The Air Tractor AT-602 is an agricultural aircraft that first flew in December 1995. Manufactured by Air Tractor, there are a number of versions available, starting with the radial-engined model AT-401, and culminating with the two-seat, turbo-prop AT802. Of low-wing, tail-dragger configuration, it carries a chemical hopper between the engine firewall and the cockpit.
As a model, the AT-602 is easy to built, with a large, constant chord wing that can be build on almost any flat surface. In addition, the square sided fuselage is well suited to inexperienced builders and the 602 might also be considered as an aileron trainer, even though it is primarily a scale model. With agricultural options including spray and dust, there is also the option to add that to your model. Your imagination will be the only limit.
Our plan is still in development, but if you have a desire to get one earlier, email us and we will let you know if we are able to help with an accelerated development time.
At 1/9 scale, our model will span just about 1900mm and should fly just fine on a 26cc gasser or even a large electric motor. The fuselage will be cavernous, so there will be no problems fitting radio gear, batteries, and the hopper you have always wanted. Also, you could set it up as a glider towplane. We’ll include the tow release on the plans just in case that’s what you want to do.
We’ll also be developing a smaller, electric version of this plan, probably 1/14 scale, with a span of 1200mm. It also should fly just fine on a 3-cell 2200maH pack. Although it will not have sparkling aerobatic performance because of that huge wing, it will be a great Sunday flier with no vices and a light wing-loading.
Air Tractor AT-602 – Design, Development, Production and Performance
The Air Tractor AT-602 is a purpose-built, single-seat agricultural aircraft designed for aerial application of liquid and dry chemicals, fertiliser, seed, and firefighting retardant. Manufactured by Air Tractor Inc. of Olney, Texas, it occupies the middle of the company’s product range, positioned between the AT-502 series and the larger AT-802 family. Since entering production in 1996, the AT-602 has become a popular choice with agricultural operators throughout North America, Australia, South America and Africa because it combines a large payload with comparatively low operating costs.
Origins and Development
By the early 1990s, Air Tractor recognised that many operators wanted an aircraft larger than the 500-gallon AT-502, but did not require the very large and more expensive 800-gallon AT-802.
The design objectives were to:
- increase payload without a significant increase in operating costs
- maintain excellent low-speed handling
- improve productivity on large farms
- retain the ruggedness required for operations from unsealed airstrips
- minimise maintenance requirements
Rather than designing an entirely new aircraft, Air Tractor enlarged the successful AT-502A airframe to accept a 630 US gallon (2,385 L) hopper and a more powerful engine. The prototype first flew on 1 December 1995, with FAA certification completed in June 1996, after which production commenced. The aircraft remains in production today.
Design Philosophy
The AT-602 was designed around four key principles:
- maximum payload
- structural simplicity
- ease of maintenance
- excellent pilot visibility
Unlike most general aviation aircraft, virtually every design decision favours agricultural efficiency rather than passenger comfort or cruise performance.
Airframe Design
Wing
The aircraft employs a cantilever low wing with:
- all-metal stressed-skin construction
- large wing area
- high-lift wing section
- full-span spray boom installation
- electrically operated flaps
The large wing produces:
- excellent lift at low speeds
- predictable stall characteristics
- good manoeuvrability during repeated low-level turns
- short-field capability from farm strips
The wing is designed to withstand repeated high-load manoeuvres associated with agricultural flying.
Hopper
The hopper is the defining feature of the aircraft.
Capacity:
630 US gallons (2,385 litres)
It is mounted directly over the aircraft’s centre of gravity so that aircraft balance changes very little as chemicals are dispersed.
The hopper can carry:
- liquid chemicals
- dry fertiliser
- seed
- firefighting retardant
- water
Quick-loading ports minimise turnaround time between sorties.
Fuselage
The fuselage consists of:
- welded steel cockpit structure
- aluminium semi-monocoque rear fuselage
- corrosion-resistant construction
- removable inspection panels
Because agricultural chemicals are highly corrosive, considerable attention is paid to drainage, sealing and ease of cleaning.
Cockpit
The cockpit is positioned well aft of the engine and above the wing leading edge, providing exceptional visibility.
Features include:
- panoramic forward view
- excellent downward visibility
- air conditioning (optional)
- energy-absorbing seat
- rollover protection
- pressurised chemical-resistant cockpit
- simplified engine instrumentation
- GPS guidance and application control systems
Modern aircraft are commonly equipped with precision agricultural guidance systems that automatically manage swath spacing and application rates.
