Wikipedia

Airspeed Ambassador

TheAirspeed AS.57 Ambassadoris a British twinpiston-enginedairlinerthat was designed and produced by the British aircraft manufacturerAirspeed Ltd.It was one of the firstpostwarairliners to be produced.

AS.57 Ambassador
Dan-Air Ambassador atBristol Airportin 1965
General information
TypeAirliner
ManufacturerAirspeed Ltd
StatusRetired
Primary userBritish European Airways
Number built23[1]
History
Manufactured1947–1953
Introduction date1951
First flight10 July 1947

The Ambassador was developed in response to a requirement identified by theBrabazon Committeefor a twin-engined short-to-medium-haul airliner as a replacement for the ubiquitousDouglas DC-3.Airspeed assembled a dispersed design team at Fairmile Manor, Cobham, Surrey, in 1943, which initially worked on a smaller proposal powered byBristol Herculesradial engines;this was quickly superseded by a larger-capacity design aimed at better fulfilling the expansion in postwar civil air travel, although several entities doubted Airspeed's projected growth in air travel. Fitted with the new but conventionalBristol Centaurusradial engines,the Ambassador was designed to accommodate fourNapier Nomadturbo-compound engines,a then-recent innovation. Its fuselage was compatible withpressurisation,this being an optional feature offered to customers.

On 10 July 1947, the first prototype Ambassador conducted itsmaiden flightat Christchurch with chief test pilot George Errington at the controls; a total of three prototypes were built. Early on,British European Airways(BEA) emerged as a key customer for the type, having placed a £3 million order for 20 aircraft in September 1948. Introducing the Ambassador to service in 1951, BEA often referred to the aircraft as the "Elizabethans", as the aircraft were used for the airline's "Elizabethan Class" passenger service. However, the type was quickly outperformed by the turboprop-poweredVickers Viscount,with BEA opting to withdraw its Ambassadors in 1958.

Secondhand aircraft were operated by several other airlines, includingDan-AirandNortheast Airlines.Despite being produced in relatively small numbers, the Ambassador was operational for longer than had been anticipated by planners.[1]

Development

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Background

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The origins of the Ambassador can be traced to 1943 and the work of theBrabazon Committee,which sought to define what types of aircraft would be desired by thepostwarcivil aviation sector. One of the committee's recommendations was a twin-engined short-to-medium-haul replacement for theDouglas DC-3,known as theType 2.[2]The British manufacturerAirspeed Ltd.was interested in this requirement and established a small design team to work on the project from a dispersed office in Fairmile Manor atCobhamin Surrey in 1943. This effort was headed by ex-de Havillandaeronautical engineerArthur Hagg, who had joined the company earlier that year.[1]

Early concepts included anunpressurisedaircraft in the 14.5-tongross weight class to be powered by a pair ofBristol Herculesradial engines.[3]Work on the endeavour was taken as far as possible without impacting Airspeed's wartime production activity, as theSecond World Warwas still raging.[4]In response to changes in planner's preferences, dictating that the interim aircraft be procured so that airliners such as the in-development Ambassador had more development time, thus the design was revised substantially to expand its capacity. By 1944, it was a considerably larger design than the DC-3, with improved comfort and space.[5]

While Airspeed's management believed that postwar demands would demand greater passenger capacities, several figures, including those within theBritish Overseas Airways Corporation(BOAC) and theAir Ministry,were less enthusiastic with their projections.[6]The company also promoted the economics of higher utilisation rates and elevated cruise speeds, whereas conventional wisdom amongst airlines was to avoid increasing speeds to reduce fuel consumption. For the Ambassador, Airspeed opted to pursue a cruising altitude of 20,000 ft, relatively high for the era.[7]A comprehensive mockup was completed by November 1944, largely for promotional purposes, while the projected operating cost figures were released during early 1945.[7]

Immediately following the end of the conflict, the BritishMinistry of Aircraft Productionplaced an order with the company to produce a pair ofprototypes.[8]While the first prototype was to be unpressurisedand powered by a pair ofBristol Centaurusradial engines,it was envisioned that the second prototype would feature a reinforced fuselage compatible with pressurisation and a wing that could accommodate fourNapier Nomadturbopropengines. Several officials, including company chairmanAlan Samuel Butler,favored the adoption of the new turbopropeller engines.[8][2]By the end of 1945, work had commenced on building structural test sections andjigs.[7]

