Misplaced Pages

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158-460: The Rolls-Royce RB.80 Conway was the first turbofan jet engine to enter service. Development started at Rolls-Royce in the 1940s, but the design was used only briefly, in the late 1950s and early 1960s, before other turbofan designs replaced it. The Conway engine was used on versions of the Handley Page Victor , Vickers VC10 , Boeing 707-420 and Douglas DC-8-40 . The name "Conway" is

316-400: A barrel roll during practices for a display flight at Farnborough Airshow . Manoeuvrability was greatly enabled by the light controls, quick response of the aircraft, and the design of certain flight surfaces such as the infinitely-variable tail-mounted airbrake. The Victor was designed for flight at high subsonic speeds, although multiple instances have occurred in which the sound barrier

474-401: A free-fall nuclear weapon ), or over shorter ranges 20,000 lb (9,100 kg) of conventional bombs. No defensive weapons were to be carried, the aircraft relying on its speed and altitude to avoid opposing fighters. The similar OR.230 required a "long range bomber" with a 2,000 nautical miles (2,300 mi; 3,700 km) radius of action at a height of 50,000 ft (15,000 m),

632-506: A "Phase 2" bomber, to be followed by "Phase 3" Victors with the wingspan increased to 137 ft (42 m) and powered by Bristol Siddeley Olympus turbojets or Rolls-Royce Conway turbofans . The Sapphire 9 was cancelled and the heavily modified Phase 3 aircraft would have delayed introduction, so an interim "Phase 2A" Victor was proposed and accepted, to be powered by the Conway but with minimal modifications. The "Phase 2A" proposal became

790-553: A 5,000-pound-force (22,000 N) design was proposed, but over the next few months it was modified to evolve into a larger 9,250-pound-force (41,100 N) design in response to a need for a new engine to power the Mk.2 low-level version of the Vickers Valiant bomber. The go-ahead to start construction of this larger design was given in October, under the name RB.80 . During development it

948-575: A combination of radar , cameras, and other sensors. Prior to the introduction of Polaris, some had already been converted into tankers to replace Valiants; further conversions to tankers followed and some of these re-purposed Victors refuelled Vulcan bombers during the Black Buck raids of the Falklands War . The Victor was the last of the V-bombers to be retired from service on 15 October 1993. The Victor

1106-416: A considerably higher bypass ratio than the Conway. Nevertheless, the Conway was successful on those aircraft, and was the first commercial aero engine to be awarded an operational period of up to 10,000 hours between major overhauls. Due to the Conway, B707-420 take-offs were the loudest by jetliners on airports and over communities until Concorde entered service. However, the Conway was revolutionary, being

1264-507: A cruising speed of 575 miles per hour (925 km/h), and a maximum weight of 200,000 lb (91,000 kg) when fully loaded. Responses to OR.230 were received from Short Brothers , Bristol , and Handley Page ; the Air Ministry recognised that developing an aircraft to meet these stringent requirements would have been technically demanding and so expensive that the resulting bomber could be purchased only in small numbers. Realising that

1422-419: A discordant nature known as "buzz saw" noise. All modern turbofan engines have acoustic liners in the nacelle to damp their noise. They extend as much as possible to cover the largest surface area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests or in dedicated experimental test rigs. In the aerospace industry, chevrons are the "saw-tooth" patterns on

1580-410: A fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have

1738-516: A further 28 1,000 lb bombs to supplement the main bomb bay, but this option was not pursued. In addition to a range of free-fall nuclear bombs, later Victor B.2s operated as missile carriers for standoff nuclear missiles such as Blue Steel. Target information for Blue Steel could be input during flight, as well in advance of the mission. It was reported that, with intensive work, a B.2 missile carrier could revert to carrying free-fall nuclear weapons or conventional munitions within 30 hours. Like

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1896-426: A high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes). The latter engine is better for an aircraft that has to fly some distance, or loiter for

2054-416: A higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better specific fuel consumption (SFC). Some low-bypass ratio military turbofans (e.g. F404 , JT8D ) have variable inlet guide vanes to direct air onto

2212-481: A hose and drogue carried under each wing, while the bomb bay remained available for weapons. Handley Page worked day and night to convert these six aircraft, with the first being delivered on 28 April 1965, and 55 Squadron becoming operational in the tanker role in August 1965. While these six aircraft provided a limited tanker capability suitable for refuelling fighters, the Mk 20A wing hosereels delivered fuel at too low

2370-572: A long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low. The first production afterburning turbofan engine was the Pratt & Whitney TF30 , which initially powered the F-111 Aardvark and F-14 Tomcat . Low-bypass military turbofans include the Pratt & Whitney F119 , the Eurojet EJ200 ,

2528-652: A low-level high-speed approach supported by increasingly sophisticated ECMs was adopted in its place. The improved Victor B.2 started to be delivered in 1961, with the first B.2 Squadron, 139 Squadron , forming in February 1962, and a second, 100 Squadron , in May 1962. These were the only two bomber squadrons to form on the B.2, as the last 28 Victors on order were cancelled. The prospect of Skybolt ballistic missiles, with which each V-bomber could strike at two separate targets, meant that fewer bombers would be needed. The government

2686-407: A passive radar warning receiver, a metric radar jammer and communications jamming equipment. Streamlined fairings on the trailing edges of the wings that could house large quantities of defensive chaff / flares were also new additions. While trials were conducted with terrain-following radar and a side scan mode for the bombing and navigation radar, neither of these functions were integrated into

2844-401: A pound of thrust, more fuel is wasted in the faster propelling jet. In other words, the independence of thermal and propulsive efficiencies, as exists with the piston engine/propeller combination which preceded the turbojet, is lost. In contrast, Roth considers regaining this independence the single most important feature of the turbofan which allows specific thrust to be chosen independently of

3002-413: A production Victor XA917 flown by test pilot Johnny Allam inadvertently exceeded the speed of sound after Allam let the nose drop slightly at a high power setting. Allam noticed a cockpit indication of Mach 1.1 and ground observers from Watford to Banbury reported hearing a sonic boom . The Victor maintained stability throughout the event. Aviation author Andrew Brookes has claimed that Allam broke

3160-403: A pure-jet of the same thrust, and jet noise is no longer the predominant source. Turbofan engine noise propagates both upstream via the inlet and downstream via the primary nozzle and the by-pass duct. Other noise sources are the fan, compressor and turbine. Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise

