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Martin B-26 Marauder - Introduction and Development
The Martin B-26 Marauder was one of the more controversial American aircraft of the Second World War, earning an early reputation as a killer aircraft before going on to suffer the lowest loss rate of any American bomber in the European theatre.
The Marauder was designed to satisfy Circular Proposal 39-640 of 11 March 1939 which called for a high speed light or medium bomber, capable of carrying 3,000lb of bombs 2,000 miles with a top speed of over 300mph. It had to be capable of operating between 8,000 and 14,000ft, and was to be used to support ground troops.
The Martin 179, designed by Peyton M. Magruder, was for an aircraft with a torpedo or cigar shaped fuselage, two massive radial engines, a nose-wheel undercarriage and short stubby wings. It was originally designed with a twin tail, but in October 1939 that was replaced with the single fin and rudder of the final design.
The winner of Proposal 39-640 was decided by allocated each design a number of quality points. The Martin 179 was the clear winner, with 813.6 points, followed by the North American NA-62. The army had wanted to order 385 examples of the winning aircraft, but Martin could only produce 201 aircraft, and so North American were rewarded with a contract for 184 NA-62s, as the B-25.
The first B-26 made its maiden flight on 25 November 1940, with Ken Ebel, Martin's chief engineer, at the controls. This and the next three aircraft were then used for testing and service evaluation, while at the same time production continued on the remaining aircraft.
The early service tests, in December 1940 and January 1941, went well. In the hands of experienced pilots the fully equipped aircraft had a service ceiling of 25,000ft, a top speed of 323mph and a range of 3,000 miles at 15,000ft. The new aircraft had the highest wing loading of any aircraft yet accepted by the USAAC, making it tricky to handle at low speeds, had a high landing speed (over 100mph) and a long takeoff run, but despite this on 8 February 1941 the B-26 was accepted for service.
In the same month the 22nd Bombardment Group at Langley Field became the first unit to receive the B-26. The new aircraft almost immediately ran into the problems that would earn it the nicknames 'widow maker' or 'the separator' (for separating the men from the boys). The B-26 was the first of a series of aircraft ordered 'off-the-shelf', without a prototype or a prolonged period of development, and it entered service only three months after its first flight.
Some problems were easy to fix. At first the aircraft delivered to Langley Field lacked the guns, radios and armour – all items installed by the Army not by Martin. The lack of the dorsal turret was a particular problem as it altered the centre of gravity, making the aircraft nose heavy. The result was a series of crashes caused by failure of the nose gear. These only ended when the full armament was installed.
A second problem was that the B-26 used many more electrical systems than earlier aircraft, including the power operated turret and the Curtiss- Electric propeller. The propeller developed a dangerous habit of failing at take-off, when it was under the most stress. Eventually this was traced to a problem with the servicing of the new aircraft – the internal batteries were being used during maintenance on items like the power turret, draining them of power. When the aircraft was next used the flat battery would fail, causing the propellers to feather and the aircraft to crash. This problem was solved by providing the ground crew with portable batteries for services.
The third problem was harder to solve. The B-26 was a 'hot' aircraft, unforgiving at low speeds, not well suited to aerobatics and with a number of new features, including the nose-wheel landing gear. This hadn't caused any problems during the brief test period when the aircraft was in the hands of experienced pilots, but in 1941 and especially at the start of 1942 the aircraft was being flown by large numbers of new pilots, many of whom came to it directly from the North American AT-6 Texan, a single engined aircraft with tail-wheel landing gear and a top speed of 205mph.
This problem was eventually solved in three ways. Physically the aircraft was given longer wings (starting with the 982nd aircraft). This made it slower but easier to handle. The training programme was extended to include a period of advanced training in the twin-engined Curtiss AT-9. Finally as the training staff became more familiar with the type the quality and usefulness of the training increased dramatically, and the accident rate dropped from a high of 162 accidents for every 100,000 hours of flying time in 1942 down to 37 in 1944.
