Although the Typhoon was basically a good design, Camm and his design team were disappointed with the wing which proved to be too thick in its cross section; this created problems with the airflow and inhibited the performance of the aircraft, especially at higher altitudes. In March 1940 a few engineers had been assigned to investigate the new low drag laminar flow wing that NACA in the United States had developed and which had been used in the new North American P-51 Mustang. The new laminar flow wing adopted for the Tempest series had a maximum thickness to chord ratio of 14.5% at the root tapering to 10% at the tip. By comparison the Typhoon's wing, using a NACA 4 digit series wing section, was substantially thicker - 19.5% (root) to 12% (tip). The maximum thickness of the Tempest wing was set further back at 37.5% of the chord versus 30% for the Typhoon's wing.
The wingspan was originally greater than that of the Typhoon at 43 ft (13.1 m), but the wingtips were later "clipped" and the wing became shorter; 41 ft (12.5 m) versus 41 ft 7 in (12.7 m). The wing planform was changed to an elliptical shape to accommodate the 800 rounds of ammunition for the four 20 mm (.79 in) Hispano cannons, which were moved back further into the wing. The new elliptical wing had greater area than the Typhoon's.
The thinner wing also displaced fuel tanks that had been fitted into the leading edge of the Typhoon's wing. This greatly reduced fuel capacity but Hawker engineers added a new 21 in (53 cm) bay ahead of the cockpit accommodating a 76 gal (345 l) fuel tank, giving a maximum of 360 gal (1,636 l) and an operational radius of 500 mi (805 km) Another important feature of the new wing for the Tempest I was Camm's proposal that radiators for the new Napier Sabre IV engine were to be fitted into the leading edge of the wing inboard of the undercarriage. This eliminated the distinctive "chin" radiator associated with the Typhoon and improved aerodynamics.
A further improvement of the Tempest wing over that of the Typhoon was the exceptional, flush riveted surface finish, essential on a high performance laminar flow airfoil. Fortunately for the pilots the new wing and airfoil, and the four-bladed propeller unit, eliminated the high frequency vibrations that had plagued the Typhoon.
The redesigned main undercarriage legs were longer and had a wider track (16 ft/5 m) to improve stability at the high landing speed of 110 mph (180 km/h), and to allow tip clearance for a new four-blade, 14 ft (4 m) diameter propeller. The main undercarriage units were designed to incorporate a system of trunnions which shortened the legs as they retracted. The main wheels also needed new thin tyres in order to fit within the wing. Finally, the retractable tailwheel was fully enclosed by small doors.
Camm and the Hawker design team placed a high priority on making their aircraft easily accessible to both air and ground crews; to this end the forward fuselage and cockpit areas of the earlier Hurricane and the Tempest and Typhoon families were covered by large removable panels providing access to as many components as possible, including flight controls and engine accessories. Both upper wingroots incorporated panels of non-slip coating. For the pilot a retractable foot stirrup under the starboard root trailing edge was linked to a pair of handholds which were covered by spring loaded flaps. Through a system of linkages, when the canopy was open the stirrup was lowered and the flaps opened, providing easy access to the cockpit. As the canopy was closed the stirrup was raised into the fuselage and the flaps snapped shut.
General characteristics
- Crew: One
- Length: 33 ft 8 in (10.26 m)
- Wingspan: 41 ft 0 in (12.49 m)
- Height: 16 ft 1 in (4.90 m (tail down))
- Wing area: 302 ft² (28 m²)
- Empty weight: 9,250 lb (4,195 kg)
- Loaded weight: 11,400 lb (5,176 kg)
- Max takeoff weight: 13,640 lb (6,190 kg)
- Powerplant: 1× Napier Sabre IIA or IIB or IIC liquid-cooled H-24 sleeve-valve engine:, 2,180 hp (1,625 kW) Sabre IIA
- Propellers: Four-bladed Rotol or de Havilland propeller
Performance
- Maximum speed: 432 mph (695 km/h) Sabre IIA at 18,400 ft (5,608 m), Sabre IIB 435 mph at 19,000 ft (700 km/h at 5,791 m)
- Range: 740 mi (1,190 km)
- 1,530 mi (2,462 km) with 90 gal (409 l) drop tanks
- Service ceiling: 36,500 ft (11,125 m)
- Rate of climb: 4,700 ft/min (23.9 m/s)
- Wing loading: 37.75 lb/ft² (184.86 kg/m²)
- Power/mass: 0.21 hp/lb (0.31 kW/kg)
Armament
- 4 × 20 mm (.79 in) Mark II Hispano cannons, 200 rpg
- 2 × 500 lb (227 kg) or 1,000 lb (454 kg) bombs
- 8 × 3 in (76.2 mm) RP-3 rockets
- 2 × 45 gal (205 l) or 2 × 90 gal (409 l) drop tanks.
** Hawker Tempest - Warbird Fare