Rolls-Royce Mustang Mk.X: British Experimental Variant

Early Allison-powered Mustang circa 1942.  (Imperial War Museum CH 6710)

The North American Mustang Mk.X, also known as the "Rolls-Royce Mustang" or Mustang X, was an experimental variant of the North American Mustang I, (factory designation Model NA-73) where the Allison engine was replaced by a Rolls Royce Merlin. The improvements in performance led to the adoption of the Merlin, in the form of the licence-built Packard V-1650 version of the Merlin, in following production of the P-51 Mustang.

The Mustang, had been designed and developed by North American Aviation in 1940 to a requirement by the British Purchasing Commission for fighters to equip the Royal Air Force. However while the airframe was sound, the engine did not perform well at the high altitudes characteristic of air to air combat over Europe. Rolls Royce took up a recommendation that the Mustang be tested with a Merlin engine and five aircraft were converted. The aircraft were tested by the British and then the US Army Air Forces.

It is distinct from the Merlin-powered P-51B/C that later followed. The development proceeded incorporating a Rolls-Royce Merlin 65 medium-high altitude engine along with numerous modifications, in an experimental programme undertaken by Rolls-Royce in 1942.

Design and Development

The RAF had, following modifications by Lockheed at Speke to fit an oblique camera and other local British modifications, been actively using the Mustang I (Model NA-73) since early 1942 for Army Cooperation, tactical reconnaissance and as a fighter bomber and loved the aircraft's speed, range and performance.

In April 1942, the Royal Air Force's Air Fighting Development Unit (AFDU) tested the Allison V-1710-engined Mustang at higher altitudes and found it wanting above 18,000 ft (5,500 m). The commanding officer, Wing Commander Ian Campbell-Orde invited Ronald Harker, a test pilot from Rolls-Royce's Flight Test establishment at Hucknall to fly it.

It was quickly evident that performance, although exceptional up to 15,000 ft (4,600 m), was inadequate at higher altitudes. This deficiency was due largely to the single-stage supercharged Allison engine, which lacked power at higher altitudes. Still, the Mustang's advanced aerodynamics showed to advantage, as the Mustang Mk.I was about 30 mph (48 km/h) faster than contemporary Curtiss P-40 fighters using the same Allison powerplant. The Mustang Mk.I was 30 mph (48 km/h) faster than the Supermarine Spitfire Mk Vc at 5,000 ft (1,500 m) and 35 mph (56 km/h) faster at 15,000 ft (4,600 m), despite the latter having a more powerful engine than the Mustang's Allison.

Above 15,000 ft (4,600 m) however, its performance fell off quite rapidly and at 20,000 ft (6,100 m) its maximum speed was 357 mph (575 km/h), which was slower than both the Spitfire Mk V and Messerschmitt Bf 109F. Its rate of climb also decreased significantly and it required eleven minutes to reach 20,000 ft (6,100 m) versus the Spitfire Mk V at seven.

Nonetheless, Harker returned from his flight so enthusiastic, that he immediately phoned Ray Dorey, Head of Rolls-Royce's Experimental Division and asked how quickly a Merlin 61 from the Spitfire Mk IX could be fitted to the aircraft. Within 48 hours Dorey had consulted with Ernest Hives, head of Rolls-Royce and authorisation was given to proceed. Hives put forward a proposal to Air Chief Marshal Sir Wilfrid Freeman (Air Member [of the Air Council] for Production and Design) with the result that Air Ministry and Rolls Royce representatives met on 13 May. By early June the Controller of Research and Development at the Ministry of Air Production had agreed to proceed with installation of Merlin 61 in a Mustang in the UK and - arranged via General Arnold - Packard were to install the Packard V-1650-1 (equivalent to a Merlin XX) in a Mustang in the US.

Rolls-Royce's Chief Aerodynamic Engineer at Hucknall, Witold Challier, did aerodynamic calculations and estimated that the engine/airframe combination would result in a speed of 400 mph with the Merlin XX and with the Merlin 61 441 mph (710 km/h) at 25,600 ft (7,800 m).

