Glossary — I

IAF Indian Air Force.

IAI Israel Aircraft Industries.

IAS Indicated airspeed, airspeed indicator reading corrected for instrument error.

IATA International Air Transport Association.

ICAO International Civil Aviation Organisation.

ICH Improved Cargo Helicopter (US Army name of CH-47F).

IDF/AF Israeli Defence Force/Air Force.

IDS InterDictor Strike (variant of Tornado).

IFF Identification friend or foe.

IFR (1) Instrument flight rules (compare VFR); (2) in-flight refuelling.

IGE In ground effect: helicopter performance with theoretical flat horizontal surface just below it (for example mountain).

IIR Imaging infra-red.

ILS Instrument landing system. See Cat.

Imperial gallon 1.20095 US gallons: 4.546 litres.

INAS (1) Integrated nav/attack system (2) Inertial Navigation and Attack (3) Indian Naval Air Station.

Inc Incorporated (company constitution).

incidence The angle at which the wing is set in relation to the fore/aft axis. Often wrongly used to mean angle of attack (which see).

inertial navigation Measuring all accelerations imparted to a vehicle and, by integrating these with respect to time, calculating speed at every instant (in all three planes) and, by integrating a second time, calculating total change of position in relation to starting point.

INS Inertial navigation system.

integral construction Machined from solid instead of assembled from separate parts.

integral tank Fuel (or other liquid) tank formed by sealing part of structure.

intercom Wired telephone system for communication within aircraft.

inverter Electric or electronic device for inverting (reversing polarity of) alternate waves in AC power to produce DC.

IOC Initial operational capability.

IR Infra-red.

IRADS Infra-red acquisition and designation system.

IRCM Infra-red countermeasures.

IRIAF Islamic Republic of Iran Air Force.

IRLS Infra-red linescan (builds TV-type picture showing cool and hot regions as contrasting shades).

IRS Inertial reference system.

IRST Infra-red search and track.

ISA International Standard Atmosphere (1013.5 mb, 1 225 g/m³ and 15°C at mean sea level; lapse rate 1.98°C per 1 000 ft up to –56.5^°C at 36,090 ft).

ISAR Imaging Synthetic Aperture Radar.