Aviation Maintenance Terms
14 CFR
Title 14 of the Code of Federal Regulations
429
ARINC 429 Data Bus Standard
629
ARINC 629 Data Bus Standard
A/D
Analog/Digital; Analog-to-Digital
A/D CONV
Analog-to-Digital Converter
A/FD
Airport/Facility Directory
A/L
Autoland
AC
Alternating current. Electrical current in which the electrons continually change their rate of flow and periodically reverse their direction.
AC
Advisory Circular
AC
Advisory Circular
ac
Alternating Current
AC
Advisory Circular (FAA)
ACARS
ARINC Communication Addressing and Reporting System
ACC
Active clearance control. A system for controlling the clearance between tips of the compressor and turbine blades and the case of high-performance turbofan engines. When the engine is operating at maximum power, the blade tip clearance should be minimum, and the ACC system sprays cool fan discharge air over the outside of the engine case. This causes the case to shrink enough to decrease the tip clearance. For flight conditions that do not require such close clearance, the cooling air is turned off, and the case expands to its normal dimensions. The control of the ACC system is done by the FADEC, or full-authority digital electronic control.
ACO
Aircraft Certification Office
ACO
Aircraft Certification Office
ACR
ADS-B Aircraft Operation Compliance Report
AD
Airworthiness Directive
AD (ashless dispersant) oil
A mineral-based lubricating oil used in reciprocating engines. This oil does not contain any metallic ash-forming additives, but has additives that disperse the contaminants and hold them in suspension until they can be removed by filters.
ADC
Air data computer. An electronic computer in an aircraft that senses pitot pressure, static pressure, and total air temperature. It produces an indication of altitude, indicated airspeed, true airspeed, and Mach number. The output of ADC is usable by any of the engine or flight control computers.
ADC
Air-Sata Computer
ADC
Air data computer.
ADCP
ATC Dual-control Panel
ADEDS
Advanced Electronic Display System
ADF
Automatic Direction Finder
ADF
Automatic direction finder.
ADI
Attitude-director Indicator; Air Data Instrument
ADI
Attitude director indicator.
ADI (antidetonation injection) system
A system used with some large reciprocating engines in which a mixture of water and alcohol is sprayed into the engine with the fuel when operating at extremely high power. The air/fuel mixture is leaned to allow the engine to develop its maximum power, and the ADI fluid absorbs excessive heat when it vaporizes.
ADIRS
Air Data And Inertial Reference System
ADS-B
Automatic Dependent Surveillance - Broadcast
ADS-B
Automatic Dependent Surveillance – Broadcast
ADS-B IN
Receipt, processing, and display of other aircraft’s ADS-B transmissions. ADS-B IN is necessary to use airborne applications.
ADS-B In- Receipt
Processing, and display of other aircraft’s ADS-B transmissions. ADS-B In is necessary to utilize airborne applications.
ADS-B OUT
Transmission of an aircraft’s position, altitude, velocity, and other information to other aircraft and ATC ground-based surveillance systems.
ADS-B Out
Transmission of an aircraft’s position, altitude, velocity, and other information to other aircraft and ATC ground based surveillance systems.
ADS-R
Automatic Dependent Surveillance - Rebroadcast
ADS-R
Automatic Dependent Surveillance – Rebroadcast
AFC
Automatic Frequency Control
AFCS
Automatic Flight Control System
AFDS
Autopilot Flight Director System
AFM
Airplane Flight Manual
AFM
Airplane flight manual.
AFM
Aircraft Flight Manual
AFMS
Airplane Flight Manual Supplement
AIM
Aeronautical Information Manual
AIRB
Basic Airborne
AIRCOM
Air/Ground Communications
AM
Amplitude Modulation
AML
Approved Model List
AMP
Amperes
AMP or AMPL
Amplifier
AMS
Aerospace Material Specification
AN
Army/Navy
AND
Army Navy Design
ANSI
American National Standards Institute
ANSP
Air Navigation Service Provider
ANT
Antenna
AP
Autopilot
APB
Auxiliary Power Breaker
APC
Absolute pressure controller.
APCU
Auxiliary Power Control Unit
APU
Auxiliary power unit. A small turbine- or reciprocating- engine-powered generator, hydraulic pump, and air pump. APUs are installed in the aircraft and are used to supply electrical power, air, and hydraulic pressure when the main engines are not running.
APU
Auxiliary power unit.
APU
Auxiliary Power Unit
ARINC
Aeronautical Radio Incorporated
ARNC IO
ARINC I/O Error
ARNC STP
ARINC I/O UART Data Strip Error
ARP
Aerospace Recommended Practice
ASA
Aircraft Surveillance Applications
ASAS
Aircraft Surveillance Applications System
ASDE-X
Airport Surface Detection Equipment, Model X
ASSAP
Airborne Surveillance and Separation Assurance Processing
ASTC
Amended Supplemental Type Certificate
ASTM
American Society For Testing Materials
ATA
Air Transport Association
ATAS
ADS-B Traffic Advisory System
ATC
Air Traffic Control
ATC
Air Traffic Control
ATC
Air Traffic Control
ATCRBS
Air Traffic Control Radar Beacon System
ATCRBS
Air Traffic Control Radar Beacon System
ATCT
ATC Transponder
ATCTS
ATC Transponder System
ATF
Aerodynamic twisting force. The aerodynamic force that acts on a rotating propeller blade to increase its blade angle. The axis of rotation of a blade is near the center of its chordline, and the center of pressure is between the axis and the leading edge. Aerodynamic lift acting through the center of pressure tries to rotate the blade to a higher pitch angle.
