Avro 691 Lancastrian – The Very First Jet Airliner
Which was the first jet airliner to make an international flight? The Avro 961 Lancastrian.
You might think that would be the de Havilland Comet airliner that made its first flight in 1949. Good guess, but not correct.
The record books show that the first international flight of a jet airliner took place in November 1946 when a Lancastrian flew from London’s Heathrow airport to the Aéroport de Paris at Le Bourget!
The Lancastrian was an odd Frankenstein of an aircraft, a lightly modified version of the Lancaster bomber that was used both as an airliner and as a test-bed for several early British turbojets: the aircraft that made the flight to Le Bourget in 1946 was powered by two Rolls-Royce Merlin piston engines plus two Rolls-Royce Nene turbojets.
The Merlin engines were shut down during flight, which is why this became the first officially recognised international jet passenger flight (though just two passengers were carried on that occasion).
This is the largely forgotten story of the Avro Lancastrian and the role it played in the development of British turbojet engines and the creation of the first true jet airliners.
During World War Two, Britain produced relatively few transport aircraft. The biplane Vickers Type 264 Valentia had entered service in 1934, and it was slow, with a top speed of around 130mph. Despite that, the Valentia continued to be used up to 1944.
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The monoplane Bristol Bombay, a light bomber/transport aircraft introduced in 1939, was a little better, but it could carry just 24 troops at speeds of up to 190mph.
As war approached, the British aviation industry was fully committed to developing and producing as many fighters and bombers as possible, so instead of producing its own transport aircraft, under the Lend-Lease agreement Britain received over 2,000 examples of the American Douglas C-47 Skytrain, a rugged transport aircraft based on the DC-3 airliner and identified in Britain as the Dakota. Later in the war, Britain received 24 examples of the even better Douglas C-54 Skymaster, based on the DC-4 airliner.
The availability of these US transport aircraft meant that Britain didn’t have to use scarce manpower and resources to create its own modern transport aircraft.
This doesn’t seem to have been the result of a formal agreement between Britain and America, it was simply a pragmatic approach at a time when the British aviation industry was wholly focussed on fighter and bomber development and production, but it did have an unfortunate knock-on effect after the war.
The experience of producing large numbers of transport aircraft put the US aviation industry in a good position to begin the creation of post-war airliners. Britain found itself without any modern indigenous transport aircraft that could be quickly and easily converted to airliners. As a short-term solution, British aviation companies began to consider the conversion of existing bombers into airliners.
The first conversion of a Lancaster bomber into an airliner had taken place in Canada in 1943. Victory Aircraft (later to become part of Avro Canada) converted a number of Lancaster Mk X bombers to become a transport/passenger aircraft, the Lancaster XPP (Lancaster Type X – Passenger Plane).
This involved the removal of all turrets, the creation of a new streamlined nose and tail cone, and the fitment of two 400-gallon fuel tanks in the bomb bay. Nine XPPs were built, and these were used by Trans-Canada Airlines (TCA) to carry up to ten passengers at a time on the Montreal-Prestwick route.
In Britain, consideration of a similar conversion began in early 1945, while the war was still in progress. As the war drew to a close, orders for Lancaster bombers were cancelled and Avro was left with a number of partly completed aircraft.
Rather than scrap these, it was decided to re-purpose them as airliners, identified as the Avro 691 Lancastrian. This was very similar to the Lancaster XPP, with all turret openings faired over and a new streamlined nose and tail being added.
Large fuel tanks were fitted in what had been the bomb bay giving the Lancastrian both long range and good performance with a cruising speed of 240mph and a range of over 4,000 miles. However, the slim fuselage of the Lancaster which was retained on the Lancastrian gave this aircraft the very limited ability to carry passengers.
Originally designed for a crew of seven, it was only possible to fit nine passenger seats in the Lancastrian, making it suitable as a VIP transport or mail plane, but severely restricting its use as a commercial airliner.
Nevertheless, the British Overseas Airways Corporation (BOAC) took delivery of 30 Lancastrians beginning in April 1945 and used these on several international routes including England-Australia. Because little else was available, other British carriers also used the Lancastrian and in 1946, a Lancastrian operated by British South American Airways (BSAA) undertook the very first scheduled passenger departure from London’s new airport at Heathrow.
Turbojet Test Bed
The limited passenger capacity of the Lancastrian meant that it was never going to be anything more than a short-term solution for British airlines, but this aircraft found a new and unexpected role as a test bed for turbojet engines.
The Rolls-Royce RB.41 Nene turbojet was the third jet engine produced by Rolls-Royce and one of the most powerful in the world when it was first to run in October 1944, producing almost 5,000lbs of thrust.
The Nene was first tested in flight when it was installed in a modified American Lockheed P-80 Shooting Star. The Nene-powered P-80 undertook a number of test flights from RAF Syerston in Nottinghamshire until it was destroyed after a hard landing in December 1945.
