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Autogiro

Autogiro

An autogyro (only an autogiro™ when produced by the Cierva Autogiro Company or one of its licensees (see below), sometimes called a gyroplane, gyrocopter™, or rotaplane) is an aircraft supported in flight by an unpowered rotor. Though the autogyro resembles a helicopter, it is driven in flight by an engine-powered propeller similar to that of an airplane. Often mistakenly characterized as a hybrid between an airplane and helicopter, the autogyro is a distinct type of aircraft that made its first successful flight on 17 January 1923 at Cuatro Vientos Airfield in Madrid, Spain, predating the first successful helicopter by 13 years. All helicopters utilize rotor technology first developed for the autogiro: the helicopter owes its existence to the brilliant work conducted by Juan de la Cierva and his associates. helicopter

General characteristics

Autogyros can take off and land in significantly smaller areas compared to airplanes, and depending on the model, can operate from helipads. When fitted with a jump start feature, an autogyro can takeoff from a standing start into forward flight, accelerate in ground effect, then commence a climb; hovering capability is not available however since the rotor is always declutched before the autogyro leaves the ground. If rotor collective pitch control is provided, an autogyro can execute a collective flare; otherwise landings are always made with a cyclic flare. Certificated autogyros flown by trained and qualified pilots are notably safe. As intended by la Cierva, the rotor always turns regardless of the airspeed of the aircraft, though as airspeed decreases rotor rpm reduces to a minimum value at zero airspeed. Reduction of engine power increases the descent rate, though the autogyro remains fully stable and controllable. Directional control, provided by a rudder, can become nonexistent at low airspeed and low propeller thrust. For example, the Air and Space 18A gyroplane rudder rapidly loses effectiveness below 50mph airspeed when the engine is throttled. Most autogyros are neither efficient nor very fast (for one exception see Wing Commander Ken Wallis, below - around 120mph on 60bhp). Fixed-wing aircraft are faster and use less fuel over the same distance, helicopters generally require more power (and hence fuel) than a fixed wing aircraft (or autogyro) for the same top speed/load etc. It must be noted, however, that large scale autogyro development ceased prior to WW2 and with few exceptions has not benefitted from rotary wing developments applied to helicopters. Gyroplanes are typically more maneuverable than fixed-wing aircraft, but do not hover as does a helicopter. When helicopters became practical, autogyros were neglected for nearly 30 years. They were however at one time used extensively by major newspapers and by the US Postal Service for mail service between the Camden, NJ airport and the top of the post office building in downtown Philadelphia, PA. As the infrastructure for service, repair, training and building increases the number of autogyro users may increase. Autogyros can be of tractor configuration with the engine(s) and propeller(s) at the front of the fuselage, or pusher configuration with the engine(s) and propeller(s) at the rear of the fuselage. Early autogyros were fitted with fixed rotor hubs, small fixed-wings and airplane-type control surfaces. At the low airspeed at which autogyros can easily operate, the airplane-type control surfaces became ineffective and could readily lead to loss of control, particularly during landing. The direct control rotor hub, which could be tilted in any direction by the pilot, was first developed on the Cierva C.19 Mk.V and saw production on the Cierva C.30 series of 1934. Rotor drives initially took the form of a rope wrapped around the rotor axle and then pulled by a team of men to accelerate the rotor prior to a long taxi to bring the rotor up to speed sufficient for takeoff. The next innovation was a fully deflectable horizontal stabilizer that directed propeller slipstream into the rotor. Cierva license, Pitcairn-Cierva Autogiro Company of Willow Grove, PA, finally solved the problem with a light mechanical transmission driven by the engine. The Groen Brothers Hawk 4 of the late 1992 is advertised as possessing Ultra-Short Take-Off and Landing (USTOL) capabilty, enabling the aircraft to take off and land within a very short distance (25 feet). This is merely a new name for performance autogyros have always possessed.

History

Juan de la Cierva, a Spanish engineer and aeronautical enthusiast, invented the first successful rotorcraft, which he named autogiro in 1923. His craft used a tractor-mounted forward propeller and engine, a rotor mounted on a mast, and a horizontal and vertical stabilizer. His first three designs, C.1, C.2, and C.3, were unstable due to aerodynamic and structural deficiencies in their rotors. His fourth design, the C.4, fitted with flapping hinges to attach each rotor blade to the hub, made the first successful flight of a rotary-wing aircraft, piloted by Alejandro Gomez Spencer, on 17 January 1923. The C.4 was fitted with conventional airplane ailerons, elevators and rudder for control. During a later test flight, the engine failed shortly after takeoff and the aircraft descended slowly and steeply to a safe landing, validating la Cierva's efforts to produce an aircraft that could be flown safely at low airspeeds. Juan de la Cierva This success eventually became well known and after further limited Autogiro development in Spain, la Cierva accepted an offer from Scottish industrialist James G. Weir to establish the Cierva Autogiro Company in England following a 20 October 1925 demonstration to the British Air Ministry at Farnborough. Test pilot for these flights was Frank T. Courtney. From this point on, Britain became the world center of rotary-wing aircraft development. A crash due to blade root failure in February 1927 led to an improvement in rotor hub design. Adjacent the flapping hinge a drag hinge was incorporated to allow each blade to slightly oscillate horizontally and relieve inplane stresses generated as a byproduct of flapping motion. Development work on means to accelerate the rotor prior to takeoff was also undertaken. Efforts with the C.11 in Spain showed that development of a light and efficient mechanical rotor transmission was not a trivial undertaking and led to the adoption of the intermediate expedient of inclining the horizontal stabilizer to redirect the propeller slipstream into the rotor while on the ground. This feature was later introduced on the production C.19 series of 1929. Further Autogiro development led to the Cierva C.8 L.IV which on 18 September 1928 made the first rotary-wing aircraft crossing of the English Channel followed by an extensive tour of Europe. US industrialist Harold F. Pitcairn had in 1925 visited la Cierva in Spain upon learning of the successful flights of the Autogiro; in 1928 he visited la Cierva in England after taking a C.8 L.IV test flight piloted by Arthur H.C.A. Rawson and being particularly impressed with the Autogiro's safe vertical descent capability, purchased a C.8 L.IV with a Wright Whirlwind engine. Arriving in the United States on 11 December 1928 accompanied by Rawson, this Autogiro was redesignated C.8W. (Further editing of the following to continue) The Cierva "Autodynamic" rotor used drag hinges with offset axes to perform this to good effect with great simplicity, but the Pitcairn collective pitch control advanced the "jump" ability. The C-19 technology was licensed to a number of manufacturers, including Harold Pitcairn in the U.S. (in 1928) and Focke-Achgelis of Germany. In 1931 Amelia Earhart flew a Pitcairn PCA-2 to a then world altitude record of 18,415 feet (5613 m). In World War II, Germany pioneered a very small gyroglider "rotor-kite", the Focke-Achgelis Fa 330 "Bachstelze" (Water-wagtail), towed by submarines to provide aerial surveillance. It's reported that German gyro pilots were often forgotten in the heat of battle when the submarine dived suddenly. The Japanese also developed the Kayaba Ka-1 Autogyro for reconnaissance, artillery-spotting, and anti-submarine uses. The autogyro was resurrected post WW2 when Dr. Igor Bensen (a doctor of Divinity) saw a captured German U-Boat's gyroglider, and was fascinated by its characteristics. At work he was tasked with the analysis of the British "Rotachute" gyro glider designed by expatriate Austrian Raoul Hafner. This led him to adapt the design for his own purposes and eventually market the B-7. Post WW2 autogyros, such as the Bensen B-8M gyrocopter, generally use a pusher configuration for simplicity and to increase visibility for the pilot. For greater simplicity, they generally lack both variable-pitch rotors and powered rotors. It must be noted that Bensen autogyros and its derivatives have established an abysmal safety record due to their deficient stability and control characteristics greatly worsened by use of a teetering rotor, and their marketing as a build it yourself and teach yourself how to fly it aircraft. Three FAA-certified designs, Umbaugh U-18/Air and Space 18A of 1965, Avian 2-180 of 1967, and McCulloch J-2 or 1972 have for various reasons been commercial failures.

Bensen's design

The Bensen Gyrocopter™, the protoype of many post WW2 gyroplanes, actually consists of three versions, the B-6, B-7 and B-8. All three were designed in both unpowered and powered forms. The basic design is a simple frame of square aluminum or galvanized steel tubing, reinforced with triangles of lighter tubing. It is arranged so that the stress falls on the tubes, or special fittings, not the bolts. All welds or soldered structural joints should be inspected. The rotor is on the top of the vertical mast. The outlying fixed wheels are mounted on an axle (of tubing). The front-to-back keel (more tubing) mounts the forward wheel (which casters), seat, other tubes, engine and a vertical stabilizer. Some versions mount seaplane-style floats and successfully land and take off from water. It is common for the vertical stabilizer to drag on the ground unless it is cut away. This is also why many frames have a small wheel mounted on the back end of the keel. Many light gyroplane rotors are made from aluminum, though GRP-based composite blades (Sport Copter, Averso, Revolution, RAF eg) and GRP-skinned blades are increasing in number. Even aircraft-quality birch was specified in early Bensen designs, and a wood/steel composite is still used in the world speed record holding Wallis.

