On April 11th 1939 the North American NA-40B, NX14221, took off from Wright Field in Ohio to undertake a series of engine-out tests. During one of those tests the pilot lost control of the aircraft and it augured in. The aircraft was consumed by the subsequent fire, but the crew escaped serious injury. As a result, Douglas won the 1937 competition with their design that would become the A-20 Boston/Havoc. North American Aviation (NAA) went back to the drawing board. The lessons learned with the NA-40B were incorporated into a new twin-engine bomber design. NAA designated it the NA-62. Today we know that aircraft as the B-25 Mitchell medium bomber.
The NA-62 design was entered into the 1939 United States Army Air Corps (USAAC) medium bomber competition. Competing against the NA-62 was the Martin B-26 Marauder. Although there was no B-25 prototype aircraft yet, the USAAC ordered the NA-62 design into production as the B-25. The Marauder was also ordered into production without a single flyable example available for inspection, meaning both designs were essentially ordered right off the drawing board. The 9,816 B-25s produced by NAA would go on to serve with nearly every allied nation and in every theatre of World War II, train thousands of Air Force multi-engine pilots and crew members, and even star in a few movies.
Distinctive design features of the B-25 were the twin vertical stabilizers mounted at the ends of the horizontal stabilizer in the tail of the aircraft and the pronounced “gull” wing which resulted from the outer wing panels being designed with anhedral, or downward angle, from the engine nacelles out to the wingtips. B-25s were continuously improved, modified, and upgraded throughout the design’s history, resulting in 28 distinct variants with differing primary mission capabilities, armor and armament configurations, inclusion of self-sealing fuel tanks, nose and tail gun installations, and dorsal (upper fuselage) gun turret locations. When used by the United States Navy (USN) or Marine Corps (USMC), the B-25 was designated PBJ.
Early production variants of the B-25 were used for the famous raid on Tokyo by Doolittle and his raiders. B-25Cs were employed against Japanese targets in the Pacific beginning early in 1942 and continuing for the rest of the war. It was found that bombing from the medium altitudes at which the B-25 was designed and intended to bomb was less effective than low-level tactics. When 5th Air Force weaponeer Paul “Pappy” Gunn field-installed six forward-firing .50 caliber machine guns in their noses at the Townsville Modification Depot in Australia, and then loaded them full of parachute-retarded fragmentary bombs (parafrags), the modified 5th Air Force B-25Cs and B-25Ds became highly effective low-level strafing skip-bombers. The coming out party for these “commerce raiders” was the Battle of the Bismarck Sea. Gunn and his team removed the Bendix remote-controlled ventral turret from many of these bombers. The crews considered it useless to begin with, and after all, who needs a belly turret when you do all your flying down in the weeds anyway?
NAA incorporated some of the field mods made by Gunn and his weaponeers into the B-25G and the B-25H models. The G had a shorter nose with two 50 caliber machine guns…and a 75 millimeter M4 cannon. The M4 was the largest cannon used on production aircraft during the war. The G model also did away with that ventral turret, added two defensive gunnery positions in the fuselage aft of the wings (the “waist” positions), and improved the tail gunner position. On the H model B-25 the M4 cannon was replaced by a lighter weight built-for-purpose cannon and more .50 caliber machine guns were added up front. The 75 millimeter cannon, due to its slow rate of fire and substantial recoil, was removed from many of the G and H models and replaced with additional .50 caliber machine guns. There was also no copilot or bombardier in the B-25H. The pilot shared space under the greenhouse with the combination navigator/cannoneer who loaded the 75 millimeter cannon. The dorsal turret was moved forward to offset the extra crew and weapon weight now carried aft in the waist and tail of the bomber. The ability to carry up to eight 5” high velocity aerial rockets (HVARs) on rails under the outer wing panels was incorporated as well.
The ultimate Mitchell, the B-25J, looked like the previous straight bomber variants up front but incorporated the H model crew stations aft. B-25Js all carried four 50 caliber machine guns installed on the fuselage under the cockpit in “package” mounts. Built in larger numbers than any other B-25 variant, 4,318 J model B-25s rolled off the NAA production lines. NAA also produced a kit that added eight nose-mounted 50 caliber machine guns for a total of 14 that could be fired toward soon-to-be shredded targets. Add the ability to fire HVARs and drop bombs and the B-25J was capable of dishing out terrific amounts of punishment. B-25s equipped with cameras for aerial reconnaissance were designated F-10s.
Navy and Marine Corps PBJs were in most respects identical to their USAAC counterparts. A significant difference was the increased use of radar in the PBJs. PBJ radars were usually mounted in place of the ventral turret or in a fairing protruding from the nose of the aircraft. Later PBJs mounted the radar in a starboard wing fairing. Most of the PBJs equipped USMC bombing squadrons beginning during early 1943 with Marine Bombing Squadron 413 (VMB-413). The Marines operated their PBJs from the Philippines, Saipan, Iwo Jima, and Okinawa. Tasked primarily with long-range interdiction of Japanese shipping, the weapons of choice for the Marine PBJs were the 5 inch HVAR and the .50 caliber machine guns, both used effectively to enforce the virtual blockade of Japan. During November of 1944, the Navy did put a B-25 on a carrier again, but this time it was a PBJ-1H with a ginormous tail hook. The carrier was the USS Shangri-La (CV-38). The irony is that the last time B-25s had operated from an aircraft carrier (the Doolittle Raid in 1942), when asked where the raid had originated, President Roosevelt had replied, “Shangri-La.” The carrier suitability tests of the PBJ-1H were judged to be marginally successful, but the project was not pursued beyond the feasibility study.
