The Douglas A-26 / B-26 Invader

v1.0.0 / 01 dec 16 / gv_goebel

* The Douglas Company's A-20 twin-engine bomber proved a significant asset to the Allied cause during World War II -- leading the firm to develop a much-improved follow-on, which emerged as the "A-26 Invader". It went into service too late in the conflict to have much effect in the war, but in the postwar period, as the "B-26", it proved a significant asset in the war in Korea, and served with distinction in Vietnam. This document provides a history and description of the A-26 / B-26 Invader.

Douglas B-26C Invader



* By 1940, the Douglas company was just beginning deliveries of their new A-20 twin-engine bomber -- but the firm was already starting to work on an improved follow-on, the "A-26", in response to a US Army Air Corps (USAAC) requirement for multi-role light bomber, intended for medium- and low-level bombing attacks, and featuring heavy defensive armament -- weak defensive armament having proven a weakness in the A-20. Other changes in the A-26 inspired by the failings of the A-20 included a stronger airframe, better performance, shorter take-off run, and a cockpit with side-by-side instead of tandem seating.

The A-26 design team was led by Ed Heinemann and Robert Donovan. A full-scale mock-up of the A-26 was displayed to Air Corps brass in April 1941, with the government awarding a contract for development in June. Three prototypes were ordered, with the initial "XA-26" prototype performing its first flight on 10 July 1942, with test pilot Ben Howard at the controls. Trials proving satisfactory, it was ordered into production as the "A-26C".

The second prototype, the "XA-26A", was built to the night-fighter specification, featuring airborne intercept (AI) radar in the nose, four 12.7-millimeter (0.50-caliber) M2 Browning guns in a ventral turret, and four 20-millimeter cannon in a belly pack. The US Army Air Forces (USAAF) -- which had superseded the Air Corps -- selected the Northrop P-61 Black Widow for the night-fighter role, and the A-26 night fighter didn't enter production.

The third prototype, the "XA-26B", had a solid nose, fitted with a 75-millimeter M4 cannon mounted on the right side, with "petals" that covered the muzzle of the gun until it was fired. This variant would also be ordered into production, as the "A-26B".

* As it emerged, the A-26 was clearly a descendant of the A-20, an all-metal aircraft with twin radial engines, a mid-mounted wing, and tricycle landing gear -- with a general configurational resemblance between the two aircraft overall, the A-26 being more streamlined and advanced. Flight surfaces were of conventional configuration, the wing having a noticeable dihedral and the tailfin having a leading-edge fillet; flight control surfaces were also conventional, including flaps, ailerons, elevators, and rudder. All landing gear assemblies retracted backwards, the main gear into the engine nacelles. There was a bumper under the tail to deal with tail strikes on take-off.

The prototypes and early production were powered by Pratt & Whitney (PW) R-2800-27 two-row, 18-cylinder, air-cooled radial engines with 1,490 kW (2,000 HP) each, driving three-bladed variable-pitch props. The prototypes had large prop spinners, but they were deleted in production, since they led to engine cooling problems. The internal fuel capacity of the prototypes was 3,795 liters (1,050 US gallons), this being raised in production machines to 6,057 liters (1,600 US gallons).

Defensive armament consisted of remote-control ventral and dorsal turrets, each with two M2 Browning machine guns. The top turret could be turned forward for strafing. The initial production A-26Bs had a 75-millimeter M4 cannon on the right side of the nose and two M2 Brownings on the left; that was quickly changed in production to four M2 Brownings on the right and two on the left. Four packs with two M2 guns each could also be fitted under the wings; with the upper turret adding its weight, that gave an impressive forward firepower of 16 machine guns.

