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.

Chobert Rivets

Chobert rivets are made with either snap or countersunk heads.  The action of closing a Chobert rivet is illustrated.  When the mandrel is pulled through the tapered hole the rivet head is formed.  As the mandrel continues pulling through the rivet, the shank expands and fills the hole.

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Sealing pins can be fitted in the rivet bore.  This increases the shear strength of the rivets and prevents moisture entering.

The manufacturer’s rivet part number is in the form of a code giving rivet material and diameter and grip length in ¹/₃₂ in.

Chobert rivets with oversize shanks are available for repair work on aircraft.

The chobert rivet is closed with a steel mandrel which forms part of the riveting tool.  A different sized mandrel is used with each diameter of rivet.  Before use it should be checked for diameter using an approved gauge.  The mandrel must also be inspected for scratches or other damage and must be clean and lightly lubricated.  Mandrels must be replaced when the head diameter has been reduced by 0.002 inch.