Radiation patterns are examined for L-Band beacon antennas mounted on aircraft ranging from small, single-engine, general aviation aircraft to the Boeing 747. The data analyzed consists of antenna gain values taken in two degree steps over a spherical surface centered at the antenna location. Data from three representative scale model aircraft are studied in detail and show the effects of various airframe structural members on the radiation lobing patterns and the relative performance of antennas located at a number of positions on each scale model aircraft. Significant observations were that: -Landing gear and flaps complicate the lobing structure but do not introduce many more low gain values. -In general, antennas mounted forward of the leading edge of the wing and on fuselage bottom centerline (not too close to nosewheel) provide the best overall performance. -As an aircraft maneuvers, antenna performance degrades in direct relationship with the severity of the roll or pitch.