ailerons: Aircraft control surfaces on the wings that control roll, used to bank the aircraft.
Air Accidents Investigation Branch: The British government’s air crash investigation unit.
Aircraft Communications Addressing and Reporting System (ACARS): Digital datalink system for transmission of short messages between aircraft and ground stations including automatic relay of data about aircraft performance and activity.
airway: Defined flight route upon which commercial aircraft are usually required to travel.
Australian Maritime Safety Authority (AMSA): The national body in charge of marine search and rescue operations.
Australian Transport Safety Bureau (ATSB): The federal government agency that investigates air crashes and other transport accidents.
autonomous underwater vehicle (AUV): Torpedo-like un-manned miniature submarine equipped with cameras, side-scan sonar, multi-beam echo-sounders and other devices, which are programmed to scan, chart and photograph underwater topography and objects on it.
auxiliary power unit (APU): Generator that can provide electrical and hydraulic power to an aircraft when the main engines are not running, operated by a small jet engine usually in the tail.
black box: see flight data recorder and cockpit voice recorder.
blind transmission: In air traffic control, a radio call from controllers to an aircraft, which is thought to be in flight, to establish communications.
Broken Ridge: Large underwater escarpment rising from the sea floor in the southern Indian Ocean off the coast of Western Australia.
Bureau of Inquiry and Analysis in Civil Aviation Security (BEA): The French government’s air accident investigation agency.
burst frequency offset (BFO): Measure of changes in frequency in electronic ‘handshakes’ between a satellite and an aircraft’s satellite data unit, used to calculate speed.
burst timing offset (BTO): Measure of changes in time, and hence distance, in electronic ‘handshakes’ between a satellite and an aircraft’s satellite data unit.
cockpit voice recorder: The aircraft ‘black box’ that automatically records voices and sounds from the plane’s flight deck.
Defence Science and Technology Group (DSTG): A branch of the Australian Department of Defence that provides specialised knowledge and analysis of military-related matters. Previously known as Defence Science and Technology Organisation (DSTO).
ditch: The act of landing an aircraft on water in an emergency.
elevator: On an aircraft, the control surface on the tail that controls pitch, or up and down movement.
first officer: The co-pilot on an aircraft.
flap: Moveable surface on the rear of an aircraft’s wing that can be deployed to change the airflow for more lift and reduced speed.
flaperon: Moveable surface on the rear of an aircraft’s wing which can be deployed as a flap for take-off and landing but acts as an aileron during cruise for controlling bank.
flight data recorder (FDR): The aircraft ‘black box’ which automatically records hundreds of flight parameters including pilot control inputs, altitude, speed and other factors.
Flight Information Region: The large global division of airspace in which air traffic control centres take responsibility for guiding air traffic.
flight management system: The computer system which guides a flight automatically according to instructions from the pilots; the autopilot.
flutter: The potentially dangerous out-of-control flapping of a control surface such as a rudder, aileron or elevator, or a flap, in flight.
Freedom of Information (FOI): In the Australian federal public service, the statutory process guided by the FOI Act in which individuals can seek documents from federal departments and agencies.
hypoxia: Lack of adequate oxygen which can cause grogginess, unconsciousness, brain damage and death, in civil aviation usually caused by accidental decompression of an aircraft at high altitude.
Inmarsat: British satellite company that owned and operated the satellite over the Indian Ocean that relayed automatic electronic ‘handshakes’ from the satellite data unit of MH370 to a ground station.
International Civil Aviation Organisation (ICAO): The Montreal-based specialised agency of the United Nations that develops and guides international protocols for air navigation and administration, including, under what is known as Annex 13, air crash investigations.
Joint Agency Coordination Centre (JACC): The administrative body established in early 2014 by the Australian federal government to coordinate the response of agencies and departments to the disappearance of MH370, including communications with the media, next-of-kin, and foreign government officials.
knot: Measure of speed in maritime and aviation navigation: one knot is one nautical mile per hour, roughly equivalent to just under two kilometres per hour.
National Transportation Safety Board (NTSB): The US government agency that investigates air crashes and other transport accidents.
nautical mile (NM): Measure of distance in maritime and aviation navigation, roughly equivalent to just under two kilometres.
Ocean Infinity: British-owned, Houston-based underwater marine survey company that conducted the second seabed search for Malaysia Airlines Flight MH370.
phugoid: A cyclical aircraft motion, usually when it is unpiloted or under only partial control, in which it naturally climbs or goes level until it slows down and approaches a stall, then dives, picks up speed, and climbs again.
pilot-in-command (PIC): The flight officer in charge of an aircraft on a flight; the captain.
primary radar: In aviation, radar which detects and tracks aircraft through the return and analysis of electronic pulses bounced off them.
ram air turbine (RAM): Device which automatically deploys from the fuselage of an aircraft into the slipstream during total engine failure to provide a bare minimum of hydraulic and electrical power to run control surfaces and essential instruments.
rapid decompression: Fast loss of pressurisation of an aircraft at high altitude, usually due to an accident which damages the integrity of the fuselage.
rating: A qualification for a pilot to fly an aircraft of a certain type or in particular conditions.
rudder: The control surface on an aircraft’s tail which controls left-or-right direction, known as yaw.
satellite data unit (SDU): The electronic unit on an aircraft which transmits and receives data and telephone and fax communications via satellite relay to ground stations. Also known as SATCOM.
Search Strategy Working Group (SSWG): The panel of international experts from overseas government air crash investigation bodies, British satellite company Inmarsat, and US aircraft manufacturer Boeing which advised the ATSB in its search for MH370.
secondary radar: Radar that detects signals emitted from an aircraft’s transponder which broadcasts its identity, position, altitude, and speed, used by air traffic controllers to keep track of flights and guide pilots.
Seventh Arc: The band in the southern Indian Ocean upon which MH370 is thought to have come down after running out of fuel. It is based on the last of seven notional rings around the Asia-Pacific region upon which MH370 is thought to have been flying at the time of each of seven roughly hourly automatic electronic ‘handshakes’ between MH370’s satellite data unit and an Inmarsat satellite over the Indian Ocean.
sonar: System used to detect, map and produce images of underwater objects and topography by analysing the return of electronic signals bounced off them through the water, much like radar does in the air.
sortie: An aerial mission – a departure, flight and return of an aircraft – such as on a search and rescue operation.
stall: The aerodynamic fail point for an aircraft where it slows to the point where the airflow over the wings is no longer fast enough to produce enough lift to keep it in the air, and it starts to fall from the sky.
towfish: The devices towed by ships on a long tether which carry side-scan sonar used to search for objects on the seabed.
trailing edge: The rear part of a wing, flap or control surface on an aircraft based on the orientation it is flying forward through the air; the opposite position to the ‘leading edge’.
transponder: Electronic device on an aircraft which transmits a signal to air traffic control radar on the ground with the plane’s identity, position, altitude and speed in real time.
Transportation Safety Board (TSB): The Canadian federal agency which investigates air crashes and other transport accidents.
underwater locator beacon (‘pinger’): The electronic devices attached to an aircraft’s black box flight recorders that automatically emit an acoustic signal when submerged, enabling searchers with ‘pinger locator’ equipment to find aircraft that have crashed in bodies of water.
waypoint: Points of latitude and longitude on airways used as reference points for air navigation and air traffic control purposes, whose names are all composed of five capital letters.
witness marks: In air crash investigation, damage marks on aircraft wreckage like cracks, tears, smudges, burns and scratches that provide clues to what caused an accident.
9M-MRO: The registration of the Boeing 777 which flew MH370.