Cockpit Voice Recorder — Page 501, Lesson 598

Right, let's get into the Cockpit Voice Recorder — the CVR. This is a system you'll be operating and, more importantly, relying on, throughout your career, so let's build it from the ground up. The principal function of the CVR is to preserve vital information in the event of an air accident. That information is recoverable and is used by the Accident Investigation Branch — the AIB. So think of it as the flight deck's memory, kept specifically for investigators if something goes wrong. Now, what does it actually record? It automatically records the last 30 minutes of communications and conversations on the flight deck. On some aircraft, that's extended to 2 hours. That's a key distinction to remember — 30 minutes standard, 2 hours on some types. When is it operational? This is a critical operational point. The CVR is operational whenever 115 volts AC power is applied to the aircraft, OR any engine is running, OR the aircraft is airborne. So it's not just when you're flying — it's live whenever the aircraft has electrical power on the ground too. The system itself comprises four main units: a tape recorder, a control unit, a monitor display, and an area microphone. The units and their locations are shown in Figure 37.1. Now, let's talk about the recording requirements. In accordance with OPs Regulations — that's Operations Regulations — the recorder must record from before the aircraft is capable of moving under its own power, until it is no longer able to do so. But it should also record pre-start procedures and post engine shut-down procedures. So the window is wider than just taxi to shutdown. What parameters are recorded? Let me list them precisely. First, voice communications transmitted from or received on the flight deck. Second, the aural environment of the flight deck — that's the ambient sound, captured by the area microphone. Third, voice communication of flight crew members using the aeroplane's interphone system. Fourth, voice or audio signals introduced into a headset or speaker. And fifth, voice communication of flight crew members using the PA system — the public address system. Now, the physical unit itself. The tape recorder is located inside a crash-proof metal box. It's painted red or orange, and it's normally placed at the rear of the aircraft, often adjacent to the flight data recorder — the FDR. The high-impact case is designed to withstand shock, high temperature, and fire. So it's built to survive the very accident it's meant to document. On the front of the unit is fitted an underwater locating device — the ULD. This device emits a continuous series of ultrasonic pulses to help locate a submerged CVR. It's automatically activated by water, and the battery will last several days. So if the aircraft goes into water, the ULD switches on by itself and pings away so recovery teams can find the recorder. So to tie it together: the CVR preserves the last 30 minutes to 2 hours of flight deck audio, it's powered up whenever the aircraft has AC power or an engine running or is airborne, it captures five specific categories of audio, and it's housed in a crash and fire-resistant box with an underwater locator beacon. That's the complete picture of the system.