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Armstrong Whitworth A.W.27

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Adapted from the English Wikipedia article Armstrong Whitworth A.W.27, available under CC BY-SA 4.0Updated 29 November 202532 sources
Armstrong Whitworth
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The Armstrong Whitworth A.W.27 Ensign represented the largest British-built four-engine monoplane airliner of the Interwar period.[1]

In 1934, Imperial Airways issued a request for proposals to develop a sizable monoplane airliner powered by four Armstrong Siddeley Tiger engines. Armstrong Whitworth responded with the Ensign design, intended to accommodate up to 40 passengers on routes spanning Europe and Asia while also facilitating the transport of airmail. This aircraft played a key role in linking Britain with onward seaplane services reaching destinations such as Australia and South Africa. However, initial operations were plagued by mechanical issues, and subsequent modifications only brought slight improvements in reliability and performance.

Throughout the Second World War, the Ensign fleet was operated by the British Overseas Airways Corporation (BOAC), formed from the merger of Imperial Airways and British Airways. These aircraft served routes between Britain and numerous points in the Middle East, Africa, and India, frequently supporting military efforts. In 1940, two Ensigns were lost due to enemy attacks, while another was captured in 1942 and later flown by French forces. The final passenger service for the Ensign took place in June 1946, with all remaining planes dismantled by the following year.

Background

Armstrong Whitworth A.W.27 Ensign G-ADSR Ensign at its rollout in 1938

The inception of the Ensign dates back to 1934 when Imperial Airways sought a large four-engine monoplane airliner powered by Armstrong Siddeley Tiger radial engines.[2] At that time, Imperial Airways was modernizing its fleet to replace aging biplane airliners like the Handley Page H.P.42, partly driven by new government regulations mandating that first-class mail within the British Empire be transported via air. Alongside this, Imperial Airways also commissioned a specification for a large flying boat, which resulted in the development of the Short Empire.[2] Armstrong Whitworth was directly approached and explored multiple configurations including low-wing monoplanes with two, three, or four engines. Nevertheless, Imperial Airways' managing director insisted on a four-engine shoulder-wing monoplane design, anticipating greater passenger appeal.[2]

The airline invested £27,000 for initial design efforts and agreed to pay £43,300 for the prototype's construction on 22 September 1934, aiming for delivery in 1936.[3] Subsequently, an order for eleven additional aircraft was placed in May 1935 at £37,000 each,[4] followed by a further two aircraft ordered in December 1936 at £39,766 13s 4d apiece, bringing total orders to fourteen.[3]

By October 1934, final specifications emphasized careful placement of tailplanes relative to wings to prevent wing flutter and tail buffeting.[2] Flight controls were mass-balanced to counter flutter risks, and wing fillets were incorporated to ensure smooth airflow around the fuselage. The airframe was constructed to satisfy military strength standards.[5] Performance criteria included maintaining a cruise speed of 155 mph (249 km/h) at 5,000 ft (1,500 m) and achieving takeoff within 320 yd (290 m).[3]

During the late 1930s, production priorities favored manufacturing of Whitley bombers for the Royal Air Force, which delayed progress on the Ensign project. Additionally, limited production capacity meant assembly took place not at Armstrong Whitworth’s primary Coventry facility,[6] but rather at another Hawker-Siddeley subsidiary, Air Service Training located in Hamble.[3]

Ongoing requests for design alterations from Imperial Airways caused delays extending up to two years,[7] resulting in the Ensign’s maiden flight occurring only on 24 January 1938.[8]

The introduction of the two Mark II variants was postponed further as Imperial Airways and Armstrong Whitworth evaluated their potential use as piggyback motherships akin to the Maia of the Short Mayo Composite, intended to carry smaller long-range parasite aircraft. This concept was eventually abandoned before modifications were completed.[9] Consequently, Everest first flew on 20 June 1940 and Enterprise followed with its inaugural flight on 28 October.[9]

