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General
FLUID LINES AND FITTINGS
Question | Answer |
---|---|
Of what material are most low-pressure rigid fluid lines made? | 1100-1/2 hard or 3003-1/2 hard aluminum alloy tubing. |
Is the size of a rigid fluid line determined by its inside or its outside diameter? | By its outside diameter. |
When routing a fluid line parallel to an electrical wire bundle, which should be on top? | The electrical wire bundle should be on top. |
What is the function of the lay line (the identification stripe) that runs the length of a flexible hose? | This line shows the mechanic whether or not the line has been twisted when it was installed. The line should be straight, not spiraled. |
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 of the way to the flare cone. |
Where are quick-disconnect fluid line couplings normally used in an aircraft hydraulic system? | Quick disconnect couplings are normally used where the engine-driven pump connects into the hydraulic system. |
Is the size of a flexible hose determined by its inside or its outside diameter? | By its inside diameter. |
What is the minimum amount of slack that must be left when a flexible hose is installed in an aircraft hydraulic system? | The hose should be at least 5% longer than the distance between the fittings. This extra length provides the needed slack. |
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 damage can be caused by overtightening an MS flareless fitting? | Overtightening drives the cutting edge of the sleeve deeply into the tube and weakens it. |
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 is the principal advantage of Teflon hose for use in an aircraft hydraulic system? | Teflon hose retains its high strength under conditions of high temperature. |
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. |