Into flight

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On 10 July 1947, the first prototype,registeredG-AGUA,conducted the type'smaiden flight,flown by chief test pilot George B.S. Errington.[8]After the generally successful first flight, the prototype underwent a month of alterations, including deleting the spring tab and replacing it with gearedtabsfitted to the outer rudders and locking the inner rudder;reversible propellerswere also installed. During September 1947, the prototype made its first public display alongside elements of the second prototype, including its cockpit and control system, at theSociety of British Aircraft Constructors(SBAC) show atRadlett.[9]

On 22 November 1947, the programme received a setback when the prototype was forced to perform abelly landingafter the portundercarriageleg failed to deploy due to a loss ofhydraulicpressure.[9]This did not seemingly deter customer confidence, as the newly created operatorBritish European Airways(BEA) continued to openly express their preference for the type, and in September they placed a £3 million order for 20 Ambassadors.[10][11]This support was so impactful that, according to aviation author H. A. Taylor, rival aircraft manufacturerVickerswas close to cancelling development of theViscountover fears that airlines held a preference for advanced piston-powered airliners over the unfamiliar turboprop.[12]

During flight testing, it was found that the aircraft possessed particularly favourable low speed characteristics.[13]Having been explored in depth beforehand, this was dramatically displayed at the 1948Farnborough Airshow,becoming the only aircraft in history to perform such an aerial display with one engine out throughout. This was a deliberate choice, with the inactive engine's propeller beingfeatheredprior to taking off and remaining so until after landing.[14]The first prototype performed the majority of flight testing through late 1948.[15]

A total of three prototypes were constructed for the test programme.[10]The second Ambassador,G-AKRD,[16]was the first to feature pressurisation and was equipped with a full passenger cabin configuration for demonstration flights.[14]This second prototype was subsequently used by theBristol Aeroplane Companyfrom 1953 for flight-testing theBristol Proteus705 turbine engine. From March 1958, it was used byRolls-Roycefor testing theDartandTyneturboprops.[2][17]The third prototype and first Ambassador 2G-ALFRwas initially used for BEA proving trials,[16]and in 1955 it also supported the development trials of theNapier Elandturbine engine. During 1958, intensive simulated airline flying, to pave the way for BEA Vanguards, was performed using two Tyne-powered Ambassadors.[18][19]

During the latter stage of development, some issues were uncovered.[11]The wing, which had been designed to inducelaminar flowcharacteristics, was relatively unconventional in its design; testing revealed that it lacked sufficient strength, and redesigning the wing was not straightforward. Technical assistance was provided byde Havillandand the issue was proven to be resolved in December 1949.[11]Three minor accidents during demonstration flights, while causing no serious damage, often delayed testing and did not inspire confidence amongst potential customers.[20]Quantity production of the Ambassador commenced during 1950, leading to the first production standard aircraft, destined for BEA, performing its first flight on 12 January 1951.[21]

Design

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The Airspeed Ambassador was an all-metal twin-engine airliner, designed to serve short-to-medium haul routes.[22]It was relatively advanced for the era, being relatively aerodynamically clean, having ahigh aspect–ratio wingwith hoped-for near-Laminar flowcharacteristics, atricycle undercarriage,a steerable nosewheel, integral fuel tanks, and other recent innovations.[13]Distinctive external features of the Ambassador included its three lowtailfinsand a long pointed nose, giving it a resemblance to the larger transcontinentalLockheed Constellation.Its tricycle gear gave it a more modern appearance than contemporaries such as theDC-3,Curtiss Commando,Avro LancastrianandVickers Vikingsthat were common on Europe's shorter airline routes.