ATS
Air Traffic Services
AUX
Auxiliary
AVC
Automatic Volume Control
AWG
American Wire Gauge
AWS
Air Weather Service
B/CU
Battery/Charger Unit
BAT or BATT
Battery
BCD
Binary-coded Decimal
BDC
Bottom dead center. The position of a piston in a reciprocating engine when the piston is at the bottom of its stroke, and the wrist pin, crankpin, and center of the crankshaft are all in line.
BHP
Brake horsepower. The actual horsepower delivered to the propeller shaft of a reciprocating or turboprop engine.
BIT
Binary Digit; Built-in Test
BITE
Built-in test equipment.
BITE
Built-in test equipment. A troubleshooting system installed in many modern electronic equipment. BITE equipment monitors engine and airframe systems, and when a fault is found, isolates it and provides maintenance personnel with a code that identifies the LRU (line replaceable unit) that contains the fault.
BITE
Built-in Test Equipment
BITS
Bus Interconnect Transfer Switch
BMEP
Brake mean effective pressure. The average pressure inside the cylinder of a reciprocating engine during the power stroke. BMEP, measured in pounds per square inch, relates to the torque produced by the engine and can be calculated when you know the brake horsepower.
BNR
Binary Numerical Reference; Binary
BP
Band-Pass
BPCU
Bus Power Control Unit
BSFC
Brake specific fuel consumption. A measure of the amount of fuel used for a given amount of power produced by a heat engine. BSFC is expressed in pounds of fuel burned per hour for each brake horse-power the engine is producing.
BT
Bus Tie
BTB
Bus Tie Breaker
BTC
Before Top Center
BUS
Electrical Bus; 429 Digital Data Bus
C.G.
Center Of Gravity
CAC
Caution Advisory Computer
CAGE
Commercial and Government Entity Code
CAMP
Continuous airworthiness maintenance program.
CAS
Calibrated airspeed.
CAT II
Category II.
CAVS
CDTI Assisted Visual Separation
CAWS
Central Aural Warning System; Caution and Warning System
CB, C/B, or CKT/BKR
Circuit Breaker
CDI
Course deviation indicator.
CDI
Course-deviation Indicator
CDTI
Cockpit Display of Traffic Information
CDU
Control display unit.
CDU
Central Display Unit
CFC
Carbon Fiber Composite
CFDIU
Centralized Fault Display Interface Unit
CFDS
Centralized Fault Display System
CFR
Code of Federal Regulations
CH or CHAN
Channel
CHGR
Charger
CKT
Circuit
CLK
Clock
CLR
Clear
CMCS
Central Maintenance Computer System
CMP
Configuration, maintenance, and procedures.
CMPTR
Computer
CO
Carbon Monoxide
COAX
Coaxial
COP
Copper
CP
Control Panel
CPDLC
Controller Pilot Data Link Communication
CRT
Cathode-ray tube.
CRT
Cathode ray tube. An electronic display tube in which a stream of electrons is attracted to the charged inner surface of the tube face. Acceleration grids and inner surface of the tube face. Acceleration grids and focusing grids speed the movement of the electrons and shape the beam to a pin- point size. Electrostatic or electromagnetic forces caused by deflection plates or coils move the beam over the face of the tube. The inside of the tube face is treated with a phosphor material that emits light when the electrons strike it.
CRT
Cathode-ray Tube; Circuit
CSD
Constant-speed drive. A component used with either aircraft gas turbine or reciprocating engines to drive AC generators. The speed of the output shaft of the CSD is held constant while the speed of its input shaft varies. The CSD holds the speed of the generator, and the frequency of the AC constant as the engine speed varies through its normal operating range.
CSE or CSEU
Control System Electronics Unit
CSEUP
Control System Electronics Unit Panel
CT
Computed Tomography
CT
Current Transformer
CTF
Centrifugal twisting force. The force acting about the longitudinal axis of a propeller blade, and which tries to rotate the blade to a low-pitch angle. As the propeller rotates, centrifugal force tries to flatten the blade so all of its mass rotates in the same plane.