Rolls-Royce began the conversions of four Mustangs (RAF serials AM203, AM208, AL963 and AL975) designated Mustang Xs at Hucknall in June 1942. The Ministry had specified enough aircraft that two could be provided to the USAAF. The first converted, AL975, was given a Merlin 65 (instead of the high-altitude Merlin 61 suggested) and a four-bladed Rotol propeller.

With a minimum of modification to the engine bay, the Merlin engine neatly fitted into the adapted engine formers. A smooth engine cowling with an additional "chin" radiator was tried out in various configurations as the two-stage Merlin required a greater cooling capacity than could be obtained with the standard Mustang radiator alone. The Merlin 65 series engine was used in all the prototypes as it was identical to the Merlin 66 powering the Spitfire Mk IX, allowing for a closer comparison. Due to the speed of the conversions, engines were often swapped from aircraft to aircraft as well as being replaced by newer units. The Merlin 65 had been installed on a new engine mounting with the intercooler for the 2-speed, 2-stage Merlin mounted under the nose.

All five development Mustang X aircraft had Merlin 65s, a medium/high altitude engine rather than the Merlin 61 high altitude engine. Visually, the Merlin Mustang differed from its Allison-engined predecessor by the removal of the latter's carburettor air intake above the nose.

Testing

On 13 October 1942, AL975/G was flown for the first time with a Merlin engine on 13 October 1942 by Rolls-Royce's Chief Test Pilot Ronald Shepherd. In November a maximum speed of 413 mph (665 km/h) with full supercharger and 390 mph (630 km/h) with medium supercharger was reached.

The high-altitude performance was a major advance over the Mustang I, with the Mustang X serial AM208 reaching 433 mph (697 km/h) at 22,000 ft (6,700 m) full supercharger at 18 lb of boost and AL975 tested at an absolute ceiling of 40,600 ft (12,400 m). Freeman ( Chief Executive at the Ministry of Aircraft Production - MAP) lobbied vociferously for Merlin-powered Mustangs, insisting two of the five experimental Mustang Mk Xs be handed over to Carl Spaatz (commander of the USAAF in Europe) for trials and evaluation by the U.S. Eighth Air Force in Britain. In this, Lt Col. Hitchcock again played a key role. After sustained lobbying at the highest level, American production started in early 1943 of a North American-designed Mustang patterned after a P-51 Mustang prototype originally designated the XP-78 that utilised the Packard V-1650-3 Merlin engine replacing the Allison engine.

At the same time as the British were investigating the marriage of Merlin engine and Mustang airframe, North American Aviation were also considering the same. Under company designation NA-101, USAAF designation XP-78, they put Merlin 65s provided from the UK into two NA-91s (a cannon armed variant, known in British service as Mustang Mk IA and in USAAF as P-51) that the USAAF had kept for testing. Their first XP-51B (as the XP-78 designation had been changed) flew on 30 November 1942 a couple of weeks after the second Mustang X The aircraft had a four blade Hamilton Standard propeller instead of the three-blade propeller used with the Allison engine. Although the testing of the conversion had been delayed, the USAAF had ordered 400 P-51Bs in August 1942 before any Merlin-engined Mustang had flown.

The pairing of the P-51 airframe and Merlin engine was designated P-51B for the model NA-102 (manufactured at Inglewood, California) or P-51C for the model NA-103 (manufactured at a new plant in Dallas, Texas from summer 1943). There was no difference between these models and the RAF named both these models Mustang Mk.III. In performance tests, the P-51B achieved 441 mph (710 km/h) at 25,000 ft (7,600 m), and subsequent extended range with the use of drop tanks enabled the Merlin-powered Mustang version to be introduced as a bomber escort.

Aircraft

AG518: Used for engine installation studies, but due to a lack of guns, armour and wireless equipment, it was deemed by Rolls-Royce to be "below" latest production standards and not converted.

