P-82 Twin Mustang

Extending the escort range

Long range escort missions led to a problem that was no issue in earlier fighters: pilot fatigue. Sitting in a tight cockpit for up to 8 hours is one thing, managing fuel from takeoff untill landing, flying formation and the constant stress of air combat all (often in poor European weather conditions) combined was enough to drain pilots completely. On more than one occasion, pilots had to be helped out of their cockpit when they returned to base.

Further more, the USAAF was looking for fighters with even more range than the P-51 to operate in the extreme long escort missions, escorting B-29s on missions exceeding 2,000 miles over the Pacific (from the Solomons or Philippines to Tokyo).

NAA's Edgar Schmued came up with the idea to link two Mustangs together with a common center wing and horizontal stabilizer in November of 1943. In January of 1944, US General Herny H. “Hap” Arnold was shown the concept and became enthousiastic with the idea. As a result, NAA was given the go-ahead to proceed with the design. 

The North American P-82 Twin Mustang (NA-120) was born. As it turned out, the Marines captured islands close enough to Japan that P-51s were easily able to escort the B-29s all the way to Japan and back. As a result, P-82s never saw combat during WWII.

Design and Development

Initially intended as a very long-range (VLR) escort fighter, the F-82 was designed to escort Boeing B-29 Superfortress bombers on missions exceeding 2,000 mi (3,219 km) from the Solomons or Philippines to Tokyo, missions beyond the range of the Lockheed P-38 Lightning and conventional P-51 Mustangs. Such missions were part of the planned U.S. invasion of the Japanese home islands, which was forestalled by the surrender of Japan days after the atomic bombings of Hiroshima and Nagasaki.

The second prototype North American XP-82 Twin Mustang (44-83887) being flight-tested at Muroc Army Airfield, California.

In October 1943, the North American Aircraft design team began work on a fighter design that could travel over 2,000 mi (3,219 km) without refueling. It consisted of a two-fuselage design, somewhat similar to the experimental German Messerschmitt Bf 109Z "Zwilling". Although based on the lightweight experimental XP-51F, which would later become the P-51H Mustang, it was actually an entirely new design. North American Design Chief Edgar Schmued incorporated two P-51H Mustang fuselages lengthened by the addition of a 57 in (145 cm) fuselage plug located behind the cockpit where additional fuel tanks and equipment could be installed. These were mounted to a newly designed center wing section containing the same six .50 in (12.7 mm) M2 Browning machine guns as a single-engine Mustang, but with more concentrated fire. The outer wings were strengthened to allow the addition of hard points for carrying additional fuel or 1,000 lb (454 kg) of ordnance. The two vertical tails were also from the XP-51F, but incorporated large dorsal fillets for added stability in case of an engine failure. The aircraft had a standard landing gear with both wheels retracting into bays under each fuselage center section.

The XP-82 was to be powered by two Packard-built Rolls-Royce V-1650 Merlin engines. Initially, the left engine was a V-1650-23 with a gear reduction box to allow the left propeller to turn opposite to the right propeller, which was driven by the more conventional V-1650-25. In this arrangement both propellers would turn upward as they approached the center wing, which in theory would have allowed better single-engine control. This proved not to be the case when the aircraft refused to become airborne during its first flight attempt. After a month of work North American engineers finally discovered that rotating the propellers to meet in the center on their upward turn created sufficient drag to cancel out all lift from the center wing section, one quarter of the aircraft's total wing surface area. The engines and propellers were then exchanged, with their rotation meeting on the downward turn, and the problem was fully solved. The first XP-82 prototype (44-83886) was completed on 25 May 1945, and made the type's first successful flight on 26 June 1945. This aircraft was accepted by the Army Air Forces on 30 August 1945. AAF officials were so impressed by the aircraft while still in development that they ordered the first production P-82Bs in March 1945, fully three months before the aircraft's first flight.

Prototype XP-82s, P-82Bs and P-82Es retained both fully equipped cockpits so that pilots could fly the aircraft from either position, alternating control on long flights, while later night fighter versions kept the cockpit on the left side only, placing the radar operator in the right position.

Twin Mustangs in production at North American, 1948.

