A military transport aircraft , military cargo aircraft or airlifter is a military-owned transport aircraft used to support military operations by airlifting troops and military equipment. Transport aircraft are crucial to maintaining supply lines to forward bases that are difficult to reach by ground or waterborne access, and can be used for both strategic and tactical missions. They are also often used for civilian emergency relief missions by transporting humanitarian aid .
127-485: 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 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
254-570: 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
381-500: A platoon of infantry, or transporting towed artillery or light vehicles either internally or as underslung roles. Unlike the assault helicopter they are usually not expected to land directly in a contested landing zone, but are used to reinforce and resupply landing zones taken by the initial assault wave. Examples include the unarmed versions of the Mil Mi-8, Super Puma , CH-46 Sea Knight , and NH90 . Heavy lift helicopters are
508-648: 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
635-566: 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
762-751: 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
889-399: 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
1016-710: 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 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),
1143-401: 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 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
1270-515: A local indentation of the fuselage above and below the wing root. This proved to not be very effective. During the development of the Douglas DC-8 airliner, uncambered airfoils were used in the wing root area to combat the unsweeping. Swept wings on supersonic aircraft usually lie within the cone-shaped shock wave produced at the nose of the aircraft so they will "see" subsonic airflow and work as subsonic wings. The angle needed to lie behind
1397-413: 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
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#17327795960861524-462: A means of creating positive longitudinal static stability . For a low-speed aircraft, swept wings may be used to resolve problems with the center of gravity , to move the wing spar into a more convenient location, or to improve the sideways view from the pilot's position. By 1905, Dunne had already built a model glider with swept wings followed by the powered Dunne D.5 , and by 1913 he had constructed successful powered variants that were able to cross
1651-511: 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
1778-461: 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
1905-615: 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,
2032-484: A pair of proposed fighter aircraft equipped with swept wings from Hawker Aircraft and Supermarine , the Hawker Hunter and Supermarine Swift respectively, and successfully pressed for orders to be placed 'off the drawing board' in 1950. On 7 September 1953, the sole Hunter Mk 3 (the modified first prototype, WB 188 ) flown by Neville Duke broke the world air speed record for jet-powered aircraft, attaining
2159-573: 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 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
2286-592: A record-breaking speed of Mach 1.06 (700 miles per hour (1,100 km/h; 610 kn)). The news of a successful straight-wing supersonic aircraft surprised many aeronautical experts on both sides of the Atlantic, as it was increasingly believed that a swept-wing design not only highly beneficial but also necessary to break the sound barrier. During the final years of the Second World War, aircraft designer Sir Geoffrey de Havilland commenced development on
2413-453: A reflex curve at the trailing edge. This results in a much weaker shock wave towards the rear of the upper wing surface and a corresponding increase in critical mach number. Shock waves require energy to form. This energy is taken out of the aircraft, which has to supply extra thrust to make up for this energy loss. Thus the shocks are seen as a form of drag . Since the shocks form when the local air velocity reaches supersonic speeds, there
2540-441: 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 the 1990s Non-Developmental Airlift Aircraft (NDAA) program as an alternative to further purchases of
2667-770: 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
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#17327795960862794-589: 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
2921-420: A swept wing as it travels through the air. The airflow over a swept wing encounters the wing at an angle. That angle can be broken down into two vectors, one perpendicular to the wing, and one parallel to the wing. The flow parallel to the wing has no effect on it, and since the perpendicular vector is shorter (meaning slower) than the actual airflow, it consequently exerts less pressure on the wing. In other words,
