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The Lockheed XP-49, its designation seemingly out of sequence in that it was a conception of pre-war years, was designed in 1939 with the ambitious goal of attaining 761km/h in level flight at 4572m. The XP-49 would have been a veritable flying arsenal in its day as it was to be armed with two 20mm cannon and four 12.7mm machine-guns. It was rigorously and exhaustively tested at Burbank, California, and Wright Field, Ohio, and the XP-49 was denied production status because of an engine substitution and the appearance of the Thunderbolt and Mustang.

The XP-49 was an outgrowth of the P-38 Lightning but in most respects was an entirely new design by the Lockheed-Burbank fighter team under H. L. Hibbard and Clarence (Kelly) Johnson. Ordered by the US Army on 3 August 1939 to meet a twin-engine fighter requirement (which also produced the Grumman XP-50) the sole XP-49 was expected to attain unprecedented performance by mating the Lightning's familiar twin-boom layout with two 1715kW Pratt & Whitney X-1800 24-cylinder inline engines.

When plans to develop the powerplant proved too ambitious, twin 1006kW Continental XIV-1430-1 engines had to be substituted, reducing speed to a still-impressive 737km/h, although this was reached because the test ship lacked the added weight of protective armour which would have been fitted on a production variant. "We still felt we had a winner," says a Lockheed engineer. "We had a roomy, pressurised cabin, good handling characteristics and, eventually, good manoeuvrability." US Army planners saw the XP-49 as a possible 'convoy fighter' able to escort bombers on deep penetration raids. It might have been accorded higher priority had England been lost as a base from which to mount the air assault on the Third Reich.

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Wright Field in October 1945

The XP-49 first flew 11 November 1942 at Burbank. When it became necessary to increase the vertical fin area to improve yaw characteristics, the result was an unusual set of markings: Army directives called for 13 alternating red and white horizontal stripes on the rudder, symbolic of the original 13 American colonies. When the tail was heightened, painters simply added non-regulation extra stripes.

At Burbank, the XP-49 survived a crash-landing caused by hydraulic failure, was repaired, and was ferried to Wright Field, Ohio, on 25 June 1943. Though it was a clear improvement over the P-38, able to "fly rings around the Lightning" in the words of one pilot, minor but troublesome fuel leakage problems led to XP-49 tests being discontinued and the airframe being scrapped, just when Mustangs with long-range drop tanks were appearing over Berlin. The 'convoy fighter' concept was studied later with the Lockheed XP-58 but never produced an operational aircraft.

 

 

The XP-49

 

 

In the spring of 1939, the Air Corps issued a request for an advanced twin-engine interceptor, to be derived from an existing type and fitted with advanced high-performance engines. Lockheed responded to the request with the "Model 222", which was much like a P-38 except that it had a pressurized cabin and was to be powered by 24-cylinder inline Pratt & Whitney X-1800-SA2-G engines, which were in development and were expected to provide over 1,490 kW (2,000 HP). The Model 222 was to be armed with four 12.7 millimeter and two 20 millimeter guns, and a P-38G was modified to test this armament fit.

The Model 222 won the competition, with the Air Corps ordering a single prototype as the "XP-49" in October 1939. Lockheed proposed that production P-49s be fitted with turbocharged Wright R-2160 Tornado radials with 1,715 kW (2,300 HP) each, which would give the P-49 an estimated performance of 800 KPH (500 MPH) at altitude.

Work on the XP-49 went slowly as Lockheed was caught up in the prewar US military buildup. As development work plodded along, both the Air Corps and Lockheed began to have doubts for various reasons about the powerful engines to be fitted to the aircraft, and so the design was changed to incorporate two Continental XIV-1430-9/11 12-cylinder inverted-vee engines with 1,150 kW (1,540 HP) each for takeoff.

Engine availability further delayed development of the aircraft, and the XP-49 didn't take to the air until April 1942. The XP-49 looked much like a P-38, except for increased length and longer nacelles, and in fact the two aircraft shared about two-thirds of their parts. The aircraft was evaluated into the summer of 1943, but the Continental engines were troublesome.

   LOCKHEED XP-49:
   _____________________   _______________________
 
   spec                    english
   _____________________   _______________________

   wingspan                52 feet
   wing area               327.5 sq_feet
   length                  40 feet 1 inch
   height                  9 feet 10 inches

   empty weight            15,475 pounds
   max takeoff weight      18,750 pounds

   maximum speed           458 MPH / 398 KT
   service ceiling         40,000 feet
   range                   800 MI / 649 NMI
   _____________________   _______________________

Some sources claim that the XP-49 had few if any performance advantages over existing P-38 production, others cite a test pilot as saying it "fly rings around the Lightning", but whatever the case the USAAF abandoned all plans to put the XP-49 into production. The single prototype was used for occasional tests, including being dropped from a crane to simulate hard landings, and was finally scrapped in 1946.

