The current version is AS33514E, published in 2019. Always check SAE International's website for the most up-to-date information.
The standard was originally derived from military specification MIL-M-81531 but has since evolved to meet modern commercial aviation standards, including those set by Boeing (BAC) and Airbus (ABS).
is a critical aerospace technical standard issued by SAE International that establishes the definitive fluid system interface configuration for flareless tube connections and gasket seals . Originally integrated into United States military systems under the designation MS33514 , this standard regulates the strict geometry, dimensional tolerances, and design criteria required to ensure leak-free performance in high-pressure aircraft hydraulic, pneumatic, and fuel transport systems. sae-as33514
Elias was staring at a specific junction in the secondary hydraulic loop. It was a tiny, unassuming piece of flared metal—the fitting. To a layman, it looked like a standard bolt. To Elias, it was the only thing standing between a successful flight and a $200 million fireball.
Providing reliable sealing for fuel lines, often in conjunction with O-rings designed to be fuel-resistant. Pneumatic Systems: Used in high-pressure air and gas lines.
: Surface roughness must comply with ANSI/ASME B46.1 to prevent leaks at the sealing interface.
Rather than relying on a flared tube system (which structurally alters the shape of the pipe end), AS33514 details a . The system operates by drawing a sleeve tightly against the tube wall during assembly, cutting a microscopic groove or "bite" into the outer diameter of the tubing to secure a high-integrity, metal-to-metal seal. This connection is backed by an integrated gasket seal zone to ensure secondary protection against zero-tolerance micro-leaks. Historical Origins: The Evolution from MS33514 The current version is AS33514E, published in 2019
In fluid systems, tubes carry liquids or gases under massive pressure. Traditional setups use a "flared" tube, meaning the end of the metal tube is stretched into a funnel shape.
Simplifies installation, especially in tight spaces, by eliminating the need to flare thin-walled tubing.
The primary function of the AS33514 standard is to provide a reliable, leak-proof connection for hydraulic and fluid lines without the need for flaring the tube ends. It features a design with an external thread.
SAE AS33514 specifies the complete dimensional interface of the fitting end, including the sealing surface and the threads. This allows for the creation of components that work together seamlessly, forming a reliable, high-pressure seal. is a critical aerospace technical standard issued by
Beyond the Bolt: Why SAE-AS33514 is Changing Aerospace Fluid Systems
SAE-AS33514 sleeves are found throughout fixed-wing and rotorcraft platforms, including:
Installation requires standard wrenches rather than specialized, high-capacity flaring equipment. Status and Future Design Considerations