The Marauder entered combat with the 22nd Bombardment Group on 5 April 1942, in an attack on Rabaul. The same year saw it enter service with the RAF in the western desert, and it was only the enthusiastic reports that came from the South Pacific and North Africa that kept the B-26 in production during 1942. The Marauder was used in most theatres of the war in some numbers, but it was most important in the European theatre, at first with the Eighth Air Force and then in larger numbers with the tactical Ninth Air Force. At its peak in March 1944 the USAAF had 1,931 Marauders on its books, while the Ninth Air Force still had 1,012 in theatre in November and 800 on its books at the end of the war. By this time the B-26 had redeemed itself, and after a very shaky start had become the safest of all American bombers in the European theatre, with the lowest loss rate.
By then many Marauder groups had converted to the A-26 Invader, and only three of the Ninth's eight groups survived to join the post-war occupation forces in Germany. The last aircraft were deactivated in February 1946, and it was completely gone from the inventory by the end of the year. The B-26 disappeared so quickly for a number of reasons. It was more expensive to build than the B-25, not as modern as the A-26, and never entirely escaped from its early reputation as a dangerous aircraft.
Martin B-26 Marauder & Douglas A-26 Invader in Combat over Europe
The Martin B-26 Marauder had a long and troubled introduction to combat service. On four successive occasions various investigation boards recommended that production of the design should be cancelled due to its high rate of training accidents.
Indeed, the B-26 was deemed difficult to handle, mainly because of its relatively small wing area. The resulting high wing loading dictated an unusually long take-off run and high landing speed. The Marauder touched down at about 115 mph – which was higher than the landing speed of any contemporary fighter. Its high stalling speed only made matters worse.
Despite its terrible reputation for being a ‘widow maker’, the Marauder eventually proved its worth. By 1944, the B-26s of the U.S. 9th Air Force had recorded the lowest loss rate of any American aircraft in the ETO performing operational missions, at less than one half of one percent. Over Europe the B-26 was the workhorse of the USAAF medium bomber force. It was sparsely employed in other theatres of operations, notably in the Pacific – not that it was unwanted there. Gen. George Kenney, the commanding general of the U.S. 5th Air Force, wrote as follows to the USAAF Headquarters in Washington, D.C.:
“I know you have set me up for the B-25s but the B-26 is a much better combat job. While the B-26 may be frowned upon in some circles at home, the boys here prefer it to the B-25 every time. The B-26 has a better bomb load, more range, is faster, more manoeuvrable and stands up much better in a crack-up. We will take all you have. In peacetime the boys would probably prefer the B-25, as it is considerably easier to fly, but when they’re shooting for keeps, the B-26 takes care of itself and comes home” (quoted after: Kenneth T. Brown, Marauder Man, New York 2001).
In July 1939 the U.S. Army Air Corps was presented with a project for a new, high-speed medium bomber, designed by the Glenn L. Martin company of Middle River (near Baltimore), Maryland. The USAAC was impressed by the expected performance and ordered the aircraft ‘straight off the drawing board’ (there was no prototype). The first B-26 (s/n 40-1361) took off on its maiden flight on 25th November 1940. It was powered by two Pratt & Whitney R-2800-5 Double Wasp radial engines, rated at 1850 hp each, which were the most powerful engines available at the time. The first B-26s were accepted by the USAAC in February 1941. They were issued to 22nd BG (Bombardment Group) stationed at Langley Field, Virginia. In October 1941 the Martin production line shifted over to the B-26A, which introduced additional armour plating and self-sealing fuel tanks, among other features. Reportedly around that time the aircraft was assigned the name ‘Marauder’.
