Category FLIGHT and M ОТІOIM

Directional Stability

Directional stability keeps a plane flying in a straight line without veering to one side or the other. Early airplanes had lit­tle stability. The pilot had to concentrate extremely hard and constantly make adjustments to keep the plane under control. A gust of wind or a careless maneuver could send the plane spiraling to the ground. Many early aviators died in crashes caused by poor stability and control problems.

A modern plane’s tail fin, or vertical stabilizer, helps to provide directional stability. If the plane’s nose is pushed to one side by a gust of wind, the airflow around the tail fin moves the tail back in line with the nose, so that the plane keeps flying in the same direction instead of veering off course. (Weather vanes keep pointing into the wind for the same reason.)

Testing and Using SVS

Подпись:
Testing and Using SVSПодпись: The TIFS aircraft is a modified C-131 Samaritan military aircraft, which is itself based on a Convair 580 turboprop airliner. It was built in the 1950s and converted to a flying simulator in the late 1960s. TIFS has two cockpits. One is used to test new developments. The other (standard) cockpit can take over at any point if necessary. This double cockpit is an important feature, because it allows a test pilot safely and repeatedly to push a system all the way to failure, which is risky to do in a conventional flight test, especially near the ground. The research cockpit can be programmed to make the plane fly like other kinds of aircraft. In its test flights, it has doubled for a variety of airliners, experimental aircraft, the B-2 Spirit stealth bomber, and even the Space Shuttle. As well as simulating other aircraft, it also is used to test new avionics systems. In this case, the second cockpit can be replaced by a nose section containing the new avionics, and the research pilot sits at a crew station in the aircraft's cabin. Pilots say it is more realistic to fly TIFS than a simulator on the ground because it sounds, feels, and performs like the real airplane. The TIFS plane entered service as a military transport on March 22, 1955, so it cele-brated its fiftieth anniversary in 2005. к J
In 1999, synthetic vision was tested in flight by a modified C-131 military aircraft named the Total In-Flight Simulator (TIFS). For the tests, TIFS was fitted with screens to try a variety of dif­ferent images and data. The research flights were made out of Asheville Regional Airport in North Carolina.

Подпись: О A pilot testing SVS in 1999 was able to compare the virtual world on his screen with a view from the cockpit.Testing and Using SVSПодпись: — SEE ALSO: Testing and Using SVSResearch pilots using the synthetic vision system reported that they soon forgot they were looking at a computer-generated image and not at the real world.

System designers are already thinking about other ways in which SVS might be used in the future. One possible application is in air traffic control systems at airports.

Airport traffic con­trollers work in a con­trol room that looks out across the airport, but some parts of an airport may be obscured by buildings or bad weather. SVS could provide con­trollers with a clear, computer-generated view of the entire air­port in all conditions. Although synthet­ic vision has been developed for civil aviation, military forces also are interest­ed in the systems. Synthetic vision already has been flight tested in military airplanes and helicopters.

• Air Traffic Control • Avionics

• Cockpit • Global Positioning System • Pilot

Naval Service

The main advantage of a VTOL aircraft is that it does not need a runway, and so it can operate from any small patch of ground, from a road, or even a ship’s deck. One version of the Harrier, the Sea Harrier, was developed for naval use. It could operate from the smallest aircraft carriers. The decks of these ships are too short for most naval jets that require runways, but they are big enough for helicopters and VTOL aircraft.

A Sea Harrier with full fuel tanks and a large weapons load is too heavy to take off vertically, and the deck of a small aircraft carrier is too short to use a normal takeoff run. So small carriers are fitted with a ramp at the end of the deck, also known as a ski jump. As an aircraft accelerates toward the end of the deck, the ski jump gives it an extra push upward into the air.

Подпись: О A Sea Harrier heads for the ski jump during its takeoff from an aircraft carrier.

