Product Code Database
The Avro Type 688 Tudor was a British airliner based on Avro's four-engine Avro Lincoln bomber, itself a descendant of the famous Avro Lancaster heavy bomber, and was Britain's first pressurised airliner. Customers saw the aircraft as little more than a pressurised DC-4, and few orders were forthcoming, important customers preferring to buy US aircraft. The tailwheel undercarriage layout was also dated and a disadvantage.
Avro first proposed to build the Avro 687 (Avro XX), which was a Lincoln bomber with a new circular section pressurized fuselage and a large single fin and rudder in place of the predecessor's double ones. During the design stage, the idea of a simple conversion was abandoned and the Avro 688 was designed, which retained the four Rolls-Royce Merlin engines. It was designed by Roy Chadwick who, due to wartime restrictions, could not design a completely new aircraft, but had to use existing parts, tools and jigs. Using the Lincoln's wing, Chadwick, who had worked on the Lancaster, designed the Tudor to incorporate a new pressurized fuselage of circular cross-section, with a useful load of 3,765 lb (1,705 kg) and a range of 3,975 mi (6,400 km).
Two prototypes were ordered in September 1944 and the first, G-AGPF, was assembled by Avro's experimental flight department at Manchester's Ringway AirportScholefield 1997, p. 37. and first flew on 14 June 1945. "Avro Timeline." Avro Museum, 2005. Retrieved: 10 January 2006. It was the first British pressurised civilian aircraft, although the prototype initially flew unpressurised. The prototype Tudor I had 1,750 hp (1,305 kW) Rolls-Royce Merlin 102 engines, but the standard engines were 1,770 hp (1,320 kW) Merlin 621s.
The wing was of NACA 23018 section at the root, and was a five-piece, all-metal, twin-spar structure. The untapered centre section carried the inboard engines and main undercarriage, while the inner and outer sections were tapered on their leading and trailing edges, with the inner sections carrying the outboard engines. The were fitted with trim tab and balance tabs, and there were hydraulically operated split flaps in three sections on each side of the trailing edges of the centre section and inner wings. A fuel capacity was given by eight bag tanks, one on either side of the fuselage in the centre section and three in both inner wings.
The all-metal tail unit had a dorsal fin integrated with the fuselage, and a twin-spar tailplane with inset divided elevators. The control surfaces were mass-balanced, and each had controllable trim and .
The circular cross-section fuselage was an all-metal semi-monocoque structure, of diameter, fitted with Ceiba pentandra noise insulation above floor level. The hydraulically operated main-wheel units were similar to those of the Lancaster, had single Dunlop wheels and retracted rearward into the inboard engine nacelles. The twin tailwheels retracted rearward into the fuselage and were enclosed by twin longitudinal doors.
The Tudor I suffered from a number of stability problems, which included longitudinal and directional instability. The problem was handed over to the Royal Aircraft Establishment at RAE Farnborough, where an extensive programme of testing was carried out, the test pilot being Eric Brown.Brown, Eric "Winkle" (2006), Wings on my Sleeve, Phoenix (Orion Books Ltd), p. 161 Following the RAE's recommendations, a larger tailplane was fitted, and the original fin and rudder were replaced by larger vertical surfaces. BOAC added to the delays by requesting more than 340 modifications, and finally rejected the Tudor I on 11 April 1947, considering it unacceptable for North Atlantic operations. It had been intended that 12 Tudors would be built in Australia for military transport, but this plan was abandoned.
Twelve Tudor I aircraft were built, of which three were scrapped, while others were variously converted to the Tudor IVB and Tudor Freighter I configurations.
As a result of all the Tudor I delays, BOAC – with the support of the Ministry of Civil Aviation – sought permission to purchase aircraft with known performance and reliability, such as the Lockheed Constellation and the Boeing Stratocruiser, for its Atlantic routes instead of the Tudor. Despite BOAC's reluctance to purchase Tudors, the Ministry of Supply continued to subsidize the aircraft.Geiger 2004, p. 149.
At the end of 1944, while it was still in the design stage, BOAC, Qantas and South African Airways decided to standardise on the Tudor II for Commonwealth air routes, and BOAC increased its initial order for 30 examples to 79.
The prototype Tudor II G-AGSU first flew on 10 March 1946 at Woodford Aerodrome. The changes in design had however resulted in a loss of performance and the aircraft could not be used in hot and high conditions which resulted in Qantas ordering the Constellation and South African Airways, the Douglas DC-4 instead, with the total order reduced to 50.
During further testing, the prototype was destroyed on 23 August 1947 in a fatal crash on take off from Woodford which killed Roy Chadwick; air accident investigators later discovered that the crash was due to incorrect assembly of the aileron control circuit. ASN Aircraft accident Avro 689 Tudor 2 G-AGSU Woodford Airport. Aviation Safety Network. Retrieved: 23 February 2009.
The engines on the second prototype were changed to Bristol Hercules radials and the aircraft became the prototype Tudor 7, which did not go into production. Unimpressed by the type's performance during further tropical trials, BOAC did not operate the Tudor II and only three production Tudor IIs were built. Six aircraft were built for British South American Airways (BSAA) as the Tudor V.
