The North American F-82 Twin Mustang was a long-range twin-fuselage escort fighter, designed and produced by the American aircraft manufacturer North American Aviation. It shared limited commonality with the preceding North American P-51 Mustang.
The F-82 was designed during World War II as an escort for the Boeing B-29 Superfortress strategic bombers flying long range missions against Imperial Japan; however, the conflict ended before development could be completed. Despite the name, there was little in common between the Twin Mustang and the more conventional North American P-51 Mustang, the former being a clean sheet design that shared a minority of components with the latter. The XP-82 prototype performed its maiden flight on 15 June 1945, and the type was introduced to United States Army Air Force (USAAF) service one year later. While the end of WW2 had slowed production, the emergence of the Cold War gave renewed importance to the project as the Twin Mustang was procured as an interim solution to the fighter escort mission for the USAAF's strategic bomber force; it was also suitable for use as an all-weather air defense interceptor. On 27 February 1947, a P-82B flown by Colonel Robert E. Thacker made the longest non-stop flight ever conducted by a piston-engined aircraft, flying nonstop from Hawaii to New York without refueling and covering a distance of in 14 hours and 32 minutes.
Upon the creation of the United States Air Force (USAF) in 1948, the new service inherited the P-82 fleet (redesignating it F-82) and placed it under the Strategic Air Command (SAC), which used the type as a long-range escort fighter. Furthermore, radar-equipped F-82s were flown extensively by the Air Defense Command (ADC) as replacement all-weather day/night interceptors for the wartime Northrop P-61 Black Widow. During the Korean War, Japanese-based F-82s were among the first USAF aircraft to operate over Korea; the first three North Korean aircraft destroyed by U.S. forces were shot down by F-82s, the first being a North Korean Yak-11 downed over Gimpo Airfield by the USAF 68th Fighter Squadron. However, the appearance of the jet-powered Mikoyan-Gurevich MiG-15 over North Korea in late 1950 quickly demonstrated its ability to outmatch many USAF combat aircraft; accordingly, the type was removed from ADC service during the early 1950s, having been superseded by the Lockheed F-94 Starfire jet fighter. Following the introduction of the jet-powered Boeing B-52 Stratofortress strategic bomber, the escort fighter role was considered to have become obsolete and SAC stood down its last strategic fighter escort wings in 1957.
Design and development Development of the F-82 Twin Mustang can be traced back to 1942 and the issuing of an Advanced Development Objective that sought the development of new escort fighters. To effectively fight World War II, Allied military planners recognised that they needed to undermine the Axis powers by heavily damaging their industrial economies across both Europe and Japan prior to conducting conclusive operations such as the planned U.S. invasion of the Japanese home islands. While the United States Army Air Force's (USAAF) were in the set to introduce the Boeing B-29 Superfortress, a new bomber capable of flying missions exceeding , such as from either the Solomon Islands to Tokyo, this was beyond the range of the Lockheed P-38 Lightning and the conventional North American P-51 Mustang. Accordingly, there was a recognised need for a very long-range (VLR) escort fighter that would be able to guard the B-29 throughout its lengthy flight to Japan, rather than leaving them unprotected against interception by enemy fighters. Accordingly, a design team at North American, led by Aviation Assistant Chief Designer Edgar Schmued, started work on designing a suitable long-range escort aircraft in late 1943.
Early work centred around two different proposals, one being a more conventional twin-engine single-seat fighter while the second proposition was more unconventional, comprising a pair of fuselages that each housed a pilot and were attached to one another via a central wing. The latter was favoured and became the Twin Mustang. In spite of this name implying that the aircraft was derived from the P-51 Mustang, or that it was formed from two Mustangs having been fixed together, it was actually a largely clean-sheet design; the name was instead intended to be a reference to the increased range and payload capacity of the aircraft. Only 20 percent of the Twin Mustang’s components were interchangeable with the Mustang. In February 1944, North American presented their design proposal, which immediately received the support of multiple USAAF officials; that same month, the company received an instruction to build three XP-82 prototypes along with an initial production order for 500 aircraft.
In terms of its design configuration, the Twin Mustang comprised a pair of fuselages that were joined together via a center wing section. The landing gear was of conventional type; the main wheels retracted into the fuselage center sections. The aircraft was provisioned with various armaments, including a total of six .50 caliber (12.7mm) M3 Browning machine guns were mounted on the centre wing section. The prototype XP-82 carried an eight-gun pod beneath the aircraft's centre wing; this position could be used to accommodate bombs, radar, an external fuel tank, or weather observation apparatus. An alternative gun pod that was fitted with a cannon was also proposed.Carey 2014, p. 20. The outer wings were fitted with four hardpoints, which were rated to carry up to of ordnance each.