In a standard configuration, the Ambassador could accommodate up to 47 passengers; somewhat unusually, its passenger cabin could be eitherpressurisedor not as the customer preferred.[22]To reduce cabin noise levels, considerable effort went intosoundproofingand general furnishings; Taylor described the Ambassador as being particularly quiet for a piston engine airliner, although also noting it could not equal the lower noise levels ofturboprop-powered airliners such as theVickers Viscount.[23]It was typically powered by conventionalBristol Centaurusradial engines,although individual aircraft were reengined with various powerplants, including turboprops.[17]

To increase cruise performance, designers made great efforts to minimisedrag,using aNACAlaminar-flow wing section. The predicted low-drag performance was not completely realized, however, due to structural features for wing construction, propeller slipstream over the inner wing, and increased skin roughness in actual service conditions. The enginenacelleswere initially designed with inwardly-openinglouvresfor 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 tofeatherthe propeller using a zero-torque signal from the engine.[24]

Operational history

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During 1952,British European Airways(BEA) introduced the first of its 20 strong fleet of Ambassadors to revenue service, the airline referred to them as the "Elizabethan Class" in honour of the newly crownedQueen Elizabeth II.[10]The planned 1951 introduction date had been pushed to 1952 to address development issues.[11]By May 1951, intense proving trials of the Ambassador were being conducted by a joint team of Airspeed and BEA employees, while official BEA training commenced in August of that year.[21]The flagship of BEA's fleet wasG-ALZN,appropriately named "RMA Elizabethan".[25]The first "Elizabethan" scheduled flight was fromHeathrow AirporttoParis Le Bourgeton 13 March 1952, soon the type was used across BEA's mainUKroutes.[26]

According to Taylor, the Ambassador's performance gave BEA a competitive edge over its rivals.[26]By December 1955, the "Elizabethan Class" had reached 2,230 flying hours annually, per aircraft, the highest in BEA's fleet. However, the rivalVickers Viscount,which was introduced in 1953, was even more popular with BEA's passengers than the Ambassador.[26]Rival airlines, such asAir France,had also quickly introduced the Viscount, and thus held an advantage over BEA's Elizabethan service. Accordingly, the airline decided to withdraw the type despite its relative youth, with BEA's final scheduled Ambassador flight on 30 July 1958.[26]

There were no further sales of the Ambassador. Aviation authorsBill GunstonandPeter Masefieldlaid this lack of success largely upon attitudes withinde Havilland's management following its takeover of Airspeed in 1951; they allegedly preferred to use Airspeed's factory atChristchurch Airfieldto produce military jets designed by de Havilland.[27]One example of de Havilland's undermining of potential sales was the recall of the Sales Director to de Havilland's headquarters atHatfield Aerodrome(Hertfordshire,England) from Australia, despite his reportedly being near to finalizing an order fromTrans-Australia Airlinesfor 12 Ambassadors.[28]Taylor observed that prospective customers were often sceptical that Airspeed, being a relatively small company, could be relied upon for technical support and components.[29]

Napier's Eland engine test-bed AmbassadorG-ALFRat Farnborough SBAC Show 1955

Following the type's disposal by BEA, secondhand Ambassadors helped to establish the scheduled and charter flight operations ofDan-Air,an important airline in the development of thepackage holiday.The type was also used in the UK byAutairandBKS Air Transport.Secondhand Ambassadors were also flown for short periods by other airlines including Butler Air Transport (Australia), Globe Air (Switzerland) andNorrønafly(Norway).[30][31]Multiple entities, such asRoyal Dutch Shelland theRoyal Jordanian Air Force,also procured Ambassadors for private purposes.[32]

Passengers board a British European Airways G-AMAH Airspeed Ambassador aircraft in 1954.

The initial popularity of the Ambassador, with its pressurised cabin and goodsoundproofing,was soon eclipsed by the arrival ofturboprop-powered aircraft such as theVickers Viscountand, some years later, theLockheed Electra,which featured more reliable engines and faster speeds.

Variants

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BKS Air TransportAmbassadorG-AMADin 1965
AS.57 Ambassador 1
Prototype aircraft withBristol Centaurus130 engines, two built.[33]
AS.57 Ambassador 2
Production version with Bristol Centaurus 661 engines, 21 built including the production prototype.[34]

Projects

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AS.59 Ambassador II
Project for either a twin-engined variant withBristol ProteusorBristol Theseusengines or a four-engined variant withNapier NaiadsorRolls-Royce Darts.[35]From the first prototypes, the Ambassador's wing had been stressed for four Naiad turboprops, but no four-engined variant flew.[36]
AS.60 Ayrshire C.1
Proposed variant to meetAir Ministry Specification C.13/45for a medium-range military transport with a rear-fuselage loading ramp.[35]Ten were ordered in October 1946 but were not built, after a review of the design's projected performance produced figures lower than the Air Ministry's requirements.[37]
AS.64
Proposed military transport variant for theRoyal Air Forceto meetAir Ministry Specification C.26/43,not built.[35]
AS.66
Proposed civil freighter variant.[35]
AS.67
Proposed civil freighter variant.[35]

