B-26 Marauder Variants

Initial version used primarily for development and training. It was powered by two Pratt & Whitney R-2800-5 radials rated at 1,850 hp. (1.380 kW) each. It could carry up to 5,200 lb (2.359 kg) of bombs in a wide variety of sizes and numbers.

The original aircraft was armed with just 4 guns: 2 in a dorsal turret, 1 in the nose position, and 1 in the tail position. It was the fastest of all versions, reaching 315 mph (507 km/h) at optimum altitude.

Externally identical to the B-26 but with additional Dural armor plate. Goodyear rubber self-sealing fuel tanks replaced the original Mareng units. Other modifications included:

• A new 24-volt electrical system (was 12V);
• Shackles for one 22 inch (559 mm) torpedo weighing 2,000 lbs. (907 kg) or two 1,600 lb. (726 kg) bombs;
• The .30 caliber gun in the nose position was replaced with a 0.50 inch (12.7 mm) model;
• Fittings for for a second releasable 250-gallon gas tank in the forward bomb bay;
• A low pressure oxygen system;
• A 100-amp generator.

These changes added nearly 2,000 lbs.  The Pratt R-2800-5 engines remained but in the Ford license-built versions. The AAF also ordered all previous production aircraft to be modified to the A-model configuration and the B-26 and B-26A became virtually identical in service.

Due to a shortage of R-2800-5 engines, in late October, 1941, the AAF ordered Pratt & Whitney to divert 200 R-2800 S1A4Gs ("A" engine - 1,850 hp.) and 222 R-2800-2SB-Gs ("B" engines - 2,000 hp.) from an RAF order to Martin. These were redesignated by the AAF as R-2800-39s and R-2800-41s respectively.

The switch to -39 engines on the Baltimore assembly line began with aircraft 41-7366. These Marauders were designated B-26A-1s but were otherwise identical to the B-26A.

Built at Baltimore, Maryland from May 1942 onwards and based on the A-model, this was the first modification involving significant external changes.  Delivery commenced on April 5, 1942:

• The tail gun position was completely redesigned with the single .30-caliber replaced by two 0.50-caliber guns in a new "stepped" tail arrangement;
• Increased armor;
• The aicraft's overall length increased to 58 feet, 3 inches;
• Torpedo racks under the fuselage were now the factory standard
• The oil cooler air scoop under the cowling was enlarged;
• Engines were switched from the R-2800-39s of the B-26A-1s back to the R-2800-5s.

From July, 1942, these models, mostly assigned to units headed for the North African theater, were flown from Middle River to Martin's Omaha Modification Center and reworked. So many modifications were made that these planes unofficially became known as "B-26B-1s":

• The nose plexiglas was strengthened to fit a centerline flexible-mounted .50-caliber gun;
• A fixed forward-firing . 50-caliber machine gun was installed in the lower right-hand side of the nose;
• The two .30-caliber waist and single tunnel gun were replaced by flexible Browning . 50-calibers;
• Two circular lenses to improve visual scanning were added above each waist gun position;
• Provisions for two additional 250-gallon ferry tanks in the rear bomb bay. Total fuel capacity increased to 1,962 gallons and maximum ferry range to 2,850 miles, but takeoff weight also went up considerably.
• The engine cowling top air intakes were made much larger to accommodate sand filters;
• The flat plexiglas windows on both sides of the fuselage (adjacent to the Radio Operator/Navigator table) were replaced with "bulged" ones to enhance downward viewing;
• The large propeller spinners were permanently removed to improve engine cooling and reduce maintenance;
• Maximum takeoff weight increased to 36,500 lbs. (16.556 kg) and required more powerful engines.  The 306th and later aircraft were powered by two Pratt & Whitney R-2800-41 or R-2800-43 radials rated at 1,920 hp. (1.432 kW) each;
• Slotted flaps were installed to to reduce landing speed.