3318-512: A rate to be suitable for refuelling bombers. Work therefore continued to produce a definitive three-point tanker conversion of the Victor Mk.1. Fourteen further B.1A and 11 B.1 were fitted with two permanently fitted fuel tanks in the bomb bay, and a high-capacity Mk 17 centreline hose dispenser unit with three times the fuel flow rate as the wing reels, and were designated K.1A and K.1 respectively. The remaining B.2 aircraft were not as suited to

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3476-652: A second squadron, 15 Squadron , forming before the end of the year. Four Victors, fitted with Yellow Astor reconnaissance radar, together with passive sensors, were used to equip a secretive unit, the Radar Reconnaissance Flight at RAF Wyton . The Victor bomber force continued to build up, with 57 Squadron forming in March 1959 and 55 Squadron in October 1960. At its height, the Victor was simultaneously operating with six squadrons of RAF Bomber Command. According to

3634-511: A sense of a crew unity was considered highly important; Victor crews would typically serve together for at least five years, and a similar approach was adopted with ground personnel. In order to maximise the operational lifespan of each aircraft, Victor crews typically flew a single five-hour training mission per week. Each crew member was required to qualify for servicing certificates to independently undertake inspection, refuelling and turnaround operations. In times of high international tension,

3792-460: A series of detachments of Victor B.1As was deployed to RAF Tengah , Singapore as a deterrent against Indonesia during the Borneo conflict , the detachments fulfilling a strategic deterrent role as part of Far East Air Force , while also giving valuable training in low-level flight and visual bombing. In September 1964, with the confrontation with Indonesia reaching a peak, the detachment of four Victors

3950-412: 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 bypass duct started after the seventh stage. The combustion area consisted of ten cannular flame cans . The high-pressure compressor

4108-657: A small cross-section, which limited the amount of bypass the engine could use. It nevertheless required higher power to support a 230,000 pounds (100,000 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 13,000 pounds-force (58,000 N). Construction of

4266-550: A static thrust of 4,320 lb (1,960 kg), and had a bypass ratio of 6:1. The General Electric TF39 became the first production model, designed to power the Lockheed C-5 Galaxy military transport aircraft. The civil General Electric CF6 engine used a derived design. Other high-bypass turbofans are the Pratt & Whitney JT9D , the three-shaft Rolls-Royce RB211 and the CFM International CFM56 ; also

4424-454: A target 1,500 nautical miles (2,800 km; 1,700 mi) from a base which may be anywhere in the world". A cruising speed of 500 knots (930 km/h; 580 mph) at heights between 35,000 ft (11,000 m) and 50,000 ft (15,000 m) was specified. The maximum weight when fully loaded ought not to exceed 100,000 lb (45,000 kg). The weapons load was to include a 10,000 lb (4,500 kg) "Special gravity bomb" (i.e.

4582-432: A tendency for the aircraft to pitch upwards during low-to-moderate Mach numbers. At low altitude, the Victor typically flew in a smooth and comfortable manner, in part due to its narrowness and flexibility of the crescent wing. One unusual flight characteristic of the early Victor was its self-landing capability; once lined up with the runway, the aircraft would naturally flare as the wing entered into ground effect while

4740-473: A turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A bypass ratio of 6, for example, means that 6 times more air passes through the bypass duct than the amount that passes through the combustion chamber. Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition BPR

4898-421: A turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system. The thrust ( F N ) generated by a turbofan depends on the effective exhaust velocity of the total exhaust, as with any jet engine, but because two exhaust jets are present

Rolls-Royce Conway - Misplaced Pages Continue

5056-496: A turbojet even though an extra turbine, a gearbox and a propeller are added to the turbojet's low-loss propelling nozzle. The turbofan has additional losses from its greater number of compressor stages/blades, fan and bypass duct. Froude, or propulsive, efficiency can be defined as: η f = 2 1 + V j V a {\displaystyle \eta _{f}={\frac {2}{1+{\frac {V_{j}}{V_{a}}}}}} where: While

5214-704: A turbojet which accelerates a smaller amount more quickly, which is a less efficient way to generate the same thrust (see the efficiency section below). The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio . Engines with more jet thrust relative to fan thrust are known as low-bypass turbofans , those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are high-bypass, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofans on combat aircraft. The bypass ratio (BPR) of

5372-413: A unit would jam. A separate hydraulic circuit was used for each of the following: landing gear, flaps, nose flaps, air brakes, bomb doors, wheel brakes, nose-wheel steering, ram-air-turbine air scoops. An AC electrical system and auxiliary power unit were significant additions to the later Victor B.2, electrical reliability being noticeably improved. To evade enemy detection and interception efforts,

5530-553: A variety of cameras, a bomb bay-mounted radar mapping system and air sampling equipment to detect particles released from nuclear testing . Designated Victor SR.2, a single aircraft could photograph the whole of the United Kingdom in a single two-hour sortie. Different camera configurations could be installed in the bomb bay, including up to four F49 survey cameras and up to eight F96 cameras could be fitted to take vertical or oblique daylight photography; nighttime photography required

5688-568: Is a British jet-powered strategic bomber developed and produced by Handley Page during the Cold War . It was the third and final V bomber to be operated by the Royal Air Force (RAF), the other two being the Vickers Valiant and the Avro Vulcan . Entering service in 1958, the Victor was initially developed as part of the United Kingdom's airborne nuclear deterrent , but it was retired from

5846-507: Is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading. For example,

6004-410: Is considerable potential for reducing fuel consumption for the same core cycle by increasing BPR.This is achieved because of the reduction in pounds of thrust per lb/sec of airflow (specific thrust) and the resultant reduction in lost kinetic energy in the jets (increase in propulsive efficiency). If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft

6162-430: Is due to the speed, temperature, and pressure of the exhaust jet, especially during high-thrust conditions, such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine's exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. To reduce the noise associated with jet flow,

6320-413: Is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR can also be quoted for lift fan installations where the fan airflow is remote from

6478-420: Is sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the inlet temperature of the high-pressure (HP) turbine rotor. To illustrate one aspect of how a turbofan differs from a turbojet, comparisons can be made at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if

Rolls-Royce Conway - Misplaced Pages Continue

6636-424: Is that combustion is less efficient at lower speeds. Any action to reduce the fuel consumption of the engine by increasing its pressure ratio or turbine temperature to achieve better combustion causes a corresponding increase in pressure and temperature in the exhaust duct which in turn cause a higher gas speed from the propelling nozzle (and higher KE and wasted fuel). Although the engine would use less fuel to produce

