Avro Tudor

infobox Aircraft
name = Tudor
type = Airliner
manufacturer = Avro



caption = A B.S.A.A. Avro Tudor 2
designer = Roy Chadwick
first flight = 14 June avyear|1945
introduced =
retired =
status =
primary user = B.S.A.A
more users = BOAC
produced =
number built = 38
unit cost =
variants with their own articles =
developed from = Avro Lincoln

Avro's Type 688 Tudor was a British piston-engined airliner based on their four-engine Lincoln bomber, itself a descendant of the famous Avro Lancaster, and was Britain's first pressurised airliner. Despite having a reasonably long range, customers saw the aircraft as little more than a pressurised Douglas DC-4, and few orders were forthcoming, important customers preferring to buy US aircraft.

Design and development

Avro began work on the Type 688 Tudor in 1943, following Specification 29/43 for a commercial adaptation of the Lancaster IV bomber, which was later renamed Lincoln. The specification was based on recommendations of the Brabazon Committee which issued specifications for 9 types of commercial aircraft for postwar use.

Avro first decided to build the Avro 687 (Avro XX), which was a Lincoln bomber with a new circular section pressurised 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 1,705 kg and a range of 6,400 km. [http://avia.russian.ee/air/england/avro_tudor.html "Avro Tudor."] "Virtual Aircraft Museum". Retrieved: 10 January 2006.]

Two prototypes were ordered in September 1944 and the first, G-AGPF, was assembled at Manchester's Ringway Airport and first flew on 14 June 1945. [http://www.avromuseum.ca/node/45 "Avro Timeline."] "Avro Museum", 2005. Retrieved: 10 January 2006.] It was the first British pressurised civilian aircraft, although the prototype originally flew unpressurised. The prototype Tudor I had 1,750 hp Rolls-Royce Merlin 102 engines, but the standard engines were 1,770 hp Merlin 621s.

Operational history

Tudor I

The Tudor I was intended for use on the North Atlantic route. At the time, the US had the Douglas DC-4 and Lockheed Constellation, which could both carry more passengers than the Tudor's 12, and also weighed less than the Tudor's weight of convert|70000|lb|abbr=on. Despite this, the Ministry of Supply ordered 14 Tudor Is for BOAC, and increased the production order to 20 in April 1945.

The Tudor I suffered from a number of stability problems, which included longitudinal and directional instability. To cure this, a larger tailplane was fitted, and the original finely curved 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 incapable of 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 Is were built, of which three were scrapped, while others were variously converted to Tudor IVB and Tudor Freighter Is.

As a result of all the Tudor I's delays, BOAC - with the support of the Ministry of Civil Aviation - sought permission to purchase tried and tested aircraft 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. [cite book | last = Geiger| first = Till | authorlink = | coauthors = | title = Britain and the Economic Problem of the Cold War | publisher = Ashgate Publishing, Ltd. | year = 2004 | location = | pages = p. 149 | url = | doi = | id = | isbn = 0754602877]

Tudor II

The passenger capacity of the Avro 688 was considered unsatisfactory, so a larger version was planned from the outset. Designated the Avro 689 (also Avro XXI), the Tudor II was designed as a 60-seat passenger aircraft fror BOAC, with the fuselage lengthened to convert|105|ft|7|in|abbr=on compared to the Tudor I's convert|79|ft|6|in|abbr=on and the fuselage increased by convert|1|ft|abbr=on to convert|11|ft|abbr=on diameter, making it the largest UK airliner at the time.

At the end of 1944, while it was still in the design stage, BOAC, Quantas, 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 DC-4 Skymaster instead, and the total order was reduced to 50.

During further testing, the prototype was destroyed on 23 August 1947 in a fatal crash which killed Roy Chadwick; air accident investigators later discovered that the crash was due to incorrect assembly of the aileron control circuit. [cite web | last = | first = | authorlink = | coauthors = | title = ASN Aircraft accident Avro 689 Tudor 2 G-AGSU Woodford Airport | work = | publisher = Aviation Safety Network | date = | url = http://aviation-safety.net/database/record.php?id=19470823-0 | format = | doi = | accessdate = ]

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 as the Tudor V.

