Airspeed Ambassador

https://en.wikipedia.org/wiki/Airspeed_Ambassador

The Airspeed AS.57 Ambassador is a British twin piston-engined airliner that
first flew on 10 July 1947 and served in small numbers through the 1950s and
1960s. The planes are sometimes referred to as "Elizabethans", as they were
originally ordered and popularised by British European Airways as the planes
used for their "Elizabethan Class" passenger service.

The Ambassador had its origin in 1943 as a requirement identified by the
Brabazon Committee for a twin-engined short-to-medium-haul replacement for the
Douglas DC-3. Airspeed Ltd. was asked to prepare an unpressurised design in the
14.5-ton gross weight class, using two Bristol Hercules radial engines. In 1943,
the company duly set up a dispersed design office in Fairmile Manor at Cobham in
Surrey.

By the time the British Ministry of Aircraft Production ordered two prototypes
from Airspeed, immediately after the end of the Second World War, the design had
grown substantially. The Ambassador would be pressurised, have more powerful
Bristol Centaurus radials and have a maximum gross weight of almost 24 tons.

The revised design offered seating for 47 passengers and, having a tricycle
undercarriage, looked more modern than the DC-3s, Curtiss Commandos, Avro
Lancastrians and Vickers Vikings that were common on Europe's shorter airline
routes. With three low tailfins and a long pointed nose, it shared something of
the character of the larger transcontinental Lockheed Constellation.

Great efforts were made to reduce drag, to improve performance and cruising
efficiency. A NACA laminar-flow wing section was chosen to reduce drag although
structural features for wing construction, propeller slipstream over the inner
wing and increasing skin roughness with service were some of the things which
reduced the optimistic NACA section performance measured in a wind-tunnel. The
engine nacelles were first designed with inwardly opening louvres for exhaust
gases and cooling air rather than the usual outwardly opening "gills". However,
these proved inadequate to cool the engine, so 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.


Role
Airliner

Manufacturer
Airspeed Ltd

First flight
10 July 1947

Introduction
1951

Primary user
British European Airways

Produced
1947–1953

Number built
23

British European Airways (BEA) placed a £3 million order for 20 aircraft in
September 1948, and operated them between 1952 and 1958, calling them their
"Elizabethan Class" in honour of the newly crowned Queen. The flagship of the
fleet was G-ALZN, appropriately named "RMA Elizabethan". The first "Elizabethan"
scheduled flight was from Heathrow to Paris Le Bourget on 13 March 1952 and the
type later also served the key UK routes. By December 1955 the "Elizabethan
Class" had reached 2,230 flying hours annually, per aircraft, the highest in
BEA's fleet. However, the last Elizabethan scheduled service for BEA was
operated in August 1958, and the type was replaced by the Vickers Viscount.

The popularity of this aircraft, with its pressurised cabin and good
soundproofing, was soon eclipsed by the arrival of turboprop-powered aircraft
such as the Vickers Viscount and, some years later, the Lockheed Electra, which
featured more reliable engines and faster speeds. The coming of turboprops and
the dawning of the Jet Age caused the Ambassador to fall out of favour.

Specifications

General characteristics
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
Empty weight: 35,884 lb (16,277 kg)
Max takeoff 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
enigines, 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% powerRange: 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 weightWing 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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