Rotor Blade Design Overview
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Questions and Answers

Which rotor blade design provides a better aerodynamic pitch characteristic?

  • Uniform
  • Symmetrical (correct)
  • Asymmetrical
  • Tapered

Which rotor blade design generates greater lift for the same surface area?

  • Parallel
  • Tapered
  • Asymmetrical (correct)
  • Symmetrical

How do engineers stabilize the aerodynamic characteristics of an asymmetrical rotor blade?

  • By reducing the camber
  • By sweeping the edges 3 degrees upwards (correct)
  • By increasing the thickness of the blade section
  • By using a uniform planform

What is the most common type of rotor blade design?

<p>Symmetrical, because of aerodynamic stability (A)</p> Signup and view all the answers

Which rotor blade planform has a leading and trailing edge that run parallel to each other?

<p>Uniform (D)</p> Signup and view all the answers

Why do manufacturers prefer to produce uniform blade planforms?

<p>Because they decrease complexity in rib production (A)</p> Signup and view all the answers

What is a characteristic of a single-pocket skin configuration?

<p>It uses one large skin (D)</p> Signup and view all the answers

Where are trim balance weights added to a rotor blade?

<p>Two at the tip of the rotor blade (C)</p> Signup and view all the answers

What is the primary purpose of the flat black paint on the bottom of rotor blades?

<p>To prevent glare in the pilot's vision. (A)</p> Signup and view all the answers

Which type of rotor blades are required to have static discharge abilities?

<p>Composite blades (C)</p> Signup and view all the answers

Where are spanwise balance weights typically located on a rotor blade?

<p>At the blade tip on the spanline (C)</p> Signup and view all the answers

Which action will cause a rotor blade to fly higher in its plane of rotation?

<p>Adding weight to the trailing edge of the blade (A)</p> Signup and view all the answers

What is the purpose of stainless steel capping on the leading edges of rotor blades?

<p>To provide erosion protection (A)</p> Signup and view all the answers

Which rigging component needs to be set up first when working on a helicopter?

<p>Collective (A)</p> Signup and view all the answers

What is the effect of bending the trim tab lower on a rotor blade?

<p>It will cause the blade to fly higher in its plane of rotation (A)</p> Signup and view all the answers

What is the purpose of the correlator in a helicopter's control system?

<p>It connects the collective to the throttle (B)</p> Signup and view all the answers

What should be confirmed before connecting the collective and throttle?

<p>The throttle and collective are rigged independently (A)</p> Signup and view all the answers

What is the final flight test completed on a helicopter after rigging?

<p>An autorotational check at minimum gross weight (D)</p> Signup and view all the answers

Where is a servo tab typically located on a rotor blade?

<p>Approximately 75 percent of the span, on the trailing edge (C)</p> Signup and view all the answers

What primary function does the main servo flap serve?

<p>Removing the need for a hydraulic system (D)</p> Signup and view all the answers

In what order should flight controls be rigged?

<p>Collective, cyclic, anti-torque pedals (C)</p> Signup and view all the answers

Which system is more complex on a helicopter, a droop compensator or correlator?

<p>The droop compensator system (D)</p> Signup and view all the answers

What type of airfoil is a fixed elevator on a helicopter?

<p>An inverted airfoil that generates lift in a downwards direction (B)</p> Signup and view all the answers

Flashcards

Symmetrical Blade Design

A blade design with equal lift distribution on both sides.

Asymmetrical Blade Design

A blade design with unequal lift distribution on both sides, resulting in higher lift on the side with greater camber.

Uniform Planform

A blade design with a uniform chord length from root to tip.

Tapered Planform

A blade design with a decreasing chord length from root to tip, narrowing towards the tip.

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Single Pocket Skin Configuration

A construction technique for rotor blades using a single piece of skin wrapping around the entire blade.

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Multi-pocket Skin Configuration

A construction technique for rotor blades using multiple pieces of skin for different sections of the blade.

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Trim Balance Weight

A weight used to adjust the balance and trim of the rotor blade, located at the tip.

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Bonded Construction

A construction technique for rotor blades that eliminates the need for drilling holes, resulting in a stronger, more robust blade.

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Weight Aft of Trim Tabs

Adding weight aft of the trim tabs will cause the rotor blade to travel higher in its plane of rotation. This is because the added weight shifts the center of gravity further back, making the blade less stable and causing it to move upwards.

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Stainless Steel Capping on Rotor Blades

The leading edges of all rotor blades are capped with stainless steel to protect them from erosion caused by small dust particles in the air during flight. This erosion can damage the blades and reduce their lifespan.