Flight testing and production

During the Ensign's maiden flight, pilots noted excessively heavy ailerons and an overly stiff rudder, which was corrected by adjusting the rudder servo.[7] The second flight marked the initial retraction of the undercarriage, which underwent rigorous evaluation before being submitted to the Aeroplane and Armament Experimental Establishment (A&AEE) for Air Ministry certification.[10] While in testing, intermittent jamming of the elevators occurred at altitude; this issue was resolved by rerouting the connecting wires to accommodate fuselage contraction caused by low temperatures. A critical incident was narrowly avoided on 8 March 1938 when all four engines ceased operation due to incorrect fuel cock settings, forcing the aircraft to glide and execute a dead-stick landing at RAF Bicester.[11]

The prototype's flight tests revealed generally satisfactory handling qualities, though Royal Air Force pilots criticized its sluggish climb performance, which was attributed to the underpowered Tiger XI engines.[11] After completing flight trials, the aircraft received a certificate of airworthiness, authorizing operational deployment following modifications including redesigned trailing edge coverings, installation of an engine-driven compressor for brake charging, throttle control locks, and additional emergency exits for passengers.[12] Subsequently, the Ensign commenced its inaugural commercial flight between Croydon Airport and Paris, France on 24 October 1938.[13]

Design

Video of A.W.27 Ensign, including original news story introduction to public

The Ensign featured a high-wing cantilever monoplane design constructed primarily from lightweight alloy, with an oval-shaped fuselage and a conventional tailplane.[1] Its wing structure relied on a single robust internally braced box spar connected directly to both front and rear ribs. The wing’s leading edge was metal-clad; however, fabric covered the sections aft of the spar as well as the tailplane and vertical fin.[1] The airframe employed semi-monocoque construction techniques, combining stressed skin panels with transverse frames and longitudinal stringers. The wing was integrated into the upper portion of a deep fuselage, while tubular girders reinforced the floor structure.[14]

Equipped with hydraulically retractable landing gear that folded into the inner engine nacelles and a castoring tail wheel, the Ensign’s undercarriage presented considerable mechanical challenges during development.[14] At that time, its wheels were the largest produced in Britain,[14] fitted with Dunlop tyres measuring 6 ft 3 in (1.91 m) in diameter.[15] While Armstrong Whitworth designed and manufactured most components, sixteen hydraulic jacks controlling the flaps, undercarriage legs, locks, and doors were sourced from Lockheed locally.[15][14] Retraction was frequently erratic and uneven, taking significantly longer than anticipated.

Initially powered by four 800 hp (600 kW) moderately supercharged Armstrong Siddeley Tiger XI[1] radial engines—14-cylinder two-row units with 1,996 cu in (32.71 L) displacement[15]—mounted ahead of the wing leading edge on tubular steel frames with flexible rubber mounts enclosed in Siddeley long-chord cowlings,[15] these engines drove de Havilland three-blade two-position adjustable pitch propellers.[16] Once it became evident that these engines left the aircraft underpowered, they were replaced during returns to Armstrong Whitworth for mechanical rectifications with 855 hp (638 kW) Armstrong Siddeley Tiger XIC engines,[note 1] paired with constant speed propellers,[17] although this did not fully solve performance issues. The final two aircraft ordered by Imperial Airways in 1936 were equipped with 1,820 cu in (29.8 L) nine-cylinder single-row 950 hp (710 kW) Wright GR-1820-G102A Cyclone geared radial engines and Hamilton constant speed propellers as A.W.27A Ensign Mk.II models. Between 1941 and 1943, all eight remaining Mk.I aircraft were upgraded to Mk.II standard using these American powerplants.[18] This enhancement enabled operation in hot climates; however, early war cessation of engine production led to scarcity of spares and persistent pilot complaints regarding climb rate.[19] Steam heating was generated via a boiler utilizing engine exhaust gases distributed throughout the cabin.[15] Electrical power for lighting and battery recharging on the ground came from an auxiliary petrol-driven generator.[1]

