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 Avro Type 688 Tudor originated in 1943, following Specification 29/43 for a commercial adaptation of the Avro 694 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 685 York and the Avro 683 Lancaster.
The Avro 688 Tudor resulted from the Brabazon Committee recommendation Type IIIA, which was aimed at a four engine transport to serve the Trans-Atlantic routes 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 Avro Lincoln which was married to a new 10ft diameter, pressurised fuselage of circular cross-section. The Avro Tudor retained the tailwheel layout of the Avro Lincoln which was already outdated by the time of the emergence of the American Douglas DC-4 and the Lockheed Constellation.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 Avro 688 Tudor I had 1,750 hp Rolls-Royce Merlin 102 engines, although production aircraft used four 1,770 hp Merlin 621s.
The Avro 688 Tudor I was intended for use on the North Atlantic route and the Ministry of Supply ordered 14 Avro 688 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 the Lockheed Constellation, which had recently been introduced with TWA.
However, the Avro 688 Tudor I immediately suffered from a number of stability problems. These included longitudinal and directional instability which proved uncomfortable for fare-paying passengers.
A larger tailplane was fitted, whilst 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 buffeting problems.
On 7th February 1947, BOAC announced that they were not satisfied with the Avro 688 Tudor 1, following flight trials on the route to Nairobi. They identifyied their main concerns as 'unacceptable buffeting at speeds which became significant above approach speed'. They also complained of 'excessive swing on take-off' and reported considerably worse fuel economy than expected.
Fuel consumption was such an issue that BOAC said that 'they would find difficulty in using the aircraft on the Atlantic route' unless it could be considerably improved. This, they stated, was due to the large reduction in payload that would be needed to complete the route. One report indicated that the Trans-Atlantic payload would be reduced to only twelve passengers, and this was far from sustainable.
There were also problems with reliability of the cabin heater with heater failures causing the aircraft to have to descend, especially in adverse weather conditions. This negated the widly-publicised benefits of a pressurised cabin. On their side however, manufacturer Avro also complained of the huge difficulties induced by BOAC’s numerous requests for modifications.
Twelve Avro 688 Tudor 1 aircraft were built, of which three were scrapped. Others were variously converted to either Avro 688 Tudor 4 and Avro 688 Tudor 4B Super Traders.
Two Avro 688 Tudor I variants (G-AIYA and G-AJKC) were sent to Armstrong Whitworth for completion as VIP Transports for Cabinet Ministers. These aircraft were known as the Avro 688 Tudor 3 and had luxury accommodation for up to nine passengers, travelling 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 increased the passenger capacity to 32. A number of Avro 688 Tudor 1 aircraft were also retrospectively modified to this standard. If however, the aircraft was fitted with a Flight Engineers Station then these were reduced to 28 passenger seats and were designated as avro 688 Tudor 4Bs.
Despite the poor reception of the Avro 688 Tudor 1, A.V. Roe & Company felt able to promote the Avro 688 Tudor 4 in 1948 as ‘For luxurious travel over long ranges at high speed. Avro 688 Tudor 4 - four Rolls-Royce Merlin engines’.
The eventual main user of the Avro 688 Tudor was British South American Airways (BSAA) who used two, 28-seat Mk1 and six, 32-seat Mk4 aircraft.
The first Avro 688 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 Avro 688 Tudor 4B Super Trader (with a large fuselage cargo door) remained in service until 1959.
A second prototype Avro 688 Tudor I was rebuilt to Avro 688 Tudor 4 standards and it was subsequently converted to be powered by four Rolls-Royce Nene 4 turbojets in under-wing paired nacelles. This was known as the Avro 688 Tudor 8 (VX195) and was first flown at Woodford on 6th September 1948.
The Avro 688 Tudor 8 was used for high-altitude tests before being broken up in 1951. The technical data received during the tests however did lead 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 Avro 688 Tudor 4B, two Avro 688 Tudor 3 (which later reverted to Tudor 1), four completed as Avro 688 Tudor 4, four completed as Avro 688 Tudor 4B. Six aircraft were converted to Avro 688 Super Trader 4B standard.
The total of Avro 688 Tudor 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.
The Avro 689 Tudor 2 (described separate elsewhere on this website) was a stretched 60-seat version, which again proved to have performance problems. The Avro 689 series comprised the Avro Tudor 2, Avro Tudor 3, Avro Tudor 5 and Avro Tudor 7.
Avro 688 Specifications
|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
|Avro 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.|
|Avro Tudor 3||Avro Tudor 1 modified as executive transport aircraft. It could seat up to nine passengers, two built.|
|Avro Tudor 4||Avro 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.|
|Avro Tudor 4B||As Avro Tudor 4 retaining the Tudor 1s flight engineers station. Capacity 28 passengers.|
|Avro Super Trader 4B||Avro 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.|
|Avro Tudor 8||Conversion of a single Avro Tudor 4 with four 5,000 lbst Rolls-Royce Nene 5 jet engines.|
|Total built||22 aircraft (12 Avro Tudor 1, 2 Avro Tudor 3, 8 Avro Tudor 4/4B)|