Page:Report of the Board of Inquiry into the Helderberg air disaster.djvu/31

 relating to the main deck cargo compartment smoke detection system were recorded in the on-board technical defect log. Rectification actions included the replacement of no 2B and no 3A smoke detectors and a differential pressure switch. The recovered cockpit voice recording provided conclusive proof that the smoke detection systems of the main deck cargo compartment functioned.

The approved maintenance schedule prescribes that the orifices in the smoke detection sampling manifolds be inspected for obstructions at every tenth Phase A Inspection, i.e. at 4 300 hour intervals. Such an inspection was carried out on February 2nd 1987 at 24 394 total hours i.e. 2 349 flying hours before the accident.

The aircraft's empty mass and balance were last determined on January 23rd 1984 at which time the basic empty mass was 166 129 kg and the centre of gravity (CG) position 34,1226 m (1343,41 inches) aft of the datum. This equals 26.1% of the mean aerodynamic chord (MAC). The structural maximum certificated mass was 377 842 kg for take-off and 285 762 kg for landing.

The aircraft's mass at the time of the accident was calculated as 242 855 kg and the CG position