120-501: The Lockheed L-2000 was Lockheed Corporation 's entry in a government-funded competition to build the United States' first supersonic airliner in the 1960s. The L-2000 lost the contract to the Boeing 2707 , but that competing design was ultimately canceled for political, environmental and economic reasons. In 1961, President John F. Kennedy committed the government to subsidize 75% of
240-479: A Boeing 707 . Additionally, a delta wing is a naturally rigid structure which requires little stiffening. The plane's undercarriage was a traditional tricycle type with a twin-wheeled nose gear. Each of the two six-wheeled main gear utilized the same tires used on the Douglas DC-8 , but which were filled with nitrogen and to lower pressures. To provide an optimum entry date into service, Lockheed decided to use
360-685: A Mikoyan-Gurevich MiG-15 in Korea, although by this time the F-80 (as it was redesignated in June 1948) was already considered obsolete. Starting with the P-80, Lockheed's secret development work was conducted by its Advanced Development Division, more commonly known as the Skunk works . The name was taken from Al Capp 's comic strip Li'l Abner . This organization has become famous and spawned many successful Lockheed designs, including
480-407: A foil as angle of attack exceeds its critical value . The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid , foil – including its shape, size, and finish – and Reynolds number . Stalls in fixed-wing aircraft are often experienced as a sudden reduction in lift. It may be caused either by the pilot increasing the wing's angle of attack or by
600-595: A beefed-up turbofan derivative of the Pratt & Whitney J58 . The J58 had already successfully proven itself as a high-thrust, high-performance jet engine on the top-secret Lockheed A-12 (and subsequently on the Lockheed SR-71 Blackbird.) Since it was a turbofan, it was deemed to be quieter than a typical turbojet at low altitude and low speed, required no afterburner for takeoff, and allowed reduced power settings. The engines were placed in cylindrical pods with
720-827: A decrease in the critical angle of attack. The latter may be due to slowing down (below stall speed ) or the accretion of ice on the wings (especially if the ice is rough). A stall does not mean that the engine(s) have stopped working, or that the aircraft has stopped moving—the effect is the same even in an unpowered glider aircraft . Vectored thrust in aircraft is used to maintain altitude or controlled flight with wings stalled by replacing lost wing lift with engine or propeller thrust , thereby giving rise to post-stall technology. Because stalls are most commonly discussed in connection with aviation , this article discusses stalls as they relate mainly to aircraft, in particular fixed-wing aircraft. The principles of stall discussed here translate to foils in other fluids as well. A stall
840-507: A deep stall. Two Velocity aircraft crashed due to locked-in deep stalls. Testing revealed that the addition of leading-edge cuffs to the outboard wing prevented the aircraft from getting into a deep stall. The Piper Advanced Technologies PAT-1, N15PT, another canard-configured aircraft, also crashed in an accident attributed to a deep stall. Wind-tunnel testing of the design at the NASA Langley Research Center showed that it
960-462: A delta-shaped canard for aerodynamic trim. During wind-tunnel tests, this design demonstrated substantial shifts in the airplane's center of pressure (C/L). These would require large trim changes as the aircraft changed speed, causing trim drag . A delta wing was substituted which alleviated a portion of the movement, but it was not deemed sufficient. Lockheed knew a variable geometry, swing-wing design could accomplish this goal, but felt it
1080-448: A dive. In these cases, the wings are already operating at a higher angle of attack to create the necessary force (derived from lift) to accelerate in the desired direction. Increasing the g-loading still further, by pulling back on the controls, can cause the stalling angle to be exceeded, even though the aircraft is flying at a high speed. These "high-speed stalls" produce the same buffeting characteristics as 1g stalls and can also initiate
1200-477: A helicopter blade may incur flow that reverses (compared to the direction of blade movement), and thus includes rapidly changing angles of attack. Oscillating (flapping) wings, such as those of insects like the bumblebee —may rely almost entirely on dynamic stall for lift production, provided the oscillations are fast compared to the speed of flight, and the angle of the wing changes rapidly compared to airflow direction. Stall delay can occur on airfoils subject to
1320-408: A high angle of attack and a three-dimensional flow. When the angle of attack on an airfoil is increasing rapidly, the flow will remain substantially attached to the airfoil to a significantly higher angle of attack than can be achieved in steady-state conditions. As a result, the stall is delayed momentarily and a lift coefficient significantly higher than the steady-state maximum is achieved. The effect
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#17328694992991440-439: A leading-edge flap to increase lift at low speeds, and to allow a slight down-elevon deflection. The fuselage, as a result of greater length, changes to the wing design, and attempts to further reduce drag, featured a slight vertical thinning in the fuselage where the wings were, a more prominent wing/body "belly" to carry fuel and cargo, a longer nose, and a refined tail. Since the airplane was not as directionally stable as before,
1560-508: A leafy texture. Lockheed ranked tenth among United States corporations in the value of wartime production contracts. All told, Lockheed and its subsidiary Vega produced 19,278 aircraft during World War II, representing six percent of war production, including 2,600 Venturas , 2,750 Boeing B-17 Flying Fortress bombers (built under license from Boeing ), 2,900 Hudson bombers, and 9,000 Lightnings. During World War II, Lockheed, in cooperation with Trans-World Airlines (TWA), had developed
1680-440: A long, pointed nose that was almost flat on top and curved on the bottom, which allowed for improved supersonic performance, and could be drooped for takeoff and landing to provide adequate visibility. The wing design featured a sharp forward inboard sweep of 80°, with the remaining part of the wing's leading edge swept back 60°, with an overall area of 8,370 ft² (778 m²). The high sweep angles produced powerful vortices on
