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The North American B-25 Mitchell

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The North American B-25 Mitchell

North American B-25 Mitchell Red Bull (The Flying Bulls) flight demonstration at Bucharest International Air Show 2013.


The North American B-25 Mitchell

The North American B-25 Mitchell

By Robert Waldvogel


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.

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.

The B-25J, the definitive and numerically most popular version, had been intended for precision bombing. The aircraft, introducing a bombardier who increased the crew complement to six, reincorporated the glazed nose which had now been provisioned with one fixed and one flexible.50 caliber machine gun. The largest single Mitchell order, for 4,318 B-25s, had been placed on April 14, 1943, and the aircraft, attaining 292-mph speeds at 14,500 feet, could cruise at service ceilings of 25,500 feet.

Between 1941 and 1945, the Army Air Corps took delivery of 9,816 B-25s, 3,218 of which had been produced in Inglewood, California, until 1943, and the remaining 6,608 of which had been produced in Kansas City.

The B-25 Mitchell had several post-war applications. Demilitarized, and designated TB-25, the type, based upon the B-25J, had been converted into a trainer with the installation of an observer's seat in the nose, ahead and below the cockpit; two student seats behind the standard two pilot-instructor positions; and up to five seats in the aft cabin. Of the 400 converted aircraft operated by the US Air Force during the 1950s, the last active-duty staff transport had not been retired until May 21, 1960, although it had continued to be operated by the air forces of Brazil, Canada, Chile, Colombia, Cuba, Mexico, Holland, Uruguay, and Venezuela.

A photographic reconnaissance variant, the F-10, had featured a nose-installed tri-metrogon camera along with other aerial photography equipment, while other non-military roles had included those of executive transport, freighter, and fire bomber.

The aircraft operating my Labor Day flight, a B-25J registered 44-28932, had been produced in August of 1944 by North American Aviation in Kansas City, Kansas. Accepted by the United States Army Air Corps on August 3 of that year, it had served in the US in the AAF Flying Training Command Program, serving 12 different air bases until January of 1959, at which time it had been declared surplus and had been deleted from the US Air Force inventory. Converted into a fire bomber, it had combated forest fires for another 25 years.

Acquired by the Collings Foundation in 1984, and restored by Tom Reilly Vintage Aircraft over a two-year period, the B-25J, the first World War II bomber in the collection, had been flown n air shows in the Boston area for a decade, whereafter it had been ferried to Chino, California, in late 2001, for a secondary restoration by Carl Scholl of Aero Trader, Inc. Subsequently repositioned to Midland, Texas, it was painted by AVSource West in its current Tondelayo livery after the B-25 which had been operated by the Air Apache 345th BG of the 5th Air Force in the Pacific Theater against targets in New Guinea, the 500th BS of the 5th Air Force itself having been the fourth squadron of the 345th BG to have attacked shipping in Vunapope near Rabaul on October 18, 1943. The Tondelayo name had been inspired by Hedy Lamarr's character in the 1943 movie White Cargo and given by the crew of Lieutenant Ralph Wallace. The three-aircraft formation, comprised of the B-25 "Snafu" and flown by Captain Lyle Anacker, the "Tondelayo" flown by Lieutenant Wallace himself, and the "Sorry Satchul" flown by Lieutenant Paterson, had claimed three ships, but avenging fighters had attacked "Sorry Satchul," hitting its port engine and forcing it to ditch, and "Tondelayo," damaging its right engine. Shut down and feathered, it had almost wrenched itself from its mountings because of severe vibration.

Flying over Cape Gazelle toward base, the B-25 duo, maintaining tight formation, had been targeted by some 50 Japanese fighters, "Sorry Satchul" so badly damaged that it had been forced to head for shore and ditch and "Tondelayo," despite its own critical wounds, hovering only 30 feet above the water where it had managed to shoot down five additional enemy aircraft. Limping into base at Kiriwina, the aircraft had subsequently been repaired and patched, receiving a new right wing, engine, propeller blades, and radio equipment. Its crew had been awarded the Silver Star.

Squatting under the forward fuselage and climbing the short ladder into the cockpit section on that Labor Day in 2006, I took the right of the two observer's seats located a foot below, and behind, the cockpit, while the four other passengers entered the aft section, located behind the bomb bay, through the ventral hatch, which had been configured with an aft-facing, three-person bench seat and three individual seats. With the ladder now raised and the dual panel folded across it to form a portion of the integral floor, the B-25J had been secured for engine start.