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Black Underside of Rotor Blades

The underside of rotor blades is often painted flat black to prevent glare reflecting into the pilot's vision. This helps maintain clear visibility during flight, especially in bright sunlight.

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Static Discharge in Composite Blades

Composite rotor blades require static discharge abilities to prevent the buildup of static electricity, which can disrupt flight operations and potentially cause damage. Static discharge helps dissipate the electricity safely.

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Rotor Blade Materials

Composite, metal, and wood are the most common materials used for constructing rotor blades. Each material has its own advantages and disadvantages in terms of strength, weight, and cost.

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Tap Testing Composite Blades

Tap testing is a primary inspection method for composite rotor blades. It involves tapping the blade to listen for any signs of damage or delamination. The sound and feel of the tap can indicate the condition of the blade.

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Multi-Pocket Blade Skin

Multi-pocket blade skin configurations are more expensive to build compared to single-pocket designs due to increased complexity and the need for more intricate manufacturing processes.

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Double Plates at Blade Root & Tip

Double plates at the root and the tip of the rotor blade increase structural strength without adding significant weight. This helps to improve blade stability, reduce vibrations, and enhance overall performance.

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Servo Flap

A small airfoil located on the trailing edge of each rotor blade, at about 75 percent span, designed to optimize aerodynamic response to control inputs.

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Rigging Flight Controls

The process of adjusting the helicopter's flight controls to ensure proper operation and responsiveness.

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Droop Compensator

A mechanical linkage that automatically adjusts the engine power output based on changes in blade pitch, preventing lag in response.

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Correlator

A mechanical linkage that connects the collective pitch lever to the throttle, allowing for simultaneous control of both.

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Bifilar Vibration Absorber

A vibration suppression system that uses two sets of four-arm disks to absorb and dissipate vibrations from the rotor system.

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Hub Vibration Absorber

A vibration suppression system that uses a weighted drum supported by springs to absorb and dissipate vibrations from the rotor system.

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Force Trim System

A system that assists in returning the cyclic control to its neutral position through the use of a spring.

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Elevator

A horizontal airfoil located at the tail of the helicopter, used to adjust the pitch angle and maintain a level flight attitude.

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Study Notes

Rotor Blade Designs

  • Two main designs: symmetrical and asymmetrical
  • Symmetrical blades have better aerodynamic pitch characteristics
  • Asymmetrical blades produce more lift for the same surface area
  • Asymmetrical blades have greater camber on one side

Blade Design Characteristics

  • Asymmetrical blades are achieved by sweeping the edges 3 degrees upwards, aiding aerodynamic stability
  • Symmetrical blades are most common due to asymmetrical blades' unstable aerodynamic characteristics
  • Two main planform types: parallel (uniform) and tapered
  • Uniform planform: leading and trailing edges run parallel to each other
  • Tapered planform: leading and trailing edges converge, chord length reduces towards the blade root

Planform Preferences

  • Manufacturers prefer uniform planforms due to cost-effectiveness (single machine stamping).
  • Uneven chord length of tapered planforms necessitates changing rib numbers per rib for each blade.
  • Tapered planforms improve lift equality across the blade, compensating for speed variations

Blade Twist

  • Parallel blades have a negative twist to achieve higher angles of attack at the root, maintaining equal lift from root to tip despite differing rotational speeds.

Skin Configurations

  • Single pocket is faster to build.
  • Multiple pockets make repairs more manageable and reduce damage from one damaged sheet.
  • Single pocket skin configuration is less easily repaired when damaged.
  • Single pocket skin needs complete replacement if damaged.

Construction Methods

  • Bonded construction is preferred because of strength and lack of drilling holes for fasteners.

Rotor Blade Weights

  • Trim balance weights are not movable while the helicopter is in flight; they can be repositioned during repairs
  • Weights added to the leading edge of the rotor blade lower the helicopter in flight
  • Weights added to the trailing edge raise the helicopter in flight

Trim Tabs

  • Trim tabs improve aerodynamic efficiency for better pitch control.
  • Trim Tabs affect rotor blade flight path
  • Trim tabs adjustments are easily made to control rotor blade flight path

Additional Considerations

  • Static discharge capabilities are required for composite blades
  • Common rotor blade materials include composites, metal, and wood
  • Tap testing is a common inspection method for composite rotor blades
  • Multiple pockets are more expensive to build

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Description

Explore the fundamentals of rotor blade designs, focusing on symmetrical and asymmetrical characteristics. Learn about the aerodynamic implications of different planforms and why manufacturers often prefer uniform designs. This quiz will test your understanding of blade stability and efficiency.

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