Fluid Lines & Fittings Flashcards
How are rigid fluid lines sized, and what increments are used?
By outside diameter in 1/16inch increments, and by wall thickness in 1/1000inch increments.
Name the two types of fluid lines used on aircraft.
Rigid and flexible lines.
What markings are found on flexible hoses?
Size, manufacturing date, pressure range, and temperature limits.
Identify the features of flared-tube fittings.
Flared-tube fittings consist of a sleeve and a B-nut, has a cone angle of 37 degrees, and are usually blue.
What caution should be exercised when deburring?
Not to reduce wall thickness.
Name the parts of a standard flare-less fitting.
The body, sleeve, and nut.
Name two kinds of flares.
The single flare and the double flare.
What is the advantage of flexible Teflon?
Extremely broad operating temperature range, compatible with nearly every liquid used, and has an almost limitless shelf and service life.
How are flexible hoses sized?
By inside diameter at 1/16inch increments.
How does a quick disconnect work?
Fluid coupling that incorporates a check valve (valve and spring) to prevent fluid loss when connecting or disconnecting.
How do you determine if a line is twisted after installation?
By the lay line running the length of the hose, line should be straight not spiraled.
What is the minimum amount of slack that must be left when a flexible hose is installed in an aircraft hydraulic system?
Hose should be at least 5% longer than the distance between the fittings, extra length provides the needed slack.
What damage can be caused by overtightening an MS flareless fitting?
Overtightening drives the cutting edge of the sleeve deep into the tube and weakens it.
What kind of fittings should be used on stainless steel lines?
Stainless steel.
How should rigid, oil, fuel, and hydraulic lines be installed?
Routed through the aircraft for shortest practical length, and clamped and bonded to the structure with integrally bonded line support clamps.
What is the purpose of a Quick Disconnect (QD)?
Faster installation or removal, prevents fluid loss, and no air or debris is allowed to enter the system.
What is the difference between AN and AC flared tube fittings?
Cone angle, thread pitch, color, body length, and AN fittings have a shoulder between the end of the flare cone and the first thread while AC fittings do not.
What is the purpose of a sleeve on a flared tube fitting?
The sleeve draws the tubing flare tightly against the male fitting to form a seal.
What are some visual differences between a flare-less fitting and a flared fitting?
Flare-less fittings have no flare cone and no space between threads and the fitting.
What are the effects of over torquing a flared fitting?
Damages the flare, causing a weak point in the tube.
Of what material are most low-pressure rigid fluid lines made?
1100-1/2 hard or 3003-1/2 hard aluminum alloy tubing.
When routing a fluid line parallel to an electrical wire bundle, which should be on top?
The electrical wire bundle should be on top.
Where are quick-disconnect fluid line couplings normally used in an aircraft hydraulic system?
Where the engine-driven pump connects into the hydraulic system.
How tight should an MS flareless fitting be tightened?
Tighten the fitting by hand until it is snug, and then turn it with a wrench for 1/6-turn to 1/3-turn. Never turn it more than 1/3-turn with a wrench.
What kind of rigid tubing can be flared with a double flare?
5052-O and 6061-T aluminum alloy tubing in sizes from 1/8-inch to 3/8-inch OD.
What precautions should be taken when flaring a piece of aluminum alloy tubing?
The end of the tubing must be polished so it will not crack when it is stretched with the flaring tool.
How much pressure is used to proof test a flexible hose assembly?
This varies with the hose, but it is generally about two times the recommended operating pressure for the hose.
Of what material should rigid lines be made that carry high pressure (3,000 psi or greater) hydraulic fluid?
Annealed or 1/4-hard corrosion-resistant steel.
Is the size of a rigid fluid line determined by its inside or its outside diameter?
By its outside diameter.
How can you distinguish an AN fluid line fitting from an AC fitting?
The AN fitting has a shoulder between the end of the flare cone and the first thread. The threads of an AC fitting extend all the way to the flare cone.
What is the difference between the flare angle for aircraft and automotive fittings?
Aircraft fittings have a 37 degree flare angle and automotive fittings use 45 degree.
What should be done to the end of a tube that is to be flared?
The cut end should be polished to remove any sharp edges that could cause the tubing to crack.
What is the function of the lay line (the identification stripe) that runs the length of a flexible hose?
To show the mechanic whether or not the line was twisted when it was installed. The line should be straight, not spiraled.
Is the size of a flexible hose determined by its inside or outside diameter?
By its inside diameter.
What is the principle advantage of Teflon hose for use in an aircraft hydraulic system?
Teflon hose retains its high strength under conditions of high temperature.