The 75-millimeter cannon had been fitted to the North American B-25G and B-25H, and had not proven all that useful in practice. It had a low rate of fire, and its trajectory did not match that of the nose machine guns, making it hard to register a shot. Unguided rockets would prove much more effective. Incidentally, alternative nose gun armament configurations were evaluated or mocked-up as well:

Along with the glazed nose, the A-26C had two M2 Brownings on the right lower side of the nose, though they were often removed in practice. The A-26C was, in part, envisioned as a "strike leader", with a glazed-nose A-26C to lead a flight of solid-nose A-26Bs to a target, all the aircraft dropping on cue from the A-26C. Except for the nose assembly, the A-26C was effectively identical to the A-26B; indeed, the A-26B and A-26C were so similar that conversions could be, and on occasion were, swapping out noses -- leading to confusions in the number of each variant built. Internal bombload was 1,815 kilograms (4,000 pounds); the A-26 could also carry a total of 900 kilograms (2,000 pounds) of stores on four underwing attachments.

Douglas A-26B Invader

There were three aircrew:

Later A-26 production machines featured significant changes:

Although the A-26 was supposed to go into production in the summer of 1943, USAAF equivocation over the armament configuration, as well as troubles with the complex defensive armament system, delayed production into the fall of 1943, and introduction to service a year after that. Production of the A-26B was at the Douglas plant in Long Beach, California -- these machines being given a "-DL" designation suffix -- while production of the A-26C was at the Douglas plant in Tulsa, Oklahoma, with some A-26Bs produced there early on -- these machines being given a "-DT" suffix.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                21.34 meters        70 feet
   wing area               50.17 sq_meters     540 sq_feet   
   length                  15.62 meters        51 feet 3 inches
   height                  5.56 meters         18 feet 3 inches

   empty equipped weight   10,365 kilograms    22,850 pounds
   max take-off weight     15,875 kilograms    35,800 pounds

   max speed at altitude   600 KPH             375 MPH / 325 KT
   service ceiling         6,375 meters        22,100 feet
   range                   2,255 kilometers    1,400 MI / 1,215 NMI
   _____________________   _________________   _______________________

* The A-26 made its combat debut in the Pacific in July 1944 with the Fifth Air Force on New Guinea. The pilots in the 3rd Bomb Group's 13th Squadron, "Grim Reapers", received the first four A-26s for evaluation. The evaluation was negative, feedback stating the view from the cockpit was unacceptable for low-level attack, and forward-firing armament was inadequate -- which led to the development of the improved canopy scheme and the addition of more M2 machine guns.

Invaders began arriving in Europe in September 1944, initially operating with the 9th Air Force in Western Europe. The first operation of the A-26 was on 6 September, with 18 Invaders conducting an attack on Brest in France. The Invader was faster than the A-20 Havoc, while the range and bomb load were greater, with the type gradually displacing the A-20 and B-26 Marauder. The A-26 served with distinction on the Western and Italian fronts to the end of the war in Europe.

Invaders in Europe were credited with over 11,500 sorties, with seven "kills" of Axis aircraft to their credit, with the loss of 67 Invaders from all causes -- German flak being the worst threat. After the war in Europe ended, A-26s operating from Okinawa continued to perform attacks on Japan and Shanghai, though they only flew a few dozen missions before the end of the war in the Pacific in August.

* A number of A-26Cs were converted to "FA-26C" night reconnaissance aircraft -- the "F" being for "foto" -- with armament usually deleted, and a camera suite installed in bomb-bay, or sometimes the nose. They could drop photoflash flares for night photography, the flares being carried in the bomb-bay. A-26s were also used in trials and evaluations:

The end of the war meant the end of Invader production. Douglas had built 2,503 Invaders in all, including three prototypes, 1,356 production A-26Bs, and 1,144 production A-26Cs. The exact numbers are actually a little vague, since some aircraft were scrapped without being delivered at the end of the war, and as mentioned above, there was some swapping of noses between A-26Bs and A-26Cs. Improved A-26 variants were considered but did not enter production:

After the end of the fighting, the A-26 remained active with some light bomb and reconnaissance units in the USAAF. Although the service was drawn down rapidly after the conflict, many A-26s had remained operational with Air National Guard and Reserve units.



