The USAAF ordered 500 Merlin-powered P-82B Twin Mustangs (Model NA-123) on 8 March 1944 with production contract AC-2384, sixteen months before NAA test pilot George ‘Wheaties’ Welch took the first P-82B, 44-65160, aloft for the first time on 31 October 1945.
The end of the war forced the USAAF to re-evaluate the Twin Mustang’s future and instead of 500 P-82Bs, the Air Force issued a modified procurement order on 7 December 1945 authorizing the construction of 270 P-82Bs, including twenty already under assembly, and 230 P-82E long-range escort fighters. Further production cuts resulted in the delivery of only twenty P-82B aircraft (serial numbers 44-65160 through 65179) with the Air Force taking delivery between November 1945 and March 1946. The entire production block, except for two modified for night fighter evaluation, was assigned to the training of flight crews for the next production variant-the P-82E. The cost for the P-82B was $140,513 per unit. The B-model differed from the XP-82 only by the addition of a pressure carburettor on their Packard-Merlin engines along with the actual provision for underwing pylons for ordnance and improved machine guns (the XP-82 was equipped with Mod-2 machine guns while the P-82B received the Mod-3).
A majority of the twenty manufactured P-82Bs were used as training aircraft by the 27th Fighter Escort Group (FEG) based at Kearney Army Air Force Base (AAFB), Nebraska. Two of the -Bs were actually pulled from the production line and modified for night interception work. NACA used serial number 44-65179 in missile research while the Air Proving Ground at Eglin Field, Florida, modified and tested 44-65170 as a photographic reconnaissance version called the RF-82. Meanwhile, NAA went on to develop and produce the next Twin Mustang variant, the P-82E, and the Air Force withdrew the -B from service in December 1949.
The P-82B might have faded into oblivion and ended on the scrap heap if not for 44-65168’s (the ninth Twin Mustang off the production line) contribution to aviation history by making a non-stop flight on 27-28 February 1947. On that date, Lieutenant Colonel Robert Thacker and Lieutenant John Ard flew 44-65168, named ‘Betty Jo’ after Thacker’s wife, on a non-stop flight from Hickam Field, Hawaii, to LaGuardia Field on Long Island, New York, in fourteen hours thirty-one minutes and fifty seconds at an average speed of 347mph. They accomplished this feat without refuelling by stripping down the aircraft and adding additional internal fuel tanks and four 310-gallon drop tanks. This aircraft is now restored and displayed at the National Museum of the U.S. Air Force.
F-82E Long-Range Escort
Air Force interest with the P-82 program continued as there was no alternative long-range escort for the B-50 Superfortress, an improved version of the B-29 with a noticeably higher vertical stabilizer, and the Convair B-36 Peacemaker, then under development, since early jet fighters didn’t have the range for long-range escort missions. (The Air Force’s front-line jet interceptor, the Lockheed F-80, only had a normal range of approximately 800 miles). Early in the Twin Mustang’s development, the government made it no secret that it wanted Allison V-1710 engines to power the P-82 since it had become doubtful that the Packard-Merlin V-1650 would be available much longer. This was largely due to failed negotiations with Rolls-Royce who owned the rights and wanted Packard to pay $6,000 in royalties for every engine that the company produced. Another reason to switch to the Allison was that General Motors (GM), who owned Allison, also owned forty percent of North American Aviation and, with the end of the war, the aircraft industry went into a nose dive and the company needed to sell more Allison engines and parts to keep investors happy.
The P-82E, designated as model NA-144, became the first mass produced model of the Twin Mustang and was powered by the Allison V-1710-143 (right) and 145 (left) engines, which rotated in opposite directions. In February 1946, North American received an order for 250 Allison-powered P-82Es with a finalized contract (AC-13950) for this procurement signed on 10 October 1946. The $35 million procurement contract covered the cost for 250 P-82Es plus tools and spare parts. North American would be paid $17 million for the first 100 planes, $14.5 million for the remaining 150, and $3.5 million for special tools and ground-handling equipment. The Air Force expected the first deliveries to begin in November 1946 and, after the completion of the first 100 aircraft, NAA and the Air Force would review the contract to adjust requirements which it did by ordering the last 150 E models modified as night fighters. NAA test pilot George Welch took the P-82E on its maiden flight on 17 April 1947. The new Twin Mustang model was slightly slower with a top speed of 465mph and a lower rate of climb by almost 900 feet per minute.
Problems with the Allison engines delayed Twin Mustang production for nearly two years as production costs rose to more than $50 million. The government negotiated with Allison in August 1945 to supply North American with an updated V-1710, since earlier versions of the powerplant had equipped the P-38 and P-40, among other famed aircraft from the Second World War. Allison agreed to purchase government parts to develop the new engine, which proved to be costly with a final price tag of $18.5 million. As previously stated the first flight of the P-82E took place on 17 April 1947; however, engine malfunctions appeared during the flight and continued with the next four aircraft accepted by the Air Force (one each in September and November 1947 and two in December). The updated Allison V-1710 suffered from spark plug fouling, oil leaks, engine backfiring at high and low power settings, auxiliary super-charger failure, and engine power surge. Fouling of the spark plugs caused by oil accumulation was the most serious problem requiring new spark plugs after nearly every single flight.