 

 

 

Click on Picture to enlarge

Lockheed XP-49

The XP-49, Lockheed Model 222, was developed as a possible successor to the P-38 and won a design competition in August 1939. The aircraft was originally designed for Pratt & Whitney X-1800 engines (24 cylinders and 2,300 hp. each), but after development problems with these engines, Continental "Hyper" engines were substituted requiring lengthened nacelles to re-balance the aircraft for the lighter XI-1430's.

The XP-49 first flew on 11 November 1942. Flight testing revealed undersized vertical stabilizers which were then enlarged to increase stability. (XP-49 trivia: the rudders were not repainted after the modification; two more stripes were added to fill the space--15 instead of the standard 13). The XP-49 wasn't significantly better than the P-38 and never entered production.

TYPE XP-49

Number built/Converted 1

Remarks Improved P-38 (S/N 40-3055)

SPECIFICATIONS
Span: 52 ft. 0 in.
Length: 40 ft. 1 in.
Height: 9 ft. 9.5 in.
Weight: 15,475 lbs. empty/18,750 lbs. gross
Armament: designed for two 20mm cannon and 4 .50-cal. machine guns although no armament was actually installed on the aircraft.
Engines: 2 Continental XI-1430-1 of 1,600 hp.

PERFORMANCE
Maximum speed: 406 mph. at 15,000 ft.

 

Click on Picture to enlarge

The XP-49

The Lockheed XP-49, its designation seemingly out of sequence in that it was a conception of pre-war years, was designed in 1939 with the ambitious goal of attaining 761km/h in level flight at 4572m. The XP-49 would have been a veritable flying arsenal in its day as it was to be armed with two 20mm cannon and four 12.7mm machine-guns. It was rigorously and exhaustively tested at Burbank, California, and Wright Field, Ohio, and the XP-49 was denied production status because of an engine substitution and the appearance of the Thunderbolt and Mustang.

The XP-49 was an outgrowth of the P-38 Lightning but in most respects was an entirely new design by the Lockheed-Burbank fighter team under H. L. Hibbard and Clarence (Kelly) Johnson. Ordered by the US Army on 3 August 1939 to meet a twin-engine fighter requirement (which also produced the Grumman XP-50) the sole XP-49 was expected to attain unprecedented performance by mating the Lightning's familiar twin-boom layout with two 1715kW Pratt & Whitney X-1800 24-cylinder inline engines.

When plans to develop the powerplant proved too ambitious, twin 1006kW Continental XIV-1430-1 engines had to be substituted, reducing speed to a still-impressive 737km/h, although this was reached because the test ship lacked the added weight of protective armour which would have been fitted on a production variant. "We still felt we had a winner," says a Lockheed engineer. "We had a roomy, pressurised cabin, good handling characteristics and, eventually, good manoeuvrability." US Army planners saw the XP-49 as a possible 'convoy fighter' able to escort bombers on deep penetration raids. It might have been accorded higher priority had England been lost as a base from which to mount the air assault on the Third Reich.

The XP-49 first flew 11 November 1942 at Burbank. When it became necessary to increase the vertical fin area to improve yaw characteristics, the result was an unusual set of markings: Army directives called for 13 alternating red and white horizontal stripes on the rudder, symbolic of the original 13 American colonies. When the tail was heightened, painters simply added non-regulation extra stripes.

At Burbank, the XP-49 survived a crash-landing caused by hydraulic failure, was repaired, and was ferried to Wright Field, Ohio, on 25 June 1943. Though it was a clear improvement over the P-38, able to "fly rings around the Lightning" in the words of one pilot, minor but troublesome fuel leakage problems led to XP-49 tests being discontinued and the airframe being scrapped, just when Mustangs with long-range drop tanks were appearing over Berlin. The 'convoy fighter' concept was studied later with the Lockheed XP-58 but never produced an operational aircraft.

