A snippet from Roy Downes‘ memoirs… brilliant!
I learned about flying from that
Most flying magazines devote a page or two to this subject. So perhaps now is as good a time as any to include an account of one of the many lessons I learned, during the twenty-eight years I spent in the air.
It was a beautiful, Central African, late afternoon with eight/eighths of blue sky. Our Viscount was cruising at FL150 en-route from Harare to Blantyre in Malawi. Some sixty miles out of Blantyre, we intercepted the required 242° Radial from the Blantyre VOR and contacted Chileka ATC, who cleared us for a straight-in approach to runway 10, giving the weather conditions as: surface wind 240/10kt, visibility 10+km, weather nil, QNH 1023, QFE 928, Temperature +21°C. The quartering tailwind would give us a tailwind component of 6kt, well within the capabilities of the aircraft.
At +21°C, the heat of the day had passed and we were looking forward to a beer in the Chileka Flying Club, as we were ‘night-stopping’ in Blantyre. Runway 10/28 at Chileka Airport, Blantyre, is 7628ft long at an elevation of 2555ft AMSL. There was no ILS at the time but runway 10 was equipped with a VASI system (Visual approach slope indicator), for glide-slope guidance. At 49 miles DME, I reduced the power from the cruise RPM of 14200 to 10500, set a torque pressure of 40psi and commenced the descent. On crossing the Shire River (the only river that drains Lake Malawi and the fastest flowing in Africa), we were passing 5000 feet on the QFE and 15 nautical miles from Chileka. We were ideally placed for the planned straight-in approach. At five miles DME, I allowed the speed to decay to the flap limiting speed and selected the flaps to 20°, called for the undercarriage extension and increased the torque to 80psi. The co-pilot then completed the final items on the landing checklist. At 800 feet we were correctly positioned on the glide-slope with the speed stabilised at 120kt. The tower controller again passed the surface wind information and cleared us to land – no change, steady at 240/10kt. To think they even paid us to do this!
As I have indicated, I was certainly no stranger to the African Cumulonimbus. Repeatedly, I had successfully wrestled with these gigantic energy fields and their indescribable turbulence. I knew all there was to know about extreme turbulence – or so I imagined. At about 600 feet, I noticed we were going slightly above the glide slope – starting to experience the result of the reducing tailwind – so I reduce the torque pressure to 60psi. With the conditions as smooth as one could possibly wish for, I selected 32° flap. Then it happened. The worst turbulence encounter I had ever experienced. Without warning, the nose pitched down dramatically and the aircraft rolled violently to the left. For the next fifteen to twenty seconds, there followed the most exciting roller-coaster ride ever. Disney’s ‘Space Mountain’ was tame by comparison. I cannot describe the control inputs I made while endeavouring to prevent a semi inverted collision with the ground. A full power application had no immediate effect but as we crossed the runway threshold, we were at least the right way up. The aircraft was not responding to the power application and it appeared that we were going to contact the ground with far too high a sink rate. Then, as quickly as it had started, we flew out of this isolated ‘bubble’ of turbulence into smooth air, about 50 feet above the runway.
I regained control, landed and stopped comfortably in the remaining distance. Had the phenomenon lasted another second or two, I am in no doubt we would have crashed. With no Flight data recorders installed, the investigators could not possibly have determined the accident cause, and ‘Pilot Error’ would have been the inevitable conclusion. What then was the cause? It certainly was not the aircraft. Could it have been wake turbulence? Hardly so. The preceding aircraft, an Air Malawi DC3, had landed an hour and twenty minutes before – Chileka is no threat to Heathrow. Was it a dust devil? It seemed unlikely. African dust devils generate vast columns of dust, visible for miles and the tower controller was adamant that he had seen no such evidence. In any case, with the late afternoon temperature and the steady surface wind, the conditions were not conducive to dust devil formation. I naturally discussed the event with my fellow pilots but all I ever got from them was that ‘glazed’ look of total disbelief. Conversely, meteorologists were extremely interested and obtained detailed weather data from the area, to try to determine the reason. However, no one has yet offered a logical explanation for that ‘bubble’ of extreme turbulence. What then did I learn from this? I learned that above all, pilots should always ‘EXPECT THE UNEXPECTED.’