Avro 688 and 689 Tudor and 711 Trader

Low-wing cantilever monoplane to Specification 29/43 to meet the requirements of OR.152 for a Long Range Civil Transport, resulting 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 crew of five consisted of two pilots, a flight engineer, radio operator and navigator. Passenger capacity was 24 day passengers, or 12 on night (sleeper) flights. The wing, based on that of the Lincoln, was a five-piece, all-metal, twin-spar structure, the untapered centre section carrying 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 3,300 imp gal 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 servo tabs. The pressurised, circular cross-section, fuselage was an all-metal semi-monocoque structure, of 10 ft (3.0 m) 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. The prototype was fitted with four 1,750 h.p. Rolls-Royce Merlin 102 powerplants, although production aircraft used four 1,770 h.p. Merlin 621s.

Type 688 Tudor I Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
120 ft	79 ft 6 in	20 ft 11 in	1421 sq ft	47960 lb	71000 lb	210 mph/ 182 kn	260 mph/ 226 kn	3630 mi	26000 ft
36.58 m	24.23 m	6.38 m	132.02 m2	21754 kg	32205 kg	338 km/h	418 km/h	5842 km	7925 m

Tudor I modified by Armstrong Whitworth Aircraft as executive transport aircraft to meet the requirements of OR.210, and had luxury accommodation for up to nine passengers, travelling by day or night.

Tudor I with fuselage lengthened by 5 ft 9 in, to Specification 28/46 to meet the requirements of OR.152 for a Civil Transport for BSAA. Elimination of the Flight Engineer Station increased the passenger capacity to 32. Four Rolls-Royce Merlin 621s or 1,760 h.p. Merlin 623 powerplants.

As Tudor IV but retained the Tudor Is flight engineers station, reducing passenger capacity to 28, to meet the requirements of Specification 11/48 for a Medium Range Civil Transport for BOAC.

Tudor IVB with large freight door in the port side.

Tudor IV fitted with four Rolls-Royce Nene 4 turbojets in under-wing paired nacelles.

60-seat passenger aircraft to Specification 12/44 to meet the requirements of OR.152 for a Medium Range Civil Transport. As Type 688 with the fuselage lengthened to 105 ft 7 in and increased by 1 ft to 11 ft diameter, along with a reprofiled nose. Four 1,750 h.p. Rolls-Royce Merlin 102, 1,740 h.p. Merlin 600A or 1,770 h.p. Merlin 621 powerplants.

Type 689 Tudor II Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
120 ft	105 ft 7 in	24 ft 3 in	1421 sq ft	46300 lb	80000 lb	235 mph/ 204 kn	295 mph/ 256 kn	2330 mi	25550 ft
36.58 m	32.18 m	7.39 m	132.02 m2	21001 kg	36287 kg	378 km/h	475 km/h	3750 km	7788 m

44 passenger version of Tudor II to Specification 39/46 to meet the requirements of OR.152 for a Civil Transport for BSAA.

Tudor II fitted with four 1,750 h.p. Bristol Hercules 120 powerplants in an attempt to give better performanc, and was later fitted in June 1948 with shorter landing gear with the engines repositioned (inclined) to give better ground clearance.

Freighter development of the Tudor II fitted with a tricycle undercarriage. Four Rolls-Royce Merlin 623 or Bristol Hercules 763 powerplants. Airframes were allocated for conversion (See Type 689 Production Table), but none built.