad-engined counterparts had been unable to, and tracing its lineage to the B-10, the B-12, the B-18, and the B-23, the B-25 itself, named after the US Army Air Corps Officer General Billy Mitchell, had been infused life as a self-funded project by North American Aviation in the form of the NA-40-1. The 19,500-pound prototype, featuring a narrow fuselage with a green house cockpit; a straight mid-wing; two, 1,100-horsepower R-1830 piston engines; an angular, twin vertical tail; and a tricycle undercarriage of single wheels, had first flown in January of 1939, but a power deficiency had necessitated the retrofit of 1,350-horsepower R-2600s. Although the modified version, designated NA-40-2, had offered superior performance, it crashed after a two-week test program.
Its NA-62 successor, which had been extensively modified, featured a wider fuselage which in turn increased the now lower-mounted, constant root-to-tip dihedral mid-wing span, 1,700-horsepower R-2600-9 engines, square-geometry vertical tails, and a 27,000-pound gross weight. Approved in September of 1939, this version, designated the XB-25, first flew in prototype form on August 19 of the following year.
Initially delivered to the Army Air Corps, the aircraft demonstrated directional stability deficiencies, resulting in the outer wing mounting redesign with the tenth aircraft off the production line, which reduced the engine-to-wing tip dihedral and gave it its characteristic gull-wing profile.
The B-25 Mitchell, in production form, appeared with an aluminum alloy, semi-monocoque fuselage, constructed of four longerons, which produced a 53.6-foot overall length. The cantilever, all-metal, mid-mounted wings, comprised of a two-spar, fuselage-integral center section housing integral fuel tanks and two outer, single-spar sections with detachable wing tips, featured sealed ailerons with both fixed and controllable trimming tabs and dual-section, hydraulically-operated, trailing edge slotted flaps divided by the engine nacelles. Spanning 67.7 feet, they sported a 609.8-square-foot area. Powered by two 1,700-horsepower, Wright-Cyclone two-row, 14-cylinder, air-cooled R-2600 piston engines housed in aerodynamic nacelles which traversed the wing chord and turned three-bladed, constant-speed, 12.7-foot, full-feathering, anti-icing Hamilton Standard propellers, the aircraft could climb to 15,000 feet in 11.3 minutes and attain a maximum speed of 303 mph at 13,000 feet. The cantilever twin vertical fins and rudders, fitted with fixed and controllable trimming tabs, had been modified with rounded tops and yielded a 16.5-foot aircraft height. The tricycle, single-wheeled, hydraulically-actuated, aft-retracting undercarriage, the first such configuration employed by a US bomber, featured aerodynamic door covers over all three wheel wells in both the extended and retracted positions, while the main wheels were equipped with hydraulic brakes. The aircraft, with a 21,100-pound empty weight, had a maximum gross weight of 33,500 pounds.
Several versions had been produced. The first of these, the B-25A, incorporated pilot armor and self-sealing fuel tanks, while its successor, the B-25B, introduced two electrically-operated Bendix turrets, each of which replaced the midship and tail guns and featured two.50 caliber machine guns. Entering service in 1941 with the 17th Bomb Group at McChord Field near Tacoma, Washington, the aircraft, whose production run totaled 120, also featured a separate photographic station between the upper turret and the tail and a shortened, 54.1-foot length.
Powered by two 1,700-horsepower Wright R-2600-13 engines, the B-25C, the third version, introduced an autopilot system and external racks which could carry eight 250-pound bombs, and a later fuel capacity increase to 1,100 gallons. Of the 3,909 build, 1,619 had been produced in Inglewood, California, while 2,290 had been assembled in Kansas City, Kansas, under the B-25D designation.
The singular B-25E and -F variants were intended as test vehicles of wing and tail anti-icing systems, while the B-25G replaced the glazed nose with an armored one, the latter containing two.50 caliber machine guns and one 9.6-foot-long, 900-pound, cradle-mounted, M-4 cannon capable of firing 23-inch, 15-pound shells. Although its armament had otherwise adhered to the B-25C standard, its bomb bay could accommodate an aircraft torpedo. The variant, operated by a crew of four and featuring a 50.10-foot overall length, enjoyed a 405-unit production run.
The B-25H, with significantly increased armament, featured four.50 caliber machine guns in the metallic, armored nose, and a further four on the side, arranged in pairs; a repositioned top turret, now located in the roof of the navigator’s compartment; the removal of the ventral turret; enlarged, aft-wing,.50 caliber machine gun waist positions; and a tail gun station with two further.50 caliber machine guns. As World War II’s most extensively armed design, it could attain 293-mph speeds at 13,000 feet and had a 23,800-foot service ceiling.