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Questions and Answers
Which rotor blade design has a better aerodynamic pitch characteristic?
Which rotor blade design has a better aerodynamic pitch characteristic?
What feature of asymmetrical rotor blades allows them to achieve similar aerodynamic stability to symmetrical blades?
What feature of asymmetrical rotor blades allows them to achieve similar aerodynamic stability to symmetrical blades?
Why are symmetrical rotor blades more commonly used than asymmetrical blades?
Why are symmetrical rotor blades more commonly used than asymmetrical blades?
Which rotor blade planform has a leading and trailing edge that run parallel to each other?
Which rotor blade planform has a leading and trailing edge that run parallel to each other?
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Why do manufacturers prefer to produce uniform planform blades?
Why do manufacturers prefer to produce uniform planform blades?
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Why do parallel blades have a negative twist from root to tip?
Why do parallel blades have a negative twist from root to tip?
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What is a benefit of using bonded construction for rotor blades?
What is a benefit of using bonded construction for rotor blades?
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How many trim balance weights are typically used on a rotor blade?
How many trim balance weights are typically used on a rotor blade?
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What is the purpose of the stainless steel capping on the leading edges of rotor blades?
What is the purpose of the stainless steel capping on the leading edges of rotor blades?
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Why are the bottom surfaces of rotor blades often painted flat black?
Why are the bottom surfaces of rotor blades often painted flat black?
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Which type of rotor blades are required to have static discharge capabilities?
Which type of rotor blades are required to have static discharge capabilities?
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What is the primary inspection method used for composite rotor blades?
What is the primary inspection method used for composite rotor blades?
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Where are spanwise balance weights typically located on a rotor blade?
Where are spanwise balance weights typically located on a rotor blade?
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If weight is added to the leading edge of a rotor blade, what effect will it have on the helicopter?
If weight is added to the leading edge of a rotor blade, what effect will it have on the helicopter?
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How should you bend a trim tab to make the rotor blade fly lower in its plane of rotation?
How should you bend a trim tab to make the rotor blade fly lower in its plane of rotation?
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What is the first control that should be rigged when working on a helicopter?
What is the first control that should be rigged when working on a helicopter?
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What action is crucial before connecting the collective and throttle?
What action is crucial before connecting the collective and throttle?
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What is the correct sequence for testing a helicopter after rigging?
What is the correct sequence for testing a helicopter after rigging?
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Where is the servo tab located on a rotor blade?
Where is the servo tab located on a rotor blade?
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What is a primary function of the main servo flap?
What is a primary function of the main servo flap?
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In what order are the flight controls rigged?
In what order are the flight controls rigged?
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Which system is considered more complex, a droop compensator or a correlator?
Which system is considered more complex, a droop compensator or a correlator?
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What is the primary function of the droop compensator?
What is the primary function of the droop compensator?
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What is the purpose of the correlator?
What is the purpose of the correlator?
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Study Notes
Rotor Blade Designs
- Two main rotor blade designs exist: symmetrical and asymmetrical.
- Symmetrical blades have better aerodynamic pitch characteristics.
- Asymmetrical blades generate greater lift for the same surface area, with higher camber on one side.
- Engineers achieve similar pitching characteristics in asymmetrical blades by sweeping the edges by 3 degrees upwards to achieve aerodynamic stability.
- Symmetrical blades are the most common design due to the asymmetrical blade's unstable aerodynamic characteristics.
- Two planform types exist: parallel (uniform) and tapered.
- Uniform planforms have leading and trailing edges parallel to each other.
- Uniform platforms generate greater lift due to their chord line.
- Tapered planforms have a converging leading and trailing edge, and decreasing chord length towards the blade root.
Manufacturing Preferences
- Manufacturers prefer uniform platforms due to cost-effectiveness.
- Uniform designs utilize a single machine stamping for ribs, as the chord line doesn't change, and only one rib part number is required.
- Tapered blade planforms require different rib numbers for each rib due to varying chord length.
- Tapered designs provide more equal lift across the blade due to accommodating variations in speed.
Blade Twist
- Parallel blades have a negative twist to achieve a higher angle of attack (AOA) at the root and compensate for slower blade spinning at the tip, ensuring equal lift across the blade's entire length.
Skin Configurations
- Single-pocket skin configurations are faster to build due to using one large skin.
- Multi-pocket skin configurations are easier to repair, as damaged skins can be replaced without affecting the entire structure.
Maintenance
- Replacing damaged skins is preferable for multi-pocket configurations.
- With single-pocket configurations, damage often leads to the entire skin's replacement.
Weight Balancing
- It is not possible to move chord line mass balance weights.
- Trim balance weights (two, typically) are adjustable only during repairs.
- Adding weights forward alters the blade's position downward in rotation
- Adding weights aft alters the blade's position upward in rotation.
Blade Tab Adjustments
- Adjusting trim tabs upwards will cause the blade to fly higher in its rotational plane
- Adjusting trim tabs downwards will cause the blade to fly lower in its rotational plane
Rotor Blade Materials
- Composite materials, metal, and wood are common rotor blade materials.
Blade Inspection
- Tap testing is a primary method for inspecting composite rotor blades.
Rotor Blade Construction
- Bonded construction techniques are preferred due to improved strength and prevention of drilling holes.
Vibration Mitigation
- Bifilar and hub vibration absorbers utilize various mechanical and construction methods to reduce noise and vibration during operation.
Helicopters
- Collective rigging happens first before performing other flight controls rigging on a helicopter.
- Turning off hydraulics, and ensuring no residual pressure remains in the hydraulic system, before rigging, helps avoid hydraulic malfunction.
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Description
Explore the intricacies of rotor blade designs, including the differences between symmetrical and asymmetrical shapes. Learn about the aerodynamic characteristics, planform types, and the manufacturing preferences of engineers in this field.
