More aviation terms follow. Let us know if there are any terms about which you would like to learn more!

IFR (Instrument Flight Rules) Rules of the road for flights permitted to penetrate clouds and low visibility conditions by reference to cockpit flight instruments and radio navigation. Aircraft must be equipped and pilots qualified and current for IFR flight. Flight plans and ATC clearances are required. Flights are monitored and traffic separated by Air Traffic Control, usually by radar.

ILS (Instrument Landing System) A precision instrument approach system utilizing radio transmitters at the runway ends which provide precise left-right and up-down indications to the pilot permitting aircraft to land during periods of low ceilings or poor visibility.

JOINT OWNERSHIP Purchase or lease of a complete aircraft by a relatively small number of owners, often through a partnership or limited liability corporation.

LAAS (Local Area Augmentation System), an enhancement of the Global Positioning System (GPS) providing greater navigation accuracy and system integrity.

MACRS (Modified Accelerated Cost Recovery System) The current method of accelerated asset depreciation required by the United States tax code; enacted in 1986.

NONTOWERED AIRPORT An airport without a control tower – the majority of America’s 13,000 airports. Only 680 airports have control towers. Non-towered airports are not “uncontrolled.” Pilots follow traffic pattern procedures and self-announce positions and intentions using the Common Traffic Advisory Frequency (CTAF), usually called the UNICOM frequency.

NMAC (Near Mid-Air Collision) Defined by FAA as a potential collision situation between aircraft within 500 feet of each other.

PAYLOAD Anything that an aircraft carries beyond what is required for its operation during flight, theoretically cargo or passengers from which revenue is derived.

PROHIBITED AREA An airspace area where flight is prohibited except by prior arrangement with the controlling agency. An example is the P-56 area over downtown Washington, D.C., prohibiting flight over the White House.

RADAR System that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations and terrain.

RESTRICTED AREA Airspace that (when “Active” or “Hot”) usually excludes civilian aircraft. Examples: airspace for rocket flights, practice air-to-air combat or ground-based artillery practice. Temporary restricted areas are established for events such as forest fires, natural disasters or major news stories. The “controlling agency” or FAA may authorize flight through a restricted area.

SEE-AND-AVOID The FAA requirement that all pilots are ultimately responsible for separation from other aircraft when visual conditions permit spotting traffic. Even IFR flights when operating in visual weather conditions or VFR flights being issued radar advisories are responsible for visual scanning to see-and-avoid other traffic.

SQUAWK A four-digit number that a pilot dials into his transponder to identify his aircraft to air traffic controllers.

TCAD A proprietary low cost anti-collision system detecting and alerting pilots to nearby transponders but not providing evasive instructions or coordination with other aircraft.

TETRAHEDRON Ground-based, free-rotating, triangular-shaped wind direction indicator, generally placed near a runway.

UNICOM (Universal Communication) A common radio frequency (usually 121.0 mHz) used at controlled (non-tower) airports for local pilot communication. UNICOM is also used by a Fixed Base Operator for general administrative uses, including fuel orders, parking instructions, etc.

VOR (VHF Omnidirectional Range) Ground-based radio navigation aid. More than 1,000 VORs electronically define Victor Airways and Jet Airways, “highways in the sky.” Most IFR and many VFR flights follow airway routes.