Curtiss XP-71

Curtiss XP-71 was a 1940 proposal of a heavy escort fighter aircraft for USAAF.  It was equipped with a pressurized cockpit and equipped with two Pratt and Whittney Wasp Mayor radial engines.  It featuring the pusher configuration with 8 countra rotating propellers. Based on the experience of heavy fighter, these type of aircrafts were requested as escort for bombers.  Two prototypes were ordered.  The development were equipped with Wasp Mayor turbocharged radial engines was supposed to be the biggest aircraft during the war
The final design of the XP-71 was bigger than the B-25 Mitchell medium bomber so this complex aircraft was considered to be need a lot of resources to built.  A mock up was built to gained data for the prototypes but later, the requirement of more advanced fighters such as jets led to the cancellation of the XP-71 project and the prototype was never built in 1942.
Specification
General characteristics

• Crew: 2
• Length: 61.83 ft (18.85 m)
• Wingspan: 82.25 ft (25.07 m)
• Height: 19.0 ft (5.79 m)
• Wing area: 602 ft² (55.9 m²)
• Empty weight: 31,060 lb (14,090 kg)
• Max takeoff weight: 46,950 lb (21,295 kg)
• Powerplant: 2× Pratt & Whitney R-4360-13 "Wasp Major" radial engines, 3,450 hp (2,574 kW) each

Performance

• Maximum speed: 428 mph (371 knots, 690 km/h) at 25,000 ft (7,620 m)
• Range: 3,000 mi (2,600 nm, 4,800 km)
• Service ceiling: 40,000 ft (12,192 m)
• Max wing loading: 51.6 lb/ft² (252 kg/m²)
• Minimum power/mass: 0.147 hp/lb (242 W/kg)
• Time to altitude: 12.5 min to 25,000 ft (7,620 m)

Armament

• Guns:
  
  
  
  • 1× 75 mm (2.95 in) cannon
  • 2× 37 mm (1.46 in) cannon

References: http://www.secretprojects.co.uk/forum/index.php/topic,3281.0.html
                    http://en.wikipedia.org/wiki/Curtiss_XP-71