1800-409: A lower speed. A fixed-wing aircraft can be made to stall in any pitch attitude or bank angle or at any airspeed but deliberate stalling is commonly practiced by reducing the speed to the unaccelerated stall speed, at a safe altitude. Unaccelerated (1g) stall speed varies on different fixed-wing aircraft and is represented by colour codes on the airspeed indicator . As the plane flies at this speed,
1920-434: A mixed-class seating of 230 passengers. The new wing featured a proportionately larger forward delta, with greater refinement to the wing's twist and curvature. Despite having the same wingspan, the wing-area was increased to 9,424 ft² (875 m²), with a slightly reduced 84° sweepback, and an increased 65° main delta wing, with reduced forward sweep along the trailing edge. Unlike previous versions, this aircraft featured
2040-417: A multi-engine non-centreline thrust aircraft), or from less likely sources such as severe turbulence. The net effect is that one wing is stalled before the other and the aircraft descends rapidly while rotating, and some aircraft cannot recover from this condition without correct pilot control inputs (which must stop yaw) and loading. A new solution to the problem of difficult (or impossible) stall-spin recovery
2160-432: A range of weights and flap positions, but the stalling angle of attack is not published. As speed reduces, angle of attack has to increase to keep lift constant until the critical angle is reached. The airspeed at which this angle is reached is the (1g, unaccelerated) stalling speed of the aircraft in that particular configuration. Deploying flaps /slats decreases the stall speed to allow the aircraft to take off and land at
2280-482: A risk of accelerated stalls. When an aircraft such as an Mitsubishi MU-2 is flying close to its stall speed, the sudden application of full power may cause it to roll, creating the same aerodynamic conditions that induce an accelerated stall in turning flight even if the pilot did not deliberately initiate a turn. Pilots of such aircraft are trained to avoid sudden and drastic increases in power at low altitude and low airspeed, as an accelerated stall under these conditions
2400-403: A shorter engine pod to be used and which utilized a new inlet design. This inlet featured minimal external cowl angles and was precisely contoured to allow a high-pressure recovery using no moving parts, and allowed maximum performance with either engine option. To allow additional airflow for noise-reduction, or to aid afterburner performance, a set of suck-in doors was added to the rear portion of
2520-534: A slate of his own choosing, since he was the largest investor. His board nominations included former Texas Senator John Tower , the onetime chairman of the Armed Services Committee , and Admiral Elmo Zumwalt Jr ., a former Chief of Naval Operations. Simmons had first begun accumulating Lockheed stock in early 1989 when deep Pentagon cuts to the defense budget had driven down prices of military contractor stocks, and analysts had not believed he would attempt
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#17328694992992640-437: A small loss in altitude (20–30 m/66–98 ft). It is taught and practised in order for pilots to recognize, avoid, and recover from stalling the aircraft. A pilot is required to demonstrate competency in controlling an aircraft during and after a stall for certification in the United States, and it is a routine maneuver for pilots when getting to know the handling of an unfamiliar aircraft type. The only dangerous aspect of
2760-523: A spin if there is also any yawing. Different aircraft types have different stalling characteristics but they only have to be good enough to satisfy their particular Airworthiness authority. For example, the Short Belfast heavy freighter had a marginal nose drop which was acceptable to the Royal Air Force . When the aircraft were sold to a civil operator they had to be fitted with a stick pusher to meet
2880-401: A stall is a lack of altitude for recovery. A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a spin . A spin can occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on
3000-505: A wedge-shaped splitter, and a squarish intake providing the inlet system for the aircraft. The inlet was designed with the goal of requiring no moving parts, and was naturally stable. To reduce the noise from sonic booms , rather than penetrate the sound barrier at a more ideal 30,000 ft (9,144 m), they intended to penetrate it at 42,000 ft (12,802 m) instead. It would not be possible on hot days, but on normal days this would be achievable. Acceleration would continue through
3120-418: Is 19% higher than V s . According to Federal Aviation Administration (FAA) terminology, the above example illustrates a so-called turning flight stall , while the term accelerated is used to indicate an accelerated turning stall only, that is, a turning flight stall where the airspeed decreases at a given rate. The tendency of powerful propeller aircraft to roll in reaction to engine torque creates
3240-438: Is a condition in aerodynamics and aviation such that if the angle of attack on an aircraft increases beyond a certain point, then lift begins to decrease. The angle at which this occurs is called the critical angle of attack . If the angle of attack increases beyond the critical value, the lift decreases and the aircraft descends, further increasing the angle of attack and causing further loss of lift. The critical angle of attack
3360-429: Is caused by flow separation which, in turn, is caused by the air flowing against a rising pressure. Whitford describes three types of stall: trailing-edge, leading-edge and thin-aerofoil, each with distinctive Cl~alpha features. For the trailing-edge stall, separation begins at small angles of attack near the trailing edge of the wing while the rest of the flow over the wing remains attached. As angle of attack increases,
3480-417: Is dependent upon the airfoil section or profile of the wing, its planform , its aspect ratio , and other factors, but is typically in the range of 8 to 20 degrees relative to the incoming wind ( relative wind ) for most subsonic airfoils. The critical angle of attack is the angle of attack on the lift coefficient versus angle-of-attack (Cl~alpha) curve at which the maximum lift coefficient occurs. Stalling
3600-480: Is increased when the wing surfaces are contaminated with ice or frost creating a rougher surface, and heavier airframe due to ice accumulation. Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack. Attempting to increase the angle of attack at 1g by moving the control column back normally causes the aircraft to climb. However, aircraft often experience higher g-forces, such as when turning steeply or pulling out of
