Incident Overview
On August 8, 1963, a South African Air Force Avro Shackleton (registration 1718) from 35 Squadron crashed during a joint training exercise known as Operation CAPEX (Cape Exercise). The exercise involved the Royal Navy submarine HMS Alliance and elements of the South African Navy and Air Force. The aircraft was tasked with conducting radar detection training against the submarine. The crash occurred in the Stettynskloof valley, about 25.8 km from Worcester, between Paarl and Stellenbosch. The aircraft was completely destroyed, and there were no survivors.
Flight Preparation
The flight crew received a full briefing at Air Force Station Ysterplaat at 12:30 on August 8. The Operations Officer advised the crew to head over False Bay after takeoff and transit seaward to the exercise area, warning against the overland route due to anticipated high icing levels. Forecast weather included heavy icing between 4,000 and 6,000 ft, cloud base at 800 ft with tops to 22,000 ft, heavy turbulence, cumulonimbus clouds, hail, and heavy rain. Surface wind was 42 km/h at 340°, increasing to 92 km/h at 5,000 ft. The crew was granted special clearance to transit below 3,000 ft. The aircraft commander, Captain T.H. Sivertsen, confirmed the seaward route in his own briefing.
Despite concerns from the Flight Office at Ysterplaat, which telephoned Maritime Group Operations Centre three times to cancel the flight, permission was not granted. Just before takeoff, Captain Sivertsen informed Air Traffic Control (ATC) that he would climb to 9,500 ft and head overland towards Port Elizabeth, contrary to his briefing. The aircraft departed Runway 34 at 15:06, turning right to 350°. ATC instructed a heading of 330° to avoid Tiger Mountain, which was acknowledged. About a minute later, Captain Sivertsen requested clearance to resume 350°, which was the last radio transmission from 1718.
The Flight and Crash
At approximately 15:20, the radar technician at DF Malan requested permission to deactivate radar due to flooding from heavy rain. Before deactivation, 1718's position was given as about 40 km on a course of 100°, with a ground course of 145°. The aircraft likely crashed in the Stettynskloof/Wemmershoek Mountains area. The crash occurred around 15:25, at which time a "Mayday" transmission was heard but not recognized by ATC.
Search and Recovery
Adverse weather prevented an immediate search. On August 9, helicopters were dispatched to the Wemmershoek area but weather remained poor. Searching continued on August 10, and the wreck was finally discovered from the air at 17:18 on August 10, just over two days after the crash. The aircraft was almost completely destroyed.
Investigation Findings
The Board of Inquiry (BOI) examined the wreckage. The port elevator and a section of the upper starboard rudder had detached in flight. The starboard rudder section was found 5,314 ft from impact, and the port elevator 4,100 ft away. The BOI could not determine which broke off first. The disintegration of these flight control surfaces rendered the aircraft uncontrollable. Additionally, the port fuel tip tank broke away, removing a section of the port wing and both outer elevators. The outer starboard elevator broke away shortly after.
Examination of the port elevator showed excessive downward movement, causing hinge damage to the steel spar. It was official opinion that pilot-applied force could not have caused this damage due to control column stops. The failure of hinge bolts in tension was attributed to leverage over the spar. The outboard end of the port elevator broke away first in a rearward direction. The starboard elevator showed signs of excessive upward travel, consistent with crash damage. The upper starboard rudder failed in tension on the outboard skin, with the inboard skin torn away from front to rear.