Rotor Blade Design Overview
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Questions and Answers

Which rotor blade design has a superior aerodynamic pitch characteristic?

  • Tapered
  • Asymmetrical
  • Parallel
  • Symmetrical (correct)

Which blade design is characterized by a higher camber on one side compared to the other?

  • Asymmetrical (correct)
  • Symmetrical
  • Tapered
  • Uniform

How do engineers achieve a similar pitching characteristic with an asymmetrical blade design?

  • By sweeping the edges upwards 3 degrees (correct)
  • By decreasing the blade's weight
  • By adding a counterweight
  • By increasing the blade's surface area

What is the primary reason symmetrical rotor blades are more commonly used?

<p>Their stable aerodynamic characteristic (D)</p> Signup and view all the answers

Which planform features leading and trailing edges that run parallel to each other?

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

Why do manufacturers prefer the uniform planform for rotor blade production?

<p>It is more cost-effective due to a single rib design. (D)</p> Signup and view all the answers

Which skin configuration is considered easier to repair?

<p>Multi pocket (B)</p> Signup and view all the answers

When can the chord line mass balance weight on a rotor blade be moved?

<p>Only during a repair (C)</p> Signup and view all the answers

What is the primary reason for painting the bottom of rotor blades flat black?

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

Which material is NOT typically used in the construction of rotor blades?

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

What is the most common method used for inspecting composite rotor blades?

<p>Tap testing (B)</p> Signup and view all the answers

What is the effect of adding weight to the leading edge of a rotor blade?

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

What type of rotor blades are required to have static discharge capability?

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

Where are chordwise mass balance weights typically located on a rotor blade?

<p>In the leading edge, 30-50 percent of the span. (C)</p> Signup and view all the answers

Which component is rigged first on a helicopter?

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

What action is required before connecting the collective and throttle?

<p>Verify the throttle is rigged correctly and independently from the collective. (C)</p> Signup and view all the answers

In what order are the flight controls rigged?

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

What is the primary function of the main servo flap?

<p>To reduce the need for hydraulic systems. (B)</p> Signup and view all the answers

Which system is considered more complex?

<p>The droop compensator. (A)</p> Signup and view all the answers

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

<p>Inverted airfoil directing lift downwards. (B)</p> Signup and view all the answers

Which vibration absorbing device uses a weighted drum supported by three springs?

<p>Hub vibration absorber. (C)</p> Signup and view all the answers

What does the correlator do?

<p>It is a mechanical linkage between the collective and the throttle. (C)</p> Signup and view all the answers

How many gradient actuators are present if all flight control systems have force trim?

<p>4 (A)</p> Signup and view all the answers

Flashcards

Symmetrical vs. Asymmetrical Blade Designs

A symmetrical rotor blade has the same aerodynamic properties on both sides, while an asymmetrical blade has a different shape on each side. Examples are seen in the profile of the blade.

Which blade design has a better aerodynamic pitch characteristic?

Symmetrical blades have better aerodynamic pitch characteristics, meaning they are more stable in the air and less prone to tip flutter. This means they need less sweeping to achieve stability.

Which blade design produces greater lift?

Asymmetrical blades are designed with a higher camber on one side than the other, allowing them to generate greater lift for the same surface area. This is due to the asymmetric airfoil shape.

What is a tapered planform?

In a tapered planform, the chord length decreases towards the blade root, resulting in a converging leading and trailing edge. This design helps distribute lift more evenly across the blade, leading to greater efficiency.

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Why are uniform planforms preferred?

Uniform planforms are preferred by manufacturers because they are more cost-effective to manufacture. The constant chord length, means only one rib part number is needed, saving on tooling and materials.

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Why do parallel blades have negative twist?

Parallel blades, also known as uniform planforms, need a negative twist. This is to compensate for the lower speed of the blade root and produce the same amount of lift throughout the blade.

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What are the advantages of bonded construction?

Bonded construction is preferred for its strength and durability, as it eliminates the need for drilling holes, which can weaken the structure. It also results in a smoother, seamless finish.

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Which skin configuration is faster to build?

A single pocket skin configuration is quicker to build because it uses one large piece of skin. It is considered more robust.

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Weight Added Aft of Trim Tabs

Adding weight aft of the trim tabs will cause the helicopter to fly higher in its plane of rotation.

