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114-413: TPP involves combining as a single package for the procurement a number of related requirements including the design, development, production and support of major systems. This concept was a "pendulum reaction" to the prior cost reimbursement policies in major weapon systems. Total Package Procurement was not successful and was abandoned shortly after MacNamara left office. TPP is a method of procuring at

228-577: A T-tail , while the designs by Boeing and Douglas had conventional tails. The Air Force considered Boeing's design to be better than that of Lockheed, but Lockheed's proposal was the lowest total-cost bid. Lockheed was selected as the winner in September 1965, then awarded a contract in December 1965. General Electric's TF39 engine was selected in August 1965 to power the new transport plane. At

342-653: A 30% shorter takeoff, a 38% higher climb rate to initial altitude, an increased cargo load and a longer range. Upgraded C-5s are designated C-5M Super Galaxy . Lockheed also planned a civilian version of the C-5 Galaxy, the L-500 , the company designation also used for the C-5 itself. Both passenger and cargo versions of the L-500 were designed. The all-passenger version would have been able to carry up to 1,000 travelers, while

456-569: A cargo load trainer at Lackland AFB, Texas, and one was sent to the Warner Robins Air Logistics Center (WR-ALC) for tear down and inspection to evaluate structural integrity and estimate the remaining life for the fleet. The U.S. Air Force began to receive refitted C-5M aircraft in December 2008. Full production of C-5Ms began in the summer of 2009. In 2009, the Congressional ban on the retirement of C-5s

570-754: A civilian jet liner, the Lockheed L-1011 . The U.S. government gave loans to Lockheed to keep the company operational. In the early 1970s, NASA considered the C-5 for the Shuttle Carrier Aircraft role, to transport the Space Shuttle to Kennedy Space Center . However, they rejected it in favor of the Boeing 747 , in part due to the 747's low-wing design. In contrast, the Soviet Union chose to transport its shuttles using

684-434: 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 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

798-419: 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

912-410: 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

1026-400: A ground stop for even the most routine long-distance flights. We spent a lot of money to make it capable of operating from unfinished airstrips near the front lines, when we never needed that capability or had any intention to use it. Robert F. Dorr, aviation historian Aircraft weight was a serious issue during design and development. At the time of the first flight, the weight was below

1140-426: 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

1254-619: A higher expected operating cost. The plan was canceled in favor of the purchase of more C-17s. The specifications of the C-5D were later used in the C-5M upgrade program. Following a study showing that 80% of the C-5 airframe's service life was remaining, Air Mobility Command (AMC) began an aggressive program to modernize all remaining C-5Bs and C-5Cs and many of the C-5As. The C-5 Avionics Modernization Program (AMP) began in 1998 and includes upgrading

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1368-416: 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

1482-590: 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 ,

1596-512: A mix of palletized cargo and vehicles. The nose and aft cargo-bay doors open the full width and height of the cargo bay to maximize efficient loading of oversized equipment. Full-width ramps enable loading double rows of vehicles from either end of the cargo hold. The C-5 Galaxy is capable of moving nearly every type of military combat equipment, including such bulky items as the Army armored vehicle launched bridge , at 74 short tons (67 t), from

1710-619: A new version of the C-5, the C-5B, in July 1982, to expand airlift capacity. The first C-5B was delivered to Altus Air Force Base in January 1986. In April 1989, the last of 50 C-5B aircraft was added to the 77 C-5As in the Air Force's airlift force structure. The C-5B includes all C-5A improvements and numerous additional system modifications to improve reliability and maintainability. In 1998,

1824-403: 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

1938-773: A similar climate as to their acquisition of F-14 Tomcat fighters. However, no C-5s were ordered by Iran, and the prospect was firmly halted by the Iranian Revolution in 1979 when the Imperial State of Iran was replaced by the Islamic State of Iran . As part of President Ronald Reagan 's military policy, funding was made available for expansion of the USAF's airlift capability. With the C-17 program still some years from completion, Congress approved funding for

2052-592: A smaller turning radius, and rotates 90° after takeoff before being retracted. "Kneeling" landing gear permits lowering the aircraft when parked, thereby presenting the cargo deck at truck-bed height to facilitate loading and unloading operations. The C-5 features a malfunction detection analysis and recording system to identify errors throughout the aircraft. The cargo compartment is 121 ft (37 m) long, 13.5 ft (4.1 m) high, and 19 ft (5.8 m) wide, or just over 31,000 cu ft (880 m ). It can accommodate up to 36 463L master pallets or