The problem with using the diminutive P-80 as a test bed was that it was too small to carry the extensive instrumentation needed to monitor the engine’s performance and there was no backup if the new engine failed. Even before the P-80 was destroyed, it was decided that test flights would continue, but in a larger, multi-engine aircraft.
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At the end of October 1945, the first Lancastrian was delivered to the Rolls-Royce Flight Test Establishment in Nottinghamshire and work began on installing two Nene turbojets. The two outboard Merlins were removed and replaced with turbojets in streamlined nacelles under the wings.
The flaps and ailerons were shortened to keep them safely out of the jet efflux and additional steel plates were added to the wing undersides to protect them from the heat of the engines.
This aircraft was first flown in August 1946, and under the power of the turbojets alone and with the propellors of the two Merlin engines feathered, it was found to be capable of maintaining a speed of 250 mph.
It was this aircraft that was used for the flight to Le Bourget in November, carrying just two passengers: Avro’s Chief Designer, Roy Chadwick, and William Thompson of the Ministry of Supply.
One further Lancastrian was converted to use Nene engines before testing began of a new type of Lancastrian powered by the de Havilland Ghost 50 turbojet designed for use in the Comet airliner.
Two Lancastrians were fitted with a pair of Ghost 50 engines in outboard nacelles and one of these was also fitted with the Walter HWK 109-500 liquid-fuelled rocket that was briefly considered as a means of providing a rocket take-off boost system for the Comet, though this was never used on the airliner.
From August 1948, two further Lancastrians were used as test beds for what would become Rolls-Royce’s most successful post-war turbojet, the axial flow Avon. As before, these were fitted outboard of the two Merlin engines in underslung nacelles.
The Avon would go on to power later versions of the Comet airliner as well as British military aircraft including the Hawker Hunter and the Vickers Valiant nuclear bomber.
The final conversion of the Lancastrian as a turbojet test bed would be used to install one of the main competitors to the Rolls-Royce Avon, the Armstrong Siddeley Sapphire. This advanced axial-flow turbojet engine would be used in the Gloster Javelin interceptor and early prototypes of the Handley Page Victor strategic bomber.
The first flight of the Sapphire Lancastrian took place in January 1950. The Lancastrian was so successful as a means of safely testing engines that a total of ten were converted to engine-test beds both for turbojets and for piston engines including the Rolls-Royce Griffon and Merlin 600. None of the Lancastrians equipped with turbojets were ever used in passenger operations but these test-bed aircraft continued to be flown until the mid-1950s.
As an airliner, the Lancastrian was not particularly successful. Its capacity to carry only a handful of passengers in a noisy, unheated, draughty, narrow fuselage meant that it could never compete with purpose-built designs that offered passengers the luxury of heated, pressurised cabins.
Despite this, it did provide passenger air travel at a time when little else was available in Britain. Over 90 Lancastrians were produced by Avro with early examples being converted from bombers while later versions were built specifically for passenger operations. In addition to BOAC and BSAA, the Lancastrian was also used by British European Airways (BEA) and the last Lancastrian wasn’t retired from passenger service until 1960!
Avro didn’t give up on the concept of converting bombers into airliners after the Lancastrian. In 1944, Avro produced what was originally identified as the Lancaster IV bomber, with an enlarged fuselage and more powerful engines.
This was later re-named as the Avro Lincoln and went on to replace the Lancaster in RAF service. At the same time that Lancastrians were being produced, Avro began a new airliner design based on the Lincoln, but this wasn’t a simple conversion.
It would lead to the development of the successful Avro Tudor airliner which incorporated a circular section, and pressurised fuselage, though it retained the Merlin engines of the bomber.
Tudors were used by a number of airlines during the 1950s and ironically, the final version, the Tudor 9 (later re-named the Avro Ashton) was powered by four of the Rolls-Royce Nene turbojets tested in the Lancastrian.
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However, as a test-bed for new turbojet designs, the Lancastrian proved to be ideal. It provided space for ample instrumentation and, if there was a problem with the turbojets, it was entirely capable of maintaining flight and landing safely using only the power of its two Merlin engines. In the role of a flying test bed, the Lancastrian safely provided data and experience that was essential to the development of British turbojet engines in the 1950s.
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- Crew: 4 + 1 cabin crew
- Capacity: 9
- Length: 76 ft 10 in (23.42 m)
- Wingspan: 102 ft (31 m)
- Height: 17 ft 10 in (5.44 m)
- Wing area: 1,297 sq ft (120.5 m2)
- Empty weight: 37,190 lb (16,869 kg) equipped
- Maximum landing weight: 58,000 lb (26,308 kg)
- Powerplant: 4 × Rolls-Royce Merlin 24/2 V-12 liquid-cooled piston engines, 1,620 hp (1,210 kW) each
- Maximum speed: 315 mph (507 km/h, 274 kn) at 58,000 lb (26,308 kg) and 12,000 ft (3,658 m)