as necessary to carry the port and starboard fin, port tailplane and several other pieces of empennage to their final positions. None of these parts, except the starboard fin, displayed any damage that could have occurred at the point if impact.
The port tailplane front spar had pulled out along its length, shearing all its rivets. Examination of the main impact zone indicated that the fuselage struck at right angles to the main mark down the slope and the sideways cartwheel or flick might have thrown empennage parts in to the air forward of, and to the right of, the impact area.
Examination of the point of impact of the port wingtip fuel tank indicated that the angle that the tank struck the ground was such that, had the tank been attached to the aircraft, the empennage should then have hit the ground. The tank was therefore most probably detached from the aircraft while still in the air. Positions of the No. 3 and 4 ailerons and part of the port wing support this reasoning.
The dump valves of both port and starboard tip tanks were found in the fully open position. As these valves are electro-mechanically driven, they were probably intentionally open and most likely before the port tip tank impact since this tank still had a considerable amount of fuel left over in it, judging by the flash fire area. The forward portion of the starboard tip tank, on the other hand, showed no signs of flash fire or explosion, indicating that its fuel content at the time of impact must have been low. The open dump valves appear to suggest that the pilot must have been busy dumping fuel in order to reduce the load on the airframe when it experienced the heavy turbulence and just before the aircraft began disintegrating. The aircraft weighed about 43 213 kg (95,242 lb) at the time of the accident.
In an attempt to reconstruct the events leading up to the crash, another Shackleton of the same weight and load as Shackleton 1718, took off from Runway 34 at DF Malan on August 22, 1963 to attempt to emulate as closely as possible the course and climb tempo of the stricken aircraft. Based on this emulation, it was ascertained that Shackleton 1718 was either at or very close to its intended cruise altitude of 2 896 m (9,500 ft) AMSL.
Instrument Flight Rules (IFR) flight had been authorised and the aircraft had been operating under IFR conditions at the time of its demise.
The Board was satisfied that the flight crew were under all circumstances both qualified and capable of performing the mission with which they had been tasked.
The accident occurred over State ground; property of the Department of Forestry. The terrain was unplanted, deforested and in its natural state. No claim could thus be made by the Department. There was no damage to private or other military property.
Shackleton 1718 was manufactured in August 1957. Although possessing a maximum take-off weight of 45 372 kg (100,000 lb), for its final flight it lifted off at 43 938 kg (96,840 lb). Since the aircraft was heavily laden with its maximum weight point close to the rearmost limit, the pilots would have experienced some instability in the yawing (left/right) plane.
The Board established that the impact speed of the aircraft was high and that this, combined with the resulting fire following the crash, caused almost complete destruction of the aircraft. There was no attempt by the crew to use parachutes and all aboard are assumed to have perished in the high G impact.
The Board established that the atrocious weather was a significant contributory factor in this accident. Wind was about 148 km/h (92 mph) due to the unstable air mass forming convection currents. Cloud cover extended from 305 m (1,000 ft) to 8 841 m (29,000 ft) AMSL with associated heavy precipitation. Due to the turbulence, the moist unstable air mass and low icing height resulted in unusually high icing conditions from 1 220 m to 1 829 m (4,000 ft-6,000 ft).
Air Force headquarters telephonically informed the Board that the maximum acceleration permitted on the Shackleton airframe was 2.4 G. It was thus theoretically 