7.9 Pipes and Hoses Flashcards
What are the four processes of pipe forming?
Cutting, Bending, Flaring, Belling
What is the primary purpose of piping in aircraft systems?
To carry fluids between different points
How is metal piping sized?
By Outside Diameter (OD), measured in 16ths of an inch
Which pipes can be bent by hand?
Pipes below ¼ in OD
What tool is primarily used for cutting aircraft pipes?
Pipe cutter
What should be done if a pipe cutter is not available?
Use a hacksaw with a fine tooth, preferably 32 TPI
How much longer should piping be cut compared to the required length?
10% longer
What must be done to the end of the pipe after cutting?
Deburred with a deburring tool or fine-tooth file
What is the objective in pipe bending?
To obtain a smooth bend without flattening the pipe
What is typically used to bend pipes of ¼ in diameter and above?
Portable hand benders or production benders
What should be done before bending a pipe?
Lightly lubricate the pipe at the bend point
What is the standard flare angle for aircraft flared fittings?
37°
What are the two types of flare used in aircraft piping systems?
Single flare, Double flare
Fill in the blank: The cutting wheel of a pipe cutter must align with the _______.
mark showing where the cut is to be made
True or False: Vehicle-type flares with a 45° flare angle can be used on aircraft.
False
What must all pipe ends to be flared be before flaring?
Fully deburred and square
What does the sleeve in a flare-type fitting do?
Provides added strength and supports the pipe
What is the consequence of excessive flattening in pipe bends?
Fatigue failure of the pipe
What type of tool is used to form a single flare?
Impact-type flaring tool or one with a flaring cone
What is the purpose of deburring the end of the pipe before flaring?
To prevent small cracks forming
What is the recommended action when bending pipes to ensure they fit exactly?
Fabricate the pipe bend at the installation site
What happens if the wall thickness of the pipe is damaged during deburring?
It can lead to fractured or defective flares
What is the acceptable percentage of the original outside diameter for a flattened portion in bends?
Not less than 75%
What is a single flare?
A single flare is formed with either an impact-type flaring tool or one having a flaring cone with a rolling action.
What method does an impact-type flaring tool use?
The piping is clamped in flaring blocks while a plunger is driven into the end of the pipe using light hammer blows while rotating the plunger.
What angle is required for a 37° flare at the hydraulic pipe end?
The required angle for a 37° flare is produced using manual flaring tools.
How is a single flare produced using tools?
The flare is produced by clamping the pipe flush in the block halves and hammering the flare pin.
What is the preferred method for producing single flares?
The roll-type method, involving an entirely self-contained unit producing a good flare.
What is the function of the flaring cone in roll-type flaring tools?
The flaring cone is turned into the pipe end, expanding the flare until it reaches the edges of the die.
What are the dimensions for single flare piping for a 1/4 inch pipe OD?
External Sleeve Diameter: 0.359 in, B Radius: +0.000, -0.010: 0.032.
What type of piping can be double flared?
Soft aluminium piping with an outside diameter of 3/8 in or smaller.
What is the advantage of a double flare compared to a single flare?
A double flare is smoother, more concentric, provides a better seal, and is more durable.
What is the first step in the procedure for double flaring?
The piping is inserted into the flaring die to a depth determined by the stop-pin and then clamped.
What is a Harrison-type fitting?
A connection that requires a special tool to mould a sleeve by widening the pipe.
What is the main advantage of a Permaswage fitting?
It can be made quickly in time-sensitive situations, is light, and gives a good seal.
What is the disadvantage of a Permaswage fitting?
It cannot be separated, which can be problematic during disassembly.
What is the purpose of belling pipes?
To connect ridged piping lines carrying low-pressure fluids or air to rubber hoses.
What tool is required for belling piping with an outside diameter over 1 inch?
A power beading machine is required for piping over 1 inch.
Fill in the blank: The bead for belling is formed by a _______.
beading frame with rollers.
How is lubrication applied when using a hand belling tool?
The inside and outside of the pipe are lubricated with light oil to reduce friction.
Why do aircraft pipes and hoses need to be tested?
To ensure safety and reliability in aircraft systems
Testing helps prevent failures that could lead to accidents.
What are the main applications of pipes in aircraft?
Hydraulic control, fuel, oil, oxygen, and instrument systems
Pipes are mainly used in stationary applications with long, straight runs.
What are the characteristics of flexible hoses in aircraft?
Used with moving parts and in areas subject to vibration
They are essential for connecting stationary to moving components.
What materials are modern aircraft pipes typically made from?
