Ayres/Thrush S2R Thrush

The Ayres/Thrush S2R is the archetypal American agricultural aircraft — a rugged, single-seat, low-wing turboprop purpose-built for aerial application of fertilizers, herbicides, insecticides, and seed. Originally designed by Leland Snow as the Snow S-2 in 1956, the type has been continuously refined and produced for nearly 70 years under four successive owners: Snow Aeronautical (Olney, TX), Rockwell-Standard/Aero Commander (as the Thrush Commander), Ayres Corporation (Albany, GA, from November 1977), and since 2003 Thrush Aircraft Inc. / Thrush Aircraft LLC (still in Albany).

It competes head-to-head with the air-tractor AT-series and is found wherever row crops are grown at scale — the American South, the Mississippi Delta, Argentina, Brazil, Australia, Eastern Europe, and Sub-Saharan Africa. Over 2,000 airframes have been built across all variants. Unlike the smaller piper-pawnee (a 150–235 HP piston trainer-scale ag plane), the Thrush is a serious commercial platform carrying a 500 US gallon hopper and typically flown by full-time ag operators earning revenue by the acre.

Thrush Aircraft Inc. filed Chapter 11 bankruptcy on September 5, 2019 after years of sluggish orders and cash flow trouble. HHM Aircraft Financing purchased the assets on November 4, 2019 and reorganized the business as Thrush Aircraft, LLC under CEO Mark McDonald, resuming deliveries in 2020. The current lineup centers on the 510P2/510P2+ (PT6A-34AG, 750 SHP) and the 710P (PT6A-65AG, 1,300 SHP), with an emerging firefighting/SEAT (single-engine air tanker) market alongside traditional ag work.

Most variants differ only forward of the firewall. The welded 4130 steel-tube fuselage, aluminum semi-monocoque tailcone, and constant-chord low wing with integral hopper aft of the firewall are common to all models. The single-place cockpit sits high on the fuselage spine for visibility over the hopper and nose; two-place trainer versions exist but are uncommon.

Book cruise of 130 KIAS at gross is mostly academic — the Thrush spends its working life at 120–140 KTAS between the field and the loading strip, and at 90–100 KIAS in the spray run 10 feet off the crop. Fuel burn at working power is 38–46 GPH on the 750 SHP PT6A-34AG, rising to 55–65 GPH on the -65AG in the 710P. Range with full fuel and an empty hopper is about 400 nm; with a full hopper it is dictated by the loading strip, not fuel.

Rate of climb at max gross (10,500 lb) off a hot loading strip is the most painful number — expect 600–800 fpm after flap retraction, less on a density-altitude day. Takeoff roll with a full 510 gallon hopper (roughly 4,300 lb of chemical) is 1,200–1,800 ft depending on surface. The airplane is designed to be flown well outside the normal GA envelope: steep climbing turns at 80 kt with 4,000 lb of chemical, 60-degree banks at the end of every row, thousands of cycles per season. The -34AG and -65AG are agricultural-rated variants of the PT6 with higher TBOs and lower ITT margins than commuter PT6s, reflecting the dusty environment.

Unlike travel GA, the Thrush's "payload-range" dynamic is ferry-vs-working, not seats-vs-fuel:

• Ferry mission (empty hopper, full fuel): 228 gal × 44 GPH ≈ 5 hours, ~600 nm still air, ~4,500 lb useful load remaining after fuel. More than enough to reposition across several states.
• Typical working loadout (full 510 gal hopper ≈ 4,300 lb of water-based chemical, ~40 gal fuel for a 45-minute mission): Takeoff at or slightly over 10,500 lb gross; hopper empties on the first swath pass, and the airplane becomes a 6,500 lb empty-ferry aircraft for the return to the loading strip. This cycle repeats 40–80 times per day in peak season.
• Maximum dry load (seed, fertilizer): Dry product density allows higher weight-for-volume, and many operators will fill to gross weight (~5,600 lb of product) even though the 510 gallon hopper volume isn't fully used.
• Hot / high / heavy: Loading strips at 3,000 ft MSL on a 95°F day reduce useful chemical load by 500–1,000 lb on the 750 SHP -34AG. The 1,300 SHP 710P eats these conditions much more easily, which is why it dominates the high-density-altitude Western and African markets.