A Sea Harrier pilot has to calculate the aircraft’s takeoff speed very careful­ly by using its weight and the current wind speed. If takeoff is too slow, the plane might not get airborne. If it is too fast, the Sea Harrier might hit the ski jump too hard and damage its undercar­riage. The Sea Harrier uses a short take­off and vertical landing, making it a STOVL aircraft. It was the first opera­tional STOVL combat aircraft to use vectored thrust.

Подпись:FLYING BEDSTEADS

When NASA was preparing to send astronauts to the Moon in the 1960s, they developed a strange – looking aircraft to prepare astro­nauts for the task of landing on the lunar surface. The lunar lander, called the Apollo Lunar Excursion Module (LEM), would descend to the Moon balanced on the fiery jet of gas from a rocket engine. The first training vehicle for this event balanced on the jet exhaust from a jet engine instead of a rocket. Called the Lunar Landing Research Vehicle, it led to the development of three Lunar Landing Training Vehicles. Astronauts called them "flying bedsteads" because of their strange appearance.

When the U. S. Marines were looking for a light attack plane, they developed the Harrier to suit their needs. Their work resulted in a new Harrier, the AV – 8B Harrier II. It had bigger, thicker wings and was able to carry a bigger payload over a greater distance.

Other Kinds of Wings

Fixed-wing airplanes are not the only aircraft that use wings. A helicopter’s rotor blades are actually long, thin wings. High-performance parachutes called parafoils are really inflatable wings. The parachute is made of two layers of fabric with dividers between them, forming a line of pockets, or cells. As the parachute moves along,
air fills the cells and forms a wing shape. The parachutist con­trols and steers the parafoil by pulling control lines that change the wing’s shape.

A flexible fabric hang glider is yet another type of wing. Called a Rogallo wing, this early hang glider was developed in the 1940s by hus­band and wife, Francis and Gertrude Rogallo. When space exploration began, NASA investigated the Rogallo wing as a way of landing the Gemini manned spacecraft. Round parachutes eventually were used instead, but the Rogallo wing was used by other designers, who devel­oped it into the modern hang glider.

Racecars also use wings. However, racecar wings do the opposite job of air­craft wings. They produce a downward force, called downforce, when they cut through air. This pushes the car down harder against the ground, giving its tires better grip, and enabling it to take corners faster without loss of traction.

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SEE ALSO:

• Aerodynamics • Aileron and

Rudder • Bernoulli’s Principle

• Lift and Drag • Stall

Industrial Production

Prewar theories that bombing would destroy civilian morale and halt factory production proved inaccurate. The British did not crumble during the Blitz; the Russians moved their factories east out of range of German planes; and German and Japanese workers contin-

Подпись: О The U.S. aerospace industry boomed during World War II. Mass production methods became more efficient, and Americans worked around the clock to build aircraft. Industrial Production

Industrial Production

Подпись:WORLD WAR II AVIATION ADVANCES

World War II was a war of air power. During the course of the war, top speeds of fighter aircraft rose from about 350 to 450 miles per hour (563 to 724 kilometers per hour). Bombers flew higher to escape interception: up to 35,000 feet (10,700 meters) by 1945. Naval battles among ships were replaced by long-range air battles between planes flying from aircraft carriers. Factory production methods speeded up manufacture, and technology greatly improved the range, nav­igation, gun power, and bombing accuracy of warplanes. Air transports, such as the C-47 and C-54, carried troops and supplies, and parachutes were used to land them. Radar was the key air invention: It aided ground defenses and also helped pilots locate enemy targets. Air weapons became more destructive as bombs laid waste to cities, and guns and rockets could blow planes apart in midair. For protection, planes had armor plating and self-sealing fuel tanks. By 1944 to 1945, air warfare had been changed forever by new weapons and tech­nology: jet planes, helicopters, the V-1 flying bomb, the V-2 missile, and the atomic bomb.

