What are the two types of fluid lines found in aircraft?
Rigid metal lines and flexible hoses
Describe the method of classifying metal tube according to size
Metal tubing is sized according to wall thickness and outside diameter.
Outside diameter is measured in 1/16 inch increments
When installing stainless steel tubing, what types 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
Single and double flare
How can you determine if a fitting is an AN type rather than AC type
AN fittings have a shoulder between the flare cone and the end of the threads, AC don't.
What are the most significant differences between AN and AC fittings?
thread pitch, and
the shoulder between the threads and flare cone on AN fittings
What are the names of the parts of a flare-less tube fitting
The nut and the ferrule or sleeve
How do you tell a flare-less fitting from a flare type fitting?
Flare-less 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?
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 a Mil Spec number, the manufacturer's 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 hose sizes designated?
By the inside diameter, measured in 1/16 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 flare-less 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 contaminants into system