Rotor Blade Design and Helicopter Skins
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Questions and Answers

What material is used to protect the leading edge of rotor blades from erosion?

  • Aluminum
  • Stainless Steel (correct)
  • Titanium
  • Carbon Fiber

Why are the bottom of rotor blades painted flat black?

  • To improve visibility
  • To reduce drag
  • To absorb heat
  • To prevent glare in the pilot's vision (correct)

Which type of rotor blade is required to have static discharge abilities?

  • Metal blades
  • Wood blades
  • Composite blades (correct)
  • All of the above

What is the primary inspection method used for composite rotor blades?

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

Where are spanwise balance weights located on a rotor blade?

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

What effect does adding weight to the trailing edge of a rotor blade have?

<p>The helicopter will fly higher in its plane of rotation (C)</p> Signup and view all the answers

What is the purpose of trim tabs on a rotor blade?

<p>To adjust the blade's angle of attack (D)</p> Signup and view all the answers

What should be done before rigging a helicopter?

<p>Ensure all residual hydraulic pressure has been removed from the system (A)</p> Signup and view all the answers

Which blade design has higher camber on one side than the other?

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

What planform produces more equal lift due to accounting for speed variation?

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

Why are symmetrical blades considered the most common design?

<p>They have desirable pitching characteristics. (D)</p> Signup and view all the answers

What happens to parallel blades as a result of having a negative twist?

<p>They produce the same lift from root to tip. (C)</p> Signup and view all the answers

What is a reason for using bonded construction in blade manufacturing?

<p>It provides strength without drilling holes. (D)</p> Signup and view all the answers

Which skin configuration is quicker to build?

<p>Single pocket (C)</p> Signup and view all the answers

What would happen if the single pocket skin configuration is damaged?

<p>It would need to be replaced completely. (B)</p> Signup and view all the answers

What is a characteristic of tapered blades in terms of rib configuration?

<p>Ribs have to change due to uneven chord length. (A)</p> Signup and view all the answers

What must be ensured before connecting the collective and throttle together?

<p>The throttle is rigged correctly (C)</p> Signup and view all the answers

What is the first step in the testing process for the helicopter after rigging is complete?

<p>Ground run test (A)</p> Signup and view all the answers

What advantage does the main servo flap provide?

<p>Eliminates the need for hydraulics (C)</p> Signup and view all the answers

In what order should the flight controls be rigged?

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

Which device is more complex, the droop compensator or the correlator?

<p>Droop compensator (C)</p> Signup and view all the answers

Which vibration absorbing device consists of weighted drum supported by three springs?

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

What role does the elevator play in a helicopter?

<p>Provides a more level flight attitude (A)</p> Signup and view all the answers

If a helicopter has a fixed elevator, what type of airfoil will it have?

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

Flashcards

Symmetrical Blade Design

A blade design where both sides of the blade have the same shape.

Asymmetrical Blade Design

A blade design where one side of the blade has a higher camber than the other.

Uniform Planform

A planform where the leading and trailing edges of the blade run parallel to each other.

Tapered Planform

A planform where the leading and trailing edges of the blade converge towards the blade root.

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Bonded Construction

A method used to strengthen rotor blades by bonding the skin and other structural parts together without drilling holes.

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Single Pocket Skin Configuration

A skin configuration where a single piece of skin covers the entire blade section.

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Multi-Pocket Skin Configuration

A skin configuration where the blade section is covered with multiple smaller pieces of skin.

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Trim Balance Weights

Small weights placed on the trim tab of a rotor blade to adjust its balance and control its pitch.

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Effect of weight on rotor blade movement

Adding weight aft of the trim tabs will cause the blade to travel higher in its plane of rotation. Adding weight forward of the trim tabs will cause the blade to travel lower in its plane of rotation.

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Why are rotor blade leading edges capped with stainless steel?

The leading edges of all rotor blades have stainless steel capping to protect against erosion caused by dust particles in the air during flight.

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Why are rotor blades painted flat black on the bottom?

The bottom of rotor blades are painted flat black to prevent glare reflecting into the pilot's vision.

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What type of rotor blades require static discharge abilities?

