Aerodynamics Of Planes

.. e air over the wings creating lift. This initial force is usually found in the form of a propeller or a jet engine. An exception to those forms of thrust is a glider. A glider still needs an initial force to begin flight, which is usually found in a tow plane.

The most commonly used thrust mechanism is a propeller. The propeller will continue to be the most commonly used because of its effectiveness and cheapness. Due to the jet engines high cost and high speeds it will remain primarily a military aircraft power plant. The physics of thrust used in aircraft is semi-complicated. Firstly, in the case of the propeller the propeller must be large enough to displace or pull enough air to keep the aircraft in flight.

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On the other hand jet engines must be able to displace a small amount of air at much higher speeds than the propeller. As an aircraft speeds up in must displace air at faster amounts causing more drag. This factor creates a barrier of speed within the Earth’s atmosphere. Although some aircraft do come extremely close to this barrier of speed such as the SR-71 and the space shuttle. The SR-71 or surveillance aircraft can reach speeds of over mach two, or two times the speed of sound approximately 14,000mph.

The space shuttle on the other hand can reach speeds of over mach five, or 36,000mph while orbiting the Earth. Both are extremely fast and made of strong, lightweight, and fire retardant materials. Today new designs for propulsion is being created such as thrust vectoring. Thrust vectoring is the ability for a jet engine to change the direction of air changing the direction of flight without using the rudder. In conclusion, without thrust or an initial power source flight is not possible. Stability and Control Stability of an aircraft during flight is crucial. To understand stability one must imagine a three-space Cartesian coordinate system, or 3-D space.

The aircraft must be controlled on its entire axis, x, y, and z. In order to keep a straight flight a rudder or vertical stabilizer must be added to the rear of the aircraft. For unhampered flight on the horizontal plane horizontal stabilizers must be added to the rear of the aircraft. Nothing needs to be added to nose of the aircraft due to the thrust of the engine. All stabilizers are important on an aircraft without one the aircraft would just spin out of control.

This is seen often when a helicopter spins out of control when the tail fan loses power. In all cases the torque of the propeller would cause an induced spin and the outcome would be disaster. New designs in stabilizer technology have allowed for lightweight aircraft to be produced. Instead of having a horizontal stabilizer and a vertical stabilizer both is put together to give just two small stabilizers emanating from the fuselage at forty-five degree angles eliminating the need for three stabilizers. The pilot has the ability to control the aircraft’s entire axis by two control devices called a pedal and a stick, or a specialized steering wheel.

Making the stick one of the most important devices inside a cockpit. High Speed Flight Minimal speed flight and high-speed flight vary in several degrees. An important aspect of this variation is related to the speed of sound. The speed of sound or sound barrier is the speed of sound moving through a given space. The actual speed of sound is varied at different altitudes due to the density of air, and how much air sound has to displace. At sea level the speed of sound is approximately 761 mph. In the early 1940’s the sound barrier seemed almost impossible until the X wing class experimental aircraft had been developed.

The speed of sound was unattainable by a conventional propeller; therefore new kinds of thrust had to be developed known as the jet engine. The jet engine carried aircraft into a new age of flight. The first aircraft to reach the speed of sound was the X-1 flown by the famous Chuck Yeager on October 14, 1947. The X-1 was shaped like a bullet because at the time it was believed to be the most aerodynamic design. The X-1 found out several important changes in flight during, before, and after an aircraft reaches the speed of sound.

The X-1 found out that when an aircraft reaches the speed of sound it is at a very unstable point of flight, but before or after the speed of sound the flight was more stable. They also found out about shock waves and how they affect flight. “In order to understand how high speed affects the compressibility of the air, let us consider an example of wave motion. Suppose we drop pebbles into a pool of water and observe the waves resulting from these disturbances. If we drop all pebbles at the same spot, but placed at equal time intervals, the waves would all spread out from a single point.

The outermost wave would be from the first pebble, the next wave from the second, and so on. Now suppose that we drop the pebbles at the same time interval but slowly move to the right as we drop them. Notice that the waves are moving faster than our forward speed. Finally, we proceed at a rate faster than the waves are able to move. Each pebble hits outside of the wave made by the previous pebble. Just as we drop the fourth pebble, the waves pile up at the forefront of our motion and tend to reinforce each other (Smith 191-192).” These shock waves build up on the nose of the aircraft creating a disturbance over the wings.

The Concord has a bendable nose so at supersonic flight it can reduce the disturbance over the wing to allow a more steady and smooth flight. Another way to decrease the disturbance over the wings are to move the wings lower than the horizontal stabilizer or visa versa to allow the shock waves moving over each wing to miss each other. Most aircraft today do not have enough fuel to maintain the speed of sound for great distances. Engineers have designed a brand new aircraft known as the F-22, which has the ability to fly an entire mission at supersonic speeds. The speed of light is unattainable by aircraft due to drag.

We have no materials that could with stand the heat caused by the friction of the air moving over its body, nor materials strong enough to be able to take the enormous drag. Today there is no thrust capability that would allow for the speed of light. Although aircraft has proved such things as time dilation it is still impossible for an aircraft to travel at 900,000 miles per second. Technology Essays.