6794-411: Is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission. Unlike in the main engine, where stoichiometric temperatures in the combustor have to be reduced before they reach the turbine, an afterburner at maximum fuelling is designed to produce stoichiometric temperatures at entry to the nozzle, about 2,100 K (3,800 °R; 3,300 °F; 1,800 °C). At

6952-506: The Victor B.2 , with Conway RCo.11 engines providing 17,250 lbf (76.7 kN), which required enlarged intakes to increase the airflow to the engines, and the wingspan was increased to 120 ft (37 m). The B.2 also added a pair of retractable "elephant ear" intakes on the upper rear fuselage forward of the fin, to feed air to Ram Air Turbines (RAT) to provide electricity should an in-flight engine failure occur. The first flight of

7110-569: The Armstrong Siddeley Sapphire used by earlier models. For this role, Rolls-Royce designed an even larger model, the RCo.8 of 14,500 pounds-force (64,000 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

7268-472: The Bristol Olympus , and Pratt & Whitney JT3C engines, increased the overall pressure ratio and thus the thermodynamic efficiency of engines. They also had poor propulsive efficiency, because pure turbojets have a high specific thrust/high velocity exhaust, which is better suited to supersonic flight. The original low-bypass turbofan engines were designed to improve propulsive efficiency by reducing

7426-677: The General Electric F110 , the Klimov RD-33 , and the Saturn AL-31 , all of which feature a mixed exhaust, afterburner and variable area propelling nozzle. To further improve fuel economy and reduce noise, almost all jet airliners and most military transport aircraft (e.g., the C-17 ) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in

7584-603: 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

7742-469: The 1960s, the Victors were soon repainted in green/grey tactical camouflage to reduce visibility to ground observation; the same scheme was applied to subsequently converted tanker aircraft. The Victor's bomb bay was much larger than that of the Valiant and Vulcan, which allowed heavier weapon loads to be carried at the cost of range. As an alternative to the single "10,000 lb" nuclear bomb as required by

7900-421: The 1960s. Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use turboprops . Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust. The core (or gas generator) of

8058-475: The Air Ministry announced the aircraft's official name to be Victor . The prototypes performed well; however, design failings led to the loss of WB771 on 14 July 1954, when the tailplane detached whilst making a low-level pass over the runway at Cranfield , causing the aircraft to crash with the loss of the crew. Attached to the fin using three bolts, the tailplane was subjected to considerably more load than had been anticipated, causing fatigue cracking around

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8216-671: The Blue Danube nuclear weapon and later with the more powerful Yellow Sun weapon when it became available. Victors also carried U.S.-owned Mark 5 nuclear bombs (made available under the Project E programme) and the British Red Beard tactical nuclear weapon. A total of 24 were upgraded to B.1A standard by the addition of Red Steer tail warning radar in an enlarged tail-cone and a suite of radar warning receivers and electronic countermeasures (ECM) from 1958 to 1960. On 1 June 1956,

8374-576: The Conway-powered 707-420 was ordered by BOAC , Lufthansa , Varig , El Al and Air India . RCo.10's development was so smooth that after delivering a small number for testing, production deliveries switched to the 17,500-pound-force (78,000 N) RCo.12 , which was designed, built and tested before the airframes finished testing. Boeing's 707-420 featured a distinctive, scalloped exhaust nozzle (pictured above) incorporating noise suppression and mechanical and aerodynamic thrust reversal up to 50%, which

8532-734: The English spelling of the River Conwy , in Wales , in keeping with Rolls' use of river names for gas turbine engines. Alan Arnold Griffith had proposed a number of different bypass or turbofan 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 . However, simpler turbojet designs were prioritized during World War II for their use in military applications. Priorities changed dramatically at

8690-543: The Falklands, with approximately 1.1 million gal (5 million L) of fuel consumed in each mission. At the time, these missions held the record for the world's longest-distance bombing raids. The deployment of other assets to the theatre, such as the Hawker Siddeley Nimrod and Lockheed Hercules , required the support of the Victor tanker fleet, which had been temporarily relocated to RAF Ascension Island for

8848-470: The Soviet detection network. This tactic was employed in conjunction with the Victor's extensive onboard ECM to increase the chances of evasion. Whilst originally the Victor would have maintained high-altitude flight throughout a nuclear strike mission, rapid advances of the Soviet anti-aircraft warfare capabilities (exemplified by the downing of a U-2 from 70,000 ft in 1960) led to this tactic being abandoned:

9006-487: The U.S. Atomic Energy Act of 1946 (McMahon Act) prohibited the export of atomic knowledge, even to countries that had collaborated on the Manhattan Project . OR.1001 envisaged a weapon not to exceed 24 ft 2 in (7.37 m) in length, 5 ft (1.5 m) in diameter, 10,000 lb (4,500 kg) in weight, and suitable for release from 20,000 ft (6,100 m) to 50,000 ft (15,000 m). At

9164-488: The V-bombers would have dispersed and been maintained at a high state of readiness; if the order was given to deploy a nuclear strike, Victors at high readiness would have been airborne in under four minutes. British intelligence had estimated that the Soviets' radar network was capable of detecting the Victor at up to 200 miles away, so to avoid interception, the Victor would follow carefully planned routes to exploit weaknesses in

9322-587: The Victor B.2 prototype , serial number XH668 was made on 20 February 1959, and it had flown 100 hours by 20 August 1959, when it disappeared from radar, crashing into the sea off the Pembrokeshire coast during high-altitude engine tests carried out by the Aeroplane and Armament Experimental Establishment (A&AEE). Most of the wreckage had been recovered by November 1960, following an extensive search and recovery operation. The accident investigation concluded that

9480-562: The Victor B.2s on order would be fitted to carry two Skybolts. This plan was abandoned when the U.S. cancelled the Skybolt programme in 1963. With the move to low-level penetration missions, the Victors were fitted with air-to-air refuelling probes above the cockpit and received large underwing fuel tanks. Nine B.2 aircraft were converted for strategic reconnaissance purposes to replace Valiants which had been withdrawn due to wing fatigue, with delivery beginning in July 1965. These aircraft received

9638-508: The Victor was never permanently based with any units stationed overseas, temporary deployments were frequently conducted, often in a ceremonial capacity or to participate in training exercises and competitions. Victor squadrons were dispatched on several extended deployments to the Far East , and short term deployments to Canada were also conducted for training purposes. At one point during the early 1960s, South Africa showed considerable interest in

