Country of origin:

United States of America

Description:

Single-seat agricultural monoplane

Power Plant:

One 507 kw (680 shp) Pratt & Whitney Canada PT6A-15AG turboprop

Specifications:

History:

On the drawing-board at Air Tractor at the same time as the AT-400 series was a new aircraft, which became known as the AT-503. The prototype (N7309X) first flew in April 1986 and had a wingspan of 14.6 m (48 ft), aN 821 kw (1,100 shp) Pratt & Whitney PT6A-45R turboprop and a five-blade propeller. The airframe was lengthened by 35.5 cm (14 in) and had a 1,892 litre (416 Imp gal) hopper. This aircraft was aimed at the US State Department’s narcotics eradication programme, but in the event the prototype was exported to Spain in 1989 where it was used in the fire-bombing and agricultural roles.

This aircraft was followed by the AT-501 and AT-502. The former, with a 15.2 m (50 ft) wingspan, was powered by a geared Pratt & Whitney R-1340-S3H1-G radial engine providing 448 kw (600 hp) and driving a three-blade propeller. The prototype (N7314C) was first flown in January 1987, but only nine were built, development switching in favour of the AT-502. The definitive aircraft in the series, the AT-502, has been very successful.

The prototype AT-502 (N7314D) was first flown in April 1987, and this model entered service in February 1988. The first examples in this region commenced work on cotton spraying during that year. The power plant was the 507 kw (680 shp) PT6A-15AG turbine, but the airframe was certified for the installation of the 559 kw (750 shp) PT6A-34AG if required. The AT-502A, which was first flown in January 1992, had the 821 kw (1,100 shp) PT6A-45R engine, a larger fin and rudder, and an operating weight of 4,717 kg (10,400 lb).

First operators of the type in this region were Macquarie Valley Ag Services at Warren, NSW with VH-MVZ (c/n 502 –0026) and Farco at Wee Waa, NSW, VH-FRB (c/n 502-0027). More than 50 examples have been registered in this region. In November 1994 VH-AQC (c/n 502B-0265) was conveyed to Auckland, NZ where it made a short demonstration tour, this aircraft having the PT6A-34AG engine of 560 kw (750 shp). It had an extra seat on the right-hand side for the loader driver. In 1995 it became ZK-SNO.

First two registered in New Zealand were Model AT-502Bs ZK-MAA (c/n 502B-2579) with McKenzie Aviation of Gore and ZK-PTK (c/n 502B-0451) with Robalan Air Ltd of Napier.

The AT-502B prototype (N1558P) was first flown in July 1992, had a thicker wing with a 0.61 m (2 ft) longer span and introduced Hoerner wing tips, these extending the wingspan and increasing the operating weight to 4,400 kg (9,700 lb). It was claimed this model increased the width of the spray pattern by 0.91 m (3 ft) allowing coverage in fewer passes. The turbine fitted was still the PT6A-15AG, but the -27, -28 or –34AG variants of that unit could be installed. The AT-503A, which was first flown in September 1990, was a two-seat trainer variant with the PT6A-34AG engine.

A New Zealand company, Super Air Ltd, has operated a subsidiary in Malaysia known as Aerospray Transportation & Commercial Aviation on fertiliser delivery and spraying of palm oil plantations. It has operated an AT-502 9M-BCX (c/n 502-0128); while another company, Aerotech, also operated AT-502s in Sabah, in Borneo, these aircraft in the off-season being operated in South Australia.

A new variant of the series was released in 2009, this being the AT-504 which used the same airframe and same engine, the Pratt & Whitney PT6A-34AG turboprop, but was constructed with side-by-side seating for training purposes. First production aircraft went to an operator in Indonesia where it was utilised for pilot training and spraying duties.

First example in Australia became VH-INO (c/n 504-4002) with Field Air Sales & Maintenance of Ballarat, VIC in June 2009.