MS15001-3 - Aerospace 45 Degree Grease Fitting

MS15001-3 – Aerospace 45-Degree Lubrication (Grease) Fitting

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The MS15001-3 is a high-strength, corrosion-resistant 45-degree angle grease fitting (also known as a Zerk fitting) manufactured to Military Standard (MS) requirements. This component is a critical interface in aircraft maintenance, designed to provide a secure, leak-proof injection point for pressurized lubricants into bearings, bushings, and pivot points. The 45-degree angled head is specifically engineered to provide access to lubrication points in confined spaces or recessed areas where a straight fitting would be inaccessible by a standard grease gun coupler.

Fabricated from high-grade steel and protected by a robust cadmium-plated finish, the MS15001-3 features a 1/8-27 NPTF (National Pipe Thread Fuel) tapered pipe thread for a self-sealing, vibration-resistant fit into the airframe or component housing. At its core is a precision-engineered spring-loaded ball check valve. This valve remains normally closed to prevent the ingress of dirt, moisture, and de-icing fluids into the sensitive bearing cavity, only opening under the hydraulic pressure of a grease gun during servicing. For the A&P mechanic, the MS15001-3 is a staple for maintaining the operational life and friction-free movement of flight control linkages, landing gear pivots, and engine accessory drives.

This part has been supersceded by AS15001-3P

Key Features

• Supersceded by Part Number: AS15001-3P

• 45-Degree Angled Head: Provides superior accessibility in tight clearance applications, allowing for efficient maintenance without disassembly of surrounding hardware.

• Spring-Loaded Ball Check: High-precision internal check valve prevents lubricant backflow and seals out environmental contaminants to prevent bearing abrasive wear.

• NPTF Tapered Threads: Features 1/8-27 NPTF dryseal threads that provide a high-pressure seal through thread deformation, critical for high-vibration aerospace environments.

• High-Strength Carbon Steel: Manufactured to withstand high injection pressures and mechanical stress during installation and servicing.

• Cadmium II Plating: Finished with yellow dichromate cadmium (per QQ-P-416) for maximum galvanic corrosion protection and enhanced lubrication of the threads.

Technical Specifications

• Part Number: MS15001-3

• Component Type: 45-Degree Angle Lubrication Fitting

• Material: Carbon Steel

• Finish: Cadmium Plate, Type II (Yellow), Class 2

• Thread Size: 1/8-27 NPTF (Tapered Pipe Thread)

• Angle: 45 Degrees

• Overall Length: 0.88 inches (Nominal)

• Shank Length: 0.19 inches

• Wrenching Hex: 7/16 inch

• Governing Specifications: MS15001, MIL-F-3541

• Certification: FAA-PMA / MIL-SPEC Standard Hardware

Aircraft Compatibility

• General Aviation: Cessna 100/200/300/400 series (landing gear and control hinges).

• Turboprop & Regional: Beechcraft King Air and Pilatus PC-12 (flap tracks and torque tubes).

• Business Jets: Gulfstream and Learjet (nose gear steering and door mechanisms).

• Helicopters: Bell and Robinson (rotor head and tail rotor pitch change linkages).

• Note: MS15001-3 is a universal aerospace standard part. Always verify the specific fitting angle required in the aircraft's Illustrated Parts Catalog (IPC).

Applications

• Landing Gear Assemblies: Lubricating trunnions, torque links, and axle pivots.

• Flight Control Linkages: Providing a service point for aileron, elevator, and rudder hinges.

• Propeller Hubs: Used on various constant-speed propeller assemblies for blade pitch bearings.

• Engine Accessories: Lubrication of wastegates and cooling fan bearings.

Why Choose MS15001-3?

In the aerospace environment, the failure of a $5 part can lead to the seizure of a $50,000 component. Choosing a genuine MS15001-3 ensures that the internal spring tension and ball seat geometry are designed to withstand the high-pressure pulses of pneumatic grease guns without "blowing out." Commercial-grade fittings often lack the corrosion resistance of the MS-spec cadmium plating, leading to "frozen" fittings that snap during removal, necessitating costly extraction and thread repair. By adhering to the MS15001 standard, operators ensure long-term ease of maintenance and the preservation of critical bearing surfaces.