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9796-453: The Victor was outfitted with an extensive ECM suite which were operated by the air electronics officer (AEO), who had primary responsibility for the aircraft's electronics and communication systems. The ECM equipment could be employed to disrupt effective use of both active and passive radar in the vicinity of the aircraft, and to provide situational awareness for the crew. Enemy communications could also be jammed, and radar guided missiles of

9954-459: The acquisition of several bomber-configured Victors. Several of the Victor B.2s had been converted for Strategic Reconnaissance missions following the retirement of the Valiant in this capacity. In service, this type was primarily used in surveillance of the Atlantic Ocean and Mediterranean Seas , capable of surveying 400,000 square miles in an eight-hour mission; they were also used to sample

10112-464: The aerospace industry has sought to disrupt shear layer turbulence and reduce the overall noise produced. Fan noise may come from the interaction of the fan-blade wakes with the pressure field of the downstream fan-exit stator vanes. It may be minimized by adequate axial spacing between blade trailing edge and stator entrance. At high engine speeds, as at takeoff, shock waves from the supersonic fan tips, because of their unequal nature, produce noise of

10270-422: The afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume and increased flow rate when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but

10428-478: The ailerons, elevators and rudder, with no manual reversion which required duplication as back-up. Since the control surfaces were fully powered an artificial feel unit was provided, fed by ram air from the pitot in the nose. Pilot control movements were transmitted via a low-friction mechanical system to the flying control units. Duplication was provided on the premise that the single pilot's input would remain functional and that neither hydraulic motors nor screwjack on

10586-441: The aircraft is going forwards, leaving a very fast wake. This wake contains kinetic energy that reflects the fuel used to produce it, rather than the fuel used to move the aircraft forwards. A turbofan harvests that wasted velocity and uses it to power a ducted fan that blows air in bypass channels around the rest of the turbine. This reduces the speed of the propelling jet while pushing more air, and thus more mass. The other penalty

10744-536: The aircraft to be lost in a crash the following year . The RCo.11 was flown in the Victor on 20 February 1959. Boeing calculated that the Conway with a bypass of only 30% would increase the proposed 707-420's range by 8% above the otherwise identical 707-320 powered by Pratt & Whitney JT4A (J75) turbojets. That estimate proved optimistic; the actual range improvement was a maximum of 2%. In May 1956, TCA ordered Conway-powered DC-8-40s, followed by additional orders from Alitalia and Canadian Pacific Air Lines , while

10902-400: The aircraft were hidden under wooden framing and tarpaulins printed with "GELEYPANDHY / SOUTHAMPTON" to make it appear as a boat hull in transit. GELEYPANDHY was an anagram of "Handley Pyge", marred by a signwriter's error. On 24 December 1952, piloted by Handley Page's chief test pilot Hedley Hazelden , WB771 made its maiden flight, which lasted for a total of 17 minutes. Ten days later,

11060-471: The average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the Pratt & Whitney PW1000G , which entered commercial service in 2016, attains 12.5:1. Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improvements in blade aerodynamics can reduce

11218-416: The bolt holes. This led to the bolts loosening and failing in shear. Stress concentrations around the holes were reduced by adding a fourth bolt. The potential for flutter due to shortcomings in the design of the fin/tailplane joint was also reduced by shortening the fin. Additionally, the prototypes were tail heavy due to the lack of equipment in the nose; this was remedied by adding large ballast weights to

11376-465: The campaign. The Victor also undertook several reconnaissance missions over the South Atlantic. These missions provided valuable intelligence for the retaking of South Georgia by British forces. Following the invasion of Kuwait by neighbouring Iraq in 1991, a total of eight Victor K.2s were deployed to Bahrain to provide in-flight refuelling support to RAF and other coalition aircraft during

11534-411: The chaff. The fairings behaved like " Küchemann carrots". These were anti-shock bodies which reduced wave drag at transonic speeds (see area rule ). Handley Page proposed to build a further refined "Phase 6" Victor, with more fuel and capable of carrying up to four Skybolt (AGM-48) ballistic missiles on standing airborne patrols, but this proposal was rejected although it was agreed that some of

11692-488: The compressor. Compressor stages run at their maximum efficiency when spinning at a specific speed for any given input air pressure - in a perfect compressor each stage would run at a separate speed. The multi-spool design, first used on the Bristol Olympus turbojet, is a compromise, the compressor being separated into "spools" designed to operate closer to most efficient speed, driven by separate turbines via concentric shafts. Two- and three-spool designs are common; beyond that

11850-455: The end of 1968. The RAF had experienced intense demand on its existing aerial refuelling tanker fleet, and its existing fleet of Victor B.1 tankers that had been converted earlier were due to be retired in the 1970s, so it was decided that the stored Victor B.2Rs would be converted to tankers also. Handley Page prepared a modification scheme that would see the Victors fitted with tip tanks, the structure modified to limit further fatigue cracking in

12008-553: The end of the war and in 1946 Rolls-Royce agreed that existing engines like the Rolls-Royce Avon were advanced enough to enable a start to work on more advanced concepts like bypass. Griffith, who by then had become Chief Engineer at Rolls-Royce , suggested building a purely experimental bypass design using parts of the Avon and another experimental jet engine, the AJ.25 Tweed . In April 1947,

12166-445: The engine and doesn't flow past the engine core. Considering a constant core (i.e. fixed pressure ratio and turbine inlet temperature), core and bypass jet velocities equal and a particular flight condition (i.e. Mach number and altitude) the fuel consumption per lb of thrust (sfc) decreases with increase in BPR. At the same time gross and net thrusts increase, but by different amounts. There

12324-427: The engine must generate enough power to drive the fan at its rated mass flow and pressure ratio. Improvements in turbine cooling/material technology allow for a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core, potentially improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce

12482-416: The engine, from the gas generator, to a ducted fan which produces a second, additional mass of accelerated air. The transfer of energy from the core to bypass air results in lower pressure and temperature gas entering the core nozzle (lower exhaust velocity), and fan-produced higher pressure and temperature bypass-air entering the fan nozzle. The amount of energy transferred depends on how much pressure rise

12640-460: The era were also reportedly rendered ineffective. The Victor B.2 featured an extended area located around the base of the tail fin which contained cooling systems and some of the ECM equipment. Some of the ECM equipment which initially saw use on the Victor, such as the original chaff dispenser and Orange Putter tail warning radar, had been developed for the earlier English Electric Canberra bomber and

12798-516: The exhaust velocity to a value closer to that of the aircraft. The Rolls-Royce Conway , the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine. Civilian turbofan engines of the 1960s, such as the Pratt & Whitney JT8D and the Rolls-Royce Spey , had bypass ratios closer to 1 and were similar to their military equivalents. The first Soviet airliner powered by turbofan engines

