The Avro 688 and 689 Tudor series of low-wing cantilever monoplanes provided a most unhappy saga for AV Roe & Co Ltd. Numerous variants were constructed with different engine installations and a succession of modifications were required to cure inadequate handling and stability problems.
The Type 688 Tudor originated in 1943, following Specification 29/43 for a commercial adaptation of the Lincoln. Because wartime transport aircraft development had been ceded to the United States, Britain set up a committee, the Brabazon Committee, to set out specifications for new commercial aircraft to be developed after the war.
Until the appearance of these new designs, British airlines relied on flying boats and adaptations of wartime bombers, such as the Handley Page Halton, Avro York and the Avro Lancastrian.
The Tudor resulted from the Brabazon Committee recommendation Type IIIA, which was aimed at a four engine transport to serve the Trans-Atlantic route and provide services to the British Empire to South Africa and India and the Far East.
The Avro 688 Tudor I was designed by Roy Chadwick using four Rolls-Royce Merlin engines and the wing of the Lincoln, married to a new 10 ft diameter pressurised fuselage of circular cross-section. The Tudor retained the tailwheel layout of the Lincoln which was already outdated following the emergence of the American Douglas DC-4 and the Lockheed Constellation.
Two prototypes were ordered in September 1944 and the first (TT176 / G-AGPF) first flew on 14th June 1945 from Ringway Airport, Manchester. It was the first British pressurised civil transport aircraft and the prototype Tudor I had 1,750 hp Rolls-Royce Merlin 102 engines although production aircraft used four 1,770 hp Merlin 621s.
The Tudor I was intended for use on the North Atlantic route and the Ministry of Supply ordered 14 Tudor I aircraft for BOAC, increasing this order to 20 aircraft in April 1945. Passenger capacity was 24 day passengers, or 12 on night (sleeper) flights and it was intended as a direct competitor to the Douglas DC-4 and Lockheed Constellation which had recently been introduced with TWA.
However, the Tudor I immediately suffered from a number of stability problems which included longitudinal and directional instability which proved uncomfortable for fare-paying passengers.
A larger tailplane was fitted and the original curved fin and rudder were replaced by larger vertical surfaces of a less attractive shape. The engine nacelles and the wing to fuselage fairings were also modified to reduce aerodynamic buffet problems.
On 7 February 1947, BOAC announced that they were not satisfied with the Tudor 1 following flight trials on the route to Nairobi identifying their main concerns as unacceptable buffeting at speeds significantly above approach speed, excessive swing on take-off and considerably worse fuel economy than expected. Fuel consumption was such that BOAC said that they would find difficulty in using the aircraft on the Atlantic route unless it could be considerably improved, due to the large reduction in payload that would be involved. One report indicates that the Trans-Atlantic payload would be reduced to only twelve passengers which was far from sustainable.
There were also problems with cabin heater reliability with heater failures causing the aircraft to have to descend, especially in adverse weather conditions which negated the widly-publicised benefits of a pressurised cabin. On their side however, manufacturer Avro also complained of the difficulties induced by BOAC’s numerous requests for modifications.
Twelve Tudor 1s were built of which three were scrapped whilst others were variously converted to Tudor 4 and Tudor 4B Super Traders.
The Avro 689 Tudor 2 (described on a separate web page) was a stretched 60-seat version, which again proved to have performance problems. The Avro 689 series comprised the Tudor 2, Tudor 3, Tudor 5 and Tudor 7.
Two Tudor Is (G-AIYA and G-AJKC) were sent to Armstrong Whitworth for completion as VIP Transports for Cabinet Ministers. These aircraft were known as Tudor 3s and had luxury accommodation for nine passengers by day or night. They were allocated RAF Serials (VP301 and VP312).
The Avro 688 Tudor 4 introduced a fuselage stretch of 5ft 9in and elimination of the Flight Engineer Station to increase the passenger capacity to 32 and a number of Tudor 1 aircraft were also retrospectively modified to this standard. If fitted with a Flight Engineer Station and with 28 passenger seats, these aircraft were designated as Tudor 4Bs.
