Rolls-Royce Conway
Encyclopedia
The Rolls-Royce RB.80 Conway was the first by-pass engine
(or turbofan) in the world to enter service. Development started at Rolls-Royce
in the 1940s, but it was used only briefly in the late 1950s and early 1960s before other turbofan designs were introduced that replaced it. The Conway powered versions of the Handley Page Victor
, Vickers VC10
, Boeing 707-420
and Douglas DC-8-40
. The name "Conway" is an Anglo-Saxon permutation of River Conwy
, in Wales
, in keeping with Rolls' use of river names for jet engines.
is an obvious example, which uses a series of additional turbine stages to capture this energy to power a propeller. However there is a tradeoff in propeller efficiency compared to forward speed, so while the turboprops are efficient engines, they are only efficient at speeds of up to 500 mph (804.7 km/h; 410.6 kn). This meant there was a sweet spot
between the high efficiencies of the turboprop at low speeds and the jet at high speeds that was not being directly addressed. This spot, between about 450 mph (724.2 km/h; 369.5 kn) and 700 mph (1,126.5 km/h; 574.8 kn), was precisely where the vast majority of commercial jet aircraft spent most of their time.
The basic concept of bypass had been studied from the earliest days of jet engine design. Alan Arnold Griffith
had proposed a number of different bypass engine designs as early as the 1930s while he and Hayne Constant
were trying to get their axial-flow jet engines working at the Royal Aircraft Establishment
. Frank Whittle
's Power Jets
also studied a number of bypass configurations. However, the need to get jet engines into service during the war meant this work had to be put aside in favor of simpler designs with shorter introduction times. The ending of the war changed priorities dramatically, and by 1946 Rolls-Royce agreed that existing engines like the Rolls-Royce Avon
were advanced enough that it was time to start work on new concepts like bypass.
Griffith suggested building a purely experimental design using parts of the Avon and another experimental jet engine, the AJ.25 Tweed. In April 1947 a 5000 pound-forces (22,241.1 N) design was proposed, but over the next few months it was modified to evolve into a larger 9250 pound-forces (41,146 N) design in response to a need for a new engine to power the Mk.2 low-level version of the Vickers Valiant
bomber. A go-ahead to start construction of this larger design was given in October, under the RB.80 name.
The new version had a four stage low-pressure compressor driven by a two-stage turbine, and an eight stage high-pressure compressor driven by another two-stage turbine. Now known as the RCo.2, design work was completed in January 1950 and the first example ran for the first time in July 1952 at 10000 pound-forces (44,482.2 N) thrust. By this time the low-level Valiant Pathfinder had been abandoned, and so the first example was also destined to be the last. Nevertheless it proved the basic concept sound, and "ran perfectly for the whole of its 133 hours life."
The work on the RCo.2 was soon put to good use. In October 1952 the Royal Air Force
awarded a contract for the Vickers V-1000
, a large jet-powered strategic transport that was intended to allow the V bomber
force to be supported in the field through air supply only. Vickers
also planned on developing a passenger version of the same basic design as the VC-7. The V-1000 design looked like an enlarged de Havilland Comet
, but from the Valiant it took the wing layout and added a compound sweep (a passing vogue in UK design). It also featured the Comet's wing-embedded engines, demanding an engine with a small cross-section, which limited the amount of bypass the engine could use. It nevertheless required higher power to support a 230000 pounds (104,326.2 kg) gross weight, so Rolls responded with the larger RCo.5.
The new engine was similar to the RCo.2 in most ways, differing in details. The low-pressure compressor now had six stages, and the high-pressure nine, driven by two and one stage turbines respectively. The first RCo.5 ran in July 1953, and passed an official type rating in August 1955 at 13000 pound-forces (57,826.9 N). Construction of the prototype V-1000 was well underway at Vickers Armstrongs' Wisley works in the summer of 1955 when the entire project was cancelled. Having second thoughts about the concept of basing the V-bombers away from the UK, the need for the V-1000 became questionable and it became an easy decision to drop the project.
B.2 variant, replacing the Armstrong Siddeley Sapphire of earlier models. For this role Rolls designed an even larger model, the RCo.8 of 14500 pound-forces (64,499.2 N), which ran for the first time in January 1956. However the RCo.8 was skipped over after receiving a request from Trans-Canada Airlines (TCA) to explore a Conway powered Boeing 707
or Douglas DC-8
, having interested both companies in the idea. Rolls responded by designing an even larger model of the Conway, the 16500 pound-forces (73,395.7 N) RCo.10, and offering the similar military-rated RCo.11 for the Victor. The new engine differed from the RCo.8 in having a new "zeroth stage" at the front of the low-pressure compressor, further increasing cold airflow around the engine. The RCo.10 first flew in an Avro Vulcan
on 9 August 1957, followed by the RCo.11 in the Victor on 20 February 1959.
