Although Gloucestershire Transport History focuses on Gloucestershire and its rich transport heritage it has never been parochial or afraid to explore relevant national or international topics, even one that is literally blowing in the wind. As such I was very proud to receive an email from Sean Edwards of Florida, USA asking for the help of Gloucestershire Transport History readers in discovering the history of two large wooden wind tunnel models of a Consolidated XB-32 Dominator four engined bomber and the slightly more familiar shape of a twin boom twin engined Northrop XP-61 night fighter.
If anyone with knowledge of either of these American piston engined aircraft or indeed of wind tunnel models, their value and collectability would like to contribute to a future article then please email me.
Meanwhile, this is what I have been able to find out:
The Consolidated XB-32 Dominator (Consolidated Model 33/34) grew from the fears of General Henry H. “Hap” Arnold, head of the US Army Air Force, that America at the end of the 1930s could face threats from both Nazi Germany and an expansionist Japan.
These fears were given further strength in 1939 by the report of a committee headed by USAAF Brigadier General W. G. Kilner and including transatlantic pioneer Charles Lindbergh who had recently toured Luftwaffe bases and was convinced that German military aviation was well ahead of the rest of Europe.
The Kilner Committee’s recommendations for the development of new long-range heavy bombers were further advanced on 2 December 1939 when General Arnold requested design studies for a 5 000 mile range bomber from manufacturers Boeing, Lockheed, Douglas and Consolidated.
Of the design studies submitted, Boeing’s B-29 was most favoured by the USAAF followed by the Lockheed XB-30, Douglas XB-31 and Consolidated XB-32 although when both Lockheed and Douglas withdrew from the competition a few months later both Boeing and Consolidated prototypes were ordered in September 1940.
The USAAF intended developing the Consolidated B-32 concept as a fall-back option should the more promising B-29 run into difficulties, much as in the 1950s the RAF would have theSupermarine Swift as an insurance policy against the Hawker Hunter jet fighter.
The design of the B-32 was entirely new but based on the layout of Consolidated’s very successful B-24 Liberator. However, the B-32 had larger wings in proportion to its body, a cylindrical fuselage, and – originally – a rounded B-29-type nose. However, this was replaced with the stepped nose more like that of a Douglas DC-3 before production began.
Like the B-29, the B-32 had pressurised crew compartments and remotely operated gun turrets while the gun turrets in the B-32 were retractable.
The twin tail of the B-24 was initially used on all three XB-32s although neither this nor a replacement B-29 single fin fitted to the third prototype provided sufficient stability. For this reason the 118 production B-32s eventually built all had an even taller single tail.
The USAAF had planned to replace all its B-24 Liberators and B-17 Flying Fortresses by B-32 Dominators from mid 1944, starting with bomb groups in the Mediterranean and followed by the 15th and 8th Air Forces. However, although the first prototype XB-32 had flown before the first B-29 it had been plagued with technical problems and fell behind development of its Boeing rival.
Indeed, a combat evaluation of eleven missions for three B-32s with the 386th Bomb Squadron of the 312th Bomb Group was only agreed because no more Boeing B-29s could be spared for the Pacific based 5th Air Force.
The first of these was flown on 29 May 1945 against a supply depot at Antatlet in the Philippines and the last on 25 June against bridges at Kiirun on the island of Formosa. Due to the success of these raids, the 386th Bomb Squadron converted entirely to B-32s and Dominators were to replace all B-24 Liberators in the Pacific.
In fact the 386th Bomb Squadron were to fly six more combat missions before the war ended and then two photographic reconnaissance missions over Japan on the eight and ninth days after the second atomic bomb was dropped on Nagasaki on 9 August 1945. Despite Japan being so close to surrender, both missions were attacked by flak and fighters and although two B-32s were damaged and Sergeant Marchione, a photographer on the second photographic reconnaissance mission, was killed no Dominators were lost due to enemy action.
After one final photographic reconnaissance mission on 28 August – the same day that American forces began their occupation of Japan – the 386th Bomb Squadron ceased operations on 30 August 1945. On 8 September the B-32 was cancelled as surplus to requirement and all production halted by 12 October. Partly built B-32s were scrapped at the Consolidated factory while completed machines were flown to scrapyards. The last B-32 was cut up in the summer of 1949, two years after the first flight of the Boeing B-47, the first of the new swept wing nuclear armed jet bombers.
As has been described in other pages on this website, fighter aircraft were used to destroy Zeppelins and other marauding enemies in the skies above England during the First World War although these were essentially day fighters flown by pilots with good night vision.
In the locust years between the two global conflicts of the Twentieth Century too, night fighters were also neglected until British air superiority during the Battle of Britain forced the Luftwaffe to bomb London, Coventry and other cities by night with radio direction finding equipment.
