Fixed-pitch propellers.  Propellers with fixed blade angles. Fixed-pitch propellers are designed as climb propellers, cruise propellers, or standard propellers. 

Fixed-wing aircraft.  An aircraft whose wing is rigidly attached to the structure. The term fixed-wing is used to distinguish these aircraft from rotary-wing aircraft, such as helicopters and autogiros. 

Flare.  See roundout. 

Flight plan.  Specified information relating to the intended flight of an aircraft that is filed orally or in writing with an FSS or an ATC facility. 

Flightpath.  The line, course, or track along which an aircraft is flying or is intended to be flown. 

Fog. Cloud consisting of numerous minute water droplets and based at the surface; droplets are small enough to be suspended in the earth’s atmosphere indefinitely. (Unlike drizzle, it does not fall to the surface. Fog differs from a cloud only in that a cloud is not based at the surface, and is distinguished from haze by its wetness and gray color.) 

Force (F). The energy applied to an object that attempts to cause the object to change its direction, speed, or motion. In aerodynamics, it is expressed as F, T (thrust), L (lift), W (weight), or D (drag), usually in pounds. 

Four forces.  The four fundamental forces of flight: lift, weight, drag and thrust. 

Four-stroke engine.  The principle of operation for some reciprocating engines involving the conversion of fuel energy into mechanical energy. The strokes are called intake, compression, power, and exhaust. 

Front.  The boundary between two different air masses. 

Front tube. The structural member of the carriage that attaches to the top of the carriage mast to the front of the fuselage. It acts as a control stop for the control bar to avoid high angles of attack. 

Fuel efficiency.  Defined as the amount of fuel used to produce a specific thrust or horsepower divided by the total potential power contained in the same amount of fuel. 

Fuel injection.  A fuel metering system used on some aircraft reciprocating engines in which a constant flow of fuel is fed 

to injection nozzles in the heads of all cylinders just outside of the intake valve. It differs from sequential fuel injection in which a timed charge of high-pressure fuel is sprayed directly into the combustion chamber of the cylinder. 

Fuel system. The system that delivers fuel to the carburetors or the fuel injection system composed of a fuel tank, fuel pickup, fuel filter, and fuel pump. 

Fuselage. The section of the WSC carriage that consists of the cockpit, containing seats for the occupants and attachments for the landing gear and wing. 

G loads.  Load imposed on an airframe due to inertia (centrifugal force). 1G of load factor represents the weight of the actual aircraft. 2G represents effectively twice the aircraft’s actual weight. 

Glidepath.  The path of an aircraft relative to the ground while approaching a landing. 

Glide ratio.  The ratio of the forward distance traveled to the vertical distance an aircraft descends when it is operating without power. For example, an aircraft with a glide ratio of 10:1 will descend about 1,000 feet for every 2 miles (10,560 feet) it moves forward. 

Global positioning system (GPS).  A satellite based radio positioning, navigation, and time transfer system used for as a reference for navigation and measures ground speed. 

Go-around.  The termination of a landing approach. Reference the AIM Pilot/Controller Glossary. 

Go/No-go decision. Decision of whether or not to make a flight based on environmental, personal or mechanical factors. A focus area for human factors study. 

GPS.  See global positioning system. 

Gross weight.  The total weight of a fully loaded aircraft including the fuel, oil, crew, passengers, and cargo. 

Ground-adjustable propeller. A type of aircraft propeller whose blade pitch angle can be adjusted when the engine is not running. The adjustment requires loosening the blades in the hub. 

Ground effect.  A condition of improved performance encountered when an airfoil is operating very close to the ground. When an airfoil is under the influence of ground 

