The Douglas XA-26F Invader
Engine test-bed 44-34586 - General
In 1940, the United States, although neutral, was beginning to
support the Allies. GE started expanding to meet their defense needs and built two new plants for turbo production. By mid-1941,
GE turbos were in mass production in four states and were seeing combat service with Allied Air Forces under the Lend-Lease
Moss also led GE in developing its early gas turbine engine, which
in America of the late 1930s, was still experimental and confined to the laboratory. Britain and Germany, on the other hand,
had made steady progress in use of the turbine as a primary source of propulsion. Both Germany's Hans von Ohain and Britain's
Frank Whittle had independently invented the turbojet engine in the mid 1930s.
Finally in 1941, GE received its first contract from the U.S. Army
Air Corps to build a gas turbine engine based on Frank Whittle's design. Six months later, on April 18, 1942, GE's engineers
successfully ran their I-A engine—the first jet engine to operate in the United States. On October 1, 1942, a Bell P-59
powered by General Electric I-16 turbojet engines made its first flight at California's Muroc Army Air Field. The jet age
had come to America. The company followed shortly with the J-31, the first turbojet produced in quantity in the United States.
The XA-26F was a prototype for a high-speed version of the Invader.
A single A-26B-61-DL (44-34586) was modified as the XA-26F prototype. It was fitted with a pair of 2100 hp R-2800-83 engines
initially driving three-bladed propellers but later fitted with four-bladed units with large spinners. In addition, a 1600
lb.s.t. General Electric J31 turbojet was installed in the rear fuselage, with the exhaust pipe in the tail and fed by an
intake above the central portion of the fuselage in place of the usual dorsal turret and gunner position. The eight-gun nose
and the six wing 0.50-inch machine guns were retained. With all three engines running at full power, the aircraft achieved
a maximum speed of 435 mph at 15,000 feet. However, this was deemed to be an insufficient performance improvement over the
proposed A-26D to warrant any production.
General Electric J31 and the XA-26F
The General Electric J31 was the first jet engine produced
in quantity in the United States, essentially a production version of the prototype Whittle
W.1 that had been sent to the US after the Tizard Mission
successes. General Electric's extensive experience in turbocharger production made them the natural choice for producing the engine, which they
initially referred to as the I-16, I-A referring to the original prototype. The USAAF later decided to standardize all their jet engine naming, at which point the
I-16 became the J31.
Like the W.1, the I-16 produced 1,650 pounds force (7.3
kN) of thrust and weighted about 850 lb. Production started for the P-59
Airacomet in 1943, and by the time the lines shut down in
1945, a total of 241 had been built. GE also used the basic design to produce the much larger I-40 with 4,000 lbf, but this
design was passed on to Allison Engine as the J33, much to GE's chagrin.
Serial #: 44-34586
Construction #: 27865
Last info: 1972
Lindsay Hopkins Vocational School, Miami Airport,
- Registered as N66368
Built as DOUGLAS XA-26F
- Prototype for a high-speed version of the Invader
out as an A-26B but modified in late 1945 as XA-26F with J31 turbojet aft of bomb bay.
the years 1950 and 1951 flew for Shell Oil Co. on a bailment contract for the USAF doing fuel research.
to Lindsay Hopkins Vocational
School in the 1950s, and was on the civil registry at least
1964-1969 as N66368.
used for ground instruction at the George T. Baker aviation school in Miami Airport and reportedly scrapped in 1972.
XA-26F - Chief test pilot - Gene May
Serial no. 44-34586 prototype for a high-speed A-26F powered
by two 2,100 hp R-2800-83 engines driving four-bladed propellers with a 1,600 lb.s.t. General Electric J31
turbojet installed in the rear fuselage. The prototype reached a top speed of 435 mph but the series was cancelled as performance
gains were not sufficient.
On June 1946, the XA-26F covered a 621-mile (1000
kilometer) course with a 1000 kilogram load at an average air speed of 413 mph. The aircraft was being flown by Lt. Col. T.P.