Composite blades need to have static discharge abilities to prevent the buildup of static electricity that could cause issues during flight.

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What is the primary inspection method for composite rotor blades?

The primary inspection method used for composite rotor blades is tap testing. This method helps detect internal damage that might not be visible on the surface.

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Which type of blade skin configuration is more expensive?

Multi-pocket blade skin configurations are more expensive to build than simpler designs.

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What is the purpose of double plates at the root of the tip?

Additional double plates at the root of the tip (near the center of the span) increase structural strength and stiffness without increasing blade weight.

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Location of spanwise balance weights

Spanwise balance weights are located at the blade tip, in the center along the span line. They help balance the weight distribution across the blade, preventing vibrations during flight.

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Servo Flap

A small airfoil located on the trailing edge of each rotor blade, positioned at 75% of the blade's span, designed to maximize aerodynamic response to adjustments.

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Main Servo Flap Function

Removes the need for hydraulic systems in pitch control, offering infinite life and reducing vibrations.

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Benefits of Servo Flaps

Simplifies the hub design, eliminates hydraulic systems, reduces vibrations, improves flight smoothness, and allows quicker response for autorotation.

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Droop Compensator

A mechanical linkage that automatically adjusts the governor, keeping the engine's power output in sync with your control inputs.

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Correlator

A direct mechanical connection between the collective pitch lever and the throttle, linking the two controls together.

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Vibration Absorbing Devices

Devices designed to reduce vibrations in the helicopter, using different mechanisms.

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Bifilar Vibration Absorber

A vibration absorbing device that uses two four-armed disks to dampen vibrations.

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Hub Vibration Absorber

A vibration absorbing device that uses a weighted drum supported by springs to reduce vibrations.

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Study Notes

Rotor Blade Design

  • Two main designs: symmetrical and asymmetrical
  • Symmetrical blades have better aerodynamic pitch characteristics
  • Asymmetrical blades generate greater lift over the same surface area, with higher camber on one side.
  • Asymmetrical blades are modified to have the same pitching characteristics as symmetrical blades (e.g. sweeping edges).
  • Symmetrical blades are the most common design because of asymmetrical blade instability.
  • Two types of blade planforms are uniform (parallel leading and trailing edges) and tapered (converging leading and trailing edges).
  • Uniform blades generate greater lift due to chordline.
  • Tapered blades have changing rib numbers due to varying chord lengths.
  • Tapered blades produce more even lift across the blade due to speed variations.

Helicopter Skin Configurations

  • Single pocket skin is quicker to build due to fewer pieces, but more difficult to repair.
  • Multi pocket skin is easier to repair as individual damaged sections can be replaced.
  • Multi-pocket skins are more expensive to build.

Bonded Construction

  • Bonded construction is used because it's stronger and doesn't require drilling holes.

Rotor Blade Trim Tabs

  • Trim tabs can be used to adjust the altitude of the blade.
  • Moving weight forward on the trim tab lowers it in rotation.
  • Moving weight backward on the trim tab raises it in rotation.

Rotor Blade Vibration

  • Bifilar vibration absorbers use weights on the arms of a device
  • Hub vibration absorbers use a weighted drum supported by springs.

Flight Controls

  • Collective is rigged first.
  • Throttle and collective are connected through a device called a correlator
  • Drivetrain elements and hydraulic components of a helicopter are rigged individually before correlator connection.

Servo Flap

  • Servo flaps located on the trailing edge of each blade.
  • Improves autorotation and reduces forces needed for pitch or altitude change.

Other important factors

  • Cyclic movement is adjusted to maintain a level attitude.
  • Overspeed is dangerous, as it can cause unwanted centrifugal force in the helicopter.
  • Mass balance weights are placed on the leading and trailing edge of the blades.
  • Mass balance weights in chord-wise direction balance the weight across the rotor.
  • The leading edge of each rotor blade contains a tracking weight.
  • Span-wise weights are situated on the central section of rotor blades.

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Description

Explore the intricacies of rotor blade design, focusing on symmetrical and asymmetrical configurations, as well as their aerodynamic characteristics. The quiz also delves into the differences between single pocket and multi pocket skin configurations for helicopters, detailing their advantages and disadvantages.

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