3048-540: A swept wing the wing panels on the Douglas DC-1 outboard of the nacelles also had slight sweepback for similar reasons. 2. to provide longitudinal stability for tailless aircraft, e.g. Messerschmitt Me 163 Kometuu . 3. most commonly to increase Mach-number capability by delaying to a higher speed the effects of compressibility (abrupt changes in the density of the airflow), e.g. combat aircraft, airliners and business jets. Other reasons include: 1. enabling
3175-412: A wing carry-through box position to achieve a desired cabin size, e.g. HFB 320 Hansa Jet . 2. providing static aeroelastic relief which reduces bending moments under high g-loadings and may allow a lighter wing structure. For a wing of given span, sweeping it increases the length of the spars running along it from root to tip. This tends to increase weight and reduce stiffness. If the fore-aft chord of
3302-434: A wing is generated by the airflow over it from front to rear. With increasing span-wise flow the boundary layers on the surface of the wing have longer to travel, and so are thicker and more susceptible to transition to turbulence or flow separation, also the effective aspect ratio of the wing is less and so air "leaks" around the wing tips reducing their effectiveness. The spanwise flow on swept wings produces airflow that moves
3429-547: A world speed record. On 12 April 1948, a D.H.108 did set a world's speed record at 973.65 km/h (605 mph), it subsequently became the first jet aircraft to exceed the speed of sound. Around this same timeframe, the Air Ministry introduced a program of experimental aircraft to examine the effects of swept wings, as well as the delta wing configuration. Furthermore, the Royal Air Force (RAF) identified
3556-410: Is a certain " critical mach " speed where sonic flow first appears on the wing. There is a following point called the drag divergence mach number where the effect of the drag from the shocks becomes noticeable. This is normally when the shocks start generating over the wing, which on most aircraft is the largest continually curved surface, and therefore the largest contributor to this effect. Sweeping
3683-470: 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
3810-503: 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 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
3937-581: 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
Lockheed C-5 Galaxy - Misplaced Pages Continue
4064-507: Is normally used to mean "swept back", but variants include forward sweep , variable sweep wings and oblique wings in which one side sweeps forward and the other back. The delta wing is also aerodynamically a form of swept wing. There are three main reasons for sweeping a wing: 1. to arrange the center of gravity of the aircraft and the aerodynamic center of the wing to coincide more closely for longitudinal balance, e.g. Messerschmitt Me 163 Komet and Messerschmitt Me 262 . Although not
4191-429: Is placed in an airstream at an angle of yaw – i.e., it is swept back. Now, even if the local speed of the air on the upper surface of the wing becomes supersonic, a shock wave cannot form there because it would have to be a sweptback shock – swept at the same angle as the wing – i.e., it would be an oblique shock. Such an oblique shock cannot form until the velocity component normal to it becomes supersonic." To visualize
4318-447: Is rare and the wing must be unusually rigid. There are two sweep angles of importance, one at the leading edge for supersonic aircraft and the other 25% of the way back from the leading edge for subsonic and transonic aircraft. Leading edge sweep is important because the leading edge has to be behind the mach cone to reduce wave drag. The quarter chord (25%) line is used because subsonic lift due to angle of attack acts there and, up until
4445-487: The Sabre dance in reference to the number of North American F-100 Super Sabres that crashed on landing as a result. Reducing pitch-up to an acceptable level has been done in different ways such as the addition of a fin known as a wing fence on the upper surface of the wing to redirect the flow to a streamwise direction. The MiG-15 was one example of an aircraft fitted with wing fences. Another closely related design
4572-632: 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
4699-711: The English Channel . The Dunne D.5 was exceptionally aerodynamically stable for the time, and the D.8 was sold to the Royal Flying Corps ; it was also manufactured under licence by Starling Burgess to the United States Navy amongst other customers. Dunne's work ceased with the onset of war in 1914, but afterwards the idea was taken up by G. T. R. Hill in England who designed a series of gliders and aircraft to Dunne's guidelines, notably
4826-654: 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 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
4953-461: The Junkers Ju 287 or HFB 320 Hansa Jet . However, larger sweep suitable for high-speed aircraft, like fighters, was generally impossible until the introduction of fly by wire systems that could react quickly enough to damp out these instabilities. The Grumman X-29 was an experimental technology demonstration project designed to test the forward swept wing for enhanced maneuverability during
5080-533: 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 a higher expected operating cost. The plan was canceled in favor of the purchase of more C-17s. The specifications of