3720-421: Is increased. Early speculation on reasons for the crash of Air France Flight 447 blamed an unrecoverable deep stall, since it descended in an almost flat attitude (15°) at an angle of attack of 35° or more. However, it was held in a stalled glide by the pilots, who held the nose up amid all the confusion of what was actually happening to the aircraft. Canard-configured aircraft are also at risk of getting into
Lockheed L-2000 - Misplaced Pages Continue
3840-447: Is provided by the ballistic parachute recovery system. The most common stall-spin scenarios occur on takeoff ( departure stall) and during landing (base to final turn) because of insufficient airspeed during these maneuvers. Stalls also occur during a go-around manoeuvre if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed. Stall speed
3960-433: Is reduced by the wing and nacelle wakes. He also gives a definition that relates deep stall to a locked-in condition where recovery is impossible. This is a single value of α {\textstyle \alpha } , for a given aircraft configuration, where there is no pitching moment, i.e. a trim point. Typical values both for the range of deep stall, as defined above, and the locked-in trim point are given for
4080-423: Is very difficult to safely recover from. A notable example of an air accident involving a low-altitude turning flight stall is the 1994 Fairchild Air Force Base B-52 crash . Dynamic stall is a non-linear unsteady aerodynamic effect that occurs when airfoils rapidly change the angle of attack. The rapid change can cause a strong vortex to be shed from the leading edge of the aerofoil, and travel backwards above
4200-499: The DC-10 ) strongly opposed the bill and they feared the government would steer contracts to Lockheed to insure loan payments. Admiral Hyman G. Rickover condemned the bill saying it represented "a new philosophy where we privatize profits and socialize losses." The New York Times editorial board held that the Nixon administration was violating its own free enterprise principles by advocating for
4320-550: The Douglas DC-9 Series ;10 by Schaufele. These values are from wind-tunnel tests for an early design. The final design had no locked-in trim point, so recovery from the deep stall region was possible, as required to meet certification rules. Normal stall beginning at the "g break" (sudden decrease of the vertical load factor ) was at α = 18 ∘ {\textstyle \alpha =18^{\circ }} , deep stall started at about 30°, and
4440-694: The GE4 which was an afterburning turbojet with variable guide-vanes, which was actually the less powerful of the two at sea level, but produced more power at high altitudes. Both engines required some degree of afterburner during cruise. Lockheed's design favored the JTF-17A over the GE-4, but there was the risk that GE would win the engine competition and Lockheed would win the SST contract, so they developed new engine pods that could accommodate either engine. Aerodynamic modifications allowed
4560-523: The Imperial Japanese Army . At the beginning of World War II, Lockheed – under the guidance of Clarence (Kelly) Johnson , who is considered one of the best-known American aircraft designers – answered a specification for an interceptor by submitting the P-38 Lightning fighter aircraft, a twin-engined, twin-boom design. The P-38 was the only American fighter aircraft in production throughout
4680-549: The L-049 Constellation , a radical new airliner capable of flying 43 passengers between New York and London at a speed of 300 mph (480 km/h) in 13 hours. Once the Constellation (nicknamed Connie ) went into production, the military received the first production models; after the war, the airlines received their original orders, giving Lockheed more than a year's head-start over other aircraft manufacturers in what
4800-773: The Lockheed Aircraft Company ( spelled phonetically to prevent mispronunciation) in Hollywood. This new company used some of the same technology originally developed for the Model S-1 to design the Vega Model . In March 1928, the company relocated to Burbank, California , and by year's end reported sales exceeding one million dollars. From 1926 to 1928 the company produced over 80 aircraft and employed more than 300 workers who by April 1929 were building five aircraft per week. In July 1929, majority shareholder Fred Keeler sold 87% of
4920-477: The critical (stall) angle of attack . This speed is called the "stall speed". An aircraft flying at its stall speed cannot climb, and an aircraft flying below its stall speed cannot stop descending. Any attempt to do so by increasing angle of attack, without first increasing airspeed, will result in a stall. The actual stall speed will vary depending on the airplane's weight, altitude, configuration, and vertical and lateral acceleration. Propeller slipstream reduces
Lockheed L-2000 - Misplaced Pages Continue
5040-425: The weight of the aircraft plus extra lift to provide the centripetal force necessary to perform the turn: where: To achieve the extra lift, the lift coefficient , and so the angle of attack, will have to be higher than it would be in straight and level flight at the same speed. Therefore, given that the stall always occurs at the same critical angle of attack, by increasing the load factor (e.g. by tightening
5160-528: The "Lockheed Loan". Even after its adoption, a further controversy developed when the Emergency Loan Guarantee Board set up by the Executive branch to oversee the loan refused to allow Congress' General Accounting Office to examine its records. They argued that the office was attempting "interference in the decision-making process" amounting to an effort to "bully" and "harass" the board. This claim
5280-593: The 1970s. Drowning in debt, in 1971 Lockheed (then the largest US defense contractor) asked the US government for a loan guarantee, to avoid insolvency. Lockheed argued that a government bailout was necessary due to the company's value for U.S. national security. On May 13, 1971, the Richard Nixon administration sent a bill titled "The Emergency Loan Guarantee Act" to Congress requesting a $ 250 million loan guarantee for Lockheed and its L-1011 Tristar airbus program. The measure
5400-456: The 1970s. In late 1975 and early 1976, a subcommittee of the U.S. Senate led by Senator Frank Church concluded that members of the Lockheed board had paid members of friendly governments to guarantee contracts for military aircraft. In 1976, it was publicly revealed that Lockheed had paid $ 22 million in bribes to foreign officials in the process of negotiating the sale of aircraft including