The cockpit accommodated two pilots seated side-by-side with dual controls; behind the copilot on the right side sat a radio operator positioned sideways.[20] This operator managed a Marconi wireless transmitter/receiver set along with radio direction finding (RDF) equipment; on empire routes they also handled short-wave radio communications.[16] The standard crew complement comprised five members: two pilots, a radio operator, a steward, and a flight clerk; on Eastern routes a second steward replaced the clerk.[7]

Eight aircraft were configured for Empire routes while four served European routes. The Empire versions accommodated 27 passengers across three cabins or provided sleeping bunks for 20; European variants seated 40 passengers distributed among four main cabins.[20][1] Armstrong Whitworth asserted that interior layouts could be switched between configurations within fifteen minutes by installing partition walls and curtains. Seat cushions converted into bunk mattresses and also functioned as flotation devices in case of water landings.[14] The central section contained a large freight hold aligned with engine positions to minimize noise intrusion, along with a pantry and a lavatory located starboard side; connecting forward and rear compartments was a narrow corridor sometimes called the 'promenade' deck.[14] On Empire flights a flight clerk substituted one steward.[21][1] Aside from interior arrangements and short-wave radio equipment installation differences, there was minimal variation between these two versions.[1]

Operational history

Ensign Mark.I, G-ADTC Endymion in 1940 displaying wartime camouflage and roundels

The prototype was designated "Ensign" by Imperial Airways, a naming convention that also lent its name to the entire aircraft class, following the airline's usual practice. By Christmas 1938, three additional Ensigns—G-ADSS Egeria, G-ADST Elsinore, and G-ADSU Euterpe—had been completed and sent to Australia carrying holiday mail; however, all three experienced mechanical failures that prevented them from completing their journeys. Specifically, Elsinore had to return over approximately 2,500 mi (4,000 km) with its landing gear extended because it could not be retracted. As a result, Imperial Airways returned the entire fleet of five aircraft to Armstrong Whitworth for modifications. These included adjustments to control runs, a reduction in rudder surface area, installation of new constant-speed propellers, and fitting more powerful 935 hp (697 kW) Tiger IXC engines to enhance performance. The upgraded aircraft underwent testing at Martlesham Heath, which showed improved climb rates. Additional reliability improvements included automatic mixture controls, priming system modifications, constant speed propellers, and replacing bolts with studs in engine rocker arm brackets.

Starting in June 1939, the Ensigns were returned to Imperial Airways alongside the sixth aircraft produced. However, the airline altered its deployment strategy by abandoning Eastern routes. Plans for four Ensigns to operate under Indian Trans-Continental Airways from Calcutta were cancelled despite registrations and new names being assigned; notably, Euralus bore the Indian registration VT-AJG briefly before reverting to its British identity. By September 1939, eleven units had been delivered.

After the outbreak of the Second World War, all Ensigns were stored in October 1939 at Baginton Aerodrome while their role in wartime was evaluated. Each aircraft was camouflaged and assigned to a newly established route between Heston Aerodrome and Le Bourget Airport, Paris. Following the creation of British Overseas Airways Corporation (BOAC) in November 1939, these aircraft returned to civilian operation under National Air Communications rather than being requisitioned for military use. In 1940, several Ensigns were flown by crews from No.24 Squadron RAF, although they were not given military serial numbers.

With the German invasion of the Low Countries, Ensigns participated in supply flights to France and evacuated personnel ahead of the German occupation in June 1940. Three aircraft were lost due to enemy action that year: G-ADSX Ettrick and G-ADSZ Elysian in France, and G-ADTC Endymion at Bristol Whitchurch in November 1940. After sustaining bomb damage on 1 June 1940, Ettrick was abandoned at Le Bourget. Although rumors suggested it was used by Germany and re-engined with Daimler-Benz powerplants, photographic evidence of its burnt wreckage shortly after German arrival disproves this claim.

Between 1941 and 1943, all eight surviving Ensigns were re-engined and subsequently deployed on BOAC's routes connecting Africa with India.

