Fluid Lines and Fittings Flashcards
What two general types of fluid lines are commonly used in aircraft plumbing?
Metal tubing and flexible hose
How is metal tubing classified in size?
By the outside diameter in 1/16 inch increments and wall thickness
How are flexible hose sizes designated?
By the internal diameter measured in 1/16 inch increments
What caution must be observed when deburring the end of tubing after cutting?
Wall thickness is not fractured or reduced in size
Name two kinds of flares commonly used in aircraft plumbing systems
The single flare and double flare
Name the parts of a military standard flareless tube fitting
Body, sleeve and nut
What type of fittings and materials should be used with stainless steel tubing?
Stainless steel fittings
What is the purpose of a sleeve on a flared tube connection?
The nut and sleeve together when tightened will draw the sleeve and tubing flare tightly against the male fitting to form the seal.
What happens to a flareless tube fitting when it is over tightened?
The nut drives the cutting edge of the sleeve deeply into the tube, causing the tube to be weakened
What are the identification markings usually found on flexible rubber hose?
A lay line, hose size, date of manufacture, pressure and temperature limits
Name at least two synthetic materials commonly used in the manufacture a flexible hose
Buna-N, Neoprene, Butyl, Ethylene Propylene Diene Rubber, Teflon
When selecting a flexible hose for using 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?
No more than 9 inches along the length of the hose
What percentage of flattening is allowed when bending metal tubing?
Do not exceed 75% of the original diameter
How can you determine if a fitting in an AN type rather than a AC type?
AN - Have a shoulder
AC - Do not have shoulder
What is 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
How do you tell a flareless fittings from flare-type fitting?
Flareless fittings do not have a flare cone, and there is no space between the threads and the end of the fitting
What is the effect of overtightening a flare tight 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 grounded to the structure
What are some of the most important advantages of Teflon tubing?
Compatible with most fluids, temperature range, low resistance to fluid flow and long shelf life and service life
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
Why are quick disconnect fittings used?
Quick means to connect or disconnect a fluid line without loss of fluid and entrance of air to the system
When fabricating a flexible hose, what percent of the total length must be allowed for freedom of movement under pressure?
5 to 8% of its total length
How can you tell that a flexible hose has been installed in a twisted position?
A twisted lay line indicates an incorrect installation
Name at least two considerations when installing flexible hose assemblies
Slack, flexing, twisting, bending, clearance and clamps
Scratches and nicks may be repaired if they are less than what percent of the wall thickness
10%
Flexible hoses should be clamped at least every how many inches?
24 inches
What is the difference between flare angles for aviation and automotive flares?
45° flares are used on cars, 35° to 37° are used in Aviation