Despite the poor reception of the Tudor 1, Avro felt able to promote the Tudor 4 in 1948 as follows: ‘For luxurious travel over long ranges at high speed. Avro Tudor 4 - four Rolls-Royce Merlin engines’.
The eventual main user of the Tudor was British South American Airways (BSAA) who used two 28-seat Mk 1 and six 32-seat Mk 4. The first Tudor 4 (G-AHNJ ‘Star Panther’) first flew on 9th April 1947, entering service with BSAA at the end of October on BSAA routes to South America via Lisbon, The Azores and Bermuda.
Unfortunately, BSAA suffered tragic losses of the aircraft, with 2 aircraft (G-AHNP ‘Star Tiger’) and (G-AGRE ‘Star Ariel’) being lost in January 1948 and January 1949.
Consequently, the type’s certification for passenger use was withdrawn in March 1949 and the type relegated to freighter work. The Tudor 4B Super Trader (with a large fuselage cargo door) remained in service until 1959.
The second prototype Tudor I was rebuilt to Tudor 4 standards. It was subsequently converted to be powered by four Rolls-Royce Nene 4 turbojets in under-wing paired nacelles. The Tudor 8 (VX195) was first flown at Woodford on 6th September 1948.
The Tudor 8 was used for high-altitude tests before being broken up in 1951 although it led to the development of the Avro 706 Ashton.
Production of the Avro 688 Tudor 1 series (Tudor 1, 3, 4/4B and 8) comprised a total of 22 aircraft made up as follows: Two prototypes (one converted to Tudor 4, then Tudor 8), ten completed as Tudor 1 of which two converted to Tudor 4B, two Tudor 3 (which later reverted to Tudor 1), four completed as Tudor 4, four completed as Tudor 4B. Six aircraft were converted to Super Trader 4B standard.
The total of Avro 688 series was 22 aircraft; the total for the stretched Avro 689 Tudor 2 series was a single prototype (destroyed during flight testing) and a further 10 production aircraft.
Avro 688 Specifications
|Avro 688||Tudor 1||Tudor 4||Tudor 8|
|Powerplants||Four 1,770 hp R-R Merlin 621 engines||Four 5,000 lbst R-R Nene 5 jet engines|
|Span||120 ft 0 in|
|Maximum Weight||71,000 lb||80,000 lb||80,000 lb|
|Capacity||24 passengers (day)||32 passengers||Test crew & instrumentation|
|Maximum Speed||260 mph||282 mph||385 mph|
|Cruising Speed||210 mph||210 mph||350 mph|
|Range||3,630 miles||4,000 miles||1,720 miles|
Avro 688 Variants & Numbers Built
|Tudor 1||Production variant, 12 built, later conversion to other variants. Fuselage length 79ft 6in. Four 1,750 hp Rolls-Royce Merlin 102 or 1,770 hp Merlin 621 engines.|
|Tudor 3||Tudor 1 modified as executive transport aircraft. It could seat up to nine passengers, two built.|
|Tudor 4||Tudor 1 lengthened by 5 ft 9 in to Specification 28/46 to meet the requirements of BSAA. Capacity up to 32 passengers. Total of eight 4/4B built new, five other aircraft converted.|
|Tudor 4B||As Tudor 4 retaining the Tudor 1s flight engineers station. Capacity 28 passengers.|
|Super Trader 4B||Tudor 4B with large freight door on port side. Four 1,760 hp Rolls-Royce Merlin 23 piston engines. Six aircraft converted to this standard.|
|Tudor 8||Conversion of a single Tudor 4 with four 5,000 lbst Rolls-Royce Nene 5 jet engines.|
|Total built||22 aircraft (12 Tudor 1, 2 Tudor 3, 8 Tudor 4/4B)|
No examples of the Avro 688 Tudor 1 Series survive.