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North American NA-73 / P-51 Mustang / A-36 Apache / P-78

na-mustangs
P-51D, P-51C, P-51D

 

Early in 1940 J.H.Kindelberger, president of North American Aviation, and J.L.Atwood, executive vice-president of the company, were called into conference with the British Purchasing Commission in New York. The British requested they build the Curtiss P-40. Kindelberger suggested they could build a better airplane, and faster. The ‘go ahead’ was given.
Kindelberger and Atwood conferred with Ray H. Rice, then chief engineer; Edgar Schmued, design engineer; E.J.Horkey, aerodynamicist, and others. The first conferences started on 5 April 1940 with Ken Bowen serving as project engineer. Others soon became involved.
 
 NA-P51-team
 
Rice ordered a low-drag, high-lift wing. Horkey had what was then considered a radical idea on airfoils and went to work with his assistants.
 
The prototype was not built from production drawings but design layouts, so fast was the work done. It was ready to fly and awaiting the installation of its 1150 hp Allison engine just 100 days from the time the first drawings were made.
 
A month before the first flight, design for production was started. In September, Bowen was assigned the job of production engineer, assisted by George Gehrkens.
 
With certain unorthodox designs involving compound curves, flush shin joints for absolute smoothness, the job of tooling up for thousands of planes fabricated by unskilled workers became a problem.
 
As no production drawings had been made it became necessary for more than 100 men to devote themselves to this job. Each part had to be considered for re-design or simplification to make it adaptable to mass production methods. Those used in production of T-6 and B-25 were brought in. In all, 2990 design drawings were made. Others were used in making flight tests and wind tunnel tests.
 
Lieut.Gen. James Dolittle would call in and try out the experimental model. Immediately the throttle was moved closer to the pilot’s seat to make operation easier for short arms.
 
 NA-NA73X-01
North American NA-73X NX19998
 
First flying on 26 October 1940, piloted by Vance Breese. Flights of the prototype revealed the need for many changes. Wind tunnel tests conducted by Horkey at California Institute of Technology revealed the need for more changes. For instance, flight tests showed that the air scoop intake had to be lowered to increase and alter air flow. Wind tunnel tests revealed to need to raise the carburettor air intake. A combination of tests showed that 50 pounds could be whittled off the flaps without any loss in aerodynamic efficiency. Flight test disclosed that a change in windshield design was in order.
 
Nine months after design for production was started the first production airplane rolled off the line.
 
The X-73 had been built in accordance with United States Army specifications but without Army supervision, as the contract was with the British. The first production NA-73 was delivered to the British in November 1941. The fifth and tenth off the production line went to the United States Army (41-038/039 for testing and experimentation. The next 150 were known as P-51’s.

 

Fitted with the same Allison V-1710 engine as the P 40, the Mustang proved to be a useful close support fighter and tactical reconnaissance aircraft. The aeroplane was soon ordered by the British and Americans as the Mustang and P-51 respectively.

 
 NA-P51-11
North American XP-51 41-039
 
In June 1942 engineering on the A-36 began. It was equipped with dive brakes, bomb racks and six .50 calibre machine guns. It was found that it could dive and climb almost vertically, powered by a 1350 hp Allison. The A-36 order was the first from the United States Army. The first was tested in September 1942 and production was completed by March 1943.
 
Two Mustangs sank an Italian cruiser and another sank an Italian transport which had been one of the world’s greatest luxury liners.
 
In 1941 one hundred and forty eight P-51 NA-91 (41-37320-37351, 41-37353-37420, 41-37422-374690 were built, of which 2 became test beds for Packard V-1650 as XP-51B (XP-78), and of which many early models became A-36A, plus 650 NA-73/NA-83 for RAF as Mustang I/IA (many were converted in England to Rolls-Royce Merlin).
 
 NA-P51-09
North American Mustang I
 
The design showed promise and AAF purchases of Allison-powered Mustangs began in 1941 primarily for photo recon and ground support use due to its limited high-altitude performance. A total of 310 P 51As were built. The 1942 P-51-1 armed recon adaptation with four wing cannon and two K-24 cameras was briefly designated F-6A at first, the unique final designation signified a batch of 57 withdrawn from an RAF Mustang I contract for USAAF duty. Fifty P 51As were allocated to the RAF as Mustang Mk IIs, while 35 were converted to F 6B tactical reconnaissance planes. Top speed was 390 mph.
 