The B-26B appeared in May 1942, and it became the most numerous version of the Marauder. The alarming rate of training accidents made it necessary to increase the wing area of the design in order to lower its wing loading and reduce the takeoff and landing speeds. A new wing was introduced on the B-26B-10 production block, which first appeared in early 1943. The wingspan was increased from 65 to 71 feet and the wing area increased from 602 to 658 square feet. A taller fin and rudder was introduced to maintain stability with the larger wing. The advantages of the reduced wing loading were offset by an increase in the aircraft’s overall weight, since in the meantime the B-26 had been upgunned to carry a total of twelve 0.50-inch machine guns. On the B-26B-20 and later blocks, the hand-held twin tail guns were replaced by a power-operated turret. Additional armour was introduced on the B-26B-30. Early models of the B-26 had two separate bomb bays. After a pair of flexible 0.50-inch machine guns had been installed in the waist window area, the space formerly occupied by the rear bomb bay was used for storing ammunition boxes. Hence, from the B-26B-45 onwards the aft bomb bay was sealed shut. The application of camouflage paint was discontinued during the production run of the B-26B-55 version. The last of 1,883 B-26Bs was delivered in February 1944.
Martin B-26 Marauder Bomber Characteristics
|Armament||Eleven .50 cal. machine guns|
|Normal bomb load||4,000 lbs., 5,200 lbs. of bombs (max overload)|
|Engines||Two Pratt & Whitney R-2800-43 "Double Wasp" radials of 2,000 hp each|
|Maximum speed||283 mph at 5,000 ft.|
|Cruising speed||216 mph|
|Range||1,100 miles with 4,000 lbs. bomb load|
|Span||71 ft. 0 in.|
|Length||56 ft. 1 in.|
|Height||20 ft. 4 in.|
|Weight||38,200 lbs. (maximum)|
|Specifications based on B-26G model.|
B-26B Marauder production at Glenn L. Martin Co., Middle River, MD.
B-26 Marauder dropping its bomb load, World War II.
USAAF B-26 Marauder with left wing and engine housing riddled by antiaircraft fire during a bombing raid in Tunisia, returned to base with a safe belly landing, 1943.
B-26 Marauder in flight, during World War II.
B-26 Marauder on display at the National Museum of the U.S. Air Force, Dayton, OH. It was flown in combat by the Free French during the final months of WW II and is painted as a 9th Air Force B-26B assigned to the 387th Bomb Group in 1945.
Cockpit photo of B-26 Marauder on display at the National Museum of the U.S. Air Force, Dayton, OH.
Category: American literature
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American WWII's aircraft
The B-26 was ordered off the drawing board (no prototypes were built) at the same time as the B-25. With a troubled development history, it was called (among other things) the "Flying Prostitute" - with its high wing loading (51 lbs per square ft) and small wings, it was said to have had no visible means of support. Although most problems were caused by pilot unfamiliarity, there were some development problems. Eventually, the type's deficiencies were corrected and the B-26 went on to a stellar career. B-26 crews began flying combat missions in the South Pacific in the spring of 1942, but most of the aircraft were sent to England and the Mediterranean. The Marauder had the lowest loss rate of any Allied bomber, less than one-half of one percent. One B-26B, nicknamed Flak Bait, flew more missions in Europe (202) than any other Allied airplane in World War II. A small number were used by the Navy as JM-1/-2 for target tug, reconnaissance, and utility duties. Most of the B-26s were retired by 1948. It was one of several American warplanes given its official nickname by the British. Production aircraft were ordered to Australia the day after Pearl Harbor was attacked to provide additional defense. The B-26 was the only Army bomber to drop torpedoes. Because of its reputation as a "widow-maker" early in its career, Lt. Col. Jimmy Doolittle was ordered to go to training airfields to personally demonstrate that the B-26 could stay aloft on one engine. Late in the war, Marauders were used to attack German rocket sites, airfields, and communications centers in France and the Low Countries. One airplane was modified in order to test the tandem landing gear arrangement for the Boeing B-47 after the war.
B-26 Marauder - Variants
As early as September 1940, orders were issued for new modifications of the "Marauder" - 139 B-26A and 791 B-26B. They implemented improvements planned earlier, but for some reason not implemented on the B-26 or suggested by the first experience of operation. They included protruded rigid fuel tanks instead of the previously used soft ones (this made it the first US army aircraft fully equipped with self-tightening tanks) and approximately 252 kg of armor to protect the crew and the most important pieces of equipment.