Although some P-82B airframes were completed before the end of World War II, most remained at the North American factory in California waiting for engines until 1946. As a result, none saw service during the war.

Like 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 Merlin engines, built under license by Packard. These provided the fighter with excellent range and performance; however, the Army had always wanted to give the Twin Mustang a purely American and stronger engine than the foreign-designed P-51's V-1650 (built at Packard plants, dismantled after the war). In addition, the licensing costs paid to Rolls-Royce for each V-1650 were being increased by Britain after the war. It therefore 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 forced 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.

Record-setting

On 27 February 1947, a P-82B 44-65168 named Betty Jo and flown by Colonel Robert E. Thacker made history when it flew nonstop from Hawaii to New York without refueling, a distance of 5,051 mi (8,129 km) in 14 hr 32 min (347.5 mph/559.2 km/h). This flight tested the P-82's range. The aircraft carried a full internal fuel tank of 576 gal (2,180 l), augmented by four 310 gal (1,173 l) tanks for a total of 1,816 gal (6,874 l). Also, Colonel Thacker forgot to drop three of his external tanks when their fuel was expended, landing with them in New York.

To this day, it remains the longest nonstop flight ever made by a propeller-driven fighter, and the fastest such a distance has ever been covered in a piston-engined aircraft (the record for the longest unrefueled flight by a propeller-driven aircraft of any type is held by the Rutan Voyager). The aircraft chosen was an earlier "B" model powered by Rolls-Royce Merlin engines (see "Survivors" 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 atomic bombing of Japan and the sudden end of World War II. With the rapid draw-down of the armed forces after the war, the newly established United States Air Force had little money for new prop-driven aircraft, especially since jets, such as the Messerschmitt Me 262 and other Luftwaffe fighters had been faster than P-51 Mustangs in the skies of Germany in late 1944. The completed airframes (less engines) of the P-82 pre-production aircraft already manufactured by North American were in storage with an uncertain future.

However, during the 1947 Soviet Aviation Day display at Tushino Airport, a surprise appearance was put in by three four-engined long-range strategic bombers. They were early examples of the Tupolev Tu-4, which was a bolt-for-bolt copy of the Boeing B-29 Superfortress, three examples of which had been interned in the Soviet Union after having been forced to land there during bombing raids against Japan. Since the USSR was expected soon to have nuclear weapons, the appearance of the Soviet Tu-4 was a shock to US military planners, since it meant that the US mainland might soon be vulnerable to nuclear attack from the air.

Until jet interceptors could be developed and put into service, the Twin Mustangs already built were seen as an interim solution to SAC's fighter escort mission for its strategic bomber force and also as an all-weather air defense interceptor.

Early attempts to develop jet-powered all-weather fighters ran into a series of snags and delays. The XP-87 Blackhawk had been ordered in December 1945, but it ran into developmental difficulties and the project was eventually totally abandoned in October 1948. The Northrop P-89 Scorpion was deemed to have greater promise, but it too ran into teething troubles and did not show promise of entering service until 1952 at the earliest. Due to the lack of any suitable jet-powered replacement, the wartime Northrop P-61 Black Widow night fighter was forced into this role, and in order to help fill in the gap until the Scorpion could be available, night fighter adaptations of the piston-engined North American P-82 Twin Mustang were developed and deployed.

On 11 June 1948, the newly formed United States Air Force eliminated the P-for-pursuit category and replaced it with F-for-fighter. Subsequently, all P-82s were re-designated F-82.

Far East Air force

In the years following World War II, the Northrop P-61 Black Widow was the Far East Air Forces (FEAF) primary air defense interceptor. However, a chronic lack of spare parts and constant maintenance made it difficult to keep the war-weary aircraft in the air. Until an all-weather jet interceptor was available, the F-82G Twin Mustang was seen as the interim solution. The last operational P-61s were sent by the 68th and 339th Fighter (All Weather) Squadrons to the reclamation yard at Tachikawa Air Base in February 1950, with Twin Mustangs arriving as replacement aircraft.
In Far East Air Forces, there were three squadrons operating the Twin Mustang consisting of 45 aircraft. The 4th Fighter (All Weather) Squadron was attached to the 51st Fighter-Interceptor Wing at Naha Air Base, Okinawa, with the mission of providing air defense within the Twentieth Air Force's area of responsibility during hours of darkness and inclement weather. The 68th F(AW)S area would cover southern Japan from their base at Itazuke and the 8th Fighter Bomber Wing, with the 339th F(AW)S covering Tokyo and northern Japan from Johnson Air Base. FEAF had about 40 Twin Mustangs assigned to the command.

