Questions and Answers
What color is an AN steel flared tube fitting?
What must be fitted to an AN bulkhead flared tubing fitting to achieve a fluid-tight seal?
In which direction is a sleeve on an MS flare less fitting permitted to move?
What is the primary advantage of a Banjo fitting in aircraft fluid systems?
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When fitting a reusable fitting to a flexible fluid line, what is the allowed clearance between the nut and the socket?
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What is a disadvantage of using copper tubing in aircraft?
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Which aluminium alloy is specifically used for fluid lines requiring higher strength?
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How can the aluminium alloy of a piece of alloy tubing be identified?
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What material is recommended for tubing in high pressure (3,000 psi) systems?
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What dimensions are indicated on the outside of a solid piece of tubing?
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What type of rigid pressure lines would typically use a beaded fitting?
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When should a flexible pipe be used in aircraft systems?
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What must be observed when a Teflon preformed hose is removed for maintenance?
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How much extra slack must be allowed for when manufacturing a flexible hose?
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What is typically done to hoses, fittings, and lines when they are disconnected for maintenance?
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What type of steel is usually used for tubing capable of handling over 3000 psi?
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Which compound is usually used in flexible hoses carrying Skydrol or petroleum-based products?
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How is the diameter of rigid tubing measured?
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What is the purpose of a lay line on a flexible fluid hose?
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What kind of fitting is required for hydraulic high pressure lines?
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What is the maximum allowed offset when mating two beaded fittings?
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What identification letters indicate a rigid fluid line containing a physically dangerous material?
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What is the flare angle used on aircraft tubed flaring?
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What is done to prevent contaminants from entering a removed fluid line?
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When would a double flare be used?
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What seals a banjo fitting from leaking?
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How is beading formed on a metal tube?
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What process is used to attach the sleeve on an MS flare less tube fitting to the tube?
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What type of tubing is classified as suitable for MS flare less fittings?
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When using a quick disconnect adapter on an aircraft, which of the following services is NOT commonly associated with it?
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What is the allowed axial movement direction for a sleeve on an MS flare less fitting?
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What is the acceptable clearance between the nut and the socket when fitting a reusable fitting to a flexible fluid line?
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What material is preferred for constructing tubing in high-pressure systems?
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What identifies the aluminium alloy in a piece of alloy tubing?
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What is the primary purpose of a lay line on a flexible hose?
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In which situation would you utilize a flexible hose in an aircraft fluid system?
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How is the diameter of a flexible fluid line measured?
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What type of fittings are used with large-diameter lines carrying low-pressure fluids?
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What happens to copper tubing used in aircraft when subjected to vibrations?
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Which types of inner liners are suitable for carrying Skydrol hydraulic fluid?
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What process must be followed when a flexible hose is removed for maintenance to ensure it retains its integrity?
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What is the purpose of applying metal blanks to a fluid line that is disconnected?
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What method is used to identify the contents of a rigid fluid line subjected to extreme temperatures?
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What distinguishes an AN flared fitting from an AC flared fitting?
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What is the maximum allowed angular deviation when mating two beaded fittings?
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Which of the following is a characteristic of a flareless fitting?
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When manufacturing a flexible hose, what is the standard percentage of slack that must be added?
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What compound is typically used to line flexible hoses carrying petroleum-based products?
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What should be done to hoses, fittings, and lines when they are disconnected for maintenance?
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What is measured to determine the size of a flexible high-pressure hose?
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What is the typical flare angle used in aircraft tubed flaring?
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What material is usually used to manufacture rigid tubing designed for high pressures?
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What is the recommended action for a hose that is temporarily removed during maintenance?
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What identifies a rigid fluid line carrying dangerous materials?
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Study Notes
Tubing Materials and Properties
- Copper tubing becomes hard and brittle when subjected to vibration, making it less suitable for aircraft applications.
- The aluminium alloy 3003-H14 is commonly used for fluid lines requiring higher strength.
- Corrosion-resistant steel tubing, either annealed or quarter-hard, is utilized in high-pressure systems (up to 3,000 psi).
- A softer aluminium alloy, pure 1100, is used for low-pressure applications, such as instrument or ventilating air tubing.
Tubing Identification and Measurement
- The diameter of a flexible fluid line is measured by its inner diameter in 1/16th inch increments.
- Rigid tubing is measured by its outer diameter, and dimensions printed on the outside typically include both the diameter and wall thickness.
- Identification of tubing alloy is indicated by colored bands on both the ends and mid-section of the tubes.
Flexible Hose Applications
- Flexible hoses are used to connect moving parts with stationary parts in areas prone to vibration or requiring extensive flexibility.
- The lay line ensures that a properly installed hose runs straight without twists, serving as a visual guide during installation.
