Podcast
Questions and Answers
What type of cutting tool for Sheet Metal Construction and Repair have straight blades with cutting edges sharpened to an 85° angle?
What size of the rivet do we need to join these 2 pieces of metal?
RD = 5/32, RL = 5/16
What is measured from the rivet center to the rivet center?
A well designed rivet joint will subject the rivets to compressive loads.
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Match the following rivet head types with their descriptions:
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What is the primary purpose of refrigerating 2017 and 2024 aluminum alloy rivets after heat treatment?
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What is one purpose of a fuel tank vent?
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Which gas is used for purging an aircraft fuel tank?
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A capacitance type fuel quantity indicating system measures fuel in
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To prevent vapor lock in fuel lines at high altitude, some aircraft are equipped with
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The pole pieces or shoes used in a DC generator are a part of the:
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Aircraft fuse capacity is rated in
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What are antiskid generators used for?
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What are composite materials with high temperature applications made of?
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Kevlar composite has __ times better tensile strength than aluminum.
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Match the following fiber orientations with their descriptions:
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What is the method used for detecting cracks in metallic surfaces?
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What is the composite component repair method that uses heat gradients to detect flaws?
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What is the method that features the use of a laser light source for inspection?
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Study Notes
Aircraft Maintenance Technology
- Metallic Structures (Sheet Metal):
- Uses stressed skin to support almost all loads
- Consists of determining the number of rivets required, style of rivet to be used, material temper condition and strength, distance of rivet holes, and spacing of rivets throughout the repair
- Filler patch is flush to the skin when applied, supported by and riveted to a reinforcement plate, which is riveted to the inside of the skin
- Cutting Tools for Sheet Metal Construction and Repair:
- Straight snips or sheet metal shears with straight blades and cutting edges sharpened to an 85° angle
- Available in sizes ranging from 6 to 14 inches, can cut aluminum up to 1/16 of an inch
- Can be used for straight cutting and large curves
- Rivet Joint:
- A well-designed rivet joint will subject the rivets to shear loads
- Rivet gauge or transverse pitch is the distance between the center of adjacent rivets in the same row
- Aluminum Alloys:
- 2024-T36 alloy has copper as its primary alloying agent
- Annealing of aluminum removes stresses caused by forming
- Rivet Types:
- Flat Head Rivet (AN442): used throughout the interior aircraft structure where special rivets are not required
- Round Head Rivet (AN430): used for applications where countersinking is not required
- Brazier Head Rivet (AN455): used where high shear strength and resistance to vibration are required
- Layout Tools for Sheet Metal Construction and Repair:
- Consists of a steel scale with three heads that can be moved to any position on the scale and locked in place
- Heads include a stock head that measures 90° and 45° angles, a protractor head that can measure any angle, and a center head that uses one side of the blade as the bisector of a 90° angle
- Marking Tools for Sheet Metal Construction and Repair:
- Graphite pencils should not be used on aluminum as they can cause corrosion
- Preferred method of marking lines and hole locations directly on aluminum is with a scribe or marker
Aircraft Structures
- Semi-Monocoque Fuselage:
- Longitudinal structural members are called longerons and stringers
- Relies largely on the strength of skin or covering
- Monocoque Fuselage:
- Relies largely on the strength of skin or covering
- Helicopter Controls:
- Movement about the longitudinal axis (roll) is effected by cyclic pitch control
- Movement about the lateral axis (pitch) is effected by collective pitch control
- Movement about the vertical axis (yaw) is effected by tail rotor pitch control
Landing Gear
- Shock Strut:
- Should be checked for proper extension and compression
- Should be checked for signs of damage or wear
- Torque Links:
- Limit compression stroke and maintain correct wheel alignment
Hydraulic Systems
- Pressure Regulator:
- Maintains system operating pressure within a predetermined range
- Unloads the pump
- Fluid:
- MIL-H-8446 (Skydrol 500 A & B) is a phosphate ester base, fire-resistant fluid
- Compatible with natural rubber seals and packings
- Instruments:
- Pitot static system connects to airspeed indicator, altimeter, and vertical speed indicator
Avionics and Electrical Systems
- Autopilot:
- Fully integrated autopilot controls the aircraft around three axes
- Antenna Installation:
- Must be grounded to the airframe
- Radio Signals:
- VHF signals are commonly used in ATC communications
- Dutch Roll:
- Counteracted with a yaw damper system
Fuel Systems
- Fuel Tank System:
- Allows all tanks to be serviced through a single connection
- Any engine can be fed from any tank
- All engines can be fed from all tanks simultaneously
- A damaged tank can be isolated from the rest of the fuel system
- Fuel Tank Vent:
- Prevents bubble formation in the fuel after it leaves the tank when atmospheric pressure is lower than fuel vapor pressure
- Fuel Quantity Indicating System:
- Measures fuel in pounds
- Fuel Purging:
- Helium or argon gas is used to purge an aircraft fuel tank
Non-Metallic Structures (Composite)
- Reinforcing Materials:
- Carbon/Graphite Fiber: used when high temperature application is needed
- Ceramic Fiber: used when high temperature application is needed
- Composite Properties:
- Fatigue resistance: Fiberglass Fiber has high fatigue resistance
- Tensile strength: Kevlar composite has higher tensile strength than aluminum
- Fiber Orientation:
- Unidirectional: all major fibers run in one direction, giving strength in that direction
- Bi-directional: fibers run in two directions, giving strength in both directions
- Resin Types:
- Thermoplastic: can be reheated and reformed
- Thermoset: cannot be reheated and reformed
- Surface Attachments:
- Adhesives: used to bond composite parts together
- Additives: used to improve the properties of the resin
- Manufacturing Methods:
- Hand or Wet Layup: most widely accepted form of applying composite materials
- Fitament Winding: used for parts with a circular cross-section
- Fiber Placement or Tape Laying: used for complex shapes
- Curing Methods:
- Heat Curing: uses heat to cure the resin
- Room Temperature Curing: uses a catalyst to cure the resin at room temperature
- Ramp and Soak Curing: uses a controlled temperature and pressure to cure the resin
Composite Repair
- Damage Detection:
- Visual inspection: detects cracks, delamination, and cosmetic damage
- Infrared inspection: detects temperature variations at the surface of a damaged part
- Laser inspection: uses a laser light source and an infrared camera to detect cracks and delamination
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Description
This quiz covers the concepts of metallic structures in aircraft maintenance, including stressed skin, rivet requirements, materials, and more.
