Hose Assemblies. The ends of all hose assemblies must be capped
during storage with polyethylene protective plugs conforming to
National Aerospace Standard (NAS) 815 or equivalent to prevent
Hose is used in aircraft plumbing whenever the connected components
must be free to move or whenever extreme vibrations are a problem.
Aircraft hose is composed of two or more layers of differing
The inner layer, or liner, is a leak-tight nonmetallic
tube made from either synthetic rubber or teflon.
The liner is
reinforced against swelling or bursting by one or more outer layers
of braid. The kind and number of braid layers depend on the intended
operating pressure range of the hose assembly.
The pressure capabilities of hose assemblies are divided into two
general categories: medium pressure and high pressure.
pressure range includes operating pressures of 1,500 psi and below.
High-pressure hose is designated for operating pressure systems up to
but not exceeding 3,000 psi.
Aircraft hose and hose assemblies can be readily identified by
markings found either stenciled along the length of the hose or
imprinted on an affixed, metal band. These markings include the date
of manufacture or fabrication, size, military specification number,
and date of pressure test.
Hose size is expressed in sixteenths of an inch by a dash number
referring to the inside diameter (ID) of the hose.
Replacement of rubber hose assemblies must be accomplished at
maintenance manual. Teflon hose does not deteriorate as a result of
age; therefore, periodic replacement is not required.
and teflon hose assemblies are subject to damage during operation
that can be cause for replacement.
Examples of these damages are:
cold flow, weather checking, leaks, or broken wires exceeding
For the most part, hose assemblies are available through supply
channels as factory prefabricated parts.
For expediency, however,
they can be field fabricated in accordance with the outlined
prefabricated assemblies only. Field fabrication is not authorized.