Flight Controls

There are only three flight controls: a control stick, rudder pedals and a throttle. Modern designs typically use a between-legs control stick instead, and the precession is handled by a mechanical linkage so that left and right stick motions are more intuitive than Bensen's simple design. Another control is a simple set of rudder pedals that move the hinged back half of the vertical stabilizer, similar to a rudder on a fixed wing aircraft. This lets the pilot keep the craft lined up in the desired direction of motion. The stabilizer is mounted behind the pusher propeller, so one can steer the craft on the ground and during takeoff. Some builders use a pushrod between the rudder bar and stabilizer. Others use cables. Some simple autogyros, including Bensen's G-6, do not use controllable-vertical stabilizers at all. They are fixed - this works for towed gyro gliders, but not for powered gyros. The throttle and choke are usually levers mounted where convenient- often under the seat. The rotor generates more lift on the leading side and less on the lagging side, and this causes the rotor to tilt backwards with forward airspeed (helicopters tilt their rotor in the opposite way as they use their rotor to drag the vehicle through the air, whereas an autogyros's blades are unpowered). This increases drag and has a lot to do with the relatively low top speed that Autogyros can reach.

Flight characteristics

Autogyros are often regarded by fixed-wing aircraft pilots as "dangerously unstable", which is certainly true when its pilot is, as is so often the case, self-taught with no professional flight instruction received whatsoever. Piloted properly, a certificated autogyro is significantly safer than any other type of aircraft because it cannot stall, since the rotor of a autogyro is always spinning. If translational airspeed becomes zero, the autogyro will descend vertically to the ground, rotor still spinning. Though safe for the pilot and passengers, landing from a vertical descent usually results in damage to the autogyro. One weakness in certain types of autogyro is pitch instability (pitch is the tilting up or down of the craft as viewed from the front or the back). Pitch instability can be a problem because autogyros lose rotor control authority in negative-G forces (positive-G forces push people into their seats; negative-G forces make people float out of them, such as driving over a hump back bridge at high speed in an automobile). Negative-G forces "unload the rotor" and rotor control authority is lost. A flying autogyro hangs from the rotor much like an object hung from a string. As long as the plane is hanging from the rotor, stability is maintained. The instant zero or negative-Gs are introduced, rotor speed begins to decay and the forces stabilizing the plane are lost. Negative-Gs can be caused by Pilot-Induced Oscillation, or PIO. PIO happens when a pilot adjusts his pitch too much too quickly, then makes a countering control input to bring the pitch back. The countering input often overcompensates, and the autogyro begins to buck like a bronco. You can see a similar effect when some learner-drivers are doing kangaroo-hops in a car with a stick shift and clutch. This is most likely at higher engine throttle settings. If the pilot continues to fight the plane, the rotor (which is flexible) can slow down due to the lack of positive G force, and can flop down and strike the spinning propeller, which destroys both and sends the autogyro into an uncontrolled fall. The way to avoid this during an incipient PIO is to apply gentle back pressure on the stick (to raise the nose in pitch) and cut engine power. Note that this is the exact opposite of what fixed-wing pilots are trained to do when in trouble, which has led to some unfortunate accidents and the autogyro's undeserved reputation for being "dangerous." Another danger is "bunting over" or a Power Push-Over (PPO). An autogyro's vertical airspeed (climb or sink rate) is directly coupled to airspeed. Increase forward airspeed, increase rate of climb. In order to maintain level flight at high engine throttle settings, the pilot must tilt the rotor forward to prevent climbing and maintain level flight. The rotor thus becomes more nearly horizontal, and the control stick becomes more sensitive. Too much forward stick, and the autogyro's rotor can aim down towards the ground. When this happens, negative-Gs occur, rotor speed drops too low to provide lift, and a high-thrustline autogyro is then pitched forward by the propeller thrust and tumbles end-over-end in a somersault. It is virtually impossible to regain control after a full PPO. Two factors can lead to pitch instability: no or too small horizontal stabilizers (h-stabs) on too short a tail and high thrustline propeller placement which destabilises the force diagram. A large h-stab, ideally in the prop wash (where the propeller blows on it) will reduce the tendency of an autogyro to bunt over as a result of improper control input by damping the control response. If the propeller thrustline in an autogyro is high -- meaning the axis of propeller power is above the center of gravity for the aircraft -- the autogyro tends to pitch forward under sudden power application (see PPOs above, as for why this is Bad). (Unfortunately, Bensen-type autogyros have a notably high thrustline.) If the thrustline is low, the autogyro tends to pitch up under sudden power application, which is harmless. It's difficult to have a low thrustline without a really tall autogyro (such as a "Dominator" style) however, so most autogyro designs simply try to get the thrustline as low as possible though still being slightly above the center of gravity. In spite of these dangers, most autogyros are designed to reduce them. Also, the majority of autogyro pilot training involves avoidance of PIO and PPOs. Autogyro rotors usually feature a teeter-hinge in the middle. Picture a autogyro or helicopter from above, rotor spinning clockwise. If the aircraft is flying forward, the rotor tips on the left are traveling faster than the aircraft, while those on the right are actually going backwards relative to the craft. If the rotor blades were fixed, this would produce uneven lift -- more lift on the left side, since those blades are traveling faster. The teeter hinge on each blade lets it "flap" up and down. As the blade swings on the left, the increased speed makes it flap up with a greater angle of attack to the relative wind. This increases drag and reduces lift. As it swings to the right, it's now going slower, relative to forward speed. This reduced drag lets it flap down and get a better bite into the air, increasing lift. Pitch is controlled by a conventional joystick coupled to the rotor. Pulling back on the stick tilts the rotor back, increasing lift and decreasing forward airspeed. Pushing forward on the stick decreases lift and increases airspeed, as long as it is not pushed much beyond horizontal (see PPO above). The plane's direction is controlled by rudder pedals.

Records and Application

As of 2002, Wing Commander Ken Wallis, an enthusiast who has built several gyroplanes, holds or has held most of the type's record performances. These include the speed record of 111.7mph (186km/h), and the straight-line distance record of 543.27 miles (905km). The record picture is continually changing, and on 16 November 2002, Ken Wallis increased the speed record to 207.7 km/h - and simultaneously set another world record as the oldest pilot to set a world record! See: [http://records.fai.org/pilot.asp?from=rotorcraft&id=335] Ken Wallis also built and flew one of the most famous autogyros - "Little Nellie" - in the James Bond movie "You Only Live Twice".
- Hours flown :Autogyros are often used to herd range animals. An autogyro 'cowboy' holds the world record for total hours in the air each week. The Bensen design has also been used by hobbyists, sight-seers and scientists (for game counting).
- Speed :The CarterCopter fixed wing/autogyro hybrid has been unofficially flown in tests at speeds above 170 mph. The claimed theoretical top speed for this general design is in excess of 450 mph. :In the late 1950s, the Fairey Rotodyne, another hybrid was capable of 213 mph. Andy Keech made a TransContinental flight from Kitty Hawk, N.C. to San Diego, Ca. in October 2003 and set 3 World Records. The 3 records are for 'speed over a recognised course', and are verified by tower personnel or by Official Observers of the U.S. National Aeronautic Association:
- Sub-class : E-3a (Autogyros : take-off weight less than 500 kg) :Category : General :Group 1 : piston engine
- Speed over a recognised course : 16.45 km/h, :::Date of flight: 12 October 2003 :::Pilot: Andrew C. KEECH (USA) :::Course/place: Kitty Hawk, NC (USA) - San Diego, CA (USA)
- Speed over a recognised course : 31.89 km/h :::Date of flight: 22 October 2003 :::Pilot: Andrew C. KEECH (USA) :::Course/place: San Diego, CA (USA) - Kitty Hawk, NC (USA)
- Speed over a recognised course, round trip : 16.42 km/h :::Date of flight: 22 October 2003 :::Pilot: Andrew C. KEECH (USA) :::Course/place: Kitty Hawk, NC (USA) - San Diego, CA (USA) and return

Kits

Many autogyros are assembled from kits. Kits with all parts, ready to assemble, are listed for US$19,550 as of 18th July 2002. This is extremely inexpensive for an aircraft. This includes an engine, the major expense. It can be reduced. Some people are clever at scrounging materials. However, scrounging increases one's construction time and program risk. Buying both the engine and rotor hub is recommended by most vendors. Some people who actually completed an autogyro have said that it took them about a year, working in their spare time. Careful estimates place most build times at 100 to 200 hours. Kit vendors often say that since it has relatively few parts, hobbyists can assemble it more rapidly and correctly than most fixed-wing kit aircraft. Kit vendors recommend working on it every day for an hour or two.

