Rotor Blade Maintenance and Design

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Questions and Answers

What is the main advantage of metal blades?

Metal blades are more efficient in terms of weight and performance. (correct)

Metal blades are cheaper to produce than wooden blades.

Metal blades are easier to repair and maintain than wooden blades.

Metal blades are generally stronger and more durable than wooden blades.

What is the purpose of the stainless steel cap on the leading edge of a wooden rotor blade?

To increase the overall weight of the blade.

To improve aerodynamic performance.

To protect the leading edge from damage during flight. (correct)

To reduce noise during flight.

What is a significant disadvantage of wooden rotor blades?

Wooden blades are more susceptible to damage from moisture than metal blades. (correct)

Wooden blades are less efficient in terms of aerodynamic performance than metal blades.

Wooden blades are more difficult to manufacture than metal blades.

Wooden blades are heavier than metal blades.

What is the purpose of the aluminum pockets on the trailing edge of a metal rotor blade?

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

How are metal rotor blades typically attached to the rotor head?

They are bolted to the rotor head using a steel cuff. (B) Signup and view all the answers

What is the purpose of the stainless steel abrasion strip on a metal rotor blade?

To protect the leading edge from damage during flight. (A) Signup and view all the answers

What should be done with a rotor blade that has sustained nonrepairable damage?

Condemn and dispose of the blade locally. (A) Signup and view all the answers

Why must wooden rotor blades be paired?

To ensure consistent weight and balance between the blades. (D) Signup and view all the answers

Which of the following should be protected with a light coating of corrosion preventive?

The blade's main bolt hole bushing. (B), The blade's outboard eroded surfaces. (C) Signup and view all the answers

Which of the following is NOT a common feature of both wooden and metal rotor blades?

A steel cuff attached to the root end of the spar. (B) Signup and view all the answers

Where should the manufacturer's blade records be placed?

Inside the container record tube. (D) Signup and view all the answers

What should be done to the container before storing the blade?

Remove old markings and stencil the blade's NSN, model, and serial number. (B) Signup and view all the answers

How should the blade be secured when packaging?

In a cushioned container with a secured lid. (B) Signup and view all the answers

What is the primary function of tail rotor blades?

Provide directional control (B) Signup and view all the answers

What materials are used to construct tail rotor blades?

Metal and fiberglass (B) Signup and view all the answers

Which type of material is commonly used for spars in metal tail rotor blades?

Aluminum (B) Signup and view all the answers

What is used to support the blade skins on the inside of metal tail rotor blades?

Aluminum honeycomb (D) Signup and view all the answers

How are the blade skins of fiberglass tail rotor blades supported?

Foam plastic and aluminum honeycomb (B) Signup and view all the answers

What method is sometimes used to achieve spanwise balance on tail rotor blades?

All of the above (D) Signup and view all the answers

How is chordwise balance achieved on some tail rotor blades?

Adding weights to the blade tip behind the spanwise balance screw (D) Signup and view all the answers

What does the process of trammeling involve?

Aligning the tail rotor blades with a 2° angle of lead (D) Signup and view all the answers

When moving the span-wise weight is permitted, what is the repairer's task?

Calculate the weight change needed after weighing the blade. (D) Signup and view all the answers

What is the primary goal of tracking a helicopter blade?

Ensuring all blades rotate on the same plane. (D) Signup and view all the answers

What can happen if helicopter blades do not track correctly?

Damage to helicopter parts. (D) Signup and view all the answers

Adding or removing tracking weights affects the blade track by:

Moving the blade up or down. (D) Signup and view all the answers

What is the primary function of trim tabs on helicopter blades?

To fine-tune the blade's tracking. (D) Signup and view all the answers

Why are trim tabs typically located near the blade tip?

To maximize the aerodynamic effect. (D) Signup and view all the answers

How are trim tabs adjusted to achieve proper blade tracking?

