Fluid Lines And Fittings Flashcards
What two general types of fluid lines are commonly used in aircraft pumbing?
Metal tubing and flexiblehose.
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 mesured in 1/16th 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 the double flare.
Name the parts of a military standard flareless-tube fitting:
Body, sleeve and nut.
What type fittings material 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 overtightened?
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 of flexible hose.
(1) Buna-N (2) Neoprene (3) Butyl (4) Ethylene Propylene diene rubber (5) 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 (hose identification) on a flexible hose?
No more than 9” along the length of the hose. (Ref book FAA-H-8083-31 page 9-18)
What percentage of flattening is allowed when bending metal tubing?
25%. Tube must maintain at least 75% of original diameter.
How can you determine if a fitting is an AN type rather than an AC type?
AN – Have a shoulder. AC – Do not.
What is the most significant diferences 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 a flare-type fitting?
Flareless fittings don’t have a flare cone and there in 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 grounded to the structure.
What are some of the important advantages of TEFLON tubing?
Compatible with most fluids, temperature range, low resistance to fluid flow and long shelf 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 into the system.
When fabricating a flexible hose, what percent of the total lenght must be allowed for freedom of movement under pressure?
5 to 8% of its total lenght.
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° in aviation.