Accidents and incidents

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  • 8 April 1955:G-AMAB,Sir Francis BaconofBritish European Airwayswas damaged beyond repair in a forced landing south-west ofDüsseldorf,Germany.[38][39][26]This aircraft had often been used by the Queen and Prince Philip when travelling to Europe in the early 1950s.[40]
  • 6 February 1958:G-ALZU,Lord Burghley,also of BEA, in what became known as theMunich air disaster,crashed on takeoff after a refuelling stop atMunichwhile operating a charter flight fromBelgrade,Yugoslavia, toManchester,England. This crash received tremendous public attention in the UK as it involved team members and staff ofManchester United Football Club,together with representatives of the national press. Of the 44 people on the plane, 21 died in the crash and 2 died later, including eight Manchester United players.[41]The investigation eventually focused on runway slush adversely affecting the speed of the plane as it attempted to take off.
  • 14 April 1966:G-ALZXofDan-Airwas damaged beyond repair when its undercarriage collapsed on landing atBeauvais,France.[42]
  • 14 September 1967G-ALZSofAutairwas damaged beyond repair on landing atLuton Airport,UK. The aircraft overran the runway and ended up in soft clay.[43]
  • 3 July 1968:G-AMADofBKS Air TransportcrashedatLondon Heathrow Airport.All but two of its crew as well as several horses which were being transported and their grooms, were killed. A parkedTridentairliner was damaged beyond repair (G-ARPT) and another Trident had its tail torn off before the airliner hit terminal buildings and came to rest. The accident was caused by a failedflapactuating rod in the left wing. The Trident which suffered the damaged tail (G-ARPI) was subsequently repaired and later involved in an unconnectedfatal accidentin June 1972.[44]
  • 30 September 1968:G-AMAGof Dan-Air was damaged beyond repair in awheels-up landingatManston,United Kingdom.[38][45]

Operators

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Civil operators

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Australia
Norway
  • Norrønafly – proposed to operate two aircraft but they never entered service.
New Zealand
  • South Seas Airways – bought one aircraft but failed to gain an operators licence; the aircraft was not delivered to New Zealand.
Switzerland
  • Globe Air – operated three aircraft.[46]
United Kingdom
BEA "Elizabethan"G-AMAG"Sir Thomas Gresham" at Manchester (Ringway) Airport on the schedule to Heathrow in July 1953

Military operators

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Jordan
Morocco
  • Moroccan Royal Flight

Aircraft on display

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G-ALZO,at the Imperial War Museum Duxford, 2015

One Elizabethan,Christopher Marlowe(G-ALZO,c/n 5226) is on display at theImperial War Museum,DuxfordnearCambridgehaving undergone major restoration by the Duxford Aviation Society. The restoration was completed in April 2013 and the aircraft is presently part of the Duxford Collection.[47]

Specifications

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Airspeed Ambassador

Data fromAirspeed aircraft since 1931,[48]British Civil Aircraft since 1919 Volume 1[49]

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
  • Airfoil:root:NACA;tip:NACA[50]
  • 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 66118-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

See also

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Aircraft of comparable role, configuration, and era

