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402-938 – Piper Aircraft OEM Bolt
Available now through the AirParts Aero marketplace.
Overview Section
The 402-938 is an authentic Piper Aircraft OEM (Original Equipment Manufacturer) structural bolt. Precision-engineered for high-performance single-engine aircraft, this fastener is a critical component in the assembly of Piper PA-32R Saratoga and 301/301T series airframes.
Unlike standard hardware, Piper 400-series bolts are manufactured to rigorous aerospace tolerances to ensure structural load paths remain secure during high-stress flight maneuvers and landing cycles. The 402-938 is typically utilized in specialized airframe junctions, such as engine mount attachments, landing gear support structures, or wing-to-fuselage spar interfaces, where a standard AN (Army-Navy) bolt does not provide the exact grip or tensile requirements.
Enhanced Technical Data
| Technical Metric | Specification Data |
| Material Base | High-Strength 8740 Alloy Steel |
| Tensile Strength | 125,000 PSI (Minimum) |
| Finish | Cadmium Plated (Yellow Chromate) per QQ-P-416 |
| Nominal Length | 2.261 in |
| Envelope Dimensions | 0.44" x 0.44" x 2.44" (Overall) |
| Shank Type | Centerless Ground for Precision Fit |
| Certification | FAA-PMA / OEM Certified |
| ATA Chapter | ATA 51 (Structures) / ATA 32 (Landing Gear) |
Advanced Engineering & Structural Application
The 402-938 is engineered for Shear and Tensile Durability. In Piper retractable gear aircraft (PA-32R), fasteners are subject to significant "working" loads during gear transition and high-speed cruise.
Engineering Insight: Close-Tolerance Shank
The 402-938 often functions as a Close-Tolerance Bolt. The shank is centerless ground to a tighter diameter tolerance than standard AN hardware. This ensures an interference or "snug" fit within the mounting holes, preventing "fretting" or vibration-induced wear that can lead to hole elongation—a common issue in aging airframes.
Corrosion Protection
The Cadmium Type II finish provides an essential sacrificial barrier against galvanic corrosion, particularly when used in proximity to aluminum alloys and stainless steel brackets. This is vital for maintaining the fatigue life of primary structural joints in varied climatic environments.
Aircraft Compatibility
The 402-938 is a primary fastener for the following Piper platforms:
Piper PA-32R-301 (Saratoga SP): High-utilization structural interfaces.
Piper PA-32R-301T (Saratoga II TC): Utilized in turbocharged variants for engine/airframe mounting.
Piper PA-32RT (Lance): Compatible with specific T-tail structural assemblies (verify via IPC).
The Piper 402-938 is a mandatory replacement component for operators maintaining the structural integrity of the Saratoga and Lance fleet. When your Aircraft Maintenance Manual (AMM) calls for a specialized Piper 400-series fastener, substituting with standard AN hardware can lead to improper grip lengths and compromised shear strength. This OEM bolt ensures that your flight controls, landing gear, or engine mounts remain secured to factory specifications. Trust the precision of genuine Piper hardware to protect your airframe's long-term airworthiness and resale value.
Installation & Maintenance Addendum
Grip Length Verification: Ensure the unthreaded shank (grip) of the 402-938 extends through the entire thickness of the material stack-up. No threads should be bearing against the internal walls of the mounting holes.
Torque Procedures: Always follow the torque values specified in the Piper PA-32R Maintenance Manual. Use a calibrated torque wrench and account for the "drag torque" of self-locking nuts if used.
Hole Inspection: Before installing a new 402-938, inspect the bore for signs of "ovalling." If the hole is enlarged, consult the Structural Repair Manual (SRM) for potential oversize fastener requirements.
