I India

icing - Any deposit of ice forming on an aircraft. This can alter the aircraft's weight and flight characteristics.

IFR (Instrument Flight Rules) - Refers to the general weather conditions pilots can expect at the surface and applies to the weather situations at an airport during which a pilot must use instruments to assist take off and landing. IFR conditions for fixed wing aircraft means the minimum cloud ceiling is greater than 500 feet and less than 1,000 feet and/or visibility is greater than 1 mile and less than 3 miles. When weather conditions are below the minimum prescribed for VFR, only instrument-rated pilots may fly in accordance with IFR.

ILS (Instrument Landing System) - Located at most major airports, this navigational equipment employs two separate antennae to provide pilots with vertical and horizontal guidance to the runway.

IM (Inner Marker) - A marker beacon used with an ILS (CAT II) precision approach located between the middle marker and the end of the ILS runway. It transmits a radiation pattern keyed at six dots per second. It indicates to the pilot, both aurally and visually, that the aircraft is at the designated decision height (DH), normally 100 feet above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach.

IMC (Instrument Meteorological Conditions) - Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimum specified for VMC.

inclement weather - Rough, severe or stormy weather.

incursions - See runway incursions

India - Designator for the letter "I" in the International Phonetic Alphabet.

indicated altitude - The altitude reading obtained from an altimeter, especially from a pressure altimeter adjusted to the aircraft's estimated height above mean sea level, but uncorrected for instrument error or variation from standard atmospheric conditions.

INS (Inertial Navigation System) - A self-contained navigation system. It consists of gyroscopes and accelerometers to provide attitude, heading, position, attitude, body/inertial velocity, and acceleration information. A primary navigation data source. INS loses accuracy with time due to drift of gyroscopes. INS-DNS is moderately accurate over land, not good over water.

instrument approach procedures - A series of predetermined maneuvers using flight instruments with specified protection from obstacles beginning at the initial approach fix to a point from which a landing can be completed and thereafter, if a landing is not completed.

instrument flight - A flight solely by reference to the cockpit instruments during low visibility or bad weather.

instrument landing - The use of navigational equipment to direct and land an aircraft usually used during inclement weather.

instrument weather conditions - Weather conditions that include reduced visibility and cloud ceilings that require a pilot to fly by reference to his or her cockpit instruments.

instruments - Tools used to observe, measure and control. For example, pilots use instruments to measure and observe the altitude, speed and direction of an aircraft.

intermodality - The integrated use of multiple transportation systems such as trams and aircraft.

international flights - A flight that arrives from or takes off to another country.

International Phonetic Alphabet - A system of words identifying the letters of the alphabet and numbers. The system was reached through international agreement, and uses words chosen for their ease of pronunciation by people of all language backgrounds.

ionosphere - A complex atmospheric zone of ionized gases that extends between 50 and 400 miles (80 to 640 kilometers) above the Earth's surface. It is located between the mesosphere and the exosphere and is included as part of the thermosphere.

isogonic lines - Lines of equal magnetic declination for a given time. The difference between true and magnetic north. Shown on most aeronautical charts as broken red lines, these lines connect points of equal magnetic variation.