Properly assembled AS33514 fittings perform well in high-vibration environments.
SAE-AS33514 is frequently cited in broader military specifications (MIL-SPECS) for hydraulic and fuel systems:
: Pitch diameter and specific fitting diameters must be concentric within .008 to .005 full indicator movement (F.I.M.).
The standard is incredibly strict about three things that determine if a plane stays in the sky or leaks hydraulic fluid at 30,000 feet: Concentricity:
hoses reinforced with stainless steel wire to handle the extreme environments of flight. WMT Maintenance Technik AG comparison table between this and the newer standards that replaced it? sae-as33514
SAE-AS33514: A Guide to Aerospace Flareless Tube Fittings is an aerospace standard that defines the dimensions and requirements for male flareless tube fitting ends used in fluid systems. Originally developed for military applications under the designation MS33514 , the standard was transitioned to SAE International to ensure continued maintenance and relevance in the modern aerospace industry. Core Technical Purpose
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).
Unlike standard UNJ threads that can be cross-threaded easily, AS33514 introduces a modified lead-in geometry. It actively prevents "cross-starting." If the fitting isn't aligned axially, the nut physically will not engage. It forces the mechanic to stop, reset, and try again.
Always verify the dash number (e.g., -1 for 1/4”, -2 for 3/8”) and outlet flow orifice. WMT Maintenance Technik AG comparison table between this
Comprehensive Guide to SAE-AS33514: Flareless Tube Fitting Standard
Preferred in applications needing robust, standardized components, as they often supersede military specifications (e.g., MIL-F-55060).
In the demanding field of aerospace engineering, fluid systems reliability is paramount. High-pressure hydraulic and fuel lines require robust connections that can withstand vibration, temperature extremes, and immense pressure without leaks. One of the industry-standard specifications governing these connections is , "Fitting End, Standard Dimensions for Flareless Tube Connection and Gasket Seal."
Customers should always specify the latest revision (currently AS33514E) to ensure compliance with current design and manufacturing requirements. Earlier versions like AS33514C and D are now historical but may still be referenced for legacy systems. Core Technical Purpose The standard was originally derived
Whether you are designing a new harness for a UAV, repairing a legacy Cessna, or procuring parts for a 787 production line, specifying SAE-AS33514 compliant sleeving ensures that every label will outlast the aircraft itself.
: Tooling marks on the sealing surface must comply with stringent roughness metrics. For instance, annular tool marks are strictly bounded—often to a maximum finish of 100 microinches Racap R sub a
: AS33514 fitting ends are designed to be compatible with other standard components, such as those defined in SAE-AS4395 or SAE-AS18280 .
It seals tightly without needing to bend, stretch, or flare the actual tube ends.
Deep Dive into SAE-AS33514: The Aerospace Flareless Tube Fitting End Standard