Douglas A/B-26 Invader

Power plants used by the A/B-26 in research and development














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Because of the post availabiliy of the A-26 Invader, the aircraft was subject to many tests involving airframe and engine modifications.
The US Navy ( JD-1 Invader ) tested the aircraft as a Ramjet platform and as can be seen on this page, several other companies took advantage of its durability and adaptability.

Associated reading

Engine testbed 44-34523 - Garrett Corporation

 
 
 
The below seven shots are from the Graham Robson collection, provided by Allied Signal.

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Serial #: 44-34523
Construction #: 27802
Civil Registration:
  N9174Z
  C-GTOX
Model(s):
  A-26B
  B-26B
Name: Hasta Luego
Status: Airworthy
Last info: 2002

 

History:
On Mark Engineering Co, Van Nuys, CA, 1963
- Registered as N9174Z.
Garrett Corp, Los Angeles, CA & Phoenix, AZ, 1964-1977
- Modified for turboprop engine in nose position.
Air Spray Ltd., Red Deer, Alberta, Jan. 1982-2002
- Registered as C-GTOX
- Flown as tanker #14/"Hasta Luego".

Engine testbed 41-39221 - Garret AiResearch Corporation

 
 
 
The below eight shots are from the Graham Robson collection, provided by Allied Signal.

Thanks to Graham Robson, here we have the only interior photos and panel shots of the surviving Marksman conversion.

marksman6n256hpanelfeb1986.jpg

marksman6n256h7panelfeb1986.jpg

marksman6n256h61981.jpg

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w5marksman6n256hgarrett6tpe33114.jpg

marksman6n256h1981.jpg

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airresearchinvader.jpg

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Finalising the engine cowl for the nose-mounted TPE 331

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Serial #: 41-39221
Construction #:
  6934
Civil Registration:
  N9636C
  N3035S
  N256H
  N25GT
Model(s):
  A-26B
  B-26B
  Marksman
Name: None
Status: Display
Last info: 2002

 

History:
Farrah Manufacturing Co Inc, 19??.
- Registered as N9636C.
Southern Natural Gas Co, Birmingham, AL, 1963-1966.
- Registered as N3035S (1).
Mapco Inc, Tulsa, OK, 1969.
- Registered as N256H (2).
Bancroft Manufacturing Co., McComb, MS, 1970-1972.
Park Meadow Inc/Ligon Air Inc, Ligonier, In.
Garret Corp, Phoenix, AZ, Circa 1979.
- Modified for testing the TPE 331 turbine engine which was mounted in the nose.
Garret AiResearch Corp, Phoenix, AZ, Apr. 1983-1988.
- Registered as N25GT.
- Used for engine testing.
Allied Signal Inc, Phoenix, AZ, Dec. 1988-1992.
Struck-off USCR, Jan. 10, 1992.
South Mountain High School, Phoenix, AZ, 1992-2002.
- Donated to Aviation Technology program.
- Displayed.

 
The Garrett T76 Turbo-Prop.
 
This gas turbine engine was designed as both a turboshaft (TSE331) and a turboprop (TPE331).  The turboshaft version never went into production; however, over 14,000 TPE331s have been sold.  The military version was designated the T76 and has the air inlet above the engine unlike most commercial versions.
 
Specifications
Turboprop (single shaft)
Compressor: two-stage centrifugal
Turbine: 3-stage
Mass flow: 5.8 to 11.6 lbs/sec
Power: 1,040 hp (776 kW)

 
The Garrett T76 Turbo-Prop

800px-turboprop_cutaway.jpg

Engine testbed 44-34586 - General Electric (XA-26F)

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.

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 program.

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.

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.

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 each.

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.

 
Specifications GE-J31

General characteristics

  • Type: Turbojet
  • Length:
  • Diameter:
  • Dry weight: 850 lb (386 kg)

Components

  • Compressor: Single stage centrifugal
  • Turbine: Single stage

Performance

  • Thrust: 1,650 lbf (7.33 kN)
  • Power-to-weight ratio:

a26-3.jpg

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Serial #: 44-34586
Construction #: 27865
Civil Registration:
  N66368
Model(s):
  A-26B
  XB-26F
Name: None
Status: Unknown
Last info: 1972

 

History:
Lindsay Hopkins Vocational School, Miami Airport, FL, 1964-1972.
- Registered as N66368

Built as DOUGLAS XA-26F - Prototype for a high-speed version of the Invader
 
Started out as an A-26B but modified in late 1945 as XA-26F with J31 turbojet aft of bomb bay. 
During the years 1950 and 1951 flew for Shell Oil Co. on a bailment contract for the USAF doing fuel research. 
 
Donated 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.
 

j31.jpg

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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 km/h

Date of flight: 20/06/1946
Pilot: T. P. GERRITY (USA)
Crew: W.K. Rickert
Course/place: Dayton, OH (USA)

Aircraft:
Douglas XA-26F (Wright R-2800-83 and GE-1-16, 2000 hp/1600 lbs)

 

 

Sub-class : C (Aviation with engine)
Without 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
Course/place: Dayton, OH (USA)

Aircraft:
Douglas XA-26F (Wright R-2800-83 and GE-1-16, 2000 hp/1600 lbs
)

 

























































































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