5207-590: The Westland-Hill Pterodactyl series. However, Dunne's theories met with little acceptance amongst the leading aircraft designers and aviation companies at the time. The idea of using swept wings to reduce high-speed drag was developed in Germany in the 1930s. At a Volta Conference meeting in 1935 in Italy, Adolf Busemann suggested the use of swept wings for supersonic flight. He noted that
Lockheed C-5 Galaxy - Misplaced Pages Continue
5334-418: The de Havilland Comet , which would become the world's first jet airliner. An early design consideration was whether to apply the new swept-wing configuration. Thus, an experimental aircraft to explore the technology, the de Havilland DH 108 , was developed by the firm in 1944, headed by project engineer John Carver Meadows Frost with a team of 8–10 draughtsmen and engineers. The DH 108 primarily consisted of
5461-671: The landing zone . This armament may be in the form of door gunners , or the modification of the helicopter with stub wings and pylons to carry missiles and rocket pods . For example, the Sikorsky S-70 , fitted with the ESSM (External Stores Support System), and the Hip E variant of the Mil Mi-8 can carry as much disposable armament as some dedicated attack helicopters . Medium transport helicopters are generally capable of moving up to
5588-506: 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
5715-412: The 1930s and 1940s, but the breakthrough mathematical definition of sweep theory is generally credited to NACA 's Robert T. Jones in 1945. Sweep theory builds on other wing lift theories. Lifting line theory describes lift generated by a straight wing (a wing in which the leading edge is perpendicular to the airflow). Weissinger theory describes the distribution of lift for a swept wing, but does not have
5842-405: The 1980s. The Sukhoi Su-47 Berkut is another notable demonstrator aircraft implementing this technology to achieve high levels of agility. To date, no highly swept-forward design has entered production. The first successful aeroplanes adhered to the basic design of rectangular wings at right angles to the body of the machine. Such a layout is inherently unstable; if the weight distribution of
5969-532: 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
6096-605: 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
6223-686: 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
6350-561: 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
6477-732: 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 Military transport aircraft Military transport aeroplanes are defined in terms of their range capability as strategic airlift or tactical airlift to reflect
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#17327795960866604-635: 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 the avionics to comply with Global Air Traffic Management standards, improving communications, fitting new flat-panel displays, improving navigation and safety equipment, and installing
6731-494: 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
6858-825: 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
6985-488: 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
7112-401: 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
7239-707: The actual aircraft speed is, this becomes a problem during slow-flight phases, such as takeoff and landing. There have been various ways of addressing the problem, including the variable-incidence wing design on the Vought F-8 Crusader , and swing wings on aircraft such as the F-14 , F-111 , and the Panavia Tornado . The term "swept wing" is normally used to mean "swept back", but other swept variants include forward sweep , variable sweep wings and oblique wings in which one side sweeps forward and
7366-434: The air does have time to react, and is pushed spanwise by the angled leading edge, towards the wing tip. At the wing root, by the fuselage, this has little noticeable effect, but as one moves towards the wingtip the airflow is pushed spanwise not only by the leading edge, but the spanwise moving air beside it. At the tip the airflow is moving along the wing instead of over it, a problem known as spanwise flow . The lift from
7493-421: The air would be added to the previously perpendicular airflow, resulting in an airflow over the wing at an angle to the leading edge. This angle results in airflow traveling a greater distance from leading edge to trailing edge, and thus the air pressure is distributed over a greater distance (and consequently lessened at any particular point on the surface). This scenario is identical to the airflow experienced by
7620-414: The aircraft changes even slightly, the wing will want to rotate so its front moves up (weight moving rearward) or down (forward) and this rotation will change the development of lift and cause it to move further in that direction. To make an aircraft stable, the normal solution is to place the weight at one end and offset this with an opposite downward force at the other - this leads to the classic layout with
7747-422: The aircraft to reach speeds closer to Mach 1. One limiting factor in swept wing design is the so-called "middle effect". If a swept wing is continuous - an oblique swept wing - the pressure isobars will be swept at a continuous angle from tip to tip. However, if the left and right halves are swept back equally, as is common practice, the pressure isobars on the left wing in theory will meet the pressure isobars of