5520-535: The Constellation obsolete. However, the design proved underpowered. The company sought to purchase Convair in 1946, but the sale was blocked by the SEC . In 1943, Lockheed began, in secrecy, development of a new jet fighter at its Burbank facility. This fighter, the Lockheed P-80 Shooting Star , became the first American jet fighter to score a kill. It also recorded the first jet-to-jet aerial kill, downing
5640-758: The F-104 Starfighter, the so-called Deal of the Century. The scandal caused considerable political controversy in West Germany , the Netherlands , Italy, and Japan. In the US, the scandal led to passage of the Foreign Corrupt Practices Act , and nearly led to the ailing corporation's downfall (it was already struggling due to the poor sales of the L-1011 airliner). Haughton resigned his post as chairman. In
5760-601: The Lockheed Aircraft Company to Detroit Aircraft Corporation . In August 1929, Allan Loughead resigned. The Great Depression ruined the aircraft market, and Detroit Aircraft went bankrupt. A group of investors headed by brothers Robert and Courtland Gross, and Walter Varney , bought the company out of receivership in 1932. The syndicate bought the company for a mere $ 40,000 ($ 858,000 in 2023). Ironically, Allan Loughead himself had planned to bid for his own company, but had raised only $ 50,000 ($ 824,000), which he felt
5880-731: The Poseidon and Trident nuclear missiles. Lockheed developed the F-104 Starfighter in the late 1950s, the world's first Mach 2 fighter jet. In the early 1960s, the company introduced the C-141 Starlifter four-engine jet transport. During the 1960s, Lockheed began development for two large aircraft: the C-5 Galaxy military transport and the L-1011 TriStar wide-body civil airliner. Both projects encountered delays and cost overruns. The C-5
6000-481: The Transfer Orbit Stage (under subcontract to Orbital Sciences Corporation ) and various satellite models. Lockheed's operations were divided between several groups and divisions, many of which continue to operate within Lockheed A partial listing of aircraft and other vehicles produced by Lockheed. Stall (flight) In fluid dynamics , a stall is a reduction in the lift coefficient generated by
6120-676: The U-2 (late 1950s), SR-71 Blackbird (1962) and F-117 Nighthawk stealth fighter (1978). The Skunk Works often created high-quality designs in a short time and sometimes with limited resources. In 1954, the Lockheed C-130 Hercules , a durable four-engined transport, flew for the first time. This type remains in production today. In 1956, Lockheed received a contract for the development of the Polaris Submarine Launched Ballistic Missile ( SLBM ); it would be followed by
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#17328694992996240-589: The US Government issued new requirements regarding the SST Program which required Lockheed to modify their design, by now called the L-2000-2 . The new design had numerous modifications to the wing; one change was rounding the front of the forward delta in order to eliminate the pitch-up tendency. To increase high-speed aerodynamic efficiency, the wing's thickness was reduced to 2.3%, the leading edges were made sharper,
6360-404: The V S values above, always refers to straight and level flight, where the load factor is equal to 1g. However, if the aircraft is turning or pulling up from a dive, additional lift is required to provide the vertical or lateral acceleration, and so the stall speed is higher. An accelerated stall is a stall that occurs under such conditions. In a banked turn , the lift required is equal to
6480-597: The aircraft from recovering from the stall. Aircraft with rear-mounted nacelles may also exhibit a loss of thrust . T-tail propeller aircraft are generally resistant to deep stalls, because the prop wash increases airflow over the wing root, but may be fitted with a precautionary vertical tail booster during flight testing , as happened with the A400M . Trubshaw gives a broad definition of deep stall as penetrating to such angles of attack α {\textstyle \alpha } that pitch control effectiveness
6600-425: The angle of attack exceeds the critical angle, the lift produced by the airfoil decreases. The information in a graph of this kind is gathered using a model of the airfoil in a wind tunnel . Because aircraft models are normally used, rather than full-size machines, special care is needed to make sure that data is taken in the same Reynolds number regime (or scale speed) as in free flight. The separation of flow from
6720-438: The angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). The pilot will notice the flight controls have become less responsive and may also notice some buffeting, a result of the turbulent air separated from the wing hitting the tail of the aircraft. In most light aircraft , as the stall is reached, the aircraft will start to descend (because
6840-575: The civil requirements. Some aircraft may naturally have very good behaviour well beyond what is required. For example, first generation jet transports have been described as having an immaculate nose drop at the stall. Loss of lift on one wing is acceptable as long as the roll, including during stall recovery, doesn't exceed about 20 degrees, or in turning flight the roll shall not exceed 90 degrees bank. If pre-stall warning followed by nose drop and limited wing drop are naturally not present or are deemed to be unacceptably marginal by an Airworthiness authority
6960-656: The company should be allowed to go into bankruptcy citing the recent decision to leave Penn Central railroad to that fate, and the fact that the airbus program at issue was commercial rather than military. Naval scholar Thomas Paul Stanton notes that the opposition to the bill held it was "the beginning of the socialization of the American aircraft and aerospace industry." Proponents responded by claiming "this socializing process had taken place many years before", and some witnesses before Congress discounted "the very notion of 'free enterprise'." Treasury Secretary Connally pointed to
7080-417: The crash of the prototype BAC 1-11 G-ASHG on 22 October 1963, which killed its crew. This led to changes to the aircraft, including the installation of a stick shaker (see below) to clearly warn the pilot of an impending stall. Stick shakers are now a standard part of commercial airliners. Nevertheless, the problem continues to cause accidents; on 3 June 1966, a Hawker Siddeley Trident (G-ARPY),
7200-479: The critical angle of attack is reached (which in early-20th century aviation was called the "burble point"). This angle is 17.5 degrees in this case, but it varies from airfoil to airfoil. In particular, for aerodynamically thick airfoils (thickness to chord ratios of around 10%), the critical angle is higher than with a thin airfoil of the same camber . Symmetric airfoils have lower critical angles (but also work efficiently in inverted flight). The graph shows that, as