CTN
Caution
CU
Control Unit; Copper
CVR
Cockpit Voice Recorder
CW
Continuous Wave
D/A
Digital-to-Analog
DAC
Digital-to-Analog Converter
DADC
Digital Air-data Computer
dB
Decibel
DBT
Dead Bus Tie
DC
Direct current. Electrical current in which the electrons always flow in the same direction.
dc
Direct Current
DCDR
Decoder
DCPC
Direct Controller Pilot Communication
DDB
Digital Data Bus
DEMOD
Demodulator
DEMUX
Demultiplexer
DFDR
Digital Flight Data Recorder
DG
Directional Gyro
DGTL
Digital
DH
Decision Height
DISC
Disconnect
DISC SOL
Disconnect Solenoid
DISTR
Distribution
DMA
Direct Memory Access
DMB
Dead Main Bus
DMC
Display Management Computer
DME
Distance-measuring Equipment
DME
Distance Measuring Equipment
DME
Distance measuring equipment compatible with TACAN.
DME
Distance measuring equipment.
DMEA
Distance-measuring Equipment Antenna
DN
Down
DU
Display Unit
E/E
Or E & E Electrical/Electronic
E1-1
First Shelf, Number 1 Equipment Rack
E2-2
Second Shelf, Number 2 Equipment Rack
EADF
Electronic Automatic Direction Finder
EADI
Electronic Attitude-director Indicator
EADI
Electronic Attitude Director Indicator.
EAROM
Electrically Alterable Read-only Memory
EAS
Equivalent airspeed.
EASA
European Aviation Safety Agency
EC
EICAS Computer
ECAM
Electronic Centralized Aircraft Monitoring
ECAM
Electronic Centralized Aircraft Monitor.
EDSP
EICAS Display Select Panel
EDU
EICAS Display Unit
EEC
Electronic Engine Control
EEC
Electronic engine control. An electronic fuel control for a gas turbine engine. The EEC senses the power-lever angle (PLA) engine RPM, bleed valve, and variable stator vane position, and the various engine pressures and temperatures. It meters the correct amount of fuel to the nozzles for all flight conditions, to prevent turbine over-speed and over- temperature.
EFI
Electronic Flight Instrument
EFIS
Electronic Flight Instrument System
EFIS
Electronic Flight Instrument System
EFIS
Electronic Flight Instrument System.
EFISCP
EFIS Control Panel
EFISCU
EFIS Comparator Unit
EFISG EFIS
Symbol Generator
EFISRLS EFIS
Remote Light Sensor
EGT
Exhaust gas temperature. The temperature of the gases as they leave the cylinder of a reciprocating engine or the turbine of a gas turbine engine.
EHSI
Electronic Horizontal-situation Indicator
EHSI
Electronic Horizontal Situation Indicator.
EHSID
Electronic Horizontal-situation Indicator Display
EHSV
Electrohydraulic Servo Value
EICAS
Engine Indicating and Crew Alerting System
EICAS
Engine Indicating and Crew Alerting System.
EICAS
Engine indicating and crew alerting system. An electronic instrumentation system that monitors airframe and engine parameters and displays the essential information on a video display on the instrument panel. Only vital information is continually displayed, but when any sensed parameters fall outside of their allowable range of operation, they are automatically displayed.
ELCU
Electrical Load Control Unit
ELEC
Electric; Electronic
ELECT
Electrical
ELEX
Electronics; Electrical
ELT
Emergency Locator Transmitter
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.
EMC
Electro Magnetic Compatibility
EMER GEN
Emergency Generator
emf
Electromotive Force
EMFI
Electromechanical Flight Instrument
EMI
Electromagnetic Interference
EMI
Electromagnetic Interference
EMI
Electromagnetic interference.
EP
External Power
EP AVAIL
External Power Available
EPC
External Power Contactor
EPCS
Electronic Power Control Switch
EPR
Engine pressure ratio. The ratio of the turbine discharge total pressure to the compressor inlet total pressure. EPR is normally used as the parameter to determine the amount of thrust an axial-flow turbojet or turbofan engine is producing.
EPROM
Erasable Programmable Read-only Memory
EPU
Estimated Position Uncertainty
ESHP
Equivalent shaft horsepower. A measure of the power produced by a turboprop engine. ESHP takes into consideration both the shaft horsepower delivered to the propeller and the thrust developed at the engine exhaust. Under static conditions, one shaft horsepower is approximately equal to 2.5 pounds of thrust.
ETFE
A copolymer of PTFE and polyethylene. Frequently referred to by the trade name, Tefzel™.
EUROCAE
European Organization for Civil Aviation Equipment
eV
Electron Volt
EVAcq
Enhanced Visual Acquisition
EWIS
As defined by§ 25.1701 of this chapter, electrical wiring interconnection system.
EXCTR
Exciter
EXT PWR
External Power
FAA
Federal Aviation Administration
FAA
Federal Aviation Administration
FAA
Federal Aviation Administration
FAA
Federal Aviation Administration.
FAA-PMA
Federal Aviation Administration Parts Manufacturer Approval
FADEC
Full-authority digital electronic control. A digital electronic fuel control for a gas turbine engine that is functioning during all engine operations, hence full authority. It includes the EEC (see EEC) and functions with the flight management computer. FADEC schedules the fuel to the nozzles in such a way that prevents overshooting power changes and over-temperature conditions. FADEC furnishes information to the EICAS (engine indication and crew alerting system).
FCC
Federal Communications Commission.