 

 NA-P51-13
 
P-51A
 
 
The initial P-51 and P-51A variants proved only moderately successful but in 1942, tests of P-51s using the British Rolls-Royce "Merlin" engine revealed much improved speed and service ceiling.
 
 
After some Allisom-powered P-51A were built, the Rolls-Royce Merlin, developing 1650 hp and equipped with two-stage, two-speed supercharger with a critical altitude of better than 30,000 ft, was in production and available to North American. The P-51B emerged with the Merlin and a four-blade propeller. It went into production in the late spring of 1943. The P-51B carried four .50 calibre machine guns and bomb racks. Dive brakes were eliminated. The radiator installation was redesigned and bubble canopy fitted. The plane was strengthened to carry the larger engine. New ailerons gave improved performance. The plane was cleaned up from spinner to rudder.
 
 
 NA-P51-14
 
Wind tunnel model tests new tail fairing
 
 
Changes were being made daily, even while the planes flowed from the final assembly. Improved manufacturing methods resulted in each unit being produced with only 3300 man-hours.
 

NA-P51-15

P-51B
 
 
The first P-51B’s were delivered to a combat group early in November 1943. Seventeen days later, on 1 December, they conducted their first operation over enemy territory. Early in January, the group knocked down 18 German combat planes without a single loss, which was a record. A week later, the group accounted for 15 aircraft without loss. They netted a total of 103 German aircraft 83 days after starting operations, beating the Thunderbolt record of 100 planes in 85 days.
 

The P-51C was built in the newly constructed North American factory in Dallas, Texas, and was essentially the same as the P-51B.

In 1943 a bubble canopy was adopted for the P-51D, which became the main version of the famous fighter and entered combat over Europe in March 1944.

The aircraft is stressed for aerobatics and is capable of most all maneuvers with the exception of sustained inverted flight, snap rolls, outside loops, and inverted spins.

 

 



There are a number of variables regarding engines. The basic engine is the Packard built V-1650-7. The V-1650-9 was also used and is interchangeable. This V-12 engine is designed with 2 removable Cylinder bank assemblies of 6 cylinders each. These are referred to as head and banks. There are a number of engines that have been fitted with the" Transport Heads."   "Transport Heads" refer to British built assemblies that were used on a commercial aircraft engine and were designed for long life.

The basic V-1650-7 engine lower end will have a TBO in civil use of about 600 hours. The V-1650-7 heads and banks will probably require some rework at about 300 hours. The transport heads will normally last to TBO and beyond.

The P-51D holds 184 US gallons. The military used drop tanks of a maximum capacity of 110 gallons each and had a 85 gallon rear fuselage tank . Most civil operators do not use drop tanks and have a rear jump seat in place of the fuselage tank. With a normal cruise fuel burn of 65 GPH, this gives a 2 2 hour endurance with a small reserve.

A steerable type system uses an interconnect from the rudder pedals to the tailwheel steering system.  This allows the pilot to steer the aircraft by use of the rudder pedals. Full forward stick movement unlocks this system. When unlocked the tailwheel becomes full swivel and steering is accomplished by differential braking.

The aircraft uses a low-pressure 1000 psi hydraulic system.  The pressure is controlled and maintained by a regulator. The pilot simply operates the flaps or the gear and it works automatically. The wheel brakes are non-boosted, hydraulically actuated from individual master cylinders. The aircraft use standard MIL-5060 (red) fluid.

The aircraft has a 24 Volt D.C. system with a 100-amp generator. Some aircraft have an alternator installed. Normal aircraft have no AC electrical devices installed. A standard battery is used to provide starting and back up power. The aircraft does not require a ground power cart for normal use.

 

The definitive P-51D variant amounted to 7,966 of the 15,469 Mustangs.
 

The only AD on the P-51 is 81-13-01. The AD calls for inspection of the Hamilton Standard prop for corrosion. This AD starts out with an 18 month inspection interval and the interval lengthens to 60 months as the prop builds a history.

 

 NA-P51-08
Four P-51D of the 8th Army Air Force’s 361st Fighter

 

The only AD on the P-51 is 81-13-01. The AD calls for inspection of the Hamilton Standard prop for corrosion. This AD starts out with an 18 month inspection interval and the interval lengthens to 60 months as the prop builds a history.

The RNZAF received 30 P-51Ds in late 1945 of what would have been 370 replacements for Corsairs. War’s end led to the cancellation of the remainder.

Providing high-altitude escort to B-17s and B-24s, they scored heavily over German interceptors and by war's end, P-51s had destroyed 4,950 enemy aircraft in the air, more than any other fighter in Europe.