Landing Gear
The AT-602 uses a conventional (tailwheel) undercarriage because it offers:
- excellent propeller clearance
- low empty weight
- high structural strength
- good operation from rough strips
- reduced maintenance
Large low-pressure tyres enable operation from soft soil and unprepared runways.
Powerplant
The aircraft is powered by one:
Pratt & Whitney Canada PT6A-60AG
Maximum output:
1,050 shp
The PT6A was selected because of its:
- exceptional reliability
- rapid power response
- excellent hot-and-high performance
- worldwide maintenance support
- resistance to foreign object damage
Power is transmitted through a large five-blade Hartzell constant-speed propeller (earlier aircraft used four-blade configurations).
Structural Design
The aircraft structure is engineered to tolerate:
- repeated high-g manoeuvres
- hard landings
- chemical exposure
- dusty environments
- high utilisation rates
Agricultural operators commonly accumulate 600–1,000 flying hours per year, making durability a critical design requirement.
Firefighting Capability
Although designed primarily for crop spraying, the AT-602 is also used for:
- wildfire suppression
- controlled burning support
- mosquito control
- environmental spraying
With suitable tanks, it can deliver water or fire retardant with high accuracy, particularly on smaller fires where large air tankers are not economical.
Production
Manufacturer:
Air Tractor Inc.
Location:
Olney, Texas, USA
Production commenced in:
1996
Production status:
Still in production
The aircraft is exported worldwide, with Australia representing one of its largest overseas markets due to the scale of broadacre farming.
Typical Specifications
| Item | Specification |
|---|---|
| Crew | 1 |
| Engine | Pratt & Whitney PT6A-60AG |
| Power | 1,050 shp |
| Propeller | Hartzell five-blade constant speed |
| Hopper Capacity | 630 US gal (2,385 L) |
| Fuel Capacity | 216 US gal (817 L) |
| Wingspan | 56 ft (17.07 m) |
| Length | 32 ft 11 in (10.03 m) |
| Height | 10 ft 10 in (3.30 m) |
| Wing Area | 336 sq ft (31.2 m²) |
| Empty Weight | ~5,500–5,830 lb (2,495–2,644 kg), depending on equipment |
| Maximum Take-off Weight | 12,500 lb (5,670 kg) |
| Useful Load | Approximately 6,900 lb (3,129 kg) |
Performance
| Performance | Value |
|---|---|
| Maximum Cruise Speed | 182 mph (158 kt) |
| Maximum Speed | Approximately 217 mph (189 kt) |
| Typical Working Speed | 145 mph (126 kt) |
| Economy Range | 600 miles (966 km) |
| Rate of Climb | 650 ft/min at MTOW |
| Stall Speed (Flaps Up) | 86 kt |
| Stall Speed (Landing Configuration) | 52 kt |
| Take-off Distance | Approximately 1,830 ft (558 m) |
Operational Characteristics
Agricultural pilots value the AT-602 for its:
- outstanding payload-to-operating-cost ratio
- stable low-speed handling
- responsive controls
- excellent visibility during spray runs
- ability to operate from short, rough airstrips
- rapid turnaround between loads
The aircraft’s large hopper allows significantly fewer refilling stops compared with smaller agricultural aircraft, improving productivity during peak spraying seasons.
Comparison with Other Air Tractor Models
| Model | Hopper Capacity | Engine Power | Typical Role |
|---|---|---|---|
| AT-402B | 400 US gal | 680 shp | Smaller farms, precision work |
| AT-502B | 500 US gal | 750 shp | Medium-scale agricultural operations |
| AT-602 | 630 US gal | 1,050 shp | Large-scale agriculture and firefighting |
| AT-802 | 810 US gal | 1,600 shp | Very large farms and aerial firefighting |
Legacy
The AT-602 has become one of the most successful large agricultural aircraft ever produced. Its combination of a 630-gallon hopper, 1,050 shp PT6A engine, rugged airframe and excellent handling makes it especially well suited to broadacre farming operations. In countries such as Australia, where fields are vast and turnaround time is critical, it offers a balance of payload, efficiency and operating cost that has ensured its continued popularity nearly three decades after its introduction.