Quick-release Couplings

Quick-release couplings are required at various points in aircraft systems. Typical uses are in fuel, oil, hydraulic and pneumatic systems. Their purpose is to save time in the removal and replacement of components; to prevent the loss of fluid and to protect the fluid from contamination. The use of these couplings also reduces the maintenance cost for the system involved.

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A coupling consists of a male and female assembly. Each assembly has a sealing piston/poppet valve that prevents the loss of fluid when the coupling is disconnected.

When the coupling is disconnected a spring pushes the conical shaped poppet onto a seat to ensure no fluid can escape. When the coupling is connected the piston faces compress the springs and lift the poppet off its seat allowing fluid to pass through.


It is extremely important to ensure the open parts of a disconnected coupling do not become contaminated. This can be achieved by placing blanking caps on the end of the couplings as soon as they have been separated.

Three checks may be used to verify a positive connection. These involve an audible, visual and tactile indication. A click may be heard at the time the coupling is locked and indicator pins will extend from the outer sleeve upon locking, which can be seen and felt.