Related pages: air-tractor (primary competitor), piper-pawnee (entry-level piston ag plane), cargo-hauling (mission definition), valuation-methodology, insurance-underwriting, maintenance-ecosystem.

• Cargo hauling (9/10): This is what the Thrush does — 4,200+ lb of liquid or dry cargo in a 510 gal hopper (710 gal on the 710P), lifted out of short, rough strips. No other certified GA airplane class is more productive per acre.
• Surveying (3/10): Not purpose-built for it, but SEAT (Single-Engine Air Tanker) operators fly Thrushes on fire patrol and retardant drops; the high pilot station gives excellent downward visibility.
• Backcountry (4/10): Outstanding unimproved-strip performance empty, but single-seat, no cargo volume aft of the hopper, and $1M+ capital cost make it completely impractical as a recreational bush plane.
• Cross-country (2/10): 130 KTAS and 400 nm range at 44 GPH burning Jet-A is fine for repositioning, terrible as a traveling machine.
• Training / Aerobatics / Local fun / Business travel (1/10): Single-seat restricted-category commercial workhorse; none of these missions apply.

See cargo-hauling for how the Thrush scores against the air-tractor AT-502/AT-802 lineup.

Ag airplanes live in a completely different avionics world than travel GA. A modern 510P2+ panel typically includes:

• Satloc / AgNav / Hemisphere GPS guidance — Differential/SBAS GPS with lightbar guidance; the primary "nav" on an ag airplane, driving swath guidance and variable-rate application.
• Flow controllers (Satloc Bantam, Hemisphere IntelliFlow) — Close the loop between GPS groundspeed and spray pump output for constant gal/acre.
• Basic round-gauge or Garmin G3X panel — Engine instruments, airspeed, altimeter; most ag operations are day VFR below 500 ft AGL, so IFR capability is largely absent and the platform is not certified IFR.
• Garmin GTR 225 / GNC 255 comm/nav and a basic transponder — the minimum for controlled-airspace transits.
• Appareo Stratus ESG / Garmin GTX 345 ADS-B Out — required in rule airspace.

Night/IFR ag operations exist but are specialist. Firefighting variants add Wulfsberg FM radios for interagency comms and sometimes FLIR.

• Goering Conversion (Goering Aircraft, Inc. — Hobbs, NM): The dominant turbine conversion STC for older R-1340 and R-1820 piston Thrushes, installing a PT6A-34 or -45. A Goering-converted airframe typically commands $150K–$300K over an otherwise equivalent piston machine.
• Hopper upgrades from 400 → 510 → 660 → 710 gallons on appropriate airframes.
• Gross weight increase STCs on T34/T45 airframes, usually 10,500 → 11,000+ lb under restricted category.
• Dispersal systems: CP-11TT nozzles, Micronair AU-5000 rotary atomizers, Transland dry spreaders, SATLOC/AgNav smart systems.
• Firefighting conversion (Fire Boss-style but single-fuselage tank): retardant gates, foam injection, external long-range tanks.
• Night vision goggle (NVG) compatibility for SEAT operators.

• Factory support: Thrush Aircraft LLC in Albany, GA provides parts, structural components, and tech support; parts availability is generally good for current production variants. Older Rockwell-era Thrush Commander 600 and out-of-production R-1820 "Bull Thrush" parts are harder to source and often come from breakers.
• A&P familiarity: Specialist. Ag maintenance shops (Covington Aircraft, Queen Bee Air Specialties, Farm Air Inc., Aero-Mod, Southeastern Aircraft Parts) dominate the support network. A general-aviation A&P without ag or PT6 experience is not a viable maintainer for a working Thrush.
• Engine support: P&WC dealer network (Covington Aircraft in Oklahoma is the leading PT6A-34AG/-65AG overhaul facility in the US), plus GE Aerospace for the H80 in 510G airframes.
• Annual operating cost (owner-operator, 400 hours/year): Roughly $80K–$140K all-in including fuel, insurance, hangar, engine reserves, airframe maintenance, and annual inspection. Hot sections every 1,800 hours are a significant scheduled expense.
• Big-ticket items: Wing spar life extension or replacement ($150K+), PT6 overhaul ($400K–$500K), prop overhaul ($25K–$40K), hopper system refurbishment.