Gerrity and Capt. W.K. Rickert (Pictured above) With all three engines operating, the XA-26F reached a top speed of 435
mph at 15,000 feet."
Records set by the XA-26F
Speed over 1000 km with 1000 kg payload : 660.53
Date of flight: 20/06/1946
Pilot: T. P. GERRITY (USA)
Crew: W.K. Rickert
Course/place: Dayton, OH (USA)
Douglas XA-26F (Wright R-2800-83
and GE-1-16, 2000 hp/1600 lbs)
Sub-class : C (Aviation with engine)
refuelling in flight
Speed over 1000 km with 1000 kg payload : 660.53 km/h
Date of flight: 20/06/1946
Pilot: T. P. GERRITY (USA)
Crew: W.K. Rickert
Dayton, OH (USA)
Douglas XA-26F (Wright R-2800-83
and GE-1-16, 2000 hp/1600 lbs)
- Prototype for a high-speed flight
Serial no. 44-34586 prototype for a high-speed A-26F
Powered by two 2,100
hp R-2800-83 engines driving four-bladed propellers with a 1,600 lb.s.t.
General Electric J31
turbojet installed in the rear fuselage.
The prototype reached
a top speed of 435 mph but the series was cancelled as performance gains were not sufficient.
To aviation historians,
the end of the Second World War in Europe was loaded with what-ifs? The majority of these speculations resided with the Luftwaffe and Nazi
Germany's attempt to get various advanced
aerial weapons into production and, more importantly, into combat. However, the Allies had smashed the Nazis and their very
limited production capability so these "what-ifs" are mainly idle speculation - especially in the light that the Luftwaffe's
new state-of-the-art warplanes such as the Me 262 were negated by poor production quality, lack of adequate fuel and supplies,
and misguided higher command decisions on how they should be produced and deployed. Also, Allied air superiority just about
negated any use of advanced warplanes for, once airborne, they would be swarmed by hundreds of fighters.
The newly-emerging jet
engine technology was not lost upon Douglas who was busy developing the very advanced XB-42 (piston) and XB-43 (jet) series
of bombers. However, they also knew that the A-26 Invader had very high performance and speculated how that performance could
be enhanced if jet power was somehow incorporated into the airframe. At the same time, propeller technology was advancing
so Douglas approached the USAAF with a proposal for a mixed power Invader and a contract
was issued to convert A-26B-61-DL s/n 44-34586 to an experimental mixed-power platform.
Given the designation XA-26F, the modifications were fairly straightforward.
The extra powerplant was a General Electric Model 7E-116-4 gas turbine and to install the unit in the rear fuselage, the gunner's
sighting station and all related equipment was removed. The upper and lower turrets were also removed along with the Station
0 armor plate. The electrical equipment in the former gunner's compartment was relocated along with the radio compass. The
SCR-695 (IFF) radio and radio compass loop antenna were also relocated while the aft portion of the flight control cables
had to be rerouted.
A large air scoop for the jet was added atop the fuselage while
the tail cone was refashioned into a tail pipe. A long exhaust pipe and shroud assembly ran from the engine to the tail cone.
Under where the top turret would have been, a 125-gallon fuel cell was installed to hold the jet's Spec. AN-F-32 Grade K JP-1
(kerosene) fuel along with an eight-quart tank for the AAF Spec. 3580D medium grade oil. The fuel system was controlled by
the operation of a master switch and the throttle. Fuel pressure ranged from 20 psi at engine idling speed to 380 psi maximum
engine operating speed. The turbine would act as an assist to improve combat performance and make takeoffs possible from short
runways or with extra heavy loads.
All flight controls, their maintenance and operation, remained unchanged
except for cable routing in the vicinity of the aft engine installation. The throttle for the aft engine was isodraulically
operated. This unit was self-contained and was in no way connected to the airplane hydraulic system.