Ensign Mark.II, G-ADSV Explorer during refueling at Accra in the Gold Coast (modern Ghana)

On 3 February 1942, during a flight along the Takoradi route between Egypt and British-controlled Ghana, engine issues—including power loss and oil leaks affecting three engines—forced Enterprise into a belly landing approximately 300 mi (480 km) short of its destination near what is now Nouakchott, then a small fishing village in Vichy-controlled French West Africa. The crew destroyed sensitive documents before being evacuated to Bathurst in Gambia via an RAF Short Sunderland flying boat. Subsequently located by a Vichy French patrol on 12 February 1942, Enterprise was repaired at Dakar and briefly operated by the Armée de l'Air de Vichy. In July 1942 it transferred to Air France, renamed Nouakchott, with its registration letter changed from G (Great Britain) to F (France). After several months operating in Mauritania, it was flown to France in October 1942 where it received an airworthiness certificate in November. However, following the German invasion of Vichy France in December 1942, it was captured along with some 1876 other French aircraft despite attempts to relocate it quickly. Early in 1943, Deutsche Luft Hansa assessed the captured plane but deemed it outdated; its older Cyclone engines were more valuable for use in their Douglas DC-3 fleet. Consequently, the engines were removed and the airframe scrapped at Montaudran near Toulouse in December 1943 without further flight.

During routine Certificate of Airworthiness inspections it was discovered that camouflage paint combined with heat accelerated deterioration of fabric-covered surfaces on the Ensigns; as a result they reverted to a silver finish. After World War II ended, due partly to maintenance challenges related to fabric surfaces and outdated engines affecting performance reliability, a decision was made to retire the fleet and repatriate them to the United Kingdom. Euterpe, which had been grounded since February 1945, was cannibalized for spare parts to maintain other aircraft.

From 1944 onward, Ensigns operated routes between Cairo and Calcutta. The final passenger service occurred in June 1946 when G-ADSW Eddystone flew from Cairo to Hurn via Marseille after delays caused by repairs in the Middle East. Although conversion options were explored and sales offers made for the type, operating expenses deterred potential buyers. Ultimately, all remaining aircraft were dismantled at Hamble during March and April 1947 and scrapped.

Accidents and incidents

  • On 15 December 1939, G-ADSU Euterpe suffered damage during a forced landing. Later that month, it was reported to be at Bonniksen's Airfield near RAF Chipping Warden with a compromised undercarriage.[22]
  • On 23 May 1940, while stationed on the ground at Merville, Nord, France, G-ADSZ Elysean was assaulted by three Luftwaffe Messerschmitt Bf 109 fighters and subsequently destroyed by fire.[22][23]
  • Also on 23 May 1940, G-ADTA Euryalus was involved in a crash at RAF Lympne, Kent. It was among six aircraft that endured a Luftwaffe attack on Merville Airfield but incurred damage. Originally bound for Croydon, the port inner engine malfunctioned over the English Channel, prompting the pilot to divert to RAF Hawkinge. Following failure of the starboard inner engine, the course was adjusted to Lympne. Upon landing, the starboard undercarriage failed to lock properly, causing the wing to scrape the ground and the aircraft to breach a fence. Euryalus was flown to RAF Hamble in June; however, it was later dismantled to provide parts for repairing G-ADSU Euterpe, which had been damaged in December 1939. Officially written off on 15 November 1941, it was scrapped in September 1942.[24]
  • On 1 June 1940, G-ADSX Ettrick was left behind at Le Bourget Airport, Paris, France because the runway was littered with time-delay bombs. The burnt remains of the aircraft were photographed shortly thereafter.[22][23]
  • On 9 November 1941, G-AFZU Everest came under attack by a Luftwaffe Heinkel He 111 over the Bay of Biscay. The crew managed a safe landing at RAF Portreath, Cornwall. The plane underwent repairs and was returned to operational status.[22]
  • On 1 February 1942, G-AFZV Enterprise executed a forced landing near Nouakchott due to engine failure. The crew were rescued successfully; the aircraft was recovered by French forces and incorporated into Air France's fleet before being seized by German forces in December 1942, who removed its engines and scrapped it.[25]
  • On 4 September 1942, G-ADSR Ensign incurred damage after its undercarriage accidentally retracted while stationary in Nigeria. It was promptly restored to service; however, a comprehensive Certificate of Airworthiness inspection in September 1944 revealed more extensive damage than initially assessed. Consequently, repairs were halted and the airframe scrapped on 3 January 1945.[26]
  • On 1 January 1946, G-ADSW Eddystone experienced undercarriage failure shortly after departing Cairo during its final revenue flight before retirement. This resulted in a belly landing at RAF Castel Benito in Tripoli.[27] Repairs were completed by 3 June 1946 when it undertook the last flight ever made by an Ensign aircraft en route to the UK scrapyard.[28]

