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Understanding why the "flareless" design is standard for critical systems sheds light on the standard's importance. Traditional flared fittings require the tube end to be precision-expanded into a cone shape. The flareless design instead relies on a metal sleeve (or ferrule) that is compressed around the tube. This approach distributes stress more evenly and is far less sensitive to assembly variations, resulting in higher reliability and a longer service life in the punishing environment of an aircraft.

: The standard mandates the use of highly controlled inch-profile UNJ screw threads featuring an increased minor diameter and a mandatory controlled root radius. This minimizes stress concentrations at the root of the thread, enhancing fatigue life under constant vibration.

The relationship between the thread and the hex face must not exceed specified tolerances when measured at specific diameters.

The AS33514E standard (and its predecessors) details several key engineering parameters: 1. Dimension and Geometry sae-as33514

It seals tightly without needing to bend, stretch, or flare the actual tube ends.

Note: While the standard is maintained actively under SAE AS33514E for legacy and active aircraft procurement contracts, it is marked as "Inactive for New Design" in favor of newer fluid connection geometries like AS4395. Design and Geometric Specifications

It ensures interchangeability and compatibility of components from different manufacturers. Understanding why the "flareless" design is standard for

Rather than being a single physical "piece," it is a design specification for a male flareless fitting end

AS33514 does not exist in isolation; it is part of a broader family of fitting and tube standards. It's vital to understand its relationship with others:

Since they do not require a flare (a 37-degree cone at the end of the tube), they are often easier to install in confined, hard-to-reach areas. This approach distributes stress more evenly and is

: The standard dictates critical measurements for concentricity, squareness, and surface roughness to prevent leaks under extreme vibration or pressure.

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.

The current version is AS33514E , released in April 2019.

These standards are used in complementary ways to create a complete connection: