Wednesday 5 December 2012

Rainmaker: Part 1 of 2

By Mitch Stirling (Air Rhod.)

Inhabitants of the Central Africa region have been involved in rainmaking for thousands of years. Evidence of this can be seen in the rock art scattered throughout the land... and in particular at Domboshawa and Silozwane caves. The 'ancients', it would seem, attempted to gain favour from their rain gods by painting lovely images on the walls of their caves. In more recent times, the Bantu folk sent invocations to their spirit mediums to bring life-giving mvura from the skies. Chaminuka was a greatly revered mudzimu in Mashonaland, and the Njelele shrine in Matabeleland was a major meeting place for rainmaking ceremonies. Then, in turn, came the commercial farmers who fired rockets skywards in the hope that moisture in the clouds could be persuaded to 'falleth as the gentle rain from heaven'. But rain - so vital for agricultural production and the welfare of the nation - has always remained fickle and unreliable; either too much, or too little (or none at all!) So... the scientists at the University of Rhodesia and the Meteorology Department (and some crazy pilots) decided that the best way to tackle the problem was to penetrate the clouds in an aeroplane and 'seed' them from within. George Mawson, Matabeleland Rainmaker (1973-1988) takes up the story in a very interesting (sometimes scary) article about how this idea progressed.

'The rainfall distribution pattern in Rhodesia varied a great deal, with Matabeleland and the western part having the lowest average rainfall per annum. First rainfall records were taken at Hope Fountain Mission in the Matopos Hills and date back to July 1888. The first official weather station opened there in 1897, followed thereafter by Bulawayo, Salisbury (Harare), Gwelo (Gweru) and Fort Victoria (Masvingo). From the records it can be seen that Salisbury had an average of 840mm of rain per annum, Bulawayo 600mm and Beit Bridge 332mm, the latter two being in Matabeleland. By 1900 there were 13 stations recording the amount of rainfall and in the years following Rhodesia's Declaration of Independence in 1965 this number had increased to 1377 stations.

Cessna 320 with modified fuselage

In spite of the dire predictions by British Prime Minister, Harold Wilson, that Rhodesia's economy would collapse, industry and farming etc increased rapidly. And with advances in technology and aircraft it was decided to implement a National Cloud Seeding operation through the Department of Meteorological Services. In 1971 Rhodesia United Air Carriers, an experienced charter company, was contracted to carry out this program with two aircraft in Salisbury and one in Bulawayo. Twin engine Beechcraft Barons were the main aircraft used throughout the cloud seeding operations and a Cessna 320, although from 1973 to 1976 I flew VP-YLT, a Cessna 210 single engine aircraft from Bulawayo to cover the Matabeleland area. A specially adapted panel fitted with two Very pistols and monitoring instruments were fitted to the aircraft in place of the rear door. And a gentleman from the local Met Department, usually known as the 'gunner', was seconded to sit in the back and fire the two pistols when required. The 'ammunition' was cartridges containing silver iodide crystals (a substitute for ice crystals). These crystals apparently induce the super-cooled water droplets in a cloud to freeze, thus acting as nuclei for what eventually reaches the ground as raindrops. The silver iodide was itself in the form of a cloud, with about one million crystals in each gram. As one can gather, the whole object of cloud seeding was to augment the rainfall by inducing existing clouds to rain or by increasing the yield of clouds that would have rained anyway. Each aircraft carried two oxygen bottles plus face masks, the oxygen supply being enough for at least three hours of usage. They also came equipped with pneumatic de-icing 'boots' - strips of rubber fitted to the leading edge of the wings. The rubber had small tunnels through which compressed air was blown to inflate the rubber ridges in the boot and break off the ice that continually accreted. Ice would also build up to 25mm thick on the front of the engine cowlings and on the very point of the spinner fitted to the propellers.