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#17327795960867874-418: The airspeed over the wing was dominated by the normal component of the airflow, not the freestream velocity, so by setting the wing at an angle the forward velocity at which the shock waves would form would be higher (the same had been noted by Max Munk in 1924, although not in the context of high-speed flight). Albert Betz immediately suggested the same effect would be equally useful in the transonic. After
8001-465: 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
8128-413: The angle of attack at the tip, thus reducing the bending moment on the wing, as well as somewhat reducing the chance of tip stall. However, the same effect on forward-swept wings produces a wash-in effect that increases the angle of attack promoting tip stall. Small amounts of sweep do not cause serious problems, and had been used on a variety of aircraft to move the spar into a convenient location, as on
8255-401: The basic concept of simple sweep theory, consider a straight, non-swept wing of infinite length, which meets the airflow at a perpendicular angle. The resulting air pressure distribution is equivalent to the length of the wing's chord (the distance from the leading edge to the trailing edge). If we were to begin to slide the wing sideways ( spanwise ), the sideways motion of the wing relative to
8382-400: The battle front. Military transport helicopters are used in places where the use of conventional aircraft is impossible. For example, the military transport helicopter is the primary transport asset of US Marines deploying from LHDs and LHA . The landing possibilities of helicopters are almost unlimited, and where landing is impossible, for example densely packed jungle, the ability of
8509-412: The capability to include chordwise pressure distribution. There are other methods that do describe chordwise distributions, but they have other limitations. Jones' sweep theory provides a simple, comprehensive analysis of swept wing performance. An explanation of how the swept wing works was offered by Robert T. Jones : "Assume a wing is a cylinder of uniform airfoil cross-section, chord and thickness and
8636-525: 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 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
8763-519: The cone increases with increasing speed, at Mach 1.3 the angle is about 45 degrees, at Mach 2.0 it is 60 degrees. The angle of the Mach cone formed off the body of the aircraft will be at about sin μ = 1/M (μ is the sweep angle of the Mach cone) When a swept wing travels at high speed, the airflow has little time to react and simply flows over the wing almost straight from front to back. At lower speeds
8890-572: 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,
9017-412: The effects of compressibility in transonic and supersonic aircraft because of the reduced pressures. This allows the mach number of an aircraft to be higher than that actually experienced by the wing. There is also a negative aspect to sweep theory. The lift produced by a wing is directly related to the speed of the air over the wing. Since the airflow speed experienced by a swept wing is lower than what
9144-460: The engine in front and the control surfaces at the end of a long boom with the wing in the middle. This layout has long been known to be inefficient. The downward force of the control surfaces needs further lift from the wing to offset. The amount of force can be decreased by increasing the length of the boom, but this leads to more skin friction and weight of the boom itself. This problem led to many experiments with different layouts that eliminates
9271-588: 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
9398-554: The fastest aircraft of the era were only approaching 400 km/h (249 mph).The presentation was largely of academic interest, and soon forgotten. Even notable attendees including Theodore von Kármán and Eastman Jacobs did not recall the presentation 10 years later when it was re-introduced to them. Hubert Ludwieg of the High-Speed Aerodynamics Branch at the AVA Göttingen in 1939 conducted
9525-476: 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
9652-482: 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
9779-565: The first wind tunnel tests to investigate Busemann's theory. Two wings, one with no sweep, and one with 45 degrees of sweep were tested at Mach numbers of 0.7 and 0.9 in the 11 x 13 cm wind tunnel. The results of these tests confirmed the drag reduction offered by swept wings at transonic speeds. The results of the tests were communicated to Albert Betz who then passed them on to Willy Messerschmitt in December 1939. The tests were expanded in 1940 to include wings with 15, 30 and -45 degrees of sweep and Mach numbers as high as 1.21. With
9906-401: 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
10033-442: The freestream conditions around the rest of the aircraft, and as the flow enters an adverse pressure gradient in the aft section of the wing, a discontinuity emerges in the form of a shock wave as the air is forced to rapidly slow and return to ambient pressure. At the point where the density drops, the local speed of sound correspondingly drops and a shock wave can form. This is why in conventional wings, shock waves form first after