By altering the trim tab's angle of attack. (A) Signup and view all the answers

What is the primary benefit of using trim tabs instead of tracking weights?

Reduced maintenance costs. (A) Signup and view all the answers

What is the primary purpose of the spar in a rotor blade?

To add strength to the rotor blade (C) Signup and view all the answers

How is the chord of a rotor blade defined?

The width measured at the widest point (D) Signup and view all the answers

What characterizes chordwise damage to a rotor blade?

It completely interrupts lines of stress (A) Signup and view all the answers

Which statement is true about doublers in rotor blades?

They provide extra strength at the root end (B) Signup and view all the answers

What is the top side of a rotor blade typically referred to as?

The low-pressure side (C) Signup and view all the answers

What material is generally used to construct the spar of a rotor blade?

Aluminum or steel (B) Signup and view all the answers

What does the chord line of a rotor blade represent?

An imaginary line perpendicular to the span line (D) Signup and view all the answers

In rotor blade terminology, what is the bottom side referred to as?

High-pressure side (C) Signup and view all the answers

What is the primary reason for bonding in blade construction?

To reduce the use of hardware that weakens the bond (D) Signup and view all the answers

What must manufacturers avoid when drilling in load-carrying parts of the blade?

Drilling any holes except at the ends (B) Signup and view all the answers

What effect do paint thinners and cleaning solvents have on bonded joints?

They can dissolve bonded joints if used carelessly (C) Signup and view all the answers

Where is the faying surface located?

Where two objects bond together (B) Signup and view all the answers

Which type of weight is placed into the leading edge of a blade during manufacture?

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

What must a repairer remember if moving weight in helicopter blades?

It will move the center of gravity forward or backward (D) Signup and view all the answers

Where are spanwise balance weights typically located on a blade?

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

What happens when spanwise weight is added to the blade?

The center of gravity moves outward (B) Signup and view all the answers

Study Notes

Rotary Wing Aerodynamics

Rotor blades are designed as symmetrical airfoils to create a stable aerodynamic pitching characteristic.
Aerodynamic stability is achieved when the center of gravity, center of pressure, and blade-feathering axis are aligned at the same point.
This alignment ensures the blade remains stable during pitch changes.

Rotor Blades - Design and Construction

Rotor blade design and construction vary among manufacturers, though all aim to create the most efficient and economical lifting device.
Helicopter design requirements influence rotor blade design and construction.

Rotor Blades - Materials

Common materials for rotor blades include aluminum, steel, brass, and fiberglass.
Early rotor blades were often made of wood.
Metal blades followed, then composite blades using various materials as the newest blade design.

Wooden Rotor Blades

First production rotor blades were laminated wood (birch, spruce, pine, and balsa).
A steel core was placed near the leading edge of the blade for increased strength.
The exterior surface was covered with resin-impregnated fiberglass cloth.
Two-thirds of the blade's outboard leading edge portion is often protected with stainless steel.
Blades are typically manufactured in matched pairs.

Metal Rotor Blades (Aluminum)

Metal blades have been in production for over 40 years.
Construction varies widely due to manufacturing expense and different manufacturers.
A typical metal blade has a hollow, extruded aluminum spar that forms the leading edge.
Quality control is a key advantage of this construction.

Metal Blades - Design Features

Single blades can be exchanged without needing matched sets.
Aluminum pockets on the trailing edge of the spar improve the blade's streamlining.
An aluminum tip cap, secured via screws, improves streamlining and aids in bonding.
Like other metals, blade life is limited due to stress during flight.

Composite Rotor Blades

Fiberglass or composite blades are load-bearing components, either using fiberglass or metal spars.
Roving's, which are strips of glass, make up the spar and are impregnated with epoxy resin.
The roving materials are wrapped around a foam core, and fiberglass cloth creates the blade's skin.
Root reinforcement plates are frequently added to the blade.
The leading edge is often covered with a stainless steel strip.