FCC
Flight Control Computer.
FCU
Flight Control Unit
FEP
Fluorinated ethylene propylene (commonly known by the trade name, Teflon™). A melt extrudable fluorocarbon resin, very similar in appearance and performance to PTFE, but with a maximum temperature rating of 200 °C.
FHA
Functional Hazard Assessment
FHP
Friction horsepower. The amount of horsepower used to turn the crankshaft, pistons, gears, and accessories in a reciprocating engine and to compress the air inside the cylinders.
FIS-B
Flight Information Services - Broadcast
FIS-B
Flight Information Services - Broadcast
FM
Frequency Modulation
FM/CW
Frequency Modulation Continuous Wave
FMC
Flight Management Computer.
FMC
Flight management computer. An electronic flight instrumentation system that enables the flight crew to initiate and implement a given flight plan and monitor its execution.
FMC
Flight Management Computer
FMCD
Flight Management Computer Control Display Unit
FMCS
Flight Management Computer System
FMS
Flight Management System
FMS
Flight Management System
FOD
Foreign object damage. Damage to components in the gas path of a turbine engine, caused by ingested objects. Debris from the runway or ramp cause FOD on the ground. Ice and birds cause most in-flight FOD.
FOD
Foreign Object Damage
FPD
Freezing point depressant.
fpm
Feet Per Minute
FREQ
Frequency
FSEU
Flap/Slat Electronic Unit
ft
Feet
FW or FWD
Forward
G/S
Glide Slope
GAL or GALY
Galley
GBAS
Ground Based Augmentation System
GCR
Generator Control Relay Auxiliary Contact
GCU
Generator Control Unit
GEB
Generator Circuit Breaker
GEN
Generator
GHz (gigahertz)
1,000,000,000 cycles per second.
GLR
Galley Load Relay
GMAW
Gas Metal Arc Welding
GMT
Greenwich Mean Time; Cordinated Universal Time
GND or GRD
Ground
GND PWR
Ground Power
GND RET
Ground Return
GND SVCE
Ground Service
GNSS
Global Navigation Satellite System
GNSS
Global Navigation Satellite System
GNSS/IRS
Global Navigation Satellite System/Inertial Reference System
GPCU
Ground Power Control Unit
GPS
Global Positioning System
GPS
Global Positioning System
GPS
Global Positioning System
GPSW
Gear Opposition Switch
GPU
Ground power unit. A service component used to supply electrical power and compressed air to an aircraft when it is operating on the ground.
GPU
Ground Power Unit
GPW
Ground Proximity Warning
GPWS
Ground Proximity Warning System
GS
Glide slope.
GSR
Ground Service Relay
GSSR
Ground Service Select Relay
GSTR
Ground Service Transfer Relay
GTAW
Gas Tungsten Arc Welding
GVA
Geometric Vertical Accuracy
GWPC
Ground Proximity Warning Computer
H/L
High/Low
HAE
Height Above Ellipsoid
HAG
Height Above Geoid
HEA
High-frequency Radio Antenna
HF (hf)
High Frequency (3 to 30 MHz)
HFCP
High-frequency Radio Control Panel
HFOM
Horizontal Figure of Merit
HI Z
High Impedance
HIL
Horizontal Integrity Level
HPL
Horizontal Protection Level
HRD
High-rate-discharge.
HRD fire extinguisher
A fire extinguisher that carries the extinguishing agent in a sealed sphere or cylinder. When the agent-discharged switch is closed, an ignited powder charge drives a cutter through a frangible disc which releases the agent. The entire contents of the container is emptied in much less than a second.
HSI
Horizontal situation indicator.
HUL
Horizontal Uncertainty Level
HZ
Hertz
Hz
Hertz
I.D.
Inner Diameter
I/O
Input/Output
IAPS
Integrated Avionics Processor System
IAS
Indicated Airspeed
IAS
Indicated airspeed.
ICA
Instructions for Continued Airworthiness
ICAO
International Civil Aviation Organization
ICAO
The International Civil Aeronautical Organization.
ICAO
International Civil Aviation Organization
ICAO
International Civil Aviation Organization.
ID
Identification
IDG
Integrated drive generator. An AC generator installed on turbine engines. An IDG incorporates a brushless, three- phase AC generator and a constant-speed drive in a single component.
IDG
Integrated Drive Generator
IF
Intermediate Frequency
IFR
Instrument Flight Rules
IFR
Instrument flight rules.
IFR
Instrument Flight Rules
IFR
Instrument Flight Rules
IGN
Ignition
IHP
Indicated horsepower. The theoretical horse-power a reciprocating engine develops.
IIS
Integrated Instrument System
ILS
Instrument Landing System
IMEP
Indicated mean effective pressure. The average pressure existing inside the cylinder of a reciprocating engine during its power stroke.
INDL
Indicator Light
INS
Inertial Navigation System.
INS
Inertial Navigation System
INST
Instrument
INSTR
Instrument
INTCON
Interconnect
INTEC
Interface
INTER
Interrogation
INTPH
Interphone
INV
Inverter
IR ILS
Receiver
IRS
Inertial Reference System.
