40-279A – Cleveland Wheel Assembly for Air Tractor and Thrush Aircraft 🛑
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Overview
The Cleveland 40-279A Main Wheel Assembly is a heavy-duty, divided-type main landing gear wheel certified under FAA-TSO-C26c for demanding applications on agricultural and specialized utility aircraft, notably the Air Tractor AT-802 and Thrush (T660P) series. The wheel assembly is a flight-critical component designed to support the majority of the aircraft's weight during ground operations and to transmit the stopping forces generated by the mating brake assembly to the ground. The designation "A" in the part number signifies an improved design variant of the original 40-279, often incorporating enhancements such as improved hubcap, seals, and corrosion resistance per applicable Service Bulletins (e.g., SB7067 and SB7082).
This main wheel features a divided design, consisting of an inner and outer wheel half fastened together by multiple tie bolts. This construction facilitates easier tire mounting and maintenance. The design is engineered to interface seamlessly with a matched hydraulic brake assembly (specifically Cleveland 30-210A / 30-210C) and accommodates a high-ply-rating, tubeless tire, ensuring reliability under the high-weight, high-cycle operational profile typical of agricultural spray applications.
Key Features
Divided Wheel Design: Composed of precision-cast or forged aluminum/magnesium inner and outer halves, secured by high-strength tie bolts, enabling straightforward field servicing of tires and tubes.
High Load Capacity: Engineered to meet the extreme static and dynamic load requirements of heavy agricultural aircraft landing and ground maneuvering.
Tapered Roller Bearings: Utilizes two heavy-duty tapered roller bearings seated in shrink-fitted cups within the hub, optimized for high load capacity and smooth rotation.
Tubeless Compatibility: Certified for use with a tubeless tire configuration, reducing complexity and the potential for tube-related failures.
Improved Sealing: Incorporates modern molded grease seals and a robust hubcap to provide superior protection for the tapered roller bearings against water, dust, and corrosive environmental agents, maximizing bearing life.
Technical Specifications
Part Number: 40-279A
Component Type: Main Wheel Assembly (Divided Type, External Interface)
OEM Manufacturer: Cleveland Wheel & Brake Systems (A Signia Aerospace Company)
Certification Type: FAA-TSO-C26c
Rim Size: 11.00-12
Compatible Tire Size: 11.00-12
Ply Rating: 10.0 Ply (Minimum specified rating)
Standard Brake Disc P/N: 164-23002
Matched Brake Assembly P/N: 30-210A / 30-210C (Must be used with the specified brake assembly)
Material: Aluminum or Magnesium Castings/Forgings (Specific material confirmed by CMM).
Bearing Type: Tapered Roller Bearings (P/N 214-09200 Cone, 214-39412 Cup).
Internal Components: Includes Inner Wheel Half Assembly (P/N 161-13301) and Outer Wheel Half Assembly (P/N 162-12401).
Aircraft Compatibility
Primary Models:
Air Tractor: AT-802 (Main Landing Gear Wheel Assembly)
Thrush: T660P Series
System Integration: Forms the foundational rolling element of the Main Landing Gear System, interfacing directly with the brake assembly and axle.
Verification Note: The Aircraft Manufacturer's Approved Parts Catalog and the Cleveland Component Maintenance Manual (CMM) are the definitive and final authority for part applicability and compatibility.
Applications Section
The 40-279A Wheel Assembly is essential for operational performance in:
Agricultural/Utility Ground Operations: Withstanding repeated, high-impact landings on rough or unprepared airfields characteristic of aerial application work.
Braking Energy Management: Providing the secure interface for the brake disc to absorb the high kinetic energy generated during deceleration and rejected takeoffs (RTO).
Load Bearing: Distributing the substantial static weight of the fully fueled and loaded aircraft and managing dynamic lateral loads during taxi and turns.
Why Choose the 40-279A Cleveland Wheel Assembly?
The wheel assembly is a fatigue-critical, life-safety component designed to absorb cyclic loads in a corrosive environment (often fertilizers and pesticides in this application). Choosing the Cleveland 40-279A certified wheel guarantees the validated structural integrity and metallurgical consistency necessary to prevent catastrophic in-flight or on-ground failure. Uncertified or improperly maintained wheels are susceptible to fatigue cracking (particularly around the tie bolt bosses or bead seats) and corrosion-induced structural failure. This TSO-approved assembly ensures the precise bearing fits and material properties that prevent premature wear, guaranteeing conformity to the highest safety standards for heavy-duty aircraft operations.
The structural integrity of the 40-279A is ensured by the careful design of the tie bolt interface. The tie bolts are subjected to a high tensile preload during assembly, which provides the necessary clamping force to contain the internal pneumatic pressure of the tire. This preload must be sufficient to prevent relative motion between the inner and outer wheel halves when subjected to bending moments and lateral loads during landing and taxiing. Failure to achieve the correct preload results in fretting and eventual fatigue failure around the fastener holes. The wheel half material (e.g., aluminum alloy) is selected for its high specific strength (strength-to-weight ratio), and the design incorporates features like tapered bearing seats to distribute the immense radial loads evenly from the axle into the wheel hub.
Note: The 40-279A Wheel Assembly is a life-limited, flight-critical component. It must be disassembled, cleaned, and inspected per the Cleveland Component Maintenance Manual (CMM) at regular intervals (usually at tire change or major inspection). Critical checks include dye penetrant inspection for fatigue cracks and precise dimensional measurement of the bead seats and bearing bores. The specified tie bolt torque is paramount and must be strictly followed during reassembly. Installation and inspection must be performed and certified by a licensed A&P mechanic or specialized wheel technician in strict accordance with the CMM and applicable Service Bulletins.
Documentation
Authoritative documentation for this TSO component includes:
Cleveland Wheel and Brake Systems Component Maintenance Manual (CMM) for 40-279A.
Cleveland Service Bulletin SB7067 & SB7082: Details the upgrade from the 40-279 to the improved 40-279A standard.
FAA Technical Standard Order (TSO) C26c: The regulatory standard governing the design and performance requirements.