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139-20000 – Cleveland/Parker Brake Piston Boot (30-170 Series)
Available now on the Airparts.aero Marketplace.
The Cleveland (Parker-Hannifin) 139-20000 is a critical environmental seal engineered for the 30-170 series aircraft brake assemblies. Commonly referred to as a "dust boot" or "piston boot," this component is fabricated from a high-grade, heat-resistant elastomer designed to protect the brake piston and cylinder bore from external contaminants. In the harsh operating environment of an aircraft landing gear—where components are exposed to runway debris, de-icing chemicals, and intense thermal radiation during braking—the 139-20000 serves as the primary line of defense against abrasive wear and moisture ingress.
Specifically designed for the 30-170 caliper architecture, the boot creates a flexible, accordion-style barrier that expands and contracts with the movement of the brake piston. By preventing dust and grit from reaching the primary hydraulic O-ring seal, the 139-20000 significantly extends the service life of the brake assembly and prevents "piston sticking" or fluid leaks caused by scored cylinder walls. For the A&P mechanic, this boot is a standard replacement item during brake overhauls and lining changes, ensuring the continued reliability of the aircraft's deceleration system.
Key Features
High-Temperature Elastomer: Manufactured from specialized synthetic rubber capable of withstanding the extreme heat generated during heavy braking cycles without becoming brittle or melting.
Accordion-Fold Design: Features a flexible geometry that allows for full piston travel (from new linings to fully worn) without inducing mechanical stress on the seal.
Precision Interference Fit: Engineered to snap securely into the caliper housing and onto the piston shoulder, ensuring a gas-tight and moisture-resistant seal.
Chemical Resilience: Formulated to resist degradation when exposed to hydraulic fluids (MIL-PRF-5606 or AS5606), Skydrol (where applicable), and common aviation cleaning solvents.
Environmental Shielding: Prevents "fretting" of the piston surface by blocking salt, sand, and runway grime that can cause catastrophic O-ring failure.
Superseded by Part Number: 139-20001
Technical Specifications
Part Number: 139-20000
Manufacturer: Cleveland / Parker-Hannifin (Aircraft Wheel & Brake Division)
Component Type: Brake Piston Dust Boot
Material: High-Temperature Synthetic Elastomer
Compatible Series: Cleveland 30-170, 30-170A, and 30-170B Brake Assemblies
Color: Black
Operating Temperature: -65°F to +400°F (approximate range)
Governing Specifications: TSO-C26 (Standard for Aircraft Wheels and Brakes)
Certification: FAA-PMA / OEM Original Equipment
Aircraft Compatibility
Cessna 208/208B Caravan: Frequently used in the main gear brake assemblies.
Beechcraft King Air 90 & 200 Series: Standard equipment for many Cleveland-converted airframes.
Piper PA-42 Cheyenne: Utilized in high-performance turboprop braking systems.
Pilatus PC-6 Porter: Common in rugged, utility-field operations.
Note: Always consult the Cleveland/Parker Application Guide or your aircraft's Illustrated Parts Catalog (IPC) to verify the 139-20000 is correct for your specific brake assembly part number (e.g., 30-170).
Applications
Brake Overhaul: Mandatory replacement part during the cleaning and resealing of brake calipers.
Preventative Maintenance: Replacing "checked" or cracked boots during annual inspections to prevent future hydraulic failure.
Why Choose 139-20000?
The braking system is one of the few "single-point failure" systems during the landing phase. Choosing the genuine Cleveland 139-20000 ensures that the boot’s Elastic Modulus and Thermal Recovery rate match the engineering requirements of the piston assembly. Generic "industrial" boots may look similar but often lack the Flame Retardancy and Hydrocarbon Resistance required for aerospace use. An inferior boot that fails under heat can melt onto the piston, causing the brakes to seize or preventing the piston from retracting, leading to "brake drag," overheated rotors, and potential tire fires.
The 139-20000 functions based on the principle of Exclusion Sealing. Unlike the internal O-ring (which is a Pressure Seal), the boot is a Static-to-Dynamic Interface Protector. From a materials science perspective, the elastomer is subjected to Thermal Cycling and Oxidative Aging. The 139-20000 is specifically engineered to resist Ozone Cracking, a common failure mode in rubber components exposed to high altitudes and electrical equipment (like landing gear motors).
Furthermore, the boot prevents the formation of Stiction (Static Friction). If dust enters the gap between the piston and the housing, it acts as a wedge, increasing the breakout force required to move the piston. This results in "notchy" braking and uneven pad wear. By maintaining a clean Surface Finish on the piston OD, the 139-20000 ensures that the Hydraulic Displacement remains linear and predictable. During installation, the boot must be seated into the Retaining Groove using only approved O-ring lubricants to ensure it does not "pinch" during the first brake application.
Note: The 139-20000 is a critical safety component. Boots that show signs of tearing, softening (swelling from oil), or "checking" (cracks) must be replaced immediately. Failure to maintain a sealed boot can lead to "Piston Cocking," where debris forces the piston to tilt and seize in the bore. Installation must be performed by a certified A&P mechanic in accordance with Cleveland Maintenance Manual WMM6000.
Documentation
Parker-Hannifin Cleveland Wheel & Brake Maintenance Manual (WMM6000)
FAA AC 43.13-1B - Chapter 9: Aircraft Systems and Components (Braking Systems)
