AIR 1120 Flexible Lines

Flexible lines must be installed with

• a slack of 5 to 8 percent of the length.

• a slack of at least 10 to 12 percent of the length.

• enough slack to allow maximum flexing during operation

• at least one 90° bend

Answer explanation

When flexible lines are installed in a fluid power system, they should be between 5 percent and 8 percent longer than the space between the fittings. This extra length (this slack) makes allowance for expansion in the system due to heat and for the fact that a hose contracts in its length when it is pressurized

Flexible hose used in aircraft systems is classified in size according to the

• outside diameter.

• wall thickness

• inside diameter

• reinforcement thickness

Answer explanation

The size of flexible hose is determined by its inside diameter. Sizes are in 1/16-inch increments and relate to corresponding sizes of rigid tubing with which it can be used

A 3/8 inch aircraft high pressure flexible hose as compared to 3/8 inch metal tubing used in the same system will

• have higher flow capabilities.

• have equivalent flow characteristics

• usually have interchangeable applications

• be used more often than rigid metal tubing

Answer explanation

Flexible hose may be used in any part of an aircraft fluid system where it has been proven by the aircraft manufacturer to be suitable. The hose must be able to carry the pressure, withstand the vibration, and pass the required fluid flow. The size of a flexible hose is approximately its inside diameter in 1/16-inch increments. This refers to the outside diameter of a rigid tube that has the equivalent flow characteristics

Which of these flexible line materials are used with petroleum base hydraulic fluids?

• Natural rubber, Ethylene-propylene

• Neoprene, Buna-N

• Natural rubber, Butyl rubber

• Butyl, Neoprene

Answer explanation

petroleum-base hydraulic fluid are made of synthetic rubber. Neoprene and Buna-N are forms of synthetic rubber

Teflon hose that has developed a permanent set from being exposed to high pressure or temperature should

• not be straightened or bent further

• not be reinstalled once removed

• be immediately replaced

• be replaced within 100 hours or 6 months

Answer explanation

When a Teflon hose that has developed a permanent set from exposure to high pressure or temperature is removed from an aircraft hydraulic system, its ends should be supported to prevent the hose from being straightened or further bent

What markings are on a fluid line that is carrying hydraulic fluid?

• Blue and Yellow stripes with circles on a white background

• Orange and Blue stripes with connected diamonds on a white background

• Blue stripe with squares on a white background

• Red stripe with stars on a white background

Flexible fluid lines can handle negative and positive pressure

• True

• False

What connection do low pressure de-ice flexible lines most often use?

• Flared

• Beaded

• Swaged

• Flareless

What design components make up all flexible fluid lines?

• Inner Liner

• Reinforcement layer

• Outer Cover

• Flare

• B-nut

High-pressure hoses of the same dash number have smaller internal diameters.

• True

• False

• Depends on the fluid being carried

• Depends on the manufacturer