The XA-26F was not to be a stripped-out test vehicle for it carried
an eight-gun nose and a six-gun wing. Also, large four-blade paddle-style propellers had been added along with a set of spinners
that had been made for the prototypes and early production aircraft. The engines were P&W R-2800-83s capable of 2100-hp
Before serious testing could really get underway, the war was over.
However, the Air Force considered the XA-26F an important test vehicle and continued flying the aircraft in different configurations.
On June 1946, the XA-26F covered a 621-mile (1000 kilometer) course with a 1000 kilogram load at an average air speed of 413
mph. The aircraft was being flown by Lt. Col. T.P. Gerrity and Capt. W.K. Rickert. With all three engines operating, the XA-26F
reached a top speed of 435 mph at 15,000 feet.
With a whole new generation of jet warplanes on the horizon, it
was obvious that it would not make practical sense to convert operational Invaders to the A-26F configuration. However, this
did not mean the prototype's career was over.
Fitted with standard propellers and minus the spinners, the XA-26F
was assigned to the Shell Oil Company in late 1949 for flight test work. Two oil company engineers were positioned in the
cockpit while another two were crammed into the rear fuselage along with the jet. Under the direction of D.N. Harris, Shell's
Project Engineer of Flight Research, the XA-26F was operated on numerous flights between Los Angeles
and Oakland, California,
to obtain experimental data on aviation fuels.
As one flight test engineer stated in a period publication, when
both P&Ws were running at full power and the jet cut in it was like, "a kick in the butt."
When this valuable research was concluded in the 1950s, the XA-26F
was stored for a period and then transferred to a technical school in Florida
where it survived until the early 1970s when it was scrapped.
Under wing cargo or personnel carrier
One unusual use of the B-26 was for use in
a program designed to test the feasibility of droppable cargo containers. At least two B-26s, B-26B 44-34606 ( Which was accidently
shot down by 64-17668 in 1966 and crashed into the sea ) and B-26C
44-35678 were used for this program and modified to carry the container under its right wing. A suspension apparatus was attached
to the underside of the wing and a remote release mechanism was installed. The idea was to resupply forward operating bases
and other inaccessible or hazardous areas without access to normal airlift, for example, frontline troops engaged in battle
or aircrew members after an emergency/crash landing.
The container itself was a streamlined box with access panels
built into the side for loading and unloading supplies. The "landing gear" consisted of a pair of skids in the center and
a small wheel and tire at the nose. Various configurations were tested for stability in flight (vertical stabilizer added)
and ruggedness on the ground.
The test program was marginally successful; however, advances in precision and low level
air drops by more conventional cargo/transport aircraft made the use of combat aircraft to deliver supplies impractical for
||At least 2
||Special Project test aircraft|
Below shows 44-35678 being used as a test bed for a carrying system to supply
troops in forward combat areas.
Each wooden pallet was fitted with landing skids and a nose wheel,
allowing it to be dropped at low altitude into small field and open areas.
The above shot shows "606" ptior to her accident with 64-17668
Drogue chute test aircraft
Drogue chute test aircraft
One B-26B was used for testing drag
and braking chutes and designated EB-26B (exempt). This aircraft was extensively modified for this test program and had a
very unusual configuration. For a typical test, the EB-26B would accelerate up to landing speeds and deploy the test chute
to determine its effectiveness. Since the aircraft didn't need to actually fly, major modifications were done to make the
aircraft as light as possible and therefore decrease the amount of time and runway needed to get up to the necessary test
speed. The most obvious modification was the removal of the wings outboard of the engine nacelles. For this reason the aircraft
was nicknamed "Wingless Wonder." Further weight savings were gained by removing all armament and even the landing gear doors.
A test apparatus was fitted to the tail section and varied based on the type of chute or deployment mechanism being
tested. For example, if a new aircraft design called for a downward opening drag chute compartment, a mockup was built and
fitted to the EB-26B for testing. Other tests compared different types and sizes of chutes for stability and effectiveness.