Rotor Blades - Internal Structural Components

Rotor blades typically have ribs, I-beams, and spanwise channels to support the blade skin.
Aluminum honeycomb foil is another common supporting structural element.

Blade Nomenclature

The Blade Planform is the overall shape viewed from above, either uniform or tapered.
Uniform planforms are more common as they are simpler to manufacture.

Blade Construction- Single Pocket/Fairing

Single-pocket blades have a one-piece skin on both top and bottom that extends across the entire span and chord, positioned behind the spar.
This design is relatively simple and easier to construct because it has a minimum number of pockets.

Blade Construction-Multiple Pockets/Fairings

Multiple-pocket blades are more costly, but pockets are simpler to replace if damaged, making repeated use possible.
This construction approach is more flexible overall
Blade pockets or fairings, coated with fiberglass, provide support

Blade Construction - Bonds and Bonding

Bonding joins multiple parts using adhesive compounds.
Using bonding is less expensive than other construction types, such as using rivets or screws.
Manufacturers avoid drilling holes, except at blade ends, to aid in overall structural strength.

Rotor Blade Preservation and Storage

Condemn and dispose of damaged blades.
Repair or seal any holes to prevent moisture and corrosion.
Remove all foreign matter with soap and water.
Protect any bare or exposed metal with corrosion-resistant coating.
Secure blades within shock-mounted supports when packaging and storing them.
Record required information on the container, such as the blade's NSN, model, and serial number.

Blade Balance

Balancing methods include chordwise, spanwise, or tracking weights.
These are often added to the leading edge to ensure proper balance.

Blade Construction - Trim Tabs

These tab adjustments allow controllers to position the rotor blades on a similar plane for flight.

Blade Construction- Tail Rotor Blades

Tail rotor blades primarily provide directional control—not lift.
Metal or fiberglass, and they are generally made using a similar method to main rotor blades, extrusions, and sheet channels.

Blade Construction -Fiberglass Blades, Metal Blades

The blade skin for metal blades is formed around the spar and is bonded to the inside.
Larger blades often have internal supporting structures (aluminum honeycomb and ribs) for reinforced support.
Smaller blades may not have internal reinforcement.
Fiberglass blade skins are formed around and bonded to H-shaped titanium spars, further reinforced by aluminum honeycomb.

Blade Construction - Blade Construction (Figures 3-10, 3-16)

The mast is station zero, which is referred to in diagrams for balance points during manufacturing.

Blade Balance-Spanwise, Trammeling

Adding or subtracting washers on the blade tip allows for spanwise balance.
Other models add the corresponding weights in the cuff attachment bolts.
Also, weights can be added or removed at the spanwise balance bolts
Fully articulated tail rotor systems must be trammeled before balancing.
Trammeling involves aligning the tail rotor blades equally, leading to a 2º lead angle.

Blade Construction (Figures 3-18, 3-20, 3-21, 3-22)

The repairer must understand that changing weights changes the center of gravity.
Adding/subtracting weight has the effect of moving the center of gravity.
Spanwise weights are at the blade tip for attaching to the spar.
Weights applied at different locations impact the rotor's stability.

Blade Construction - Blade Construction (Figures 3-23, 3-24)

Attaching weights in front of and behind a blade's feathering axis will help the blade track evenly.
Tracking weights can be shifted to adjust the orientation of the blade in the plane of rotation.
Trim tabs allow for the blade to be moved relative to its initial position, and to alter the leading edge's flying position up or down relative to the baseline.

Rotor Blade Construction - General

All blades require a specific build and tracking orientation in the plane of rotation.
Failure to meet this specification leads to various issues and problems, both structurally and practically affecting flight.

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Description

This quiz focuses on the maintenance and design features of rotor blades used in aviation. It covers topics such as the advantages and disadvantages of metal and wooden blades, their construction materials, and best practices for storage and protection. Test your knowledge on rotor blade functionality and care with these targeted questions.