Although German radio beams could be detected and disrupted, the RAF’s Supermarine Spitfire was not a practical night fighter as its narrow track undercarriage made landings in darkness dangerous. The Hawker Hurricane, although more robust and easier to handle on the ground, lacked speed and the Boulton Paul Defiant turret fighter lacked forward firing armament.
However, just as Chain Home ground radar stations had helped RAF Fighter Command detect incoming German aircraft during the Battle of Britain, so the RAF began to receive airborne interception radar sets which, due to their size and weight, had to be carried in larger twin engined aircraft such as the Bristol Blenheim and Beaufighter. As shorter wavelength radar was a more precise tool in locating nocturnal bombers, a major British development in airborne interception was the cavity magnetron – which also became the ancestor of the microwave oven.
Both the Battle of Britain and the ensuing night Blitz by the Luftwaffe were witnessed by observers from the US Army Air Force and as a result an American requirement was identified in October 1940 for a dedicated night-fighter platform possessing both firepower and speed to contend with enemy forces likely to attack the United States.
Northrop’s proposal submitted in December 1940 – for the first dedicated American night fighter followed the format of the existing twin engined twin-boom Lockheed P-38 Lightningwith a wide horizontal tail stabiliser but large enough to carry a crew of three with multiple gun positions in the fuselage. In fact it would be the largest fighter ever ordered by the USAAF.
The first XP-61 prototype – powered by Pratt & Whitney R-2800-A5G radial piston engines – flew in May 1942 with Vance Breese at the controls while the second prototype flew that November and had Radiation Laboratory SCR-270 radar installed in April 1943.
The radar system was maintained in the extreme forward portion of the nose cone assembly allowing for easy access by ground personnel. The stepped “glasshouse” cockpit housed the pilot and the gunner to his rear. The gunner was afforded a good view over the pilot although the radar operator was situated in a aft cockpit to the extreme rear of the gondola, completely separated from the other two men.
The undercarriage consisted of two large single wheeled main landing gears under each engine nacelle and a single-wheeled nose landing system – all were fully retractable with the nose wheel recessing rearwards into the cockpit floor and the main gears recessing backwards into their under-nacelle positions. Wings were straight and shoulder-mounted with slight dihedral outboard of each engine and a relatively straight leading edge with a forward swept trailing edge. The engines powered four-bladed propeller systems and were fitted to either side of the fuselage gondola.
The dorsal turret (when installed) was a product of the General Electric Company, fitted with a gyroscopic fire control computer, and could be fired by both the gunner and the radar operator as both had access to the same aiming controls and sighting instrumentation.
Additionally, the turret could be locked forward to be fired along with the 20mm cannon armament by the pilot. Traverse was 360-degree rotation with up to 90-degree elevation. The turret contained a battery of four .50 calibre Browning M2 air-cooled heavy machine guns (the centre guns slightly offset higher than the outer two guns) along with about 560 rounds of 12.7mm ammunition per gun.
The four Hispano M2 20mm cannons were also fitted to the ventral fuselage, fixed to fire forward and operating with 200 cannon rounds to a gun.
The P-61, later known as the Black Widow, was the largest contract that Northrop had ever undertaken and refining the aircraft for service took a long time with turrets, fuel tanks and control surfaces all having to be redesigned on the way.
It was soon discovered (via wind tunnel tests and, later, with a P-61 airframe test gondola) that the dorsal turret was the cause of an air flow disturbance along the aft portion of the central gondola, occurring just aft of the turret assembly itself. This find forced the removal of the turret from the 38th P-61A production example and onwards. The stability issue developed when the turret was traversed to either side or elevated away from its “at rest” face-forward position causing a disruption to the air flow causing buffeting over the aircraft when at speed
Indeed, arguments between the US Army and the Massachusetts Institute of Technology over camouflage meant that the first jet black Black Widow did not appear until February 1944.
At the same time, Northrop was already committed to building 400 Vultee Vengeance dive bombers for the RAF.
Service deliveries started in May, 1944, when the 348th Night Fighter Squadron (NFS) of the 481st Night Fighter Group (NFG) received their Black Widows. While the P-61 was exceptionally agile for such a large plane (thanks to the large and well-designed flaps), it remained troublesome and was constantly being compared to both the de Havilland Mosquito and the Bristol Blenheim as the best available night fighter. However, the P-61 did represent an advance on the Douglas Havoc.
Deliveries from Northrop rose to three a day by June 1944 and the first P-61 kill was recorded on 30 June 1944 (some sources say 6 July) when a Black Widow of the 6th NFS downed a lightly armoured Japanese ‘Betty” bomber over the Pacific.
The P-61A was built in four major sub-variants. The P-61A-1 became the initial production models fitting the R-2800-10 series engines of 2,000 horsepower. Forty-five of these aircraft were produced in whole though the last seven in the run were delivered without the dorsal turret.