See maintenance-ecosystem for the ag-turbine support supply chain.

Thrush valuation is driven by four things: (1) turbine time since overhaul or hot section, (2) airframe time and spar life, (3) hopper size and dispersal system, (4) guidance/flow control package vintage.

Rough market tiers (2025–2026):

• 1970s–early 80s Ayres S2R-600/R-1340 piston, original radial: $90K–$180K. A dying segment — avgas availability and R-1340 parts drive operators to convert.
• Goering-converted S2R-T34 on an older airframe: $250K–$450K depending on TBO status.
• 1990s–2000s Ayres S2R-T34 / 510P: $400K–$750K, heavily dependent on engine reserve and guidance upgrades.
• 2010s Thrush 510P / 510G: $800K–$1.2M.
• Current 510P2+ / 710P new factory: $1.35M (510P2+) to $1.95M+ (710P) as of 2024.

Engine reserve dominates pricing: a mid-time PT6A-34AG with 1,800 hours since overhaul on a 3,600-hour TBO represents ~$200K of deferred cost against a ~$425K overhaul, and buyers bid accordingly. See valuation-methodology for the overhaul-reserve discounting framework applied to turbine ag singles.

The Thrush is a restricted-category commercial airplane flown hard, and its AD history reflects that:

• Wing spar lower cap inspections — recurring AD on S2R and S2R-T series wings for fatigue cracks at the main spar lower cap, particularly on airframes with high spray-run hours. Life-limited spar cap replacements are a six-figure event.
• Aft fuselage / empennage attachment fittings — AD-driven inspections for corrosion and cracking from chemical exposure.
• Landing gear leg attach fittings — inspections driven by the harsh operating environment (rough strips, hard landings, heavy loads).
• PT6A-34AG / -65AG compressor section — dust erosion is the dominant maintenance driver; compressor washes are daily/weekly procedures, and hot section inspections come up on calendar, not just hours.
• Flight control cable fraying at seal grommets from ag chemical wicking.
• Hopper sump/plumbing corrosion — constant from caustic liquid chemistries.

Pre-buy red flags: hidden corrosion under the hopper, cracked engine mount tubes behind the firewall, spar cap pit corrosion, undocumented gear-up or wire-strike repairs (wire strikes are common in ag work), and PT6 compressor blades with erosion beyond service limits.

Agricultural aviation is its own insurance market — see insurance-underwriting for category definitions. Key facts:

• Hull insurance: $18K–$40K/year on a $600K–$1.2M Thrush, a ratio of roughly 2–4% of hull value (vs. ~1–1.5% for travel GA). The high rate reflects the real risk: wire strikes, ditch impacts, engine FOD from dirt strips, and the 50+ low-altitude turnarounds per day.
• Liability: Harder to place than hull. Chemical drift claims, crop damage, and third-party property damage drive aggregate limits up; $1M smooth is typical, higher is available but expensive.
• Underwriting focus: Pilot's ag experience is paramount. A 10,000-hour ag pilot pays dramatically less than a 500-hour pilot transitioning in, regardless of total time. Carriers want season-count, make/model time, PT6 time, and annual recurrent training (typically NAAA PAASS or Ag Flight School).
• Primary markets: AIG, Falcon, Old Republic Aerospace, Berkley Aviation, specialty brokers like Aviation Specialty Insurance (ASI), USAIG.

Low-time ag pilots often cannot obtain insurance on a Thrush at any price and must build hours in a smaller Pawnee or Ag-Cat first.