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North American P-51 Mustang (Part 4)

By Joe Baugher

The P-51D/K with its bubble-top canopy was perhaps the best-known version of the Mustang. It was also the most widely used variant of the Mustang, a grand total of 7956 machines of this type being produced (6502 at Inglewood and 1454 in Dallas).

One of the problems encountered with the Merlin-powered P-51B/C was the poor view from the cockpit, particular towards the rear. The "Malcolm hood" fitted to the P-51B/C was an early attempt to correct this deficiency. However, a more lasting solution was sought, and it was thought that the Mustang might be amenable to being equipped with a bubble-type all-round vision canopy similar to those fitted by the British to later marks of the Supermarine Spitfire and the Hawker Typhoon. Following discussions with the British and after examination of the clear-blown "teardrop" canopies of later Spitfires and Typhoons, North American Aviation secured an agreement with the Army to test a similar canopy on a Mustang in order to improve the pilot's view from the cockpit.

One of the early P-51B-1-NAs was chosen for the initial modifications. The new bubble-shaped hood gave almost completely unobstructed vision around 360 degrees with virtually no distortion. The large rear section did not reach its point of maximum height until a point well behind the pilot's head was reached, since wind tunnel testing showed that this shape was found to offer the best combination of viewing angles and minimum aerodynamic drag. The Plexiglas of the hood was mounted in rubber in a metal frame, the sill around the bottom being very deep. This was needed to provide the strength and rigidity required to avoid distortion and to prevent the binding or jamming of the canopy in the fuselage rails while it was being opened and closed. There were three rails, one along each side of the cockpit and one along the upper centerline of the rear fuselage. The canopy was manually opened and closed by a handle crank operated by the pilot.

In order to accommodate the new all-round vision hood, the rear fuselage of the Mustang had to be extensively cut down. However, the amount of retooling needed to accomplish this was not extensive, and very little restressing of the fuselage structure was necessary.

Having proven the concept, NAA diverted two P-51B-10-NAs (serial numbers 42-106539 and 42-106540) from the Inglewood production line and completed them as NA-106s with cut-down rear fuselage and bubble canopy. These two aircraft were redesignated P-51D.

One of the shortcomings of the P-51B was its limited firepower of only four machine guns. In addition, the guns in each wing were tilted over at quite sharp angles, requiring a sharp kink in the ammunition belt feeds and resulting in frequent gun jams. NAA took the opportunity afforded by the introduction of the new Mustang to correct this problem. The gun installation was completely redesigned, and the result was the installation of three 0.50-inch machine guns in each wing, all of them mounted upright and all fed by unkinked ammunition belts. The inboard guns each had 400 rpg, and the others had each had 270 rpg. However, Mustang users had the options of removing two of the guns and having just four, with 400 rounds each, and some pilots did actually select this option.

Another visible change introduced by the P-51D was in the increase of the wing root chord. The main landing gear was strengthened in order to accommodate the additional weight, but the wheels maintained the same diameter of 27 inches. However, the wheel bays and doors were modified and the "kink" in the wing leading edge was made much more pronounced. The "kink" in the wing of the P-51B was barely noticeable, but it was much more pronounced in the P-51D.

Four P-51D-1-NA Mustangs had been completed with the original B-type canopy before the first P-51D-5-NA model (company designation NA-109) rolled off the production line.

Readers may recall the problems with the installation of the 85-gallon tank in the rear fuselage of the P-51B and its adverse effects on the directional stability. Things got still worse for the P-51D, in which the cutting down of the top line of the rear fuselage caused a lot of keel area to be lost. In order to provide for better directional stability, a dorsal fin was added ahead of the rudder very early on in the production run of the P-51D. Some of the earlier P-51Ds (plus a few P-51Bs) were retrofitted with this dorsal fin. The extra weight and drag caused by this fin was quite small, but it helped a lot in improving the directional stability, especially when the rear fuselage fuel tank was full.

The P-51D/K introduced the K-14 computing gyro gunsight, based on a British design. The pilot needed only to dial in the wingspan of the enemy aircraft he was chasing, feed in the target range by turning a handgrip on the throttle lever, then get the wingtips of his target lined up on the bright ring projected on the gunsight, and press the trigger.

P-51Ds were also constructed in NAA's Dallas plant, the Dallas plant building some 1454 of these planes before production finally ceased.

Almost all Block-25 and subsequent Ds had underwing hardpoints not only for bombs and fuel tanks but also for various types of rocket launchers. These included zero-length stubs for six 5-inch rockets or as many as ten if no drop tanks were carried. Alternatively, "Bazooka" tubes could be carried in triple clusters.