The MS15001-3 operates on the principle of Hydraulic Check-Valve Logic combined with Interference Fit Thread Sealing. The 1/8-27 NPTF (Dryseal) thread is engineered with a taper that facilitates a metal-to-metal seal by crushing the thread crests into the roots of the mating part. This eliminates the need for Teflon tape or sealant, which could contaminate the lubricant.

From a materials standpoint, the Ball Check Valve utilizes a high-carbon steel ball and a corrosion-resistant spring. The spring rate is carefully calibrated to ensure the valve reseats instantly when the grease gun coupler is removed, maintaining a Hermetic Seal against atmospheric pressure. The 45-degree angle is achieved through precision machining of the fitting body, ensuring that the Moment of Inertia during wrenching does not lead to neck-down failure at the thread-to-body transition. This design ensures that the fitting can handle injection pressures often exceeding 5,000 PSI without structural deformation.

Note: The MS15001-3 is a critical maintenance interface. Prior to servicing, the fitting head must be wiped clean to prevent the injection of abrasive contaminants into the bearing. Over-torquing during installation can crack the component housing or strip the tapered threads. Installation must be performed by a certified A&P mechanic in accordance with AC 43.13-1B and the aircraft’s scheduled maintenance program.

Documentation

• FAA AC 43.13-1B - Chapter 9: Aircraft Systems and Components (Lubrication)

• SAE AS15001 (Standard for Lubrication Fittings)

Applicable Aircraft

• 1900 Airliner
• 1900C Airliner
• 1900D Airliner
• Baron Series B55, E55, 58 or G58
• Beechjet 400/400A
• Bonanza 36
• Bonanza F33, G33, F33A or F33C
• King Air 100
• King Air 350 Fusion
• King Air 350C FM-36 & On
• King Air 350C Fusion
• King Air 350i
• King Air 360
• King Air 360C
• King Air B200, B200T, B200C or B200CT
• King Air B200GT
• King Air B200GT Fusion or B200CGT Fusion
• King Air C90, C90A, C90GT or E90
• King Air C90GTi
• King Air C90GTx
• King Air C90GTx Fusion
• Premier Model 390
• Super King Air 350
• Super King Air 350C FM-1 to FM-35
• 747-400ERF
• CRJ-900LR
• 767-300ER
• 717
• Citation Bravo
• 757
• 777-300ER
• 737NG-800BJ
• 737-700
• 737-900
• 737-8200
• 757-200PF
• BBJ 737-700
• 737-100
• 767-200EM
• 737-700C
• 767-200
• 777-300
• 777-200F
• 767-200SF
• 777
• 737-10
• 737-800
• 737NG-600
• 767-400
• 747-400
• CRJ-702ER
• 747-8
• CRJ-702
• 747
• 737NG-700
• 737NG-700C
• 757-200
• 737-600
• 737-500
• 767-200ER
• 737-400
• BBJ 737-800
• 767-300F
• 767-200EREM
• 737NG-800
• 757-300EM
• 767-300
• 777-200LR
• 737 MAX
• 757-200PCF
• 737NG-700BJ
• 767-200ERSF
• 737-7
• 757-200PC
• 737NG-800BCF
• 737-300
• 767
• 737NG-800MMA
• 737 MAX 8
• 737NG-AEW&C
• 737-9
• 737-8
• 737-900ER
• 777-200ER
• 737-200
• 737 MAX 9
• 707
• CRJ-700ER
• 747-400F
• 747-8F
• 777-200
• 767-200ERT
• 767-400ER
• 767-300EREM
• 757-200EM
• 747-400PC
• 737NG-900
• 757-300
• CRJ-701ER
• CRJ-701
• CRJ-900ER
• 767-300BCF

List not comprehensive, may be applicable on other models.