Fluid Lines and Fitttings Flashcards
What are two types of fluid lines commonly 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 1/16th 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 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 sleeve.
How do you tell a flareless fitting from a flare-type fitting?
Flareless 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 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 if properly installed. A twisted lay line indicates an incorrect installation.
How are flexible hose sizes 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.
Name the parts of a Military Standard flareless-tube fitting?
A body, sleeve, and nut.
What are the identification markings that are usually found on flexible rubber hose?
Hose size, manufacturer, date of manufacture, pressure, and temperature limits.
Name at least two synthetic materials commonly used in the manufacture of flexible hose.
Buna-N, Neoprene, Butyl, Ethylene, Propylene-Diene rubber, Teflon.
When selecting a flexible hose for use in a phosphate-ester based hydraulic fluid (Skydrol) system, the hose should be made of which synthetic rubber compound?
Butyl.
What is the maximum interval for repeating the required markings on a flexible hose?
Not more than nine inches along the length of the hose.
What percentage of flattening is allowed when bending metal tubing?
Do not exceed 75% of original diameter.
How can you tell that flexible hose has been installed in a twisted position?
By the identification stripe running along the hose length.
Name at least two considerations when installing flexible hose assemblies.
Slack, flexing, twisting, bending, clearance, and clamps.
Flexible hose should be clamped at least every how many inches?
24 inches.
Scratches and nicks may be repaired if they are less than what percentage of the wall thickness?
10%.
What is the difference between flare angles for aviation and automotive flares?
Aviation is 37 degrees, automotive is 45 degrees.
