12NB-108 – Textron OEM Internal Wrenching Nut
Available now on the Airparts.aero Marketplace.
Overview
The Textron 12NB-108 is a genuine OEM, flight-critical, internal wrenching nut engineered for securing the engine mounts on the Beechcraft King Air and 1900 series of aircraft. This is a high-performance, proprietary fastener designed specifically for high-torque, limited-access applications where a standard external hex nut cannot be used or cannot be reliably torqued. Fabricated from ultra-high-strength steel alloy, the 12NB-108 provides the immense clamping force necessary to secure the engine mount bolts, ensuring the powerplant remains rigidly and safely attached to the airframe.
Key Features
- Internal Wrenching Design: Features a broached, internal socket (typically a 12-point or double-hexagon configuration) that allows for the application of extremely high torque via an internal drive tool. This design is essential for achieving the required bolt preload in space-constrained areas around the engine mount structure.
- Ultra-High-Strength Steel Alloy: Manufactured from a specific, high-tensile strength steel alloy and heat-treated to achieve the exceptional strength required to withstand the immense static and dynamic loads of the engine mount joint without thread stripping or failure.
- Compact, High-Strength Profile: The internal drive allows for a smaller outer diameter compared to an external hex nut of equivalent strength. This provides the necessary clearance from surrounding structures while maximizing the strength of the fastener.
- Superior Corrosion Protection: Coated with a robust, multi-layer corrosion-resistant plating to protect the high-strength steel from the harsh environment of the engine nacelle.
- Genuine Textron OEM Part: As the genuine factory component, it guarantees conformance to the exact material specifications, heat treatment, and dimensional tolerances required by the original Type Certificate. For a fastener this critical, there is no substitute.
Technical Specifications
- Part Number: 12NB-108
- Alternate Part Number: 12NB108
- Component Type: Internal Wrenching Structural Nut
- Primary Application: Engine Mount Attachment
- Material: Ultra-High-Strength, Heat-Treated Steel Alloy
- Finish: High-Performance Corrosion-Resistant Plating
- Drive Style: Internal Hex or Double Hex Socket
- Thread Specification: Proprietary (Must be verified against the mating bolt and maintenance manual).
- Certification: FAA Production Approval with full material and process traceability.
Aircraft Compatibility
The 12NB-108 is the specified OEM nut for the engine mounting system on some of the world's most successful turboprop aircraft.
- Primary Aircraft Models:
- Beechcraft King Air: 90, A90, B90, C90, E90 Series
- Beechcraft King Air: 100, A100, B100 Series
- Beechcraft Super King Air: 200, B200 Series
- Beechcraft 1900/1900C/1900D Airliner
Applications
The 12NB-108 has a singular, profoundly important application:
- Engine Mount Fastening: Used in conjunction with the corresponding high-strength bolts to secure the engine mount assembly to the firewall and nacelle structure. This joint bears the entire weight, thrust, and torque of the engine.
- Mandatory Inspection & Replacement: This hardware must be inspected for condition and proper torque at specified intervals and is often a mandatory replacement item during engine removal or after a hard landing event, per the maintenance manual.
Why Choose 12NB-108?
The engine mount connection is one of the most critical structural joints on any aircraft. A failure here would be catastrophic. The 12NB-108 nut is not just a piece of hardware; it is an engineered solution to the problem of achieving extremely high clamp loads in a confined space. Using a genuine Textron Aviation OEM part is the only way to guarantee the fastener has the certified material strength and precise manufacturing tolerances to be torqued to its specified value and safely carry the immense loads of the engine.
Order Your 12NB-108 Engine Mount Nuts Now
Ensure the integrity of your aircraft's most critical structural joint with genuine, factory-certified hardware. Visit Airparts.aero to order your Textron Aviation 12NB-108 engine mount nuts today.
The internal wrenching design of the 12NB-108 nut provides a significant mechanical advantage. By engaging the nut internally, the turning force is applied evenly across multiple points within the body of the nut itself, rather than on external corners. This allows for the transmission of much higher torque values without the risk of "rounding off" the fastener, which is a common failure point with standard hex nuts under extreme torque. This high, accurately applied torque is necessary to stretch the massive engine mount bolt to its specified preload, creating a rigid, clamped joint that resists the shear, tensile, and torsional forces generated by a powerful turboprop engine like the Pratt & Whitney Canada PT6A.
Note: This is a flight-critical structural component, often with a specific life limit or mandatory replacement schedule. It must only be used in the application specified by the Textron Aviation maintenance manual. Installation requires the use of a specific internal drive tool and a calibrated, high-range torque wrench to apply the precise torque value specified in the manual.
Applicable Aircraft
- Bonanza 36
