Fluid Lines Flashcards
When flaring aluminum tubing for use with AN fittings, the flare angle must be
37
Which statement is true regarding flattening of tubing in bends?
Flattening by not more than 25 percent of the original diameter is permissible.
A scratch or nick in aluminum tubing can be repaired provided the scratch or nick does not
appear in the heel of a bend.
Hydraulic tubing, which is damaged in a localized area to such an extent that repair is necessary, may be repaired
by cutting out the damaged area and utilizing a swaged tube fitting to join the tube ends.
Flexible hose used in aircraft plumbing is classified in size according to the
inside diameter.
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?
The minimum radius for steel is greater than for aluminum
(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,
both No. 1 and No. 2 are true.
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
52-1/2 inches.
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.
1
Metal tubing fluid lines are sized by wall thickness and
outside diameter in 1/16 inch increments.
From the following sequences of steps, indicate the proper order you would use to make a single flare on a piece of tubing:
- Place the tube in the proper size hole in the flaring block.
- Project the end of the tube slightly from the top of the flaring
tool, about the thickness of a dime. - Slip the fitting nut and sleeve on the tube.
- Strike the plunger several light blows with a lightweight hammer or
mallet and turn the plunger one-half turn after each blow. - Tighten the clamp bar securely to prevent slippage.
- Center the plunger or flaring pin over the tube.
3, 1, 6, 2, 5, 4.
What is the color of an AN steel flared-tube fitting?
Black.
The primary purpose of providing suitable bends in fluid and pneumatic metal tubing runs is to
prevent excessive stress on the tubing
A certain amount of slack must be left in a flexible hose during installation because, when under pressure, it
contracts in length and expands in diameter.
A 3/8 inch aircraft high pressure flexible hose as compared to 3/8 inch metal tubing used in the same system will
have equivalent flow characteristics.
What is an advantage of a double flare on aluminum tubing?
It is more resistant to the shearing effect of torque.
Which statement 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
1
Which statement is true regarding the geometric symbols on identifying color-code bands that are currently used on aircraft plumbing lines?
Symbols are always black against a white background regardless of line content.
The term “cold flow” is generally associated with
impressions left in natural or synthetic rubber hose material.
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
the possibility of reducing the flare thickness by wiping or ironing during the tightening process.
Which tubings have the characteristics (high strength, abrasion resistance) necessary for use in a high pressure (3,000 PSI) hydraulic system for operation of landing gear and flaps?
Corrosion resistant steel annealed or 1/4H.
If a flared tube coupling nut is overtightened, where is the tube most likely to be weakened/damaged?
At the sleeve and flare junction.
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?
AN-818-8.
When installing bonded clamps to support metal tubing,
remove paint or anodizing from tube at clamp location.
