Page:Report of the Board of Inquiry into the Helderberg air disaster.djvu/44

Rh of this aperture had melted. The signal and control wiring was routed along the top left hand side of the main deck cargo compartment in raceway G and was next to the DFDR wiring. The power supply cable was routed along the top right hand side in raceway H.

The CVR locator beacon was examined by the manufacturer who concluded that the unit had been subjected to external heat in excess of 190°C. This temperature caused the solder surrounding the water switch spring to reflow and hold the switch in the compressed position. This high temperature also damaged the potting compound around the transducer and the transducer itself, and the reflowed solder in the module caused it to short circuit. The electronics module was also found to be internally short-circuited across the battery connection.

The CVR was powered directly from the essential 115v AC bus and was wired to record from the audio selector panels of the pilot, co-pilot, flight engineer and from the cockpit area microphone. The CVR was not wired for "hot mic" recording but all verbal communications from the above mentioned crew members via oxygen masks, hand held and boom microphones would have been recorded.

"HOT MIC" recording means that the microphones are connected to a recorder in a manner that ensures the