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When reading the the written down recordings of CVR like here, for instance, it is common to see abbreviations like HOT-1, HOT-2 or CAM. I guess that CVR records multiple channels and the codes indicate the microphone that is believed to be closest to the source of the sound. But what exactly these abbreviations mean? Which others are possible?

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They may vary from report to report, and the abbreviations used will be laid out in the report before the transcript, for flight 1549 (NTSB, .pdf) they are as follows:

  • ATIS Radio transmission from the Automated Terminal Information System
  • RDO Radio transmission from accident aircraft, US Airways 1549
  • CAM Cockpit area microphone voice or sound source
  • PA Voice or sound heard on the public address system channel
  • HOT Hot microphone voice or sound source
  • INTR Interphone communication to or from ground crew

    For RDO, CAM, PA, HOT and INTR comments:

    • -1 Voice identified as the Captain
    • -2 Voice identified as the First Officer
    • -3 Voice identified as cabin crewmember
    • -4 Voice identified as groundcrew
    • -? Voice unidentified
  • FWC Automated callout or sound from the Flight Warning Computer

  • TCAS Automated callout or sound from the Traffic Collision Avoidance System
  • PWS Automated callout or sound from the Predictive Windshear System
  • GPWS Automated callout or sound from the Ground Proximity Warning System
  • EGPWS Automated callout or sound from the Enhanced Ground Proximity Warning system
  • RMP Radio transmission from ramp control at LaGuardia
  • GND Radio transmission from ground control at LaGuardia
  • CLC Radio transmission from clearance delivery at LaGuardia
  • TWR Radio transmission from the Air Traffic Control Tower at LaGuardia
  • DEP Radio transmission from LaGuardia departure control
  • 4718 Radio transmission from another airplane (Eagle flight 4718)
  • CH[1234] CVR Channel identifier 1=Captain 2= First Officer 3= PA 4= Cockpit Area Microphone
  • * Unintelligible word
  • @ Non-Pertinent word
  • & Third party personal name (see note 5 below)
  • # Expletive
  • -, - - - Break in continuity or interruption in comment
  • ( ) Questionable insertion
  • [ ] Editorial insertion

HOT vs. CAM:

This recording contained audio from Hot microphones used by the flightcrew. The voices or sounds on these channels were also, at times, heard by the CVR group on the CAM channel and vice versa. In these cases, comments are generally annotated as coming from the source (either HOT or CAM) from which the comment was easiest to hear and discern.

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