7320-404: The deep stall after deploying the anti-spin parachute but crashed after being unable to jettison the chute or relight the engines. One of the test pilots was unable to escape from the aircraft in time and was killed. On 26 July 1993, a Canadair CRJ-100 was lost in flight testing due to a deep stall. It has been reported that a Boeing 727 entered a deep stall in a flight test, but the pilot
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#17328694992997440-597: The development of a commercial airliner to compete with the Anglo-French Concorde then under development. The director of the Federal Aviation Administration (FAA), Najeeb Halaby , elected to improve on the Concorde's design rather than compete head-to-head with it. The SST , which might have represented a significant advance over the Concorde, was intended to carry 250 passengers (a large number at
7560-444: The downwash pattern associated with swept/tapered wings. To delay tip stall the outboard wing is given washout to reduce its angle of attack. The root can also be modified with a suitable leading-edge and airfoil section to make sure it stalls before the tip. However, when taken beyond stalling incidence the tips may still become fully stalled before the inner wing despite initial separation occurring inboard. This causes pitch-up after
7680-503: The entirety of American involvement in the war, from Pearl Harbor to Victory over Japan Day . It filled ground-attack, air-to-air, and even tactical bombing roles in all theaters of the war in which the United States operated. The P-38 was responsible for shooting down more Japanese aircraft than any other U.S. Army Air Forces type during the war; it is particularly famous for being the aircraft type that shot down Japanese Admiral Isoroku Yamamoto 's airplane. The Lockheed Vega factory
7800-455: The faltering economy and worries about unemployment while testifying "the time has come within the United States when we have to look at things differently. Free enterprise is just not all that free." Questions arose whether letting Lockheed fail would be bad for the market due to decreased competition or good by screening out inefficient competitors and mismanagement. Lockheed's competitors, McDonnell Douglas and General Electric (collaborators on
7920-533: The late 1980s, leveraged buyout specialist Harold Simmons conducted a widely publicized but unsuccessful takeover attempt on the Lockheed Corporation, having gradually acquired almost 20 percent of its stock. Lockheed was attractive to Simmons because one of its primary investors was the California Public Employees' Retirement System (CalPERS), the pension fund of the state of California. At
8040-442: The leading edge which increased lift at moderate to high angles of attack , yet still retained stable airflow over the control surfaces during a stall . These vortices also provided good directional control as well, which was somewhat deficient with the nose drooped at low speeds. The wing, while only 3% thick, provided substantial lift due to its large area, which, aided by vortex lift, allowed takeoff and landing speeds comparable to
8160-432: The lift to fall from its peak value. Piston-engined and early jet transports had very good stall behaviour with pre-stall buffet warning and, if ignored, a straight nose-drop for a natural recovery. Wing developments that came with the introduction of turbo-prop engines introduced unacceptable stall behaviour. Leading-edge developments on high-lift wings, and the introduction of rear-mounted engines and high-set tailplanes on
8280-407: The loan. (Later, historian Stephen J. Whitfield viewed the passage of the loan guarantee as a support for the argument that America was shifting away from Lockean liberalism. ) Following a fierce debate, Vice President Spiro T. Agnew cast a tie-breaking vote in favor of the measure on August 2, 1971. President Nixon signed the bill into law on August 9, 1971 - which became colloquially known as
8400-413: The locked-in unrecoverable trim point was at 47°. The very high α {\textstyle \alpha } for a deep stall locked-in condition occurs well beyond the normal stall but can be attained very rapidly, as the aircraft is unstable beyond the normal stall and requires immediate action to arrest it. The loss of lift causes high sink rates, which, together with the low forward speed at
8520-428: The major US aviation firms spent at least some time in the 1950s considering SST designs. Lockheed's first attempts date to 1958. Lockheed sought an airplane with cruise speeds of around 2,000 miles per hour (3,200 km/h) with takeoff and landing speeds that compared to large subsonic jets of the same era. Early designs followed Lockheed's tapered straight wing, similar to the one used on the F-104 Starfighter , with
8640-409: The mean angle of attack of the wings is beyond the stall a spin , which is an autorotation of a stalled wing, may develop. A spin follows departures in roll, yaw and pitch from balanced flight. For example, a roll is naturally damped with an unstalled wing, but with wings stalled the damping moment is replaced with a propelling moment. The graph shows that the greatest amount of lift is produced as
8760-482: The medium version featured transatlantic capability with 220 passengers. Despite the fuselage length changes, there was no appreciable increase in the risk of the aircraft pitching upwards too far (over-rotation) on takeoff. By 1966, the design took on its final form as the L-2000-7A and L-2000-7B . The L-2000-7A featured a re-designed wing and fuselage lengthened to 273 ft (83 m). The longer fuselage allows for
8880-410: The need for the canard, and re-shaped the wing into a double-delta shape with a mild twist and camber . This, along with careful shaping of the fuselage, was able to control the shift in the center of pressure caused by the highly swept forward part of the wing developing lift supersonically. The engines were shifted from being buried in the wings to individual pods slung below the wings. The new design
9000-434: The next generation of jet transports, also introduced unacceptable stall behaviour. The probability of achieving the stall speed inadvertently, a potentially hazardous event, had been calculated, in 1965, at about once in every 100,000 flights, often enough to justify the cost of development of warning devices, such as stick shakers, and devices to automatically provide an adequate nose-down pitch, such as stick pushers. When