The two-person cockpit, sporting bow tie control yokes, featured a throttle quadrant with the two engine throttles angled toward the pilot, two propeller-pitch throttles, and two fuel-mixture throttles angled toward the copilot.

Engine start, commencing with the right, number 2 powerplant, entailed turning the master ignition switch and right booster pump on, at which point the Wright R-2600 powerplant rotated and the interior became saturated with deep, vibrating, Hamilton Standard propeller-created noise. Priming and stabilizing them with the throttle to create between 800 and 1,000 revolutions per minute, the captain applied a full-rich mixture, causing them to settle into a throaty, 1,200-rpm idle. The process was repeated with the left, number 1 engine.

Contacting Republic Ground on 121.6 for taxi clearance, and armed with the latest automatic terminal information service data, the twin-finned bomber released its brakes at 0845, the thrust created by its engines, even at idle settings, sufficient to move it forward over the American Airpower ramp and away from the World War II bomber trio. Taxiing parallel to the active runway, 32, the B-25J periodically jolted in response to brake applications, turning on to the run-up area by means of differential power, its slipstream-bombarded twin rudders aerodynamically inducing ground turns. Extending its slotted, trailing edge flaps and advancing its throttles, the medium-capacity bomber, assuredly a giant in comparison to the currently landing Piper Warrior, moved on to the runway's threshold, just as the B-17 had commenced its own taxi roll from the ramp.

Moving into take off position and aligning its nose wheel with the centerline, aircraft 130669 received take off clearance from Republic Tower on 125.2, slowly advancing its two throttles in order to establish initial directional control. Firmly maintaining a straight acceleration roll, the 1,500-horsepower twin-row radials powering the Collings Foundation aircraft exploded with cabin-saturating noise as smooth, steady throttle advancements pinnacled them into their METO settings of 2,600 revolutions-per-minute and 40 inches of manifold pressure. Counteracting wind-induced directional variations with subtle rudder deflections, the captain began applying control column back pressure at 75 knots indicated air speed, the now ground-separated nose wheel producing a lift-generating angle-of-attack. The air speed-created pressure differential, bathing the huge, outstretched, upper wing surfaces in a steady stream of accelerated air, removed all ground restraints and allowed them to peel the gravity-defying aircraft to which they had been attached off the ground at 115 knots. Retracting its tricycle undercarriage at the aircraft's VMC-determined 145-knot speed, and trimming itself into its initial climb, the twin-engined bomber, encased in engine slipstream, rolled into a right bank over Route 110, headed toward Long Island's south shore.

Maintaining a 150-degree heading, the now-graceful flying bird reduced its engine rpm to 2300 and its manifold pressure to 30, moving abreast of the metallic, erector set-appearing Captree Bridge at 1,000 feet, which stretched across the deep blue surface of the Great South Bay from the island to Jones Beach and its signature lighthouse. The azure of the water, seamlessly merging with that of the sky, melded into a surreal dimension, as viewed from the 270-degree-encompassing Plexiglas nose.

The power-to-weight ratio, coupled to its aerodynamic design, had been the key to the highly-maneuverable, medium mission bomber. Unlike its long-range, high-altitude, heavy B-17 and B-24 counterparts, the B-25, at half their acquisition costs, had been intended for interdiction purposes, delivering tactical blows to enemy targets closer to the front. Because of its maneuverability, it had been able to fly low-level, tree-top strafing sorties, where it had remained virtually hidden, and had then dropped parachute-retarding bombs, which had enabled it to escape before detonation. Although it had operated extensively in the Pacific, targeting Japanese air fields from treetop altitudes and skip-bombing enemy ships, it had been used in all theaters of operation, and had been flown by the Australians, the British, the Chinese, and the Dutch. It had been the first bomber to have been lend-leased to Russia.

The most famous B-25 mission, led by Lieutenant Colonel James H. Doolittle and occurring on April 18, 1942, had entailed the launch of 16 aircraft from the aircraft carrier USS Hornet. Of the four candidate aircraft, inclusive of the B-18, the B-23, the B-26, and the B-25 itself, the latter had been chosen because of its performance. The aircraft, B-25Bs modified at the Northwest Airlines maintenance facility in Minnesota to increase their fuel tankage from 694 to 1,141 US gallons, had featured dorsal and ventral power turrets, but had been devoid of tail armament. Loaded on the USS Hornet for the sea journey to Japan, 16 aircraft, each at 31,000-pound gross weights, would take off from the 467-foot deck at a 450-mile distance, close enough to permit them to bomb targets in Tokyo, Yokahama, Kobe, and Nagoya, yet retain sufficient fuel supplies to continue the 1,200 miles to China.