12956-463: The fallout from French nuclear tests conducted in the South Pacific . Originally reconnaissance Victors were equipped for visual reconnaissance; it was found to be cheaper to assign Canberra light bombers to this duty and the cameras were removed in 1970. Subsequently, radar-based reconnaissance was emphasised in the type's role. The reconnaissance Victors remained in use until 1974 when they followed

13114-411: The fan is designed to produce (fan pressure ratio). The best energy exchange (lowest fuel consumption) between the two flows, and how the jet velocities compare, depends on how efficiently the transfer takes place which depends on the losses in the fan-turbine and fan. The fan flow has lower exhaust velocity, giving much more thrust per unit energy (lower specific thrust ). Both airstreams contribute to

13272-450: The first fan rotor stage. This improves the fan surge margin (see compressor map ). Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area exit nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, large volumes of fuel are burnt in

13430-498: The first turbofan, and the first commercial engine, equipped with internally air-cooled turbine blades, which partially accounted for its high efficiency and an extremely high exhaust temperature of 1,247 °F (675 °C). Final development of the Conway first involved the RCo.42 , designed specifically for the Vickers VC10 . As the need for wing-embedded engines was long abandoned by this point, Rolls-Royce dramatically increased

13588-471: The fitting of F89 cameras. Prior to the demise of the Valiant as a tanker, a trial installation of refuelling equipment was carried out using the Victor, including: overload bomb-bay tanks, underwing tanks, refuelling probe and jettisonable de Havilland Spectre Assisted Take-Off units. The aircraft involved in the trials, B.1 "XA930", carried out successful trials at Boscombe Down at very high all-up weights with relatively short field length take-offs. With

13746-614: The flight controls. In the event of engine flameout RATs would enable the crew to keep control of the aircraft until the engines could be relit. The Victor was commonly described as having good handling and excellent performance, along with favourable low speed flight characteristics. During the flight tests of the first prototype, the Victor proved its aerodynamic performance, flying up to Mach 0.98 without handling or buffeting problems; there were next to no aerodynamic changes between prototype and production aircraft. Production aircraft featured an automated nose-flap operation to counteract

13904-483: The fuel consumption of the turbojet. It achieves this by pushing more air, thus increasing the mass and lowering the speed of the propelling jet compared to that of the turbojet. This is done mechanically by adding a ducted fan rather than using viscous forces. A vacuum ejector is used in conjunction with the fan as first envisaged by inventor Frank Whittle . Whittle envisioned flight speeds of 500 mph in his March 1936 UK patent 471,368 "Improvements relating to

14062-400: The gas generator cycle. The working substance of the thermodynamic cycle is the only mass accelerated to produce thrust in a turbojet which is a serious limitation (high fuel consumption) for aircraft speeds below supersonic. For subsonic flight speeds the speed of the propelling jet has to be reduced because there is a price to be paid in producing the thrust. The energy required to accelerate

14220-443: The gas inside the engine (increase in kinetic energy) is expended in two ways, by producing a change in momentum ( i.e. a force), and a wake which is an unavoidable consequence of producing thrust by an airbreathing engine (or propeller). The wake velocity, and fuel burned to produce it, can be reduced and the required thrust still maintained by increasing the mass accelerated. A turbofan does this by transferring energy available inside

14378-429: The gross thrust of the engine. The additional air for the bypass stream increases the ram drag in the air intake stream-tube, but there is still a significant increase in net thrust. The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed and gets closer to the ideal Froude efficiency . A turbofan accelerates a larger mass of air more slowly, compared to

14536-472: The ground or in the air as an emergency power supply if the engine-driven generators failed. It also reduced the need for some ground support equipment. Two turbine-driven alternators, otherwise known as ram air turbines (RATs), had been introduced on the B.2 to provide emergency power in the event of electrical power being lost. Retractable scoops in the rear fuselage would open to feed ram air to them enabling them to generate sufficient electrical power to operate

14694-409: The high-bypass type, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofan engines with bypass and core mixing before the afterburner. Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit. The turbofan was invented to improve

14852-474: The hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between turbojets , which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less). Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gives significant fuel savings over

15010-456: The idea. Rolls-Royce responded by designing an even larger model of the Conway, the 16,500 pounds-force (73,000 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 the modified prototype Avro Vulcan VX770 on 9 August 1957 only for

15168-409: The inlet to the Conway engine, together with those for commercial Avon and Spey installations, was the subject of a patent infringement claim against Rolls-Royce by Rateau, a French manufacturer of steam turbines and automobile superchargers . Société pour l’exploitation des appareils Rateau of La Courneuve , who alleged the inlets infringed two of their expired 1939 patents. The patent stated that

15326-553: The intake, by its diffusing internal shape, determines the speed of the air entering the engine compressor. Since the Conway in the Boeing 707, and the other Rolls-Royce engines, had diffusing intakes, Rateau expected to be compensated for every engine made, as well as stopping all future production. Although Rateau's claim was only against Rolls-Royce, its understanding of the purpose of an intake applied to any jet engine installation. Witnesses for Rolls-Royce, including Frank Whittle, convinced

15484-403: The judge that an intake did not produce the effect claimed and that the claim was "speculative" because, by 1939, no axial-flow aircraft jet engine had been built and that earlier patents from Frank Whittle and others had already considered the design of the intakes. Data from Jane's All The World's Aircraft 1969-70 Comparable engines Related lists Turbofan The ratio of

15642-472: 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

15800-602: The low-level mission profile that the RAF had adopted for carrying out strategic bombing missions as the Vulcan with its stronger delta wing. This, combined with the switch of the nuclear deterrent from the RAF to the Royal Navy (with the Polaris missile ) meant that the Victors were declared surplus to requirements. Hence, 24 B.2 were modified to K.2 standard. Similar to the K.1/1A conversions,

15958-478: The majority of likely targets would not require such a long range, a less demanding specification for a medium-range bomber, Air Ministry Specification B.35/46 was issued. This demanded the ability to carry the same 10,000 lb bomb-load to a target 1,500 nautical miles (2,800 km; 1,700 mi) away at a height of 45,000–50,000 ft (14,000–15,000 m) at a speed of 575 mph (925 km/h). The design proposed by Handley Page in response to B.35/46

16116-468: The mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as the bypass ratio . The engine produces thrust through a combination of these two portions working together. Engines that use more jet thrust relative to fan thrust are known as low-bypass turbofans ; conversely those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are of