Warnings

Most vendors recommend that a new pilot have at least ten hours of instruction by a rated instructor in small fixed-wing aircraft, followed by at least two hours of instruction in a dual-place autogyro with an experienced instructor. An autogyro is more similar to a fixed-wing aircraft than to a helicopter. One must be able to land safely and reliably before attempting to fly any aircraft alone. Autogyros are relatively safe, but not foolproof. There were 19 fatal autogyro accidents reported to the FAA between 1996 and 2001. Autogyros are aircraft. Do not neglect safety precautions: training, instrumentation, flight rules, preflight checklists and periodic inspections and maintenance. In the United States private, recreational, and commercial pilot licenses with rotorcraft category and gyroplane class rating are issued, or the rating is added to an existing license for other aircraft; holders of sport pilot licenses can also qualify to fly autogyros. Requirements include completing required training times, passing written exams, and successfully doing oral and practical tests. Sport pilot license in-flight tests can be conducted in single-seat aircraft, but a "single place only" limitation is placed on the certificate in such cases. "Learning to fly the rotor" is a vital ingredient for safe flight in an autogyro - models and rotary kites can help the learning process, and towed gyro-gliders and boom-trainers are ideal tools for this as well as being cheap to build and fly.

Helicopter

]] , a four seat development of the R22]] A helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors (propellers). Helicopters are classified as rotary-wing aircraft to distinguish them from conventional fixed-wing aircraft. The word helicopter is derived from the Greek words helix (spiral) and pteron (wing). The engine-driven helicopter was invented by the Slovak inventor Jan Bahyl. The first stable, fully-controllable helicopter placed in production was invented by Igor Sikorsky. Compared to conventional fixed-wing aircraft, helicopters are much more complex, more expensive to buy and operate, relatively slow, have shorter range and restricted payload. The compensating advantage is maneuverability: helicopters can hover in place, reverse, and above all take off and land vertically. Subject only to refuelling facilities and load/altitude limitations, a helicopter can travel to any location, and land anywhere with enough space (a diameter of length 1.5 times the rotor disk).

Applications

Helicopters have many uses, both military and civil, including troop transportation, infantry support, firefighting, [http://www.tropicaled.com/helicopter2.htm shipboard operations], business transportation, casualty evacuation (including MEDEVAC, and air/sea/mountain rescue), police and civilian surveillance, carrying goods (some helicopters can carry slung loads, accommodating awkwardly shaped items), or as a mount for still, film or television cameras. Helicopters suffer from significantly higher operating and maintenance costs compared with fixed wing aircraft. The costs are due to inherent mechanical complexity and greater power requirements for a given gross weight. For these reasons, helicopters are not economically viable for commercial transportation. Speed and range limitations also constrain commercial applications.

History

police] Since around 400 BC the Chinese had a flying top that was used as a children's toy. This toy eventually made its way to Europe via trade and has been depicted in a 1463 European painting. Incidentally, the Wright brothers as children were given a rubber-band-powered version of this toy invented by Alphonse Penaud and were very much fascinated by it and built their own copies. "Pao Phu Tau" was a 4th century book in China that described some of the ideas in a rotary wing aircraft. The first somewhat practical idea of a human carrying helicopter was first conceived by Leonardo da Vinci around 1490, but it was not until after the invention of the powered aeroplane in the 20th century that actual models were produced. Developers such as Jan Bahyl, Oszkár Asbóth, Louis Breguet, Paul Cornu, Emile Berliner, Ogneslav Kostovic Stepanovic and Igor Sikorsky pioneered this type of aircraft, with Juan de la Cierva introducing the first practical autogiro in 1923 that was to be the basis for the modern helicopter. A flight of the first fully controllable helicopter was demonstrated by Raúl Pateras de Pescara 1916 in Buenos Aires, Argentina. The German Focke-Wulf Fw 61 was the first practical helicopter. It first flew in 1934. The Bell 47 designed by Arthur Young was the first helicopter to be licensed (in March 1946) for use in the United States. Reliable helicopters capable of stable hover flight were developed decades after fixed wing aircraft. This is largely due to higher engine power density requirements when compared with fixed wing aircraft. Igor Sikorsky is reported to have delayed his own helicopter research until suitable engines were commercially available. Improvements in fuels and engines during the first half of the 20th century were a critical factor in helicopter development. The availability of lightweight turboshaft engines in the second half of the 20th century led to the development of larger, faster, and higher performance helicopters. Turboshaft engines are the preferred powerplant for all but the smallest and least expensive helicopters today.

Generating lift

A conventional aircraft is able to fly because the forward motion of its angled wings forces air downwards, creating an opposite reaction called lift that forces the wings upwards. A helicopter uses exactly the same method, except that instead of moving the entire aircraft, only the wings themselves are moved, in a circular motion. The helicopter's rotor can simply be regarded as rotating wings (hence the military appellation of "rotary wing aircraft"). lift

Conventional layout

There are several possible design layouts for arranging a helicopter's rotors. The most common design is the Sikorsky-layout, which is used by approximately 95% of all helicopters manufactured to date. It is as follows: turning the rotor generates lift but it also applies a reverse torque to the vehicle, which would spin the helicopter fuselage in the opposite direction to the rotor. At low speeds, the most common way to counteract this torque is to have a smaller vertical propeller mounted at the rear of the aircraft called a tail rotor. This rotor creates thrust which is in the opposite direction from the torque generated by the main rotor. When the thrust from the tail rotor is sufficient to cancel out the torque from the main rotor, the helicopter will not rotate around the main rotor shaft. The world's largest and smallest series-produced helicopters follow this principle. The Mil Mi-26 can lift 27 metric tons, the Robinson R22 has a crew of two and a gross weight of 1300 lbs (590 kg). Almost all civilian helicopters have the main rotor and tail rotor system. The world's fastest helicopter, the Westland Lynx can perform aerobatic loops and rolls with this conventional rotor system. aerobatic (Poland)]] Sometimes the blades of a tail rotor are not separated by the same angle, but laid out in an X-shape, which is supposed to reduce the noise levels for military use (e.g. AH-64 Apache). If the tail rotor is shrouded (i.e., a fan embedded in the vertical tail) it is called a fenestron. The fenestron rotor system on the model EC120 helicopter uses a shaft driven system and gearbox to turn the fan. It is less efficient but the advantages are that less noise is generated, it's safer for people that may walk near it and there is less chance of the blades being damaged by objects because it's shrouded, unlike the traditional tail rotor. Other helicopters use a Notar (an acronym meaning no tail rotor) design: they blow air through a long slot along the tail boom, utilizing the Coanda effect to produce forces to counter the torque. Notars adjust thrust by opening and closing a sliding circular cover near the end of the tail boom. The amount of power required to prevent a helicopter from spinning is significant. A tail rotor can use up to 30% of the engine's power, and this power does not help the helicopter produce lift or forward motion. To reduce this waste during cruise, the vertical stabilizer is often angled to produce a force which helps counter the main rotor torque. At high speeds, it is possible for the vertical stabilizer to counteract the entire torque, leaving more power available for forward flight. This is commonly known as slip-streaming and can make hovering turns difficult on windy days. Another reason for the angled vertical stabilizer is to make it possible to stage a successful high-speed, run-on landing, in case of the tail rotor failure or damage. Many military helicopters, especially attack types, have short wings called stub wings to add lift during forward motion. They are also used as external mounts for weapons. In extreme cases, such as that of the Mil Mi-24, the wings are large enough to obstruct airflow down from the rotors, making the helicopter all but unable to hover.