Robin Cartwright and the Cessna 210 with chute, at Salisbury

On-board Met. equipment

Very pistols

A typical day's operation in Bulawayo would start with my arrival at the airfield in the morning, followed by a visit to the Met Department where the duty officer would be looking for suitable clouds in areas of Matabeleland deficient of rain, and planning a programme with Mr Clever Nyoka who was my usual Met Officer and gunner. We would get airborne in VP-WCX, our trusty Beechcraft Baron and climb steadily towards our pre-planned area. Passing through 12 000 feet on would go the oxygen masks and at 21 000 feet above sea level we would stop climbing with the outside air temperature at minus 10 degrees centigrade, the optimum required for successful seeding. Picking our way around towering, churning clouds I would start looking for well rounded ones with tops reaching above us, select one and then fly towards the centre of it. The turbulence would increase rapidly and, with the vertical speed indicator showing more than 500 feet per minute, I would tell the gunner over the intercom to fire off his cartridges. Then as quickly as possible we would make our way out of the cloud! Once during very severe turbulence we rolled upside down, although there was very little visual indication, due to the thick cloud outside. It was all part of the learning experience which never ends in flying. Flying through one opening after another and avoiding monster clouds, which sometimes were brilliant white in colour, was a sight to behold - as though we were in a different world all on our own. On a good day this process would last for three hours, with the main problem being the constant build up of ice on the leading edge of the wings, tailplane and engine cowlings. This greatly affected the stability and increased the stalling speed of the aircraft and many a time in a turn the aircraft would start to judder as it was close to the stall. Operating the de-icing boots helped to break off chunks of ice, but elsewhere it just stuck like the 'proverbial' to an army blanket.

George Mawson (centre) with Mike Sinclair and Mr Clever Nyoka
from the Met Department

On one particular day I told the gunner to fire the cartridges off, but nothing happened; again I told him to fire, with no result. I knew something must be wrong and when I looked round he was slumped against his seat. Fortunately I noticed his foot was on the oxygen pipe to his mask - a clear case of oxygen starvation! When I pushed his foot off the pipe Clever quickly recovered and was able to carry on without any further problems. He told me he had felt tired and fallen asleep. Then suddenly, coming out of a very dark cloud, I noticed out of the corner of my right eye a flash of light hurtling towards the aircraft, followed by a loud bang and a burning smell. The first thought that crossed my mind was "Hell, I hope this is not a fire", as we would never make it back to earth from 21 000 feet, but fortunately the burning smell disappeared within two to three minutes. After this I called it a day, spoke to Bulawayo control and asked for descent clearance which was readily given. On landing back at the airfield I gave the aircraft a good look over and noticed that every navigation light bulb was shattered into tiny pieces. There was a drop of melted aluminium just below each wing tip and at the rear end of the fuselage, and the plastic covering on the cable to the white navigation light had melted for about half a metre; that was obviously what had caused the burning smell. But what really was peculiar was that all six propeller blades had a perfect arc of indentations melted into them about 12 inches from the hub!

On Christmas Eve 1980 we were seeding around the Matopos Hills avoiding the clouds which topped over 30 000 feet, because the turbulence would have been too excessive for the airframe design limits. The first raindrops began to fall over the Matopos, Maleme and Mpopome Dams and after two and a half hours we had seeded 22 clouds, a good total, so we slowly made our way back to Bulawayo. On landing we learned there had been a violent widespread storm where we had been seeding and the drive-in cinema had been blown down and destroyed! We kept our mouths shut about that one.....

On another occasion we were seeding in the area between Wankie and Victoria Falls and after two hours we were ready to begin our descent and return to Bulawayo. But Bulawayo control told us to maintain our position and altitude as there was an Air Zimbabwe Viscount en route from Vic falls to Bulawayo... no problem. Half an hour later we were still there and from a quick calculation I could see that we were going to be very tight on fuel. I called the Viscount and as he was thousands of feet below us, I decided to make tracks to Bulawayo at 21 000 feet. Twenty minutes later the Viscount radioed that they were well clear of our area and control gave me clearance to descend to Bulawayo. Fifteen minutes later our main tanks were empty, so I switched to the outers and throttled back even more whilst descending through the rain and cloud. At 12 000 feet we broke out of cloud, removed the oxygen masks, but we were still a long way from home with the outers reading quarter full. Bulawayo airfield at last came into sight with all tanks reading empty and we were cleared as number one, with a straight in approach and landed with no problem. However, from the amount of fuel we uplifted when refueling I calculated that we had had only four gallons left, cutting it far too fine for me!

... to be continued.

Photo credits: Robin DW Norton, George Mawson and Mitch Stirling


Thanks to Mitch for sharing this information with ORAFs.
Thanks also to Robin and George and Mitch for their photographs.

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At 13 July 2016 at 19:25 , Blogger Unknown said...

My father, Squadron Leader REG ("Ronnie") Sheward, DFC was the last C/O of 266 (Rhodesia) Squadron. He took command on 8 March 1945 and flew the Typhoon aircraft with the designation "ZH-Q". He was born and raised in Argentina as an expatriate Englishman and as such he found he got on very well with the Rhodesians. They seem to understand each other!

Ultimately, he took the squadron to be disbanded at Lasham airfield near Alton in Hampshire.

Unbelievably, with no regard for the preservation of history, all Typhoons were scrapped and there is now only one example left which is at the RAF Museum in Hendon. The only reason we have this one is that the Americans had it for evaluation and we managed to swap it for a Hurricane.


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