On the B-26A, which began to enter the Air Force in October 1941, suspension was introduced for two additional fuel tanks (in the rear bomb bay), and 12, at the fore and tail machine guns. The B-26A was a development of the basic B-26 incorporating changes on the production line. Fittings for mounting an auxiliary fuel tank in the aft bomb bay were added, and the nose and tail .30-cal. machine guns were upgraded to .50-cal. The A model aircraft was 2 feet, 3 inches longer than the initial B-26. The first 30 of 139 A models built had R-2800-5 radial engines installed while the last 109 aircraft had R-2800-39 radials. The -39 fitted aircraft were designated B-26A-1 but were essentially identical to the earlier aircraft. The RAF got 52 B-26A-1s (FK 109 to FK 160) and designated them Marauder Mk. Is.
The first 641 (of 1883) Martin B-26Bs built were basically improved versions of the A model. Changes included replacement of the single .50-cal. machine gun with twin guns in the tail and a tunnel gun mounted in the rear crew entry hatch for increased protection below and behind the aircraft. Block 3 and 4 aircraft had large carburetor intakes necessary for more robust sand filters. Block 4 aircraft had a longer nose wheel strut, which was designed to improve take-off performance by increasing the angle of attack. Late production block 4 aircraft deleted the tunnel gun and replaced it with waist gunner positions location near the tail below the aircraft centerline. Great Britain received 19 B-26B-4s as Marauder Mk.1A. Major changes were incorporated into the B-26B-10 and later including a wing span increase of six feet and a taller vertical stabilizer.
Major changes were incorporated into the B-26 design beginning with the block 10 B model (and block 5 C model). The wing span was increased from 65 to 71 feet to decrease the high wing loading and improve the handling of the aircraft, particularly at landing speeds. The wing was also modified by adding flaps outboard of the engine nacelles to further improve take off and landing performance. The vertical stabilizer was heightened by 20 inches to 21 feet, 6 inches and made the late model B-26s easily distinguished from the "short tail" early models.
Like the B-25, the forward armament of the B-26 was increased for ground strafing missions. The nose featured one fixed and one flexible .50-cal. machine gun while four fixed fuselage-mounted .50-cal. package guns were added just behind and below the cockpit. Differences between late production B models included a switch from manually operated tail guns to powered types, relocation of the waist gunner positions and various engine cowling changes. Many aircraft were modified in the field incorporating improvements from later model production. Armor plating was added to the aircraft's exterior just below and slightly forward of the wind screen to protect the pilot and co-pilot. Block 45 and later B-26Bs had a larger windscreen designed for better forward visibility. 1,883 B-26Bs were built 1,242 of these were block 10 or later.
The B-26C was the Omaha, Neb., produced version of the B-26B. The first B-26C-5 rolled out of the new plant in August 1942 about 13 months after the order for the C model was placed. Although the C-5 was virtually identical to the Baltimore produced B-26B-10, the block numbers didn't match because of a delay in opening the plant in Nebraska. 1,210 C models were built along with more than 300 AT-23B trainer versions, which were later redesignated TB-26C. 615 C models on contract when the war ended were canceled before delivery. The RAF received 123 B-26C-30s as Marauder Mk. IIs, some of which were transferred to the South African Air Force. Like the B-26B, the C had many design changes incorporated on the production line. For example, the tail turret was changed to a Martin-Bell power type beginning with block 10 C models (and B-26B-20s), which shortened the aircraft by about two feet.
The Martin XB-26D was a modified B-26 used to test hot air deicing equipment. Heat exchangers would transfer heat from engine exhaust gases to air circulated to the leading and trailing edges of the wing and empennage surfaces. The hot air would delay the formation of lift destroying ice on the wings and tail. Hot air deicing was never incorporated into a production B-26, but the basic design is widely used on modern aircraft. The hot air deicing method was also tested on the XB-25E.