Alternative layouts

Mil Mi-24]] There are alternatives to Sikorsky's layout, which save the weight of a tail boom and rotor. Such designs use two rotors which turn in opposite directions, or contra-rotate. All of these systems are designed for the same purpose: to produce a net rotational speed of zero. These methods introduce even more mechanical complexity to the design and are usually relegated to specialized helicopter types. The co-axial design, where rotors are mounted on top of each other at the top of the fuselage and share a common main axle complex, was first built by Theodore von Karman and Asbóth Oszkár in 1918 and later became the hallmark of soviet Kamov design bureau (see for example the Kamov Ka-50 "Hokum"). Co-axial helicopters in flight are highly resistant to side-winds, which makes them suitable for shipboard use, even without a rope-pulley landing system. Another example is the Kamov Ka-26, a successful crop duster aircraft. The Kaman system of intermeshing rotors, which was developed in Nazi Germany for a small anti-submarine warfare helicopter, features two main rotors on separate, obliquely mounted axles. The contra-rotating rotors are located on top of the fuselage, close to each other. During the Cold War the American Kaman company started to produce similar helicopters for USAF firefighting purposes. Kamans have high stability and powerful lifting capability, thus the latest Kaman V-Max model is a dedicated sky crane design, used for construction works. In the flying-waggon or tandem rotor system (sometimes called "flying banana" for the peculiar shape of early U.S. examples), the two main rotors are located at the front and rear extremity of a long, boxy fuselage that resembles a railway wagon. A prime example is the Boeing CH-47 Chinook, that can carry 14 tons of payload. Waggon helicopters are practical for military logistical purposes, because entry and unloading is easily facilitated via the unobstructed front and rear ramps. The rotors and turbines are located very high on top of the fuselage, making them less sensitive to damage and dirt. The main drawback of a waggon is limited agility in air and the need for a highly trained crew, as the large main rotors have long outreach beyond the fuselage and may easily hit nearby obstacles (in 2001, a South Korean army CH-47 Chinook crashed onto a bridge for that reason while being shown live on TV). A helicopter built by Juan de la Cierva had three main rotors. These were placed at the corners of an equilateral triangle and all turned the same direction. equilateral triangle In the cross system, the rotary wing aircraft resembles a traditional fixed-wing airplane, with the two main rotors mounted at the extremities of its wings. Such helicopters are rare, because structural integrity of the wings is difficult to maintain against the amplified resonance of far off-board rotor-turbine units. The 1930s German FW-61 helicopter was built to such design. The world's largest ever helicopter, the Soviet Mil-V-12 prototype, was a cross of two Mil Mi-6 turbine-rotor units built onto a modified Antonov cargo plane. The U.S. V-22 Osprey tilting rotorcraft is similar, although its nacelles can be rotated, and shares some of the inherent technical problems of a cross system. nacelleA recent development in helicopter technology is the NOTAR system, which stands for NO TAil Rotor. The NOTAR eliminates the tail rotor by conducting high-velocity air through the tail boom. The NOTAR system was developed in the United States and is used exclusively by McDonnel Douglas Helicopters, or MD Helicopters. The most unusual design is the roto-rocket principle, where the single main rotor draws power not from the shaft, but from its own wingtip jet nozzles, which are either pressurized from a fuselage-mounted gas turbine or have their own pulsejet combustion chambers. Although this method is simple and eliminates precession, development of such helicopters ceased soon, because their extreme noise levels preclude both military and civilian use.

Controlling flight

Useful flight requires that an aircraft be controlled in all three dimensions (see flight dynamics). In a fixed-wing aircraft, this is easy: small movable surfaces are adjusted to change the aircraft's shape so that the air rushing past pushes it in the desired direction. In a helicopter, however, there often isn't enough airspeed for this method to be practical. flight dynamics, an aerodynamically restyled F28 for the corporate market.]] For rotation about the vertical axis (yaw) the anti-torque system is used. Varying the pitch of the tail rotor alters the sideways thrust produced. Dual-rotor helicopters have a differential between the two rotor transmissions that can be adjusted by an electric or hydraulic motor to transmit differential torque and thus turn the helicopter. Yaw controls are usually operated with anti-torque pedals, on the floor in the same place as a fixed-wing aircraft's rudder pedals. For pitch (tilting forward and back) or roll (tilting sideways) the angle of attack of the main rotor blades is altered or cycled during the rotation creating a differential of lift at different points of the rotary wing. More lift at the rear of the rotary wing will cause the aircraft to pitch forward, a increase on the left will cause a roll to the right and so on. Helicopters maneuver with three flight controls besides the pedals. The collective pitch control lever controls the collective pitch, or angle of attack, of the helicopter blades altogether, that is, equally throughout the 360 degree plane-of-rotation of the main rotor system. When the angle of attack is increased, the blade produces more lift. The collective control is usually a lever at the pilot's left side, near his leg. Simultanously increasing the collective and adding power with the throttle causes a helicopter to rise. angle of attack] The throttle controls the absolute power produced by the engine that is connected to the rotor by a transmission. The throttle control is a twist grip on the collective control. RPM control is critical to proper operation for several reasons. Helicopter rotors are designed to operate at a specific RPM. If the RPM is too low, rapid descent with power, known as settling with power could result. If the RPM is too high, damage to the main rotor hub from excessive forces could result. In general, RPM must be maintained within a tight tolerance, usually a few percent. In many piston-powered helicopters, the pilot must manage the engine and rotor RPM. The pilot manipulates the throttle to maintain rotor RPM and therefore regulates the effect of drag on the rotor system. Turbine engined helicopters, and some piston helicopters, use servo-feedback loop in their engine controls to maintain rotor RPM and relieves the pilot of routine responsibility for that task. The cyclic changes the pitch of the blades cyclically, causing the lift to vary across the plane of the rotor disk. This variation in lift causes the rotor disk to tilt, and the helicopter to move during hover flight or change attitude in forward flight. The cyclic is similar to a joystick and is usually positioned in front of the pilot. The cyclic controls the angle of the stationary section of the swashplate, which in turn controls the angle of the rotating section of the swashplate. The rotating section rotates with the rotor and is connected to blade pitch horns through pitch links, one link for each blade. When the swashplate is not tilted, the blades are all at the collective angle. When it is tilted, the links give a pitch-up at some azimuthal angle and a pitch-down at the opposite angle, hence creating a sinusoidal variation in blade angle of attack. This causes the helicopter to tilt in the same direction as the cyclic. If the pilot pushes the cyclic forward, then the helicopter tilts forward, and the rotor produces a thrust in the forward direction. angle of attack] As a helicopter moves forward, the rotor blades on one side move at rotor tip speed plus the aircraft speed and is called the advancing blade. As the blade swings to the other side of the helicopter, it moves at rotor tip speed minus aircraft speed and is called the retreating blade. To compensate for the added lift on the advancing blade and the decreased lift on the retreating blade, the angle of attack of the blades is regulated as the blade spins around the helicopter. The angle of attack is increased on the retreating blade to produce more lift, compensating for the slower airspeed over the blade. And the angle of attack is decreased on the advancing blade to produce less lift, compensating for the faster airspeed over the blade. If the angle of attack of any wing, including rotor blades, is too high, the airflow above the wing separates causing instant loss of lift and increase in drag. This condition is called aerodynamic stall. On a helicopter, this can happen in any of three ways. #As helicopter speed increases, the advancing blades approach the speed of sound and generate shock waves that disrupt the airflow over the blade causing loss of lift. #As helicopter speeds increase, the retreating blade experiences lower relative airspeeds and the controls compensate with higher angle of attack. With a low enough relative airspeed and a high enough angle of attack, aerodynamic stall is inevitable. This is called retreating blade stall. #Any low rotor RPM flight condition accompanied by increasing collective pitch application will cause aerodynamic stall. stall AH.1 (XV134), now on the UK Civil Register.]] Helicopters are powered aircraft, but they can still fly without power by using the momentum in the rotors and using downward motion to force air through the rotors. The main rotor acts like a "windmill" and turns. This technique is known as autorotation. A transmission connects the main rotor to the tail rotor so that all flight controls are available after engine failure. Autorotation can allow a pilot to make an emergency landing if the engine failure occurs while the helicopter is traveling high enough or fast enough. (see Height-velocity diagram). A very peculiar feature of the cyclic is that the lift is made to occur 90 degrees of rotation before the direction of tilt. This is because when one tries to tilt a spinning object (like a rotor), it moves at right angles to the direction of the force. This is called "gyroscopic precession". So control forces on the rotor are rotated 90 degrees before the desired motion. For example, forward motion requires less lift at the front of the disk and more lift at the rear of the disk, so the pilot pushes the cyclic forward. The helicopter's control linkages rotate the pitching forces 90 degrees backwards against the rotor spin, to push on the sides of the rotor rather than its front and back. It took inventors many years to recognize precession, and to learn how to arrange the cyclic's control system to overcome it.

Stability

Fixed wing aircraft are designed to be inherently stable. If a gust of wind or a nudge to one of the controls causes a fixed wing aircraft to pitch, roll, or yaw, the aerodynamic design of the aircraft will tend to correct the motion, and the aircraft will return to its original attitude. A small, fixed wing aircraft can be stable enough that a pilot can let go of the controls while looking at a map or dealing with a radio, and the plane will generally stay on course. precession In contrast, helicopters are very unstable. Simply hovering requires continuous, active corrections from the pilot. When a hovering helicopter is nudged in one direction by a gust of wind, it will tend to continue in that direction, and the pilot must adjust the cyclic to correct the motion. Hovering a helicopter has been compared to balancing yourself while standing on a large beach ball. Adjusting one flight control on a helicopter almost always has an effect that requires an adjustment of the other controls. Moving the cyclic forward causes the helicopter to move forward, but will also cause a reduction in lift, which will require extra collective for more lift. Increasing collective will reduce rotor RPM, requiring an increase in throttle to maintain constant rotor RPM. Changing collective will also cause a change in torque, which will require the pilot to adjust the foot pedals. Small helicopters can be so unstable that it may be impossible for the pilot to ever let go of the cyclic while in flight. While fixed-wing aircraft are generally designed so pilots sit on the left side of the aircraft, freeing up their right hand for dealing with radios, engine controls, and the like, helicopters are generally designed so pilots sit on the right side of the aircraft so they can keep their right hand (usually the strong hand) on the cyclic at all times, leaving the radios and engine controls for their left hand (usually the weaker hand).