Surprisingly, no B-25s were assigned to squadrons in the European Theater of Operations (ETO). In the Mediterranean Theater of Operations (MTO), several squadrons equipped with B-25s began operations from Egypt during October of 1942. They targeted everything Axis in North Africa, flying missions there until the war, and their missions, shifted north to Sicily and Italy. These Mitchells performed effective “sea sweep” missions in the Aegean Sea and the approaches to Corsica, Sicily, and Italy. Italian-based B-25s attacked targets in Italy, Austria, the Balkans, and anywhere else quick-reaction missions were needed. At maximum strength there were 20 Bombardment Squadrons attached to 5 Bombardment Groups serving in the Ninth and Twelfth Air Forces in the MTO.
At 0940 on Saturday July 28th 1945, A USAAF B-25D Mitchell bomber, flying a routine personnel transfer mission bound for Newark airport in thick fog, crashed into the north side of New York’s Empire State Building between the 79th and 80th floors. One of the Wright R-2600 engines from the bomber was found on a rooftop on the next block, where it had started a fire. 11 people in the building were killed along with all three of those aboard the aircraft. An elevator attendant survived when the elevator she was in fell 750 feet to the building’s basement. The fire caused by the crash was the only one ever brought under control that high in a building or structure.
B-25s pilots reported (and still do) that the aircraft was docile, forgiving, and safe to fly. Tricycle landing gear made for excellent visibility while taxiing and on approach. Large control surfaces made the airplane responsive but a touch heavy on the controls. The Wright R-2600 engines were good for about 3400 horsepower between them, which was more than adequate for the Mitchell. Control of the aircraft could be maintained, even banking turns into the nonfunctional engine of up to 60 degrees, down to 145 miles per hour, but rudder had to be used to control the direction of the B-25, as using ailerons could potentially cause loss of control.
One illustration of the punishment the B-25 could withstand is the B-25C Patches, assigned to the 321st Bombardment Group fighting in the MTO. Patches was so named because after all of the patched bullet and flak holes punched in the airframe were repaired, her crew chief painted each new patch with bright yellow-green zinc chromate primer. Patches absorbed 400 hits from enemy fire and flak, was landed on her belly six times, and flew more than 300 missions. By the time Patches was retired pilots reported that in order to fly her, 8 degrees of left aileron trim and 6 degrees of right rudder trim were required just to get her to fly in the same direction. Even so, Patches didn’t fly straight and level so much as she crabbed through the air sort of sideways!
After the war ended, like so many of the other aircraft that fought and won it, thousands of B-25s were unceremoniously scrapped and smelted down for razor blades. There were only a few hundred of them left by the time the United States Air Force (USAF) was created in 1947. TB-25s trainers continued to serve into the 1950s, primarily as multi-engine trainers for fledgling Air Force bomber, tanker, and transport pilots and navigators. Some B-25s were stripped of most military equipment and used as VB-25 personnel transports. During the 1950s many Air Force bases (AFBs) and Air National Guard bases (ANGBs) had a B-25 or two assigned as “base hack” or proficiency aircraft that deskbound eagles could use to maintain their flight status (and monthly flight pay). Several of these survivors received the Hayes exhaust system modification resulting in a slightly less-deafening exhaust note than the characteristic howl of the B-25’s Wright R-2600 Double Cyclone engines.
The very last operational United States Air Force B-25, a TB-25J, Air Force serial 44-30854, was flown from Turner AFB in Georgia to Eglin AFB in Florida on May 21st 1960. There the aircraft was retired in a ceremony attended by four of the surviving Doolittle Tokyo raiders. The aircraft eventually ended up at the National Museum of the United States Air Force wearing the colors of Doolittle’s lead aircraft. The last operational B-25s anywhere in the world were Indonesian B-25Js. These veteran aircraft were finally retired in 1979. Operators of the B-25 Mitchell medium bomber include Australia, Biafra, Bolivia, Brazil, Canada, China, Chile, Colombia, Cuba, Dominican Republic, France, Indonesia, Mexico, the Netherlands, Peru, Poland, Spain, Russia, the United Kingdom, USAAC, USN, USMC, Uruguay, and Venezuela. There are roughly 55 flyable B-25s maintained around the world today.
B-25s have starred in several movies over the years, including Thirty Seconds Over Tokyo (MGM 1944), In Harm’s Way (Paramount 1965), Hanover Street (Columbia 1979), Forever Young (Warner Brothers 1992), and Pearl Harbor (Touchstone 2001). The ultimate B-25 movie is without a doubt Catch-22, filmed in Mexico and released by Paramount in 1970. The movie gathered 17 flyable B-25s and one non-flyable hulk. The hulk was used for the crash scene. The aerial sequences (including that unforgettable mass takeoff) required three months to shoot. B-25s only appeared in the movie for about 12 minutes. Do you know of any other movies in which B-25s appeared?