The Dallas plant also built 1337 P-51Ks, which differed from the P-51D in having an 11-foot diameter Aeroproducts propeller in place of the 11 feet 2 inch diameter Hamilton Standard unit. The P-51K had a slightly inferior performance to that of the P-51D. Rocket stubs were introduced on the -10-NT and subsequent batches of the K production line at Dallas.

A total of 163 P-51Ks were completed as F-6K photo-reconnaissance aircraft. 126 Inglewood-built P-51Ds from blocks 20, 25, and 30 were converted after completion as F-6Ds. A few others were similarly converted near the end of the war. All of these photographic Mustangs carried two cameras in the rear fuselage, usually a K17 and a K22, one looking out almost horizontally off to the left and the other one down below looking out at at an oblique angle. Most F-6Ds and Ks carried a direction- finding receiver, serviced by a rotating loop antenna mounted just ahead of the dorsal fin. Most F-6Ds and Ks retained their armament.

Several Dallas-built P-51Ds were modified as two-seat trainers with an additional seat fitted behind the pilot's seat. Serial numbers were 44-84610, 44-84611, 44-84662, and 45-11443/11450. These were given the designation TP-51D. In order to accommodate the second seat, the radio equipment had to be relocated and an additional seat with full dual controls was installed behind the normal seat. The standard bubble canopy was large enough to accommodate the extra seat. One of the TP-51Ds was modified for use as a special high-speed observation post by Supreme Allied Commander General Dwight D. Eisenhower, which he used to inspect the Normandy beach-heads in June of 1944.

The P-51D began to arrive in Europe in quantity in March of 1944. The 55th Fighter Group was the first to get the P-51D, trading in its P-38s for the new bubble-topped fighters. The change from the torqueless twin-engined P-38 to the single-engined P-51 did cause some initial problems, and the lack of directional stability caused by the presence of a full fuselage tank took a lot of getting used to. However, once their pilots became fully adjusted to their new mounts, they found that the P-51D possessed a marked edge in both speed and maneuverability over all Luftwaffe piston-engined fighters at altitudes above 20,000 feet. However, Luftwaffe pilots considered the Mustang to be rather vulnerable to cannon fire, particularly the liquid-cooled Merlin engine which could be put out of action by just one hit.

The Mustang was the only Allied fighter with sufficient range to accompany bombers on their "shuttle" missions in which landings were made in Russia after deep-penetration targets had been attacked from English bases. The Mustangs also participated in low-altitude strikes on Luftwaffe airfields, a rather dangerous undertaking as these fields were very heavily defended by flak.

In 1943, the Allies were aware that the Luftwaffe was planning to introduce jet-powered aircraft over Germany, and that these would provide a serious threat to Allied bombers and to their escorting fighters. Mustangs first encountered Messerschmitt Me 163 Komet rocket-powered fighters on July 18, 1944, when a pair of Me 163s flew unscathed through a flight of P-51s. On August 5, 1944, Me 163s destroyed three bombers and shot down three escorting P-51s. On August 16, a Mustang flown by Lt. Col. John B. Murphy of the 359th Fighter Group finally managed to shoot down a Me 163. Although the Me 163 gained much publicity and threw the Allied high command into a near panic, the rocket-powered fighter had an extremely short endurance in the air and was very dangerous to fly. It is doubtful that these rocket-powered fighters destroyed more than a dozen or so Allied aircraft during the entire course of the war.

Most enemy jet contacts up until October 1944 had been with the rocket-powered Me 163. In that month, the Messerschmitt Me 262 began to appear in combat. The first jet kill by a Mustang was on October 7, 1944, when Lt. Urban L. Dreq of the 361st Fighter Group shot down two Me 262s while they were taking off from their base. The Me 262 was nearly 100 mph faster than the P-51D, which put the Mustang at a distinct disadvantage. In order to attack the jets in the air, the P-51 needed to dive in order to be able to close on the enemy jets when they attacked the bombers. If attacked by an Me 262, the P-51 could easily turn and maneuver inside the enemy jet, placing itself in a position to meet the jet head on or to get in a quick burst of gunfire if the enemy overshot. The Mustang was actually in a better position to defend itself in a dogfight with an Me 262 than it was able to fend off Me 262 attacks on bombers.