Limitations

precession The single most obvious limitation of the helicopter is its slow speed. The current record is around 400 km/h set by the Westland Lynx. There are several reasons why a helicopter cannot fly as fast as a fixed wing aircraft.
- When the helicopter is at rest, the outer tips of the rotor travel at a speed determined by the length of the blade and the RPM. In a moving helicopter, however, the speed of the blades relative to the air depends on the speed of the helicopter as well as on their rotational velocity. The airspeed of the forward-going rotor blade is much higher than that of the helicopter itself. It is possible for this blade to exceed the speed of sound, and thus produce vastly increased drag and vibration. It is theoretically possible to have spiralling rotors, similar in principle to variable-pitch swept wings, which could exceed the speed of sound, but no presently known materials are light enough, strong enough, and flexible enough to construct them.
- Most rotors are not rigid. Because the advancing blade has higher airspeed than the retreating blade, a perfectly rigid blade would generate more lift on that side and tip the aircraft over. In consequence, rotor blades are designed to "flap" - lift and twist in such a way that the advancing blade flaps up and develops a smaller angle of attack, thus producing less lift than a rigid blade would. Conversely, the retreating blade flaps down, develops a higher angle of attack, and generates more lift. At high speeds, the force on the rotors is such that they "flap" excessively and the retreating blade can reach too high an angle and stall. In some designs the hub is rigid. The blades are made from composites which can bend without breaking. Fully rigid rotors exist and create very responsive helicopters. In most such designs, the lift is varied cyclically and according to the speed of the helicopter. The adjustment is either by adjusting the angle of attack of the blades, or by engine-powered vacuum devices that suck air into the blades, adjusting the lift. speed of sound) twin rotor helicopter had a large cargo door and external hoist, and was used as personnel/paratroop transport, casualty evacuation, and for lifting large loads. The Belvedere had a production run of only 26 and went into RAF service in 1961.]]
- Rotorhead design is a limiting factor on many helicopters. Low or negative-G situations encountered in a semi-rigid system will result in blade flapping down until it hits the tail boom or other airframe structure, followed by rotor separation, causing a crash.
- Helicopters are susceptible to potentially disastrous vortex ring effects. In these, the downward wind from the rotor causes a circular vortex to form around the rotor. If this ring is augmented by terrain, wind, rain, or sea spray, the helicopter can lose enough lift to experience settling with power and hit the ground. During the closing years of the 20th century designers began working on helicopter noise reduction. Urban communities have often expressed great dislike of noisy aircraft, and police and passenger helicopters can be unpopular. The redesigns followed the closure of some city heliports and government action to constrain flight paths in national parks and other places of natural beauty. Helicopters vibrate. An unadjusted helicopter can easily vibrate so much that it will shake itself apart. To reduce vibration, all helicopters have rotor adjustments for height and pitch. Most also have vibration dampers for height and pitch. Some also use mechanical feedback systems to sense and counter vibration. Usually the feedback system uses a mass as a "stable reference" and a linkage from the mass operates a flap to adjust the rotor's angle of attack to counter the vibration. Adjustment is difficult in part because measurement of the vibration is hard. The most common adjustment measurement system is to use a stroboscopic flash lamp, and observe painted markings or coloured reflectors on the underside of the rotor blades. The traditional low-tech system is to mount coloured chalk on the rotor tips, and see how they mark a linen sheet.

Landing

On a ship

angle of attack] A helo deck is a helicopter pad on the deck of a ship, usually located on the stern and always clear of obstacles that would prove hazardous to a helicopter landing. In the U.S. Navy it is commonly and properly referred to as the flight deck. In the Royal Navy, landing on is usually achieved by lining up slightly astern and on the port quarter, as the ship steams into the wind and the aircraft captain slides across and over the deck. Shipboard landing for some helicopters is assisted though use of a haul-down device that involves attachment of a cable to a probe on the bottom of the aircraft prior to landing. Tension is maintained on the cable as the helicopter descends which assists the pilot with accurate positioning of the aircraft on the deck; once on deck locking beams close on the probe, locking the aircraft to the flight deck. This device was pioneered by the Royal Canadian Navy and was called "Beartrap". The U.S. Navy implementation of this device, based on Beartrap, is called the "RAST" system (for Recovery Assist, Secure and Traverse) and is an integral part of the LAMPS MK III (SH-60B) weapons system.

Hazards of helicopter flight

As with any moving vehicle, operation outside of safe regimes could result in loss of control, structural damage, or fatality. For helicopters the hazards are particularly acute since they are flying at relatively low altitude, with little time to react to a sudden event. The following is a list of some of the potential hazards:
- Retreating blade stall
- Settling with power
- Ground resonance
- Low-G condition
- Operating within the shaded area of the height-velocity diagram
- Vortex ring state, a problem the V-22 Osprey was associated with Each of these conditions is potentially fatal and recovery might not be possible. For this reason, good pilotage demands operation within safe flight regimes and avoiding hazardous conditions at all costs.

Helicopter models and identification

V-22 Osprey In identifying conventional helicopters during flight it is helpful to know that when viewed from below, the rotor of a French, Russian, Soviet or Ukrainian designed helicopter rotates counter-clockwise, whilst that of a helicopter built in Italy, the UK or the USA rotates clockwise (see list of helicopter models). Some companies, notably Schweizer in the USA, are developing remotely-controlled variants of light helicopters for use in future battlefields. [http://rotomotion.com/ Rotomotion] is currently selling a line of small (less than 50 kg) rotorcraft UAVs, including an all electric helicopter. Hybrid types that combine features of helicopters and fixed wing designs include the experimental Fairey Rotodyne of the 1950s and the Bell Boeing Osprey, which is on order by the U.S. Marine Corps and will be the first mass produced tilt-rotor aircraft to enter service. A helicopter should not be mistaken for an autogyro, which is a historical predecessor of the helicopter that gains lift from an unpowered rotor. Some common nicknames for helicopters are "copter", "chopper", "whirlybird", "windmill", "helo" (common U.S. Navy usage) or "paraffin budgie" (the latter term being mostly used in the UK offshore oil industry).

External links

- : "Aircraft, especially aircraft of the direct lift amphibian type and means of construction and operating the same"
- [http://www.helis.com/ Helicopter history]
- [http://centennialofflight.com/history/helicopter.html Helicopter history]
- [http://www.aerospaceweb.org/design/helicopter/history.shtml Image of a Chinese flying top]
- [http://www.centennialofflight.gov/essay/Rotary/early_20th_century/HE2.htm Helicopter development in the early 20th century]
- [http://www.centennialofflight.gov/essay/Dictionary/helicopter/DI27.htm Description of a helicopter]
- [http://www.heli-szene.de/ Helicopter pictures and videos (in German)]
- [http://www.mh-53pavelow.com/ Sikorsky MH-53J/M PAVE LOW helicopter]

References

- Thicknesse P, Jones A et al, Military Rotorcraft, 2nd edition, 2000, Brassey's World Military Technology series, Shirvenham UK, xvi + 160pp, ISBN 1857533259
- Wragg D, Helicopters at War: A pictorial history, 1983, Robert Hale Ltd, London UK, 283pp, ISBN 0709008589
- ko:헬리콥터 ja:ヘリコプター nb:Helikopter

Juan de la Cierva

Juan de la Cierva (21 September 1895--19 December 1936) was a Spanish aeronautical engineer and pilot. His most famous accomplishment was the invention in 1923 of the Autogiro, the predecessor to the helicopter. He was born in Murcia, Spain, and moved to England in 1925 where with the support of Scottish industrialist James G. Weir, established the Cierva Autogiro Company. The Autogiro used a tractor-mounted propeller and engine, a rotor mounted on a mast, and an airplane-type tail assembly. His first three designs -- the C.1, C.2, and C.3 were unstable; the fourth design, the C.4, was successful. The C.8L Mk.II Autogiro made the first flight across the English Channel by a rotary-winged airplane on 18 September 1928. During the Spanish Civil War, he supported Francisco Franco's side. He died in a fixed-wing airplane accident near London, England, at the age of 41. Many say that if he had not died so young, he would have invented the helicopter, because his creation the Autogiro is the direct predecessor of the helicopter.

External links

- [http://www.centennialofflight.gov/essay/Dictionary/cierva/DI17.htm U.S. Centennial of Flight - Juan de la Cierva] Cierva, Juan de la La Cierva, Juan de La Cierva, Juan de La Cierva, Juan de La Cierva, Juan de Cierva, Juan de la

Amelia Earhart

Amelia Mary Earhart (born 24 July, 1897, Atchison, Kansas - missing from 2 July 1937, western Pacific ocean), daughter of Edwin and Amy Earhart, was an American aviator and noted early female pilot who mysteriously disappeared over the Pacific Ocean during a circumnavigational flight in 1937.