Thirty five P-61A-5 were also produced without the dorsal turret but fitted instead with the R-2800-65 series engines of 2,250 horsepower. Northrop engineers were always trying to get more “punch” out of her engines.
One hundred P-61A-10 were built featuring water injection for an increased boost to engine output and twenty P-61A-11 were given underwing hardpoints (one to a wing, inboard of the engines) for fuel tanks or two 1 600 lb bombs.
The addition of fuel tanks drastically increased the range of the base model Widow, allowing it to operate in the vastness of the Pacific. Comparatively, the addition of bombing capabilities allowed for night-time intruder ground attacks to be added to the Widow’s role.
Although conventional piston engined bombers and fighters were far less of a threat to Britain in 1944 than they had been in 1940, the P-61 Black Widow proved a useful interceptor of V-1 flying bombs ( with nine confirmed kills) and also also as a ground attack platform, firing its two ventrally mounted 20mm canon against road and railway traffic: most notably during the Battle of The Bulge in December 1944. No P-61s were lost over Europe but three crews did achieve “ace” status.
540 examples of the P-61B model followed from July of 1944 and reintroduced a structurally reinforced dorsal turret albeit with just 2 machine guns at first and later with the full 4 machine gun compliment on the P-61B-15. The nose was stretched a full eight inches to provide for a greater capacity while a SCR-695 tail warning radar was installed.
The rear gunner’s glass cone, prone to collapse or breaking off completely during high speed flight, was strengthened and four underwing hardpoints could eventually handle fuel tanks, bombs or HVAR 5-inch ground attack rockets.
More specifically thirty eight P-61B-2 examples were produced with the same underwing hardpoints as that of the A-11 models while the forty six P-61B-10s featured four hardpoints. The P-61B-11 brought back the dorsal turret with two .50 calibre machine guns but only five were built while the 153 P-61B-15 Black Widows featured four .50 calibre machine guns in the same position.
The six P-61B-16 reverted to just two machine guns in the dorsal turret while the 84 P-61B-20 featured a new General Electric four gun turret. Produced in another batch of six were the P-61B-25 featured an automatically-aimed and fired turret supported by an APG-1 gun-laying radar and integrated computer system while at least a dozen P-61B models served with the United States Marine Corps under the designation of F2T-1N (serial numbers 52750 through 52761).
In 1945 the P-61C became the final production version with improved and turbocharged systems supplied by General Electric (designated as CH-5) fitted beneath each 2 800 bhp Pratt & Whitney R-2800-73 radial piston engine nacelle.
New and larger propeller systems from Curtiss were installed to each engine for improved high-altitude performance and top speed was increased to 430 miles per hour at 30 000′ though some longitudinal instability occurred when the aircraft officially exceeded 35 000lbs, adding to the need for at least a three mile runway. New airbrakes were also added over and above the wings while other impressive statistics were 307 mph cruise speed, service ceiling of 41 000 feet, 2 600 feet per minute climb and 1 725 miles range.
Had the war against Japan not formally ended in September 1945 Northrop would have also produced an even more impressive P-61D while 20 November 1944 marked the first flight of a prototype P-61E escort fighter. Intended to assist Boeing B-29 Superfortresses in bombing the Japanese mainland, these Widows were built without the dorsal turret and for a crew of two in a tandem seating arrangement under a large blown canopy glass. Other features included additional fuel tanks and a nose-mounted battery of four .50 calibre machine guns while the original four 20mm cannons in the ventral position were retained. The rear radar operator’s position was taken up by the extra fuel tanks to improve range.
Although the P-61E escort fighter never went into production, the F-15A “Reporter” was developed from the first abandoned XP-61E prototype and became a dedicated photo-reconnaissance platform. Once again, the pilot and camera operator sat in tandem under a single-piece bubble-type canopy and the forward fuselage featured six cameras. The 2 800 bhp Pratt & Whitney R-2800-73 piston engines were the same radials fitted to the P-61C and 36 production examples were designated RF-61C by the United States Air Force, founded in 1947, which used “F” for Fighter rather than “P” for Pursuit in its nomenclature.
The XP-61E had reported performance specifications of 376 miles per hour top speed; a service ceiling of 30 000 feet, a rate-of-climb of 2 500 feet per minute and a range of 2 250 miles. Power was supplied from two 2 000 bhp Pratt & Whitney R-2800-65 engines.
Reporter specifications included a top speed of 440 miles per hour, cruising speed of 315 miles per hour, a service ceiling of 41 000 feet and a range of 4 000 miles.
Although based in Japan after 1945, P-61s were replaced by F-82 Twin Mustangs in May 1950 just months before the outbreak of the Korean War and finally left the USAAF inventory in 1952.