IRS
Inertial Reference System
IRU
Inertial Reference Unit.
IRU
Inertial Reference Unit
ITP
In-Trail Procedure
kHz
Kilohertz
KSI
Thousands Of Pounds Per Square Inch
kts
Knots
kts
Knots
kV
Kilovolts
kVA
Kilovoltamperes
kVAR
Kilovoltampere Reactive
L-Band
Radio Frequency Band (390 to 1550 MHz)
LCD
Liquid crystal display. A digital display that consists of two sheets of glass separated by a sealed-in, normally transparent liquid crystal material. The outer surface of each glass sheet has a transparent conductive coating with the viewing side etched into character-forming segments with leads going to the edges of the display. A voltage applied between the front and back coatings disrupts the orderly arrangement of molecules and causes the liquid to darken so that light cannot pass through it. The segment to which the voltage is applied appears as black against a reflected background.
LCD
Liquid-crystal Display
LD
Load
LED
Light-emitting Diode
LF (lf)
Low Frequency (30 to 300 KHz)
LO Z
Low Impedance
LOC
Localizer
LORAN
Long-Range Navigation. A [Decommissioned] radio navigation system utilizing master and slave stations transmitting timed pulses. The time difference in reception of pulses from several stations establishes a hyperbolic line of position that may be identified on a LORAN chart. By utilizing signals from two pairs of stations, a fix in position is obtained.
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.
LPV
Localizer Performance with Vertical Guidance
LRU
Line replaceable unit. Aircraft components designed to be replaced as a unit while the aircraft is on the flight line.
LRU
Line Replaceable Unit
LRU
Line replaceable unit.
LS
Loudspeaker
LSB
Lower Sideband
LSPTM
Limit Switch Position Transmitter Module
LT
Light
LTS
Lights
m
meter (or “metre”), the SI metric system base unit for length
m/s
Meters per second
MAC
Mean Aerodynamic Chord
MAN/ELEC
Manual/Electric
MAP
Manifold absolute pressure. The absolute pressure that exists within the induction system of a reciprocating engine. It is the MAP that forces air into the cylinders of the engine. MAP is commonly called manifold pressure.
MBA
Marker-beacon Antenna
MCDP
Maintenance Control and Display Panel
MCDU
Multi-Function Control and Display Unit
MCDU
Multipurpose Control and Display Unit
MCP
Mode Control Panel
MDE
Modern Digital Electronics
MEC
Main Equipment Center; Main Engine Control
MEG or MEGA
Million
MEK
Methul ethyl ketone. A volatile, water soluble, organic chemical compound that is used as a solvent to remove oily contaminants from ignition system components.
MEK
Methylethylketone
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.
MEM
Memory
METO
Maximum Except-Take Off
MF
(mf) Medium Frequency (300 KHz to 3 MHz)
MFD
Multi-Function Display
MFD
Multifunction display. A liquid crystal or CRT display that shows a number of parameters and replaces several analog-type indicators.
MFD
Multi-function display.
MHz
Mega Hertz
MHz
Megahertz
MHz
Megahertz
MHz (megahertz)
1,000,000 cycles per second.
MIC
Microphone
MICRO-P
Microprocessor
MIG
Metal Inert Gas
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.
MILLI
One One-thousandth (0.001)
MKR BCN
Marker Beacon
MOPS
Minimum Operation Performance Standards (RTCA documents)
MOPS
Minimum Operational Performance Standards
MS
Military Standard
MSDS
Material Safety Data Sheets
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.
MSEC
(ms) Milliseconds
MSG
Message
MSL
Mean Sea Level
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-failure
MTBF
Mean time between failures.
MUX
Multiplexer
mV
Millivolts
N/A
Not Applicable or No Change
NACA
National Advisory Committee for Aeronautics. This organization, dedicated to the technical development of aviation, has been superseded by NASA.
NACA cowling
A long-chord cowling used over a radial engine. The forward portion of this cowling has an aerodynamic shape that produces a forward pull, and the rear portion extends back to fair in with the fuselage. There is a narrow peripheral gap between the rear of the cowling and the fuselage for the cooling air to escape. Some NACA cowlings have controllable flaps over this opening to control the amount of cooling air that flows through the engine.
NACP
Navigational Accuracy Category for Position
NACV
Navigational Accuracy Category for Velocity
NAS
National Aerospace System
NAS
National Aerospace Standard
NASA
National Aeronautics and Space Administration.
NAV
Navigation
NC
Normally Closed; Not Connected; No Connection
NDB
Nondirectional Beacon
NDB
Non-directional beacons.
NDB (ADF)
Nondirectional beacon (automatic direction finder).
NDI
Nondestructive Inspection
NEG
Negative
NIC
Navigational Integrity Category
NICBARO
Barometric Altitude Integrity Code
NM
Nautical Mile
NM
Nautical mile.
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.