Variants

A.W.27 Ensign Mk.I
Equipped with four Armstrong Siddeley Tiger IX radial piston engines delivering 800 hp (600 kW) or alternatively the Tiger IXC variant rated at 850 hp (630 kW).
A.W.27A Ensign Mk.II
Powered by four Wright GR-1820-G102A Cyclone radial piston engines, each producing 950 hp (710 kW).

List of aircraft

Comprehensive roster of Armstrong Whitworth Ensign aircraft
Designation Registration(s) Operator(s) Category Remarks
Mk.I
Ensign G-ADSR Imperial Airways/BOAC Eastern/Empire class Upgraded to Mk.II standard. Withdrawn from service in 1944
Egeria[note 2] G-ADSS[note 2] Imperial Airways/BOAC Eastern/Empire class Initially registered as VT-AJE and named Ellora. Later converted to Mk.II
Elsinore G-ADST Imperial Airways/BOAC Eastern/Empire class Upgraded to Mk.II
Euterpe G-ADSU[note 2] Imperial Airways/BOAC Eastern/Empire class Originally assigned VT-AJF registration. Later converted to Mk.II
Explorer G-ADSV Imperial Airways/BOAC Eastern/Empire class Converted to Mk.II standard
Eddystone G-ADSW Imperial Airways/BOAC Western/European class Upgraded to Mk.II configuration
Ettrick G-ADSX Imperial Airways/BOAC Western/European class[29] Abandoned and subsequently destroyed in 1940
Empyrean G-ADSY Imperial Airways/BOAC Western/European class Converted to Mk.II specification
Elysian G-ADSZ Imperial Airways/BOAC Western/European class Lost due to enemy action in May 1940
Euralus G-ADTA[note 2] Imperial Airways/BOAC Eastern/Empire class Initially designated VT-AJG registration.

Written off in November 1941

Echo G-ADTB Imperial Airways/BOAC Eastern/Empire class Upgraded to Mk.II standard
Endymion[note 2] G-ADTC[note 2] Imperial Airways/BOAC Eastern/Empire class Originally assigned VT-AJH and named Etah
Mk.II
Everest G-AFZU BOAC Registered as G-ADTE but never operated under this registration
Enterprise/
Nouakchott 		G-AFZV
F-AFZV/F-BAHD 		BOAC/
Armée de l'Air/Air France 		Allocated G-ADTD registration but not utilized operationally

Operators

France Vichy France authorities
Template:UK
  • British Overseas Airways Corporation (BOAC)
  • Imperial Airways London (IAL)
  • Royal Air Force (RAF)

Specifications (A.W.27A Mk.II)

Three-view illustration of the Armstrong Whitworth A.W.27 from L'Aerophile, June 1937

Template:Aircraft specs

See also

Template:Aircontent

Notes

  1. ↑ The primary differences included increased supercharger boost on takeoff from 2.5 to 3.5 lb/in (0.045 to 0.063 kg/mm) and substitution of rocker arm bracket bolts with studs to address common failures.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Four units were assigned Indian registrations beginning with VT, and two (Ellora and Etah) were also given names for Indian Trans-Continental Airways operations from Karachi, though delivery was ultimately cancelled.