9120-430: The normal stall, give a high α {\textstyle \alpha } with little or no rotation of the aircraft. BAC 1-11 G-ASHG, during stall flight tests before the type was modified to prevent a locked-in deep-stall condition, descended at over 10,000 feet per minute (50 m/s) and struck the ground in a flat attitude moving only 70 feet (20 m) forward after initial impact. Sketches showing how
9240-449: The pilot has actually stalled the aircraft. This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) or generic flight manuals describe stalling in terms of airspeed . This is because all aircraft are equipped with an airspeed indicator , but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer (and is required for certification by flight testing) for
9360-403: The plane featured a ventral fin, located on the underside of the trailing fuselage. The L-2000-7B was extended to 293 ft (89 m), utilizing a lengthened cabin and a more pronounced upward-curving tail to reduce the chance of the tail striking the runway during over-rotation. Both designs had the same maximum weight of 590,000 lb (267,600 kg), and the aerodynamic lift-to-drag ratio
9480-497: The pod. To provide mid-air braking capability for rapid deceleration and rapid descents, and to assist ground braking, part of the nozzle could be employed as a thrust reverser at speeds below Mach 1.2. The pods were also repositioned on the new wing to better shield them from abrupt changes in airflow. The additional thrust from the new engines allowed supersonic penetration to be delayed until up to 45,000 ft (13,716 m) under virtually all conditions. Since at this point
9600-463: The possibility of supersonic overland flight was still considered to be an option, Lockheed also considered larger, shorter-ranged versions of the L-2000-2B. All designs weighed exactly the same, with a new tail design, changes to the fuselage length, extensions to the forward delta, increased capacity, and variations in fuel capacity. The largest version featured capacity for 250 domestic passengers, while
9720-410: The ramifications of the Lockheed loan guarantee soon resurfaced in late 1975 with discussions on possible aid to New York City during its fiscal crisis . Lockheed finished paying off the $ 1.4 billion loan in 1977, along with about $ 112.22 million in loan guarantee fees. The Lockheed bribery scandals were a series of illegal bribes and contributions made by Lockheed officials from the late 1950s to
9840-473: The real life counterparts often tend to overestimate the aerodynamic stall angle of attack. High-pressure wind tunnels are one solution to this problem. In general, steady operation of an aircraft at an angle of attack above the critical angle is not possible because, after exceeding the critical angle, the loss of lift from the wing causes the nose of the aircraft to fall, reducing the angle of attack again. This nose drop, independent of control inputs, indicates
9960-421: The rear delta was enlarged considerably; to increase the payload, the trailing edge featured a forward sweep of 10°, extending the inner part of the wing rearward. The new nose reduced the overall length to 214 ft (65.2 m) while retaining virtually the same internal dimensions. Wingspan was identical as before, and despite the thinner wing, the increased wing area of 9,026 ft² (838.5 m²) allowed
10080-587: The same takeoff performance. The airplane's overall lift-to-drag ratio increased from 7.25 to 7.94. During the course of the L-2000-2's development, the engine previously selected by Lockheed was no longer deemed acceptable. During the time frame between the L-2000-1 and L-2000-2, Pratt and Whitney designed a new afterburning turbofan called the JTF-17A , which produced greater amounts of thrust. General Electric developed
10200-422: The separated regions on the top of the wing increase in size as the flow separation moves forward, and this hinders the ability of the wing to create lift. This is shown by the reduction in lift-slope on a Cl~alpha curve as the lift nears its maximum value. The separated flow usually causes buffeting. Beyond the critical angle of attack, separated flow is so dominant that additional increases in angle of attack cause
10320-442: The sound barrier to Mach 1.15, at which point sonic booms would be audible on the ground. The plane would climb precisely to minimize sonic boom levels. After an initial level-off at around 71,500 ft (21,793 m), the plane would cruise climb upwards, ultimately reaching 76,500 ft (23,317 m). Descents would also be performed in a precise way to reduce sonic boom levels until subsonic speeds were reached. By 1964,
10440-458: The stall and entry to a super-stall on those aircraft with super-stall characteristics. Span-wise flow of the boundary layer is also present on swept wings and causes tip stall. The amount of boundary layer air flowing outboard can be reduced by generating vortices with a leading-edge device such as a fence, notch, saw tooth or a set of vortex generators behind the leading edge. Fixed-wing aircraft can be equipped with devices to prevent or postpone
10560-502: The stall speed by energizing the flow over the wings. Speed definitions vary and include: An airspeed indicator, for the purpose of flight-testing, may have the following markings: the bottom of the white arc indicates V S0 at maximum weight, while the bottom of the green arc indicates V S1 at maximum weight. While an aircraft's V S speed is computed by design, its V S0 and V S1 speeds must be demonstrated empirically by flight testing. The normal stall speed, specified by
10680-437: The stalling behaviour has to be made good enough with airframe modifications or devices such as a stick shaker and pusher. These are described in "Warning and safety devices". Stalls depend only on angle of attack, not airspeed . However, the slower an aircraft flies, the greater the angle of attack it needs to produce lift equal to the aircraft's weight. As the speed decreases further, at some point this angle will be equal to
10800-405: The sweep angles were changed from 80/60° to 85/62°, and substantial twist and camber were added to the forward delta; much of the rear delta was twisted upwards to allow the elevons to remain flush at Mach 3.0. In addition, wing/body fairings were added on the underside of the fuselage where the wings are located, allowing a more normally shaped nose to be used. To retain low-speed performance,
10920-561: The takeover since he was also at the time pursuing control of Georgia Gulf . Merger talks between Lockheed and Martin Marietta began in March 1994, with the companies announcing their $ 10 billion planned merger on August 30, 1994. The headquarters for the combined companies would be at Martin Marietta headquarters in North Bethesda, Maryland . The deal was finalized on March 15, 1995, when