The B-26E was a B-26B modified by moving the dorsal (top) turret from the aft fuselage forward to just behind the cockpit. The E model was tested against a standard aircraft in defensive and offensive firepower tests. In a strafing mission, the forward top turret would bring the total firepower to eight .50-cal. machine guns. Although the tests showed the forward turret location to be an improvement, only marginal gains were achieved. Martin engineers along with the Army Air Forces decided the cost and time of converting the production lines was not worth the effort, and the basic B-26 was built with the aft positioned dorsal turret throughout the production run.
The B-26F was an improved version of the B-26B-55-MA. The most significant change for the F model design was the 3.5 degree increase in the wing's angle of incidence -- the wing and engines were tilted slightly up in order to improve take off, landing and low speed performance. Other changes made included the removal of the fixed .50-cal. machine gun in the nose, an improved tail turret with increased armor and ammunition for the gunner, and slightly increased fuel capacity. The RAF received 200 F models (S/N 42-96329 to 42-96528) as Marauder IIIs. The B-26F was manufactured exclusively in Martin's Baltimore plant after the Omaha plant converted to B-29 assembly. The first aircraft was delivered in early February 1944.
The B-26G was the last production model of the series. A total of 893 B-26G combat-ready aircraft were built along with 57 TB-26G crew training aircraft (950 total). The RAF received 150 G models along with 200 B-26Fs, which were all designated Marauder III. Externally, the B-26F and B-26G were identical. The only way to distinguish these two models is by serial number. Interior equipment on the B-26G was standardized and accounts for most of the differences with the F model. The last of more than 5,000 B-26s built (all types) was delivered on March 30, 1945, and named Tail End Charlie "30".
The B-26 Marauder
One of the most controversial American combat aircraft of the Second World War was the Martin B-26 Marauder. It was primarily used in Europe and was in fact numerically the most important USAAF medium bomber used in that theatre of action. However, on four occasions, investigation boards had met to decide if the development and production of the Marauder should continue.
In spite of this, the Marauder survived all attempts to remove it from service. By 1944, the B-26s of the US 9th Air Force had the lowest loss rate on operational missions of any American aircraft in the European theatre, reaching a point less than one half of one percent. Despite its high landing speed of 130 mph, which remained essentially unchanged throughout the entire production career of the B-26 in spite of numerous modifications made to reduce it, the Marauder had no really vicious flying characteristics and its single-engine performance was actually fairly good. Although at one time the B-26 was considered so dangerous an aircraft that aircrews tried to avoid getting assigned to Marauder-equipped units and civilian ferry crews actually refused to fly B-26s, it turned out that the Marauder could be safely flown if crews were adequately trained and knew what they were doing. It nevertheless did demand somewhat of a higher standard of training for its crews than did its stablemate, the B-25 Mitchell. Once mastered however, the B-26 offered a level of operational immunity to its crews unmatched by any other aircraft in its class.
A total of 5157 B-26 Marauders were built. Although on paper the B-26 was a more advanced aircraft than the North American B-25 Mitchell, it was built in much fewer numbers because it was more expensive to manufacture and had a higher accident rate (even though the accidents were mainly due to insufficient training and not inherently bad design).
The Martin Marauder's history dates back to early 1939. Both the North American B-25 Mitchell and the Martin B-26 Marauder owe their origin to the same Army Air Corps specification. On March 11, 1939, the Air Corps issued a proposal for the design of a new medium bomber. According to the requirements listed in the specification, a bombload of 3000 pounds was to be carried over a range of 2000 miles at a top speed of over 300 mph and at a service ceiling exceeding 20,000 feet. The crew was to be five and armament was to consist of four 0.30-inch machine guns. The proposal called for either the Pratt & Whitney R-2800, the Wright R-2600, or the Wright R-3350 radial engine.
Four aircraft manufacturers responded with proposals, Martin, Douglas, Stearman and North American. Since the Army wanted a high maximum speed but hadn't specified any limitation on landing speed, the Martin team selected a high-mounted wing with a wingspan of only 65 feet. Its small area gave a wing loading of more than 50 pounds per square foot. The wing was shoulder-mounted to leave the central fuselage free for bomb stowage. The fuselage had a low-drag profile with a circular cross section.
