Supplied B1 Module 07A textbook: PDF pages 225–240.
Tubing identification and sizing
Confirm material, outside diameter, wall thickness and fitting specification before fabricating or replacing a line. Tubing is commonly sized by outside diameter, while wall thickness affects internal diameter and strength. System identification markings help avoid connecting incompatible services. A rigid pipe, flexible hose and electrical conduit can look similar from a distance but have very different requirements. Use the approved tubing and fittings for the fluid, pressure, temperature and location. Do not judge compatibility only by whether threads engage.
What is commonly used to state rigid tubing size? Outside diameter and wall thickness.
Cutting, bending and flaring
Cut squarely and remove internal and external burrs while preventing debris entry. Place required nuts and sleeves before making the flare. Use an appropriate bender to prevent flattening and wrinkling; observe the specified bend radius. Aircraft flared fittings commonly use a 37-degree flare and must not be confused with a 45-degree automotive flare. Inspect concentricity, smoothness and wall condition. A cracked or distorted flare should be remade through an approved process rather than forced into sealing.
Why are 37-degree and 45-degree flares not interchangeable? Their mating surfaces have different angles.
Rigid-line installation and supports
The line should align with its fittings without forcing them into position. Start nuts correctly and use a backup wrench to prevent twisting adjacent fittings. Apply prescribed torque and inspect supports and clearances. Clamps prevent vibration and chafing, but excessive restraint can create stresses from thermal expansion or movement. Protect the line from adjacent structure, cables and heat. Routing is part of the installation design; a shorter substitute route may create interference or remove necessary flexibility.
What is indicated by a line that must be forced into its fittings? Possible misalignment or incorrect fabrication.
Hose construction and limits
Flexible hoses contain a compatible inner liner, reinforcement and protective cover appropriate to the application. Verify part number, service and shelf-life controls and fitting condition. Minimum bend radius, pressure rating and temperature rating are different limits. A protective fire sleeve does not make a hose immune to all heat damage. Do not twist a hose during installation; use identification stripes where provided to reveal twist. Allow the designed movement and slack without creating rubbing or excessive bends.
What does twisting a hose during installation threaten? The liner, reinforcement and service life.
Inspection of pipes and hoses
Look for cracks, dents, flattened bends, corrosion and chafing on rigid tubing. Inspect hose covers for cuts, blisters, hardening, softening, heat damage, leakage and exposed reinforcement. Check end fittings, support security and separation from moving components. Some defects require replacement even before leakage develops. Apply the actual damage criteria and life limits. A hose that appears dry may have internal deterioration; visual inspection does not cancel an established replacement interval.
Which hose defect requires assessment under the maintenance limits? Blistering, exposed reinforcement or leakage.
Cleanliness and testing
Cap open lines with clean approved caps and prevent foreign material from entering. Flush, pressure test or leak check using the specified fluid, pressure, duration and precautions. Stored pressure can release violently; depressurise as instructed before disconnecting. Never seek a high-pressure hydraulic leak with a bare hand, because a fine jet can penetrate skin. Test acceptance includes the required pressure and leakage limits as well as fitting condition. Restore the system and remove all temporary caps and equipment.
Why must a hydraulic leak not be checked by hand? A high-pressure jet can inject fluid through skin.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A rigid line aligns only after pulling it sideways. What is the correct response?
Correct the alignment using approved data — Installation stress can lead to fatigue and leakage.
A hose stripe spirals after installation. What should be investigated?
Twist in the hose — A longitudinal stripe helps reveal hose twisting.
A replacement fitting has the same thread but a different flare angle. What is appropriate?
Use the specified compatible fitting — Thread engagement does not establish sealing-surface compatibility.
An open hydraulic line is left uncapped during nearby drilling. What is the main concern?
Internal contamination by chips and debris — Clean caps and work-area control protect the system from contamination.