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59 Cards in this Set
- Front
- Back
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What is meant by matter? |
Anything that occupies space and has weight.
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What are the three basic physical states in which matter can exist?
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Solid, liquid, and gas.
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What is meant by pressure?
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Force that acts on a unit of area.
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What is the standard sea level atmospheric pressure expressed in inches of mercury and in pounds per square inch?
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29.92 inches of mercury and 14.69 pounds per square inch.
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What characteristic of the atmosphere determines the speed of sound?
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Its temperature.
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What is meant by the fulcrum of a lever?
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The point about which the lever rotates.
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Give an example of a first–class lever, a second–class lever, and a third–class lever.
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First–class: A screwdriver being used to pry the lid from a can of paint.
Second–class: A wheelbarrow. Third–class: A hydraulically retracted landing gear. |
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What formula is used to find the amount of work done when an object is moved across a floor?
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Work = Force ⋅ Distance
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What determines the mechanical advantage of an arrangement of ropes and pulleys?
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The number of ropes that support weight.
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What determines the mechanical advantage of a gear train?
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The ratio between the number of teeth on the drive gear and the number of teeth on the driven gear.
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What is meant by the resonant frequency of an aircraft structure?
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The frequency that produces the greatest amplitude of vibration in the structure.
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What is the principle upon which ultrasonic inspection is based?
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Any fault within a material will change the material's resonant frequency. Comparing the resonant frequency of a known sound material with the material under test will indicate the presence of a fault.
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What are two types of fluids?
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Liquid and gaseous.
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What is meant by the density of a fluid?
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The mass–per–unit volume of the fluid.
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What is meant by the specific gravity of a fluid?
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The ratio of the density of the fluid to the density of pure water.
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What effect does the increase in temperature of a confined gas have on its pressure?
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When the volume of a gas remains constant, an increase in its temperature increases its pressure.
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What effect does an increase in the volume of a gas have on its temperature if its pressure remains constant?
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As the volume of a gas increases with a constant pressure, the temperature decreases.
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What effect does an increase in the pressure of a confined gas have on its temperature?
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Increasing the pressure of a confined gas increases its temperature.
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What is the difference in the fluids used in a hydraulic system and those used in a pneumatic system?
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Fluid used in a hydraulic system is incompressible. Fluid used in a pneumatic system is compressible.
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What effect on density altitude is caused by an increase in air temperature?
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As the temperature increases, the air density decreases and the density altitude increases.
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What effect does an increase in density altitude have on engine performance?
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As density altitude increases, air density decreases and engine performance decreases.
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What effect does high humidity have on piston engine performance?
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Water vapor is less dense than dry air and thus high humidity decreases the density of the air. The less dense air decreases engine performance.
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What does the specific gravity of the electrolyte of a lead–acid aircraft battery indicate?
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The amount of acid relative to the water in the electrolyte. This is an indication of the state of charge of the battery.
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How much force is produced by 1,000 psi of hydraulic pressure acting on a piston with an area of 20 square inches?
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20,000 pounds.
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How many cubic inches of fluid is forced out of a cylinder by a piston with an area of 20 square inches, when the piston moves five inches?
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100 cubic inches.
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What will happen to the pressure of a confined gas if the temperature of the gas is increased?
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The pressure will increase.
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What is meant by a temperature of absolute zero?
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The temperature at which all molecular movement stops.
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What is the Celsius equivalent of a temperature of 50°F?
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10°C
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What are three methods of heat transfer?
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Conduction, convection and radiation.
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What is meant by the absolute humidity of the atmosphere?
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The actual amount of water that is in a given volume of air.
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What causes ice to change into liquid water?
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The absorption of heat energy.
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What happens inside a solid material when it absorbs heat energy?
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The molecules within the material move faster.
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What is the basic unit of heat in the English system?
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British Thermal Unit.
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How much work will one Btu of heat energy perform?
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778 foot–pounds of work.
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What is the basic unit of heat in the Metric system?
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Calorie.
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How much heat energy is in a small calorie?
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The amount of heat energy that will raise the temperature of 1 gram of water 1°C.
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How much heat energy is in a large calorie (Calorie)?
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The amount of heat energy that will raise the temperature of 1 kilogram of water 1°C.
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What is the first law of thermodynamics?
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Heat energy can neither be created nor destroyed, it can only be changed in its form.
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What is the second law of thermodynamics?
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Heat energy can only flow from a body having a high temperature to a body having a lower temperature.
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What is an example of heat transfer by conduction?
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Removal of heat from an engine cylinder by air flowing over its surface.
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What is an example of heat transfer by convection?
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The uniform heating of the air in a room by a floor heater. The heated air rises and forces the cooler air down so it can be heated by conduction.
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What is an example of heat transfer by radiation?
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The heating of the Earth's surface by heat transmitted through space from the sun.
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Why do most metals expand when they are heated?
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As heat is absorbed, the electrons move faster and expand their orbits in the molecules of the metal.
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What is meant by the density of air?
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The weight of a given volume of air.
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What is meant by relative wind with regard to an airfoil?
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The direction the wind strikes an airfoil.
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What is meant by an angle of attack?
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The acute angle formed between the chord line of an airfoil and the direction the air strikes the airfoil.
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What is meant by the critical angle of attack?
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The highest angle of attack at which the air passes over the airfoil in a smooth flow. Above the critical angle of attack the airflow breaks away and becomes turbulent.
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What is meant by the stagnation point of an airfoil?
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The point on the leading edge of an airfoil at which the airflow separates, some flowing over the top and some over the bottom.
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What is the difference between speed and velocity?
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Speed is the rate at which an object is moving. Velocity is the vector quantity that expresses both the rate and direction an object is moving.
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What is meant by air density?
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The mass of air in a given volume.
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What is meant by weight?
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The measure of the force of gravity acting on a body.
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What is meant by thrust?
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The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the airplane.
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What is meant by drag?
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The aerodynamic force acting in the same plane as the relative wind striking an airfoil. Drag acts in the direction opposite to that of thrust.
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What is meant by autorotation in a helicopter?
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The aerodynamic force that causes a helicopter rotor to spin with no engine power applied to the rotor system.
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What is meant by dissymmetry of lift produced by a helicopter rotor?
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The difference in lift between the two sides of the rotor disc when the helicopter is in forward flight. The side with the advancing blade produces the greater lift because forward speed adds to the rotor speed. The side with the retreating blade produces less lift because the forward speed subtracts from the rotor speed.
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What is meant by a blade stall of a helicopter rotor?
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A condition of flight in which the retreating blade is operating at an angle of attack higher than will allow for the air to flow over its upper surface without turbulence.
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What is meant by translational lift in a helicopter?
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The additional lift produced by a helicopter rotor as the helicopter changes from hovering to forward flight.
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What is meant by ground effect in helicopter flight?
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An increase in lift when a helicopter is flying at an altitude of less than half the rotor span. This increase is produced by the effective increase in the angle of attack caused by the deflection of the downwashed air.
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What is meant by ground resonance in a helicopter?
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The destructive vibration that occurs when the helicopter touches down roughly and unevenly. The shock throws a load into the lead–lag hinges of the rotor blades and causes them to oscillate about this hinge. If the frequency of this oscillation is the same as the resonant frequency of the fuselage, the energy will cause the helicopter to strike the ground hard with the opposite skid or wheel. If corrective action is not taken immediately, ground resonance can destroy the helicopter. |