Eventually it was decided that the best strategy in fighting the jets was to jump them while they were taking off from or landing at their bases. The early jets had very poor acceleration and were thus extremely vulnerable during takeoff and landing. The usual tactic was for scores of Mustangs to circle high over known Me 262 bases, daring the jets to take off. If any rose to the challenge, diving Mustangs would be upon them almost before their wheels could be retracted. If the Messerschmitts refused to take the bait, the bases would be strafed and the jets would be destroyed on the ground.

Units operating the P-51D in the ETO included the following:

4th Fighter Group, 8th Air Force

20th Fighter Group, 8th Air Force

27th Fighter Group, 12th Air Force

31th Fighter Group, 15th Air Force

52nd Fighter Group, 15th Air Force

55th Fighter Group, 8th Air Force

67th Tactical Reconnaissance Group, 9th Air Force

68th Tactical Reconnaissance Group, 9th Air Force

69th Tactical Reconnaissance Group, 9th Air Force

78th Fighter Group, 8th Air Force.

325th Fighter Group, 15th Air Force.

332nd Fighter Group, 15th Air Force. This was the famous all-black outfit.

339th Fighter Group, 8th Air Force.

352nd Fighter Group, 8th Air Force.

353nd Fighter Group, 8th Air Force.

354th Fighter Group, 9th Air Force.

355th Fighter Group, 8th Air Force.

356th Fighter Group, 8th Air Force.

357th Fighter Group, 8th Air Force.

359th Fighter Group, 8th Air Force.

361th Fighter Group, 8th Air Force.

363rd Fighter Group, 9th Air Force.

364th Fighter Group, 8th Air Force.

370th Fighter Group, 9th Air Force.

479th Fighter Group, 8th Air Force.

Several Mustang pilots became "ace-in-a-day", scoring five or more victories during one mission: Lt. William R. Beyer of the 361st Fighter Group, Capt. William T. Whisner, Capt. Donald S. Bryan of the 352nd Group, Lt. Claude J. Crenshaw of the 359th Group, Capt L. K. Carson of the 357th Group, Lt. J. S. Daniel of the 339th Group, Capt. William J. Hovde of the 355th Group, and Mister Right Stuff himself, Capt. Charles E. "Chuck" Yeager of the 357th Group. Maj. George Preddy of the 352th Group held the ETO Allied record of six victories on one mission, which he achieved on August 6, 1944. Major Preddy was the top USAAF Mustang ace of the war, scoring 23.83 out of his 26.83 victories while flying a P-51. (Why this odd fraction?)

The top-scoring Mustang-equipped fighter group was the 357th, with 609 air and 106 ground kills from February 11, 1944 to April 25, 1945.

By the time that Germany surrendered, all of the Escort Groups of the 8th Air Force and some of the groups in the 9th Air force had converted to P-51s.

Because of the higher priority of the war in Europe, the P-51D Mustang did not arrive in the Pacific until late in 1944. P-51Ds were initially based in the Philippines and on Iwo Jima. By that stage of the war, Japanese fighter opposition was rare, and Philippine-based Mustangs mostly performed close-support work. However, while flying over Japanese-occupied regions of Luzon, Captain William A. Shomo managed to shoot down six Tonys and one bomber in one day while flying an F-6D photo-recon aircraft. For this action, he was awarded the Congressional Medal of Honor.

As Japanese resistance on Luzon came to an end, the Philippine-based Mustangs were used to bomb and strafe Japanese forces based on Formosa. Iwo Jima-based Mustangs flew the first escort missions with B-29 bombers attacking Japan, and they undertook the first land-based fighter strikes against Tokyo on April 7, 1945, when B-29s hit the Nakajima Aircraft Engine Factory. Such missions involved flights lasting up to seven or eight hours, covering distances of over 1500 miles. When General Curtis LeMay decided that most B-29 missions would take place at night from medium altitudes, the Iwo Jima-based Mustangs went over to ground attack missions against Japanese airfields. Extensive use was made of the five-inch rockets which were carried under each wing.

The P-51D remained in service in considerable numbers with the USAAF for many years after the Second World War ended. In 1948, the newly-formed USAF eliminated the P-for-pursuit category and replaced it with F-for-fighter. The designation of the P-51 was changed to F-51. In addition, the old category of F for photographic reconnaissance was eliminated, and F-6D and F-6K photographic reconnaissance aircraft became RF-51D and RF-51K respectively. Two seat F-6D conversions became TRF-51D.

In May 1946, the Air National Guard (ANG) was reformed and ANG fighter units received most of the P-51D/K Mustangs withdrawn from regular USAAF service. By December of 1948, over 700 Mustangs were serving with 28 ANG squadrons. RF-51D reconnaissance aircraft also served with the ANG. No fewer than 22 of the 27 ANG wings saw service in the Korean War.