- Teflon and Butyl liners are suitable for carrying Skydrol hydraulic fluid.
- It is crucial to avoid bending a preformed Teflon hose outside its designated shape during maintenance.
Hose Manufacturing and Maintenance
- When manufacturing flexible hoses, allow an extra 5-8% slack in the hose length.
- Hoses, fittings, and lines must be blanked off when disconnected for maintenance to prevent contamination.
- Metal blanks are required for lines that must maintain full system pressure when not connected.
Fittings and Connectors
- Aircraft tubing flaring uses a 37-degree flare angle.
- A double flare is typically employed for high-pressure installations.
- AN fittings are identified by a blue or black color, using a 37-degree angle and coarser threads with a shoulder and recess.
- AN and AC fittings can be differentiated by their color and thread appearances, with AN steel fittings being black.
Special Fittings
- Banjo fittings are sealed using O-rings or aluminium gaskets, preventing leaks in fluid systems.
- Quick disconnect fittings are suitable for Ground Support Equipment (GSE) applications.
- Flareless fittings are used in hydraulic high-pressure lines to enhance reliability.
- The sleeve in a flareless fitting should move axially but remain stationary radially, with pre-setting ensuring a secure fit.
General Tips and Requirements
- When using beaded fittings for large-diameter lines carrying low-pressure fluids, ensure compliance with maximum allowable offset (1/16-inch) and angular deviations (3 degrees).
- Steel tags can identify the contents of rigid fluid lines facing extreme temperatures.
- For AN bulkhead flared tubing fittings, crush washers or synthetic seals are required for a fluid-tight connection.
- Ensure a clearance of 1/32 to 1/16 inch between the nut and socket when fitting a reusable fitting to a flexible fluid line.
Tubing Materials and Properties
- Copper tubing becomes hard and brittle when subjected to vibration, making it less suitable for aircraft applications.
- The aluminium alloy 3003-H14 is commonly used for fluid lines requiring higher strength.
- Corrosion-resistant steel tubing, either annealed or quarter-hard, is utilized in high-pressure systems (up to 3,000 psi).
- A softer aluminium alloy, pure 1100, is used for low-pressure applications, such as instrument or ventilating air tubing.
Tubing Identification and Measurement
- The diameter of a flexible fluid line is measured by its inner diameter in 1/16th inch increments.
- Rigid tubing is measured by its outer diameter, and dimensions printed on the outside typically include both the diameter and wall thickness.
- Identification of tubing alloy is indicated by colored bands on both the ends and mid-section of the tubes.
Flexible Hose Applications
- Flexible hoses are used to connect moving parts with stationary parts in areas prone to vibration or requiring extensive flexibility.
- The lay line ensures that a properly installed hose runs straight without twists, serving as a visual guide during installation.
- Teflon and Butyl liners are suitable for carrying Skydrol hydraulic fluid.
- It is crucial to avoid bending a preformed Teflon hose outside its designated shape during maintenance.
Hose Manufacturing and Maintenance
- When manufacturing flexible hoses, allow an extra 5-8% slack in the hose length.
- Hoses, fittings, and lines must be blanked off when disconnected for maintenance to prevent contamination.
- Metal blanks are required for lines that must maintain full system pressure when not connected.
Fittings and Connectors
- Aircraft tubing flaring uses a 37-degree flare angle.
- A double flare is typically employed for high-pressure installations.
- AN fittings are identified by a blue or black color, using a 37-degree angle and coarser threads with a shoulder and recess.
- AN and AC fittings can be differentiated by their color and thread appearances, with AN steel fittings being black.
Special Fittings
- Banjo fittings are sealed using O-rings or aluminium gaskets, preventing leaks in fluid systems.
- Quick disconnect fittings are suitable for Ground Support Equipment (GSE) applications.
- Flareless fittings are used in hydraulic high-pressure lines to enhance reliability.
- The sleeve in a flareless fitting should move axially but remain stationary radially, with pre-setting ensuring a secure fit.
General Tips and Requirements
- When using beaded fittings for large-diameter lines carrying low-pressure fluids, ensure compliance with maximum allowable offset (1/16-inch) and angular deviations (3 degrees).
- Steel tags can identify the contents of rigid fluid lines facing extreme temperatures.
- For AN bulkhead flared tubing fittings, crush washers or synthetic seals are required for a fluid-tight connection.
- Ensure a clearance of 1/32 to 1/16 inch between the nut and socket when fitting a reusable fitting to a flexible fluid line.
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Description
Explore the key materials and properties of various tubing suitable for different applications, particularly in aircraft systems. Learn about the advantages of copper, aluminium alloys, and corrosion-resistant steel. Understanding tubing identification and measurement is crucial for effective implementation in engineering contexts.