While possessing substantial range, the resulting aircraft was not particularly agile and thus considered to be ill-suited to dogfighting. The flight controls used on the models were particularly heavy and were unboosted, although later production aircraft did feature hydraulically-boosted controls (provisioned from three separate hydraulic systems) for the aileron, elevator, and rudder. It could maintain level flight on a single engine provided effective use of the rudder and the propeller of the idle engine was feathered.
The XP-82 prototypes, as well as production P-82Bs and P-82Es, retained both fully-equipped cockpits that permitted pilots to fly the aircraft from either position, alternating control during long flights and thereby enabling the aircraft to be safely continuously flown to the full extent of its lengthy endurance. However, the later night fighter versions of the aircraft opted to retain the cockpit on the left side only, having placed the radar operator in the right position. An internal heater was present, although this was typically operated only for anti-icing purposes during flight.
The maiden flight of the first prototype took place on 26 June 1945; two months later, the USAAF accepted delivery of this prototype, as well as two more prototypes by October of that year. However, by the time that the second prototype had been completed, the USAAF's need for long escort fighters had been resolved via the capture of several islands sufficiently close to the Japanese mainland. Accordingly, in December 1945, it was decided to scale back the production numbers from 500 aircraft to 270 aircraft. While several P-82B airframes were completed before the end of WW2, most of these remained at the North American factory in California waiting for engines until 1946. As a result, none saw service during the conflict; delivery of the first P-82Bs occurred during January 1946.
Like most versions of the P-51 Mustang, the first two prototype XP-82s as well as the next 20 P-82B models were powered by British-designed Rolls-Royce V-1650 Merlin engines, re-engineered for increased durability and mass-production, and built under license by Packard. These engines provided the fighter with excellent range and performance; however, officials within the USAAF sought to power the Twin Mustang using an indigenous and stronger engine than the foreign-designed P-51's V-1650. In addition, the licensing fees paid to Rolls-Royce for each V-1650 were being increased by Britain after the war. To this end, the service negotiated in August 1945 with the Allison Division of the General Motors Corporation for a new version of the Allison V-1710-100 engine. This measure compelled North American to switch subsequent production P-82C and later models to the lower-powered engines. It was found that Allison-powered P-82 models demonstrated a lower top speed and poorer high-altitude performance than the earlier Merlin-powered versions. The earlier P-82B models were designated as trainers, while the "C" and later models were employed as fighters, making the P-82 one of the few aircraft in U.S. military history to be faster in its trainer version than the fighter version.
While work had slowed on the P-82's development following the end of WW2, circumstances had changed by 1947. Increasing tensions between the rising superpowers of the era, the United States and the Soviet Union, which would cumulate in the lengthy Cold War, led to an increased prioritisation of numerous military programmes on both sides. While separate efforted proceeded towards developing a new generation of jet aircraft, full-rate production of the P-82 was authorised as a replacement for the wartime Northrop P-61 Black Widow as an all-weather night fighter to defend the American mainland against a potential attack by nuclear-armed Soviet bombers.
In 1948, the 3200th Proof Test Group at Eglin AFB, Florida, fitted the 4th F-82B Twin Mustang with retractable pylons under the outer wings capable of mounting ten High-Velocity Air Rockets (HVAR) each, which folded into the wing undersurface when not in use. This installation was not adopted on later models, the standard "tree" being used instead. The thirteenth aircraft was experimentally fitted with a center wing mounted pod housing an array of recon cameras, and was assigned to the 3200th Photo Test Squadron, being designated, unofficially, the RF-82B.
Record-setting
On 27 February 1947, P-82B, named Betty Jo and flown by Colonel Robert E. Thacker, made history when it flew non-stop from Hawaii to New York without refueling, a distance of in 14 hours and 32 minutes, during which the aircraft averaged . During this flight, it carried a full internal fuel tank of , augmented by four tanks for a total of . Colonel Thacker did not drop three external tanks when their fuel was expended, either because of an oversight, or because they were stuck due to a mechanical glitch. This remains the longest nonstop flight ever made by a propeller-driven fighter, and the fastest time in which such a distance has ever been covered in a piston-engine aircraft. The aircraft chosen was an earlier "B" model powered by Rolls-Royce Merlin engines (see "Surviving aircraft" below).
Operational history The Twin Mustang was developed at the end of the prop-driven fighter era and at the dawn of the jet age. Its designed role as a long-range fighter escort was eliminated by the end of World War II. With the rapid draw-down of the armed forces after the conflict, the newly established USAF had little money for new propeller-driven aircraft, especially since jet aircraft, such as the Messerschmitt Me 262, had proved to be faster than the P-51 Mustang over the skies of Germany in late 1944. The completed airframes (minus engines) of the P-82 pre-production aircraft already manufactured went into storage, with an uncertain future.