Listed for the exam, the main components of a CVR:
a shock-resistant recorder — tape historically, digital storage today, with an underwater locating beacon (ULB) on the case, a pinger that starts transmitting on immersion so the box can be found under water;
a cockpit area microphone (CAM) — the open microphone that captures the aural environment of the whole flight deck;
a control unit — with auto/on, test and erase controls and a headset jack;
limited flight-deck controls — such as erase and test switches; the erase function exists for the lawful routine erase after an uneventful flight and is heavily interlocked, normally usable only on the ground, which is why erasing after an occurrence is exactly the offence the rule names.
And the main parameters recorded, which together are simply every channel of flight-deck audio:
voice communications transmitted from or received on the flight deck — the radio traffic;
the aural environment of the flight deck — the CAM's channel: warnings, switches, engine note, voices off-microphone;
voice communication over the aircraft's interphone system — pilot to pilot, flight deck to cabin;
voice or audio signals introduced into a headset or speaker — whatever the pilots heard in their ears, including navigation idents and alerts;
voice communication over the public address (PA) system, if installed.
The flight data recorder
The purpose of the flight data recorder (FDR) is the numbers half of the same account: it records what the aircraft was doing, parameter by parameter, for accident and incident investigation. Its typical location is the same rear-fuselage territory as the CVR, and for the same reason. Listed for the exam, the main components of an FDR:
a shock-resistant data recorder — with its own ULB on the case;
a data interface and acquisition unit — the stage that collects the parameters from the aircraft's systems and formats them for storage;
a recording system — the digital flight data recorder (DFDR) itself;
two control units — one governing the start sequence, one the event-mark setting;
limited flight-deck controls, but including an event switch — one button the crew can press to mark this moment in the recording, so an occurrence can be found in the data afterwards; there is deliberately no erase.
The main parameters recorded on the FDR, listed for the exam:
time or a relative time count — the thread every other parameter hangs on;
attitude — pitch and roll;
airspeed;
pressure altitude;
heading;
normal acceleration — the g-loading;
propulsive/thrust power on each engine, and the flight-deck thrust or power lever position, if applicable;
flaps/slats configuration or the flight-deck selection;
ground spoilers or speed brake selection.
That list is a floor, not a ceiling: additional parameters are recorded according to the FDR's capacity and the applicable operational requirements, and a modern recorder carries hundreds of parameters beyond the mandatory core.
The aircraft condition monitoring system
The recorders serve the investigation that nobody wants; the aircraft condition monitoring system (ACMS), which the syllabus writes as the aeroplane condition monitoring system, serves the everyday. Its purpose is to monitor the condition of the aircraft and its engines for maintenance: trends, exceedances and fault reports, gathered in flight and delivered to the people who fix things. This is the machinery behind a claim module 1 made in passing: the maintenance systems that stamp engine exceedances and fault records with the clock's time are this system, matching each event to a moment so it can be tied to a phase of flight afterwards.
The structure is a data funnel. The inputs come from the aircraft's systems, such as air conditioning, autoflight, flight controls, fuel, landing gear, navigation, pneumatic, the APU (auxiliary power unit) and the engines, plus the MCDU (multifunction control and display unit), the same flight-deck keyboard the FMS lessons used, through which the crew can call up reports. At the centre sits the data management unit, deciding what is worth keeping and packaging it. The recording unit is a digital recorder, and the outputs are a printer on the flight deck and the ACARS or ATSU data link the communications module taught, which carries reports straight to the ground:
ACARS — the aircraft communications addressing and reporting system;
ATSU — the air traffic service unit, the avionics that manages the link.