Rotor Blade Construction Quiz

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Questions and Answers

What protects the leading edge of wooden rotor blades from abrasion?

Aluminum tip cap

Aluminum pockets

Stainless steel cap (correct)

Fiberglass cloth

What is a distinct advantage of metal rotor blades?

They are lighter than wood blades

They are more resistant to moisture damage

They have better quality control during construction (correct)

They are less expensive to manufacture

What is the purpose of the aluminum pockets on metal rotor blades?

To attach the blade to the rotor head

To protect the blade from abrasion

To improve the blade's aerodynamic profile (correct)

To provide additional strength to the blade

What is a disadvantage of wooden rotor blades?

They are susceptible to moisture damage (C) Signup and view all the answers

What type of construction is common to all rotor blades?

Bonded construction (C) Signup and view all the answers

What is the purpose of the steel cuff on metal rotor blades?

To attach the blade to the rotor head (D) Signup and view all the answers

What is the main reason why most wooden rotor blades are in matched pairs?

To ensure that the blades are identical in shape and weight (D) Signup and view all the answers

What type of material is used to cover the exterior surface of a fiberglass rotor blade?

Resin impregnated fiberglass cloth (A) Signup and view all the answers

What is the location of the blade tip?

Furthest from the center of rotation (A) Signup and view all the answers

What is the purpose of the blade tip cap?

To provide a means for attaching balance weights (A) Signup and view all the answers

What is the leading edge of the blade?

The part of the blade that meets the air first (D) Signup and view all the answers

Why is the leading edge of the blade thicker than the trailing edge?

To improve the aerodynamic performance of the blade (D) Signup and view all the answers

Why is the leading edge of the blade covered with a hard cap or coating?

To protect the blade from erosion caused by sand and dust (A) Signup and view all the answers

What is the span of a rotor blade?

The distance from the root to the tip of the blade (C) Signup and view all the answers

Why is the span line important to blade repairers?

It helps them to locate and classify damage to the blade (A) Signup and view all the answers

What is a primary advantage of using a uniform planform for rotor blades?

It simplifies the manufacturing process. (C) Signup and view all the answers

What does a uniform blade design reduce in terms of production?

The number of unique stamping dies needed. (C) Signup and view all the answers

How does a tapered planform blade differ in performance compared to a uniform planform?

It achieves a more uniform lift distribution. (C) Signup and view all the answers

What is a characteristic of most rotor blades in terms of twist?

They are twisted negatively from root to tip. (B) Signup and view all the answers

Which material is commonly used for the skin of rotor blades?

Aluminum (B) Signup and view all the answers

What is the function of the blade root in a rotor blade?

It provides attachment to the rotor head. (C) Signup and view all the answers

Why are tapered planform blades not commonly used by manufacturers?

They are more complicated and costly to manufacture. (D) Signup and view all the answers

What consequence arises if the blade angle remains constant along its length?

Uneven lift distribution across the blade. (B) Signup and view all the answers

What is the faying surface in bonding?

The surface area where two objects are bonded together (B) Signup and view all the answers

Why do manufacturers avoid drilling holes in load-carrying parts of the blade?

Holes weaken the strength of the bond (A) Signup and view all the answers

What type of weights are placed into the leading edge of a blade for mass balance?

Mass balance weights (B) Signup and view all the answers

What happens when weights in the blade are adjusted?

It alters the center of gravity (B) Signup and view all the answers

What is a potential consequence of careless use of cleaning solvents on bonded joints?

Dissolves bonded joints (B) Signup and view all the answers

Which weight type is typically located at the tip of the blade?

Spanwise weights (D) Signup and view all the answers

What does adding spanwise weight to a blade do to the center of gravity?

Moves it outward (C) Signup and view all the answers

When is a repairer allowed to move weights in helicopter blades?

Only with specific manufacturer guidance (D) Signup and view all the answers

What effect does subtracting weight have on the center of gravity?

Moves it inward (C) Signup and view all the answers

What negative consequences can arise from blades failing to track correctly?

Causes vibrations and damages parts (D) Signup and view all the answers

How can tracking weights be used to retain blade track?

By adding or shifting weights in front of and behind the feathering axis (A) Signup and view all the answers

What is a cheaper method to align rotor blades to the same plane of rotation?