2166-569: 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

2280-552: A system or component as may be practicable thereby: Total Package Procurement did not succeed. The unique complexity of shipbuilding made Total Package Procurement particularly inappropriate for these programs. Notable programs that encountered major problems with the TPP approach were the Air Force's Lockheed C-5 Galaxy and AGM-69 SRAM , the Army's Lockheed AH-56 Cheyenne , the Tarawa-class amphibious assault ships (LHA), and

2394-499: A takeoff weight of 649,680 lb (294,690 kg) including payload, fuel, and other equipment. On 18 July 2017, C-5s based at Dover were ordered to stand down so maintenance crews could determine the cause for some nose landing gear failing. The last TF39-powered C-5 flew in late 2017. The C-5A is the original version of the C-5. From 1969 to 1973, 81 C-5As were delivered to the Military Airlift Command of

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2508-473: 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

2622-421: 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

2736-496: 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

2850-704: 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

2964-470: Is a large, high-wing cargo aircraft with a distinctive high T-tail fin (vertical) stabilizer, with four TF39 turbofan engines mounted on pylons beneath wings that are swept 25°. (The C-5M uses newer GE CF6 engines.) Similar in layout to its smaller predecessor, the C-141 Starlifter, the C-5 has 12 internal wing tanks and is equipped for aerial refueling . Above the plane-length cargo deck

3078-434: Is a type of airbreathing jet engine that is widely used in aircraft propulsion . The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all

3192-583: Is an upper deck for flight operations and for seating 80 passengers in rear facing seats (unlike most commercial airplanes) and the embarked loadmaster crew in forward facing seats. Bay doors at both nose and tail open to enable "drive-through" loading and unloading of cargo. The cargo hold of the C-5 is one foot (30 cm) longer than the entire length of the first powered flight by the Wright brothers at Kitty Hawk, North Carolina . For its voracious consumption of fuel and its maintenance and reliability issues

3306-507: 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,

3420-410: 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

3534-430: 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,

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3648-413: 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

3762-420: 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

3876-411: 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

3990-634: The American Ethical Union honored Durham with the Elliott-Black Award. The Deputy Assistant Secretary of the Air Force for Management Systems, Ernest Fitzgerald, was another person whose fostering of public accountability was unwelcome. Upon completion of testing in December 1969, the first C-5A was transferred to the Transitional Training Unit at Altus Air Force Base , Oklahoma. Lockheed delivered

4104-479: 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

4218-676: The Douglas C-133 Cargomaster and complement Lockheed C-141 Starlifters . In addition to higher overall performance, the United States Army wanted a transport aircraft with a larger cargo bay than the C-141, whose interior was too small to carry a variety of their outsized equipment . This need led to the CX-4 requirement of July 1962, for which Lockheed, Boeing, Convair, and Douglas proposed six-engined designs. When

4332-702: 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

4446-539: The National Aeronautic Association for formal recognition. The C-5M had carried a payload of 176,610 lb (80,110 kg) to over 41,100 ft (12,500 m) in 23 minutes, 59 seconds. Additionally, 33 time to climb records at various payload classes were set, and the world record for greatest payload to 6,562 ft (2,000 m) was broken. The aircraft was in the category of 551,200 to 661,400 lb (250,000 to 300,000 kg) with

4560-586: The Spruance-class destroyers . Upon taking office as Deputy Secretary of Defense in 1970, David Packard issued a May 28, 1970 memorandum that contained a number of major reforms designed to address "the real mess we have on our hands." A key reform was elimination of TPP except in rare situations. Lockheed C-5 Galaxy The Lockheed C-5 Galaxy is a large military transport aircraft designed and built by Lockheed , and now maintained and upgraded by its successor, Lockheed Martin . It provides

4674-484: The United States Air Force (USAF) with a heavy intercontinental-range strategic airlift capability, one that can carry outsized and oversized loads, including all air-certifiable cargo. The Galaxy has many similarities to the smaller Lockheed C-141 Starlifter and the later Boeing C-17 Globemaster III . The C-5 is among the largest military aircraft in the world. The C-5 Galaxy's development