Related lists

References

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Citations

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  1. ^abcTaylor 1970, p. 110.
  2. ^abcPhipp 2007, pp. 75–77.
  3. ^Taylor 1970, pp. 110–111.
  4. ^Taylor 1970, p. 111.
  5. ^Taylor 1970, pp. 111–112.
  6. ^Taylor 1970, pp. 112–113.
  7. ^abcTaylor 1970, p. 113.
  8. ^abcTaylor 1970, p. 114.
  9. ^abTaylor 1970, p. 115.
  10. ^abcSingfield 2000, p. 12.
  11. ^abcdTaylor 1970, p. 119.
  12. ^Taylor 1970, pp. 115–116.
  13. ^abTaylor 1970, pp. 116–117.
  14. ^abTaylor 1970, p. 117.
  15. ^Taylor 1970, pp. 118–119.
  16. ^abJackson 1973, p. 30.
  17. ^abTaylor 1970, p. 118.
  18. ^Gunston 1989, p. 128.
  19. ^Taylor 1970, pp. 127–128.
  20. ^Taylor 1970, pp. 119–121.
  21. ^abTaylor 1970, pp. 121–122.
  22. ^abTaylor 1970, p. 112.
  23. ^Taylor 1970, pp. 117–118.
  24. ^Boot 1990, pp. 25–26.
  25. ^Taylor 1970, p. 122.
  26. ^abcdeTaylor 1970, p. 125.
  27. ^Masefield and Gunston 2002, p. 83.
  28. ^Masefield and Gunston 2002, p. 214.
  29. ^Taylor 1970, p. 126.
  30. ^Jackson 1973, pp. 395–396.
  31. ^Taylor 1970, pp. 129–130.
  32. ^Taylor 1970, p. 127.
  33. ^Jackson 1973, p. 25.
  34. ^Jackson 1973, p. 26.
  35. ^abcde"Airspeed Type Designations."Flight International,23 February 1951, p. 228.
  36. ^Boot 1990, p. 25.
  37. ^Boot 1990, p. 24.
  38. ^abEastwood and Roach 1991, p. 7.
  39. ^"Accident description: Airspeed AS.57 Ambassador 2, 8 April 1955."Aviation-safety.net.Retrieved 13 November 2010.
  40. ^Eastwood and Roach 1991, p. 12.
  41. ^"Accident description: Airspeed AS.57 Ambassador 2, 6 February 1958."Aviation-safety.net.Retrieved 6 May 2012.
  42. ^Ranter, Harro."ASN Aircraft accident Airspeed AS.57 Ambassador 2 G-ALZX Beauvais-Tillé Airport (BVA)".aviation-safety.net.
  43. ^Ranter, Harro."ASN Aircraft accident Airspeed AS.57 Ambassador 2 G-ALZS London-Luton Airport (LTN)".aviation-safety.net.
  44. ^"Accident description: Airspeed AS.57 Ambassador 2, 3 July 1968."Aviation-safety.net.Retrieved 6 May 2012.
  45. ^"Accident description: Airspeed AS.57 Ambassador 2, 30 September 1968."Aviation-safety.net.Retrieved 13 November 2010.
  46. ^abcde"Airspeed AS.57 Ambassador".British aviation projects to productions.Retrieved8 May2020.
  47. ^"Airspeed Ambassador 2".Duxford Aviation Society.Retrieved30 December2020.
  48. ^Taylor 1970, pp. 132–134.
  49. ^Jackson 1987,p. 29
  50. ^Lednicer, David."The Incomplete Guide to Airfoil Usage".m-selig.ae.illinois.edu.Retrieved16 April2019.

Bibliography

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  • Boot, Roy (1990).From Spitfire to Eurofighter: 45 years of Combat Aircraft Design.Shrewsbury, UK: AirLife Publishing.ISBN1-85310-093-5.
  • Eastwood, Tony; Roach, John (1991).Piston Engine Airliner Production List.West Drayton, UK: The Aviation Hobby Shop.ISBN0-907178-37-5..
  • Gunston, Bill.Rolls-Royce Aero Engines.Patrick Stephens Limited, 1989.ISBN1-85260-037-3.
  • Jackson, A.J (1987) [1973].British Civil Aircraft since 1919 Volume 1.London: Putnam.ISBN0-85177-808-9..
  • James, Derek (April 2003). "Database: Airspeed Ambassador".Aeroplane Monthly.Vol. 31, no. 4. pp. 65–80.
  • Masefield, Sir Peter; Gunston, Bill (2002).Flight Path.Shrewsbury, England: Airlife.ISBN978-1-8403-7283-0.
  • Phipp, M (2007).The Brabazon Committee And British Airliners 1945–1960.Stroud: Tempus.ISBN978-0-7524-4374-4.
  • Quinlan, H. G. (1984). "Talkback".Air Enthusiast.No. 25. pp. 78–79.ISSN0143-5450.
  • Singfield, Tom (2000).Classic Airliners.Leicester, UK: Midland Publishing.ISBN1-85780-098-2..
  • Taylor, H A (1970).Airspeed Aircraft since 1931.London: Putnam.ISBN0370001109.
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