The EB-26B was used as a test aircraft throughout the early 1950s.
||"Wingless Wonder" test bed|
Engines: Two Pratt & Whitney R-2800-27 radials of 2,000 hp each
Approx. 150 mph (aircraft could not fly)
Span: N/A (outer wings were removed)
50 ft. 8 in.
Height: 18 ft. 6 in.
Serial number: 44-34137 (originally A-26B-45-DL)
The A-26B pictured is s/n 44-34137 which was used in the
forties to conduct parachute braking tests. The outer wings, landing gear doors and other equipment was removed to lighten
the aircraft so it could reach speeds simulating an aircraft that had just landed. After the trials ended in 1948, this Invader was scrapped. Several types of parachutes were tested, not only the type shown on the photo.
I think the Air Force itself conducted these tests.
Photo -Recon with targeted flash bombing system
Photo -Recon with targeted flash bombing system
The B-26K was designed with an interchangeable nose section, which could
changed from the eight .50-cal. machine gun solid nose to a bombardier's nose with clear sections. A reconnaissance "pallet"
was designed to be fitted into the bomb bay as a unit consisting of five reconnaissance cameras, including a panoramic camera
with in-flight photo processing capability. The bomb bay package also included photo flash bomb ejector racks for night reconnaissance
missions. Special bomb bay doors with openings for the cameras and photo flash bomb ejectors allowed the bomb bay doors to
remain closed during reconnaissance missions. The clear nose of the RB-26K had an optically flat panel for use with a forward
oblique reconnaissance camera. The tail housed a vertical camera.
The RB-26K was capable of flying armed reconnaissance
missions. The forward guns and internal bomb bay were replaced with cameras, but the eight wing pylons could still carry up
to 8,000 pounds of mixed ordnance depending on mission requirements. Typically, wing ordnance was not carried to increase
the speed of the aircraft.
Armament: Eight wing pylons capable
of carrying 8,000 lbs. of mixed ordnance
Engines: Two Pratt & Whitney R-2800-52Ws of 2,500 hp (maximum
with water injection)
Maximum speed: 323 mph/281 knots
Cruising speed: 310 mph/270
Range: 2,700 statute miles/2,346 nautical miles
Service ceiling: 30,000 ft.
71 ft. 6 in.
Length: 51 ft. 7 in.
Height: 19 ft.
Serial numbers: 64-17640 to 64-17679
The 6' Square windows were for the KA-56A panoramic mirror camera
system which was equipped with an automatic in-flight processing system. Similar cameras were in service in WW2. The later
F-492 camera system required 6" diameter windows in the bay doors.
A K-38 forward obligue recon camera was mounted looking
through the bombardier's optically flat panel. In addition there was a P-2 vertical camera in the tail.
Flash bombs were
not dropped from the forward part of the bomb bay as previously stated as the bomb bay doors could not be opened in flight
wothout disrupting the camera mountings by the air stream regardless of the three air flow disrupters in front of the bomb
Flash bombs were carried on the underwing hard points.
Flares were dropped from the standard flare tube system
mounted in the bomb bay.
RB-26C Tactical Recon Squadron, special mods
FA-26C was a reconnaissance conversion of the A-26C. Between 1945 and 1947, the F (secondary) prefix letter was assigned to
aircraft when the primary mission was changed to reconnaissance. In this case, an A-26C modified for the reconnaissance role
was re-designated FA-26C. Beginning in 1930 and prior to 1945, the F designator was used as a primary prefix for reconnaissance
aircraft. For example, a P-51, built as a photo recon aircraft, was designated F-6 (not FP-51).
Only a few A-26Cs
were modified for reconnaissance duties. Modifications typically involved removing all guns and installing cameras throughout
the aircraft. Additionally, an aircraft intended for night reconnaissance was equipped with photo flash bombs. Some aircraft
were also modified for electronic reconnaissance with the installation of radar and signal intelligence gathering equipment.