* In 1947, the US Air Force emerged from the USAAF as an independent service; one of the consequences was that the "A" for "Attack" designation code was dropped, with the A-26 becoming the "B-26", to forever cause confusion with the Martin B-26 Marauder, by then fully out of service. In any case, the A-26B, A-26C, and FA-26C became the "B-26B", "B-26C", and "RB-26B" respectively -- all the reconnaissance machines were designated "RB-26B", even though they generally had glazed noses.

There were a number of military conversions of B-26s in the postwar period:

The US Navy ended up acquiring the B-26 in the postwar period. Following the conversion of a B-26A and a B-26C to the "XJD-1" target tug configuration, 150 B-26Cs into "JD-1" target tugs, known as "Jig Dogs" or "Juliet Delta" to crews. They were stripped of armament and brightly painted -- as the old gag goes, to let training pilots know the target was being towed by the tug, instead of pushing it -- and had a winch in the bomb-bay to handing a target sleeve. They had plexiglas nose, smaller than the B-26C glazing, with radar sometimes installed behind it; sometimes the glazing was painted over.

One JD-1 was used as an ejection-seat trials platform, while some of them were later re-converted into "JD-1D" drone controllers to carry, launch, and control Firebee drones. In 1962, when the Pentagon adopted the "tri-service" designation scheme, such JD-1 and JD-1D machines as were still in service were given the new designations of "UB-26J" and "DB-26J" respectively.

* In any case, unlike many other twin-engine bombers left over from the war, a substantial number of B-26s remained in military service following the conflict. That was fortunate, because they ended up being needed again.

When North Korea invaded South Korea in June 1950, the B-26 Invader was one of the few assets readily available to respond. Invaders operating out of Japan performed their first strikes of the war, on a North Korean airfield, on 29 June 1950. US air power quickly negated the North Korean air force, but on the ground, South Korean and US forces were pushed back into the southeast corner of the country, around the city of Pusan.

The North Korean Army was overstretched and had run out of momentum; an amphibious landing at Inchon, the port city of Seoul, threatened the North Koreans with encirclement, and they fled north in disorder. US and South Korean forces then pursued them into North Korea, only to suffer a reversal of their own late in the year, when Red Chinese forces intervened, throwing them back into South Korea. By early 1951, the conflict had settled down into a war of attrition along the border of the two countries.

B-26B Invaders over Korea, 1951

The B-26 Invader was a major player in the conflict, in particular in the night attack role, with the aircraft operating from bases in South Korea. Night strikes were most effectively supported by B-26s or Douglas C-47 "Fireflies" dropping parachute flares. However, in 1951, a number of Invaders were fitted with an underwing searchlight for night attack, though it proved unsuccessful: the searchlight was draggy and clumsy, turning it on blinded the aircrew, and it also drew hysterical fire from the enemy. Searchlight operations were abandoned late in 1951.

Three B-26Cs were fitted with an infrared sensing system, mounted in an overgrown nose fixture, developed by Bell Labs. The IR sensing system was named "mac", after the project engineer, Demetro Mac Cavitch. It was introduced in 1953, near the end of the war, and did result in a few "kills" of locomotives, but the idea wasn't pursued further.

There was a wide range of configurations of RB-26s used in Korea, with different camera fits, as well as provisions for underwing carriage of photoflash flares for night photography. A number of RB-26s were fitted with the AN/APA-64 radar signal analyzer -- designed to locate and characterize adversary radars, originally developed for the Lockheed P2V Neptune maritime patrol aircraft. It appears there were other specialized fits of signals intelligence gear to B-26s, these machines featuring a litter of antennas and fairings, with some of these aircraft serving in Europe to monitor East Bloc activities.

