Aerospace Thread-Lok Ground Service Equipment Quick-Disconnect Couplings | Parker Stratoflex


Parker Aerospace’s Thread-Lok ground service equipment (GSE) quick disconnect (QD) couplings are a proven solution for fluid conveyance systems that provide the robust connection for ground service equipment to the aircraft flight systems. The Thread-Lok QD is used in a wide range of pressure and temperature applications.

Thread-Lok GSE QD uses the same high-performance internal-valve design from the IndiLok, SlideLok, and Thread-Lok QDs, and provides a highly reliable and robust positive locking mechanism to ensure the performance needed in difficult aircraft system environments. In addition, the Thread-Lok GSE QD incorporates the option for a cap or plug to provide protection in the uncoupled condition, when QD halves are not connected and equipment is not attached to the aircraft system.

Thread-Lok QDs use proven engineering and design experience to provide a simple one-hand operation to thread the QD halves together with a visual confirmation of proper and full coupling to improve both time and safety. The Thread-Lok design incorporates tang and slot design, which engage when the coupling halves are threaded together and fully connected. When the QD halves are fully connected, the slot (coupler-hose half) is engaged with the tang (nipple-bulkhead or manifold half) to provide both visual and touch indication of the fully connected position. The QD can only engage and lock in one position with the tang and slot, to confirm full connection and full internal-valve open-flow position. The engaged slot and tang also provide a secondary lock in the connected position, preventing the coupling halves from unintentional uncoupling due to vibration in service.

Thread-Lok couplings use Parker’s efficient, self-sealing valve design that permits fluid flow with minimum pressure loss and turbulence. Flush-faced valve design also minimizes air inclusion or spillage during coupling or uncoupling. The design allows for simple, one-handed operation to connect (thread clockwise) or disconnect (pull back on the outer actuating sleeve and thread counter clockwise) the coupling halves during installation or maintenance on the fluid system.

As the coupling halves are threaded together, the internal fluid flow path opens. When in the fully open position, the coupling halves are locked together using Parker Aerospace’s reliable and high-strength acme threads. The acme threads provide robust performance in harsh environments along with making it impossible to cross thread during connection, as can be the case with finer thread products. Typical installations use the GSE coupler half with plug on the ground equipment (hose) side. The GSE nipple half with cap installs in a panel or in a manifold on the aircraft side providing access for the system maintenance activities.

The Thread-Lok quick disconnect requires linear movement to connect and disconnect along with room to access the outer, or actuating sleeve, by hand in order to pull back the sleeve and rotate to disconnect the two halves.

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Tech Specifications:

MATERIALS OF CONSTRUCTION: Stainless steel or other materials specified
FOR FLUID TYPE: Hydraulic, fuel, and cooling system applications

Features & Attributes

  • Provides ease of maintenance in fluid systems allowing connection to the hydraulic, cooling, or other systems of the aircraft with ground equipment when required
  • Designed to protect system integrity without restricting fluid flow rate or operation
  • Thread to connect with positive visual and touch indication of fully connected and latched position
  • Meets performance requirements of SAE specification AS1709
  • Small and very efficient size and flow-rate combination, ideal for hydraulic, fuel, and cooling system applications
  • Low pressure drop based on streamline valve design
  • Simple, one-hand connect and disconnect operation for ease of use
  • Range of end-fitting styles and fluid-compatibility options available
  • Stainless steel construction meets typical electrical bonding requirements
  • Engineered, tested, and constructed to provide long-term, reliable service for both high-rate cycling systems and continuous-flow systems
  • Prevents fluid loss or spillage and air inclusion when connected and disconnected during maintenance


The Parker Aerospace Thread-Lok GSE QDs are used on a variety of aerospace and related applications where positive indication of latching is important. Along with robust performance in harsh environments, their small size, light weight, and high reliability are important for systems in service today. Programs include Boeing 787, Airbus A380 and A350 hydraulic system connections for commercial jets. These GSE QDs are also used in military applications and a range of cooling system fluids such as polyalphaolefin (PAO), ethylene glycol (EGW), and propylene glycol (PGW).

For the best choice where reliable and robust performance is required, Parker Aerospace recommends the Thread-Lok GSE quick-disconnect coupling series for your ground-to-aircraft service connections. The mechanical advantage of connecting the coupling halves with a thread-together design often provides the most robust performance in systems including engines, landing gear, and brake systems.

The Thread-Lok QD and Thread-Lok GSE series have been proven over years of service, with a history of reliability both in the air on the ground. The baseline qualification for this product is based on the applicable requirements of industry standard SAE AS1709 specification. In some cases, qualification is based on or may be required for specific platform installation and performance requirements. Contact Stratoflex Products Division with interface and performance requirements to determine if this product is the best choice for your installation and application.

Optional Features

Standard configuration is available in stainless steel body construction. Component materials include stainless steel and other materials compatible with specific fluid applications. Contact Stratoflex Products Division for any other specific material information.

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