Using trim tabs on the trailing edge (D) Signup and view all the answers

What is the function of a trim tab during tracking operations?

It adjusts the blade's flight altitude in the plane of rotation (A) Signup and view all the answers

Where is the trim tab typically located on a rotor blade?

Near the tip of the blade (B) Signup and view all the answers

What is one reason for adding tracking weights to helicopter blades?

To maintain a consistent tip path plane (C) Signup and view all the answers

What must happen for all rotor blades to fly in the same plane of rotation?

The trim tabs need to be adjusted correctly (C) Signup and view all the answers

What is the purpose of painting the bottom of the rotor blade black?

To prevent glare from reflecting into crew compartments (C) Signup and view all the answers

What is the purpose of blade stations?

To indicate the position of the blades relative to the mast (A) Signup and view all the answers

What is the main advantage of a single-pocket or fairing blade?

It is easier to manufacture than a multiple-pocket blade (A) Signup and view all the answers

What is the main advantage of a multiple-pocket or fairing blade?

It is easier to repair in the event of damage (C) Signup and view all the answers

What is the purpose of the internal structural components in a rotor blade?

To provide structural support for the blade skin (B) Signup and view all the answers

What is bonding in the context of rotor blade construction?

A method of joining two or more parts together using an adhesive (C) Signup and view all the answers

Which type of rotor blade is typically used on large helicopters?

Multiple-pocket or fairing blade (B) Signup and view all the answers

Study Notes

Rotary Wing Aerodynamics

AVIA-1035 course
Focuses on rotor blade aerodynamics

Rotor Blades

Design and construction vary between manufacturers, but all aim for efficiency and cost-effectiveness.
Helicopter design dictates specific requirements for rotor blades, influencing their design.

Rotor Blade Design

Most blades are symmetrical airfoils to create a stable aerodynamic pitch.
Stability is ensured when the center of gravity, center of pressure, and feathering axis are aligned.
The constant alignment of these forces across blade pitch changes yields flight stability.

Asymmetrical Airfoils

Asymmetrical airfoils are becoming more common
This design is capable of producing greater lift compared to symmetrical airfoils.
Aerodynamic stability achieved with a 3° upward angle on the trailing edge.
This design counteracts excessive center of pressure shifts

Rotor Blade Materials

Common materials include aluminum, steel, brass, and fiberglass.
Initial blades often used wood, still used in some applications.
Metal blades were used next, followed by composite designs incorporating multiple materials.
Composite blades are the most recent design.

Wooden Rotor Blades

First production blades employed laminated wood from various species (birch, spruce, pine, balsa).
A steel core was placed within the wood laminations near the leading edge for reinforcement.
A resin-impregnated fiberglass cloth covers the exterior surfaces.

Wooden Blade Details

Two-thirds of the outboard leading edge covered with stainless steel caps for abrasion prevention.
Blade pairs are often a matching set for construction consistency; a single blade is not easily substituted.
Moisture affects wood blades; this can be mitigated by a brief helicopter run-up.

Metal Rotor Blades (Aluminum)

Have been used for over 40 years.
Construction varies considerably among manufacturers and over time.
Typical blades use an extruded hollow aluminum spar forming the leading edge.
Quality control during construction is an advantage.

Metal Blades - Design Details

Single blades can be replaced without a matched set.
Aluminum pockets bonded to the trailing edge help with streamlining.
An aluminum tip cap is fastened using screws, enhancing assembly efficiency.
Metal blades have a limited lifespan due to flight stresses.

Rotor Blades - Diagrams

Diagrams (Figures 3-6, 3-7, 3-8, 3-9, 3-10, 3-11, 3-12, 3-13, 3-14, 3-15, 3-16, 3-17. 3-18, 3-19, 3-20, 3-21, 3-22, 3-23, and 3-24) depict blade components and construction features.

Fiberglass/Composite Rotor Blades

Fiberglass is a primary material for construction.
The spar can be made of fiberglass or metal.
Roving material impregnated with epoxy resin is wound around a foam core.
Fiberglass cloth makes up the blade skins, providing rigidity and protection.

