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—The slow, smooth transition from a normal  approach attitude to a landing attitude. This ma- neuver is accomplished in a PPC by pulling down  on the steering lines to increase drag, reducing the  forward speed and decreasing the rate of descent. 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. FOUR FORCES—The four fundamental forces of  flight: lift, weight, drag and thrust. FOUR-STROKE ENGINE—The principle of opera- tion for some reciprocating engines involving the  conversion of fuel energy into mechanical energy.  The strokes are called intake, compression, power,  and exhaust. FSS—FAA Flight Service Station. 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 de- scends 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. G LOADS—Loads imposed on an airframe due to  inertia (centrifugal force). 1G of load factor repre- sents the weight of the actual aircraft. 2G repre- sents effectively twice the aircraft’s actual weight. GLOBAL POSITION SYSTEM (GPS)—A satellite- based radio positioning, navigation, and time- transfer system. GO-AROUND—The termination of a landing approach. Reference the AIM Pilot/Controller  Glossary. GO OR 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 POSITION SYSTEM. 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. INSTRUMENT FLIGHT RULES (IFR)—Rules  governing the procedures for conducting instru- ment flight. Also a term used by pilots and con- trollers to indicate type of flight plan. INDUCED DRAG—That part of total drag which  is created by the production of lift. Induced drag  increases with a decrease in airspeed. INCIDENT—An occurrence other than an accident,  associated with the operation of an aircraft, which  affects or could affect the safety of operations. IFR—See INSTRUMENT FLIGHT RULES. HYPOXIA—State of oxygen deficiency in the body  sufficient to impair functions of the brain and  other organs. HYPERVENTILATION—Occurs when an indi- vidual is experiencing emotional stress, fright, or  pain, and the breathing rate and depth increase,  although the carbon dioxide level in the blood is  already at a reduced level. The result is an exces- sive loss of carbon dioxide from the body, which  can lead to unconsciousness due to the respiratory  system’s overriding mechanism to regain control  of breathing. HOUR METER—An instrument installed in many  aircraft to show the actual number of hours the  engine has operated. The hour meter is an electri- cal clock that starts when the engine oil pressure  builds up, and runs until the engine is shut down  and the oil pressure drops to zero. HIWAS—See HAZARDOUS INFLIGHT WEATH- ER ADVISORY SERVICE. HEADWIND—A wind which blows from the direc- tion the aircraft is flying. The ground speed of an  aircraft (the speed the aircraft is moving over the  ground) is less than the speed through the air by  the velocity of the headwind. HAZARDOUS INFLIGHT WEATHER ADVISORY  SERVICE (HIWAS)—Recorded weather forecasts  broadcast to airborne pilots over selected VORs. GROUND TRACK—The aircraft’s path over the  ground when in flight. GROUNDSPEED (GS)—The actual speed of an air- craft over the ground. It is true airspeed adjusted  for wind. Groundspeed decreases with a head- wind, and increases with a tailwind. GROUND EFFECT—A condition of improved per- formance encountered when an airfoil is operating  very close to the ground. When an airfoil is under  the influence of ground effect, there is a reduction  in upwash, downwash, and wingtip vortices. As  a result of the reduced wingtip vortices, induced  drag is reduced. G-5