In May, 1942, Pratt & Whitney began delivering upgraded R-2800-41 engine ("B" series - 2,000 hp. takeoff-rated) to Martin's Middle River production line.  Marauders built with this powerplant were designated B -26B-2s with the first delivered on June 17, 1942.  Additional modifications included:

• A "whip" antenna on the belly just aft of the nose wheel door for a new VHF radio.

In the fall of 1942, the slightly-modified Pratt & Whitney R-2800-43 engine (2,000 hp takeoff-rated) became available and were installed on 28 Marauders,which were designated "B-26B-3s". Most of these also received all B-26B-1 modifications at Martin's Omaha facility.

Production of this model at the Baltimore line began in September, 1942 with the 431st aircraft of the "B" series. The Marauder's gross weight was steadily increasing with added equipment and armament, and wing loading, already high in the original design, eventually rose to a marginally safe 63 lbs./sq. ft. In fact, the B-26B-4's wing loading was exceeded only by the German Do 217 (64 lb./sq. ft.), highest of all the medium bombers of World War II.

Many North African-bound B-26B-4s also received the "B-26B-1" modifications. Significant changes included the following:

• The nose gear strut was lengthened by six inches to increase the wing's angle of attack in an attempt to improve takeoff performance. A bulge was added near the front of the gear doors to clear the repositioned retracting mechanism. The longer strut gave the B-4 variant a distinct "nose-up" attitude on the ground;
• Mechanically operated main wheel landing gear doors were incorporated starting with this variant. Built in three sections, two were closed when the landing gear was extended to cut drag. Retractable circular air ventilators were added beside pilot and co-pilot positions;
• 4 forward-firing .50-caliber fixed guns in "blisters" were mounted on each side of the fuselage below the Radio Operator / Navigator compartment. This brought total gunnery armament to twelve Colt-Brownings.

To decrease wing loading, Martin was directed to increase wing area to 713 sq. ft. by broadening the chord and lengthening span to 71 feet. This reduced wing loading to a safer 51.5 lbs./sq. ft.  However, increased weight and drag reduced the "long wing" Marauder's maximum speed to about 282 mph at 15,000, and cruising speed to 214 mph. With a load of 4,000 lbs. of bombs and 962 gallons of fuel (no bomb bay tanks), the "long wing" had an operating range of about 550 miles. 

Marauders built at Omaha were now to have the suffix "MO", and the original B-26Cs from the Nebraska plant were subsequently redesignated B -26C-05-MOs. Other significant modifications included:

• A larger vertical larger tail;
• Overall, the plane was increased to 58 feet,3 inches long, and height to 21 feet, 6 inches;
• Due to the larger and heavier wing and tail assembly, and additional armament and armor, weight increased by 1,500 lbs. to 26,300 pounds basic, 31,200 lbs. normal (DGW) and 37,000 lbs. loaded;
• The 47 inch main gear tires were reaplaced with 50-inch versions on a larger wheel, requiring the addition of a streamlined bulge to the gear doors for clearance;
• An improved hydraulic system;
• Exhaust stack flame dampers;
• 200 amp generators (up from 100);
• Shorter co-pilot's seat to provide easier access to the nose compartment;
• B-26B-1 gunnery armament and B-26B-4 forward-firing, blister-mounted guns made standard;
• The waist gun doors were enlarged and moved one station aft to improve downward and forward angle of fire. They were slid up and locked open before firing;
• A large circular window, replacing the two previous smaller ones, was added above each waist door to provide better visibility for the gunners;
• The bomb bay racks and hoisting equipment were improved;
• The Bombardiers' station was improved and the optically flat glass In the lower nose enlarged and elongated to provide a better view during the target run.
• From the 61st aircraft of this model onwards, the nose and main gear doors closed when the gear was fully extended (to reduce drag).

In early 1943, the AAF ordered a weight reduction test program aimed at improving landing and takeoff performance. Omaha-built B-26C-5-MOs to be assigned to the England-bound 323rd Bombardment Group, were substantially lightened by removing the co-pilot's seat. control collumn and armor plating, along with other equipment including the liaison radio set.