Mustangs served in nearly every combat zone, including the Pacific where they escorted B-29s to Japan from Iwo Jima. Between 1941-5, the AAF ordered 14,855 Mustangs (including A-36A dive bomber and F-6 photo recon versions), of which 7,956 were P-51Ds.

naa-36apache
A-36 Apache


A total of 15386 aircraft were built including 500 A-36As and 120 P-51Ds assembled in Australia (CAC CA-17). 620 were exported to the RAF for a total to the USAAF/USAF of 14,365.

During the Korean War, P-51Ds were used primarily for close support of ground forces until withdrawn from combat in 1953.

The U.S. Military and the Royal Canadian Air Force made the largest surplus release of these aircraft in the late 50's and early 60's. A number of aircraft previously served with the forces of over seas countries. The aircraft sold as surplus in 1958 for prices ranging from $800-1500. The Mustang is probably the most recognized fighter of World War II and has proven to be a popular and widely used civilian Warbird.

Many people refer to the "Cavalier" Mustang as the ultimate conversion for civilian use. This conversion was performed by Trans Florida Aviation of Sarasota in the mid 60's to the early 70's. While this conversion was very nice at that time, most restorations done in the last 10-15 years are of superior quality. The Executive Mustang, or Cavalier, rebuild and conversion involved plush, soundproofed cockpit, IFR electronics, baggage compartments in former gun bays, 402-gal fuel tanks, and zero-time majored 1500hp Packard-Merlin V-1650-7 engine. SYSTEMS
 
Successor to Trans-Florida Aviation, acquired during 1960s type certificate for North American F-51 Mustang, producing tandem two-seat business/sport conversions of F-51D as Cavalier 2000 series, and building new single-seat F-51Ds for the USAF counterinsurgency Military Assistance Program. Prototype of Mustang II, two-seat COIN patrol/attack version equipped with heavier armament, flew December 1967; prototype Turbo Mustang III (with Rolls-Royce Dart) in 1969. Second prototype flew in April 1971, equipped with Lycoming T55 engine, by which time the program had been sold to the Piper Aircraft Corporation, but then the company was dissolved.
 
Priced at $32,500 less radio 19 were reportedly under way by the end of 1959 (44-11558=N6175C, -72844=N5076K, -73027, -73260=N5075K, -73411=N550D, -73584=N51Q, -73656=N5073K, -73843=N351D, -74427, -74441, -74453, -74458/74459, -74469=N7723C, -74831, -74854, -84658=N7724C, 45-11381=N5471V, -11489=N5421V).
 
Executive Mustang / Cavalier variants:
 
Cavalier 750
1959
No tip tanks.
 
Cavalier 1200
1960
As 750
with two additional 45-gal internal wing tanks.
 
Cavalier 1500
1960
As 750, with two additional 63-gal internal wing tanks.
 
Cavalier 2000
1967
110-gal tip tanks.
 
Cavalier 2500
As 2000, with two additional 63-gal internal wing tanks.
 
Cavalier Mustang II
1967
F-51D modified for counter-insurgency duties
1760hp RR Merlin 620.
2 built.
 
Turbo Mustang III
1968 or 1971

Prototypical COIN design for production by Piper Co as PA-48 Enforcer.

The TF-51D was originally built by TEMCO aircraft and incorporated a full rear cockpit with Dual Controls. In the last several years this conversion has been produced by a California company and is very popular. It added about $250,000 to the price of a Mustang.

 

na-p-51
 
 
LSA / Ultralight Replicas:
Loehle Aviation 5151
FK Lightplanes FK51 Mustang


Experimental Replicas:

Stewart S-51D
Papa 51 Inc Thunder Mustang
Thunder Builders Group Thunder Mustang
Titan Aircraft P-51
Falconair SAL Mustang P-51
Cameron & Sons P-51
KWP-51 K-W Mustang
Bonsall Mustang MkII

 

P-51 Mustang variant production


Production

XP-51
Number built/Converted 2
Model NA-73; Developed for UK

P-51
Number built/Converted 150
Prod. model; 4 20mm cannon

P-51A
Number built/Converted 310
Fitted w/ bomb racks; 4 .50-cal. mgs

XP-51B
Number built/Converted 2
Imp. P-51; was XP-78

P-51B-NA
Number built/Converted 1988
Prod. model; Blks 1-15; Inglewood

P-51C-NT
Number built/Converted 1750
Dallas Plant; Blks 1-11

P-51D-NA
Number built/Converted 6502
Bubble Canopy; Blks 1-30

P-51D-NT
Number built/Converted 1454
Blks 5-30; 6 .50-cal. mgs.

