Airspeed AS.57 Ambassador

The Airspeed Ambassador was an all-metal twin-engine airliner, designed to serve short-to-medium haul routes.

It was considered to be relatively advanced for the era, being a relatively aerodynamically clear aircraft with features such as a high aspect ratio wing with near-Laminar flow characteristics, a tricycle undercarriage, a steerable nose wheel, integral fuel tanks, and other recent innovations.

Distinctive external features of the Ambassador included its three low tailfins and a long pointed nose, it shared something of the character of the larger transcontinental Lockheed Constellation.

In a standard configuration, the Ambassador was could accommodate a maximum of 47 passengers, somewhat unusually, its passenger cabin could be either pressurised or not, dependent on the preference of the specific customer.

It was typically powered by conventional Bristol Centaurus radial engines, although individual aircraft were re-engine with various power plants, including turboprops.

In order to achieve a high level of efficiency while cruising, its designers made great efforts to minimize drag.

These included the use of a NACA laminar-flow wing section, although structural features for wing construction, propeller slipstream over the inner wing and increasing skin roughness with service were amongst several factors that reduced the optimistic NACA section’s performance when measured in a wind tunnel.

The engine nacelles were initially designed with inwardly-opening louvers for exhaust gases and cooling air rather than the usual outwardly opening “gills”.

However, these proved inadequate for cooling the engine, thus the gills were reinstated.

Engine-out climb performance was enhanced by being able to feather the propeller using a zero-torque signal from the engine.

Specifications

Crew

3

Capacity

Up to 60 passengers

Length

81 ft (25 m)

Wingspan

115 ft (35 m)

Height

18 ft 4 in (5.59 m)

Wing area

1,200 sq ft (110 m2)

Aspect ratio

11:1

Airfoil

Root-NACA

Tip-NACA

Empty weight

35,884 lb (16,277 kg)

Max take-off weight

52,000 lb (23,587 kg)

Fuel capacity

1,000 imp gal (1,200 US gal; 4,500 l) in two integral wing tanks, with provision for 600 imp gal (720 US gal; 2,700 l) in two centre-section bag tanks

Powerplant

2 × Bristol Centaurus 661 18-cylinder air-cooled sleeve-valve piston engines, 2,625 hp (1,957 kW) each

Performance

Maximum speed

312 mph (502 km/h, 271 kn) at 75% power with 11,650 lb (5,280 kg) payload

Cruise speed

300 mph (480 km/h, 260 kn) at 20,000 ft (6,100 m) at 50,000 lb (23,000 kg)

279 mph (242 kn; 449 km/h) at 60% power

Range

720 mi (1,160 km, 630 nmi) with 11,650 lb (5,280 kg) payload and no reserves at 280 mph (240 kn; 450 km/h)

900 mi (780 nmi; 1,400 km) at 220 mph (190 kn; 350 km/h)

1,560 mi (1,360 nmi; 2,510 km) with 7,900 lb (3,600 kg) payload max. fuel at 280 mph (240 kn; 450 km/h)

1,950 mi (1,690 nmi; 3,140 km) with 7,900 lb (3,600 kg) payload max. fuel at 220 mph (190 kn; 350 km/h)

Rate of climb

1,520 ft/min (7.7 m/s) at 5,000 ft (1,500 m) at maximum weight

Rate of climb on one engine

420 ft/min (130 m/min) after take-off at maximum weight

360 ft/min (110 m/min) at 5,000 ft (1,500 m) at maximum weight

Wing loading

43.3 lb/sq ft (211 kg/m2) at 52,000 lb (24,000 kg)

Power/mass

0.1 hp/lb (0.16 kW/kg) at 52,000 lb (24,000 kg)

Take-off distance to 50 ft (15 m)

3,270 ft (1,000 m) at maximum T.O weight

Take-off distance to 50 ft (15 m) one engine

4,950 ft (1,510 m) at maximum T.O weight

Landing distance from 50 ft (15 m)

2,565 ft (782 m) at max landing weight.

 

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