TNAG-2856-FCO40-4109-Hong-Kong-compensation-claim-regarding-Korean-Air-Lines-Flig-1993 — Page 98

- 27 -

1.14.2.5

1.14.2.5.1

Validation of the CVR recordings

Using the garnet film technique developed by Schlumberger Industries, it was confirmed that the track widths and spacings were compatible with those of the record head used in the Collins' CVR.

1.14.2.5.2

During playback of a copy tape, each crew audio channel was monitored throughout the duration of the recording to ensure that no changes in the frequency of the power supply interference occurred.

1.14.2.5.3

The HF radio communications were correlated with those recorded on the Tokyo ATC tape and their relative timings checked with the radio transmission keying parameters recorded on the DFDR tape. The timings of the VHF radio communications, the change of flight level, and the autopilot disconnect warnings after the attack, were consistent with the DFDR record.

1.14.3

1.14.3.1

Digital flight data recorder

Recording system design

1.14.3.1.1 KE 007 was equipped with a Teledyne flight data acquisition unit (FDAU). Electrical signals of various types from the numerous sources monitored were fed to this unit where they were processed to a common 0 to 5 volt DC format and then multiplexed into an ARINC 573 serial digital signal that consisted of a string of binary zeros and ones in the form of square waves.

1.14.3.1.2. The signal processing depended on the type of signal input. One group of parameters, which included the magnetic heading, was measured by synchros from which outputs were fed to the FDAU. In the Teledyne FDAU, the conversion from recorded digital numbers to synchro angles was not a linear relationship but a trigonometric function which deviated from linear values by up to +4°.

1.14.3.1.3 In the ARINC 573 format, parameters were monitored in a basic four-second cycle known as a frame. This was divided into subframes 1 to 4, each of which spanned one second and contained sixty-four twelve-bit words. The first word in each subframe was a synchronization word that was unique to that subframe number.

1.14.3.1.4 There was a fixed grouping of words in the frame in which certain words contained measurements with a twelve-bit resolution whilst others had a ten-bit resolution with two bits reserved for bistate signals. Some words were also grouped together so that a parameter could be sampled at rates varying from once per four seconds to four times per second.

1.14.3.2

DFDR description

1.14.3.2.1 KE 007 was equipped with a Sundstrand 573A DFDR, part number 981-60009-010 and serial number 3069. The DFDR recorded the ARINC 573 serial digital signal that was generated in the FDAU sequentially on the four tracks of a reversing 0.25 inch Vicalloy metal tape at a tape speed of 0.43 inches/second with a packing density of 1 786 bits/inch. The tape had a length of approximately 800 ft which enabled it to retain the previous twenty-five hours of information.