Rotor/Blade Reinforcement/Additions

Root reinforcement plates are added to fiberglass blades.
Trail edge foam filler and additional roving strips to the trailing edge reinforce stability.
Fiber coverings that add fairing and streamline the blade.
The leading edge of the fiberglass blade is protected by a stainless steel strip.
Balancing weights are added to the blade tip during manufacturing.

Rotor Blade - Aluminum Hollow Spar Design

Featured in Figure 3-7, highlighting structural details.

Rotor Blade - Composite Roving Design

Depicted in Figure 3-7, showing the blade root details.

Rotor Blade - Other Details

Additional protection with rubber erosion strips bonded to the underside of the blade.
Steel socket for attaching the blade to the rotor head.
Stainless steel tip caps fastened to the spar and tip pocket.
Internal grounding strips for static electricity transfer to the aircraft.

Blade Nomenclature

The planform is the blade shape viewed from above.
Uniform planforms are common for easier construction.
Tapered planforms give better lift throughout the blade.

Rotor Blade - Span and Span Line

Span is the distance from root to tip, a crucial measurement.
Span line is an imaginary line that runs parallel to the blade from the root to the tip.
Damages are often reported relative to the location on the span line.

Rotor Blade Defects

Defects parallel to the span line are less critical; the chordwise stress affects the entire blade.

Chord and Chord Line

Blade width measured at the widest point, the chord.
Chord line an imaginary line from leading to trailing edge, perpendicular to the span line.
Used as a reference line for angular measurement.

Spar Construction

Spar, the primary support structure, is often made of aluminum, steel or fiberglass.
Usually D-shaped, forming the airfoil leading edge.
Shape varies based on material and blade design fit.

Blade Construction - Other Components

Internal structural components include ribs, I-beams, spanwise channels, and aluminum honeycomb foil for strength.

Bonding

Bonding methods reduce hardware needs, which usually weaken the structural bond.
Bonding surfaces called faying surfaces.
This process is not susceptible to chemical damage or many cleaning solvents.

Blade Construction - Single Pocket

Uses a single, continuous skin for top and bottom construction
Skin wraps across the entire span and chord from behind the spar.
Simple design minimizes the number of joining points (pockets) or fairings during bonding.

Blade Construction - Multiple Pocket

Most large-rotor blades use multiple pockets or fairings behind the spar
Repairs only require replacing pockets or fairings instead of the entire blade, making repairs more efficient and cost-effective.

Blade Balance

Three types of balancing weights (mass chordwise, spanwise, and tracking) are used to ensure proper balance and distribution.
Mass balance bars are bonded to the leading edge of the blade.
Balance ensures that the center of gravity is about 25% of the chord.
Manufacturer-specific methods, shapes, and locations for balance vary.

Blade Movement Restriction

Usually, helicopter blade weights are fixed and not easily repositioned or adjusted.
Changing weights affect the center of gravity.
Spanwise weights affect the center of gravity to move outward or inward.

Blade Construction & Efficiency

Rotating blades should track on the same level plane for efficiency and vibration-free operation.
Tracking deviations cause vibrations leading to damage and reduced comfort.
Air turbulence caused by blade rotation also reduces performance.

Blade Construction - Trim Tabs

Trim tabs are used to fine-tune the blade's position in the plane of rotation.
Placement is typically at the blade tip for the necessary aerodynamic reaction.

Tail Rotor Blades

Tail rotor blades are used for directional control in helicopters.
Metal blades are built similarly to the main rotor blades with aluminum extrusions, hollow extrusions, and sheet channels.
Fiberglass tail rotor blades use fiberglass sheets and solid titanium spars.

Blade Preservation and Storage

Maintenance instructions for rotor blade handling, storage, inspections, and documentation.
Condemn blades with nonrepairable damage.
Tape blade holes and inspect for damage.
Clean the blade external surfaces.
Protect surface areas from erosion or corrosion.
Secure blades and containers after cleaning and repairs.
Document critical information such as NSN, model, and serial number.

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Description

Test your knowledge about rotor blade construction and materials with this detailed quiz. Explore the advantages and disadvantages of different rotor blade types, including wooden and metal blades, and their specific components. Perfect for aviation enthusiasts and students studying aerodynamics.