AM121: This aircraft arrived at the Rolls-Royce Flight Test Establishment at Hucknall on 7 June 1942 and was the first to be delivered but the last to be converted. It hd been provided to act as the baseline comparison. A broader chord fin was installed but the aircraft was not slated for testing at Hucknall and instead was sent to RAF Duxford before being loaned to the 8th Fighter Command USAAF at Bovingdon along with AL963.

AL963: First used for performance and handling trials of the Mustang I before conversion on 2 July 1942; its nose contours had a much "sleeker" appearance due to the intercooler radiator being relocated to the main radiator duct. It was used for "stability and carburation" trials. Other changes included a small fin extension and the "blanking" of cowling louvres. This example was able to reach 422 mph (679 km/h) at 22,400 ft (6,800 m). It was sent to the USAAF Air Technical Section at RAF Bovingdon for evaluation.

AL975/G: First used for performance and handling trials of the Mustang I before conversion on 2 July 1942; flying for the first time on 13 October 1942. The aircraft was identifiable by a bulged lower engine cowling and was also fitted with a four-blade Spitfire Mk IX propeller. In testing, it achieved a top speed of 425 mph (684 km/h) at 21,000 ft (6,400 m).

AM203: The third aircraft was fitted with a four-bladed, 11 ft 4 in diameter Rotol wooden-bladed propeller and achieved 431 mph (694 km/h) at 21,000 ft (6,400 m). It was used to test paint finishes. It was loaned to the USAAF for evaluation in February 1943

AM208: The second conversion had the front radiator flap sealed permanently giving a 6–7 mph (9.7–11.3 km/h) boost. The same modification was subsequently made to all test aircraft.

Advanced Developments

In June 1943, Rolls-Royce proposed to re-engine the Mustang with a Griffon 65, although the resultant "Flying Test Bed" (F.T.B.) would involve a dramatic redesign. Three surplus Mustang I airframes were allotted by the Ministry of Aircraft Production (MAP) and were dismantled in order to provide the major components for a mid-amidships installation of the more powerful Griffon engine, somewhat like the V-1710 Allison installation in the American Bell P-39 Airacobra and Bell P-63 Kingcobra. The project culminated in a mock-up, albeit with a Merlin 61 temporarily installed, serialed as AL960, that was examined by representatives from the Ministry in 1944, but was not given priority status. Further studies involving more powerful engines or turboprops were not given approval and the development contract was cancelled in 1945 and the mock-up was destroyed.

Operators

United Kingdom

Royal Air Force

United States

United States Army Air Forces

Bibliography

Birch, David. Rolls-Royce and the Mustang. Derby, UK: Rolls-Royce Heritage Trust, 1987.

Delve, Ken. The Mustang Story. London: Cassell & Co., 1999.

Gruenhagen, Robert W. Mustang: The Story of the P-51 Mustang. New York: Arco Publishing Company, Inc., 1969.

Newby Grant, William (1981). P-51 Mustang. Bison Books.

Mustang Mk.X AM203 in the third configuration tested with a high-speed paint finish applied by Sanderson and Holmes, the coachbuilders in Derby, UK.

Artist's concept of the proposed Rolls-Royce Flying Test Bed (FTB) Mustang. (Bzuk)

North American A-36 Mustang: American Ground Attack / Dive Bomber

A-36A "Margie H" at the National Museum of the United States Air Force, in the scheme of the A-36A flown by Captain Lawrence Dye of the 16th Fighter-Bomber Squadron in Tunisia, Sicily and Italy.

The North American A-36 (company designation NA-97, listed in some sources as "Apache" or "Invader", but generally called Mustang) is the ground-attack/dive bomber version of the North American P-51 Mustang, from which it could be distinguished by the presence of rectangular, slatted dive brakes above and below the wings. A total of 500 A-36 dive bombers served in the Mediterranean and Southeast Asia theaters during World War II before being withdrawn from operational use in 1944.