Boeing had calculated that the Conway, even though it had limited bypass in keeping with its original in-wing mounting, would increase the range of the 707-420 by 8% compared to the otherwise identical 707-320 powered by the non-bypass Pratt & Whitney JT4A
(J75). In May 1956 TCA ordered Conway-powered DC-8s, followed by additional orders from Alitalia
and Canadian Pacific Air Lines, while the Conway powered 707 was ordered by BOAC
, Lufthansa
, Varig
and Air India
. RCo.10's development was so smooth that after delivering a small number for testing, further deliveries switched to the 17150 pound-forces (76,287 N) RCo.12, which was designed, built and tested before the airframes had finished their testing. These models also featured a distinctive scalloped silencer, and a thrust reverser that could provide up to 50% reverse thrust.
Although successful in this role, only sixty-nine 707's and DC-8s were built with the Conway, due largely to the delivery of the first US-built bypass engines, particularly the Pratt & Whitney JT3D
. Nevertheless the Conway was successful on these designs, and was the first commercial aero engine to be awarded clearance to operate for periods up to 10,000 hours between major overhaul.
Rolls continued working on the Conway, delivering the RCo.15. This was similar to the earlier RCo.12, but had a larger zeroth-stage along with a larger engine housing to fit it. This improved cruise fuel consumption by 3% while at the same time increasing take-off thrust to 18500 pound-forces (82,292.1 N). The designs were otherwise similar, and RCo.12's could be re-built into RCo.15's during overhauls.
. As the need for wing-embedded engines was long abandoned by this point, Rolls dramatically increased the zeroth-stage diameter to increase the bypass from about 25% to 60%, and further increasing thrust to 20250 pound-forces (90,076.5 N). First run in March 1961, it would be the most successful of all the Conways, powering all of the VC10 fleet, later models with the RCo.43.
The engine produced 17150 pound-forces (76,287 N) for takeoff, weighed 4500 pounds (2,041.2 kg) and had a specific fuel consumption of 0.712 at take-off thrust and 0.87 for cruise.
By 1968 a Hyfil carbon-fibre fan assembly was in service on Conways of the VC10s operated by BOAC
. A sectioned Conway is displayed as part of a stack of jet engines at the National Museum of Flight at East Fortune in Scotland. A Conway can also be found in the storage wing of the Canada Aviation and Space Museum.
Turbofan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...
(or turbofan) in the world to enter service. Development started at Rolls-Royce
Rolls-Royce Limited
Rolls-Royce Limited was a renowned British car and, from 1914 on, aero-engine manufacturing company founded by Charles Stewart Rolls and Henry Royce on 15 March 1906 as the result of a partnership formed in 1904....
in the 1940s, but it was used only briefly in the late 1950s and early 1960s before other turbofan designs were introduced that replaced it. The Conway powered versions of the Handley Page Victor
Handley Page Victor
The Handley Page Victor was a British jet bomber aircraft produced by the Handley Page Aircraft Company during the Cold War. It was the third and final of the V-bombers that provided Britain's nuclear deterrent. The other two V-bombers were the Avro Vulcan and the Vickers Valiant. Some aircraft...
, Vickers VC10
Vickers VC10
The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...
, Boeing 707-420
Boeing 707
The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...
and Douglas DC-8-40
Douglas DC-8
The Douglas DC-8 is a four-engined narrow-body passenger commercial jet airliner, manufactured from 1958 to 1972 by the Douglas Aircraft Company...
. The name "Conway" is an Anglo-Saxon permutation of River Conwy
River Conwy
The River Conwy is a river in north Wales. From its source to its discharge in Conwy Bay it is a little over long. "Conwy" is sometimes Anglicized as "Conway."...
, in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, in keeping with Rolls' use of river names for jet engines.