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SEE ALSO:

• Aircraft, Military • Aircraft Carrier

• Bomber • Fighter Plane • Missile

• Parachute • Radar

Industrial Production

Industrial Production

Traveling in Space

After being launched, a spacecraft leav­ing Earth for the Moon or Mars does not need to keep burning fuel. Spacecraft can make use of other methods of propulsion, such as solar sails or ion engines. Once on course and free of Earth’s gravity pull, the engines can be switched off to save fuel as the space­craft coasts through space. This is how the Apollo astronauts traveled to the Moon, a trip that took two-and-a-half days. They fired their engines only to slow down the spacecraft and during their return to Earth.

Traveling in Space

О The Apollo 10 crew sped home at 24,790 miles per hour (39,890 kilometers per hour) on their return from the Moon in 1969. The astronauts’ capsule splashed down safely in the Pacific Ocean.

Traveling in Space

О Helios A and Helios B were space probes sent in the 1970s to orbit the Sun. They reached the highest speed of any spacecraft. A 1974 photo­graph shows Helios A on top of a launch vehicle.

Although there is no air in space, space is not empty. It contains dust, chunks of minerals, space junk, and streams of radiation flowing out at great speed from the Sun and from other stars.

Stretching into space around Earth is a magnetic field. This magnetism attracts electrically charged particles that form belts, or zones, of radiation. Named the Van Allen radiation belts, these radia­tion zones were unknown until the first U. S. satellite, Explorer 1, encountered them in 1958. The Van Allen belts were the first important scientific discovery made by a spacecraft.

The fastest spacecraft sent from Earth so far have been the solar probes Helios A (1974) and Helios B (1976). Helios B traveled about 150,000 miles per hour (241,350 kilometers per hour) as it orbited the Sun. Although spacecraft are the fastest vehicles ever flown by humans, they are snail-like in space terms, where the distances are unimag­inably immense. The nearest star is 4.2 light years from Earth. So even if a future spacecraft could reach light speed of 186,000 miles per second (299,280 kilometers per second), it would take 4.2 years to get there.

To fly astronauts to Mars and back using existing spacecraft would take eighteen months. Keeping astronauts alive, healthy, and able to work during such a long mission poses great chal­lenges to space science. Humans are not designed for an airless, weightless environment. A manned spacecraft must provide everything needed for human life support-air, water, food, fuel, energy, waste disposal, and exercise. Long periods of spaceflight weaken the body’s muscles. So great are the chal­lenges that some scientists believe that

Space Shuttle

T

he Space Shuttle was the world’s first reusable spacecraft and the first spacecraft with wings. The Space Shuttle can carry seven astronauts into space, stay in orbit for about two weeks, and then fly back to Earth to land on an airstrip.

The Shuttle Concept

Until the first Space Shuttle flew in 1981, all spacecraft (manned craft, satel­lites, and space probes) were launched by multistage rockets. Such rockets and the spacecraft they carried could be used just once. Only the spacecraft itself reached space; the discarded rocket stages fell into the sea or burned up in the atmosphere. The Space Shuttle was planned as a more economical vehicle
that could make regular trips into space. It has no rival. The Soviet Buran shuttle spacecraft, similar in appearance, made only one flight, without a crew, in 1988; it was thereafter canceled.

In 1969, a Space Task Group set up by President Richard Nixon’s adminis­tration suggested several new space projects. One was a reusable spacecraft, capable of flying one hundred or more missions. The result was the Space Shuttle, known to NASA as the Space Transportation System (STS). The main contractor was North American Aviation (later part of Rockwell International, now part of Boeing). Other contractors responsible for supplying the engines

О A view inside the Space Shuttle shows the giant engines, the cargo bay, and the flight deck and mid-deck where the astronauts live.

Space Shuttle

Rudder and speed brake

Main engines (3)

Maneuvering engines (2)

 

Forward

control

thrusters

 

Hydrazine and nitrogen tetroxide tanks

 

Space radiators (inside doors)

 

Manipulator arm

 

Cargo bay

 

Flight

deck

 

Space Shuttle

Space Shuttle

Подпись: Unite'Подпись: Nose Mid-deck gear Air

control

thrusters

Electrical system fuel cells

Body flap Elevon

 

Main gear

 

Space Shuttle

and fuel tanks, were Morton Thiokol, Martin Marietta, and Rocketdyne.