11040-525: The time, more than twice as many as Concorde), fly at Mach 2.7-3.0, and have a range of 4,000 mi (7,400 km). The program was launched on June 5, 1963, and the FAA estimated that by 1990 there would be a market for 500 SSTs. Boeing , Lockheed , and North American officially responded. North American's design was soon rejected, but the Boeing and Lockheed designs were selected for further study. Most of
11160-458: The time, the New York Times said, "Much of Mr. Simmons's interest in Lockheed is believed to stem from its pension plan, which is over funded by more than $ 1.4 billion. Analysts said he might want to liquidate the plan and pay out the excess funds to shareholders, including himself." Citing the mismanagement by its chairman, Daniel M. Tellep , Simmons stated a wish to replace its board with
11280-423: The turn) the critical angle will be reached at a higher airspeed: where: The table that follows gives some examples of the relation between the angle of bank and the square root of the load factor. It derives from the trigonometric relation ( secant ) between L {\displaystyle L} and W {\displaystyle W} . For example, in a turn with bank angle of 45°, V st
11400-492: The two companies' shareholders approved the merger. The segments of the two companies not retained by the new company formed the basis for L-3 Communications , a mid-size defense contractor in its own right. Lockheed Martin also later spun off the materials company Martin Marietta Materials . The company's executives received large bonuses directly from the government as a result of the merger. Norman R. Augustine who
11520-505: The upper wing surface at high angles of attack is quite different at low Reynolds number from that at the high Reynolds numbers of real aircraft. In particular at high Reynolds numbers the flow tends to stay attached to the airfoil for longer because the inertial forces are dominant with respect to the viscous forces which are responsible for the flow separation ultimately leading to the aerodynamic stall. For this reason wind tunnel results carried out at lower speeds and on smaller scale models of
11640-412: The wing is no longer producing enough lift to support the aircraft's weight) and the nose will pitch down. Recovery from the stall involves lowering the aircraft nose, to decrease the angle of attack and increase the air speed, until smooth air-flow over the wing is restored. Normal flight can be resumed once recovery is complete. The maneuver is normally quite safe, and, if correctly handled, leads to only
11760-411: The wing tip, well aft of the c.g. If the tip stalls first the balance of the aircraft is upset causing dangerous nose pitch up . Swept wings have to incorporate features which prevent pitch-up caused by premature tip stall. A swept wing has a higher lift coefficient on its outer panels than on the inner wing, causing them to reach their maximum lift capability first and to stall first. This is caused by
11880-434: The wing wake blankets the tail may be misleading if they imply that deep stall requires a high body angle. Taylor and Ray show how the aircraft attitude in the deep stall is relatively flat, even less than during the normal stall, with very high negative flight-path angles. Effects similar to deep stall had been known to occur on some aircraft designs before the term was coined. A prototype Gloster Javelin ( serial WD808 )
12000-415: The wing. The vortex, containing high-velocity airflows, briefly increases the lift produced by the wing. As soon as it passes behind the trailing edge, however, the lift reduces dramatically, and the wing is in normal stall. Dynamic stall is an effect most associated with helicopters and flapping wings, though also occurs in wind turbines, and due to gusting airflow. During forward flight, some regions of
12120-691: The world in 1937. Subsequent designs, the Lockheed Model 12 Electra Junior and the Lockheed Model 14 Super Electra expanded their market. The Lockheed Model 14 formed the basis for the Hudson bomber, which was supplied to both the British Royal Air Force and the United States military before and during World War II . Its primary role was submarine hunting. The Model 14 Super Electra were sold abroad, and more than 100 were license-built in Japan for use by
12240-618: Was lost to deep stall ; deep stall is suspected to be cause of another Trident (the British European Airways Flight 548 G-ARPI ) crash – known as the "Staines Disaster" – on 18 June 1972, when the crew failed to notice the conditions and had disabled the stall-recovery system. On 3 April 1980, a prototype of the Canadair Challenger business jet crashed after initially entering a deep stall from 17,000 ft and having both engines flame-out. It recovered from
12360-404: Was able to rock the airplane to increasingly higher bank angles until the nose finally fell through and normal control response was recovered. The crash of West Caribbean Airways Flight 708 in 2005 was also attributed to a deep stall. Deep stalls can occur at apparently normal pitch attitudes, if the aircraft is descending quickly enough. The airflow is coming from below, so the angle of attack
12480-463: Was an American aerospace manufacturer . Lockheed was founded in 1926 and merged in 1995 with Martin Marietta to form Lockheed Martin . Its founder, Allan Lockheed , had earlier founded the similarly named but otherwise-unrelated Loughead Aircraft Manufacturing Company , which was operational from 1912 to 1920. Allan Loughead and his brother Malcolm Loughead had operated an earlier aircraft company, Loughead Aircraft Manufacturing Company , which
12600-686: Was at the time CEO of Martin Marietta received an $ 8.2 million bonus. Both companies contributed important products to the new portfolio. Lockheed products included the Trident missile , P-3 Orion maritime patrol aircraft , U-2 and SR-71 reconnaissance airplanes , F-117 Nighthawk , F-16 Fighting Falcon , F-22 Raptor , C-130 Hercules , A-4AR Fightinghawk and the DSCS-3 satellite. Martin Marietta products included Titan rockets , Sandia National Laboratories (management contract acquired in 1993), Space Shuttle External Tank , Viking 1 and Viking 2 landers,
12720-585: Was built in any number (141 aircraft) was the Vega first built in 1927, best known for its several first- and record-setting flights by, among others, Amelia Earhart , Wiley Post , and George Hubert Wilkins . In the 1930s, Lockheed spent $ 139,400 ($ 2.29 million) to develop the Model 10 Electra , a small twin-engined transport. The company sold 40 in the first year of production. Amelia Earhart and her navigator, Fred Noonan , flew it in their failed attempt to circumnavigate