16274-486: The mechanical complexity is too great. 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 by the Ministry of Supply designation as the RCo.2 , design work was completed in January 1950 and the first example ran for the first time in July 1952 at 10,000 pounds-force (44,000 N) thrust. By this time,

16432-417: The mechanical power produced by the turbine. In a bypass design, extra turbines drive a ducted fan that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to turboprops in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for

16590-512: The nose as a result of the Blue Steel installation. Coincidentally, Peter White, a senior aerodynamicist attended a symposium in Brussels and learned of Whitcomb's conical bodies set on the top of a wing which would add volume while reducing wave drag. However, the added skin friction drag meant an overall slight drag increase. So large streamlined fairings were added to the top of the each wing to hold

16748-408: The nuclear delivery role, the Victor was finished in an all-over anti-flash white colour scheme, designed to protect the aircraft against the damaging effects of a nuclear detonation. The white colour scheme was intended to reflect heat away from the aircraft; paler variations of RAF's roundels were also applied for this same reason. When the V-bombers were assigned to the low-level approach profile in

16906-520: The nuclear mission in 1968, following the discovery of fatigue cracks which had been exacerbated by the RAF's adoption of a low-altitude flight profile to avoid interception , and due to the pending introduction of the Royal Navy's submarine-launched Polaris missiles in 1969. With the nuclear deterrent mission relinquished to the Royal Navy a large V-bomber fleet could not be justified. A number of Victors were modified for strategic reconnaissance, using

17064-474: The number of extra compressor stages required, and variable geometry stators enable high-pressure-ratio compressors to work surge-free at all throttle settings. The first (experimental) high-bypass turbofan engine was the AVCO-Lycoming PLF1A-2, a Honeywell T55 turboshaft-derived engine that was first run in February 1962. The PLF1A-2 had a 40 in diameter (100 cm) geared fan stage, produced

17222-447: The onboard electromechanical analogue bomb-aiming apparatus. Some of the navigation and targeting equipment was either directly descended from, or shared concepts with, those used on Handley Page's preceding Halifax bomber. Operationally, the accuracy of the bomb-aiming system proved to be limited to roughly 400 yards, which was deemed sufficient for high-level nuclear strike operations. The Victor had fully powered flying controls for

17380-440: The operational doctrine developed by the RAF, in the circumstance of deploying a large-scale nuclear strike, each Victor would have operated entirely independently; the crews would conduct their mission without external guidance and be reliant upon the effectiveness of their individual tactics to reach and successfully attack their assigned target; thus great emphasis was placed on continuous crew training during peacetime. Developing

17538-428: The operational fleet. The Victor B.1 was powered by four Armstrong Siddeley Sapphire turbojet engines. The engines were embedded in pairs in the wing roots. Because of the mid wing position, the tail was mounted at the tip of the fin to keep clear of the jet efflux. Sapphire engines installed in the Victor suffered 'centre-line closure' failures flying in dense cloud or heavy rain flying in the tropics. The Victor B.2

17696-556: The other two V-Bombers, the Victor made use of the Navigational and Bombing System (NBS); a little-used optical sight had also been installed upon early aircraft. For navigation and bomb-aiming purposes, the Victor employed several radar systems. These included the H2S radar , developed from the first airborne ground-scanning radar, and the Green Satin radar . Radar information was inputted into

17854-552: The programme. Two HP.80 prototypes, WB771 and WB775 , were built. WB771 had been partially assembled at the Handley Page factory at Radlett airfield when the Ministry of Supply decided the runway was too short for the first flight. The aircraft parts were transported by road to RAF Boscombe Down where they were assembled for the first flight; bulldozers were used to clear the route and create paths around obstacles. Sections of

18012-437: The proposal matured, a high-mounted, full tailplane was adopted instead. The profile and shaping of the crescent wing was subject to considerable fine-tuning and alterations throughout the early development stages, particularly to counter unfavourable pitching behaviour in flight. The HP.80 and Avro's Type 698 were chosen as the best two of the proposed designs to B.35/46, and orders for two prototypes of each were placed. It

18170-414: The propulsion of aircraft", in which he describes the principles behind the turbofan, although not called as such at that time. While the turbojet uses the gas from its thermodynamic cycle as its propelling jet, for aircraft speeds below 500 mph there are two penalties to this design which are addressed by the turbofan. Firstly, energy is wasted as the propelling jet is going much faster rearwards than

18328-476: The prototype V-1000 was well underway at Vickers Armstrong's 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. The Conway was saved once again when it was selected to power the Handley Page Victor B.2 variant, replacing

18486-515: The prototypes. Production Victors had a lengthened nose to move the crew escape door further from the engine intakes as the original position was considered too dangerous as an emergency exit in flight. The lengthened nose also improved the center of gravity range. Production B.1 Victors were powered by the Armstrong Siddeley Sapphire ASSa.7 turbojets rated at 11,000  lbf (49  kN ), and were initially armed with

18644-399: The same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where

18802-455: The same level as the rest of the crew, due to a large pressurised compartment that extended all the way to the nose. As with the other V-bombers, only the pilots were provided with ejection seats ; the three systems operators relying on "explosive cushions" inflated by a CO 2 bottle that would help them from their seats, but despite this, escape for them would have still been very unlikely in most emergency situations. While assigned to

18960-568: The same time, the Air Ministry drew up requirements for bombers to replace the piston-engined heavy bombers such as the Avro Lancaster and the new Avro Lincoln which equipped RAF Bomber Command . In January 1947, the Ministry of Supply distributed Specification B.35/46 to aviation companies to satisfy Air Staff Operational Requirement OR.229 for "a medium range bomber landplane capable of carrying one 10,000 lb (4,500 kg) bomb to

19118-510: The smaller TF34 . More recent large high-bypass turbofans include the Pratt & Whitney PW4000 , the three-shaft Rolls-Royce Trent , the General Electric GE90 / GEnx and the GP7000 , produced jointly by GE and P&W. The Pratt & Whitney JT9D engine was the first high bypass ratio jet engine to power a wide-body airliner. Handley Page Victor The Handley Page Victor

19276-502: The sole requirement for bypass is to provide cooling air. This sets the lower limit for BPR and these engines have been called "leaky" or continuous bleed turbojets (General Electric YJ-101 BPR 0.25) and low BPR turbojets (Pratt & Whitney PW1120). Low BPR (0.2) has also been used to provide surge margin as well as afterburner cooling for the Pratt & Whitney J58 . Propeller engines are most efficient for low speeds, turbojet engines for high speeds, and turbofan engines between