TP-51D-NT
Number built/Converted 10
2-place trainer variant

P-51E
Number built/Converted 0
Model not assigned

XP-51F
Number built/Converted 3
Exp. lt. weight test model

XP-51G
Number built/Converted 2
Mod. XP-51F w/ new eng.

P-51H-NA
Number built/Converted 555
Prod. model; Blks 1-10

XP-51J
Number built/Converted 2
Mod. XP-51F w/ new eng.

P-51K-NT
Number built/Converted 1337
Imp. -D; Aeroprop; Blks 1-15

P-51L-NA
Number built/Converted 0
Imp. -H w/ new eng.

P-51M-NT
Number built/Converted  1
Imp. -H w/ new eng.

 

 



Specifications -

 

NA-73X
Engine: Allison V-1710, 1100 hp
Wingspan: 37'0"
Length: 32'2"
Useful load: 2250 lb
Max speed: 387 mph
Cruise speed: 307 mph
Stall: 120 mph
Range: 350 mi
Seats: 1

 

XP-51 / NA-73
Engine: Allison V-1710-39, 1100hp
Wing span: 37'0"
Length: 32'3"
Useful load: 1687 lb
Max speed: 382 mph
Cruise speed: 300 mph
Range: 625 mi

Ceiling: 30,800 ft

P-51A / Mustang Mk.II
Engine: Allison, 1200 hp
Max speed: 394 mph @ 15,000 ft.

P-51B
Max speed: 441 mph
Max range: 1300 mph
Armament: 4 x .50 in Browning mg
Bomb load: 2 x 1000 lb

P-51C
Engine: Merlin V-1650/3, 1210 hp @ 25,800 ft
Max speed: 439 mph
Max range: 2700 miles
Armament: 4 x .50 in Browning mg
Bomb load: 2 x 1000 lb

P-51D
Engine: Packard Merlin V-1650-7 or V-1650-9, 1450 hp / 1,695 hp
Propeller: Hamilton Standard 4-Blade 24D50, 134"
Span: 37 ft 0.25 in / 11.89 m
Length: 32 ft 3.25 in / 9.85 m
Height: 13 ft 8 in / 4.16 m
Wing area: 21.65 sq.m / 233.04 sq ft
Frontal Area: 13.4 sq.ft.
Max take-off weight: 5488 kg / 12099 lb
Normal Gross Weight: 9450 lb
Empty weight: 3232 kg / 7125 lb
Wing Loading: 49.2 lbs/sq.ft.
Power Loading: 7.78 lbs/hp
Drop tank maximum capacity: 2 x 110 USG
Rear fuselage tank capacity : 85 USG
Maximum speed: 703 km/h / 437 mph at 25,000 ft
Speed @ Sea Level: 326 kts (375 mph, 603 kph)
Normal cruise: 240 kt at 65 USgph at 8000 ft
Cruise Speed @ 75% Power: 250 kts (300 mph, 483 kph)
Range normal: 950 sm,
Range max: 1710 sm
Service Ceiling: 12770 m / 41,900 ft.
Rate of Climb @ gross: 2800 ft/min
Climb to 30,000 ft / 9,145 m: 13 minutes 0 seconds
Vx (best angle of climb): 87 kts
Vy (best rate of climb): 148 kts
Va (design maneuvering): 226 kts
Vfe (max flaps extended): 143 kts
Vle (max landing gear extended): 148 kts
Vne (never exceed): 439 kts
Vsl (stall, clean): 92 kts
Vso (stall, in landing config.): 88 kts
Best Glide: 152 kts
Armament: Six .50-cal. machine guns / 2,000 lb external
Design Limit Load Factor: +8g / -4g @ 8000 lbs / +5.5g / -2.5g @ 11600 lbs.
Crew: 1
Cost: $54,000

 

P-51H
Engine: Packard Merlin V-1650-9
Max speed: 487 mph @ 25,000 ft

P-51J
Engine: Allison 119/F32, 1700 hp @ 20,700 ft
Max speed: 492 mph @ 27,400 ft.

F-6B
Engine: Allison, 1200 hp
Max speed: 390 mph.

Mustang 4
Engine: 1,520 h.p. Packard Merlin V1650-3
Span: 37 ft
Weight: 10,000 lb
Max. Speed: 445 mph

 

na-p51d-ld

North American P-51 Mustang

 

 


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