NSEC
(ns) Nanoseconds
NTSB
National Transportation Safety Board
NVM
Nonvolatile Memory
OAM
Original Aircraft Manufacturer
OBS
Omni Bearing Selection
OC
Overcurrent
OEM
Original Equipment Manufacturer
OF
Over-Frequency
OPSPECS
Operations specifications.
OVV or OV
Overvoltage
OVVCO or OVCO
Overvoltage Cutout
P-S
Parallel to Series
PA
Passenger Address; Power Amplifier
PARA/SER
Parallel to Serial
PCB
Plenum chamber burning. A method of thrust augmentation used on engines with vectored nozzles. Fuel injected into the fan-discharge air is burned to increase thrust.
PCU
Passenger Control Unit; Power Control Unit
PFD
Permanentmagnet Generator
PMA
Parts manufacturer approval.
PMA
Parts Manufacturer Approval
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.
POA
Position Offset Applied
POC
Portable oxygen concentrator.
POH
Pilot’s Operating Handbook. A document published by the airframe manufacturer and approved by the FAA that lists the operating conditions for a particular model of aircraft. Engine operating parameters are included in the POH.
POS
Positive
POT
Potentiometer; Plan Of Test
PR
Power Relay
PRL
Parallel
PROM
Programmable Read-Only Memory
PROX
Proximity
PRT
Power recovery turbine. A turbine driven by exhaust gases from several cylinders of a reciprocating engine. Energy extracted from exhaust gases by the turbine is coupled, through a fluid clutch, to the engine crankshaft.
PSEU
Proximity Switch Electronic Unit
PSI
Pounds Per Square Inch
PTFE Tape (Insulation)
Polytetrafluoroethylene tape. (commonly known by the trade name, Teflon™), wrapped around a conductor and then centered with heat, fusing the layers into a virtually homogeneous mass. It is used both as a primary insulation against the conductor, and as an outer layer or jacket over a shield. Maximum temperature rating is 260 °C.
PV diagram
A diagram showing the relationship between the volume of a cylinder and the pressure during a cycle of engine operation.
PVC (Polyvinylchloride)
A thermoplastic resin used to make transparent tubing for insulating electrical wires.
PVF2
Polyvinylidine Fluoride. A fluorocarbon plastic, that when used in aircraft wire, is invariably radiation cross-linked and employed as the outer layer.
PWR
Power
PWR SPLY
Power Supply
QPL
Qualified Products List
QTY
Quantity
r-t
Receiver-Transmitter
RA
Resolution Advisory (TCAS II)
RA
Resolution Advisory
RA
Radio Altimeter; Radio Altitude
RAD
Radio
RAIM
Receiver Autonomous Integrity Monitoring
RAIND
Radio Altimeter Indicator
RAM
Random-Access Memory
RART
Radio Altimeter Receiver-Transmitter
RAT
Ram Air Turbine
RC
Radius of Containment
Rc
Radius of containment
RCCB
Remote-Control Circuit Breaker
RCL
Recall
RCVR
Receiver
RCVR/XMTR
Receiver/Transmitter
RDF
Radio direction finding.
RDMI
Radio Distance Magnetic Indicator
RF (rf)
Radio Frequency
RF energy
Electromagnetic energy with a frequency high enough to radiate from any conductor through which it is flowing.
RFI
Radio-Frequency Interference
RFM
Rotorcraft Flight Manual
RFMS
Rotorcraft Flight Manual Supplement
RLS
Remote Light Sensor
RMI
Radio magnetic indicator.
RMI
Radio Magnetic Indicator
RNAV
Area navigation.
RPM
Revolutions per minute. A measure of rotational speed. One rpm is one revolution made in one minute.
RPM
Revolutions per minute.
rpm
Revolution Per Minute
RTV
Room Temperature Vulcanizing
RVSM
Reduced Vertical Separation Minimum
s
second, the SI metric system base unit for time or time interval
SA
Selective Availability
SAE
Society of Automotive Engineers. A professional organization that has formulated standards for the automotive and aviation industries.
SAE
Society of Automotive Engineers
SAE
Society Of Automotive Engineers
SAT
Static Air Temperature
SATCOM
Satellite communications.
SATCOM
Satellite Communication
SBAS
Satellite-Based Augmentation System
SBS
Surveillance and Broadcast Services
SC
Special Committee
SCR
Silicon-Controlled Rectifier
SDA
System Design Assurance
SDI
Source Destination Identifier
SELCAL
Selective Calling System
SER DL
Serial Data Link
SG
Symbol Generator
SHF
Super-high frequency.
SIL
Source Integrity Level
SILSUPP
SIL Supplement
SIS
Signal-in-Space
SITA
Société International De Telecommunications Aeronautiques
SMAW
Shielded Metal Arc Welding
SMD
Surface Mounted Device
SNR
Signal-to-Noise Ratio
SOAP
Spectrometric oil analysis program. An oil analysis program in which a sample of oil is burned in an electric arc and an analysis is made of the wavelength composition of the resulting light. Each chemical element in the oil, when burned, produces light containing a unique band of frequencies. A computer analyzes the amount of each band of frequencies and prints out the number of parts of the element per million parts of the entire sample. SOAP can predict engine problems by warning the engine operator of an uncharacteristic increase of any elements in the oil.