Background
In early jet engines the exhaust was much faster and hotter than it had to be for efficient thrust; capturing some of that energy would improve the fuel economy of the engine. The turbopropTurboprop
A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...
is an obvious example, which uses a series of additional turbine stages to capture this energy to power a propeller. However there is a tradeoff in propeller efficiency compared to forward speed, so while the turboprops are efficient engines, they are only efficient at speeds of up to 500 mph (804.7 km/h; 410.6 kn). This meant there was a sweet spot
Sweet spot
Sweet spot may refer to:*Sweet spot *Sweet spot *Sweet spot...
between the high efficiencies of the turboprop at low speeds and the jet at high speeds that was not being directly addressed. This spot, between about 450 mph (724.2 km/h; 369.5 kn) and 700 mph (1,126.5 km/h; 574.8 kn), was precisely where the vast majority of commercial jet aircraft spent most of their time.
The basic concept of bypass had been studied from the earliest days of jet engine design. Alan Arnold Griffith
Alan Arnold Griffith
Alan Arnold Griffith was an English engineer, who, among many other contributions, is best known for his work on stress and fracture in metals that is now known as metal fatigue, as well as being one of the first to develop a strong theoretical basis for the jet engine.-Early work:A. A...
had proposed a number of different bypass engine designs as early as the 1930s while he and Hayne Constant
Hayne Constant
Hayne Constant, C.B., C.B.E., F.R.S, F.R.Ae.S. was an English mechanical and aeronautical engineer who developed jet engines during World War II....
were trying to get their axial-flow jet engines working at the Royal Aircraft Establishment
Royal Aircraft Establishment
The Royal Aircraft Establishment , was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence , before finally losing its identity in mergers with other institutions.The first site was at Farnborough...
. Frank Whittle
Frank Whittle
Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS was a British Royal Air Force engineer officer. He is credited with independently inventing the turbojet engine Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS (1 June 1907 – 9 August 1996) was a British Royal Air...
's Power Jets
Power Jets
Power Jets Ltd was a United Kingdom company set up by Frank Whittle for the purpose of designing and manufacturing jet engines.-History:Founded on January 27, 1936, the company consisted of Whittle, Rolf Dudley-Williams, James Collingwood Tinling, and Lancelot Law Whyte of investment bankers O T...
also studied a number of bypass configurations. However, the need to get jet engines into service during the war meant this work had to be put aside in favor of simpler designs with shorter introduction times. The ending of the war changed priorities dramatically, and by 1946 Rolls-Royce agreed that existing engines like the Rolls-Royce Avon
Rolls-Royce Avon
|-See also:-Bibliography:* Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9-External links:**** a 1955 Flight article on the development of the Avon...
were advanced enough that it was time to start work on new concepts like bypass.
Griffith suggested building a purely experimental design using parts of the Avon and another experimental jet engine, the AJ.25 Tweed. In April 1947 a 5000 pound-forces (22,241.1 N) design was proposed, but over the next few months it was modified to evolve into a larger 9250 pound-forces (41,146 N) design in response to a need for a new engine to power the Mk.2 low-level version of the Vickers Valiant
Vickers Valiant
The Vickers-Armstrongs Valiant was a British four-jet bomber, once part of the Royal Air Force's V bomber nuclear force in the 1950s and 1960s...
bomber. A go-ahead to start construction of this larger design was given in October, under the RB.80 name.
Early models
During development it was decided to further improve the basic design by adding another feature then becoming common, a "two spool" compressor arrangement. In earlier designs the engine generally consisted of a series of compressor stages connected via a shaft to one or more turbine stages. Although this arrangement is mechanically simple, it has the disadvantage of lowering the efficiency of the compressor, where a higher rotational speed is useful at higher compressions. In the multi-spool design the compressor is separated into "spools" designed to operate at their most efficient speed, driven by separate turbines via concentric shafts.The new version had a four stage low-pressure compressor driven by a two-stage turbine, and an eight stage high-pressure compressor driven by another two-stage turbine. Now known as the RCo.2, design work was completed in January 1950 and the first example ran for the first time in July 1952 at 10000 pound-forces (44,482.2 N) thrust. By this time the low-level Valiant Pathfinder had been abandoned, and so the first example was also destined to be the last. Nevertheless it proved the basic concept sound, and "ran perfectly for the whole of its 133 hours life."
The work on the RCo.2 was soon put to good use. In October 1952 the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
awarded a contract for the Vickers V-1000
Vickers V-1000
The Vickers-Armstrongs V-1000 was a prototype jet-powered cargo aircraft designed to a UK Ministry of Supply requirement for a strategic transport to support the V bomber fleet. Both the Ministry and Vickers also intended to use the same basic design as the VC7, a six-abreast trans-Atlantic jet...
