https://en.wikipedia.org/wiki/Avro_Tudor

The Avro Type 688 Tudor was a British piston-engined airliner based on Avro's
four-engine Lincoln bomber, itself a descendant of the famous Lancaster heavy
bomber, and was Britain's first pressurised airliner. Customers saw the aircraft
as little more than a pressurised DC-4 Skymaster, and few orders were
forthcoming, important customers preferring to buy US aircraft. The tailwheel
undercarriage layout was also dated and a disadvantage.

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 nine types of commercial aircraft for
postwar use.

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
Airport and first flew on 14 June 1945. 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.

Design

The Tudor was a low-wing cantilever monoplane with four engines, a single fin
and rudder and a retractable tailwheel undercarriage (in its original
configurations).

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 3,300 imp gal (15,000 l;
4,000 US 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 43
ft (13 m) 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 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.

Operational history

Tudor I

The Tudor I was intended for use on the North Atlantic route. At the time, the
United States 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 70,000 lb (32,000 kg). The Tudor's tailwheel layout was also a
drawback. 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. 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. Following the RAE's
recommendations, 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.

In all, 9 different versions were built, including the Tudor 8 with jet engines.

Can be read at https://en.wikipedia.org/wiki/Avro_Tudor


Role
Airliner

Manufacturer
Avro

Designer
Roy Chadwick

First flight
14 June 1945

Primary users
B.S.A.A
BOAC

Produced
1945–1949

Number built
38

Developed from
Avro Lincoln

Developed into
Avro Ashton

Specifications (Avro 688 Tudor 1)

General characteristics
Crew: 5 (two pilots, flight engineer, radio operator, navigator)
Capacity: 24 passengers
Length: 79 ft 6 in (24.23 m)
Wingspan: 120 ft 0 in (36.58 m)
Height: 22 ft 0 in (6.71 m)
Wing area: 1,421 sq ft (132.0 m2)
Airfoil: root: NACA 23018; tip: NACA 23009
Max takeoff weight: 76,000 lb (34,473 kg)

Maximum landing weight: 66,000 lb (29,937 kg)
Powerplant: 4 × Rolls-Royce Merlin 100 V-12 liquid-cooled piston engines, 1,770
hp (1,320 kW) each for take-off
Propellers: 4-bladed Rotol constant-speed fully-feathering propellers

Performance
Maximum speed: 290 mph (470 km/h, 250 kn) at 66,000 lb (29,937 kg) at sea level
320 mph (278 kn; 515 km/h) at 8,000 ft (2,438 m)346 mph (301 kn; 557 km/h) at
20,000 ft (6,096 m)Cruise speed: 242 mph (389 km/h, 210 kn) at 66,000 lb (29,937
kg) at sea level
283 mph (246 kn; 455 km/h) at 12,000 ft (3,658 m)300 mph (261 kn; 483 km/h) at
22,500 ft (6,858 m)Range: 4,660 mi (7,500 km, 4,050 nmi) maximum fuel
4,100 mi (3,563 nmi; 6,598 km) with maximum payloadMaximum range:' 4,890 mi
(4,249 nmi; 7,870 km) at 10,000 ft (3,048 m) (engines delivering 500 hp (373
kW))
Service ceiling: 30,100 ft (9,200 m)

24,300 ft (7,407 m) on 3 engines10,000 ft (3,048 m) on 2 enginesAbsolute
ceiling: 31,500 ft (9,601 m)
26,000 ft (7,925 m) on 3 engines12,400 ft (3,780 m) on 2 enginesRate of climb:
990 ft/min (5.0 m/s) at sea level
730 ft/min (3.7 m/s) at 20,000 ft (6,096 m)Wing loading: 53.5 lb/sq ft (261
kg/m2)



*