 

 

The Continental I-1430-9 "Hyper" Engine

 

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Continental I-1430-9

 The development of the liquid-cooled Continental "Hyper" high horsepower engine began in 1932. It featured cylinders with "spherical" combustion chambers and sodium cooled exhaust valves. An upright V-12 engine was planned, but emphasis was later changed to an inverted V-12 engine for pursuit planes. Continental built the inverted V engine in 1938 and successfully tested it in 1939. In 1943, the 1,600 hp. IV-1430 engine, later re-designated the XI-1430, was tested extensively in the Lockheed XP-49, a modified version of the P-38 "Lightning." In 1944 it was also tested in the McDonnell XP-67. Only 23 I-1430 series engines were delivered. Although more powerful and lighter than the nearest competitor, the engine was not produced because tooling capacity for large scale production was not available.

SPECIFICATIONS:
Model: Continental I-1430 "Hyper"
Type: 12 cylinder, liquid-cooled, inverted V
Displacement: 1,430 cu. in.
Horsepower: 1,600
RPM: 3,200
Weight (dry): 1,615 lbs.

The Continental I-1430 Engine

 

 

The Lockheed XP-49

By  Joe Baugher

 

Click on Picture to enlarge

Lockheed XP-49

On March 11, 1939, the USAAC Materiel Division issued Circular Proposal 39-775 to the aircraft industry. This proposal called for a new type of twin-engined, high-performance interceptor fighter. The successful entry was, however, to derive as many design features as possible from already existing aircraft.

Four contractors submitted proposals. The Lockheed entry was a progressive development of the P-38 Lightning, and was given the company designation of Model 222. The Model 222 had the same general arrangement as the P-38, but featured a pressure cabin and was powered by a pair of turbo-supercharged twenty-four cylinder Pratt & Whitney X-1800-SA2-G (military designation XH-2600) liquid-cooled engines which were supposed to develop somewhere between 2000 and 2200 horsepower. Lockheed proposed to replace these engines by a pair of 2300 hp Wright R-2160 Tornado turbo-supercharged radials in production aircraft. Armament was to be a pair of 20-mm cannon and four 0.50-inch machine guns. Total fuel capacity was to be 300 US gallons, as compared to 230 US gallons for the early production P-38. The Model 222 was rather optimistically estimated to have a top speed of 473 mph at 20,000 feet when powered by the Pratt & Whitney XH-2600s, and a speed of no less than 500 mph at the same altitude when powered by the Wright Tornadoes.

The USAAC finished looking over the four proposals on August 3, 1939. The Lockheed proposal (which by this time had had its company designation changed to Model 522) was judged the most promising of the four entries, and the USAAC ordered one example under the designation XP-49 in October 1939. The competing Grumman entry was their Design 41, which was a development of the XF5F-1 Skyrocket twin-engine carrier-based fighter. The Grumman design came in second, but the USAAC considered it sufficiently promising that they ordered one example under the designation XP-50.

A contract for a single XP-49 prototype was officially issued on January 8, 1940. Because the Lockheed company was preoccupied with the P-38 Lightning, work on the XP-49 proceeded quite slowly during the early months of 1940. Both the USAAC and Lockheed soon came to realize that with either the Pratt & Whitney XH-2600 or the Wright R-2160 engines, the XP-49 would be seriously overpowered. Consequently, in March 1940 it was decided to substitute a pair of experimental Continental XIV-1430-9/11 twelve-cylinder inverted-vee liquid-cooled engines rated at 1540 hp for takeoff. In order to counteract torque, the engines rotated in opposite directions--the port propeller rotated CCW when viewed from the rear, and the starboard propeller rotated CW. Other changes included the substitution of dummy armor plate for the genuine armor plate called for in the original specification, thus expediting construction of the prototype. A maximum speed of 458 mph at 25,000 feet was now anticipated.

On December 23, 1940 , detailed design of the XP-49 began under the direction of project engineer M. Carl Haddon. Two-thirds of the XP-49 airframe components were common with the P-38. The primary differences were in the engine installation, the use of a heavier and stronger undercarriage, and a pressurized cockpit similar to that of the XP-38A.

Since much of the airframe was common with the production P-38, the construction of the XP-49 prototype (serial number 40-3055) went fairly rapidly. However, the first flight was delayed by problems with the experimental Continental engines, which were not yet cleared for flight operations at the time they were delivered to Lockheed in April 1942. It was not until November 14, 1942 that the XP-49 took to the air for the first time, flown by test pilot Joe Towle.

The aircraft was grounded only a week later for replacement of the engines by XIV-1430-13/15 engines rated at 1350 hp for takeoff and 1600 hp at 25,000 feet. The fuel tanks were replaced by self-sealing tanks taken from a P-38, and a flight engineer's jump seat was added behind the pilot's seat. Flights were resumed in December, but were marred by continual hydraulic problems. When it was actually able to fly at all, the aircraft handled fairly well and had good maneuverability, but the Continental engines gave the XP-49 a rather uninspiring performance--the maximum speed was only 406 mph at 15,000 feet as against a promised speed of 458 mph at 25,000 feet.

