Project Origins and Early Development:
Glenn L. Martin Company of Middle River, Maryland (near Baltimore) was assigned the company designation of Model 179.In January of 1939, the United States Army Air Corps issued a specification (Circular Proposal 39-640) for a twin-engine medium bomber. Requests for proposals were widely circulated throughout the industry and responding companies included Martin, Douglas, Stearman, and North American. The proposal of the
Peyton M. Magruder as Project Engineer for the Model 179. Magruder and his team decided on a low-drag fuselage profile with a circular cross section. Since the Army desired high maximum speed but had not specified maximum landing or stall speeds, the team selected a wing a span of just 65 feet with a dihedral of only 1.3 degrees.Martin assigned a 26-year-old aeronautical engineer named
This yielded a wing loading of over 50 pounds per square foot. The wings were unusual in possessing no fillets, and were shoulder-mounted to leave the central fuselage free for bombs and provide ground clearance for the large propellers.
Early wind tunnel test models featured a twin vertical tail configuration (shown at right) that designers thought would provide better aerodynamic control. However, this was replaced by a single fin and rudder to provide the tail gunner with a better field of view.
Pratt & Whitney R-2800-5 Double Wasp air-cooled radials, the most powerful available at the time. Two-speed mechanical superchargers were installed to maintain engine power up to medium altitudes, and ejector exhausts vented on both sides of the closely-cowled nacelles. The engines drove four-bladed Curtiss Electric propellers of 13 feet, 6 inches in diameter, and with large spinners and cuffs at the blade roots to enhance engine cooling.The engines were to be a pair of 1850 hp.
The bomb bays were in an unusual tandem configuration. The forward pair of doors folded in half "accordion-style" when opened, while the aft doors opened outward in a more conventional "clamshell" fashion. Two 2000 lb. bombs could be carried in the main bomb bay, or up to 4,800 lbs. of smaller bombs if the aft bay was used as well.
Detailed design of the Model 179 was completed by June of 1939. On July 5, 1939, the Model 179 was submitted to a Wright Field Board. The Martin design was rated the highest of those submitted, and on August 10, 1939, the Army issued a contract for 201 Model 179s under the designation "B-26". This contract was finally approved on September 10. At the same time, the competing North American NA-62 was issued a contract for 184 examples under the designation B-25. Since the design had been ordered "off the drawing board", there was no "XB-26" as such.
semi-monocoque aluminum alloy fuselage was fabricated in three sections and had four main longerons, transverse circular frames, and longitudinal stringers covered by aluminum skin. The mid section containing the bomb bays was built integrally along with the wing section.The
The retractable tricycle landing gear was hydraulically actuated. The nose wheel pivoted 90 degrees and retracted into the nose section while the main gear folded aft into the engine nacelles. The vertical and horizontal stabilizers featured smooth, stressed-skin cantilever structures, with metal elevator surfaces and a fabric rudder surface.
The first aircraft (C/N 1226, USAAF Serial No. 40-1361) came off the production line in early November 1940, and even though it had yet to fly, orders for 139 B-26As with self-sealing tanks and armor were issued by the Army on September 16, 1940. Further orders for 719 B-26Bs on September 28, 1940 brought the total order to 1,131 aircraft.
On the 25th of September 1940, Martin Test Pilot and Chief Engineer, William K. "Ken" Ebel, Co-pilot Ed Fenimore, and Flight Engineer Al Malewski successfully completed the aircraft's maiden flight. Thus, the bomber went from paper concept to a flying aircraft in less than two years. Since there was no prototype, the first few production aircraft were used for test purposes. The first 113 hours of flight testing went fairly well with few required modifications. However, a slight rudder overbalance necessitated reversal the rudder trim tab direction travel. Soon after, the aircraft was turned over to the Army Air Corps for operational testing.
On February 22, 1941, the first four B-26s were accepted by the USAAF. The first operational unit was the 22nd Bombardment Group (Medium) based at Langley Field, Virginia, which had previously operated Douglas B-18s. However, several nose gear strut failures briefly delayed transition to full operational status. Although the strut was strengthened, the real problem was improper weight distribution. Due to logistical foul-ups, the first few B-26s were delivered without guns and had to be longitudinally trimmed using tools and spare parts for ballast. When the Army received the planes, they removed the ballast, thereby moving the aircrafts' center of gravity forward and increasing loads on the nose gear. Installation of the guns corrected the problem.
