Physics in Aviation

Anything that occupies space and has weight.

Solid, liquid, and gas.

The capacity for doing work.

Work = Force × Distance

The number of ropes that support the weight.

The ratio between the number of teeth on the drive gear and the number of teeth on the driven gear.

The point about which the lever rotates.

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.

Force that acts on a unit of area.

29.92 inches of mercury and 14.69 pounds per square inch.

Its temperature.

The temperature at which all molecular movement stops.

10°C

Conduction, convection, and radiation.

The actual amount of water that is in a given volume of air.

The absorption of heat energy.

The molecules within the material move faster.

British Thermal Unit.

778 foot-pounds of work.

Calorie.

The amount of heat energy that will raise the temperature of 1 gram of water 1°C.

The amount of heat energy that will raise the temperature of 1 kilogram of water 1°C.

Heat energy can neither be created nor destroyed, it can only be changed in its form.

Heat energy can only flow from a body having a high temperature to a body having a lower temperature.

Removal of heat from an engine cylinder by air flowing over its surface.

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.

The heating of the Earth's surface by heat transmitted through space from the sun.

As heat is absorbed, the electrons move faster and expand their orbits in the molecules of the metal.

Bernoulli's principle states that an increase in speed of a fluid results in a decrease in pressure of the same fluid.

Newton's first law of motion states that a body at rest remains at rest, and a body in motion will continue in a straight line unless acted on by a force.

Liquid and gaseous.

The mass-per-unit volume of the fluid.

The ratio of the density of the fluid to the density of pure water.

When the volume of a gas remains constant, an increase in its temperature increases its pressure.

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.

100 cubic inches.

The pressure will increase.

The weight of a given volume of air.

The direction the wind strikes an airfoil.

MAC is the average distance from the leading edge to the trailing edge of the wing.

The acute angle formed between the chord line of an airfoil and the direction the air strikes the airfoil.

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.

The point on the leading edge of an airfoil at which the airflow separates, some flowing over the top and some over the bottom.

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.

The mass of air in a given volume.

The measure of the force of gravity acting on a body.

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.

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.

The aerodynamic force that causes a helicopter rotor to spin with no engine power applied to the rotor system.

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 the 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

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.

The additional lift produced by a helicopter rotor as the helicopter changes from hovering to forward flight.

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.

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.

As density altitude increases, air density decreases and engine performance decreases.

The extension of flaps increases the camber of the airfoil, causing greater lift and drag.

They allow the airflow to remain attached to the upper surface of the wing at higher angles of attack, reducing stall speed.

Stall strips cause a disruption to the airflow as angle of attack increases, causing the inboard section of the wing to stall before the outboard wing.

Wing fences, or stall fences, delay the stall from reaching the ailerons, allowing improved aileron control at slower airspeeds.

Vortex generators create a small vortex, or disturbance that causes the air to remain attached to the surface at higher angles of attack.

As temperature increases, density decreases and volume increases. As density decreases, the weight of a set volume also decreases.

As the volume of a gas increases with a constant pressure, the temperature decreases.

Increasing the pressure of a confined gas increases its temperature.

Fluid used in a hydraulic system is incompressible. Fluid used in a pneumatic system is compressible.

As the temperature increases, the air density decreases and the density altitude increases.

The frequency that produces the greatest amplitude of vibration in the structure.

20,000 pounds.

As density altitude increases, engine performance decreases and aircraft aerodynamic performance decreases.

An incorrectly repaired control surface can begin to flutter during flight and separate from the aircraft.

Performance and testing data are used by aircraft manufacturers to show that their products meet the regulations that they are being certified to. The certification criteria can be complex and specific to certain aircraft and components. It is dangerous for a certified mechanic or pilot to develop their own testing of a modification without consulting the FAA Aircraft Certification Office in their district.

Confusing English and metric units of measure can lead to misreading of performance charts, fueling an aircraft with less fuel than necessary, overloading an aircraft beyond maximum allowed weight, and many other dangers.