The first Shuttle to fly was Enterprise, which was used for prelimi­nary flight and landing tests from 1977. These tests included flights on top of a modified Boeing 747 airplane. Enterprise never actually went into space. Five Space Shuttles have flown in orbit. The first operational Space Shuttle, delivered to NASA in March 1979, was Columbia, which made its first space flight on April 12, 1981, and remained in service until it was destroyed in a tragic accident in 2003. Challenger, which arrived at Kennedy Space Center in July 1982, was the first Space Shuttle to be lost in an accident, in January 1986. The three Space Shuttles currently operational are Discovery, delivered in November 1983; Atlantis, delivered in April 1985; and Endeavour, which was built to replace Challenger and arrived at Kennedy Space Center in May 1991.

Control

The wings, fin, and stabilizers keep an airplane flying straight and level. A pilot, however, needs the ability to make an airplane turn, climb, dive, and roll. Parts of the aircraft’s wings, fins, and stabilizers are hinged so that they can swivel. These moving parts are called control surfaces. The control surfaces are

Подпись: О The weight of passengers must be spread evenly through the aircraft to keep the plane balanced and stable.

the ailerons in the wings, the elevators in the horizontal stabilizers, and the rudder in the vertical fin. When the pilot moves the flight controls in the cockpit, the control surfaces move and change the aircraft’s balance. The aircraft responds by turning, pitching its nose up or down, or rolling.

An aircraft’s ability to produce the amounts of pitch, roll, and yaw the pilot wants is called the aircraft’s response. Different types of aircraft often need a different response. For example, a fast response is crucial for fighter planes in combat. Modern fighters are deliberately designed to be unstable. Flight comput­ers keep a fighter plane under control until the pilot needs to make a fast maneuver, when the plane’s lack of sta­bility enables it to respond instantly to
the controls. Airliners do not need the rapid response of fighters. An airliner is more stable and responds more slowly to its controls.

. Tail

A

n aircraft’s tail helps to keep it stable in the air. The tail’s con­trol surfaces make the aircraft climb, dive, and turn to the left or right.

An airplane’s tail acts like an arrow’s feathers or a firework rocket’s long stick. The tail keeps the plane pointing in the right direction, nose first. Without a tail in place, most airplanes would crash to the ground. The Northrop B-2 Spirit stealth bomber, for example, has no tail and is therefore a very unstable aircraft. It only can be flown with the help of a powerful flight computer.

Stabilizers

A typical airplane tail has a vertical sta­bilizer, or fin, that stands up on top of the fuselage, and a horizontal stabilizer, or tailplane, which sticks out from either side of the tail fin. The fin has a moving part at the back called the rudder. When the rudder is turned to the left, the air
flowing around it pushes the plane’s tail to the right, and the aircraft’s nose turns to the left. When the rudder turns to the right, the aircraft’s nose turns to the right.

The tailplane has moving parts at the back called elevators. The elevators con­trol the aircraft’s pitch. When the eleva­tors tilt up, air flowing around them pushes the aircraft’s tail down and brings the nose up. When the elevators tilt down, the aircraft’s nose tips down as well.

Lift Engines

Another method for achieving vertical flight uses separate engines for lift and for forward flight. The lift engines are used to get airborne, and then separate forward thrust engines propel the plane normally. Once the plane is flying forward and the wings are generating lift, the lift engines are shut down. The disadvantage of this design is that the aircraft has to carry the dead weight of the lift engines, which reduces its performance.

One example of this type of aircraft is the Russian Yakovlev Yak-38 Forger. It has three jet engines. Two lift engines behind the pilot blow air straight down. The main engine provides thrust from two nozzles behind the wing. These nozzles can rotate to direct the jet exhaust downward to provide extra lift. The Yak-38 serves on Russia’s Kiev class aircraft carriers.