19434-436: The sound barrier knowingly to demonstrate the Victor's higher speed capability compared to the earlier V-bombers. The Victor was the largest aircraft to have broken the sound barrier at that time. The RAF required its bombers to be capable of higher operational ceilings, and numerous proposals were considered for improved Victors. Initially, Handley Page proposed using 14,000 lbf (62 kN) Sapphire 9 engines to produce

19592-404: The specification, the bomb bay was designed to carry several conventional armaments, including a single 22,000 lb (10,000 kg) Grand Slam or two 12,000 lb (5,400 kg) Tallboy earthquake bombs , up to forty-eight 1,000 lb (450 kg) bombs or thirty-nine 2,000 lb (910 kg) sea mines. One proposed addition to the Victor were underwing panniers capable of carrying

19750-453: The standard bombers into the tanker conversion line; a handful of modified Avro Vulcans assumed the maritime radar reconnaissance role in their place. Both the Victor and the Vulcan, played a high-profile role during the 1982 Falklands War. In order to cross the distance of the South Atlantic, a single Vulcan required refuelling several times from Victor tankers. A total of three bombing missions were flown against Argentine forces deployed to

19908-468: The starboard pitot head had failed, causing the flight control system to force the aircraft into an unrecoverable dive. Minor changes resolved the problem, allowing the B.2 to enter service in February 1962. A total of 21 B.2 aircraft were upgraded to the B.2R standard with Conway RCo.17 engines (20,600 lbf or 92 kN thrust) and facilities to carry a Blue Steel stand-off nuclear missile . Anti-radar chaff storage had to be relocated from under

20066-614: The subsequent 1991 Gulf War . RAF strike aircraft such as the Panavia Tornado would frequently make use of the tanker to refuel prior to launching cross-border strikes inside Iraq. The remaining Victor fleet was retired in 1993, at which point it had been the last of the three V-bombers in operational service. A total of four Victors have survived and are on display in the United Kingdom. None are flightworthy. A fifth airframe, Victor K.2 XH673 : A K.2 served as Gate guardian at RAF Marham when retired in 1993, but in early 2020 she

20224-484: The tail continued to sink, giving a cushioned landing without any command or intervention by the pilot. However, this characteristic was considered to be of no special advantage according to an assessment of the second prototype by the Aeroplane and Armament Experimental Establishment. The Victor has been described as an agile aircraft, atypical for a large bomber aircraft; in 1958, a Victor had performed several loops and

20382-440: The tanker role until withdrawn in October 1993. The Victor was a futuristic-looking, streamlined aircraft, with four turbojet (later turbofan) engines buried in the thick wing roots. Distinguishing features of the Victor were its highly swept T-tail with considerable dihedral on the tail planes, and a prominent chin bulge that contained the targeting radar , nose landing gear unit and an auxiliary bomb aimer 's position. It

20540-520: The technology and materials available at the time. The first turbofan engine, which was only run on a test bed, was the German Daimler-Benz DB 670 , designated the 109-007 by the German RLM ( Ministry of Aviation ), with a first run date of 27 May 1943, after the testing of the turbomachinery using an electric motor, which had been undertaken on 1 April 1943. Development of the engine

20698-497: The thrust equation can be expanded as: F N = m ˙ e v h e − m ˙ o v o + B P R ( m ˙ c ) v f {\displaystyle F_{N}={\dot {m}}_{e}v_{he}-{\dot {m}}_{o}v_{o}+BPR\,({\dot {m}}_{c})v_{f}} where: The cold duct and core duct's nozzle systems are relatively complex due to

20856-665: The trailing edges of some jet engine nozzles that are used for noise reduction . The shaped edges smooth the mixing of hot air from the engine core and cooler air flowing through the engine fan, which reduces noise-creating turbulence. Chevrons were developed by GE under a NASA contract. Some notable examples of such designs are Boeing 787 and Boeing 747-8  – on the Rolls-Royce Trent 1000 and General Electric GEnx engines. Early turbojet engines were not very fuel-efficient because their overall pressure ratio and turbine inlet temperature were severely limited by

21014-428: The turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an overall pressure ratio increase. The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at

21172-476: The two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner. Most of the air flow through a high-bypass turbofan is lower-velocity bypass flow: even when combined with the much-higher-velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity. Therefore, turbofan engines are significantly quieter than

21330-418: The two. Turbofans are the most efficient engines in the range of speeds from about 500 to 1,000 km/h (270 to 540 kn; 310 to 620 mph), the speed at which most commercial aircraft operate. In a turbojet (zero-bypass) engine, the high temperature and high pressure exhaust gas is accelerated when it undergoes expansion through a propelling nozzle and produces all the thrust. The compressor absorbs

21488-510: The use of two separate exhaust flows. In high bypass engines, the fan is situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core . The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke. In low bypass engines

21646-554: The wing decreased in three distinct steps from the root to the tip, to ensure a constant critical Mach number across the entire wing and consequently a high cruise speed. The other parts of the aircraft which accelerate the flow, the nose and tail, were also designed for the same critical mach number so the shape of the HP.80 had a constant critical mach number all over. Early work on the project included tailless aircraft designs, which would have used wing-tip vertical surfaces instead; however as

21804-469: The wing, which was to have been fitted with tip fuel tanks to reduce wing fatigue, had 18 inches removed from each tip instead and the bomb aimer's nose glazing was replaced with metal. During 1982, the glazing was reintroduced on some aircraft, the former nose bomb aimer's position having been used to mount F95 cameras in order to perform reconnaissance missions during the Falklands War . The K.2 could carry 91,000 lb (41,000 kg) of fuel. It served in

21962-455: The wings, and ejection seats provided for all six crewmembers. The Ministry of Defence delayed signing the order for conversion of the B2s until after Handley Page went into liquidation . The contract for conversion was instead awarded to Hawker Siddeley , who produced a much simpler conversion proposal, with the wingspan shortened to reduce wing bending stress and hence extend airframe life. While

22120-450: The withdrawal of the Valiant because of metal fatigue in December 1964 the RAF had no flight-refuelling capability, so the B.1/1A aircraft, by then surplus in the strategic bomber role, were refitted for this duty. To get some tankers into service as quickly as possible, six B.1A aircraft were converted to B(K).1A standard (later redesignated B.1A (K2P) ), receiving a two-point system with

22278-676: The world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in Project Apollo as the powerplant for the Lunar Landing Research Vehicle . A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan behind inlet guide vanes, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to ensure there

