FAA Private Pilot - Glider (PGL) key terms

Published airspeeds a pilot uses to fly a glider safely, including best glide, minimum sink, stall, maximum winch or aero-tow speed, and maneuvering speed; each applies to a specific configuration, weight, and condition.

The airspeed that produces the greatest horizontal distance traveled per unit of altitude lost in still air. Flying faster or slower than this value reduces the distance available for reaching a landing area.

The airspeed at which a glider loses altitude most slowly in still air. It is lower than best glide speed and is used for maximizing time aloft, as in weak lift or when holding in a thermal.

The horizontal distance a glider travels for each unit of altitude lost, often stated as a number such as 30:1. It varies with airspeed, weight, and contamination on the wings.

A curve plotting sink rate against airspeed for a glider in still air. Pilots use it, adjusted for headwind, tailwind, or lift, to choose the airspeed that maximizes the distance or time needed.

The technique of adjusting airspeed away from best glide based on the air mass: fly faster into a headwind or sink, slower in a tailwind or lift, to maximize cross-country progress or reach a goal.

A ring setting on a variometer that tells the pilot the expected strength of the next thermal, so the instrument indicates the optimum speed to fly between thermals. Higher settings mean faster cruising speeds.

The angle between the wing chord line and the relative wind. Increasing it increases lift up to the critical angle, beyond which the wing stalls regardless of airspeed or attitude.

The angle of attack at which airflow separates from the wing and lift drops sharply. A wing stalls at this angle at any weight, airspeed, or bank angle, which is why stall recognition depends on feel and warning devices.

The tendency of a glider to yaw away from the direction of a turn when ailerons are deflected, because the downgoing wing produces more induced drag. Coordinated rudder pressure counters it.

A flight condition in which the nose points away from the turn, so the relative wind strikes the side of the glider. A forward slip is used to lose altitude quickly without gaining airspeed.

A flight condition in which the nose points into the turn and the tail swings outward, often caused by too much rudder in the turn direction. It is inefficient and can lead to a spin if the wing stalls.

An aggravated stall in which one wing is more deeply stalled than the other, causing autorotation and rapid descent. Recovery requires stopping the rotation with opposite rudder, then breaking the stall.

The ratio of the lift produced by the wings to the glider's actual weight. It increases in turns and pull-ups, raising stall speed and structural stress on the airframe.

The maximum airspeed at which full, abrupt control deflection will stall the glider before the structure is overstressed. Above this speed, control inputs should be smooth and limited.

Pressure altitude corrected for nonstandard temperature. High density altitude reduces lift, climb performance, and takeoff or launch performance, and raises true airspeed for a given indicated airspeed.

The process of confirming that the glider's total weight and center of gravity fall within the limits in its flight manual. Out-of-limit loading degrades handling, stall behavior, and structural safety.

The point where the glider's total weight is considered concentrated. A CG too far aft reduces pitch stability and stall recovery; too far forward increases stall speed and trim drag.

Water or solid weight carried to raise wing loading and improve penetration in strong conditions. Jettisonable ballast must be releasable, and its use is restricted to the limits stated in the flight manual.

The glider's weight divided by its wing area. Higher wing loading raises stall and glide speeds but improves penetration and reduces sensitivity to turbulence; lower loading favors weak lift and tight thermals.

A rising column of air warmed by the surface. Glider pilots circle in thermals to gain altitude, and the strongest lift is usually found on the sunny side of slopes, dark fields, and other heat sources.

Upward-moving air created when wind is deflected over a ridge or hill. It requires wind roughly perpendicular to the ridge and is strongest near the slope, weakening with distance downwind.

Smooth, often strong lift in standing waves downwind of mountain barriers, marked by lenticular clouds. It can extend to great altitude and is associated with strong downdrafts and turbulence below.

Turbulent, tumbling air beneath the lee side of a ridge or below a mountain wave. Rotors can produce violent up- and downdrafts and must be avoided during approach and landing.

An instrument that shows the rate of climb or descent, helping the pilot center lift and judge sink. Total-energy varieties compensate for changes caused by airspeed so the reading reflects the air mass.

A launch in which a powered towplane pulls the glider on a rope. The pilot stays high or low as briefed, avoids slack line, and releases at the agreed altitude or signal.

A ground-based winch pulls the glider up a steep climb on a cable. The pilot holds a consistent climb attitude, watches for a cable break, and lowers the nose promptly if power is lost.

A deliberately weak element in the launch rope or cable that breaks before the glider or tow aircraft is overloaded. Its rating must match the glider's maximum weight as specified in the flight manual.

Loss of launch power at low altitude, such as a rope break or winch failure. The pilot must immediately lower the nose, accelerate to a safe speed, and land ahead or in a suitable area rather than turn back.

A planned off-airport landing when lift is lost or a problem prevents reaching a runway. The pilot selects a field, flies a stable pattern, uses slips to lose excess altitude, and lands into the wind.

A cross-country flight that ends with an off-airport landing because the pilot could not find or reach lift. The pilot should plan the field early, land into wind, and secure and report the glider afterward.

Uncontrolled airspace where no ATC clearance is required. In the United States, glider operations are permitted in Class G during daylight with the required visibility and cloud clearance, but other rules still apply.

Controlled airspace that is generally not charted at the surface but begins at a designated altitude. VFR glider flights may operate in it without a clearance if weather minimums and equipment rules are met.

The visibility and cloud-clearance requirements that must be met to fly under visual flight rules. They vary by airspace class and altitude, and glider pilots must know the values for each class they use.

The required horizontal and vertical distance from clouds for VFR flight in a given airspace class. Glider pilots climbing in thermals must remain clear of clouds unless they hold an instrument clearance.

The 30-nautical-mile ring around certain large airports within which aircraft must have an operating Mode C transponder and altitude reporting, with limited exceptions that pilots should verify before flight.

An airborne radar beacon that replies to ATC interrogations and, when altitude reporting is enabled, transmits pressure altitude. Glider pilots must know when one is required and when it may be turned off.

A notice containing time-critical information about changes to facilities, services, or hazards that affect flight. Pilots must check NOTAMs during preflight planning, especially for temporary flight restrictions and closed areas.

A designated area where flight is limited or prohibited for a period, often for security, firefighting, or events. Pilots must check for TFRs before flight and remain clear unless authorized.

A VFR navigation chart that shows airspace, airports, terrain, obstacles, and navigation aids at a scale suitable for cross-country planning. Its legend explains symbols and airspace boundaries.

The angular difference between true north and magnetic north at a given location. It is applied when converting a true course from a chart to the magnetic heading flown with a compass.

The angle a pilot turns into the wind so the actual ground track matches the desired course. It depends on wind speed and direction relative to the course and changes as conditions change.