10160-412: 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,
10287-414: The helicopter to hover allows troops to deploy by abseiling and roping . Transport helicopters are operated in assault, medium and heavy classes. Air assault helicopters are usually the smallest of the transport types, and designed to move an infantry squad or section and their equipment. Helicopters in the assault role are generally armed for self-protection both in transit and for suppression of
10414-631: 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
10541-756: The immediate post-war era, several nations were conducting research into high speed aircraft. In the United Kingdom, work commenced during 1943 on the Miles M.52 , a high-speed experimental aircraft equipped with a straight wing that was developed in conjunction with Frank Whittle 's Power Jets company, the Royal Aircraft Establishment (RAE) in Farnborough , and the National Physical Laboratory . The M.52
10668-538: The introduction of jets in the later half of the Second World War , the swept wing became increasingly applicable to optimally satisfying aerodynamic needs. The German jet-powered Messerschmitt Me 262 and rocket-powered Messerschmitt Me 163 suffered from compressibility effects that made both aircraft very difficult to control at high speeds. In addition, the speeds put them into the wave drag regime, and anything that could reduce this drag would increase
10795-494: The introduction of supercritical sections, the crest was usually close to the quarter chord. Typical sweep angles vary from 0 for a straight-wing aircraft, to 45 degrees or more for fighters and other high-speed designs. Shock waves can form on some parts of an aircraft moving at less than the speed of sound. Low-pressure regions around an aircraft cause the flow to accelerate, and at transonic speeds this local acceleration can exceed Mach 1. Localized supersonic flow must return to
10922-472: The largest and most capable of the transport types, currently limited in service to the CH-53 Sea Stallion and related CH-53E Super Stallion , CH-47 Chinook , Mil Mi-26 , and Aérospatiale Super Frelon . Capable of lifting up to 80 troops and moving small Armoured fighting vehicles (usually as slung loads but also internally), these helicopters operate in the tactical transport role in much
11049-399: The maximum Thickness/Chord and why all airliners designed for cruising in the transonic range (above M0.8) have supercritical wings that are flatter on top, resulting in minimized angular change of flow to upper surface air. The angular change to the air that is normally part of lift generation is decreased and this lift reduction is compensated for by deeper curved lower surfaces accompanied by
11176-485: 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
11303-420: The need for the downward force. One such wing geometry appeared before World War I , which led to early swept wing designs. In this layout, the wing is swept so that portions lie far in front and in back of the center of gravity (CoG), with the control surfaces behind it. The result is a weight distribution similar to the classic layout, but the offsetting control force is no longer a separate surface but part of
11430-448: The needs of the land forces which they most often support. These roughly correspond to the commercial flight length distinctions: Eurocontrol defines short-haul routes as shorter than 1,500 km (810 nmi), long-haul routes as longer than 4,000 km (2,200 nmi) and medium-haul between. The military glider is an unpowered tactical air transport which has been used in some campaigns to transport troops and/or equipment to
11557-433: The other back. The delta wing also incorporates the same advantages as part of its layout. Sweeping a wing forward has approximately the same effect as rearward in terms of drag reduction, but has other advantages in terms of low-speed handling where tip stall problems simply go away. In this case the low-speed air flows towards the fuselage, which acts as a very large wing fence. Additionally, wings are generally larger at
11684-421: The pairing of the front fuselage of the de Havilland Vampire to a swept wing and small vertical tail; it was the first British swept wing jet, unofficially known as the "Swallow". It first flew on 15 May 1946, a mere eight months after the project's go-ahead. Company test pilot and son of the builder, Geoffrey de Havilland Jr ., flew the first of three aircraft and found it extremely fast – fast enough to try for
11811-458: The performance of their aircraft, notably the notoriously short flight times measured in minutes. This resulted in a crash program to introduce new swept wing designs, both for fighters as well as bombers . The Blohm & Voss P 215 was designed to take full advantage of the swept wing's aerodynamic properties; however, an order for three prototypes was received only weeks before the war ended and no examples were ever built. The Focke-Wulf Ta 183