Some of the RB-26s carrying the AN/APA-64 were fitted with AN/APS-15 bombing radar, in a fairing forward of the rear turret, and a "Short-Range Navigation (SHORAN)" targeting system, with the aircraft obtaining a position fix from ground transmitter stations. Some bomber B-26s were also apparently fitted with AN/APS-15 and SHORAN, but such kit could only be used in strikes on fixed targets such as bridges.

B-26C Invader at USAF Museum

The fighting on the ground was largely for political purposes, with the two sides attempting to jockey for position at the bargaining table; air attacks were largely for harassment value or battlefield support. When an agreement was reached in 1953, the B-26s went home -- to then be generally phased out, being replaced in the bomber role by the Martin B-57 Canberra, and in the reconnaissance role by the Douglas RB-66 Destroyer.



* After the Korean War, many B-26s ended up in civilian hands -- for equipment trials; photo-survey; executive transport; and air tanker operations against forest fires. A number of companies performed the conversions, some in ones and twos -- but others were more focused on the exercise. Lynch Air Tankers of Billings, Montana, converted five Invaders to air tanker configuration by adding a 4,540-liter (1,200 US gallon) tank, plus modified wings to permit shorter take-offs and improved maneuverability. These machines were designated "B-26STOL".

The R.G. LeTourneau company of Longview, Texas -- a manufacturer of heavy earth-moving machinery -- converted three Invaders to executive transport configuration for company use. These were relatively modest conversions, involving no major changes to the airframe, featuring six seats for passengers. LeTourneau also sold at least two more conversions.

The Rock Island Oil & Refining Company of Hutchinson, Kansas, performed four "Monarch 26" conversions of Invaders, also with six seats, but with more extensive modifications. The Monarch 26 featured a recontoured fuselage, with panoramic windows, an airstair on the right, a lavatory, and a galley. The Invader's wing spars, which ran through the fuselage, were replaced by a ring spar assembly to free up cabin space. The cockpit featured a metal roof and a revised control layout, while the nose was stretched by 76 centimeters (30 inches) -- to accommodate a baggage hold, weather radar, or other customer-specified kit. Additional fuel tanks were fitted in the outer wings. Rock Island also converted three Invaders to "Consort 26" trials platforms, these aircraft being used by aerospace companies for research and development programs.

The most significant among the firms performing conversions was the On Mark Engineering Company of Van Nuys, California, which began updating Invaders from 1955, to then obtain a license from Douglas to produce parts and provide service for B-26s. The first On Mark executive conversion was the "Marketeer", which was introduced in 1955, featuring unpressurized accommodations for 11 passengers.

On Mark Marketeer Sexy Sue

The Marketeer had wingtip tanks, options for different levels of passenger accommodations, extensive passenger windows, a new cockpit with a covered top, plus an extended nose with a baggage hold. Buyers could replace the original R-2800-75/79 engines, with 1,490 kW (2,000 HP) each, with R-2800-DB-16 engines providing 1,865 kW (2,500 HP) each, raising top speed from 505 KPH (315 MPH) to 585 KPH (365 MPH); a larger rudder had to be installed for the more powerful engines. Although the two wing spars ran through the cabin in early conversions, a ring structure was later fitted that freed up the internal space. Weather radar was optional.

At least 29 Marketeer conversions were performed, with at least two being sold to the US Central Intelligence Agency (CIA). These machines had a roller floor for allowing paradrop of cargos, a multi-mode radar, militarized communications and navigation systems, and possibly defensive countermeasures -- the militarized avionics being installed by LTV's Temco division in Greenville, Texas. The careers of these two machines are obscure. One Marketeer, the US Weather Bureau flew one with a weather radar for weather observations.

The On Mark firm then went on to develop a pressurized Marketeer, called the "Marksman", which also featured a modified fuselage with more headroom. At least a dozen Marksman conversions were performed. However, Grumman introduced the twin-turboprop "G-159 Gulfstream" executive aircraft in 1959, with the intent of taking over the market for executive conversions of World War II twin-piston aircraft; it did so, with jet executive aircraft following, the market for executive conversions of the Invader drying up in the early 1960s. Several Marksmen were used for trials; air tanker Invaders served into the 1970s.

