Fluids Line and Fittings

Question 1

Which coupling nut should be selected for use with 1/2-inch aluminum oil lines which are to be
assembled using flared tube ends and standard AN nuts, sleeves, and fittings?

Answer 1

AN-818-8

Question 2

Metal tubing fluid lines are sized by wall thickness and

Answer 2

Outside diameter in 1/16 inch incriments

Question 3

From the following sequences of steps, indicate the proper order you would use to make a single flare
on a piece of tubing:
1. Place the tube in the proper size hole in the flaring block.
2. Project the end of the tube slightly from the top of the flaring tool, about the thickness of a dime.
3. Slip the fitting nut and sleeve on the tube.
4. Strike the plunger several light blows with a lightweight hammer or mallet and turn the plunger one- half turn after each blow.
5. Tighten the clamp bar securely to prevent slippage.
6. Center the plunger or flaring pin over the tube.

Answer 3

3,1,6,2,5,4

Question 4

Hydraulic tubing, which is damaged in a localized area to such an extent that repair is necessary, may be
repaired

Answer 4

By cutting out the damaged area and utilizing a swaged tube fitting to join the tube ends

Question 5

What is an advantage of a double flare on aluminum tubing?

Answer 5

More resistant to damage when the joint is tightened

Question 6

A certain amount of slack must be left in a flexible hose during installation because, when under
pressure, it

Answer 6

Contracts in length and expands in diameter

Question 7

The term ‘cold flow’ is generally associated with

Answer 7

Impression left in natural or synthetic rubber hose material

Question 8

What is the color of an AN steel flared-tube fitting?

Answer 8

Black

Question 9

Which of the following statements is/are correct in reference to flare fittings?
1. AN fittings have an identifying shoulder between the end of the threads and the flare cone.
2. AC and AN fittings are considered identical except for material composition and identifying colors.
3. AN fittings are generally interchangeable with AC fittings of compatible material composition.

Answer 9

1

Question 10

Flexible lines must be installed with

Answer 10

A slack of 5 to 8 percent of the length

Question 11

The maximum distance between end fittings to which a straight hose assembly is to be connected is 50
inches. The minimum hose length to make such a connection should be

Answer 11

52 1⁄2 inches

Question 12

Excessive stress on fluid or pneumatic metal tubing caused by expansion and contraction due to
temperature changes can best be avoided by

Answer 12

Providing bends in the tubing

Question 13

The material specifications for a certain aircraft require that a replacement oil line be fabricated from
3/4-inch 0.072 5052-0 aluminum alloy tubing. What is the inside dimension of this tubing?

Answer 13

0.606 inch

Question 14

In most aircraft hydraulic systems, two-piece tube connectors consisting of a sleeve and a nut are used
when a tubing flare is required. The use of this type connector eliminates

Answer 14

The possibility of reducing the flare thickness by wiping or ironing during the tightening process

Question 15

Which statement(s) about Military Standard (MS) flareless fittings is/are correct?
1. During installation, MS flareless fittings are normally tightened by turning the nut a specified amount,
rather than being torqued.
2. New MS flareless tubing/fittings should be assembled clean and dry without lubrication.
3. During installation, MS flareless fittings are normally tightened by applying a specified torque to the
nut

Answer 15

1

Question 16

When flaring aluminum tubing for use with AN fittings, the flare angle must be

Answer 16

37 degrees

Question 17

Scratches or nicks on the straight portion of aluminum alloy tubing may be repaired if they are no
deeper than

Answer 17

10 percent of the wall thickness

Question 18

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

Answer 18

Inside diameter

Question 19

A scratch or nick in aluminum tubing can be repaired provided it does not

Answer 19

Appear in the heal of the bend

Question 20

Which of the following hose materials are compatible with phosphate-ester base hydraulic fluids?
1. Butyl.
2. Teflon.
3. Buna-N.
4. Neoprene.

Answer 20

1 and 2

Question 21

Which tubings have the characteristics (high strength, abrasion resistance) necessary for use in a high-

Answer 21

Corrosion resistant steel annealed or 1/4H

Question 22

When installing bonded clamps to support metal tubing,

Answer 22

Remove paint or anodizing from tube clamp location.

Question 23

In a metal tubing installation,

Answer 23

Tension is undesirable because pressurization will cause it to expand and shift

Question 24

The best tool to use when cutting aluminum tubing, or any tubing of moderately soft metal is a

Answer 24

Hand operated wheel type tubing cutter

Question 25

The primary purpose of providing suitable bends in fluid and pneumatic metal tubing runs is to

Answer 25

Prevent excessive stress on the tubing

Question 26

Which of the following statements is true regarding minimum allowable bend radii for 1.5 inches OD or
less aluminum alloy and steel tubing of the same size?

Answer 26

The minimum radius for steel is greater than for aluminum

Question 27

A gas or fluid line marked with the letters PHDAN is

Answer 27

Used to carry a hazardous substance

Question 28

Which statement is true regarding the variety of symbols utilized on the identifying color-code bands
that are currently used on aircraft plumbing lines?

Answer 28

Symbols are always black against white background regardless of the line content

Question 29

If a flared tube coupling nut is overtightened, where is the tube most likely to be weakened/damaged?

Answer 29

At the sleeve and flare junction

Question 30

Which statement concerning Bernoulli’s principle is true?

Answer 30

The pressure of the fluid decreases at point where the velocity of the fluid increases

Question 31

(1) Bonded clamps are used for support when installing metal tubing.
(2) Unbonded clamps are used for support when installing wiring.

Regarding the above statements,

Answer 31

Both 1 and 2 are true

Question 32

Which statement is true regarding flattening of tubing in bends?

Answer 32

Flattening may not be more than 25 percent of the original diameter is permissible

Question 33

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

Answer 33

Have equivalent flow characteristics