Two 323rd squadrons flew some combat missions with this configuration, but commanders objected so vehemently to the loss of the co-pilot position that the experiment was abandoned. All of these single pilot aircraft were eventually converted back to a the standard two-pilot configuration.

The last 150 "B" model Marauders (642nd to 791st articles, 41-18185 through 41-18334) from Middle River were manufactured as "B-26B-1O-MAs", identical to B-26C-5- MOs. The first B-10 was accepted on January 15, 1943. The suffix "MA" designated aircraft built at Baltimore.

By March of 1943, the Martin Omaha plant had made the changes required by the Baltimore Engineering Department and began producing B-26C-10-MO models, Identical to the B-26B-10-MA.

The block of 100 Baltimore-built Marauders serialed 41-31573 through 41-31672 were designated B-26B-15-MAs. They differed from the B-26B-10 only in having the fixed oxygen system Type A-9 regulator removed and improved IFF equipment (SCR-595A) fitted.

The Martin Omaha plant also incorporated these changes in aircraft 41-34908 through 41-34997, which were then designated as "B-26C-15-MOs".

Beginning with the B-26B-20-MA and B-26C-20-MO:

• The hand-held twin .50 caliber guns in the tail position were replaced with a power-operated electromechanical Bell M-6 turret. The new, bluntly rounded position significantly altered the Marauder's tail profile and reduced overall length to 56 feet, 1 inch.
• A shorter chord rudder was installed.

These aircraft featured more armor plate on the Martin 250CE turret. Some of these aircraft destined for Stateside training and other non-combat uses were not fitted with the Bell tail turret.

For the C-25-MO models headed for the Mediterranean theater of operations, the Martin Omaha plant installed a collector pan beneath the tail guns to hold spent cartridge casings.

Three B-26C-25-MOs, serials 41-35370 through 41-35372, were converted to AT-23Bs.

• A curved piece of armor plate was mounted externally on the left side of the fuselage to protect the pilot.
• Additional armor was also added behind the Bombardier position and around vital mechanical parts of the plane in several locations.

One hundred B-26B-30-MAs were built at Baltimore while 200 B-26C-30-MOs were made by Martin-Nebraska.  Forty-eight B-26C-30-MOs were converted to AT-23Bs with serial numbers 41-35525 through 41-35572. The 100 C-30 models assigned to the RAF were known as the "Marauder II".

The carburetor alcohol de-icing system was eliminated and that was the only change in this block of 100 B-26B-35-MAs and 200 identical B-26C-35-MOs.

23 aircraft, 41-35598 through 41-35620, were converted from B-26C-35-MOs to AT-23Bs at the Martin plant in Omaha.

• A torpedo firing switch was added to the pilot's control column with this version;
• The type B-2 Torpedo Director was discontinued;
• The carburetor air duct was revised for hot air de-icing from the middle of this block (42-43320) forward;
• "Shark nose" ailerons were used from aircraft 42-43310 on.

The Martin Baltimore plant built 200 B-26B-40-MAs of which 141 were eventually converted to AT-23As (Serials Nos. 42-43319 through 42-43459). The Martin Omaha plant manufactured 100 B-26C-40-MOs and all were subsequently converted to AT-23Bs.

• A ring-and-head sight was mounted on the pilot's panel for aiming the 4 fixed blister-mount guns;
• Stronger bomb hooks for the B-10 shackles were installed;
• A new SCR-695 IFF system was added;
• An SCR-522 VHF command radio set with accessories was added.
• The engine fire extinguisher was reinstated as standard equipment.
• A remote heading compass was installed.
• Based on combat experience, the Army Air Force's original requirement for the ability to carry thirty 100-pound bombs was dropped.  The aft bomb bay was therefore bolted shut from this variant onwards and used to store tail gun ammunition. A special track was installed to carry ammo back to the tail gun position (about 28 feet).
• The fixed .50-caliber machine gun In the nose was deleted in the middle of the production run (from 42-95979).

