Common Types of Aerospace Fittings

Throughout the aerospace industry, flared or flareless fittings are used to attach sections of tubing. The SAE Aerospace Standards, commonly known as AS Standards, establish the requirements for fittings used in fluid systems throughout many types of aircraft. There are six common thread styles and connections used in aerospace fittings: AN 24 fittings, AN 37 fittings, O-ring bosses (ORBs), National Pipe Thread (NPT), hose barbs, and hose clamps. In this blog, we will discuss each type.

AN 24 Fittings

AN 24 fittings are 24 degree cone flareless fittings and nuts. These are used in aircraft fluid systems with nominal operating pressures up to and including 3,000 psi.

AN 37 Fittings

Fittings of this type are 37 degree JIC (Joint Industry Council) flared internal cone fluid connection fittings. They are intended for use with 37 degree external cone spherical nose and seal rings fittings. They are used in a wide range of aerospace fluid systems.

O-Ring Boss

The O-ring boss (ORB) is a multipurpose thread suited to medium and high-pressure hydraulic applications. The male thread features an o-ring at its base that mates with a chamfer machined into its female counterpart, making ORBs ideal for leak-proof applications. To identify the proper ORB threads, consult the outer and inner diameters of both the male and female threads.

National Pipe Thread

National Pipe Thread (NPT) fittings provide a leak-proof seal without the need for added PTFE tape or another type of sealant compound. NPT standards refer to technical standards for screw threads on threaded pipes and pipe fittings. These can include both tapered and straight thread series for purposes such as rigidity, pressure-tight sealing, or both. Fittings of this type can provide an effective seal for pipes transporting liquids, gases, steam, and hydraulic fluid.

Hose Barbs

Hose barbs allow for an easy push-connection of flexible plastic or rubber hosing that offers a robust connection. Hose barb fittings may have one or several barbs, evenly spaced or with extra space behind, between, or in front of each barb. The fitting itself may be plastic or metal and have barbs of varying types. These differences are meant to improve the grip and seal of the tubing for its specific application.

Hose Clamps

A hose clamp, also known as a hose clip or hose lock, is a device used to attach and seal a hose onto a fitting such as a barb or nipple. There are many types of hose clamps, the primary of which are screw/band clamps, also known as worm gear clamps, as well as spring clamps, wire clamps, and ear clamps.

While these are the most common types of aerospace fittings, many other types exist. These include bushings, nipples, sleeves, caps, nuts, push-to-connect couplings, crosses, plugs, tees, elbows, reducers, and unions. It is important to state that, while some fittings look identical, no two are the same. For example, Army-Navy (AN) military standard fittings call for tighter tolerances and define all types of fittings. Adversely, the Joint Industry Council (JIC) uses AN standards only as a baseline for their own standards which cover fewer sizes. Whatever type of fitting you need, ensure you are getting it from a trusted source.

For all types of aerospace fittings and much more, look no further than Methodical Purchasing. Owned and operated by ASAP Semiconductor, we can help you find all types of parts for the aerospace, civil aviation, defense, electronics, industrial, and IT hardware markets. Our account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at or call us at +1-714-705-4780. Let us show you why we consider ourselves the future of purchasing.


November 23, 2022

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