22436-500: The zero-stage diameter to increase the bypass from about 30% to 60%. Other major revisions were incorporated, primarily in the low-pressure compressor. First run was in March 1961. Takeoff rating was 20,370 pounds-force (90,600 N). For the Super VC10, the last model was the RCo.43 , rated at 21,800 pounds-force (97,000 N). The RCo.12 Conway was an axial-flow turbofan with a low bypass of about 30% or bypass ratio of 0.3:1. It had

22594-599: Was abandoned with its problems unsolved, as the war situation worsened for Germany. Later in 1943, the British ground tested the Metrovick F.3 turbofan, which used the Metrovick F.2 turbojet as a gas generator with the exhaust discharging into a close-coupled aft-fan module comprising a contra-rotating LP turbine system driving two co-axial contra-rotating fans. Improved materials, and the introduction of twin compressors, such as in

22752-408: Was already considered to be nearly obsolete by the time the Victor entered service. Significant improvements and alterations were made to the avionics and ECM suites, as effective ECMs had been deemed critical to the Victor's role;. For example, the introduction of the more capable Red Steer tail warning radar . The introduction of the Victor B.2 was accompanied by several new ECM systems, including

22910-454: Was also unhappy with Sir Frederick Handley Page 's resistance to its pressure to merge his company with competitors. Following Skybolt's cancellation, Victor B.2s were retrofitted as carrier aircraft for the Blue Steel standoff nuclear missile. The introduction of standoff weapons and the switch to low-level flight in order to evade radar detection were said to be decisive factors in the successful penetration of enemy territory. In 1964–1965,

23068-569: Was broken. During development of the Victor B.2, the RAF had stressed the concept of tactical manoeuvrability, which led to much effort in development being given to increasing the aircraft's height and range performance. The Victor was the last of the V bombers to enter service, with deliveries of B.1s to No. 232 Operational Conversion Unit RAF based at RAF Gaydon , Warwickshire taking place in late 1957. The first operational bomber squadron, 10 Squadron , formed at RAF Cottesmore in April 1958, with

23226-416: Was decided to further improve the basic design by adding another feature then becoming common, a "two spool" compressor arrangement. Earlier engines generally consisted of a series of compressor stages connected via a shaft to one or more turbine stages, with the burners between them arranged around the shaft. Although this arrangement is mechanically simple, it has the disadvantage of lowering the efficiency of

23384-629: Was derived from the General Electric J85/CJ610 turbojet 2,850 lbf (12,700 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 , with about a 50% increase in thrust to 4,200 lbf (19,000 N). The CF700 was the first small turbofan to be certified by the Federal Aviation Administration (FAA). There were at one time over 400 CF700 aircraft in operation around

23542-450: Was developed and supplied by Rolls-Royce. Douglas developed the DC-8's reverser-suppressor nozzle to work in conjunction with a variable ejector, which provided necessary, additional noise suppression. Although successful in this role, only 37 707s and 32 DC-8s were fitted with the Conway, due largely to delivery of the Pratt & Whitney JT3D : this was the first US-built bypass engine and had

23700-556: 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 to minimise overall diameter. The RCo.12 produced 17,500 pounds-force (78,000 N) for takeoff, weighed 4,544 pounds (2,061 kg) dry and had a specific fuel consumption of 0.725 at takeoff and 0.874 for typical cruise. In 1968, Hyfil carbon-fibre fan blades were installed on Conways of VC10s operated by BOAC . In November, 1966,

23858-468: Was given the Handley Page HP.88 designation. The HP.88 crashed on 26 August 1951 after completing only about thirty flights and little useful data was gained during its brief two months of existence. By the time the HP.88 was ready, the HP.80 wing had changed such that the former was no longer representative. The design of the HP.80 had sufficiently advanced that the loss of the HP.88 had little effect on

24016-424: Was given the internal designation of HP.80. To achieve the required performance, Handley Page's aerodynamicist Dr. Gustav Lachmann and his deputy, Godfrey Lee developed a crescent-shaped swept wing for the HP.80. Aviation author Bill Gunston described the Victor's compound-sweep crescent wing as having been "undoubtedly the most efficient high-subsonic wing on any drawing board in 1947". The sweep and chord of

24174-436: Was originally required by the specification that the whole nose section could be detached at high altitudes to act as an escape pod, but the Air Ministry abandoned this requirement in 1950. The Victor had a five-man crew, comprising the two pilots seated side by side and three rearward-facing crew, these being the navigator/plotter, the navigator/radar operator, and the air electronics officer (AEO). The Victor's pilots sat at

24332-538: Was powered by the newer Rolls-Royce Conway turbofan which at one point was the most powerful non- afterburning engine outside the Soviet Union. The Conway had significantly higher thrust than the Sapphire engine in the B.1. The Victor B.2 had a Blackburn Artouste auxiliary power unit (AAPU) installed in the starboard wing root. It provided high-pressure air for starting the engines, and also provided electrical power on

24490-430: Was prepared for rapid dispersal, with two aircraft loaded with live conventional bombs and held on one-hour readiness, ready to fly operational sorties. However, they were never required to fly combat missions and the high readiness alert finished at the end of the month. Following the discovery of fatigue cracks, developing due to their low-altitude usage, the B.2R strategic bombers were retired and placed in storage by

24648-493: Was recognised, however, that there were many unknowns associated with both designs, and an order was also placed for Vickers' design, which became the Valiant . Although not fully meeting the requirements of the specification, the Valiant design posed little risk of failure and could therefore reach service earlier. The HP.80's crescent wing was tested on a ⅓-scale glider , the HP.87, and a heavily modified Supermarine Attacker , which

24806-539: Was replaced by Vickers VC10 and Lockheed Tristar tankers. The origin of the Victor and the other V bombers is linked to the early British atomic weapons programme and nuclear deterrent policies that were developed after the Second World War . The atom bomb programme formally began with Air Staff Operational Requirement OR.1001 issued in August 1946, which anticipated a government decision in January 1947 to authorise research and development work on atomic weapons;

24964-568: Was the Tupolev Tu-124 introduced in 1962. It used the Soloviev D-20 . 164 aircraft were produced between 1960 and 1965 for Aeroflot and other Eastern Bloc airlines, with some operating until the early 1990s. The first General Electric turbofan was the aft-fan CJ805-23 , based on the CJ805-3 turbojet. It was followed by the aft-fan General Electric CF700 engine, with a 2.0 bypass ratio. This

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