Kōrero: Topdressing

Whārangi 5. Commercial developments of aerial topdressing

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The first commercial aerial topdressing was in Canterbury. In May 1949, Tiger Moth ZK-ASO, piloted by John Brazier of Airwork (NZ) Ltd, applied superphosphate at a rate of 56 kilograms per hectare on Sir Heaton Rhodes’s property Otahuna, at Tai Tapu. The plane carried 181 kilograms of fertiliser, and each trip took 7.5 minutes. The cost was calculated to be less than half of that for manual spreading.

The Wairarapa

About the same date, L. T. Daniell, a Wairarapa farmer, arranged for 127 tonnes of fertiliser to be dropped on 11 different properties close to Masterton aerodrome. Within two months, 200 farmers had 101,000 hectares topdressed by air.

Adapted aircraft

Before the end of 1949, war-surplus de Havilland Tiger Moths were being converted, with one cockpit transformed into a hopper capable of carrying 272 kilograms of fertiliser. These could fly from hill-country airstrips (rather than aerodromes) or the nearest flat land, reducing the turnaround time for each trip.

Aircraft including Piper Cub, Piper Pawnee, Auster and the de Havilland Beaver aircraft were later used. On the East Coast of the North Island, severe soil erosion threatened pastoral farming, and aerial topdressing provided a way to sow and maintain new pasture.

By any measure, the developments in 1949 proved a turning point for New Zealand agriculture. Fertiliser use expanded, and stock numbers doubled over the next 20 years.

Fill ’er up

Each fixed-wing topdressing plane has a truck driver who follows it around from farm to farm, using a loader to scoop fertiliser from a concrete bin. The driver fills a bucket fitted with a canvas or plastic chute, while the plane is flying. When it lands, he releases the fertiliser through the chute and into the aircraft hopper. This takes only a few seconds, and the aircraft is ready for take-off again.

Topdressing companies

By the end of 1949 five firms were spreading fertiliser: Airwork, James Aviation, Aircraft Services, Gisborne Aerial Topdressing (later Feildair), and Southern Scenic Airtrips. Wanganui Aero Work was founded in 1950. Over the next five years another 50 companies joined in, and by 1958 there were 73.

An ideal aircraft

As aerial topdressing expanded, so did the search for the ideal fixed-wing aircraft. In 1952 the Civil Aviation Department set out specifications that included, not surprisingly, the ability to operate from short airstrips in variable weather conditions while carrying at least 1,000 pounds (454 kilograms) of fertiliser. Included in the 23-point list were initial climb rates of 300 metres per minute with a full load, good ground-handling, and safety for the pilot in the event of a crash.

Building an aircraft specifically for aerial topdressing was a somewhat revolutionary request for manufacturers at the time.

The Fletcher is born

In 1953, Wendell Fletcher, of Fletcher Aviation Corporation in the US, presented a proposal to the annual conference of the Aviation Industry Association which resulted in the production of the Fletcher FU 24 aircraft. The first model was all metal, with a 225-HP engine.

The first prototype was flown in 1954, and since then over 300 Fletchers in various configurations have been built, including a modified Fletcher, called a Cresco, powered by a turbine engine. The Fletcher remains the most common fixed-wing aircraft used for aerial topdressing in New Zealand.

Me pēnei te tohu i te whārangi:

John Maber, 'Topdressing - Commercial developments of aerial topdressing', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/topdressing/page-5 (accessed 24 June 2024)

He kōrero nā John Maber, i tāngia i te 24 Nov 2008