* Although the Invader had a limited future as an executive aircraft, it actually went back to war in a serious fashion -- the US Air Force seeing it as useful for the "counter-insurgency" role as the fighting in Southeast Asia ramped up in the early 1960s. From 1961, RB-26s and B-26s were committed to the theater in the "air commando" role, the fleet being built up to a dozen aircraft; they included a number of "RB-26L" reconnaissance machines, with a modernized camera suite. The old Invaders were essentially clapped-out, with two shedding their wings in 1963 due to cracked wing spars, two others having been shot down. They were withdrawn in 1964.

However, the USAF had already begun work on beefing up the B-26 for the air commando role. A single "YB-26K-OM Counter Invader" prototype was delivered by On Mark in 1962, this machine featuring the eight-gun solid nose, the turrets being removed; a new wing with wingtip tanks, three M2 machine guns in each wing, and four stores pylons under each wing; modernized avionics; and R-2800-103W engines with water-methanol injection providing 1,865 kW (2,500 HP) each, driving square-tipped reversible propellers with neat prop spinners. Speed was increased by over 10%, range was more than doubled, and warload was increased by 60%.

In November 1963, On Mark got a contract from the Air Force to provide 40 "B-26K-OM" machines, these aircraft differing from the prototype by deleting the wing guns and the prop spinners -- as well as using R-2800-52W engines instead of R-2800-103W engines, with the same power ratings. The solid gun nose could be swapped out for a glazed nose, though that wasn't often done. A camera suite for reconnaissance or aerial survey missions could be installed in the bombbay, with bombbay doors featuring camera ports as part of the kit. Initial flight of the first B-26K-OM was in 26 May 1964, with the last delivered in 1965.

On Mark B-26K Counter Invader

Five of the B-26Ks were provided to the CIA, while 30 went to Thailand from 1966 -- where they were redesignated "A-26A" in honor of tradition, the Thais having problems with bombers operating out of their country, but willing to swallow attack aircraft. They were used by the 606th Aero Commando Squadron to interdict traffic on the Ho Chi Minh Trail, which ran through Laos and Cambodia, being used by North Vietnam to funnel troops, weapons, and supplies to support the communist insurgency in South Vietnam. Since the USAF was not supposed to be fighting in Laos, the national insignia on the Counter Invaders was painted out.

The Counter Invaders were finally withdrawn from combat in the theater in 1969, 12 having been lost in operations to that time. Five were transferred to the South Vietnamese Air Force, though they were only used for ground instruction, and were destroyed to prevent them from falling into North Vietnamese hands when South Vietnam fell in 1975. The others had been retired to the Davis-Monthan AFB "boneyard" in Tucson, Arizona, in 1973; it appears that a few had been fitted with the camera suite and used for air survey operations before that time, though details are unclear.



* The first foreign user, of sorts, of the Invader was Britain, which was loaned a USAAF A-26B for trials in 1944; that machine crashed, but two A-26Cs were then provided to the UK for further trials. The British liked the Invader, and were to obtain 140 "Invader Bomber Mark I (B.I)" machines -- but with a number of changes for British service. That stretched out deliveries into 1945, with the end of the war ensuring that the Invader B.Is would not be delivered. After the conflict, the two trials machines were returned to the USA, to be used as target tugs.

The French were the most enthusiastic foreign user of the Invader. A total of 111 B-26s and RB-26s from USAF stocks were supplied from 1951 to support the French war in Indochina. When a cease-fire was declared in 1954, the survivors were returned to the Americans. That wasn't the end of the Invader in French service, however, with the French buying up other Invaders through various channels.