The A-36 project was a stopgap measure intended to keep North American Aviation (NAA) assembly lines running during the first half of 1942 despite the US having exhausted its funds earmarked for fighter aircraft.

Design and Development

With the introduction of the North American Mustang Mk I with the Royal Air Force's Army Co-operation Squadrons in February 1942, the new fighter began combat missions as a low-altitude reconnaissance and ground-support aircraft. Supplementing the Curtiss P-40 Tomahawks already in service, Mustang Mk Is were first supplied to No. 26 Squadron RAF, then rapidly deployed to 10 additional squadrons by June 1942. First used in combat over the Dieppe Raid on 19 August 1942, a Mustang of No. 414 (RCAF) Squadron downed one Focke-Wulf Fw 190s, the first victory for a Mustang. Despite the limited high-altitude performance of the Allison V-1710 engine, the RAF was enthusiastic about its new mount, which "performed magnificently".

During the Mustang Mk I's successful combat initiation, North American Aviation's president Howard "Dutch" Kindelberger pressed the newly redesignated U.S. Army Air Forces (USAAF) for a fighter contract for the essentially similar P-51, 93 of which had passed into the USAAF when the Lend-Lease contract with Britain ran out of funds. The Mustang Mk IA/P-51 used four 20 mm Hispano wing cannons in place of the original armament, a combination of four wing-mounted .30 in (7.62 mm) M1919 Browning machine guns and four .50 in (12.7 mm) M2 Browning machine guns. Two were mounted in the wings, while the second pair was mounted in the "chin", or lower engine cowling, and synchronized to fire through the propeller. No funds were available for new fighter contracts in fiscal year 1942, but General Oliver P. Echols and Fighter Project Officer Benjamin S. Kelsey wanted to ensure that the P-51 remained in production.

Since appropriations were available for an attack aircraft, Echols specified modifications to the P-51 to turn it into a dive bomber. The contract for 500 A-36A aircraft fitted with bomb racks, dive brakes, and heavier-duty wing, was signed by Kelsey on 16 April 1942, even before the first flight of the first production P-51 in May 1942. With orders on the books, North American Aviation (NAA) began modifying the P-51 to accept the bomb shackles which had already been tested in a "long-range ferry" program that the RAF had stipulated. Engineering studies totaling 40,000 hours and wind tunnel testing with a 1⁄8-scale model were completed in June 1942. Utilizing the basic P-51 airframe and Allison engine, structural reinforcing "beefed up" several high stress areas and "a set of hydraulically operated dive brakes were installed in each main wing plane". Due to the slightly inboard placement of the bomb racks and unique installation of four cast aluminum dive brakes, a complete redesign of the P-51 wing was required.

The first A-36A (42-83663) was rolled out of the NAA Inglewood plant in September 1942, rapidly going through flight testing with the first flight in October, with deliveries commencing soon after of the first production machines. The A-36A continued the use of nose-mounted .50 in (12.7 mm) machine guns along with wing armament of four .50 in (12.7 mm) caliber machine guns. The USAAF envisaged that the dive bomber would operate mainly at altitudes below 12,000 ft (3,700 m) and specified the use of a sea level-rated Allison V-1710-87, driving a 10 ft 9 in (3.28 m)-diameter three bladed Curtiss-Electric propeller and delivering 1,325 hp (988 kW) at 3,000 ft (910 m). The main air scoop inlet was redesigned to become a fixed unit with a larger opening, replacing the earlier scoop which could be lowered into the airstream. In addition, the A-36 carburetor air intake was later fitted with a tropical air filter to stop sand and grit being ingested into the engine.

The USAAF later ordered 310 P-51As, which were essentially A-36s without the dive-brakes and nose-mounted weapons, leaving an armament of four wing-mounted .50 in (12.7 mm) Browning machine guns. A 1,200 hp (890 kW) Allison V-1710-81 engine was fitted and used the same radiator and air intake as the A-36A. The P-51A was still fitted with bomb racks that were mainly used to carry drop tanks.