On January 1, 1943, the XP-49 was damaged during an emergency landing at Muroc AAB after a simultaneous in-flight failure of both the hydraulic and the electrical systems. While being repaired, the XP-49 received 7 3/4 inch taller vertical tail surfaces. The XP-49 flew again on February 16, 1943. In this form, it was delivered to Wright Field on June 26, 1943, almost 27 months later than expected. By that time, the Army had lost all interest in the XP-49, since the performance was actually inferior to that of the standard P-38J which was already in service. In addition, the questionable future of the troublesome Continental engine caused the Army to abandon any further consideration of quantity production of the XP-49.

Even after the USAAF had decided not to proceed with quantity production of the XP-49, the Army continued testing the aircraft at Wright Field. However, maintenance difficulties with the Continental engines and problems with the fuel system limited the usefulness of the XP-49, and it was flown only rarely. It ended its useful life by being dropped from a bridge crane to simulate hard landings. It was finally scrapped in 1946.

Performance of the XP-49 included a maximum speed of 406 mph at 15,000 feet, 384 mph at 10,000 feet, and 347 mph at sea level. Initial climb rate was 3300 feet per minute, and the XP-49 could climb to 20,000 feet in 8.7 minutes. Normal range was 679 miles, and maximum range was 1800 miles. Service ceiling was 37,500 feet. Weights were 15,410 pounds empty and 18,750 pounds loaded. Wingspan was 52 feet 0 inches, length was 40 feet 1 inch, height was 9 feet 9 1/2 inches (original tail), 10 feet 5 1/4 inches (revised tail), and wing area was 327.5 square feet. The proposed armament of 2 20-mm cannon with 670 rpg and four 0.50-inch machine guns with 300 rpg was never actually fitted.

Sources:

1. Lockheed Aircraft Since 1913, Rene J. Francillon, Naval Institute Press, 1988.
    
2. War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday, 1964.
    
3. The American Fighter, Enzo Angelucci and Peter M. Bowers, Orion, 1987.

By  Joe Baugher

 

The XP-49

 

The XP-49 was a development of the Lockheed Corporation and a possible replacement for its successful line of P-38 Lightning aircraft. The XP-49 was to be a high-altitude performer with the capabilities of a well-designed fighter stemming from a fine pedigree in the Lightning series itself.

The United States Army was increasingly concerned with ballooning costs of Lockheed's latest P-38 model and put forth a new developmental contract to survey similarly performing aircraft from a variety of contractors. After review of several of the proposed entries, the Army settled on the new Lockheed design, itself intended to replace the still active P-38 series. This Model 522 aircraft designation was then changed to the developmental platform marked as XP-49.

The XP-49 was very similar in visual appearance to the P-38. The twin-boom design was found to be quite an effective performer for the P-38 series since its introduction and the XP-49 would follow suit. Despite these similarities, the XP-49 was, in fact, an entirely new design and engineering feat put about by Lockheed. The system was also to be featured with Pratt & Whitney's ultra-new X-1800 engines capable of an impressive 2,300 horsepower which would have propelled the XP-49 to speeds nearing 500 miles per hour.

The single prototype was completed and first flown in November of 1942, sans all guns to promote expediency in the development of the general airframe. The weapon systems were to be comprised of twin 20mm cannons and 4 x .50 caliber heavy machine guns - quite the potent combination considering the P-38 was armed with just a single 20mm cannon and 4 x .50 caliber gun array. Initially a single seat fighter, an observation seating area was later added aft. A cancellation was then put forth on any further development of the Pratt & Whitney engines in favor of the Continental brand powerplants designated as XI-1430, dropping the promoted top speed of the XP-49 by a massive 75 miles per hour. The XP-49's days were numbered from then on.

The system led a very brief testing life before running into further powerplant issues with its new Continentals leading to their cancellation. An unplanned crash landing also took place during testing when a landing gear failed to extend - such was the life of the XP-49. With the cancellation of the powerplants, the US Army looked to other avenues as the war progressed, effectively leaving the XP-49 project dead on the runway.

In its final vision of glory, the remaining XP-49 airframe was subjected to brutish testing by being dropped at heights against a concrete flooring. These tests were conducted to see the extent of damage caused by G-forces on the fuselage. The XP-49 remains were later paraded in limited display and ultimately cannibalized and scrapped.

 

 

 

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