The Mustang was in action once again when the Korean War began on June 25, 1950. The Mustang was better suited to the small airstrips of Korea than were the F-80s and F-82s based in Japan. Japan-based F-51Ds were immediately transferred to Korea and pressed into service in an attempt to halt the rapid North Korean advance. The Mustangs were based at Kimpo, Pusan, and Pohang, flying out of one field then another in close support operations against the advancing North Koreans. They were called on to carry the brunt of air support missions during these difficult early days of the war, since the jet aircraft of the day did not have enough range to permit sufficient loiter time over the target.

In order to build up close support forces, 145 F-51s were brought over from the USA aboard the aircraft carrier USS *Boxer*. These planes were quickly assembled and flown out to combat units. The 18th Fighter-Bomber Wing gave up its F-80 jets for Mustangs, perhaps one of the few occasions in history in which a combat outfit traded in its jets for piston-engined aircraft. The Mustangs were instrumental in halting the North Korean advance, giving United Nations forces enough time to build up sufficient strength to be able to go over onto the offensive. Mustangs flew 62,607 tactical support combat missions. 351 Mustangs were lost in action, most of them the victims of antiaircraft fire.

Although their primary mission was close support, they did manage to shoot down a few North Korean Yaks when these aircraft made their infrequent appearances. When Mustangs were jumped by Chinese-piloted MiG-15 jet fighters, however, they were faced with an opponent with a far superior performance. When this happened, there was little the Mustangs could do save to try to turn inside the MiGs, hit the deck, and run for home.

The last American active-duty Mustang was P-51D-30-NA Ser No 44-74936, which was finally withdrawn from service with the West Virginia ANG in 1957. This airplane is now on display at the WPAFB Museum in Dayton, Ohio. It is, however, painted as P-51D-15-NA Ser No. 44-15174.

Specs of the P-51D-25-NA: one 1695 hp Packard Merlin V-1650-7 twelve-cylinder Vee liquid-cooled engine. Maximum speed: 395 mph at 5000 feet, 416 mph at 10,000 feet, 424 mph at 20,000 feet, 437 mph at 25,000 feet. Range was 950 miles at 395 mph at 25,000 feet (clean), 2300 miles with maximum fuel (including drop tanks) of 489 US gallons under most economical cruise conditions. Initial climb rate was 3475 feet per minute. An altitude of 5000 feet could be reached in 1l7 minutes, 10,000 feet in 3.3 minutes, 20,000 feet in 7.3 minutes. Service ceiling was 41,900 feet. Weights were 7125 pounds empty, 10,100 pounds normal loaded, 12,100 pounds maximum. Wingspan was 37 feet 0 1/4 inches, length was 32 feet 3 inches, height was 8 feet 8 inches, and wing area was 233 square feet.

Serials of the P-51D:

44-11153/11352 North American P-51D-5-NT Mustang

44-12853/13252 North American P-51D-20-NT Mustang

44-13253/14052 North American P-51D-5-NA Mustang

44-14053/14852 North American P-51D-10-NA Mustang

44-14853/15752 North American P-51D-15-NA Mustang

44-63160/64159 North American P-51D-20-NA Mustang

44-72027/72626 North American P-51D-20-NA Mustang

44-72627/74226 North American P-51D-25-NA Mustang

44-72227/75026 North American P-51D-30-NA Mustang

44-84390/84989 North American P-51D-25-NT Mustang

45-11343/11542 North American P-51D-25-NT Mustang

45-11543/11742 North American P-51D-30-NT Mustang

Serials of the P-51K:

44-11353/11552 North American P-51K-1-NT Mustang

44-11553/11952 North American P-51K-5-NT Mustang

44-11953/12852 North American P-51K-10-NT Mustang

Sources:

American Combat Planes, Ray Wagner, Third Enlarged Edition, Doubleday, 1982.

The American Fighter, Enzo Angelucci and Peter Bowers, Orion Books, 1987.

War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday 1964.

United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

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

Classic Warplanes: North American P-51 Mustang, Bill Gunston, Gallery Books, 1990.

Famous Fighters of the Second World War, Volume I, William Green, 1967.

British Military Aircraft Serials, 1912-1969, Bruce Robertson, Ian Allen, 1969.

Joe Baugher

AT&T Bell Laboratories

2000 North Naperville Road

Naperville, Illinois 60566-7033