Operational History

The A-36A-1-NA "Apache" (although Apache was the A-36A's official name, it was rarely used) joined the 27th Fighter-Bomber Group (27th FBG) composed of four squadrons based at Ras el Ma Airfield in French Morocco in April 1943 during the campaign in North Africa. The 27th had a mixed component of Douglas A-20 Havoc light bombers and A-36As while the second operational unit, the 86th Fighter Bomber Group (Dive) arrived in March 1943 with the first pilots trained and qualified on the A-36A. On 6 June 1943, both of these A-36A units flew combat missions directed against the island of Pantelleria as part of Operation Corkscrew in June 1943 to take the island prior to attack on Sicily. After the surrender of Italian forces on Pantelleria, it became the home base for the two A-36A groups during the Allied invasion of Sicily. The A-36A proved to be a potent weapon: it could be put into a vertical dive at 12,000 ft (3,700 m) with deployed dive brakes, thus limiting the dive speed to 390 mph (630 km/h).[1] Pilots soon recognized that extending the dive brakes after "peel-off" led to some unequal extension of the brakes due to varying hydraulic pressure, setting up an invariable slight roll, which impeded aiming. Proper technique soon cured this anomaly and, subsequently, pilots achieved extremely consistent results. Depending on the target and defenses, the bomb release took place between 2,000 and 4,000 ft (610 and 1,220 m), followed by an immediate sharp "pull up."

Dive brakes in the wings gave the A-36A greater stability in a dive; however, a myth has arisen that they were useless due to malfunctions or because of the danger of deploying them and that they should be wired closed. Capt. Charles E. Dills, 522d Fighter Squadron, 27th FBG, XIIth Air Force emphatically stated in a postwar interview: "I flew the A-36 for 39 of my 94 missions, from 11⁄43 to 3⁄44. They were never wired shut in Italy in combat. This 'wired shut' story apparently came from the training group at Harding Field, Baton Rouge, LA."

However, tactical reconnaissance training with P-51 and A-36 aircraft had delivered some disquieting accident rates. At one time, A-36 training had resulted in the type having "the highest accident rate per hour's flying time" of any USAAF aircraft. The most serious incident involved an A-36A shedding both wings when its pilot tried to pull out from a 450 mph (720 km/h) dive. Combat units flying the A-36A were ordered to restrict their approach to a 70° "glide" attack and refrain from using dive brakes. This order was generally ignored by experienced pilots, but some units did wire dive brakes shut until modifications made to the hydraulic actuators. Nevertheless, the A-36 was used with great success as a dive-bomber, acquiring a reputation for precision, sturdiness and silence.

By late May 1943, 300 A-36As had been deployed to the Mediterranean Theater, with many of the first batch sent to the 27th FBG to re-build the group following losses as well as completing the final transition to an all-A-36A unit. Both groups were actively involved in air support during the Sicilian campaign, becoming especially adept at "mopping up" enemy gun positions and other strong points as the Allies advanced. During this operation, the 27th FBG circulated a petition to adopt the name "Invader" for their rugged little bomber, receiving unofficial recognition of the more fitting name. Despite the name change, most combat reports preferred the name "Mustang" for all of the variants. Author William Hess claims that the Germans gave it a flattering, if fearsome, accolade, calling the A-36As: "screaming helldivers."

Besides dive bombing, the A-36A racked up aerial victories, totaling 84 enemy aircraft downed and creating an "ace", Lieutenant Michael T. Russo from the 27th FBG (ultimately, the only ace using the Allison-engined Mustang). As fighting intensified in all theaters where the A-36A operated, the dive bomber began to suffer an alarming loss rate with 177 falling to enemy action. The main reason for the attrition was the hazardous missions that placed the A-36A "on the deck" facing murderous ground fire. German defenses in southern Italy included placing cables across hill tops to snare the attacking A-36As. Despite establishing a reputation for reliability and performance, the one "Achilles' heel" of the A-36A (and the entire Mustang series) remained the ventral-fuselage location of the radiator/cooling system, leading to many of the losses. By June 1944, A-36As in Europe were replaced by Curtiss P-40s and Republic P-47 Thunderbolts. In the Mediterranean, the A-36A was also used briefly by the Royal Air Force 1437th Strategic Reconnaissance Flight, in Foggia, Italy. The 1437th Flight took the aircraft on loan from the USAAF to replace their Martin Baltimores. These aircraft were painted with RAF roundels and individual aircraft letters and they were also given RAF serial numbers[2] These Royal Air Force had their aircraft chin .50 Browning guns removed.