Early Controversy and Operational Challenges:
The B-26 was a fast plane with better overall performance than its contemporary, the B-25 Mitchell. However, the Marauder's small wing area and high wing loading, the highest of any allied bomber of the time, meant higher approach, touchdown and stall speeds (140 mph, 120 to 115 mph, and 130 mph with no flaps, respectively).
With the war heating up across the planet, the demand for new aircrewman was extremely pressing. Most experienced pilots were already overseas, seasoned instructors were in short supply, and it was not practical to give new pilots much flight time during initial training. They rapidly went from low performance aircraft (such as the Beechcraft AT-9) directly into "hot ships" like the B-26.
The Marauder's high performance and revolutionary features made this a huge leap for most, and the high approach speed and unforgiving single engine operation were more than some "green" pilots could handle. Experienced mechanics were also in short supply, which may have contributed to the high incidence of engine failures early in the bomber's career.
Due to its rotund fuselage, the Marauder's engines were placed fairly far outboard. Loss of power on one side therefore caused substantial asymmetrical thrust that could induce rapid yaw and roll rates if minimum controllable airspeed (VMC) was not achieved (or maintained). Although this was to be expected of an aircraft with this power and configuration, these characteristics initially led to a high number of accidents, particularly on takeoff.
The crash rate inevitably spawned a number of cynical nicknames such as "Widowmaker", "Martin Murderer", "The Flying Coffin", "B-Dash-Crash", "The Flying Prostitute" (because its small wings provided "no visible means of support"), and "The Baltimore Whore" (because the Martin Company was located there).
By the autumn of 1943, the situation resulted in the appointment of a blue ribbon Commission of Inquiry was led by then-Senator Harry Truman. When he and other commission members arrived at the Avon Park Bombing Range, they were greeted by the still-burning wreckage of two crashed Marauders. Indeed, the regularity of crashes by pilots training at MacDill Field — up to fifteen in one thirty day period — led to the only mildly exaggerated catchphrase, "One a day in Tampa Bay." The Board soon ordered the entire B-26 fleet to be grounded pending further inquiry.
Nevertheless, despite its high stall and landing speeds (which remained essentially unchanged despite numerous modifications made to reduce them), the Marauder had no really "vicious" flying characteristics, and its single-engine performance was actually fairly good for the day.
Although the B-26 was for a time considered so dangerous that aircrews tried to avoid getting assigned to Marauder-equipped units and civilian ferry crews actually refused to fly them, it turned out that the bomber was actually very safe in the hands of a properly trained crew. It certainly demanded a higher standard of training than the B-25 Mitchell, but once mastered, the B-26 offered a level of operational immunity to its crews unmatched by any other aircraft in its class.
Design Changes Lead to the Lowest Loss Rate of Any WWII Combat Aircraft:
Consequently, a variety of design changes were implemented and the resulting B-26B had an additional 6 feet (1.8 m) of wingspan and other changes. These modifications slightly reduced landing and stall speeds and ultimately yielded the lowest attrition rate of any combat aircraft of WWII. Nevertheless, it remained a challenging plane to fly and somewhat controversial throughout its service life.
B-26 crews first began flying combat missions in the South Pacific in the spring of 1942, but the majority were sent to England and the Mediterranean. The 22nd Army Air Force Bomb Group was originally based in northern Australia but often operated from Port Moresby, New Guinea. On 9 June 1942, Lt. Cmdr. Lyndon B. Johnson flew on a bombing mission to Lae, New Guinea, but his aircraft developed engine trouble and returned to base.
Like the B-25, the B-26 was originally designed for medium-altitude bombing, but the demands of combat eventually brought them down to treetop level. Later versions of the B-26 were equipped with a side-mounted battery of forward-firing machine guns for strafing ground targets. Intensive low-level bombing and strafing at Utah Beach by the Marauders before and during the "D-Day" Normandy invasion contributed to a reduction in casualties among the American assault force.
The B-26 was phased out of Army Air Force service shortly before the end of the war. The last Marauder mission of WWII was flown in May 1945. It continued to see duty in a variety of civilian roles for many years. Today, this superb machine lives on as a highly-prized museum item and in a handful of flyable variants.