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. [Citation | last = Payne | first = L.G.S. | author-link = | last2 = | first2 = | author2-link = | title = Britain's Long-term Policy for Transocean Airliners: The Industry Should Concentrate On New Gas-Turbine Types Now | newspaper = Daily Telegraph | pages = | year = | date = 5 February 1948 | url = ]

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 in the late 1940s and 1950s. [cite book | last = Yenne | first = William | authorlink = | coauthors = | title = Classic American Airliners | publisher = Zenith Imprint | year = 2005 | location = | pages = p. 22 | url = | doi = | id = | isbn = 0760319316]

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.

Tudor III

Two Tudor Is, G-AIYA and G-AJKC, were sent to Armstrong Whitworth for completion as VIP transports for Cabinet Ministers. They could accommodate 10 passengers and had 9 berths. They were reregistered as VP301 and VP312, and both were acquired by Aviation Traders in September 1953, VP301 being reconverted into a Tudor I.

In 1955, G-AIYA and the Tudor I G-AGRG were lenghtened to Tudor IV standard. Together with the unlengthened Tudor I G-AGRI, which had become a 42-seat passenger aircraft, they were used on Colonial Coach Services between the UK, Tripoli and Lagos.

Tudor IV

To meet a BSAA requirement, some Tudor Is were lenghtened by convert|5|ft|9|in|abbr=on, engined with 1,770 hp Rolls-Royce Merlin 621s and 1,760 hp Rolls-Royce Merlin 623s. With 32 seats and no flight engineer position, these were known as Tudor IVs, and when fitted with a flight engineer's position and 28 seats as Tudor IVBs.

The first example, G-AHNJ "Star Panther", 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 its first airplane, G-AHNK "Star Lion". 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 January - 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. Four Tudor IVs were fitted with convert|6|ft|10|in|abbr=on by convert|5|ft|5|in|abbr=on cargo doors aft and designated Super Traders IV or IVB, receiving their Certificate of Airworthiness in March 1955. Some remained in service until 1959, until G-AGRH "Zephyr" crashed in Turkey on 23 April.

Tudor V

The Tudor V was a modified version of the Tudor II with 44 seats. BSAA acquired 5 which never entered passenger service with the airline. They were instead stripped of their fittings and used as fuel tankers on the Berlin Airlift. They ended up making 2,562 sorties in 6,973 hours, carrying 22,125 tons of fuel into Berlin.

On 12 March 1950, G-AKBY, which had been returned to passenger service, crashed at Llandow, Wales, killing 80 of its passengers. [cite web | last = | first = | authorlink = | coauthors = | title = ASN Aircraft accident Avro 689 Tudor 5 G-AKBY Llandow | work = | publisher = Aviation Safety Network | date = | url = http://aviation-safety.net/database/record.php?id=19500312-0 | format = | doi = | accessdate = ]

Tudor VI

The Tudor VI was to be built for the Argentinian airline FAMA for South Atlantic service, with 32-38 seats or 22 sleeper berths, but none were built.

Tudor VII

The Tudor VII was the first production Tudor II fitted with Bristol Hercules air-cooled radial engines in an attempt to give better performance. The sole example built, G-AGRX, made its first flight on 17 April 1946, and was later fitted with shorter landing gear and the engines inclined to give better ground clearance in June 1948. G-AGRX was used for cabin temperature experiments, and was finally sold for spares in March 1954.

Tudor 8

The second prototype Tudor I was rebuilt to Tudor IV standards and fitted with four Rolls-Royce Nene turbojets. It was given military identification VX195 and made its first flight on 6 September 1948, being used for high-altitude experiments before being broken up in 1951.

Tudor 9

Following tests of the Tudor 8, the Ministry of Supply ordered six Tudor 9s, which were based on the Tudor II but with four Rolls-Royce Nenes and tricycle undercarriage. The original design was then modified and the type was produced as the Avro 706 Ashton, the first Ashton flying on 1 September 1950.

Description

The Tudor was a low-wing cantilever monoplane with four engines, a single fin and rudder and a retractable tailwheel undercarriage.

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 ailerons were fitted with trim 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 convert|3300|impgal|abbr=on 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 convert|43|ft|abbr=on twin-spar tailplane with inset divided elevators. The control surfaces were mass-balanced, and each had controllable trim and servo tabs.

The circular cross-section fuselage was an all-metal semi-monocoque structure, of convert|10|ft|abbr=on diameter, fitted with kapok-filled inner and outer skins 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.

Variants

All built by Avro at Woodford Aerodrome.