SOL
Solenoid
SOLV
Solenoid Valve
SOM
Start Of Message
SOT
Start Of Transmission
SPKR
Speaker
SPR
Software Problem Report
SQL
Squelch
SRM
Structural Repair Manual.
SSB
Single Sideband
SSID
Supplemental Structural Inspection Documents
SSM
Sign Status Matrix
SSR
Secondary Surveillance Radar
ST
Synchro Transmitter
STAT INV
Static Inverter
STBY
Standby
STC
Supplemental Type Certificate
STC
Supplemental Type Certificate
STOL
Short takeoff and landing.
SURF
Basic Surface Situation Awareness
SURF (Basic Surface)
An ADS-B application that displays traffic over an airport surface map underlay, and is used to support the flight crew in making decisions about taxiing, takeoff, and landing. The underlying map may depict runways only, or runways, taxiways, and other movement areas.
SW
Switch
SYM GEN
Symbol Generator
T-R
Transformer-Rectifier
TA
Traffic Advisory (TCAS II)
TACAN
Ultra-high frequency tactical air navigational aid.
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.
TAI
Thermal anti-ice. A system used to prevent the formation of ice on an aircraft by flowing heated air inside the structure.
TAS
Traffic Advisory System
TAS
True airspeed.
TAT
True Air Temperature
TBDP
Tie Bus Differential Protection
TBO
Time between overhauls. A time period specified by the manufacturer of an aircraft engine as the maximum length of time an engine should be operated between overhauls without normal wear causing parts of the engine to be worn beyond safe limits. TBO depends upon proper operation and maintenance in accordance with the engine manufacturer’s recommendations. The overhaul of an engine when it reaches its TBO hours is not mandatory, except for certain commercial operators that have the requirement written into their operations manual.
TC
Type Certificate
TC
Type Certificate
TCAS
Traffic Alert and Collision Avoidance System
TCAS
I TCAS system that does not provide resolution advisories
TCAS
II TCAS system that provides resolution advisories
TCAS
Traffic alert and collision avoidance system. An airborne system that interrogates mode A, C, and S transponders in nearby aircraft and uses the replies to identify and display potential and predicted collision threats.
TCAS
Traffic Alert and Collision Avoidance System
TCAS
I Traffic Alert and Collision Avoidance System (generation 1)
TCAS
II Traffic Alert and Collision Avoidance System (generation 2)
TCAS
A traffic alert and collision avoidance system.
TCAS
Traffic Alert Collision Avoidance System.
TCAS
Traffic Alert and Collision Avoidance System
TCAS I
A TCAS that utilizes interrogations of, and replies from, airborne radar beacon transponders and provides traffic advisories to the pilot.
TCAS II
The second and current generation of instrument warning TCAS. It offers all the benefits of TCAS I, but also offers the pilot direct, vocalized instructions to avoid danger, known as a "Resolution Advisory" (RA). TCAS II systems coordinate their resolution advisories before issuing commands to the pilots, so that if one aircraft is instructed to descend, the other will typically be told to climb — maximizing the separation between the two aircraft.
TCAS II
A TCAS that utilizes interrogations of, and replies from airborne radar beacon transponders and provides traffic advisories and resolution advisories in the vertical plane.
TCAS III
A TCAS that utilizes interrogation of, and replies from, airborne radar beacon transponders and provides traffic advisories and resolution advisories in the vertical and horizontal planes to the pilot.
TCDS
Type Certificate Data Sheets
TDC
Top dead center. The position of a piston in a reciprocating engine when the piston is at the top of its stroke and the wrist pin, crankpin, and center of the crankshaft are all in line.
TDC
Top Dead Center
TEL
Tetraethyl lead.
TFR
Transfer
TIG
Tungsten Inert Gas
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.
TIS-B
Traffic Information Service – Broadcast
TIS-B
Traffic Information Service - Broadcast
TIT
Turbine inlet temperature. The temperature of the gases from the combustion section of a gas turbine engine as they enter the turbine inlet guide vanes or the first stage of the turbine.
TMC
Thrust management computer.
TMC
Thrust Management Computer
TMS
Terminal Marking Sleeve
TMS
Thrust Management System
TMSP
Thrust Mode Select Panel
TOM
Time of Measurement
TR unit
A transformer-rectifier unit. A TR unit reduces the voltage of AC and changes it into DC.
TRU
Transformer-Rectifier Unit
TSFC
Thrust specific fuel consumption. A measure of efficiency of a turbojet or turbofan engine. It is a measure of the number of pounds of fuel burned per hour for each pound of thrust produced.
TSO
Technical Standard Order
TSO
Technical Standard Order
TSO
Technical standard order.