With the outbreak of the Korean War in June 1950, the F-82 was pressed into operational combat duty. On the night of 24/25 June 1950, 68th Fighter Squadron F-82 aircrews standing alert at Itazuke AB were notified at 0400 that FEAF had received a report that North Korea had crossed the 38th Parallel and their mission was to fly to the area and report back on any activity seen on the main roads and railroads. When the alert aircraft reached the area it was overcast with cloud tops at about 8,000 ft (2,438 m). Using their airborne search radar, the Twin Mustangs flew through the clouds and broke out at about 2,000 ft (610 m), heading for Kimpo Airfield near Seoul. The pilots observed huge convoys of North Korean trucks and other vehicles, including 58 tanks which had crossed into South Korea. Heading back into the clouds and turning back to Japan, the crews returned to Itazuke AB where they were debriefed by a U.S. Army colonel from General Douglas MacArthur's staff. This reconnaissance flight was later recorded as the first combat mission flown in the Korean War.

Farewell from family of Air Force Capt. Johnnie Gosnell, flying with the 68th All-Weather Fighter Interceptor Squadron at Itazuke AB Japan to fly on a combat mission over Korea.

With this information, along with other intelligence reports available to them, FEAF confirmed that the Korean People's Army had, indeed, launched a full-scale invasion of South Korea. FEAF's first priority, however, was to evacuate United States citizens. On the morning of 26 June, the nearby Norwegian freighter Reinholte was sent to Inchon harbor to evacuate non-military personnel from Seoul, which lay directly in the invasion route. A flight of Twin Mustangs from the 68th F(AW)S were dispatched to the area, arriving at dawn to provide air protection for the evacuation. Two of the F-82s were dispatched to fly over the road from Seoul, while others flew Top Cover over the Inchon docks. The patrol went without incident until about 1300, when a pair of Soviet-built aircraft (the exact aircraft type has never been determined) came out of the clouds. Orders given to the F-82 pilots prohibited any aggressive action; however, the gun switches were activated when the leader tightened up his turn and peeled off at the F-82s with his wing man in close tail. The F-82s dropped their external tanks, turned on combat power and started a climbing turn towards the North Korean aircraft. For some reason, the North Korean leader fired while too far away with his bullets falling short of the Twin Mustangs. The F-82s pulled up into the clouds and above the overcast, putting them in a position to return fire if the North Koreans followed them. However, they did not, and no further contact was made for the rest of the day. The evacuation at Inchon was successfully carried out with a total of 682 civilians being transported to Sasebo, Japan.

Flight of 339th FS F-82Gs (46-403, 46-390, 46-366, 46-394) heading to Korea in June 1950.

Once the bulk of civilians had been evacuated out of South Korea by ship, the priority of FEAF changed to a military nature. The 339th F(AW)S received orders from Fifth Air Force to move all available aircraft, along with crews and equipment to Itazuke Air Base to assist the 68th in providing air cover for the evacuation of Seoul. However, the 339th's complement of aircraft were scattered over several bases at the time. Seven F-82s were at Yokota AB which were flyable and two were in the hangar undergoing maintenance for major repairs. Four other F-82s were at Misawa AB on TDY. The three at Yokota were dispatched immediately to Itazuke and well as the four at Misawa making a total of seven combat ready F-82Gs present for duty on 27 June. The 68th F(AW)S had a total of 12 operational F-82Gs. This, combined with what the 339th could contribute was insufficient to meet the combat needs thrust upon FEAF. The F-80 Shooting Star was available, but its thirsty jet engine meant it could only remain over the airfield for a few minutes before having to return to base and could not reach the forward combat area from Japan. No USAF P-51 Mustangs were available, and the British Commonwealth had not yet made a decision to commit to combat Korea, making the Australian Mustangs in Japan academic at this critical situation. FEAF ordered Twentieth Air Force to send eight F-82s from its 4th F(AW)S from Okinawa to Itazuke making a total of 27 F-82s available for combat duty. This was commendable, considering that on 31 May 1950, a total of 32 F-82s existed within FEAF. With these combined squadrons, the 347th Provisional Fighter Group (AW) was formed.

