This is a huge plan set, and covers both the single-seat, and tandem twin-seat version, both long and short wings, and comes with full-size drawings for all formers and ribs of course. The plan set covers five very large sheets, and the model is designed around the O.S. 1.6FX, though electric would also be a great option.
At 1/6 scale, the wing spans over 2.5 Metres and the fuselage is nearly 1.7 Metres. This is not a model for the faint of heart, but everything is there on the plans for either version you wish to build. There’s even provision for a hopper tank if you want to make spraybars functional.
Ayres Thrush – Design, Development, Production and Performance
The Ayres Thrush is one of the world’s longest-serving and most successful agricultural aircraft designs. Originally conceived by renowned agricultural aircraft designer Leland Snow, the aircraft evolved through several manufacturers and names—including Snow S-2, Aero Commander Ag Commander, Rockwell Thrush Commander, Ayres Thrush, and today’s Thrush Aircraft series. Since the first prototype flew in 1956, nearly 2,000 aircraft have been produced, with modern derivatives still in service around the world.
Design Origins
Leland Snow had already established a reputation as an innovative agricultural aircraft designer while still in his twenties. His philosophy differed from many contemporaries, who adapted existing light aircraft for agricultural work. Snow believed an agricultural aeroplane should be designed specifically for its mission.
His principal design goals were:
- excellent pilot visibility
- a large centrally located chemical hopper
- rugged construction for rough airstrips
- predictable low-speed handling
- high payload relative to empty weight
- simple maintenance
- corrosion resistance
The prototype Snow S-2 first flew in 1956, incorporating many design features that remain characteristic of modern agricultural aircraft.
Evolution of the Design
The Thrush family changed ownership several times while undergoing continuous refinement.
| Year | Development |
|---|---|
| 1956 | Snow S-2 prototype first flight |
| 1957–1964 | Production by Snow Aeronautical |
| 1965 | Purchased by Aero Commander (Rockwell) |
| Early 1970s | Renamed Thrush Commander |
| 1977 | Ayres Corporation purchased the programme |
| Early 1980s | First PT6-powered Turbo Thrush introduced |
| 2003 | Thrush Aircraft acquired the design and production line |
Each new owner retained the proven basic airframe while increasing payload, engine power and structural capability.
Airframe Design
Wing
The Thrush employs a cantilever low wing optimised for low-level agricultural work.
Design features include:
- all-metal stressed-skin construction
- relatively thick wing section
- large wing area for good lift at low speed
- full-span spray boom installation
- electrically operated flaps (on later models)
The wing is engineered to tolerate repeated pull-ups, steep turns and high utilisation while maintaining forgiving stall characteristics.
Hopper
The hopper is positioned directly over the aircraft’s centre of gravity, minimising trim changes as chemicals are dispensed.
Depending on the model, hopper capacities ranged from:
- 400 US gal (1,514 L) on early Thrush Commander models
- 500 US gal (1,893 L) on later S2R-T65 variants
- up to 660 US gal (2,500 L) on the Ayres 660 Turbo Thrush
The hopper can carry:
- liquid pesticides
- herbicides
- fertiliser
- seed
- firefighting retardant
This centralised mass distribution contributes to the aircraft’s stable handling throughout a spray sortie.
Fuselage
The fuselage combines:
- welded steel tube cockpit structure
- aluminium semi-monocoque rear fuselage
- corrosion-resistant materials
- removable inspection panels
The cockpit structure also functions as a rollover-protection cage, enhancing pilot survivability in the event of an accident.
Cockpit
The single-seat cockpit was designed for maximum visibility.
Typical features include:
- excellent forward and downward visibility
- elevated seating position
- energy-absorbing seat
- air conditioning (optional on later aircraft)
- GPS guidance systems
- agricultural flow control systems
- modern glass avionics on recent variants
The pilot sits well behind the engine, allowing clear visibility of the spray swath and field boundaries.
Landing Gear
Like most specialised agricultural aircraft, the Thrush uses a conventional (tailwheel) undercarriage.
Advantages include:
- greater propeller clearance
- lower structural weight
- improved rough-strip performance
- simpler maintenance
- better operation from muddy farm strips
Large low-pressure tyres reduce ground pressure during operations from soft fields.