;688 Tudor 1:Production variant, 12 built, later conversion to other variants.;689 Tudor 2:Stretched version, five built.;688 Tudor 3:Tudor 1 modified by Armstrong Whitworth Aircraft as executive transport aircraft. it could seat up to nine passengers, two built.;688 Tudor 4:Stretched version of the Tudor 1 (but not the same as the Tudor 2 with the fuselage lengthened by only 6ft (1.83m)). It could seat up to 32 passengers, 11 built.;688 Tudor 4B:As Tudor 4 but retained the Tudor 1s flight engineers station, Small number of Tudor 1s were converted into Tudor 4Bs.;689 Tudor 5:Tudor 2 for BSAA, powered by four 1,770-hp (1,312-kW) Rolls-Royce Merlin 621 piston engines, six built. One aircraft crashed in 1950 killing 80 in the Llandow Air Disaster. ;689 Tudor 6:Ordered by the Argentinian airline FAMA, but the order was cancelled. None of the airframes were completed.;689 Tudor 7:Tudor 2 fitted with four 1,750-hp (1,305-kW) Bristol Hercules 120 radial piston engines, one prototype only.;688 Tudor 8:Jet-engined version of the Tudor 1. Tudor 1 "VX195" was fitted with four Rolls-Royce Nene turbojet engines.;Tudor 9:Jet-engined version of the Tudor 2, became the 706 Ashton;Super Trader 4B: Re-engined version. Fitted with four 1,760-hp (1,305-kW) Rolls-Royce Merlin 23 piston engines.;Tudor Freighter 1: Freight and cargo version. Three aircraft were used by BOAC during the 1949 Berlin Airlift.;711 Trader:Proposed freighter development of the Tudor 2 fitted with a tricycle landing gear; not built.

Operators

;flag|Canada|1921
*Lome Airways;UK
*Air Charter
*Airflight
*British Overseas Airways Corporation (BOAC)
*British South American Airways
*Surrey Flying Services

pecifications (Avro 688 Tudor 1)

aircraft specifications
plane or copter?=plane
jet or prop?=prop
ref=Jane's Fighting Aircraft of World War II [Jane 1946, p. 104.]
crew=5 (two pilots, flight engineer, radio operator, navigator)
capacity=24 passengers
length main=79 ft 6 in
length alt=24.23 m
span main=120 ft 0 in
span alt=36.58 m
height main=22 ft 0 in
height alt=6.71 m
area main=1,421 ft²
area alt=132 m²
airfoil=
max takeoff weight main=76,000 lb
max takeoff weight alt=34,500 kg
loaded weight main=66,000 lb
loaded weight alt=30,000 kg
more general=
engine (prop)=Rolls-Royce Merlin 100
type of prop=12-cylinder V12 engines
number of props=4
power main=1,770 hp
power alt=1,320 kW
power original=
max speed main= 320 mph
max speed alt= 512 km/h
max speed more= at 8,000 ft (2,440 m)
cruise speed main= 283 mph
cruise speed alt=453 km/h
cruise speed more=at 12,000 ft (3,660 m)
range main=3,630 mi
range alt= 5,840 km
ceiling main=30,100 ft
ceiling alt=9,180 m
climb rate main=990 ft/min
climb rate alt= 5 m/s
loading main=53.5 lb/ft²
loading alt=261 kg/m²
thrust/weight=
more performance=

ee also

* Star Tiger and Star Arielaircontent
related=
* Avro Lincoln
* Avro Lancastrian
* Avro Ashton
similar aircraft=
* Avro Canada Jetliner
* Vickers VC.1 Viking
lists=
see also=

References

Notes

Bibliography

* Angelucci, Enzo and Matricardi, Paolo. "World Aircraft - Commercial Aircraft 1935-1960". London: Sampson Low Guides, 1979. ISBN 0-562-00125-5.
* Holmes, Harry. "Avro - The History of an Aircraft Company". Wiltshire, UK: Crowood Press, 2004. ISBN 1-86126-651-0.
* Jackson, A.J. "Avro Aircraft since 1908, 2nd edition". London: Putnam Aeronautical Books, 1990. ISBN 0-85177-834-8.
* Jane, Fred T. “The Avro 688 Tudor I.” "Jane’s Fighting Aircraft of World War II". London: Studio, 1946. ISBN 1-85170-493-0.

External links

* [http://www.britishaircraft.co.uk/aircraftpage.php?ID=75 BAD]
* [http://www.jaapteeuwen.com/ww2aircraft/html%20pages/avro%20688%20tudor.htm Tudor]
* [http://www.apda61.dsl.pipex.com/Av4/Tudor.jpgA picture of the jet-powered Tudor 8]