The engines were to be a pair of 1850 hp Pratt & Whitney R-2800-5 Double Wasp air-cooled radials, which were the most powerful engines available at the time. Two-speed mechanical superchargers were installed in order to maintain engine power up to medium altitudes and ejector exhausts vented on each side of the closely-cowled nacelles. The engines drove four-bladed 13 foot 6 inch Curtiss Electric propellers. Large spinners were fitted to the propellers and root cuffs were added to aid in engine cooling. In all, the armament included two 30 calibre machine guns and three 50 calibre machine guns including one in the tail and another installed in the tip of a transparent nose cone and operated by the bombardier. The tail gunner had enough room to sit in an upright position, unlike the prone position that had been provided in the early B-25.
There were two bomb bays, fore and aft. The bomb bay doors were unusual in being split in tandem, the forward pair folding in half when opened and the aft set being hinged normally to open outward. Two 2000-lb bombs could be carried in the main bomb bay, but up to 4800 pounds of smaller bombs could be carried if the aft bay was used as well.
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. Although the first B-26 had yet to fly, orders for 139 B-26As with self-sealing tanks and armor were issued on September 16. Further orders for 719 B-26Bs on September 28, 1940 brought the total B-26 order to 1131 aircraft.
A series of failures of the front wheel strut resulted in a delay in bringing the B-26 to full operational status. Although the forward landing gear strut was strengthened in an attempt to correct this problem, the true cause was an improper weight distribution. The manufacturer had been forced to deliver the first few B-26s without guns and had trimmed them for delivery flights by carefully loading service tools and spare parts as ballast. When the Army took the planes over, they removed the ballast without replacement and the resultant forward movement of the center of gravity had multiplied the loads on the nosewheel, causing the accidents. The installations of the guns called for in the original design corrected the problem.
The last B-26 was delivered in October of 1941. That month, the Martin Middle River production line shifted over to the B-26A version, which really was the same aircraft with a few modifications.
The Martin B-26 Marauder.
The Martin B-26 Marauder. By J. K. Havener. St. Petersburg, Fla.: Southern Heritage Press, 1998. Tables. Diagram. Photographs. Bibliography. Index. Pp. viii, 264. $18.95 paperback. ISBN: 0-941072-27-4
Former B-26 pilot Havener has given us a wonderful history of the development and operations of the famous Martin Marauder. A veteran of over fifty combat missions in Europe as well as a transition instruction in the aircraft, he provides one of the best overall histories of the aircraft written.
This is an important point. There are a number of good books about the B-26. In 1980, veteran pilot, Carl Moore, wrote an excellent short book, Flying the B-26 Marauder over Europe. This is more of the typical "here's the story of my experiences during the War" kind of book. It is also far richer in technical content than Havener's volume. But Havener has assembled stories of literally hundreds of missions, crews, and aircraft from the four major theaters in which the B-26 engaged in combat: the southwest Pacific, Alaska, the Mediterranean, and--most importantly--western Europe.
One of the most important parts of the story has to be how the B-26 was "saved" from being cancelled. Most readers are probably aware of the Marauder's early problems that led to such epithets as the "Widow Maker," "One a day in Tampa Bay," and the "B Dash Crash." The hero of the story is always Brig. Gen. Jimmy Doolittle. Well, yes, partly. Hap Arnold gave Doolittle responsibility for getting the B-26 weapon system's problems squared away. But most of the work was done by Doolittle's hand-picked man, 1st Lt. (later Colonel) Vincent "Squeek" Burnett. The demo flights around the U.S., development of operating procedures, and work with Martin were mostly Burnett's doing and saved what became one of the great combat aircraft in Europe.
