motion restrained where necessary, but should
FLEXIBLE TUBING (HOSE). --Flexible
never be rigidly supported. To avoid chafing use
hose assemblies consist of lengths of hose coupled
suitable bulkhead-type grommets or cushioned
with threaded end fittings. There are two classes
of flexible tubing--high pressure and low
Protect hose installations from excessive
temperature, such as exhaust blasts, supercharger
You can get the specifications for flexible hose
ducts, and the like, either by shrouding or
by interpreting the identification code on the hose.
relocation. Use flame-resistant hose forward of
This identification, a series of dots and dashes,
the firewall on certain aircraft or as NAVAIR
gives hose size, temperature range, and date of
instructions may direct.
manufacture. The date of manufacture is in
quarter of year and year. Refer to NA 01-1A-8
Where hoses connect to an engine or to
for a detailed discussion of flexible hose identi-
engine-mounted accessories, provide 1 1/2 inches
of slack between the last point of support and
engine attachment. This prevents the chance of
You cannot construct high-pressure flexible
the hose pulling off the nipple due to engine
hose at the organizational level. You must order
movement, Whenever possible, install the hose so
it through supply, as organizational maintenance
all hose markings are visible.
cannot perform high-pressure tests.
All hose materials deteriorate from exposure
to heat, sunlight, excessive moisture, and ozone.
You can order the parts for a low-pressure
Therefore, you should stow hoses in a cool dry
flexible hose through supply and make the hose
place and away from electrical equipment. You
locally. You can reuse fittings from a damaged
can obtain age limits of shelf items based on the
hose if they meet the required specifications.
manufacturer's code from current accessory
bulletins. Stow hose in straight lengths to prevent
When you install hose, make sure it will not
it from setting in a curved position. Replace the
twist under any operating condition. This type
hose if cover material is peeling or flaking, or the
installation lessens the tendency for connecting
braid reinforcement is open to the elements.
fittings to loosen. When you replace hose in
hydraulic, fuel, oil, alcohol, and pneumatic
systems, make sure the new hose is an exact
duplicate of the old hose. By this, the length,
outside diameter, inside diameter, material, type,
and shape (except on directed modifications) must
Maintenance of the pitot-static system consists
be the same as the old hose.
of checking the lines for integrity, water, and
miscellaneous obstructions. A pressure check is
If a bend is necessary when installing hose in
of the utmost importance as any slight leak will
fluid systems, the radius must not be smaller than
result in erroneous indications of the instruments
the minimum specified in NA-01-1A-8. This
during flight. You should also check the pitot
publication shows the minimum bend radii for
heater for proper operation. You can do this by
flexible hose. When practical, it is desirable to use
monitoring a voltage drop when the heat is turned
a radius that is larger than the specified minimum.
on, or by checking the pitot tube for the presence
When you install hose through holes in
brackets and when using supporting clips, there
can be no reduction in hose diameter. If these
conditions are present, they reduce flow, and
damage to the hose may occur.
Do not touch the pitot tube with your bare
The hose must have support every 24 inches.
hand with the heat on. The extreme heat
Closer supports are desirable when practical. The
may cause your skin to stick to the surface.
flexible line support should never cause deflection
of the rigid connecting lines under any possible
The following is an outline for water and
relative motion that may occur. Flexible hose
debris removal from the pitot-static system.
between two rigid connections may have excessive