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4788-520: 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 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

4902-506: The "Heavy Logistics System" (CX-HLS) (previously CX-HLC). In May 1964, proposals for aircraft were received from Boeing , Douglas , General Dynamics , Lockheed , and Martin Marietta . General Electric , Curtiss-Wright , and Pratt & Whitney submitted proposals for the engines. After a downselect, Boeing, Douglas, and Lockheed were given one-year study contracts for the airframe, along with General Electric and Pratt & Whitney for

5016-421: 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

5130-517: The 1990s Non-Developmental Airlift Aircraft (NDAA) program as an alternative to further purchases of the McDonnell Douglas C-17 Globemaster III as well as a replacement for older C-5As. The C-5D was to have General Electric F138-GE-100 (CF6-80C2) engines, improved avionics and significantly improved reliability and maintainability, although it could not use austere runways or conduct airdrop operations and had

5244-487: The 76 completed C-5As to restore full payload capability and service life began in 1976. After design and testing of the new wing design, the C-5As received their new wings from 1980 to 1987. In 1974, Imperial Iran , having good relations with the United States, offered $ 160 million (equivalent to $ 989 million today) to restart C-5 production to enable Iran to purchase aircraft for their own air force, in

5358-572: The Air Force Reserve Command's 433d Airlift Wing at Lackland AFB / Kelly Field, Texas, and 439th Airlift Wing at Westover ARB, Massachusetts. The last operational C-5A was retired on 7 September 2017. The C-5B is an improved version of the C-5A. It incorporated all modifications and improvements made to the C-5A with improved wings, simplified landing gear, upgraded TF-39-GE-1C turbofan engines and updated avionics. Fifty examples of

5472-607: The Avionics Modernization Program (AMP) began upgrading the C-5's avionics to include a glass cockpit , navigation equipment, and a new autopilot system. Another part of the C-5 modernization effort is the Reliability Enhancement and Re-engining Program (RERP). The program replaced the engines with newer, more powerful ones. A total of 52 C-5s were contracted to be modernized, consisting of 49 B-, two C- and one A-model aircraft through

5586-687: The British-led peacekeeper initiative in Zimbabwe in 1979. On 24 October 1974, the Space and Missile Systems Organization successfully conducted an air-launched ballistic missile test, where a C-5A Galaxy aircraft air dropped an 86,000-pound (39,000 kg) Minuteman ICBM from 20,000 feet (6,100 m) over the Pacific Ocean. The missile descended to 8,000 feet (2,400 m) before its rocket engine fired. The 10-second engine burn carried

5700-562: The C-5 and wanted to build the biggest thing we could … Quite frankly, the C-5 program was a great contribution to commercial aviation. We'll never get credit for it, but we incentivized that industry by developing [the TF39] engine. General Duane H. Cassidy , former MAC Commander in Chief The criteria were finalized and an official request for proposal was issued in April 1964 for

5814-647: The C-5 since 1969. In that time, the airlifter supported US military operations in all major conflicts including Vietnam , Iraq , Yugoslavia , and Afghanistan , as well as allied support, such as Israel during the Yom Kippur War and operations in the Gulf War . The Galaxy has also distributed humanitarian aid, provided disaster relief, and supported the US space program. In 1961, several aircraft companies began studying heavy jet transport designs that would replace

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5928-607: The C-5, and later the L-1011 , which led to the governmental rescue of the company. Lockheed proposed a twin body C-5 as a Shuttle Carrier Aircraft to counter the Conroy Virtus , but the design was turned down in favor of the Boeing 747 . United States Air Force – 52 C-5Ms in service as of August 2018 Air Mobility Command Air Force Reserve Command Military Airlift Command / Air Mobility Command Air Force Reserve Turbofan A turbofan or fanjet

6042-496: The Galaxy's aircrews have nicknamed it "FRED", for Fucking Ridiculous Economic/Environmental Disaster. Takeoff and landing distance requirements for the plane at maximum-load gross weight are 8,300 ft (2,500 m) and 4,900 ft (1,500 m), respectively. Its high-flotation main landing gear provides 28 wheels to distribute gross weight on paved or earth surfaces. The rear main landing gear can be made to caster to make

