STD-2044 - Lycoming™ Self Locking Nut .250-20

STD-2044 – Lycoming™ Self Locking Nut .250-20

Available now on the Airparts.aero Marketplace.

Overview

The Lycoming STD-2044 is a genuine OEM, self-locking hexagon nut, an essential piece of hardware for securing numerous components on Lycoming aircraft engines. This fastener is manufactured to the AN365-420A military standard and is commonly referred to as a "nyloc" nut. It is engineered to resist loosening under the constant, high-frequency vibration of a piston engine. Featuring a captive nylon locking collar and fabricated from cadmium-plated steel, the STD-2044 is the factory-specified nut for a multitude of general-purpose, firewall-forward applications.

Key Features

• Nylon Insert Locking Mechanism: The defining feature is an integrated nylon (polyamide) collar at the top of the nut. As a bolt or stud is threaded through, the nylon insert is elastically deformed, creating a powerful, uniform frictional grip on the threads that provides prevailing torque and prevents loosening.
• Vibration Resistance: The prevailing torque created by the nylon insert makes this nut exceptionally resistant to loosening from engine vibration, eliminating the need for secondary locking devices like lock washers in many applications.
• High-Strength Steel Construction: Fabricated from a high-quality carbon steel alloy, providing the tensile strength required to properly secure engine accessories and non-structural components.
• Corrosion-Resistant Plating: Plated with a durable cadmium finish to provide excellent protection against corrosion in the harsh, high-temperature environment of the engine compartment.
• Genuine Lycoming OEM Part: As a genuine factory part, it guarantees conformance to Lycoming's stringent material and performance standards. It is dimensionally and functionally identical to the AN365-420A standard nut.

Technical Specifications

• Lycoming Part Number: STD-2044 or STD2044
• Military Standard Equivalent: AN365-420A
• Component Type: Self-Locking Nut with Nylon Insert
• Material: Carbon Steel
• Finish: Cadmium Plated
• Locking Element: Nylon (Polyamide) Insert
• Thread Specification: 1/4-20 UNC-2B
  • Nominal Diameter: 1/4 inch (0.250 inches)
  • Threads Per Inch: 20 (Coarse Thread)
• Wrench Size: 7/16 inch
• Maximum Operating Temperature: 250°F (121°C)

Aircraft Compatibility

The Lycoming STD-2044 is a universal hardware component used in numerous locations on nearly every engine that Lycoming produces.

• Common Lycoming Engine Series:
  • O-235, O-320, IO-320
  • O-360, IO-360, AIO-360, AEIO-360
  • O-540, IO-540, TIO-540, AEIO-540
  • IO-720
• Common Applications on Engine:
  • Rocker Cover / Valve Cover Fastener
  • Securing engine baffles and baffle seals.
  • Mounting various lightweight accessories, brackets, and line clamps.

Applications

The STD-2044 is the workhorse fastener for creating secure, vibration-proof bolted joints on the engine:

• General-Purpose Engine Fastening: The standard locknut for the vast majority of non-structural and accessory attachments on Lycoming engines where temperatures do not exceed 250°F.
• Serviceable Joints: Allows for fasteners to be removed and reinstalled for maintenance (e.g., adjusting valves) while still providing a reliable locking action upon re-torquing (subject to inspection).

Why Choose STD-2044?

A fastener that has loosened due to engine vibration can lead to oil leaks, baffle cracking, or the failure of a critical accessory. The Lycoming STD-2044 provides a simple, lightweight, and highly effective solution to this problem. Using a genuine Lycoming OEM-specified nut ensures that the part has the certified material strength, thread quality, and correct prevailing torque characteristics to function as a reliable locking device. Substituting with non-certified commercial-grade locknuts is strictly prohibited in aviation as they lack the rigorous quality control and traceability required for flight-critical applications.

Order Your Lycoming STD-2044 Nuts Now

Stock your shop with the most common and reliable flight-certified locknut for Lycoming engines. Visit Airparts.aero to order your STD-2044 self-locking nuts today.

The STD-2044 self-locking nut functions by creating "prevailing torque." This is a measured resistance to rotation that exists even when the nut is not seated against a surface. The locking action is created as the male threads of the bolt or stud engage the smaller-diameter nylon ring, which elastically deforms and creates a 360-degree frictional grip. This constant pressure on the threads prevents the nut from moving relative to the bolt, even when subjected to intense engine vibration. The 250°F temperature limit is critical; above this temperature, the nylon insert will soften, lose its elasticity, and its locking ability will be significantly reduced or eliminated. For applications exceeding this temperature, an all-metal high-temperature locknut (such as an AN364 / MS21042) must be used.

Note: This is a flight-critical component. It must be tightened using a calibrated torque wrench to the value specified in the applicable maintenance manual. While reusable, the nut must be discarded if it can be run down to the seating surface by hand, as this indicates the nylon locking element has lost its effectiveness.
NUT, 1/4-20 self-locking

Fits the following engine models:
Lycoming™

1. IO-360-A1B6
2. TO-360     (A1A6D, C1A6D, F1A6D)
3. HIO-360-G1A
4. LTO-360-A1A6D
5. TIO-360     (A1B, C1A6D)
6. AEIO-360-A1B6
7. IO-540-AC1A5
8. TIO-540     (A1C, A2C, C1A, E1A, G1A, H1A, J2BD, K1AD, R2AD, T2AD, V2AD, W2A, AA1AD, AB1AD, AB1BD, AE2A, AF1A, AF1B, AG1A, AJ1A, AK1A)
9. LTIO-540     (F2BD, J2B, J2BD, K1AD, V2AD, W2A)
10. TIO-541     (E1A4, E1B4, E1C4, E1D4)
11. TIGO-541     (D1A, D1B, E1A, G1AD)
12. IO-720      (C1B, C1BD)

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