TSO
Technical Standard or der
TSOA
Technical Standard Order Authorization
TXPDR
Transponder
UAT
Universal Access Transceiver
UAT
Universal Access Transceiver
UBR
Utility Bus Relay
UDF engine
Un-ducted Fan™. The trade name registered by General Electric for a type of ultra-high-bypass turbofan engine that drives one or more wide-blade propellers that have between eight and twelve blades. These blades, which are not enclosed in a duct or shroud, are very thin, have wide chords, and are highly swept back in a scimitar shape that enables them to power airplanes flying in the speed range near Mach 0.8.
UF
Underfrequency
UHB (ultra-high-bypass) engine
A turbine that drives a pair of ducted or un-ducted contrarotating propellers which have eight to 12 variable-pitch blades. These blades are very thin, have wide chords, and are swept back with a scimitar shape that allows them to power airplanes flying in the speed range of Mach 0.8. The blades are made of advanced composites for high strength and light weight. USH engines may be of either the tractor or pusher type, and have a bypass ratio in excess of 30:1.
UHF
Ultrahigh Frequency (300 MHz to 3 GHz)
UHF
Ultrahigh frequency.
UNDF
Underfrequency
UNDV
Undervoltage
US
Underspeed
USB (us)
Upper Sideband
USEC
Microseconds
UTC
Coordinated Universal Time
UV
Undervoltage
UV
Utraviolet
V
Volts; Voltage; Vertical; Valve
V ac, Vac, or VAC
Volts Alternating Current
V dc, Vdc, or VDC
Volts Direct Current
V1
The maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
V2
Takeoff safety speed
V2
Takeoff safety speed.
V2min
Minimum takeoff safety speed.
VA
Volt-Amperes
VA
Design maneuvering speed.
VAPP
Target approach airspeed
VAR
Volt-Ampere Reactive
VB
Design speed for maximum gust intensity.
VC
Design cruising speed.
VD
Design diving speed.
VDF /MDF
Demonstrated flight diving speed.
VEF
The speed at which the critical engine is assumed to fail during takeoff.
VF
Design flap speed.
VFC /MFC
Maximum speed for stability characteristics.
VFE
Maximum flap extended speed
VFE
Maximum flap extended speed.
VFOM
Vertical Figure of Merit
VFR
Visual flight rules.
VFR
Visual Flight Rules
VFR
Visual Flight Rules
VFTO
Final takeoff speed.
VH
Maximum speed in level flight at maximum continuous power
VH
Maximum speed in level flight with maximum continuous power.
VHF
Very high frequency.
VHF
Very high frequency.
VHF (vhf)
Very High Frequency (30 to 300 MHz)
VIFF
Vectoring in forward flight. A method of enhancing the maneuverability of an airplane by vectoring the exhaust gases and/or fan-discharge air to produce thrust components not parallel to the longitudinal axis of the aircraft.
VLE
Maximum landing gear extended speed.
VLO
Maximum landing gear operating speed.
VLOF
Lift-off speed.
VLSI
Very Large-Scale Integration
VMC
Minimum control speed with the critical engine inoperative.
VMO
Maximum operating limit speed
VMO /MMO
Maximum operating limit speed.
VMU
Minimum unstick speed.
VNE
Never-exceed speed. The maximum speed the aircraft is allowed to attain in any conditions of flight.
VNE
Never-exceed speed
VNE
Never-exceed speed.
VNO
Maximum structural cruising speed.
VOR
Very high frequency Omni Range navigation.
VOR
VHF Omnirange; Visual Omnirange
VOR
Very High Frequency Omnidirectional Range
VOR
Very high frequency omnirange station.
VORTAC
An electronic navigation system that contains both a VOR and a TACAN facility.
VORTAC
VOR Tactical Air Navigation
VORTAC
Collocated VOR and TACAN.
VR
Voltage Regulator
VR
Rotation speed.
VREF
Reference landing speed.
VRMS
Volts Root Means Square
VS
Stalling speed or the minimum steady flight speed at which the airplane is controllable
VS0
The stalling speed or the minimum steady flight speed in the landing configuration.
VS1
The stalling speed or the minimum steady flight speed obtained in a specific configuration.
VSA
Visual Separation on Approach
VSR
Reference stall speed.
VSR1
Reference stall speed in a specific configuration.
VSRO
Reference stall speed in the landing configuration.
VSW
Speed at which onset of natural or artificial stall warning occurs.
VTOSS
Takeoff safety speed for Category A rotorcraft.
VX
Speed for best angle of climb.
VY
Speed for best rate of climb
VY
Speed for best rate of climb.
W
Watts
WAAS
Wide Area Augmentation System
WARN
Warning
WCP
Weather Radar Control Panel
WEA
Weather
WEU
Warning Electronics Unit Power Supply
WGS-84
World Geodetic System-1984
WGS-84
World Geodetic System 1984
WPT
Waypoint
WX (WXR)
Weather Radar
XCVR
Transceiver
XDCR
Transducer
XFMR
Transformer
XFR
Transfer
XL-ETFE
A process of radiation cross-linking the polymer chains is used to thermally set the plastic. This prevents the material from softening and melting at elevated temperature.
XMIT
Transmit
XMTR
Transmitter
XPDR
Transponder
µ
Micro
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