The third of the pre-production Tudor 2s, initially G-AGRZ, was used for pressurisation tests as VZ366 at RAE Farnborough.
The second Tudor II to be completed, G-AGRY, went to Nairobi for tropical trials as VX202, but these were unsatisfactory and Tudor II orders were reduced to 18. Eventually, only four Tudor IIs were completed including the prototype.
From 1946 on, the potential purchase of US aircraft by operators such as BOAC led to criticism of government policy, because of the damage that could potentially be caused to Britain's civil aircraft industry by a failure to buy the Tudor. L.G.S. Payne, The Daily Telegraph's aeronautical correspondent, said that British government policy had led to the development of aircraft which were uncompetitive in price, performance and economy. He blamed the Ministry of Supply's planners for this failure, since the industry had effectively been nationalised and argued that the government should pursue the development of jet aircraft instead of "interim types" such as the Tudor.Payne, L.G.S. "Britain's Long-term Policy for Transocean Airliners: The Industry Should Concentrate on New Gas-Turbine Types Now". The Daily Telegraph, 5 February 1948.
BOAC cancelled its order for Tudors in 1947, instead taking delivery of 22 Canadair North Stars which they renamed C-4 Argonauts, and used them extensively between 1949 and 1960.Yenne 2005, p. 22.
Six aircraft ordered as Tudor IIs were intended to be modified with tricycle landing gear, for use by BSAA as freighters, and designated the 711 Trader. They were not built, but a parallel design using the same landing gear was produced as the jet-powered Avro Ashton.
In 1955, G-AIYA and the Tudor I G-AGRG were lengthened to Tudor IV standard. Together with the un-lengthened Tudor I G-AGRI, which had become a 42-seat passenger aircraft, they were used on the Air Charter Ltd Colonial Coach Services between the UK, Tripoli and Lagos.Jackson 1990, p. 387.
BSAA's new flagships received mixed reviews from pilots. Some greeted it with enthusiasm, such as Captain Geoffrey Womersley, who described it as "the best civil airliner flying." Others rejected it as an unsound design. BSAA's chief pilot and manager of operations, Gordon Store, was unimpressed:
"The Tudor was built like a battleship. It was noisy, I had no confidence in its engines and its systems were hopeless. The Americans were fifty years ahead of us in systems engineering. All the hydraulics, the air conditioning equipment and the recircling sic fans were crammed together underneath the floor without any thought. There were fuel-burning heaters that would never work; we had the floorboards up in flight again and again.Brookes 1992, p. 40.
The Tudor IV's fuel-burning heaters were made by Janitrol and were also used on the US-built passenger aircraft – such as the Lockheed Constellation – as well as later on US-ordered variants of the Vickers Viscount.
The first example, G-AHNJ Star Panther, first flew on 9 April 1947. The Tudor IV received its Certificate of Airworthiness on 18 July 1947, and on 29 September, BSAA took delivery of G-AHNK Star Lion, the first of its six Tudor 4s to be delivered. It departed the next day from Heathrow on a flight to South America, and on 31 October began flights from London to Havana via Lisbon, the Azores, Bermuda and Nassau.
On the night of 29–30 January 1948, Tudor IV G-AHNP Star Tiger, with 31 people on board, disappeared without trace between Santa Maria in the Azores and Bermuda. Tudors were temporarily grounded and while the cause of the accident was never determined, the type returned to service on 3 December 1948, when a weekly service was begun from London to Buenos Aires via Gander, Bermuda, and other stops, returning via the Azores.
Disaster struck again on 17 January 1949, when Tudor IV G-AGRE Star Ariel also disappeared, this time between Bermuda and Kingston, Jamaica, with the loss of 20 people, and the Tudor IVs were once more grounded. The subsequent fleet shortage led to BSAA being taken over by BOAC. Pressurisation problems were suspected to be the cause of the two accidents, and the remaining aircraft were flown as unpressurised freighters under the designations Tudor Freighter IV and IVB.
A Tudor IV was tested at De Havilland's Hatfield Airfield on 1 April 1949 to check "no lift angle"Duxbury diary 1949. and flown to Heathrow on 8 April.
After storage for some years at Manchester Airport, four ex-BSAAC Tudor IVs were bought by Air Charter Limited in late 1953.Scholefield 1997, p. 84. They were fitted with by cargo doors aft by Aviation Traders and designated Super Traders IV or IVB, receiving their Certificate of Airworthiness in March 1955. These were operated by Air Charter Ltd on long distance freight flights as far as Christmas Island. Some remained in service until 1959, until G-AGRH Zephyr crashed in Turkey on 23 April 1959.
On 12 March 1950, G-AKBY, which had been returned to passenger service with Airflight Ltd, on a charter flight from Ireland, crashed at RAF Llandow, South Wales, with the resulting death of 80 of its passengers and crew. "ASN Aircraft accident Avro 689 Tudor 5 G-AKBY Llandow." Aviation Safety Network. Retrieved: 23 February 2009.
In 1953, Lome Airways leased an ex BSAA Tudor 5 from Surrey Flying Services as CF-FCY for freight operations in Canada. It was retired at Stansted and scrapped in 1959.Jackson 1973, p. 467.
|
|
