Τετάρτη, 21 Σεπτεμβρίου 2016

Late to the Party: The long range escort jet fighter of WWII


First flown on 25 February 1945, the first XP-83 proved underpowered and unstable. source
First flown on 25 February 1945, the first XP-83 proved underpowered and unstable. source
On 24 March 1944, with the war in Europe signalling the need for a long-range escort fighter and the P-51 Mustang not yet proven in this role, the USAAF tasked the builder of the first American jet aircraft to build a larger, longer-legged jet fighter. Bell assigned engineer Charles Rhodes to ‘bring along’ the bulky XP-83, powered by two 1633kg thrust General Electric 1-40  turbojets. The craft was to be armed with six 12.7mm Browning nose machine-guns.

The Bell XP-83 was a United States prototype escort fighter designed by Bell Aircraft duringWorld War II. It first flew in 1945. As an early jet fighter, its limitations included a lack of power and it was soon eclipsed by more advanced designs.
The early jet fighters consumed fuel at a prodigious rate, which severely limited their range and endurance. In March 1944, the United States Army Air Forces requested Bell to design a fighter with increased endurance, and formally awarded a contract for two prototypes on 31 July 1944.
Bell had been working on its “Model 40” interceptor design since 1943. It was redesigned as a long-range escort fighter, retaining the general layout of the P-59 Airacomet. The two General Electric J33-GE-5 turbojet engines were located in each wing root, which left the large and bulky fuselage free for fuel tanks and armament. The fuselage was an all-metalsemimonocoque, capable of carrying 1,150 gal (4,350 l) of fuel; in addition, two 250 gal  drop tanks could be carried. The cabin was pressurized, and the canopy a small and low bubble type. The armament was to be six 0.5 in (12.7 mm) machine guns in the nose.
The close proximity of the two low-slung powerplants caused hot exhaust gases to buckle the tail-plane unless, during run-ups, fire trucks were used to play streams of water over the rear fuselage. source
The close proximity of the two low-slung powerplants caused hot exhaust gases to buckle the tail-plane unless, during run-ups, fire trucks were used to play streams of water over the rear fuselage. source
Early wind tunnel reports had pinpointed directional instability but the “fix” of a larger tail would not be ready in time for flight testing.The first prototype was flown on 25 February 1945, by Bell’s chief test pilot Jack Woolams, who found it to be underpowered and unstable. The limited flight testing provided satisfactory flight characteristics although spins were restricted until the larger tailfin was installed. The second prototype did incorporate the extended tail and an aileron boost system. One unique characteristic was the XP-83’s refusal to “slow down” due to its sleek aerodynamic shape and lack of drag brakes; test pilots were forced to fly very long and flat landing approaches.
On 4 September 1947, just as this test programme had begun, a ramjet caught fire and flames spread to the wing. Pilot Chalmers 'Slick' Goodlin and engineer Charles Fay, without benefit of ejection seats, bailed out safely. The Bell XF-83, which never received a popular name, had made its last flight. source
On 4 September 1947, just as this test programme had begun, a ramjet caught fire and flames spread to the wing. Pilot Chalmers ‘Slick’ Goodlin and engineer Charles Fay, without benefit of ejection seats, bailed out safely. The Bell XF-83, which never received a popular name, had made its last flight. source
The first prototype was used in 1946 as a ramjet testbed, with an engineer’s station located in the fuselage behind the pilot and on 14 September 1946 one of the ramjets caught fire – the pilot “Slick” Goodlin and engineer Charles Fay had to parachute out. The second prototype flew on 19 October and was scrapped in 1947. Apart from range, the XP-83 was inferior to Lockheed’s P-80 Shooting Star, and the XP-83 project was canceled in 1947.
General characteristics
  • Crew: 1 pilot (engineer’s station fitted to first prototype, with an entrance door under the fuselage)
  • Length: 44 ft 10 in (13.67 m)
  • Wingspan: 53 ft 0 in (16.15 m)
  • Height: 15 ft 3 in (4.65 m)
  • Wing area: 431 sq ft (40.0 m²)
  • Empty weight: 14,105 lb (6,400 kg)
  • Loaded weight: 24,090 lb (10,930 kg)
  • Max. takeoff weight: 27,500 lb (12,500 kg)
  • Powerplant: 2 × General Electric J33-GE-5 turbojets, 4,000 lbf (18 kN) each
Performance
  • Maximum speed: 522 mph (453 kn, 840 km/h) at 15,660 ft (4,775 m)
  • Range:
    • Internal fuel: 1,730 mi (1,500 nmi, 2,785 km)
    • With drop tanks 2,050 mi (1,780 nmi, 3,300 km)
  • Service ceiling: 45,000 ft (14,000 m)
  • Rate of climb: 5,650 ft/min (28.7 m/s)
  • Time to altitude: 11.5 min to 30,000 ft (9,100 m)
  • Wing loading: 56 lb/sq ft (273 kg/m²)
  • Thrust/weight: 0.33
Armament
  • Guns:
    • 6 × .50 in (12.7 mm) M2 machine guns or
    • 6 × .60 in (15.2 mm) T17E3 machine guns (prototypes) or
    • 4 × 20 mm (0.79 in) Hispano cannons or
    • 1 × 37 mm (1.46 in) cannon in the nose

Δεν υπάρχουν σχόλια:

Δημοσίευση σχολίου