Because the new engine was not as reliable as the Merlin (it was nicknamed ‘The Allison time-bomb’), problems persisted with the engines that required extensive testing through June 1948 using the first four -82E Twin Mustangs. North American had to accept the first 200 Allison engines, which could only operate at lower power settings, to avoid further F-82 production delays. Meanwhile, as the aircraft company waited for acceptable engines, the cost to North American continued to climb as it had to store uncompleted Twin Mustang airframes in a warehouse owned by the Consolidated-Vultee Aircraft Corporation (Convair) at Downey, California. Assembly lines were set up at Downey to install engines as they arrived and deliver the completed F-82Es rather than truck them back to North American’s facility at Inglewood. NAA engineers were able to fix some of the problems by using Merlin components but the engine, along with a shortage of spare parts, continued to be a problem for the F-82 throughout the aircraft’s operational life. The F-82Es were externally indistinguishable from the F-82Bs except for a reconfigured nose for the Allison engine with twelve exhaust stacks on each side of the cowling instead of the six that characterized the Packard Merlin.
The P-82E became the F-82E, after the newly established U.S. Air Force changed the pursuit ‘P’ indicator to ‘F’ for fighter in 1948. The Air Force accepted 100 F-82Es with serial numbers 46-255 to 46-354, the serial numbers being reduced from 7 digits for the -B series to 5 digits for the E-H series. Actual tail numbering, except for the -B model, consisted of the last number of the relevant fiscal year followed by the three-digit production serial number. Most went to the 27th Fighter Escort Group (FEG) which was comprised of the 522nd, 523rd, and 524th Fighter Interceptor Squadrons (FIS) and were assigned to the newly established Strategic Air Command (SAC) as long-range escorts for B-29, B-50, and B-36 bombers. The F-82E often flew long-range demonstration flights as a propaganda weapon against the Soviets to show the Air Force’s ability to protect its strategic bomber force. By the end of fiscal year 1948, North American had delivered seventy-two E-Model Twin Mustangs with a further twenty-four in fiscal year 1949 at a cost of $215,154 per unit (this was the same cost as applied to the F through H series). The 27th FEG conducted over-water Very Long Range (VLR) training missions beginning in January 1949 which encompassed a five-leg flight starting from Kearney Air Force Base (AFB), Nebraska, to MacDill AFB, Florida, then to Ramey AFB, Puerto Rico, to Howard AFB Panama, then to Jamaica, and then back to Kearney – a trip that took a few days to complete. One VLR mission starting from Bergstrom AFB in Austin, Texas, to Ramey AFB – a distance of some 2,300 miles – was accomplished without refuelling.
The Air Force regarded the F-82E as a short-term interim fighter, and with the promise of jets with longer range plus the arrival of mid-air refuelling with Boeing KC-29 and KC-97 aerial tankers, the Air Force had begun phasing out the F-82E by March 1950, less than a year after the final unit rolled off the assembly line. The 27th FEG started transitioning to the F-84E Thunderjet in the spring of 1950 and by September 1950, the Group’s last F-82Es were flown to Warner-Robbins AFB, Georgia. The Air Force made the decision to scrap all of the Twin Mustang escorts, retaining the engines and other usable parts for the remaining F-82F/G/H night and all-weather fighters stationed in Alaska and the Korean War zone.
Night and All-Weather Fighter
The Air Force’s first aircraft specifically designed as a night fighter was the twin-engine P-61 Black Widow equipped with the SCR-720 airborne radar. Two prototypes were ordered in January 1941 but, due to technical issues, a prototype did not take to the air until May 1942. Labour and material shortages delayed delivery of the first production P-61A until October 1943 followed by the P-61B in July 1944 and a C-variant in July 1945. The twin-boom Black Widow, armed with 20mm cannons and .50-caliber machine guns, proved far superior to the P-70 – a stop-gap night-fighter adaptation of the Douglas A-20 Havoc/Boston light bomber. Powered by two 2,000-hp Pratt & Whitney engines with two-speed General Electric superchargers, the P-61 had a top speed of 367mph with a rate of climb of 1,775 feet-per-minute. Unfortunately it proved to be a poor interceptor against Japanese bombers above 20,000 feet and the Black Widow’s radar operated satisfactory only eighty-one percent of the time, making that system responsible for more abortive missions than any other malfunction. The SCR-720 had a forward search azimuth of 180-degrees with a maximum search range of five to seven miles. However, the Black Widow was the best the Air Force could hope for during that period and it would rely on the P-61 after the war until 1948 when the F-82F and G Twin Mustangs, specially equipped for night fighting duties, became operational.