Encountering a Japanese picket boat during the morning of April 18, and fearing imminent attack, Doolittle made the decision to launch the B-25 fleet at an 800-mile distance, or 350 miles further, from land, the first take off occurring at 8:18 a.m., which had been less than an hour after the boat had been sighted. Using strong headwinds and the deck's sea swell-created inclination, the bombers had just been able to accomplish the precarious feat, with the last taking off at 9:21 a.m.

After some four hours of flying, the lead aircraft, flown by Doolittle himself, dropped the first bomb over Tokyo, shortly after which it had been joined by the remaining 15. Although all safely departed Japanese air space, insufficient fuel, caused by the earlier launching, and deteriorating weather, resulted in the crash-landing or abandonment of 15 B-25s in China, while the 16th landed in Vladivostock, where its crew had been captured.

Nevertheless, the mission had been both a technological and operational success, and had elevated troop morale and garnered tremendous notoriety for the aircraft.

Banking left to a 240-degree heading, aircraft 1306669 Tondelayo was carried back over Captree Bridge by its gull, variable-dihedral wings and its three-bladed propellers, crossing over Long Island's south shore. The B-17 Flying Fortress, appearing particularly graceful over the blue surface of the Great South Bay, flexed off of the port cockpit windows. World War II skies had somehow been resurrected that morning.

Fuel burn depended on engine setting: at 180 mph, with the engines turning at 1,700 revolutions per minute and feeding off of 27 inches of manifold pressure, the aircraft burned 120 gallons per hour, while a ten-mph cruise speed increase, attained with a 1,800-rpm/28-inch setting, resulted in a 130-gallon per hour consumption.

Recontacting Republic Tower, aircraft 130699 advised its intention of "inbound for landing" and reduced power, now gravity-induced into its descent profile. Maintaining a 180-mph speed and a 320-degree heading, it extended its trailing edge flaps, which provided air speed control, by means of progressive drag production. Flap settings equally depended on flight phase: 1/4 for take off, 1/2 and 3/4 for descent, and full for landing.

The aircraft's clean stalling speed had been 95 mph, which decreased to 83 mph at maximum gross weight with full flaps and undercarriage at 26,000 feet.

Extending its drag-producing landing gear into the slipstream, the aircraft inched toward Runway 32's threshold, as its altimeter unwound: 600 feet...500...300...100...

Passing over the fence at 115 mph, the olive-green, twin-engined, twin-finned medium bomber sank toward the blurred concrete in a full back-pressure control yoke-induced flare, screeching on the ground with its left main wheel at 80 mph, at which time the friction sufficiently reduced its air speed to permit the remaining two bogies to settle earthward.

Completing its deceleration roll and taxiing on to the American Airpower Museum ramp, the B-25J Mitchell, as the medium mission bomber, had appropriately been the first to return to base, the B-17 and the B-24 still plying the skies. If World War II had still been raging, the sequence would have been exactly the same.

A graduate of Long Island University-C.W. Post Campus with a summa-cum-laude BA Degree in Comparative Languages and Journalism, I have subsequently earned the Continuing Community Education Teaching Certificate from the Nassau Association for Continuing Community Education (NACCE) at Molloy College, the Travel Career Development Certificate from the Institute of Certified Travel Agents (ICTA) at LIU, and the AAS Degree in Aerospace Technology at the State University of New York - College of Technology at Farmingdale. Having amassed almost three decades in the airline industry, I managed the New York-JFK and Washington-Dulles stations at Austrian Airlines, created the North American Station Training Program, served as an Aviation Advisor to Farmingdale State University of New York, and devised and taught the Airline Management Certificate Program at the Long Island Educational Opportunity Center. A freelance author, I have written some 70 books of the short story, novel, nonfiction, essay, poetry, article, log, curriculum, training manual, and textbook genre in English, German, and Spanish, having principally focused on aviation and travel, and I have been published in book, magazine, newsletter, and electronic Web site form. I am a writer for Cole Palen's Old Rhinebeck Aerodrome in New York. I have made some 350 lifetime trips by air, sea, rail, and road.


Article Source: https://EzineArticles.com/expert/Robert_Waldvogel/534926


http://EzineArticles.com/?The-North-American-B-25-Mitchell&id=3686036



Robert Waldvogel

Aviation, Teaching, Writing, Foreign Language, Travel, Photography.

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