Fluid Lines and Fittings Oral Flashcards
What are the two types of fluid lines commonly found in aircraft?
Rigid metal lines and flexible hoses.
Describe the method of classifying metal tubing according to size.
Metal tubing is sized according to wall thickness and outside diameter. Outside diameter is measured in 1/16th inch increments.
When installing stainless steel tubing, what type of fittings should be used?
Stainless steel fittings.
What is the function of the sleeve on a flared-tube fitting?
The nut fits over the sleeve and draws the sleeve and the tubing flare tightly against the male fitting to form the seal.
Describe the two types of flares commonly used on aircraft tubing
The single flare and the double flare.
How can you determine if a fitting is an AN type rather than an AC type?
AN fittings have a shoulder between the flare cone and the end of the threads, AC fittings do not.
What are the most significant differences between AN and AC fittings?
Sleeve length, thread pitch, and the shoulder between the threads and the flare cone on AN fittings.
What are the names of the parts of a flareless tube fitting?
The nut and the sleeve.
How do you tell a flareless fitting from a flare-type fitting?
Fareless fittings don′t have a flare cone and there is no space between the threads and the end of the fitting.
What is the effect of over-tightening a flare type fitting?
The sealing surface may be damaged or the flare cut off.
In addition to being securely clamped, what is an additional requirement for installing metal fuel, oil, and hydraulic lines?
The lines must be electrically bonded to the structure.
What are some of the important advantages of Teflon tubing?
It is compatible with nearly every liquid, has a broad operating temperature range, low resistance to fluid flow and has a very long shelf and service life.
Describe the identification markings commonly found on flexible hoses.
A lay line, identification such as Mil Spec number, the manufacturers name or symbol, the hose size and a date code.
How can you determine if a flexible hose has been correctly or incorrectly installed?
The lay line will be straight if the hose is properly installed. A twisted lay line indicates an incorrect installation.
How are flexible hoses designated?
By the inside diameter, measured in 1/16th inch increments.
What precautions must be observed when deburring the end of a tube after it is cut?
The wall thickness must not be reduced in size or fractured.
Describe the operation of quick disconnect couplings.
Each half has a valve that is held open when coupled and is spring loaded closed when disconnected.
If you fabricate a replacement for a flexible hose, what percentage of the total length must be added to allow for movement under pressure?
5 to 8 percent.
What happens to the tube when a flareless fitting is overtightened?
The tube is weakened when the nut drives the cutting edge of the sleeve too deeply into the tube.
Why are quick disconnect fittings used?
To provide a quick means to connect or disconnect a fluid line without loss of fluid or entrance of air into the system.
Of what material are most low pressure rigid fluid lines made?
1100-½ hard or 3003-½ 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
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 O.D.
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 1/6th turn to 1/3 turn. Never turn it more than 1/3 turn with a wrench.
How much pressure is used to proof test a flexible hose assembly?
This varies with the hose, but is generally about two times the recommended operating pressure for the hose.