Eight were converted to "B-26N" night-fighter configuration, with AI.X radar scavenged from British Meteor night fighters mounted in the nose. They saw action in the Algerian conflict from 1961, mostly in the ground-attack role. A cease-fire was signed in 1962, with the B-26Ns then being used as bomber trainers up to 1965, when they were retired.

The French also converted 15 Invaders, including a prototype conversion, to the "RB-26P" reconnaissance configuration, featuring a French camera suite. The first RB-26Ps were obtained in 1960, seeing some operational use in Africa before their retirement in 1968. Other French Invaders were used as trials machines, target tugs, and trainers, with the last being phased out in 1968.

Besides France, users of hand-me-down Invaders included Brazil, Chile, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Indonesia, Nicaragua, Portugal, Saudi Arabia, and Turkey. A number of B-26s in Latin American service were upgraded to B-26K standard, with machines also converted to VIP transport configuration. All Invaders were out of military service by the early 1980s.

The CIA was an enthusiastic user of the Invader, with Taiwanese B-26s performing covert night missions with the type over mainland China, under CIA control. CIA-provided B-26s were also used by the Cubans involved in the ill-fated Bay of Pigs invasion of Cuba in 1961, and were employed in the fighting in the Congo in the early 1960s. It appears some Invaders were also obtained by drug smugglers, who appreciated the Invader's high performance.

The Invader not only survives in the form of many museum displays, a number are still flying -- generally in military colors, with dummy gun noses and something dummy underwing munitions. Some of these aircraft belie their warlike paint-jobs with passenger windows, having been superficially "re-militarized" after being converted to executive aircraft following the end of their service careers.



* As a footnote to the Invader story, an Air Force pilot named Jack Krause published recollections of a 1968 mission over Southeast Asia in a B-26K Counter Invader. The tale involved a night mission to perform attacks on the Ho Chi Minh Trail in Laos, with the B-26K flying into a storm marked by the occurrence of "St. Elmo's fire" -- an aerial electrostatic phenomenon well-known to pilots.

Krause got worried about the flexing of the B-26K's wings in the storm, remembering the tales about how some of the earlier batch of B-26s in the theater had shed a wing; the B-26K had rebuilt wings, but the worry still remained. Other worries were about to emerge, taking the night flight into the unreal:


Then St. Elmo made his appearance. The windshield started glowing and sparkling a pale blue all around the edges. Then the side windows started to dance in blue. It was an intensity I had never before experienced, despite many hours flying in weather, including in the Far North where St. Elmo hung out quite a bit.

I peeked out at the wings and saw huge blue bow waves formed on my tip tanks. These fan-shaped apparitions stuck out at least five feet [1.5 meters] in front of the tanks. The armament under the wings also began to glow with huge fan-shaped arcs of blue. Soon the propellers began to produce thick blue corkscrews that trailed over the wings and back into the darkness. Meanwhile, we were being thrown around inside the cockpit with disturbing intensity.

The finale occurred when a string of softball-sized globules of blue formed at the apex of the windshield and rolled between our seats and into the bomb bay. This was mesmerizing, to say the least. I tried to catch one, but there was nothing there.

Two terrifying thoughts entered my mind about then. One was to wonder what the effect all that static electricity was having on the fuzes in the armament we were carrying. The other was how well we must be illuminated for those gunners on the ground. We must have looked just like a slow-moving meteor.


Krause could have unloaded his stores and gone home, but he chose not to. The B-26K got out of the clouds and proceeded to the target area; with ground controllers then informing Krause that they hadn't asked for strikes, had no targets, and suggested the B-26K return to base. Such is the military. The return to base took the B-26K back through the storm again, with St. Elmo's fire just as much in evidence, Krause becoming increasingly exhausted trying to keep the bucking aircraft under control. The B-26K did land safely, after a memorable four-hour flight.

Douglas B-26B Invader

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

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* Revision history:

   v1.0.0 / 01 dec 16