In 1948, the USAF dropped the F designator for reconnaissance aircraft and replaced it with the R designator. The
F designator was reassigned to fighter aircraft. At the same time, the A (attack) designator was dropped and the A-26 was
reclassified as a bomber. Thus the FA-26C was re-designated RB-26C.
With the start of the Korean War in June 1950,
the USAF had very little tactical reconnaissance capability. As a result, the USAF ordered more RB-26C conversions for night
The RB-26B, or simply
RB-26, was a reconnaissance conversion of the Douglas B-26. When the Korean War began in June 1950, the 3rd Bomb Group (Light)
was equipped with B-26Bs and stationed in Japan. This group had only two bomb squadrons initially (8th and 13th), but was
pressed into immediate service, first covering the evacuation of U.S. citizens from South Korea in the first few days of the
war and later in the interdiction mission. The B-26Bs were first used to attack North Korean ground targets (truck convoys,
trains, rail lines, bridges, etc.) in daylight and achieved significant results. However, as the losses to B-26 interdiction
raids became unacceptable, North Korea started moving supplies primarily at night.
In early July, the 162nd Tactical
Reconnaissance Squadron (Night Photo) was told to move from Langley Air Force Base, Va., to Itazuke Air Base, Japan to begin
flying reconnaissance missions as soon as possible. Supply delays with a new photo flash bomb system prevented the 162nd from
beginning operations until August 1950. In September, the 162nd was assigned to the 543rd Tactical Support Group and in October
the group moved from Japan to Taegu Air Base, South Korea.
The 162nd TRS was equipped with 16 RB-26s initially, but
total combat-ready strength never rose above 20 aircraft. The mission of the squadron was to take night reconnaissance and
damage assessment photos. However, the new photo flash bomb system was prone to failure and the flash bombs had a relatively
high dud rate.
Because there were no preexisting tactics for night intruder (interdiction) missions, various techniques
were tried, some involving RB-26s and B-26Bs in Hunter-Killer pairs. The reconnaissance aircraft would seek targets and when
found, drop parachute flares to mark the location and call the B-26B to attack. This technique didn't work very well since
the mobile ground targets usually moved away from the area illuminated by the flare or rapidly dispersed off the roadway.
Other techniques tried included adding a seven million candlepower searchlight to the aircraft. The aircraft with
the light was accompanied by one or more attack aircraft and would light a target area for a short time allowing a more effective
attack. There were two major drawbacks to this plan: first, the searchlight made an excellent target for enemy gunners and
second, the light had a very limited time of operation (less than a minute).
Eventually, night interdiction tactics
evolved so the RB-26 was not needed. Improved night photography aircraft were available early in the war and the 162nd TRS
was deactivated on Feb. 25, 1951.
The RB-26 designation was used beginning
in 1948 after the USAF dropped both the attack (A) and reconnaissance (F) designations. All FA-26s still in service were re-designated
as RB-26s. Limited numbers of B-26Bs and B-26Cs were converted for use as reconnaissance aircraft. The gun turrets were removed
and the bomb bay adapted to carry additional equipment depending on the intended mission. For example, night reconnaissance
aircraft were fitted with a photo flash "bombing" system. The converted aircraft generally used the simple RB-26 designation,
although aircraft fitted with a bombardier's (clear) nose could be RB-26C, while the solid nose type was the RB-26B.
When the Korean
War began in June 1950, the Air Force had an urgent need for tactical night reconnaissance aircraft. The 162nd Tactical Reconnaissance
Squadron was moved from Langley Air Force Base, Va., to Japan and began flying missions in August 1950. During the first year
of the war, RB-26s flew 2,305 effective sorties. The RB-26 retained a limited offensive weapons capability when rockets or
bombs were loaded on wing racks and during the first year of the war, 342 tons of bombs were dropped and 120 rockets were