, a large jet-powered strategic transport that was intended to allow the V bomber
V bomber
The term V bomber was used for the Royal Air Force aircraft during the 1950s and 1960s that comprised the United Kingdom's strategic nuclear strike force known officially as the V-force or Bomber Command Main Force...
force to be supported in the field through air supply only. Vickers
Vickers
Vickers was a famous name in British engineering that existed through many companies from 1828 until 1999.-Early history:Vickers was formed in Sheffield as a steel foundry by the miller Edward Vickers and his father-in-law George Naylor in 1828. Naylor was a partner in the foundry Naylor &...
also planned on developing a passenger version of the same basic design as the VC-7. The V-1000 design looked like an enlarged de Havilland Comet
De Havilland Comet
The de Havilland DH 106 Comet was the world's first commercial jet airliner to reach production. Developed and manufactured by de Havilland at the Hatfield, Hertfordshire, United Kingdom headquarters, it first flew in 1949 and was a landmark in aeronautical design...
, but from the Valiant it took the wing layout and added a compound sweep (a passing vogue in UK design). It also featured the Comet's wing-embedded engines, demanding an engine with a small cross-section, which limited the amount of bypass the engine could use. It nevertheless required higher power to support a 230000 pounds (104,326.2 kg) gross weight, so Rolls responded with the larger RCo.5.
The new engine was similar to the RCo.2 in most ways, differing in details. The low-pressure compressor now had six stages, and the high-pressure nine, driven by two and one stage turbines respectively. The first RCo.5 ran in July 1953, and passed an official type rating in August 1955 at 13000 pound-forces (57,826.9 N). Construction of the prototype V-1000 was well underway at Vickers Armstrongs' Wisley works in the summer of 1955 when the entire project was cancelled. Having second thoughts about the concept of basing the V-bombers away from the UK, the need for the V-1000 became questionable and it became an easy decision to drop the project.
Production versions
The Conway was saved once again when it was selected to power the Handley Page VictorHandley Page Victor
The Handley Page Victor was a British jet bomber aircraft produced by the Handley Page Aircraft Company during the Cold War. It was the third and final of the V-bombers that provided Britain's nuclear deterrent. The other two V-bombers were the Avro Vulcan and the Vickers Valiant. Some aircraft...
B.2 variant, replacing the Armstrong Siddeley Sapphire of earlier models. For this role Rolls designed an even larger model, the RCo.8 of 14500 pound-forces (64,499.2 N), which ran for the first time in January 1956. However the RCo.8 was skipped over after receiving a request from Trans-Canada Airlines (TCA) to explore a Conway powered Boeing 707
Boeing 707
The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...
or Douglas DC-8
Douglas DC-8
The Douglas DC-8 is a four-engined narrow-body passenger commercial jet airliner, manufactured from 1958 to 1972 by the Douglas Aircraft Company...
, having interested both companies in the idea. Rolls responded by designing an even larger model of the Conway, the 16500 pound-forces (73,395.7 N) RCo.10, and offering the similar military-rated RCo.11 for the Victor. The new engine differed from the RCo.8 in having a new "zeroth stage" at the front of the low-pressure compressor, further increasing cold airflow around the engine. The RCo.10 first flew in an Avro Vulcan
Avro Vulcan
The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, was a jet-powered delta wing strategic bomber, operated by the Royal Air Force from 1956 until 1984. Aircraft manufacturer A V Roe & Co designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced,...
on 9 August 1957, followed by the RCo.11 in the Victor on 20 February 1959.
Boeing had calculated that the Conway, even though it had limited bypass in keeping with its original in-wing mounting, would increase the range of the 707-420 by 8% compared to the otherwise identical 707-320 powered by the non-bypass Pratt & Whitney JT4A
Pratt & Whitney JT4A
|-See also:-External links:*...
(J75). In May 1956 TCA ordered Conway-powered DC-8s, followed by additional orders from Alitalia
Alitalia
Alitalia - Linee Aeree Italiane S.p.A. , in its later stages known as Alitalia - Linee Aeree Italiane S.p.A. in Extraordinary Administration, was the former Italian flag carrier...
and Canadian Pacific Air Lines, while the Conway powered 707 was ordered by BOAC
Boac
Boac may refer to:* Boac, Marinduque, a municipality in the Southern Philippines* Boac , an American rapper* British Overseas Airways Corporation, a former British state-owned airline...
, Lufthansa
Lufthansa
Deutsche Lufthansa AG is the flag carrier of Germany and the largest airline in Europe in terms of overall passengers carried. The name of the company is derived from Luft , and Hansa .The airline is the world's fourth-largest airline in terms of overall passengers carried, operating...