Early life

Amelia's grandfather was Alfred Otis, a former federal judge and a leading citizen in Atchison who reportedly was not satisfied with her father Edwin's own success as a lawyer, which is said to have contributed to the break up of her family. Some biographers have speculated that this history of disapproval and doubt followed Amelia throughout her childhood as a tomboy and into her adult flying career. As a girl she is said to have spent long hours playing with her little sister Muriel (Pidge) along with climbing trees, “belly-slamming” her sled downhill and hunting rats with a rifle. At the age of ten (1907) in Des Moines, Iowa Amelia saw an airplane at the Iowa State Fair. She later described it as “...a thing of rusty wire and wood and not at all interesting.” Amelia was twelve when her father Edwin, by then a railroad executive, was promoted and the family's finances improved. However it soon became apparent Edwin was an alcoholic. Five years later, in 1914, he was fired from The Rock Island Railroad. Amy Earhart took Amelia and Muriel to Chicago where they lived with friends. She sent the girls to private schools using money from a trust fund set up by her grandfather Alfred. Amelia graduated from Hyde Park High School in 1915, then went to Canada where she visited her sister at school. She received training as a nurse's aide and in November 1918 began work at Spadina Military Hospital in Toronto, Ontario. By 1919 Earhart had enrolled at Columbia University to study pre-med but quit a year later to be with her parents who had gotten together again in California. Later in Long Beach she and her father went to a stunt-flying exhibition and the next day she went on a ten minute flight. Earhart had her first flying lesson at Kinner Field near Long Beach. Her teacher was Anita “Neta” Snook, a pioneer female aviator. Six months later Earhart purchased a yellow Kinner Airster biplane which she named "Canary." On 22 October 1922 she flew it to an altitude of 14,000 feet, setting a women's world record. On 15 May 1923 Earhart was the sixteenth woman to be issued a pilot's license by the Federation Aeronautique Internationale (FAI).

Aviation career and marriage to GP

High-altitude fliers made little money. Earhart sold Canary and bought a yellow Kissel roadster which she named "the Yellow Peril." Her parents divorced in 1924 and she drove her mother across the United States in the Yellow Peril to Boston, Massachusetts where in 1925 she took employment as a social worker. Earhart also became a member of the National Aeronautic Association's Boston chapter, through which she invested a small sum of money into airport construction and the sale of Kinner airplanes in the Boston area. She also wrote local newspaper columns on flying and as her local celebrity grew she helped market Kinner airplanes, promote flying and encourage women pilots. According to the Boston Globe she was “one of the best women pilots in the United States,” although this characterization has been somewhat disputed by aviation experts and experienced pilots in the decades since. After Charles Lindbergh's solo flight across the Atlantic in 1927, Amy Guest, a wealthy American living in London, UK, expressed interest in being the first woman to fly (or be flown) across the Atlantic Ocean. After deciding the trip was too dangerous to make herself, she offered to sponsor the project anyway, suggesting they find "another girl with the right image." While at work one afternoon in April 1928 Earhart got a phone call from a man who asked her, "Would you like to fly the Atlantic?" She interviewed with the project coordinators who included book publisher and publicist George P. Putnam and was asked to join pilot Wilmer Stultz and co-pilot/mechanic Louis Gordon on the flight, nominally as a passenger. The team left Trepassey Harbor, Newfoundland in a Fokker F7 on 17 June 1928 and arrived at Burry Port, Wales, United Kingdom approximately 21 hours later. She piloted the plane for part of the journey and wrote in the flight log, "If anyone finds that wreck, know that the non-success was caused by my getting lost in a storm for an hour." When the crew returned to the States they were greeted with a ticker-tape parade in New York and a reception by President Calvin Coolidge at the White House. Because of her physical resemblance to Lindbergh, whom the press had dubbed "Lucky Lindy", the American public began referring to Amelia as "Lady Lindy". Earhart later placed third at the Cleveland Women's Air Derby (nicknamed the "Powder Puff Derby" by Will Rogers). For a while she was engaged to Samuel Chapman, an attorney from Boston. Meanwhile Putnam took the chance of heavily promoting Earhart, which included publishing a book she authored, lecture tours and using pictures of her in mass market endorsements for products including luggage, cigarettes (she didn't smoke), pajamas and women's sportswear. The extensive time they spent together led to intimacy and after substantial hesitation on her part they were married on 7 February 1931. Earhart referred to the marriage as a "partnership" with "dual control", and appears to have requested an open marriage; in a recently-discovered premarital letter to Putnam, she wrote that "I want you to understand I shall not hold you to any midaevil [sic] code of faithfulness to me nor shall I consider myself bound to you similarly."[http://ncbuy.com/news/wireless_news.html?qdate=2003-02-25&nav=VIEW&id=0823D7UCP05030225],[http://news.uns.purdue.edu/html4ever/030224.Mobley.Earhart.html]. Later in 1931 she set a world altitude record of 18,415 feet (5613 m) in a Pitcairn PCA-2 autogyro. On the morning of 20 May 1932, at the age of thirty-four, Earhart took off from Saint John, New Brunswick with the latest (dated) copy of a local newspaper. She stopped off in Harbour Grace, Newfoundland in her single engine Lockheed Vega, intending to fly to Paris and duplicate Charles Lindbergh's solo flight. However strong north winds, icy conditions and mechanical problems forced her to land in a pasture near Londonderry, Northern Ireland, United Kingdom. As the first woman to fly solo non-stop across the Atlantic she received the Distinguished Flying Cross from Congress, the Cross of Knight of the Legion of Honor from the French Government, and the Gold Medal of the National Geographic Society from President Herbert Hoover. On 11 January 1935 Earhart became the first person to fly solo from Honolulu, Hawaii to Oakland, California. Later that year she soloed from Los Angeles to Mexico City and back to Newark, New Jersey. She held several transcontinental speed records. Earhart joined the faculty of Purdue University in 1935 as counselor on careers for women, exploring new fields for young women to enter after graduation.

World Flight, 1937

In July 1936 she took delivery of a Lockheed 10E Electra financed by Purdue University and started planning a round-the-world flight. This would not be the first to circle the globe, but would be the longest at 29,000 miles (47,000 km) since it would follow a grueling equatorial route. Although the Electra was publicized as a "flying laboratory" little useful science was planned and the flight seems to have been arranged around Earhart's goal to circumnavigate the earth along with providing raw material and public attention for her next book. Through contacts in the Los Angeles aviation community Fred Noonan was eventually chosen as navigator. He had vast experience in both marine (he was a licensed ship's captain) and flight navigation. Noonan had recently left Pan Am, where he established most of the company's seaplane routes across the Pacific. He hoped the resulting publicity would help him establish his own navigation school in Florida. On 17 March 1937 they flew the first leg, Oakland, California to Honolulu, Hawaii. The flight resumed three days later but a tire blew on takeoff and Earhart ground-looped the plane. Severely damaged, the aircraft had to be shipped to California for repairs and the flight was called off. The second attempt would begin at Miami, this time flying east. They departed on 1 June and after numerous stops in South America, Africa, the Indian subcontinent and Southeast Asia they arrived at Lae, New Guinea on June 29. About 22,000 miles (35,000 km) of the journey had been completed and the remaining 7,000 miles (11,000 km) would all be over the Pacific. June 29 On 2 July 1937 at midnight GMT Earhart and Noonan took off from Lae. Their intended destination was Howland Island, a flat sliver of land 2000 meters long and 500 meters wide, 10 feet (3 m) high and 2556 miles (4113 km) away. Their last positive position report and sighting were over the Nukumanu Islands, about 800 miles (1,300 km) into the flight. The U.S. Coast Guard cutter Itasca was on station at Howland, assigned to communicate with Earhart's Lockheed Electra 10E and guide her to the island once she arrived in the vicinity. Through a series of misunderstandings or errors (the details of which are still controversial), the final approach to Howland using radio navigation was never accomplished, although vocal transmissions by Earhart indicated she and Noonan believed they had reached Howland's charted position, which was incorrect by about five nautical miles (9 km), over scattered clouds which are said to have cast hundreds of island-like shadows on the ocean. After several hours of frustrating attempts at two-way communications, contact was lost, although subsequent transmissions from the downed Electra may have been received by operators across the Pacific. The United States government spent $4 million looking for Earhart. The air and sea search by the Navy and Coast Guard was the most costly and intensive in history at that time, but search and rescue techniques during that era were rudimentary and planning was influenced by individuals wary about how their roles in looking for an American hero might be reported by the press. Many researchers believe the plane ran out of fuel and Earhart and Noonan ditched at sea. However, one group (TIGHAR - The International Group for Historic Aircraft Recovery) suggests they may have flown for two and a half hours along a standard line of position, which Earhart specified in her last transmission received at Howland, to Nikumaroro Gardner Island (now Nikumaroro, Kiribati), landed there, and ultimately perished. TIGHAR's research has produced a range of documented, archaeological and anecdotal evidence (but no proof) supporting this theory.

