Subject: Number Forty-Nine in the Series--Lockheed XP-49

From: [email-masked]
Date: 5 Feb 93 19:31:44 GMT

>From [email-masked]

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 
turbosupercharged 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 turbosupercharged 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-engined 
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 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, the 
aircraft handled 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 inflight 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 inferior to the standard P-38J 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.  

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.  
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.  

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.  

Sources: 

  Lockheed Aircraft Since 1913, Rene J.  Francillon, Naval Institute 
  Press, 1988.  

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

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

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548