A-36As also served with the 311th Fighter Bomber Group in the China-Burma-India theater. The 311th had arrived in Dinjan, India by late summer 1943 after being shipped across the Pacific via Australia. Two squadrons were equipped with the A-36A while the third flew P-51As. Tasked with reconnaissance, dive bombing, attack and fighter missions, the A-36A was outclassed by its main opposition, the Nakajima Ki-43 "Oscar." The light and highly agile Japanese fighter could outmaneuver the A-36A at all altitudes but did have some weak points: it was lightly armed and offered little protection for pilot or fuel tanks. However, the A-36A fought at a significant disadvantage, having to carry out long-range missions often at altitudes above The Hump that meant its Allison engine was below peak performance. In a fighter escort mission over Burma, three A-36As were lost without scoring a single victory. The A-36A CBI missions continued throughout 1943–1944 with indifferent results. The A-36A remained in service in small numbers throughout the remaining year of the war, some being retained in the US as training aircraft.

"The type's relatively brief service life should not camouflage the fact that it made a major contribution to the Allied war effort" especially in the Mediterranean and it amounted to the first USAAF combat use of a Mustang variant. The effectiveness of the A-36 as a ground attack aircraft was demonstrated on 5 June 1944. In a well-planned attack on the large, well defended rail depot and ammunition dump at Orte, Italy, Lieutenant Ross C. Watson led a flight of four A-36s through a heavy overcast on the approach to the target. Watson's A-36s scored several hits under intense anti-aircraft fire although his aircraft was damaged by ground fire. Under continuing heavy ground fire, Watson pressed home his attack and destroyed the ammunition dump before making an emergency landing at an advanced Allied airfield.

Operators

United Kingdom

Royal Air Force

One A-36A was supplied to the RAF in March 1943 for experimental purposes. Its RAF serial number was EW998. Six others were loaned.

United States

US Army Air Force

27th Fighter-Bomber Group

86th Fighter-Bomber Group

311th Fighter Bomber Group

Surviving Aircraft

Compared to the P-51 Mustang, relatively few A-36As survived the war and the subsequent postwar retirement and scrapping of obsolete types. One A-36A, bearing race number #44, owned and flown by Kendall Everson, was entered in the 1947 Kendall Trophy Race. It was able to reach 377.926 mph (608.213 km/h), finishing second to the winning P-51D flown by Steve Beville.

Airworthy

A-36A

42-83731 – private owner in Houston, Texas

42-83738 Baby Carmen – Collings Foundation in Stow, Massachusetts

On Display

A-36A

42-83665 Margie H – National Museum of the United States Air Force at Wright-Patterson AFB in Dayton, Ohio.[3]

Specifications (A-36A)

Crew: 1

Length: 32 ft 3 in (9.83 m)

Wingspan: 37 ft 0.25 in (11.28 m)

Height: 12 ft 2 in (3.71 m)

Gross weight: 10,000 lb (4,535 kg)

Powerplant: 1 × Allison V-1710-87 liquid-cooled piston V12 engine, 1,325 hp (988 kW)

Maximum speed: 365 mph (590 km/h, 315 kn)

Cruise speed: 250 mph (400 km/h, 215 kn)

Range: 550 mi (885 km, 478 nmi)

Service ceiling: 25,100 ft (7,650 m)

Guns: 6× 0.50 in (12.7 mm) AN/M2 Browning machine guns

Bombs: Up to 1,000 lb (454 kg) of bombs on two underwing hardpoints

Bibliography

Delve, Ken. The Mustang Story. London: Cassell & Co., 1999.

