ILS - instrument landing system. The approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach. The localiser provides azimuth guidance, while the glide-slope defines the correct vertical descent profile. Marker beacons and high intensity runways lights are also part of the ILS.
IMC - instrument meteorological conditions: weather below VMC minima, see below. Also associated rating used in conjunction with UK PPL.
INCERFA - uncertainty phase of search-and-rescue procedure.
INS - inertial navigation system. A gyroscope-based system which senses acceleration and deceleration and computes an aircraft\position in latitude and longitude with great accuracy. Used mostly by long-haul airliners, military aircraft and sophisticated business jets. Also IRS, inertial reference system.
INTER - intermittent or fluctuating, term used in Met reports.
IR - Instrument Rating
IRAN - Inspect and repair as necessary
IRE - Instrument Rating Examiner
IRT - Instrument Rating Test
ISA - International Standard Atmosphere -- a set of standard conditions or temperature and pressure which serve as a basis for comparison. ISA = pressure 1013.2 millibars, temperature 15 degrees C. Aircraft perＦＯＲＭance figures quoted by manufacturers are often based on such a \
ITT - inter-turbine temperature. Also TGT, turbine gas temperature TIT, turbine inlet temperature.
IWR - Instrument weather rating. Proposed by the JAA as a replacement for the UK\IMC rating
J
JAA - Joint Aviation Authority.
JAR - Joint Aviation Requirements, being drawn up by eighteen European states, aimed at unifying airworthiness, flight crew licensing and other criteria among signatory nations.
JAWG - Joint Airmiss Working Group. A civilian/military committee which reviews and
reports on all airmisses which occur in UK airspace.
JEFTS - Joint Elementary Flying Training Squadron based at RAF Barkston Heath, Lincolnshire
Jeppesen - U.S.-developed navigational/approach chart system with worldwide coverage,
similar to British Aerad system.
JPATS - Joint Primary Aircraft Training System. A USAF/U.S. Navy programme to select a common aircraft design as a basic pilot trainer for the two services, due to be decided next year. K
kg - kilogram(s)
kHz - kilohertz, the frequency of a radio carrier wave measured in thousands of cycles per second. 1 kHz = 1,000 Hertz.
KIAS - knots indicated airspeed.
km - kilomrtre(s)
knot (kt) - one nautical mile per hour (never one knot per hour), the standard unit of aviation speed measurement. One knot equals 1.1515 mph; one nautical mile equals 6,080 feet.
kV- kilovolt
kW - kilowatt.
L
LARS - Lower Airspace Radar Advisory service, available to all aircraft flying in uncontrolled UK airspace from 3,000 feet amsl to FL95. See also MMARS, RAS and RIS, below.
LAMS - Light Aircraft Maintenance Schedule, the CAA-approved schedule for fixed-wing light aircraft below 2,730 kg auw whose Cs of A are valid for three years subject to compliance with LAMS.
lat - latitude.
LATCC - London Area & Terminal Control Centre at West Drayton, near Heathrow.
lb - pound(s)
lbf - engine thrust in pounds force
LCD - liquid crystal display
lczt - (ILS) localizer (USA)
l/d ratio - lift /drag ratio, a measurement of the efficiency of a wing aerofoil section
LDA - landing distance available.
LED - light emitting diode
LF - low-frequency radio waves with frequencies in the 30-300 kHz band.
LITAS - low-intensity two-colour approach system.
LLTV - low light level television.
LLZ - localizer ((USA).
LOC - localiser. The azimuth guidance portion of an instrument landing system.
locator - medium-frequency non-directional radio beacon used as an aid to establishing yourself on final approach during an instrument landing procedure..
LOFT - Line-orientated flying training. Usually on large jet simulators to prepare newly-qualified commercial pilots for multi-crew airline operations
LOM - Locator outer marker
lon(g) - longitude
Loran - low-frequency hyperbolic radio long-range navigation system which measures time difference between reception of synchronised signals transmitted from ground transmitters. Loran-C, operates in the 100-110 kHz frequency band with an operating range of 600-1,500 nm independent of line-of-sight, and is becoming very popular among GA aircraft operators in the USA. M
M or mag - magnetic
Mach number - ratio of true airspeed to the speed of sound. Mach 1 is the speed of sound at sea level, ISA, approximately 1,100 feet per second or 760 mph.
MAP - missed approach point. The point on a published ILS approach expressed in time or distance from the final approach fix, or as an altitude on the glideslope, at which the missed approach procedure must be initiated if the runway or approach lights are not clearly in sight.
marker beacons (mkrs) - part of an instrument landing system using 75 MHz transmitters emitting fan-shaped or elliptical signal patterns vertically upwards, defining specific points along the glideslope. The outer marker OM is situated at or near the glideslope intercept altitude of the ILS localiser, the middle marker (MM) defines a point on the glideslope at or near decision height (DH). Markers provide aural and visual indications on a cockpit marker beacon receiver.
MATZ - military aerodrome traffic zone. An area of protected airspace surrounding certain military airfields which normally extends for a five nautical mile radius around the airfield and upwards from the surface to 3,000 feet above aerodrome level. A \final approach path to the main runway outwards from the MATZ boundary, enclosing an area two nautical miles either side of the extended runway centreline and upwards from 1,000 feet above the surface to 3,000 feet above aerodrome elevation. Although recognition of a MATZ is not mandatory for civil aircraft, all MATZ aerodromes offer a penetration service to civil traffic during operational hours.
Mayday - international radio distress call (from the French, m\help me). It signifies imminent danger to life requiring immediate assistance.
mb - millibar.
MCC - Multi-crew co-operation
MCU - management control unit
MDA - minimum descent altitude. The lowest altitude, in feet amsl, to which descent is authorised on final approach during a non-precision instrument landing (i.e. where no glideslope guidance is given) without visual reference to the runway.
MDH - minimum descent height, agl.
MEDA - military emergency diversion airfield.
medevac - medical evacuation
Met - meteorology, weather.
METAR - coded aerodrome Met report. Also SPECI, special civil aviation weather report, and TAF, terminal aerodrome forecast of weather expected.
MF - medium frequency. Radio waves with frequencies in the 300- 3,000 kHz range.
MFA - military flying area
MFD - multi-function display. An EFIS CRT offering selectable displays of weather radar, navigation maps, checklists and data other than primary flight inＦＯＲＭation.
MH - magnetic heading
MHz - Megahertz, the frequency of radio carrier waves measured in millions of cycles per second.
minimums - weather condition requirements for a particular mode of flight (e.g. for VFR operation, IFR take-offs and landings).
MLS - microwave landing system. A microwave-based instrument approach system intended to replace ILS in the 1990s and claimed to offer a number of advantages such as the ability to fly segmented and curved precision approaches.
MLW - maximum landing weight. Weight of an aircraft above whivh fuel must be burned off or jettisoned before landing or there may be risk of structual damage
mm - millimetre\
MMARS - Military Middle Airspace Radar Service, available to military and civil aircraft operating in UK airspace between FL100 and FL245.
MOA - military operations area.
MoD - UK\
mod - modification to an aircraft or equipment
mogas - car fuel, approved for use in some light aircraft subject to certain conditions.
MPA - man-powered aircraft
mph - miles per hour
MPI - major periodic inspection
MSA - minimum sector altitude or minimum safe altitude.
msl - mean sea level
MTBF - mean time between failures. Also MTTR, mean time to repair
MTMA - military terminal control area.