Powerplant Development
One of the strengths of the Thrush design has been its adaptability to different engines.
Early Radial Engines
Initial aircraft were powered by radial piston engines including:
- Continental engines (early production)
- Pratt & Whitney R-985 Wasp Junior
- Pratt & Whitney R-1340 Wasp
- Wright R-1300
- Wright R-1820 Cyclone
These engines delivered between 450 and 1,200 hp, depending on the model.
Turbine Era
In the late 1970s and early 1980s, Ayres pioneered turbine-powered agricultural aircraft by installing the Pratt & Whitney Canada PT6A turboprop.
Later variants used:
- PT6A-15AG
- PT6A-34AG
- PT6A-45AG
- PT6A-65AG
- Garrett TPE331 series engines on selected models
Benefits included:
- greatly improved reliability
- lower maintenance
- higher payload capability
- shorter take-off distances
- reduced vibration
- lower pilot workload
The quiet operation of the PT6-powered aircraft earned the nickname “Hush Thrush.”
Structural Design
The Thrush structure is intended for continuous commercial use, with features including:
- welded chrome-moly steel cockpit frame
- heavy-duty landing gear
- reinforced wing spars
- corrosion protection for chemical exposure
- easily removable panels for maintenance
Modern derivatives incorporate higher-life wing spars and improved corrosion-resistant coatings to extend operational life.
Production
Production has been centred in Albany, Georgia, USA throughout most of the aircraft’s history.
Ownership progression:
- Snow Aeronautical
- Aero Commander (Rockwell)
- Ayres Corporation
- Thrush Aircraft
Today, much of the fabrication, machining, welding, wing assembly and final assembly is performed in-house at the Albany facility, with engines, propellers, avionics and spray systems installed during final assembly. Every aircraft undergoes a factory test-flight programme before delivery.
Typical Specifications (Ayres S2R Turbo Thrush)
| Item | Specification |
|---|---|
| Crew | 1 |
| Length | 33 ft (10.1 m) |
| Wingspan | 47 ft 6 in (14.5 m) |
| Height | 9 ft 2 in (2.8 m) |
| Wing Area | 350 sq ft (32.5 m²) |
| Hopper Capacity | 400–500 US gal (1,514–1,893 L), depending on variant |
| Empty Weight | 3,600–4,900 lb (1,630–2,220 kg) |
| Maximum Take-off Weight | Up to 10,500 lb (4,763 kg) on high-gross variants |
| Engine | Pratt & Whitney PT6A or Garrett TPE331 (variant dependent) |
| Engine Power | 680–1,300 shp |
Typical Performance (Turbo Thrush)
| Performance | Value |
|---|---|
| Maximum Speed | 160–188 mph (139–163 kt) |
| Cruise Speed | Approximately 150 mph (130 kt) at 55% power |
| Working Speed | 90–150 mph (78–130 kt) |
| Ferry Range | Up to 1,000 miles (1,600 km), depending on fuel and variant |
| Rate of Climb | Approximately 1,500–2,000 ft/min (variant dependent) |
| Take-off Distance | Typically under 2,000 ft when lightly loaded from prepared strips |
Operational Characteristics
Operators value the Thrush for its:
- exceptionally stable low-speed handling
- high payload capacity
- forgiving stall behaviour
- rugged landing gear
- straightforward maintenance
- excellent pilot visibility
- ability to operate from rough, unsealed strips
These characteristics have made it particularly popular for broadacre farming, forestry operations, mosquito control and aerial firefighting.
Legacy
The Thrush’s greatest achievement is the longevity of its basic design. Over nearly seventy years, the airframe has successfully evolved from a 450 hp radial-engine crop duster into a family of 1,300 shp turbine-powered agricultural aircraft. Its influence extends beyond its own production line; design elements from the S-2 were incorporated into aircraft such as the Polish PZL M-18 Dromader, and its emphasis on purpose-built agricultural engineering helped define the standards for modern aerial application aircraft. Today, the Thrush remains one of the principal competitors to the Air Tractor family in the global agricultural aviation market.