Freeman, Roger A (1975). Mustang at War. New York: Doubleday and Company, Inc., 1974.

Grinsell, Robert. "P-51 Mustang". Great Book of World War II Airplanes. New York: Wing & Anchor Press, 1984.

Gunston, Bill and Robert F. Dorr. "North American P-51 Mustang: The Fighter that Won the War." Wings of Fame Vol. 1. London: Aerospace Publishing Ltd., 1995.

Gruenhagen, Robert W. Mustang: The Story of the P-51 Mustang. New York: Arco Publishing Company, Inc., 1969.

Hess, William N. Fighting Mustang: The Chronicle of the P-51. New York: Doubleday and Company, 1970.

Kinnert, Reed. Racing Planes and Air Races: A Complete History, Volume IV: 1946–1967. Fallbrook, California: Aero Publishers, Inc., 1969 (revised ed.)

Kinzey, Bert. P-51 Mustang Mk In Detail & Scale: Part 1; Prototype through P-51C. Carrollton, Texas: Detail & Scale Inc., 1996.

Mizrahi, Joe. "Pursuit Plane 51." Airpower, Vol. 25, no. 5, September 1995, pp.5–53.

Smith, Peter C. Straight Down! The North American A-36 Dive Bomber in Action. North Branch, Minnesota: Specialty Press, 2000.

Spick, Mike. "The North American P-51 Mustang." Great Aircraft of WWII. Leicester, UK: Abbeydale Press, 1997.

Taylor, John W.R. "North American P-51 Mustang." Combat Aircraft of the World from 1909 to the present. New York: G.P. Putnam's Sons, 1969.

United States Air Force Museum Guidebook. Dayton, Ohio: Air Force Museum Foundation, Wright-Patterson AFB, 1975.

 

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[1]      "A36A-1 Flight Manual requires deployment before starting a dive".

[2]      A-36 serial 42-14807 became HK947/A, 42-83898 became HK4945/B, 42-84018 became HK944/C, 42-83906 became HK955/D, 42-83829 became HK955/D, 42-83829 became HK956/E and 42-84117 became HK946/F.

[3]      In 1971, Charles P. Doyle of Rosemount, Minnesota obtained 42-83665, subsequently restored by the 148th Fighter-Interceptor Group of the Minnesota Air National Guard, under the command of Colonel Wayne C. Gatlin.

USAAF pilots of a training unit in Louisiana in front of a North American P-51A Mustang fighter in 1943. (USAAF)

Sole RAF A-36A on demonstration flight showing dive brakes, circa 1943. (RAF)

Production of A-36A fighter planes at North American Aviation at Inglewood, California, in October 1942. (United States Library of Congress's Prints and Photographs division under the digital ID fsa.8b13087)

A-36A Mustang of the 86th Fighter Bomber Group (Dive) in Italy, 1944. (USAAF)

A-36 Apache s/n 42-84057 of the 27th Fighter Bomber Group, lost to flak on 14 January 1944. (USAAF)

Sole RAF A-36A on demonstration flight showing 500 lb bombs, circa 1943. (RAF)

Sole RAF A-36A on demonstration flight showing 500 lb bombs, circa 1943. (RAF)

A-36A s/n 42-83721. (Bill Larkins)

A-36A in Inglewood, California. (USAAF)

North American A-36 s/n #42-83671. (USAAF)

A-36 “Chihuahua” in Alaska. (Signal Corps Archive)

A-36 Apaches in formation. Nearest aircraft is s/n 4283707. (San Diego Air and Space Museum Archive)

A-36 Apaches loaded on transport for Lend Lease shipment. (National Archives and Records Administration, cataloged under the National Archives Identifier (NAID) 197296)

North American A-36A Mustang.