, Varig
Varig
VARIG was the first airline founded in Brazil, in 1927. From 1965 until 1990 it was Brazil's leading and almost only international airline...
and Air India
Air India
Air India is the flag carrier airline of India. It is part of the government of India owned Air India Limited . The airline operates a fleet of Airbus and Boeing aircraft serving Asia, Australia, Europe and North America. Its corporate office is located at the Air India Building at Nariman...
. RCo.10's development was so smooth that after delivering a small number for testing, further deliveries switched to the 17150 pound-forces (76,287 N) RCo.12, which was designed, built and tested before the airframes had finished their testing. These models also featured a distinctive scalloped silencer, and a thrust reverser that could provide up to 50% reverse thrust.
Although successful in this role, only sixty-nine 707's and DC-8s were built with the Conway, due largely to the delivery of the first US-built bypass engines, particularly the Pratt & Whitney JT3D
Pratt & Whitney JT3D
|-See also:-External links:*...
. Nevertheless the Conway was successful on these designs, and was the first commercial aero engine to be awarded clearance to operate for periods up to 10,000 hours between major overhaul.
Rolls continued working on the Conway, delivering the RCo.15. This was similar to the earlier RCo.12, but had a larger zeroth-stage along with a larger engine housing to fit it. This improved cruise fuel consumption by 3% while at the same time increasing take-off thrust to 18500 pound-forces (82,292.1 N). The designs were otherwise similar, and RCo.12's could be re-built into RCo.15's during overhauls.
Final versions
The final development of the Conway series was the RCo.42, designed specifically for the Vickers VC10Vickers VC10
The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...
. As the need for wing-embedded engines was long abandoned by this point, Rolls dramatically increased the zeroth-stage diameter to increase the bypass from about 25% to 60%, and further increasing thrust to 20250 pound-forces (90,076.5 N). First run in March 1961, it would be the most successful of all the Conways, powering all of the VC10 fleet, later models with the RCo.43.
Design
The RCo.12 Conway was an axial-flow turbofan with a low bypass ratio of about 25%. It had a seven-stage low-pressure compressor, the first six stages made of aluminium and the last of titanium. Behind this was the nine-stage high-pressure compressor, the first seven stages of titanium and the last two of steel. The bypass housing duct was also made of titanium. The combustion area consisted of ten cannular flame cans. The high-pressure compressor was driven by a single-stage turbine using hollow air-cooled blades, which was followed by the two-stage turbine powering the low-pressure compressor. Accessories were arranged around the front of the engine, leading to a minimum of increased diameter.The engine produced 17150 pound-forces (76,287 N) for takeoff, weighed 4500 pounds (2,041.2 kg) and had a specific fuel consumption of 0.712 at take-off thrust and 0.87 for cruise.
By 1968 a Hyfil carbon-fibre fan assembly was in service on Conways of the VC10s operated by BOAC
Boac
Boac may refer to:* Boac, Marinduque, a municipality in the Southern Philippines* Boac , an American rapper* British Overseas Airways Corporation, a former British state-owned airline...
Applications
- Boeing 707-420Boeing 707The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...
- Douglas DC-8-40Douglas DC-8The Douglas DC-8 is a four-engined narrow-body passenger commercial jet airliner, manufactured from 1958 to 1972 by the Douglas Aircraft Company...
- Handley Page VictorHandley Page VictorThe Handley Page Victor was a British jet bomber aircraft produced by the Handley Page Aircraft Company during the Cold War. It was the third and final of the V-bombers that provided Britain's nuclear deterrent. The other two V-bombers were the Avro Vulcan and the Vickers Valiant. Some aircraft...
- Vickers VC10Vickers VC10The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...
Engines on display
A preserved Rolls-Royce Conway engine is on public display at the Royal Air Force Museum CosfordRoyal Air Force Museum Cosford
The Royal Air Force Museum Cosford is a museum dedicated to the history of aviation, and the Royal Air Force in particular. The museum is a non-departmental public body sponsored by the Department for Culture, Media and Sport and a registered charity...
. A sectioned Conway is displayed as part of a stack of jet engines at the National Museum of Flight at East Fortune in Scotland. A Conway can also be found in the storage wing of the Canada Aviation and Space Museum.
Specifications (Conway)
See also
External links
- Conway - The Evolution of the First Rolls-Royce By-pass Turbojet a 1960 FlightFlight InternationalFlight International is a global aerospace weekly publication produced in the UK. Founded in 1909, it is the world's oldest continuously published aviation news magazine...
article on the Conway