Aviation Maintenance Terms
ADC
Air data computer.
ADF
Automatic direction finder.
ADI
Attitude director indicator.
BITE
Built-in test equipment.
CDI
Course deviation indicator.
CDU
Control display unit.
CRT
Cathode-ray tube.
DME
Distance measuring equipment.
EADI
Electronic Attitude Director Indicator.
ECAM
Electronic Centralized Aircraft Monitor.
EFIS
Electronic Flight Instrument System.
EHSI
Electronic Horizontal Situation Indicator.
EICAS
Engine Indicating and Crew Alerting System.
ELT (emergency locator transmitter)
A self-contained radio transmitter that automatically begins transmitting on the emergency frequencies any time it is triggered by a severe impact parallel to the longitudinal axis of the aircraft.
EMI
Electromagnetic interference.
FCC
Federal Communications Commission.
FCC
Flight Control Computer.
FMC
Flight Management Computer.
FPD
Freezing point depressant.
GHz (gigahertz)
1,000,000,000 cycles per second.
HRD
High-rate-discharge.
HSI
Horizontal situation indicator.
ICAO
The International Civil Aeronautical Organization.
IFR
Instrument flight rules.
INS
Inertial Navigation System.
IRS
Inertial Reference System.
IRU
Inertial Reference Unit.
LORAN A
Long Range Aid to Navigation. A hyperbolic navigation system that operates with frequencies of 1,950 kHz, 1,850 kHz, and 1,900 kHz.
LORAN C
The LORAN system used in aircraft. It operates on a frequency of 100 kHz.
LRU
Line replaceable unit.
MEK
Methyl-ethyl-ketone is an organic chemical solvent that is soluble in water and is used as a solvent for vinyl and nitrocellulose films. MEK is an efficient cleaner for preparing surfaces for priming or painting.
MFD
Multi-function display.
MHz (megahertz)
1,000,000 cycles per second.
MIG welding
Metal inert gas welding is a form of electric arc welding in which the electrode is an expendable wire. MIG welding is now called GMA (gas metal arc) welding.
MSDS
Material Safety Data Sheets. MSDS are required by the Federal Government to be available in workplaces to inform workers of the dangers that may exist from contact with certain materials.
MSL
Mean sea level. When the letters MSL are used with an altitude, it means that the altitude is measured from mean, or average, sea level.
MTBF
Mean time between failures.
NDB
Non-directional beacons.
NPN transistor
A bipolar transistor made of a thin base of P-type silicon or geranium sandwiched between a collector and an emitter, both of which are made of N-type material.
PNP transistor
A bipolar transistor made of a thin base of N-type silicon or germanium sandwiched between a collector and an emitter, both of which are made of P-type material.
PVC (Polyvinylchloride)
A thermoplastic resin used to make transparent tubing for insulating electrical wires.
RDF
Radio direction finding.
RMI
Radio magnetic indicator.
RPM
Revolutions per minute.
SHF
Super-high frequency.
SRM
Structural Repair Manual.
STOL
Short takeoff and landing.
TACAN (Tactical Air Navigation)
A radio navigation facility used by military aircraft for both direction and distance information. Civilian aircraft receive distance information from a TACAN on their DME.
TCAS
Traffic Alert Collision Avoidance System.
TIG welding
Tungsten inert welding is a form of electric arc welding in which the electrode is a nonconsumable tungsten wire. TIG welding is now called GTA (gas tungsten arc) welding.
TMC
Thrust management computer.
TR unit
A transformer-rectifier unit. A TR unit reduces the voltage of AC and changes it into DC.
UHF
Ultrahigh frequency.
VFR
Visual flight rules.
VHF
Very high frequency.
VNE
Never-exceed speed. The maximum speed the aircraft is allowed to attain in any conditions of flight.
VOR
Very high frequency Omni Range navigation.
VORTAC
An electronic navigation system that contains both a VOR and a TACAN facility.
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