After discussing the origins and claims to fame of the Marauder, Havener devotes the next three chapters to operations. The Pacific and Alaska come across for what they were: training grounds for what the aircraft would later become in Europe. The living conditions and logistics in both theaters were miserable, and the Army really hadn't figured out how it wanted to use the aircraft. A superb medium bomber didn't do as well dropping torpedoes or doing low-level bombing and strafing, and many crews paid the price of these tough early operations. After some initial difficulties in the Med, Doolittle and Burnett finally established how the Marauder should be used and, despite the also austere field conditions in that theater, the aircraft started showing some impressive results.
But Europe was where Martin's dream proved its worth. The B-26 had the lowest loss rate of any combat aircraft in the theater. One, Flak Bait (in the National Air and Space Museum collection) racked up 202 combat missions--a record for any aircraft in Europe. B-26s were first to hit beach targets on D-Day and hit everything from airfields to strategic targets to bridges and gun emplacements all the way to V-E Day. The eight groups flew from 239 missions (the newest outfit) to 428 (the first group, starting in May 1943).
Martin built more than 5,200 aircraft, but when the war ended these were quickly sent to reclamation sites and, for the most part, melted down for their aluminum. Today only about five of these bombers remain, but they are fitting tributes to an excellent combat aircraft and the men who flew them in combat. Havener has ensured that the Marauder story will not be forgotten.
Martin B-26 Marauder - Introduction and Development - History
Span: 71 ft. 0 in.
Length: 58 ft. 3 in.
Height: 21 ft. 6 in.
Weight: 38,200 lbs. (max.)
Armament: Twelve .50-cal. machine guns plus 5,200 lbs. of bombs (max.
overload) or one externally mounted torpedo
Engines: Two Pratt & Whitney R-2800-43 "Double Wasp" radials of 2,000 hp. each (take-off power)
Despite its high landing speed of 130 mph, which remained essentially unchanged throughout the entire production career of the B-26 in spite of numerous modifications made to reduce it, the Marauder had no really vicious flying characteristics and its single-engine performance was actually fairly good. Although at one time the B-26 was considered so dangerous an aircraft that aircrews tried to avoid getting assigned to Marauder-equipped units and civilian ferry crews actually refused to fly B-26s, it turned out that the Marauder could be safely flown if crews were adequately trained and knew what they were doing. It nevertheless did demand somewhat of a higher standard of training from its crews than did its stablemate, the B-25 Mitchell. However, once mastered, the B-26 offered a level of operational immunity to its crews unmatched by any other aircraft in its class.
A total of 5157 B-26 Marauders were built. Although on paper the B-26 was a more advanced aircraft than its stablemate, the North American B-25 Mitchell, it was built in much fewer numbers because it was more expensive to manufacture and had a higher accident rate.
One of the most commonly-asked questions is the difference between the Martin B-26 Marauder and the Douglas B-26 Invader. They were two completely different aircraft and had been designed to completely different requirements. The Douglas B-26 Invader had been originally been designated A-26, and was a twin-engined attack bomber intended as a successor to the Douglas A-20 Havoc. In 1948, the newly-independent Air Force decided to eliminate the A-for-Attack series letter as a separate designation, and the A-26 Invader was redesignated B-26, in the bomber series. There was no danger of confusion with the Martin B-26 Marauder, since this aircraft was by that time no longer in service with the US Air Force.
The history of the Martin Marauder dates back to early 1939. Both the North American B-25 Mitchell and the Martin B-26 Marauder owe their origin to the same Army Air Corps specification. On March 11, 1939, the Air Corps issued Proposal No. 39-640 for the design of a new medium bomber. According to the requirements listed in the specification, a bombload of 3000 pounds was to be carried over a range of 2000 miles at a top speed of over 300 mph and at a service ceiling exceeding 20,000 feet. The crew was to be five and armament was to consist of four 0.30-inch machine guns. The proposal called for either the Pratt & Whitney R-2800, the Wright R-2600, or the Wright R-3350 radial engine.
