Analysis of a Disaster
Planning for the event had been going on for two and a half months, and because of the unsettled weather in the Cape at that time of year, senior officers had worked out five complex plans to put on the safest and best display possible. These ranged from a magnificant clear-weather displayvin which more than two hundred SAAF aircraft- Impalas, Mirages, Vampires, Canberras, Buccaneers, Skymasters, Shackletons, helicopters, Cessnas, Albatrosses and Dakotas- would fly past at different altitudes in ten action-packed minutes, to a display in thickly overcast weather of helicopters only, flying at five hundred feet. Three hundred and fifty pilots and crew were backed up by five hundred and fifty ground crew and communications staff.
The Operation had been planned with great precision. For the various aircraft to arrive over the dais at the right times, bearing in mind the great differences in their speeds, timing had to be calculated to split seconds.
There could be no overlaps, nor could there be large gaps between the formations. Precautions had even been made in the event of engine trouble, and pilots were instructed to head for the open sea where lifeboats and rescue squads were standing by.
Several plans had been worked out to make provision for variable weather. However all the plans were subject to the requirement that all flying was to be carried out in visual conditions, that is, the pilots would be able to see the ground at all times.
Electronic navigation aids were sited for the safe routing of aircraft, and all these were tested in practice. All pilots received written orders as well as detailed verbal pre-flight briefing, and were shown key points along the routes, from the air and on the ground.
The planners worked out holding areas for various types of aircraft, the routes they would take to the dais, the fly-past routes, the heights and speeds, the turning points and the routes from south of the saluting-base back to their bases, DF Malan Airport, the SAAF base at Ysterplaat and the Flying Training School at Langebaanweg. Summersfield was designated a reserve airfield.
Planners also made sure that routes, turns and altitudes would prevent collisions between aircraft and, if the weather should turn nasty, they would keep the aircraft away from high ground.
To make sure that the various groups of aircraft passed the saluting base within a certain number of seconds, aircraft with different speeds were grouped in blocks and instructed to fly at certain speeds and heights.
There were seven speed blocks, and the Mercurius aircraft were grouped with the Vampires and Impalas in the sixth block with a stipulated speed of 250 knots.
After the fly-past there was always the danger that the different aircraft might catch up with one another or collide on their return to base. To avoid that, formations were instructed either to fly straight on or turn to the left or right after the completion of the fly-past.
Aircraft with longer endurances, such as the Shackletons, Hercules, Dakotas, Skymasters, Albatrosses, Canberras and Buccaneers, were to fly straight ahead. Aircraft with short endurances- Vampires and Mirages- were to turn left and return to DF Malan Airport.
Turning right to return to their base at Langebaanweg, the Mercurius jets and Impalas took a breakaway route from south of the saluting base over low ground over the Swart River area. This was the safest route, for if they had turned left to return to base they would have had to fly over high ground, which would have been dangerous in bad weather.
The right turn for the Mercurius and Impala aircraft was calculated mathematically at a rate of one turn, that is, three degrees a second.
This at 250 knots, from a point thirty seconds flying time, also at 250 knots, south of the saluting-base would have given the aircraft a safe distance of two miles east of Devils Peak.
This calculation was tested in practice and found correct by the control staff. Leaders of formations were also given the opportunity to practice the turn and to comment on the practicability of this manoeuvre.
The leaders of the Mercurius and Impala teams flew the route and turned twice, once on the day of the accident, but neither made any comments to the control staff about the plan.
An extensive communications centre at Goodwood kept formation leaders and control staff under strict supervision, and the positions of formations could be ascertained and correlated with planned positions at all times. The communications system also allowed liaison between leaders of formations and enabled them to report changes in the weather and to receive new instructions from the control centre. There were no breakdowns in this communications system, and it worked perfectly.
At the various bases and over the saluting dais the weather was suitable for the rehearsal. However, during the fly-past, the base of a broken layer of cloud south of the dais was down to eight hundred feet, and approval was given by control center for formation leaders to reduce height to maintain visual flight. This was in accordance with instructions to formation leaders, including the leader of the Mercurius jets.
While flying towards the dais, the leader of the Vampires radioed to the leader of the Mercurius jets. He was thirty seconds behind the Mercurius jets, but he wanted confirmation that they were not behind time according to the tight schedule.
When the Mercurius leader confirmed that they were ten seconds late, the Vampire leader increased speed to 280 knots, at which speed he flew over the saluting dais. The distance between the Vampire and Mercurius formations at first decreased, then remained constant, which meant that the Mercurius leader also probably increased speed.
When the Mercurius formation flew into the broken cloud soon after flying over the dais, it maintained its planned height of a thousand feet. In doing so, the formation leader chose to ignore the overriding instruction that visual flight was to be maintained at all times.
Why did he do that? We can only suppose, as the board of inquiry did, that the leader regarded the flight in cloud as a common occurrence, for as a transport pilot he had complete confidence in his own ability and his instruments.
The Impalas, however, which were following the Mercurius formation, were taken by their leader below the clouds where they were able to maintain visual flight as ordered.
And what about instrument flying? The Mercurius had weather radar, but even if it was switched on, it is doubtful whether the leader would have had time to pay much attention to it.
The board of inquiry ran through the fatal flight in every detail. It flew the identical course in an identical aircraft. Then, together with evidence from eyewitnesses, it was able to reproduce the exact flight path of the Mercurius formation.
It showed that the principal cause of the accident was simply that the formation turned much wider than had been planned and which the leader had been instructed to do in his briefing before the flight.
The formation was flying faster than had been stipulated in its attempt to make up the few seconds that it had lost in the fly-past.
The Mercurius formation had to break to the right thirty seconds after flying over the saluting base and then fly back along the same bearing to Langebaanweg. Thirty seconds was adhered to, but the turn began farther south than the point planned. Again, the higher speed also resulted in a wider turn than had been planned, and the leader had not made allowance for that by turning more steeply.
The last, fatal error was in not maintaining visual contact with the ground. That would almost certainly have warned the leader that he was two miles west of his planned flight path and on a collision course with the mountain.
The board of inquiry found that the disaster was caused by the leader of the Mercurius formation not maintaining visual contact with the ground, and during the flight in the clouds, making an error of judgement by turning too wide, which resulted in a collision with the slopes of Devils Peak.