Legacy

Amelia Earhart was a widely-known celebrity during her lifetime. Her shyly charismatic appeal, independence, persistence, coolness under pressure, courage and goal-oriented career along with the mysterious circumstances of her disappearance have driven her lasting fame in popular culture. Hundreds of books have been written about her life, which is often cited as a motivational tale, especially for girls. Earhart is generally regarded as a feminist icon who blazed a trail of achievement for generations of women who came after her.

Books by Earhart

Kiribati Amelia Earhart was an accomplished and articulate writer who served as aviation editor for Cosmopolitan magazine from 1928 to 1930. She authored numerous magazine articles and essays, and published two books based upon her experiences as a flyer during her lifetime:
- 20 Hrs., 40 Min. was her journal of her 1928 flight across the Atlantic as a passenger (making her the first woman to make such a journey).
- The Fun of It was a memoir of her flying experiences, as well as an essay on women in aviation. A third book credited to Earhart, Last Flight, was published following her disappearance and featured journal entries she made in the weeks prior to her final departure from New Guinea. Compiled by Putnam himself, historians have cast doubt upon how much of the book was actually Earhart's original work and how much had been embellished by Putnam.

Fiction by other authors

The romantic, tragic and mysterious story of Amelia Earhart has spurred the imaginations of many writers. Stories featuring her have ranged from straightforward biographies to true flights of fantasy. For example:
- I Was Amelia Earhart is a faux autobiography by Jane Mendelsohn in which "Earhart" tells the story of what happened to her in 1937, complete with heavy doses of romance with her co-pilot.
- Flying Blind by Max Allan Collins is a detective novel in which the intrepid Nathan Heller is hired to be a bodyguard for Amelia Earhart. Before long they become lovers, and later Heller helps her to try to escape from the Japanese following her ill-fated flight.
- The Star Trek: Voyager episode, "The 37s", suggests that Earhart and Noonan were kidnapped by aliens in 1937 and taken to the Delta Quadrant, where they were found by Captain Kathryn Janeway but chose to remain on the far side of the galaxy instead of returning to Earth. (Star Trek also established that one of Starfleet's main space stations is named after Earhart.)
- The 1943 Rosalind Russell film Flight for Freedom was a fictionalized treatment of Earhart's life, with a heavy dose of Hollywood World War II propaganda.
- In an episode of the TV sitcom Friends, Ross suggested that if he were to win the lottery, he intended to make a dinosaur/Amelia Earhart theme park.
- Heather Nova recorded a song named I Miss My Sky (Amelia Earhart's Last Days), located on her album Redbird (2005).
- A 1976 television bio project titled Amelia Earhart included flying by Hollywood stunt pilot Frank Tallman whose late partner in Tallmantz Aviation, Paul Mantz, had tutored Earhart in the 1930s.
- In the TV adaptation of Dilbert, Amelia Earhart is trapped in a museum exhibition where there are buttons which serves to torment her and to simulate a fictional storm which brought her plane down.

Urban legends

During the decades since her disappearance many rumours and urban legends have circulated (and often been published) about what might have happened to Earhart and Noonan. Some have claimed Earhart was captured in the South Pacific Mandate area by the Japanese and interned for a number of years before either perishing or being executed. This originated when a man, then 15, claimed he had been toying with his radio and a woman came upon the speaker, claiming to be Amelia Earhart. There was then a scream and the woman said Japanese soldiers had entered the plane, she begging them not to hurt her. Then the transmission went dead. Purported photographs of Earhart during her captivity have been identified as having been taken before her final flight. A fictional World War II era movie called Flight for Freedom starring Rosalind Russell and Fred MacMurray is often cited as the most likely source of a popular myth Earhart was a spy. Some researchers have noted the possibility that for wartime propaganda purposes, the US government may have tacitly encouraged (or was indifferent to) false rumours Earhart had been captured by the Japanese. An archaeological dig on Tinian in 2004 failed to turn up any bones at a location rumoured since the close of World War II to be the aviators' grave. Perhaps the strangest rumour was that Earhart had been forced to make propaganda radio broadcasts as one of the many women known as Tokyo Rose (according to several biographies of Earhart, George Putnam investigated this rumor personally, but after listening to recordings of numerous Tokyo Roses, was unable to recognize her voice among them). Others have suggested Earhart later managed to return to America where she changed her name and lived out her life quietly, while still others blame her disappearance on Unidentified Flying Objects. There is no evidence to support any of these suggestions, which have all been dismissed by serious historians. (The aforementioned Star Trek episode was based upon the UFO myth.)

Bibliography

- Briand, Paul, Daughter of the Sky. New York: Duell, Sloan, Pearce, 1960.
- Butler, Susan, East to the Dawn: The Life of Amelia Earhart. Reading MA: Addison-Wesley, 1997.
- Devine, Thomas E., Eyewitness: The Amelia Earhart Incident. Frederick, CO: Renaissance House, 1987.
- Goerner, Fred, The Search for Amelia Earhart. New York: Doubleday, 1966.
- King, Thomas F.; Jacobson, Randall; Spading, Kenton; Burns, Karen Ramey; Amelia Earhart's Shoes. Lanham, MD: AltaMira Press, 2001. ISBN: 0759101302
- Long, Elgen M., Amelia Earhart: The Mystery Solved. New York: Simon & Schuster, 1999.
- Loomis, Vincent V., Amelia Earhart, the Final Story. New York: Random House, 1985.
- Lovell, Mary S., The Sound of Wings. New York: St. Martin's Press, 1989.
- Rich, Doris L., Amelia Earhart: A Biography. Washington DC: Smithsonian Institution Press, 1989.
- Strippel, Dick., Amelia Earhart - The Myth and the Reality. New York: Exposition Press, 1972.

External links

- [http://www.tighar.org/Projects/Earhart/AEdescr.html The Earhart Project] from The International Group for Historic Aircraft Recovery. Includes a summary of the Nikumaroro landing hypothesis and a video showing Earhart's Lockheed taking off from Lae
- [http://www.lib.purdue.edu/spcol/aearhart/ Amelia Earhart Collection of Papers, Memorabilia and Artifacts] Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia Earhart, Amelia ja:アメリア・イアハート

Stall

where sponges are sold]] Stall can refer to:
- a semi-permanent place for conducting sales.
- the living quarters for an animal in a barn or stable.
- a high-backed booth at a restaurant.
- any small compartment (such as a shower stall or restroom stall).
- In a theatre or concert hall auditorium, the stalls are the seats on the ground floor directly in front of the stage.
- A phenomenon whereby an engine abruptly ceases operating and stops turning (perhaps due to fuel starvation or a mechanical failure), or in response to a sudden increase in engine load.
- The loss of lift in an aircraft when the critical angle of attack is exceeded results in a stall (flight).
- An instruction pipeline of a modern CPU may stall when execution cannot continue because previous events that the current instruction is dependent on has not yet completed.

Ken Wallis

Wing Commander K H Wallis MBE, DEng (hc), CEng, FRAeS, FSETP, PhD (hc), RAF (Ret'd) to give him his full title, is one of the leading exponents of autogyros. He has held (in some cases still holds) 34 records relating to them. He produces autogyros for in his own words "reconnaissance, research & development, surveillance and military purposes" and his designs are not available for enthusiasts. Born on 16th April, 1916, he developed a practical interest in mechanics, building a motorcycle at the age of 11. In the 1930s he bought and assembled a Flying Flea aircraft. These were kit form midget aircraft which were banned in 1936 after several fatalities due to design flaws. His military career started with Westland Lysander patrols in the RAF. In 1942 he was transferred to Bomber Command, flying Wellingtons near Grimsby. He subsequently served in Italy. Thereafter he was involved in research and development. He left the RAF in 1964 retiring to Norfolk. He took an interest in powerboating which he kept up until 1957, when he won the 56-mile long Missouri Marathon. He receieved the MBE in 1996 He provided and flew Little Nellies in the James Bond film You Only Live Twice. He is President of the Norfolk & Suffolk Aviation Museum. Wallis, Ken Wallis, Ken

2002

2002 (MMII) is a common year starting on Tuesday of the Gregorian calendar. It was designated the:
- International Year of Ecotourism and Mountains
- Year of the Outback in Australia
- National Science Year in the United Kingdom
- Autism Awareness Year in the United Kingdom See also Wikipedia's almanac of events for this year.

Overview of the year

In contrast to 2000 and 2001, which retained elements of the late 1990s, 2002 shifted into a new cultural decade. With the declining popularity of late 1990s and early 2000s acts like 'N Sync and The Backstreet Boys after band break-ups, rap acts like 50 Cent and Eminem rose in popularity. Pop-Punk acts like Good Charlotte and New Found Glory also appealed to adolescents. 2002 also marked the begining of the controversial Iraq War, which many say, along with 9/11, was the true generation definer of the 2000s.