Before dawn on 27 June, the 347th Provisional Group was up in the air over Korea, with a mission to provide cover for the Douglas C-54 Skymaster transports flying in and out of Kimpo Airfield safely as they moved the last civilians out. Fearing that the North Korean Air Force might try to shoot down the transport (a C-54 had been destroyed on the ground at Kimpo by North Korean fighters on 25 June), the Air Force requested air cover to protect the aircraft during takeoff. Fortunately, 339th Fighter All Weather Squadron (F(AW)S) with their F-82Gs were based at Yokota AB and the 68th F(AW)S was based at Itazuke AB Japan. With Lieutenant Colonel John F. Sharp in command, 27 F-82Gs of the 35 in Japan answered the call. Arriving in the early morning, they orbited Kimpo Airfield in three flights, each above the other. Suddenly, at 1150 hours, a mixed lot of five North Korean fighters (Soviet-built Yak-9s, Yak-11s and La-7s) appeared, heading for the airfield. One of the Yak-11s immediately scored several hits on 68th F(AW)S pilot Lt. Charles Moran's vertical stabilizer. Moments later, Lt. William G. "Skeeter" Hudson, also of the 68th F(AW)S, initiated a high-G turn to engage the Yak. Soon Hudson was closing in on the Yak's tail. He then fired a short burst at close range, scoring hits with his six .50 in (12.7 mm) machine guns. The Yak banked hard to the right, with the F-82G in close pursuit. A second burst hit the Yak's right wing, setting the gas tank on fire and knocking off the right flap and aileron. The North Korean pilot bailed out, but his observer, who was either dead or badly wounded, remained in the doomed aircraft. Parachuting down to Kimpo Airfield, the North Korean pilot was immediately surrounded by South Korean soldiers. Surprisingly, he pulled out a pistol and began firing at them. The South Korean soldiers returned fire, killing the pilot. Moments later, Lt. Moran shot down an La-7 over the airfield, while a few miles away, Major James W. Little, commanding officer of the 339th F(AW)S, shot down another La-7. The C-54 was able to escape safely. Of the five North Korean aircraft dispatched, only two returned to their base. In the process, Lt. William G. "Skeeter" Hudson, with his radar operator Lt. Carl Fraiser, had scored the first aerial "kill" of the Korean War.

46-363 and unidentified 68th FS F-82G on the alert ramp at Kimpo AB, South Korea

Considering these crews had not been extensively trained in air-to-air gunnery, they came out of combat looking very good. It is generally believed that the aircraft Hudson and Fraiser flew that day was an F-82G named "Bucket of Bolts" (s/n 46-383), as their usual aircraft was down for repairs. "Bucket of Bolts" would survive the Korean War and eventually be reassigned to escort duty in Alaska. It is believed to have been scrapped at Ladd AFB, Alaska in 1953.

General characteristics

• Crew: 2
• Length: 42 ft 9 in (12.93 m)
• Wingspan: 51 ft 3 in (15.62 m)
• Height: 13 ft 10 in (4.22 m)
• Wing area: 408 ft² (37.90 m²)
• Empty weight: 15,997 lb (7,271 kg)
• Max takeoff weight: 25,591 lb (11,632 kg)
• Powerplant: 2 × Allison V-1710-143/145 counter-rotating liquid-cooled V12 engines, 1,380 hp takeoff (1,029 kW each) each

Performance

• Maximum speed: 482 mph (400 kn, 740 km/h) at 21,000 ft (6,400 m)
• Range: 2,350 mi (1,950 nmi, 3,605 km)
• Service ceiling: 38,900 ft (11,855 m)

Armament

• Guns: 6 × .50 in (12.7 mm) Browning M2 machine guns
• Rockets: 25 × 5 in (127 mm) rockets
• Bombs: 4,000 lb (1,800 kg)