Requests for proposals were widely circulated throughout the industry. Proposals were received from Martin, Douglas, Stearman, and North American. The proposal of the Glenn L. Martin company of Middle River, Maryland (near Baltimore) was assigned the company designation of Model 179. Martin assigned 26-year-old aeronautical engineer Peyton M. Magruder as Project Engineer for the Model 179. Magruder and his team chose a low-drag profile fuselage with a circular cross section. Since the Army wanted a high maximum speed but hadn't specified any limitation on landing speed, the team selected a high-mounted wing with a wingspan of only 65 feet. Its small area gave a wing loading of more than 50 pounds per square foot. The wing was shoulder-mounted to leave the central fuselage free for bomb stowage. The wings were unusual in possessing no fillets. The engines were to be a pair of 1850 hp Pratt & Whitney R-2800-5 Double Wasp air-cooled radials, which were the most powerful engines available at the time. Two-speed mechanical superchargers were installed in order to maintain engine power up to medium altitudes, and ejector exhausts vented on each side of the closely-cowled nacelles. The engines drove four-bladed 13 foot 6 inch Curtiss Electric propellers. Large spinners were fitted to the propellers, and root cuffs were added to aid in engine cooling.
The armament included a flexible 0.30-inch machine gun installed in the tip of a transparent nose cone and operated by the bombardier. Two 0.50-inch machine guns were installed in a Martin-designed dorsal turret located behind the bomb bay just ahead of the tail. This was the first power-operated turret to be fitted to an American bomber. Another 0.30-inch flexible machine gun was installed in a manually-operated tunnel position cut into the lower rear fuselage. There was a 0.50-inch manually-operated machine gun installed in a pointed tail cone. The tail gunner had enough room to sit in an upright position, unlike the prone position that had been provided in the early B-25.
There were two bomb bays, fore and aft. The bomb bay doors were unusual in being split in tandem, the forward pair folding in half when opened and the aft set being hinged normally to open outward. Two 2000-lb bombs could be carried in the main bomb bay, but up to 4800 pounds of smaller bombs could be carried 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.
Although the first B-26 had yet to fly , orders for 139 B-26As with self-sealing tanks and armor were issued on September 16. Further orders for 719 B-26Bs on September 28, 1940 brought the total B-26 order to 1131 aircraft.
Early wind tunnel test models of the B-26 had featured a twin tail, which designers thought would provide better aerodynamic control. This was dropped in favor of a single fin and rudder so that the tail gunner would have a better field of view.
The B-26 had a semi-monocoque aluminum alloy fuselage fabricated in three sections. The fuselage had four main longerons, transverse circular frames, and longitudinal stringers covered by a metal skin. The mid section with the bomb bays was built integrally with the wing section. The retractable tricycle landing gear was hydraulically actuated. The nose wheel pivoted 90 degrees to retract into the nose section, and the main wheels folded backwards into the engine nacelles. The tail fins were of smooth stressed skin cantilever structure. The elevators were covered with metal skin, but the rudder was fabric covered.
The first B-26 (c/n 1226, USAAF serial 40-1361) took off on its maiden flight on November 25, 1940, with chief engineer and test pilot William K. Ebel at the controls. The first B-26 initially flew without any armament fitted.
The first 113 hours of flight testing went fairly well, and there were few modifications needed. However, a slight rudder overbalance required that the direction of travel of the trim tabs be reversed.
Since there was no prototype , the first few production aircraft were used for test purposes. On February 22, 1941, the first four B-26s were accepted by the USAAF. The first to use the B-26 was the 22nd Bombardment Group (Medium) based at Langley Field, Virginia, which had previously operated Douglas B-18s.
A series of failures of the front wheel strut resulted in a delay in bringing the B-26 to full operational status. Although the forward landing gear strut was strengthened in an attempt to correct this problem, the true cause was an improper weight distribution. The manufacturer had been forced to deliver the first few B-26s without guns, and had trimmed them for delivery flights by carefully loading service tools and spare parts as ballast. When the Army took the planes over, they removed the ballast without replacement and the resultant forward movement of the center of gravity had multiplied the loads on the nose wheel, causing the accidents. The installations of the guns corrected the problem.
The last B-26 was delivered in October of 1941. That month, the Martin Middle River production line shifted over to the B-26A version.