In November 1945, the Air Force requested an evaluation of the P-82B to see whether it could be adapted to replace the P-61 night fighter. Consequently, North American pulled the tenth and eleventh of the twenty production P-82Bs for conversion into night fighters as the P-82C (serial number 44-65169) and P-82D (serial number 44-65170) in late 1946. The P-82C’s maiden flight occurred on 27 March 1947 and the P-82D followed two days later. Both experimental night fighters featured a large radar pod, nicknamed the ‘pickle’ or ‘dong,’ under the centre wing section with the C-model housing the SCR-720 radar while the P-82D used the AN/APS-4 radar. The large nacelle, adopted for the production models F-82F, G, and H, and somewhat resembling a drop tank, protruded forward past the propellers to eliminate interference. A radar operator’s position, with related equipment, replaced the co-pilot’s instrumentation and controls in the right-hand cockpit.
One hundred examples of the D variant were produced as the P-82F (model NA-149 with serial numbers 46-405 to 46-504) equipped with the AN/APG-28 – an improved version of the APS-4 radar – with an additional forty-five of the C variant as the P-82G (model NA-150 with serial numbers 46-355 to 46-383 and 46-389 to 46-404 equipped with the SCR 720). The additional weight of the radar pod created very few performance problems with the F-82F having a top speed of 460mph. The G’s SCR-720 radar weighed slightly less than the APG-28 and thus the aircraft’s performance was slightly better. Before NAA delivered either the F or the G, the Air Force requested an additional requirement for modifying a small number of the night variants into all-weather fighters for service in Alaska; nine F-82Fs (serial numbers 46-496 through 46-504) and five additional F-82Gs (serial numbers 46-384 through 46-388). The F-82H was the last Twin Mustang variant produced and was specially equipped with thermal anti-icing gear and de-icer boots on the propeller blades. The thermal de-icing equipment sent hot air from behind the after-cooler radiator and blew it across the wing leading edges and tail surfaces. Other modifications included an improved cockpit heating system, updated radio equipment, plus the SCR-720 radar with which the F-82G was already equipped.
The F, G, and H Twin Mustang was not a pilot’s ideal night fighter due to the cockpit’s limited field of view, and poor landing characteristics especially at night. Moreover, during nocturnal operations, the pilot and radar operator found it difficult to maintain night vision due to engine exhaust flame, instrument glare and the bright flashes from the aircraft’s machine guns. The Air Force accepted the last F-82G and six F-82H Twin Mustangs in March 1949.
By mid-1950, the Twin Mustang had become a second-line aircraft as squadrons began replacing them with the jet-powered F-89 and F-94. From an operational standpoint, some pilots felt a psychological discomfort of impending doom of a midair collision when they caught sight of the co-pilot/radar operator’s fuselage out of the corner of their eyes. Another problem was with the J-8 Altitude Gyro used during instrument flying. Pilots either loved it or hated it because it read exactly opposite to the presentation of conventional gyroscopic instruments. When the miniature aircraft on the gyro appeared ‘below’ the reference line, instead of descending the F-82 was actually climbing and so, during an instrument landing approach, the pilot had to remain cognizant of what the aircraft was actually doing.
The F-82F first flew on 11 March 1948 and entered service in September with the Air Defense Command to replace the P-61 Black Widow, while the F-82G had become operational by the end of 1948 with the Caribbean Air Command: the Fifth, and Twentieth Air Force for the Far East Air Forces (FEAF). The Air Force established two all-weather fighter groups – the 52nd Fighter (All-Weather) Group (F(AW)G) and 325th F(AW)G – with the first F-82Fs going to the 52nd F(AW)G. These F-82 night fighter air groups provided air defence of the CONUS (Continental United States) from early 1948 to mid-1952 when conversion to the Lockheed F-94A/B was completed. The first F-82H flew on 15 February 1949 and all fourteen went to the 449th Fighter (All-Weather) Squadron (F(AW)S) based at Ladd AFB, with detachments operating from Galena, Davis, and Mark Fields, Alaska. The last F-82H remained on the USAF inventory until June 1953. The 449th flew periodic armed-reconnaissance missions over the coastline of western Russia (Chukchi Peninsula), between May 1949 and July 1950, along with challenging Soviet reconnaissance aircraft that neared Alaskan airspace. An unusual series of missions flown by the 449th during May 1949 was bombing ice jams in Alaskan rivers to prevent flooding.
Problems with the lacklustre performance of the Allison V-1710 engine caused nearly a two-year delay in the production and delivery of the F-82E, and by that time the Air Force had reduced the procurement order to 250 E through H variants. The F-82 was the last piston-engined fighter accepted by the Air Force in large numbers; it was an interim fighter, a stop-gap measure needed to fill a void until the arrival of modern jet fighters with greater range and night fighting capabilities. The Twin Mustang would have faded into oblivion except for the record-breaking flight of the F-82B ‘Betty Jo,’ delays in the production of the Northrop F-89 and Lockheed F-94 all-weather jets, and the unforeseen Korean War. F-82-equipped USAF squadrons saw intense service in the Korean War flying escort, weather reconnaissance, night combat air patrol (NCAP), and interdiction missions between June 1950 and February 1952 before being phased out and replaced by the F-94B. The principal variant of the Twin Mustang to operate in Korea was the F-82G night fighter which, in the new age of jet interceptors, scored the recently established Air Force’s first aerial kills only two days after the war began. Ultimately, the lack of spare parts, maintenance issues, and the arrival of jet all-weather fighters ended the F-82’s combat duty over Korea.