Compass Rose--A graduated circle, usually marked in degrees, indicating directions and printed or
inscribed on an appropriate medium.
Conical Surface--An imaginary surface that extends from the periphery of the inner horizontal surface
outward and upward at a slope of 20 horizontal to one for a horizontal distance of 2,133.6 m (7,000 ft) to
a height, 152.4 m (500 ft) above the established airfield elevation. The conical surface connects the
inner horizontal surface with the outer horizontal surface. It applies to fixed-wing installations only.
Controlling Obstacle--The highest obstacle relative to a prescribed plane within a specified area. In
precision and non-precision approach procedures where obstacles penetrate the approach surface, the
controlling obstacle is the one which results in the requirement for the highest Decision Height (DH) or
Minimum Descent Altitude (MDA).
Crosswind Runway--A secondary runway that is required when the primary runway orientation does
not meet crosswind criteria (see Appendix D).
Decision Height--A height above the highest elevation in the touchdown zone, specified for a precision
approach, at which a missed approach procedure must be initiated if the required visual reference has
not been established.
Displaced Threshold--A runway threshold that is not at the beginning of the full-strength runway
Edge of Apron--The boundary of an apron, marked by painted stripe in accordance with pavement
Fixed-Wing Aircraft--A powered aircraft that has wings attached to the fuselage so that they are either
rigidly fixed or swing-wing, as distinguished from aircraft with rotating wings, like a helicopter.
Flight Path--The line connecting the successive positions occupied, or to be occupied, by an aircraft,
missile, or space vehicle as it moves through air or space.
Fuel Servicing Safety Zone (FSSZ)--The FSSZ is the area required for safety around pressurized fuel
carrying servicing components; i.e. servicing hose, fuel nozzle, single point receptacle (SPR), hydrant
hose car, ramp hydrant connection point, etc. and around aircraft fuel vent outlets. The fuel servicing
safety zone is established and maintained during pressurization and movement of fuel.
Full Stop Landing--The touchdown, rollout, and complete stopping of an aircraft to zero speed on
Grade--Also Gradient--A slope expressed in percent. For example, a 0.5 percent grade means a 0.5
meter [foot] slope in 100 meters [feet].
Ground Point of Intercept (GPI)--A point in the vertical plane of the runway centerline or center of a
helipad at which it is assumed that the straight line extension of the glide slope (flight path) intercepts
the approach surface base line (TM 95-226).
Helicopter--An aircraft deriving primarily elements of aerodynamic lift, thrust and control from one or
more power driven rotors rotating on a substantially vertical axis.
Helicopter(Light)-- helicopters with a gross weight of 2,722 kg [6,000 pounds] or less.
Helicopter(Medium)-- Helicopters with a gross weight of 2723 5,443 kg [6,001 12,000 pounds].
Helicopter(Heavy)-- Helicopters with a gross weight over 5,443 kg [1,2000 pounds].