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Rotor Blade Leading Edges

Stainless steel capping is added to leading edges for erosion protection. Dust particles wear away the blade surface during flight.

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Rotor Blade Bottom Paint

The bottom of rotor blades are painted flat black to reduce glare for the pilot's vision.

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Static Discharge on Rotor Blades

Composite rotor blades are designed with static discharge abilities to prevent electrical build-up during flight.

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Rotor Blade Materials

Composite, metal, and wood are the most common materials for rotor blade construction.

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Composite Blade Inspection

Tap testing is the primary method used to inspect for damage on composite rotor blades. It utilizes sound to detect internal defects.

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Rotor Blade Skin Cost

Multi-pocket skin configurations are more costly to manufacture compared to single-pocket designs.

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Double Plates on Blade

Double plates at the root and tip of the blade increase structural strength and stiffness without adding significant weight.

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Rigging the Throttle and Collective

The process of independently adjusting the collective and throttle controls before connecting them together.

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Helicopter Testing

A sequence of tests performed on a helicopter after rigging to ensure proper functionality and safety, starting with ground runs and progressing to full flight.

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Servo Flap

A small airfoil located at roughly 75% of a rotor blade's span, situated on the trailing edge.

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Main Servo Flap

A component on a helicopter rotor blade that eliminates the need for hydraulics and simplifies hub design, while also enhancing stability and efficiency.

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Flight Control Rigging Order

The correct sequence for adjusting a helicopter's flight controls: Collective is adjusted first, then Cyclic, and finally the Anti-torque pedals.

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Droop Compensator

A mechanical linkage that automatically adjusts the governor to compensate for changes in power, preventing lag in the system.

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Correlator

A mechanical connection between the collective and the throttle that links their movements.

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Vibration Absorption Devices

Devices used to mitigate vibration in helicopters, such as the Bifilar Vibration Absorber with its two four-arm disks, and the Hub Vibration Absorber with its weighted drum.

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Study Notes

Rotor Blade Design

  • Two main designs: symmetrical and asymmetrical
  • Symmetrical blades have better aerodynamic pitch characteristics
  • Asymmetrical blades provide greater lift for the same surface area, with higher camber on one side
  • Engineers use sweeping edges on asymmetrical blades to achieve symmetrical pitching characteristics
  • Symmetrical blades are the most common design due to the asymmetrical design's instability
  • Two main planform types: parallel (uniform) and tapered
  • Uniform planform has parallel leading and trailing edges
  • Uniform planform creates greater lift due to its chord line
  • Tapered planform has converging leading and trailing edges with decreasing chord length towards the root
  • Manufacturers prefer uniform planforms for cost-effectiveness, using one machine stamping for ribs and only one rib part number.
  • Tapered planforms need different rib numbers due to varying chord length
  • Tapered blades provide more equal lift, accounting for speed variations
  • Parallel blades have negative twist for maintaining the same lift at different rotor blade speeds.

Helicopter Skin Configurations

  • Single pocket: Quicker to build, but harder to repair if damaged.
  • Multi pocket: Easier to repair, but more expensive to build.

Helicopter Construction

  • Bonded construction is stronger and eliminates drilling holes
  • Multi-pocket skin configuration is easier to repair than single-pocket

Rotor Blade Weights and Balance

  • Weight added to the leading edge lowers the helicopter in its plane of rotation.
  • Weight added to the trailing edge raises the helicopter in its plane of rotation.

Trim Tabs

  • Trim tabs adjust the rotor blades to fly higher or lower in their plane of rotation.
  • Trim tab position is adjusted to alter the aerodynamic effect of airflow, for achieving correct pitch changes.

Rotor Blade Material and Color

  • Metal, composite, and wood are common materials for rotor blades.
  • Rotor blade bottoms are painted flat black to reduce glare for the pilot.

Rigging Procedures

  • Rigging occurs before further procedures and ensures removal of all residual hydraulic force.
  • Collective is rigged first on a helicopter for all stages of preparation.

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Description

This quiz covers the essential aspects of rotor blade design, focusing on symmetrical and asymmetrical configurations. It also explores planform types, highlighting the advantages and disadvantages of uniform and tapered designs. Understand the aerodynamic implications and manufacturing preferences in rotor blade engineering.

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