Aerospace threads are very similar to hydraulic threads but they have significantly tighter tolerances and require more stringent quality control verifications throughout the manufacturing process.

Timeline of thread names:

Standards were created by various organizations which included part numbers designations to be used to order the parts that were required.

• 1940s: US Aerospace started using AN (Air Force-Navy or Army- Navy) standards
• 1941: NAS (National Aerospace Standards) thread and fitting standards were used
• 1950s: MS (Military Standards) standards replaced the AN standards
• 1994: MS standards were cancelled as a cost savings measure, which caused problems. NASM standards were then created
• Mid-1990s: AS (Aerospace Standards) standards were created by SAE

The Aerospace industry today uses many of these standards and part number designations. They will often order parts using ‘older’ part numbers since that is what the aircraft was certified with and still requires today. This leaves suppliers with a part which may actually have multiple part numbers!

Standards and specifications

Each of these standards (AN, MS, NASM, AS) has specification documents for each type of fitting that the aerospace industry requires.

Examples of these include: AS4395 - Permanent swaged hose fittings (replaced MS33656) AS5202 - Reusable hose fittings AS21902 - MS flareless tube fittings (newer designation) AS1919 - 37° flared tube fitting Or MS20823 Elbow 45 deg pipe to flared MS21913 plug flareless tube Or AN919 reducer external thread flared tube

Each specification document provides the details regarding the part (often including a detailed drawing), manufacturing dimensions, material codes, part numbers and other information relevant to manufacturing, purchasing or putting into service. They also have specifications for the type of threads that each of these fittings shall use. There are specifications for many other aspects of military fittings as well (plating, welding… ).

When a customer asks for a part number which starts with AN, MS or AS, it may be wise to review the specification for that part number to help you determine if it is exactly what they are looking for. Whether it be threads, end sizes, material, the specification document will provide the correct descriptions and information for that part. The fitting then has to comply with every aspect of this specification (even including the specifications that are referenced throughout the document).

Revisions

It is also critical to have the correct revision level for each part. Over the years aspects of the parts have changed. These modifications have been reflected in the specification documents. Some parts have alphabetical revisions, while others have numerical revisions. It is always best to ensure that the customer provides the revision level that they require for each part since the incorrect revision may make the part unusable in a specific application.

Quality systems

It is important to note as well, that most Aerospace parts must be manufactured by companies that have a quality system that has been audited by outside parties to Aerospace standards as well. These include the AS9000 series (AS9100 for manufacturer’s, AS9110 for repairs, AS9120 for distributors), NADCAP for special processes, as well as FAA or EASA compliance for certain applications. The nature of the application makes safety of everyone on board a critical factor when manufacturing or distributing Aerospace parts.

All of Aerocom’s products undergo quality checks prior to shipping. For aerospace and military clients, we provide fluid connectors that comply with all industry standards through our AS9120 quality system. Documentation and certificates are controlled per our quality management systems. When your application demands fluid connectors with extremely high reliability and safety, Aerocom delivers precision-manufactured solutions backed by technical expertise and quality documentation.

Requests for aerospace parts often come with all sorts of requirements and it is important to provide parts that meet all of the specified needs in order for the part to fit correctly into the aircraft. Understanding all of the numbering designations described in the specifications is essential to providing customers with the correct parts!

Contact Aerocom today to discuss any of your Aerospace requirements.