Non-corrosive steels, aluminium, and titanium alloys
These materials enhance durability and safety.
What are the classifications of pressure lines in aircraft?
- High-pressure lines: over 1500 psi (105 bar)
- Medium-pressure lines: below 1500 psi (105 bar)
- Low-pressure lines: suction and return lines
In which aircraft areas must pipelines be made of steel?
Engine area and landing gear area
This is due to fire hazards and the risk of Foreign Object Damage (FOD).
What is the purpose of rubber covers on pipes?
To protect pipes from Foreign Object Damage (FOD)
They help extend the life of the pipes.
What materials are used to manufacture aircraft hoses?
Synthetic rubber and Polytetrafluoroethylene (PTFE)
PTFE is chemically inert and can withstand high temperatures.
What is a significant property of PTFE hoses?
Chemically inert and unaffected by synthetic oils and fluids
PTFE hoses have a long shelf life but require careful handling.
What is the purpose of high tensile steel wire braiding in hoses?
Provides maximum resistance to bursting and minimizes dimensional changes
This is crucial for maintaining hose integrity under pressure.
What type of repairs are not permitted for aircraft engine pipes?
Repairs are not permitted; engine pipes must always be replaced
This ensures safety and reliability in critical systems.
What can be done with minor dents and scratches in aluminum alloy piping?
They may be repaired by blending with hand tools
Damage limits apply; consult the aircraft maintenance manual.
What is the maximum allowable depth for sharp-bottomed surface defects?
5% of the pipe’s wall thickness
Sharp-bottomed traces of impact are not permitted.
What are the three types of hose ratings based on pressure?
- Low pressure: up to 600 psi (4137 kPa)
- Medium pressure: up to 3000 psi (20 685 kPa)
- High pressure: 3000 psi or over (20 685 kPa or over)
What is the purpose of lay lines on hoses?
To indicate whether the assembly is twisted during installation
They also identify the hose and provide manufacturer information.
What is the procedure for cleaning a hose assembly before testing?
Clean out internally with compressed air blown from both directions alternately
This ensures no debris affects the testing process.
What checks must be performed before installing a hose?
- Applicability
- Length
- Cleanliness
- Damage
What should be avoided to prevent undue strain on hoses during installation?
Twisting the hose
Lay lines should be checked to ensure proper orientation.
What materials are used for protective sleeves on hoses?
- Heat shrink
- Nylon spiral wrap
- Teflon
What is essential during the inspection of aircraft pipes and hoses?
Look for signs of leaks and chafing
Any leak, however small, must be investigated thoroughly.
True or False: Minor repairs are allowed on engine pipes.
False
Engine pipes must always be replaced for safety.
What must fluid lines in aircraft be secured with?
Appropriate clamps
All fluid lines must follow structural members of the aircraft.
What are the two most commonly encountered clamps for fluid lines?
- Rubber cushioned clamp
- Plain clamp
What is the purpose of a rubber cushioned clamp?
Secures lines subject to vibration and prevents chafing
What type of clamp is used for metal fuel, oil, or hydraulic lines?
Bonded clamp
What must be removed from the line where a bonded clamp is fitted?
Any paint or anodising
What is essential to prevent leaks from pipe and hose assemblies?
Adherence to specific torque figures from the Aircraft Maintenance Manual (AMM)
What is the recommended lubricant for O-rings during assembly?
Specified hydraulic fluid
What should be inspected before tightening connections?
- Contamination
- Damage
- Sealing surfaces
What is the maximum allowable force to correct pipe alignment during installation?
Light finger pressure (1 daN)
True or False: Lubricant should be applied on the contact surfaces between the sleeve and the fitting.
False
What must be done to a hydraulic fitting after it has been torqued?
Apply a witness mark with red paint
What is the minimum bend radius for hoses determined by?
- Operating pressure
- Type of hose
- Nominal size
What should be done if a hose assembly is twisted during fitting?
Avoid twisting to prevent undue strain
What is the role of support clamps for fluid lines?
Prevent chafing and reduce stress
Fill in the blank: All fluid lines must not chafe against _______.
Control cables or aircraft structure
What are the checks to carry out before installing a flexible hose?
- Applicability
- Length
- Cleanliness
- Damage
What is the importance of having bends in pipe installations?
To absorb flexing and expanding forces due to thermal expansion and pressure
What should be done if a leak is present after testing the system at operational pressure?
Tighten the nut an additional flat
What is the maximum pressure that pipes must be tested at after installation?
Operational pressure
