SP90E10 – Textron Aviation OEM Split Pin (Cotter Pin)
Available now through the AirParts Aero marketplace.
Overview Section
The SP90E10 is a high-precision Split Pin (commonly known as a Cotter Pin) manufactured to Textron Aviation OEM specifications. This critical safety-locking device is used throughout the airframe to prevent the accidental loosening of castellated nuts, clevis pins, and threaded fastners subject to high vibration or rotational forces.
The SP90E10 is designed for "single-use" safety locking. Once inserted through a hole in a fastener and a slot in a castellated nut, the tines are bent back to create a mechanical stop. This ensures that even if the initial torque of the fastener is lost, the nut cannot back off the threads, maintaining the mechanical integrity of flight control linkages, landing gear assemblies, and engine components.
Key Features Section
Corrosion-Resistant Material: Typically manufactured from CRES (Stainless Steel) or high-grade Cadmium-Plated Carbon Steel to resist oxidation in harsh environments.
Precision Sizing: Sized specifically to fit the standard diameter holes found in AN and NAS series bolts (typically fits a 1/16" or 3/32" hole depending on specific dash numbering).
High Ductility: The alloy is engineered to be bent 90 to 180 degrees without fracturing, ensuring the locking tines remain secure until the next maintenance interval.
Textron OEM Certified: Meets the exact metallurgical and dimensional standards required for Cessna and Beechcraft type-certified aircraft.
Vibration Immunity: Unlike nylon locknuts, a split pin provides a physical, mechanical barrier that cannot be "shaken" loose by harmonic resonance.
Standardized Eyelet: Features a uniform "loop" head that prevents the pin from being pulled through the hole and provides a point of contact for removal tools.
Technical Specifications Section
| Specification | Detail |
| Part Number | SP90E10 |
| Manufacturer | Textron Aviation (Cessna / Beechcraft) |
| Common Name | Split Pin / Cotter Pin |
| Material | Stainless Steel (CRES) or Plated Steel |
| Nominal Diameter | Typically 1/16" (Verify per AMM) |
| Nominal Length | Typically 1" (Verify per AMM) |
| Specification | Equivalent to MS24665 or AN380 series |
| Quantity | Sold individually or in bulk kits |
Aircraft Compatibility Section
The SP90E10 is a "fleet-wide" consumable found in the maintenance logs of nearly every aircraft in the AirParts Aero inventory:
Cessna Single-Engine: Used on the axle nuts, flight control pulleys, and throttle linkages of the Cessna 152, 172, and 182.
Beechcraft King Air: Found on the landing gear drag links and engine control quadrants of the 90, 200, and 300 series.
Beechcraft Bonanza/Baron: Essential for the safety-locking of the nose-gear steering and flight control rod ends.
Textron Jets: Utilized in various secondary structures and interior mechanical assemblies of the Cessna Citation line.
Technical Applications & Safety
The SP90E10 is often used with a Castellated Nut. The slots in the nut (the "castellations") align with a hole drilled through the bolt.1 The pin is the only thing standing between a secure linkage and a total mechanical disconnect.
Safety Warning: NEVER REUSE A SPLIT PIN. Once the tines of an SP90E10 have been bent and straightened during removal, the metal undergoes "work hardening." Re-bending the pin a second time creates micro-fractures in the material, which can cause the tines to snap off under vibration, leading to a catastrophic loss of the locking feature.
The engineering value of the SP90E10 lies in its Shear Strength and Ductility Balance. The pin is designed to be soft enough to bend without specialized tools, yet strong enough to resist the shear forces exerted by a nut trying to back off a thread.
In many critical applications, the pin is installed using the "Preferred Method": one tine is bent over the end of the bolt, and the other is bent down against the flat of the nut. This ensures that the pin cannot rotate and wear out the hole over time. Choosing the genuine Textron SP90E10 through AirParts Aero ensures that the chemical composition of the metal prevents "hydrogen embrittlement," a common failure mode in low-quality hardware that causes pins to shatter under load.
Installation & Maintenance Addendum
Hole Alignment: Never over-torque or under-torque a nut to align the castellations. If the hole doesn't align, try a different nut or add a thin washer to change the alignment point.
Tine Length: If the tines are too long after installation, they should be trimmed with side-cutters to prevent them from snagging on clothing or other mechanical parts.
Tight Fit: The pin should be a "snug" fit in the hole. If the pin is loose and can "rattle," the vibration will eventually wear the pin and the hole, compromising the safety lock.