Citations

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Tapper, 1988, p.237
  2. ↑ 2.0 2.1 2.2 2.3 Tapper, 1988, p.235
  3. ↑ 3.0 3.1 3.2 3.3 Tapper, 1988, p.236
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named imp
  5. ↑ Tapper, 1988, pp.235-236
  6. ↑ Tapper, 1988, pp.236-237
  7. ↑ 7.0 7.1 7.2 Tapper, 1988, p.279
  8. ↑ Jackson, 1973
  9. ↑ 9.0 9.1 Ricco, 2017 p.18
  10. ↑ Tapper, 1988, pp.239-241
  11. ↑ 11.0 11.1 Tapper, 1988, p.241
  12. ↑ Tapper, 1988, p.242
  13. ↑ Tapper, 1988, p.243
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 Tapper, 1988, p.278
  15. ↑ 15.0 15.1 15.2 15.3 15.4 NACA, 1937, p.7
  16. ↑ 16.0 16.1 NACA, 1937, p.6
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Tapper244
  18. ↑ Flight, 1957, p.247
  19. ↑ Tapper, 1988, p.251
  20. ↑ 20.0 20.1 Cite error: Invalid <ref> tag; no text was provided for refs named jane
  21. ↑ Moss, January 1957, p.204
  22. ↑ 22.0 22.1 22.2 22.3 Harbar, 2015, pp.77-94
  23. ↑ 23.0 23.1 Ricco, 2017 p.23
  24. ↑ Moss, January 1957, pp.204-205
  25. ↑ Ricco, 2017 p.18-23
  26. ↑ Tapper, 1988, p.250-251
  27. ↑ Tapper, 1988, p.252
  28. ↑ Tapper, 1988, p.253
  29. ↑ Higham, 2016, pp.160-161
  30. ↑ Lewis, 1968, p.22

Bibliography

  • Armstrong Whitworth 27 "Ensign" Commercial Airplane (British) An all-metal high-wing monoplane. Aircraft Circulars No. 206. Washington, DC: National Advisory Committee for Aeronautics. 1937 – via UNT digital library. from Flight, January 7 and April 1, 1937
  • Bluffield, Robert (2009). Imperial Airways – The Birth of the British Airline Industry 1914–1940. Surrey, England: Ian Allan. ISBN 978-1906537074.
  • Bridgman, Leonard (1988). Jane's Fighting Aircraft of World War II. New York: Crescent Books. ISBN 0517679647.
  • Harrison, W.A. (March 2015). "Aeroplane Database: Armstrong Whitworth Ensign". Aeroplane. Stamford: Key Publishing. pp. 77–94. ISSN 0143-7240.
  • Britain's Imperial Air Routes, 1918 to 1939: The story of Britain's overseas airlines (Revised ed.). Fonthill. 2016. pp. 160–161. ISBN 978-1-78155-370-1.
  • Jackson, A.J. (1973). British Civil Aircraft since 1919. Vol. 1 (2nd ed.). London: Putnam. ISBN 0370100069.
  • Lewis, Peter (1968). Squadron Histories: R.F.C., R.N.A.S. and R.A.F., since 1912 (2nd ed.). London, UK: Putnam. ISBN 978-0370000220.
  • Moss, P.W. (15 January 1957). "Ensign Class: The History of a Fleet of Airliners That Went to War: Part 1". Flight. Vol. 71, no. 2508. London, UK: Iliffe and Sons. pp. 203–206.
  • Moss, P.W. (22 February 1957). "Ensign Class: The History of a Fleet of Airliners That Went to War: Part 2". Flight. Vol. 71, no. 2509. London, UK: Iliffe and Sons. pp. 247–250.
  • Ricco, P Phillipe. ""Flag of Convenience"". "The Aviation Historian" (issue 27) October 2017 Horsham, UK pages 18–23 issn 2051-1930. {{cite journal}}: no-break space character in |journal= at position 25 (help)
  • {{cite magazine last1="Stroud" first1="John" title="Wings of Peace" magazine=Aeroplane Monthly date="July 1988" volume="16" issue="7" pages="433–437" issn="0143-7240"}}
  • Template:Cite book last="Tapper" first="Olive" title="Armstrong Whitworth Aircraft since 1913" publisher="Putnam" location="London" year="1988" isbn="0851778267"

External links

Related profiles

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