Events

January

- January 1 - The Republic of China officially joins the World Trade Organization, as Chinese Taipei.
- January 1 - The Open Skies mutual surveillance treaty, initially signed in 1992, officially enters in to force.
- January 5 - Charles Bishop, a 15 year-old student pilot, crashes a light aircraft into a Tampa, Florida building, evoking fear of a copycat 9/11 terrorist attack.
- January 9 - The United States Department of Justice announces it is going to pursue a criminal investigation of Enron.
- January 10 - Enrique Bolaños began his five-year term as President of the Republic of Nicaragua.
- January 13 - President George W. Bush faints after choking on a pretzel.
- January 14 - The case of Adelaide Abankwah comes into trial in New York
- January 16 - A student shoots 6 people at the Appalachian School of Law, killing three.
- January 16 - John Ashcroft announces that American Taliban member John Walker Lindh would be tried in the United States.
- January 16 - The UN Security Council unanimously establishes an arms embargo and the freezing of assets of Osama bin Laden, Al-Qaida, and the Taliban.
- January 17 - Eruption of Mount Nyiragongo in the Democratic Republic of the Congo, displacing an estimated 400,000 people.
- January 18 - A Canadian Pacific Railway train carrying anhydrous ammonia derails outside of Minot, North Dakota, killing one.
- January 22 - AOL Time Warner brings a federal suit against Microsoft seeking damages. The suit alleges that the market for AOL's Netscape Navigator Internet browser was harmed when Microsoft started to give away a competing browser.
- January 22 - Kmart Corp becomes the largest retailer in American history to file for Chapter 11 bankruptcy protection.
- January 22 - Clyde Hood sentenced for 14 years in prison for Omega Trust fraud
- January 24 - Terrorist suspect John Walker Lindh's hearing begins.
- January 27 - Several explosions at a military dump in Lagos, Nigeria kill more than 1,000.

February

- February 2 - Crown Prince Willem-Alexander of the Netherlands marries Máxima, Princess of Orange in Amsterdam.
- February 3 - Costa Rica: elections for President and Congress
- February 8-February 24 - 2002 Winter Olympics in Salt Lake City, Utah
- February 12 - The trial of former President of the Federal Republic of Yugoslavia Slobodan Milošević begins at the United Nations war crimes tribunal in The Hague
- February 12 - Nuclear waste: US Secretary of Energy makes the decision that Yucca Mountain is suitable to be the United States' nuclear repository.
- February 13 - Queen Elizabeth II gives former New York City mayor Rudolph Giuliani an honorary knighthood.
- February 16 - Rachel Thaler, aged 16, blown up at a pizzena in an Israeli shopping mall following a suicide bombing attack on a crowd of teenagers.
- February 19 - NASA's Mars Odyssey space probe begins to map the surface of using its thermal emission imaging system.
- February 20 - In Reqa Al-Gharbiya, Egypt, a fire on a train injures over 65 and kills at least 370
- February 20 - In most of the world, at 20:02 (8:02 PM) local time, date (written as day/month), time, and year are all 2002, making each of them alone, any two together, and the combination of all three, all palindromes.
- February 22 - Norwegian-facilitated ceasefire begins in Sri Lanka
- February 23 - FARC kidnaps Ingrid Betancourt in Colombia when she campaigns for presidency
- February 27 - Ethnic conflict in India: 59 Hindu pilgrims die aboard a train burned by a Muslim mob in Godhra, India, sparking a series of riots, leaving hundreds dead
- February 28 - The ex-currencies of all euro members officialy (at EU-level) cease to be legal tender.

March

- March 1 - U.S. invasion of Afghanistan: In eastern Afghanistan, Operation Anaconda begins.
- March 1 - 28 people die in continuing violence in Ahmedabad. Police shoot and kill five while attempting to control rioters.
- March 1 - The Envisat environmental satellite successfully reaches an orbit 800km above the Earth on its 11th launch, carrying the heaviest payload to date at 8500kg.
- March 1 - Space Shuttle Columbia flies Hubble Space Telescope service mission (STS-109).
- March 1 - Peseta discontinued as official currency of Spain and is replaced with the euro (€)
- March 3 - São Tomé and Príncipe: elections for the legislature
- March 6 - France agrees to return the remains of Saartje Baartman to South Africa
- March 10 - Colombia: elections for the legislature; Togo: elections for the Parliament
- March 11 - BBC 6 Music, the first new BBC music radio station in decades, is launched
- March 12 - In Texas, Andrea Yates is found guilty of drowning her five children on June 20, 2001. She is later sentenced to life in prison
- March 17 - Portugal: elections for the Parliament
- March 19 - US Attack on Afghanistan: Operation Anaconda ends (started on March 1) after killing 500 Taliban and al Qaeda fighters with 11 allied troop fatalities
- March 21 - In Pakistan, Ahmed Omar Saeed Sheikh along with three other suspects are charged with murder for their part in the kidnapping and killing of Wall Street Journal reporter Daniel Pearl
- March 27 - Netanya suicide attack: A suicide bomber kills 28 people in Netanya, Israel
- March 31 - Ukraine: elections for the Parliament

April

April
- April 2 - Israeli forces surround the Church of the Nativity in Bethlehem, when militants take shelter there. A siege ensues.
- April 9- Funeral of Queen Elizabeth, the Queen Mother takes place in Westminster Abbey, London.
- April 15 - An Air China Boeing 767-200 crashes into a hillside during heavy rain and fog near Pusan, South Korea, killing 128
- April 15 - The Alameda Corridor transportation project in Los Angeles, California opens to rail traffic, ceasing operations of through freight trains on the 120-year-old BNSF Harbor Subdivision.
- April 17 - Four Canadian infantrymen are killed in Afghanistan by friendly fire from two U.S. F-16s.
- April 18 - New order of insects, Mantophasmatodea, announced.
- April 25 - South African Mark Shuttleworth blasts off from the Baikonur cosmodrome; he had paid £15 million for the trip.
- April 26 - Robert Steinhauser opens fire on his former teachers and other students in Erfurt, Germany and then kills himself: 16 dead.
- April 27 - Three people killed in Laughlin, Nevada River Run Riot.
- April 30 - Pakistan: Pakistani voters approve a referendum granting a five-year term for Pakistani president Pervez Musharraf.

May

May]
- May 4 - In Germany, BV Borussia Dortmund wins the Bundesliga title after a 2-1 victory over SV Werder Bremen.
- May 6 - In the Netherlands, politician Pim Fortuyn is killed by Volkert van der Graaf.
- May 7 - Gay Canadian teenager Marc Hall is granted a court injunction ordering that he be allowed to attend his high school prom with his boyfriend.
- May 9 - The 38-day stand-off in the Church of the Nativity in Bethlehem comes to an end when the Palestinians inside agreed to have 13 suspected militants among them deported to several different countries. The standoff started April 2.
- May 9 - In Kaspiysk, Russia, a remote-control bomb explodes during a holiday parade, killing 43 and injuring at least 130.
- May 10 - FBI agent Robert Hanssen is sentenced to life without the possibility of parole for selling American secrets to Moscow for $1.4 million in cash and diamonds.
- May 12 - Former President Jimmy Carter arrives in Cuba for a five-day visit with Fidel Castro becoming the first President of the United States, in or out of office, to visit the island since Castro's 1959 revolution.
- May 15 - The Netherlands: elections for the Lower House.
- May 16 - Star Wars: Attack of the Clones is released in theaters.
- May 20 - Restoration of East Timor independence
- May 21 - US State Department releases report citing seven State-Sponsors of Terrorism;Iran,Iraq,Cuba,Libya,North Korea,Sudan,andSyria.
- May 22 - In Washington, DC, Chandra Levy's remains are found in Rock Creek Park.
- May 22 - American civil rights movement: 16th Street Baptist Church bombing: A jury in Birmingham, Alabama convicts former Ku Klux Klan member Bobby Frank Cherry of the 1963 murders of four girls.
- May 23 - Irish Football Captain, Roy Keane, Is sent home from the Training Camp in Saipan, by Manager Mick McCarthy after an Argument over Training arrangements. This cause a huge Media sensation in Ireland and Britain. Many people were split over two sides and some called it the Second Irish Civil War.
- May 23 - First Eurovision Song Contest in a former Soviet country: Estonia
- May 25 - The Boston Celtics come back from twenty-six points down to defeat the New Jersey Nets in Game 3 of the National Basketball Association's Eastern Conference Finals.
- May 25 - China Airlines Flight 611 broke up near the Penghu Islands at Taiwan Strait, killing all 225 people on board.
- May 26 - The Mars Odyssey finds signs of huge water ice deposits on the planet Mars.
- May 28 - Washington DC's medical examiner declares that Chandra Levy's death was the result of homicide.
- May 31 through June 30 - 17th Football World Cup in South Korea and Japan

June

June over London in a fly past for Queen Elizabeth II on her Golden Jubilee]]
- June 1 - The Los Angeles Lakers def the Sacramento Kings 112-106, to win Game 7 of the National Basketball Association's 2002 Western Conference Finals.
- June 3 - The "Party in the Palace" takes place at Buckingham Palace, London for Queen Elizabeth II's Golden Jubilee celebrations.
- June 4 - Quaoar is discovered.
- June 4 -