12840-693: Was built to vague initial requirements and suffered from structural weaknesses, which Lockheed was forced to correct at its own expense. The TriStar competed for the same market as the McDonnell Douglas DC-10 ; delays in Rolls-Royce engine development caused the TriStar to fall behind the DC-10. The C-5 and L-1011 projects, the canceled U.S. Army AH-56 Cheyenne helicopter program, and embroiled shipbuilding contracts caused Lockheed to lose large sums of money during
12960-663: Was considered more advanced, representing a greater lead over the Concorde and thus more fitting to the original design mandate. Boeing eventually changed its advanced variable-geometry wing design to a simpler delta-wing similar to Lockheed's design, but with a tail. The Boeing SST was ultimately cancelled on May 20, 1971 after the US Congress stopped federal funding for the SST program on March 24, 1971. Data from General characteristics Performance Aircraft of comparable role, configuration, and era Related lists Lockheed Corporation The Lockheed Corporation
13080-433: Was denied by Comptroller General Elmer B. Staats , and efforts were made by Senator William Proxmire to get Treasury Secretary John Connally to testify due to the suspicion that the loan guarantee was in jeopardy. The editorial board of The New York Times blasted the situation, citing it as another argument against the propriety of the loan guarantee and the precedent it set for other failing companies. The debate around
13200-428: Was designated L-2000-1 and was 223 ft (70 m) long with a narrow-body 132 in (335.2 cm) wide fuselage to meet aerodynamic requirements, allowing for passenger seating of five abreast seating in coach and a four-abreast arrangement in first-class seating. A typical mixed-class seating layout would equal around 170 passengers, with high-density layouts exceeding 200 passengers. The L-2000-1 featured
13320-400: Was easily foreseen as the post-war modernization of civilian air travel. The Constellation's performance set new standards which transformed the civilian transportation market. Its signature tri-tail was the result of many initial customers not having hangars tall enough for a conventional tail. Lockheed produced a larger transport, the double-decked R6V Constitution , which was intended to make
13440-420: Was first noticed on propellers . A deep stall (or super-stall ) is a dangerous type of stall that affects certain aircraft designs, notably jet aircraft with a T-tail configuration and rear-mounted engines. In these designs, the turbulent wake of a stalled main wing, nacelle-pylon wakes and the wake from the fuselage "blanket" the horizontal stabilizer, rendering the elevators ineffective and preventing
13560-508: Was hotly debated in the US Senate. The chief antagonist was Senator William Proxmire (D-Wis), the nemesis of Lockheed and its chairman, Daniel J. Haughton. Some of the debate in Congress developed over what conditions should be attached to the bailout. Senator Alan Cranston demanded that the management be forced to step down, lest it set a precedent rewarding wasteful spending. Others argued that
13680-459: Was increased to 8:1. Full-scale mock-ups of the Boeing 2707-200 and L-2000-7 designs were presented to the FAA, and on December 31, 1966 the Boeing design was selected. The Lockheed design was judged simpler to produce and less risky, but its performance during takeoff and at high speed was slightly lower. Because of the JTF-17A, the L-2000-7 was also predicted to be louder as well. The Boeing design
13800-538: Was located next to Burbank's Union Airport which it had purchased in 1940. During the war, the entire area was camouflaged in case of enemy reconnaissance. The factory was hidden beneath a huge burlap tarpaulin painted to depict a peaceful semi-rural neighborhood, replete with rubber automobiles. Hundreds of fake trees, shrubs, buildings, and even fire hydrants were positioned to give a three-dimensional appearance. The trees and shrubs were created from chicken wire treated with an adhesive and covered with feathers to provide
13920-578: Was lost in a crash on 11 June 1953 to a "locked-in" stall. However, Waterton states that the trimming tailplane was found to be the wrong way for recovery. Low-speed handling tests were being done to assess a new wing. Handley Page Victor XL159 was lost to a "stable stall" on 23 March 1962. It had been clearing the fixed droop leading edge with the test being stall approach, landing configuration, C of G aft. The brake parachute had not been streamed, as it may have hindered rear crew escape. The name "deep stall" first came into widespread use after
14040-583: Was operational from 1912 to 1920. The company built and operated aircraft for paying passengers on sightseeing tours in California and had developed a prototype for the civil market, but folded in 1920 due to the flood of surplus aircraft deflating the market after World War I . Allan went into the real estate market while Malcolm had meanwhile formed a successful company marketing brake systems for automobiles. On December 13, 1926, Allan Loughead, John Northrop , Kenneth Kay and Fred Keeler secured funding to form
14160-425: Was too heavy: they preferred a fixed-wing solution. In a worst-case scenario, they were willing to design a fixed-wing aircraft using fuel for ballast. By 1962, Lockheed arrived at a highly swept, cranked-arrow design featuring four engine pods buried in the wings and a canard. The improvement was closer to their goal, but still not optimal. By 1963, they extended the leading edge of the wing forward to eliminate
14280-565: Was too small a sum for a serious bid. In 1934, Robert E. Gross was named chairman of the new company, the Lockheed Aircraft Corporation, which was headquartered at what is now the airport in Burbank, California . His brother Courtlandt S. Gross was a co-founder and executive, succeeding Robert as chairman following his death in 1961. The company was named the Lockheed Corporation in 1977. The first successful construction that
14400-402: Was vulnerable to a deep stall. In the early 1980s, a Schweizer SGS 1-36 sailplane was modified for NASA 's controlled deep-stall flight program. Wing sweep and taper cause stalling at the tip of a wing before the root. The position of a swept wing along the fuselage has to be such that the lift from the wing root, well forward of the aircraft center of gravity (c.g.), must be balanced by
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