109 B-26B-45-MAs (Serial Nos. 42-107856 through 42-107881) were converted to AT-23Bs.

• An emergency mechanical bomb bay door closing mechanism was added;
• A modified IFF system was installed;
• Lycoming propeller blades were used from aircraft 42-95942 onwards;

Two hundred B-26B-50-MAs were built at Baltimore.

• The D-8 bombsight was replaced with an M-series unit.
• Several changes to the Martin CE 250 top gun turret (optical sight, etc.) were incorporated from aircraft 42-96079 onwards.
• Camouflage paint was no longer applied to aircraft built at the Baltimore plant from Serial No. 42-96129 onwards.

Two hundred B-26B-55-MAs were manufactured.

This first example of this variant came off the Middle River line in February, 1944.  Changes included:

• Wing incidence was increased by 3.5 degrees to 7 degrees. This configuration provided better ground clearance for the propellers, improved lift, reduced takeoff run and landing speed.  This was the final significant structural change to the B-26 program. Airborne, the "F" no longer gave pilots the impression that it was flying with a "nose high" attitude. Unfortunately, maximum speed was reduced to 277 mph. and overall handling characteristics were slightly degaded.
• Torpedo shackles were no longer installed from this model onwards;
• An all-electric bomb release system was installed;
• From aircraft 42-96231 onwards, a revised oil cooler with thermostatic control and a surge valve was used;
• Wing lower access panels were redesigned for easier removal;
• Several changes were nade to the instrument panel;
• The trailing antenna was made removable;
• An improved fuel transfer system was installed and a cross-feed added to main fuel tanks, although the system was not yet functional on this variant.
• An emergency landing gear extension system was installed.

These two groups of identical aircraft were built for the RAF and SAAF as "Marauder IIIs", (Serial Nos. HD 402 through HD 601).

• The Bell M-6 power-boost tail turret was replaced by the M-6A with a flexible canvas cover over the end of the gun position;
• Optical gun sight mounts were added to the flexible machine guns;
• A T-1 bombsight replaced the M-series;
• Provisions for British nose and tail bomb fusing and B-9 bomb shackles were added;
• Radio equipment was modified to British standards.

The model started production on the Baltimore kine in March of 1944. It was essentially identical to the the B-26F except for inrenal equipment:

• An armor "blanket" was added to protect the fuselage from the blast of the blister guns;
• From aircraft 43-34190 onwards, a C-1 autopilot system was added by request of the Ninth Air Force;
• Partial top-surface camouflage paint was applied at the factory;
• Inboard and outboard wing fuel tanks were connected via a crossfeed;
• Universal "Army/Navy" instead of "Air Corps" equipment was installed;
• The life raft compartment in the top, forward fuselage was made larger to acommodate an A-3 or E-2 rubber dinghy, provisions, and a dinghy radio.

The G-10-MA variant was built for the USAAF and the G-11-MAs for the RAF and known as "Marauder Ills". 

Changes included:

• A cartridge casing collector under the tail gun position was made standard;
• The lock valve cowl flap system was no longer used from aircraft 43-34575 onwards;
• Some of these aircraft received Lycoming propellers.

• The C-1 Automatic Pilot was no longer installed;
• The radio compass was modified.

In November of 1944, the last ten aircraft of this block (Serial nos. 44-67945 through 44-67954) were converted to training and target-towing duties and designated as "TB-26-15-MAs" .

• Whip-type static dischargers were added.

Fifteen planes of this block (Serial nos. 44-67955 through 44-67969) were built as TB-26G-20-MAs and 75 were designated B-26G-21-MAs (Serial Nos. 44-67990 through 44-68064) and turned over to the RAF where they were numbered HD677 through 751 and called "Marauder Ills".

This was the final production variant with only minor changes. Tthirty-two of these (Serial nos. 44-68222 through 44-68253) were stripped of armament and operational equipment in March, 1945, to serve as TB-26G-25-MA trainers and target tugs.

The last Marauder built left Martin's Middle River production line on April 18, 1945. It was B-26G-25-MA (Serial No. 44-68254) named "Tail End Charlie" and "30".