6156-831: The RERP. The program featured over 70 changes and upgrades, including the newer General Electric engines. Three C-5s underwent RERP for testing purposes. Low-rate initial production started in August 2009 with Lockheed reaching full production in May 2011; 22 C-5M Super Galaxies have been completed as of August 2014. RERP upgrades were completed on 25 July 2018. The Air Force received the last modified aircraft on 1 August 2018. In 2014 Lockheed investigated drag reduction by plasma-heating of turbulent transonic airflow in critical points, saving overall weight by reducing fuel consumption. The Air Force Research Laboratory looked into shape-memory alloy for speed-dependent vortex generators . The C-5

6270-435: The U.S. Air Force. Due to cracks found in the wings in the mid-1970s, the cargo weight was restricted. To restore the C-5's full capability, the wing structure was redesigned. A program to install new strengthened wings on 77 C-5As was conducted from 1981 to 1987. The redesigned wing made use of a new aluminum alloy that did not exist during the original production. As of August 2016, there were ten A-models in service flown by

6384-772: The US Army judged the CX-4 specification inadequate for its requirements, by late 1963 the CX-4 specification gave way to the CX-HLC requirement specified an airlifter with four engines, an equipped gross weight of 550,000 pounds (249,000 kg), a maximum payload of 180,000 lb (81,600 kg), and a speed of Mach 0.75 (500 mph or 805 km/h). The cargo compartment was 17.2 ft (5.24 m) wide by 13.5 feet (4.11 m) high and 100 ft (30.5 m) long with front and rear access doors. USAF studies showed that high-bypass turbofan engines were needed for thrust and fuel efficiency requirements. We started to build

6498-493: The USAF decided to convert remaining C-5Bs and C-5Cs into C-5Ms with avionics upgrades and re-engining. The C-5As will receive only the avionics upgrades. The last of 52 C-5Ms was delivered to Air Mobility Command in August 2018. In response to Air Force plans to retire older C-5 aircraft, Congress implemented legislation that set limits on retirement plans for C-5As in 2003. As of November 2013, 45 C-5As have been retired, 11 have been scrapped, parts of one (A/C 66-8306) are now

6612-403: The United States to any location on the globe; and of accommodating up to six Boeing AH-64 Apache helicopters or five Bradley Fighting Vehicles at one time. The first C-5A was delivered to the USAF on 17 December 1969. Wings were built up in the early 1970s at Altus AFB , Oklahoma; Charleston AFB , South Carolina; Dover AFB , Delaware; and Travis AFB , California. The C-5's first mission

6726-464: 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

6840-422: 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

6954-409: 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 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

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7068-404: The air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust . The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as

7182-466: The all-cargo version was predicted to be able to carry typical C-5 volume for as little as 2 cents per ton-mile (in 1967 dollars). Although some interest was expressed by carriers, no orders were placed for either L-500 version, due to operational costs caused by low fuel efficiency, a significant concern for a profit-making carrier, even before the oil crisis of the 1970s, keen competition from Boeing's 747, and high costs incurred by Lockheed in developing

7296-474: 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

7410-653: The avionics to comply with Global Air Traffic Management standards, improving communications, fitting new flat-panel displays, improving navigation and safety equipment, and installing a new autopilot system. The first flight of a C-5 with AMP (85-0004) occurred on 21 December 2002. The Reliability Enhancement and Re-engining Program (RERP) began in 2006. It includes fitting new General Electric F138-GE-100 (CF6-80C2) engines, pylons and auxiliary power units, and upgrades to aircraft skin and frame, landing gear, cockpit and pressurization systems. Each CF6 engine produces 22% more thrust (50,000 lbf or 220 kN), providing

7524-575: The dubious distinction of being the first development program with a $ 1‑billion (equivalent to $ 8.3 billion today) overrun. Due to the C-5's troubled development, the Department of Defense abandoned Total Package Procurement . In 1969, Henry Durham raised concerns about the C-5 production process with Lockheed, his employer. Subsequently, Durham was transferred and subjected to abuse until he resigned. The Government Accountability Office substantiated some of his charges against Lockheed. Later,

7638-448: 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

7752-427: 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

7866-590: The engines. All three of the designs shared a number of features. The cockpit was placed well above the cargo area to allow for cargo loading through a nose door. The Boeing and Douglas designs used a pod on the top of the fuselage containing the cockpit, while the Lockheed design extended the cockpit profile down the length of the fuselage, giving it an egg-shaped cross section. All of the designs had swept wings , as well as front and rear cargo doors, allowing simultaneous loading and unloading. Lockheed's design featured