11938-402: The presentation the host of the meeting, Arturo Crocco , jokingly sketched "Busemann's airplane of the future" on the back of a menu while they all dined. Crocco's sketch showed a classic 1950s fighter design, with swept wings and tail surfaces, although he also sketched a swept propeller powering it. At the time, however, there was no way to power an aircraft to these sorts of speeds, and even
12065-422: The problem. In addition to pitch-up there are other complications inherent in a swept-wing configuration. For any given length of wing, the actual span from tip-to-tip is shorter than the same wing that is not swept. There is a strong correlation between low-speed drag and aspect ratio , the span compared to chord, so a swept wing always has more drag at lower speeds. In addition, there is extra torque applied by
12192-403: The right wing on the centerline at a large angle. As the isobars cannot meet in such a fashion, they will tend to curve on each side as they near the centerline, so that the isobars cross the centerline at right angles to the centerline. This causes an "unsweeping" of the isobars in the wing root region. To combat this unsweeping, German aerodynamicist Dietrich Küchemann proposed and had tested
12319-431: The root anyway, which allows them to have better low-speed lift. However, this arrangement also has serious stability problems. The rearmost section of the wing will stall first causing a pitch-up moment pushing the aircraft further into stall similar to a swept back wing design. Thus swept-forward wings are unstable in a fashion similar to the low-speed problems of a conventional swept wing. However unlike swept back wings,
12446-417: The same way as small fixed wing turboprop air-lifters. The lower speed, range and increased fuel consumption of helicopters are offset by their not requiring a runway. Swept wing A swept wing is a wing angled either backward or occasionally forward from its root rather than perpendicular to the fuselage. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds
12573-448: 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 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
12700-402: The stagnation point on the leading edge of any individual wing segment further beneath the leading edge, increasing effective angle of attack of wing segments relative to its neighbouring forward segment. The result is that wing segments farther towards the rear operate at increasingly higher angles of attack promoting early stall of those segments. This promotes tip stall on back-swept wings, as
12827-554: The swept wing design used by most modern jet aircraft, as this design performs more effectively at transonic and supersonic speeds. In its advanced form, sweep theory led to the experimental oblique wing concept. Adolf Busemann introduced the concept of the swept wing and presented this in 1935 at the Fifth Volta Conference in Rome. Sweep theory in general was a subject of development and investigation throughout
12954-698: 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
13081-549: 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 )
13208-411: The tips are most rearward, while delaying tip stall for forward-swept wings, where the tips are forward. With both forward and back-swept wings, the rear of the wing will stall first creating a nose-up moment on the aircraft. If not corrected by the pilot the plane will pitch up, leading to more of the wing stalling and more pitch up in a divergent manner. This uncontrollable instability came to be known as
13335-450: The tips on a forward swept design will stall last, maintaining roll control. Forward-swept wings can also experience dangerous flexing effects compared to aft-swept wings that can negate the tip stall advantage if the wing is not sufficiently stiff. In aft-swept designs, when the airplane maneuvers at high load factor the wing loading and geometry twists the wing in such a way as to create washout (tip twists leading edge down). This reduces
13462-404: The tips to bend upwards in normal flight. Backwards sweep causes the tips to reduce their angle of attack as they bend, reducing their lift and limiting the effect. Forward sweep causes the tips to increase their angle of attack as they bend. This increases their lift causing further bending and hence yet more lift in a cycle which can cause a runaway structural failure. For this reason forward sweep
13589-472: The wing also remains the same, the distance between leading and trailing edges reduces, reducing its ability to resist twisting (torsion) forces. A swept wing of given span and chord must therefore be strengthened and will be heavier than the equivalent unswept wing. A swept wing typically angles backward from its root rather than forwards. Because wings are made as light as possible, they tend to flex under load. This aeroelasticity under aerodynamic load causes
13716-448: The wing experiences airflow that is slower - and at lower pressures - than the actual speed of the aircraft. One of the factors that must be taken into account when designing a high-speed wing is compressibility , which is the effect that acts upon a wing as it approaches and passes through the speed of sound . The significant negative effects of compressibility made it a prime issue with aeronautical engineers. Sweep theory helps mitigate