7980-524: 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

8094-494: The fan nozzle. The amount of energy transferred depends on how much pressure rise 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

8208-480: The first C-5B on 28 December 1985 and the final one in April 1989. The reliability of the C-5 fleet has been a continued issue throughout its lifetime, however the C-5M upgrade program seeks in part to address this issue. Their strategic airlift capacity has been a key logistical component of U.S. military operations in Afghanistan and Iraq . Following an incident during Operation Iraqi Freedom where one C-5

8322-450: 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

8436-483: The first operational Galaxy to the 437th Airlift Wing , Charleston Air Force Base , South Carolina, in June 1970. Due to higher than expected development costs, in 1970, public calls were made for the government to split the substantial losses that Lockheed was experiencing. Production was nearly brought to a halt in 1971 as Lockheed went through financial difficulties, due in part to the C-5 Galaxy's development, as well as

8550-402: The flaps deflected 40° was higher than predicted (2.60 vs. 2.38), but was lower than predicted with the flaps deflected 25° (2.31 vs. 2.38) and with the flaps retracted (1.45 vs. 1.52). After being one of the worst-run programs, ever, in its early years, it has evolved very slowly and with great difficulty into a nearly adequate strategic airlifter that unfortunately needs in-flight refueling or

8664-496: 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 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

8778-429: 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

8892-413: The guaranteed weight, but by the time of the delivery of the 9th aircraft, had exceeded guarantees. In July 1969, during a fuselage upbending test, the wing failed at 128% of limit load, which is below the requirement that it sustain 150% of limit load. Changes were made to the wing, but during a test in July 1970, it failed at 125% of limit load. A passive load-reduction system, involving uprigged ailerons,

9006-635: The high-winged An-225 , which derived from the An-124 , which is similar in design and function to the C-5. During static and fatigue testing , cracks were noticed in the wings of several aircraft, and as a consequence, the C-5A fleet was restricted to 80% of maximum design loads. To reduce wing loading, load alleviation systems were added to the aircraft. By 1980, payloads were restricted to as low as 50,000 lb (23,000 kg) for general cargo during peacetime operations. A $ 1.5 billion program (equivalent to $ 8 billion today), known as H-Mod, to re-wing

9120-474: 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

9234-417: 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

9348-487: The missile to 20,000 feet (6,100 m) again before it dropped into the ocean. The test proved the feasibility of launching an intercontinental ballistic missile from the air. Operational deployment was discarded due to engineering and security difficulties, though the capability was used as a negotiating point in the Strategic Arms Limitation Talks . Aircraft 69–0014, "Zero-One-Four" used in

9462-401: The new variant were delivered to the U.S. Air Force from 1986 to 1989. The C-5C is a specially modified variant for transporting large cargo. Two C-5As (68-0213 and 68-0216) were modified following major accidents to have a larger internal cargo capacity to accommodate large payloads, such as satellites. The major modifications were the removal of the rear passenger compartment floor, splitting

9576-539: 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

9690-416: The outset of the acquisition phase under a single contract containing price, performance and schedule commitments, the maximum practical amount of design, development, production and support needed to introduce and sustain a system or component in the inventory. The purpose of TPP was to procure under the influence of competition as much of the total design, development, production and support requirements for

9804-567: The rear cargo door in the middle, and installing a new movable aft bulkhead further to the rear. The official C-5 technical manual refers to the version as C-5A(SCM) Space Cargo Modified . Modifications also included adding a second inlet for ground power, which can feed any power-dependent equipment that may form part of the cargo. The two C-5Cs are operated by U.S. Air Force crews for DOD spacecraft programs and NASA , and are stationed at Travis AFB, California. Both C-5Cs #68-0213 and #68-0216 have been modified into C-5Ms as of 2017. Proposed during

9918-467: The required thrust still maintained by increasing the mass accelerated. A turbofan does this by transferring energy available inside 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

10032-399: 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

10146-502: 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

10260-454: 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 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

10374-536: 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

10488-702: The test was retired to the Air Mobility Command Museum at Dover Air Force Base . The C-5 has been used for several unusual functions. During the development of the secretive stealth fighter, the Lockheed F-117 Nighthawk , Galaxies were often used to carry partly disassembled aircraft, leaving no exterior signs as to their cargo. The C-5 remains the largest aircraft to operate in the Antarctic, capable of operating from Williams Field near McMurdo Station . The C-5 Galaxy

10602-497: 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

10716-551: The time, GE's engine concept was revolutionary, as all engines before had a bypass ratio less than two-to-one, while the TF39 promised and would achieve a ratio of eight-to-one, which had the benefits of increased engine thrust and lower fuel consumption. Boeing lost the military contract but went on to develop the successful 747 civilian airliner with over 1,500 aircraft built when manufacturing ended in 2022 after 54 years of production. The first C-5A Galaxy ( serial number 66-8303 )

10830-673: 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

10944-428: 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

11058-425: 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 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

11172-445: 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 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

11286-453: 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 the propulsion of aircraft", in which he describes the principles behind the turbofan, although not called as such at that time. While

11400-476: 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

11514-418: 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

11628-510: 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

11742-701: 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

11856-522: The years. During the Yom Kippur War in 1973, multiple C-5s and C-141 Starlifters delivered critical supplies of ammunition, replacement weaponry and other forms of aid to Israel, the US effort was named as Operation Nickel Grass . The C-5 Galaxy's performance in Israel was such that the Pentagon began to consider further purchases. The C-5 was regularly made available to support American allies, such as

11970-452: Was a major supply asset in the international coalition operations in 1990–91 against Iraq in the Gulf War . C-5s have routinely delivered relief aid and humanitarian supplies to areas afflicted with natural disasters or crisis; multiple flights were made over Rwanda in 1994. The C-5 is also used to transport Marine One . The wings on the C-5As were replaced during the 1980s to restore full design capability. The USAF took delivery of

12084-614: 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

12198-450: Was complicated, including significant cost overruns , and Lockheed suffered significant financial difficulties. Shortly after entering service, cracks in the wings of many aircraft were discovered and the C-5 fleet was restricted in capability until corrective work was completed. The C-5M Super Galaxy is an upgraded version with new engines and modernized avionics designed to extend its service life to 2040 and beyond. The USAF has operated

12312-441: Was damaged by a projectile, the installation of defensive systems has become a stated priority. The C-5 AMP and RERP modernization programs plan to raise mission-capable rate to a minimum goal of 75%. Over the next 40 years, the U.S. Air Force estimates the C-5M will save over $ 20 billion. The first C-5M conversion was completed on 16 May 2006 and C-5Ms began test flights at Dobbins Air Reserve Base in June 2006. In 2008,

12426-660: 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

12540-441: Was incorporated, but the maximum allowable payload was reduced from 220,000 to 190,000 lb (100,000 to 86,000 kg). At the time, a 90% probability was predicted that no more than 10% of the fleet of 79 airframes would reach their fatigue life of 19,000 hours without cracking of the wing. Cost overruns and technical problems of the C-5A were the subject of a congressional investigation in 1968 and 1969. The C-5 program has

12654-757: Was on 9 July 1970, in Southeast Asia during the Vietnam War . C-5s were used to transport equipment and troops, including Army tanks and even some small aircraft, throughout the later years of the US action in Vietnam. In the final weeks of the war, prior to the Fall of Saigon , several C-5s were involved in evacuation efforts. During one such mission , a C-5A crashed while transporting a large number of orphans, with over 140 killed. C-5s have also been used to deliver support and reinforce various US allies over

12768-402: Was overturned. The Air Force seeks to retire one C-5A for every 10 new C-17s ordered. In October 2011, the 445th Airlift Wing based at Wright-Patterson Air Force Base replaced all remaining C-5s with C-17s. The C-5M reached initial operating capability (IOC) on 24 February 2014 with 16 aircraft delivered. On 13 September 2009, a C-5M set 41 new records and flight data was submitted to

12882-465: Was rolled out of the manufacturing plant in Marietta, Georgia , on 2 March 1968. On 30 June 1968, flight testing of the C-5A began with the first flight, flown by Leo Sullivan, with the call sign "eight-three-oh-three heavy ". Flight tests revealed that the aircraft exhibited a higher drag divergence Mach number than predicted by wind tunnel data. The maximum lift coefficient measured in flight with

12996-587: 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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