13843-402: The wing has the effect of reducing the curvature of the body as seen from the airflow, by the cosine of the angle of sweep. For instance, a wing with a 45 degree sweep will see a reduction in effective curvature to about 70% of its straight-wing value. This has the effect of increasing the critical Mach by 30%. When applied to large areas of the aircraft, like the wings and empennage , this allows
13970-469: The wing to the fuselage which has to be allowed for when establishing the transfer of wing-box loads to the fuselage. This results from the significant part of the wing lift which lies behind the attachment length where the wing meets the fuselage. Sweep theory is an aeronautical engineering description of the behavior of airflow over a wing when the wing's leading edge encounters the airflow at an oblique angle. The development of sweep theory resulted in
14097-524: The wing, which would have existed anyway. This eliminates the need for separate structure, making the aircraft have less drag and require less total lift for the same level of performance. These layouts inspired several flying wing gliders and some powered aircraft during the interwar years. The first to achieve stability was British designer J. W. Dunne who was obsessed with achieving inherent stability in flight. He successfully employed swept wings in his tailless aircraft (which, crucially, used washout ) as
14224-582: 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
14351-446: 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
14478-582: Was another swept wing fighter design, but was also not produced before the war's end. In the post-war era, Kurt Tank developed the Ta 183 into the IAe Pulqui II , but this proved unsuccessful. A prototype test aircraft, the Messerschmitt Me P.1101 , was built to research the tradeoffs of the design and develop general rules about what angle of sweep to use. When it was 80% complete, the P.1101
14605-555: Was captured by US forces and returned to the United States , where two additional copies with US-built engines carried on the research as the Bell X-5 . Germany's wartime experience with the swept wings and its high value for supersonic flight stood in strong contrast to the prevailing views of Allied experts of the era, who commonly espoused their belief in the impossibility of manned vehicles travelling at such speeds. During
14732-436: 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 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
14859-493: 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 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
14986-437: 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,
15113-515: Was envisioned to be capable of achieving 1,000 miles per hour (1,600 km/h) in level flight, thus enabling the aircraft to potentially be the first to exceed the speed of sound in the world. In February 1946, the programme was abruptly discontinued for unclear reasons. It has since been widely recognised that the cancellation of the M.52 was a major setback in British progress in the field of supersonic design. Another, more successful, programme
15240-448: Was first investigated in Germany as early as 1935 by Albert Betz and Adolph Busemann , finding application just before the end of the Second World War . It has the effect of delaying the shock waves and accompanying aerodynamic drag rise caused by fluid compressibility near the speed of sound , improving performance. Swept wings are therefore almost always used on jet aircraft designed to fly at these speeds. The term "swept wing"
15367-438: 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
15494-753: 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
15621-567: 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 the National Aeronautic Association for formal recognition. The C-5M had carried
15748-464: 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
15875-606: Was the US's Bell X-1 , which also was equipped with a straight wing. According to Miles Chief Aerodynamicist Dennis Bancroft, the Bell Aircraft company was given access to the drawings and research on the M.52. On 14 October 1947, the Bell X-1 performed the first manned supersonic flight, piloted by Captain Charles "Chuck" Yeager , having been drop launched from the bomb bay of a Boeing B-29 Superfortress and attained
16002-541: Was the addition of a dogtooth notch to the leading edge, used on the Avro Arrow interceptor. Other designs took a more radical approach, including the Republic XF-91 Thunderceptor 's wing that grew wider towards the tip to provide more lift at the tip. The Handley Page Victor was equipped with a crescent wing , with three values of sweep, about 48 degrees near the wing root where the wing
16129-471: Was thickest, a 38 degree transition length and 27 degrees for the remainder to the tip. Modern solutions to the problem no longer require "custom" designs such as these. The addition of leading-edge slats and large compound flaps to the wings has largely resolved the issue. On fighter designs, the addition of leading-edge extensions , which are typically included to achieve a high level of maneuverability, also serve to add lift during landing and reduce
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