Rotor Blade Maintenance Quiz

Rotary Wing Aerodynamics

• AVIA-1035 course
• Presented by FANSHAWE

Rotor Blades

• Designs and construction vary by manufacturer, but all aim for efficient, economical lifting.
• Helicopter design requirements influence blade design & construction.

Rotor Blade Design

• Symmetrical airfoils are standard to create stable aerodynamic pitching.
• Stability achieved when center of gravity, center of pressure, and feathering axis align.
• Blade stays stable in flight because the forces remain aligned as pitch changes.
• Asymmetrical airfoils are gaining popularity, offering greater lift than symmetrical models of equivalent size.
• Stability achieved by building a 3° upward angle into the trailing edge.
• This prevents excessive center-of-pressure movement during angle of attack changes.

Rotor Blade Materials

• Common materials include aluminum, steel, brass, and fiberglass.
• Early blades were made of wood, some still in use.
• Metal blades followed, then composite blades utilizing various materials, representing the newest blade type.

Wooden Rotor Blades

• First production blades were laminated wood (birch, spruce, pine, and balsa).
• Combinations used to achieve needed strength and aerodynamics.
• Steel core near leading edge.
• Outer surface covered with resin-impregnated fiberglass cloth.
• Two-thirds of outer leading edge covered with stainless steel cap for abrasion protection.
• Often used in matched pairs due to wood variations.
• Susceptible to moisture.

Metal (Aluminum) Rotor Blades

• Over 40 years in use; construction varies significantly between manufacturers.
• A typical metal blade includes a hollow, extruded aluminum spar creating the leading edge.
• Single blades can be changed without needing a matched pair.
• Aluminum pockets bonded to the trailing edge for streamlining.
• Aluminum tip cap fastened to spar and tip pockets.
• Like other metal dynamic components, likely to be limited in lifespan due to stresses.

Composite Rotor Blades

• Fiberglass or composite blades are the main load-carrying components, often made of fiberglass.
• Fiberglass blade use a procured roving spar, or metal spar.
• Roving (glass material strips) are impregnated with epoxy resin and wound around a foam core.
• Skins are made of fiberglass cloth.
• Root reinforcement plates added.
• Trailing edge includes another roving strip, and fiberglass covered, bonded area.
• The leading edge is protected by a stainless steel covering.
• Balancing weights added by manufacturers.

Rotor Blades - Figure 3-6

• Displays the parts of a typical metal blade with labels for each component.

Rotor Blades - Figure 3-7

• Displays a cross-section and diagram of a composite blade.

Rotor Blades - Figure 3-7 Composite Rovings

• Shows a detailed diagram of the root section of the composite blade.

Rotor Blade Additional Information

• Additional protection added with a rubber erosion strip to bottom.
• A steel socket is threaded into the blade's spar shank for connection to the rotor head.
• Stainless steel tip caps are bolted to spar and tip pockets.
• Internal grounding strips bond electricity to aircraft.

Blade Nomenclature

• The planform is the shape when viewed from above; it can be uniform or tapered.
• Uniform planforms are easier to manufacture because all internal parts are the same size.

Rotor Blades - Figure 3-8

• Illustrates the differences between uniform and tapered planforms.

Rotor Blades - Figure 3-10

• Shows the tip of the rotor blade with markings.
• Attachments for added weight.

Rotor Blades - Figure 3-11

• Shows the leading edge and its significant thickness and protective covering from abrasion.

Rotor Blades - Figure 3-12

• Shows the trailing edge of the rotor blade and its reinforcement.

Rotor Blades - Figure 3-13

• Illustrates the span and span line of the rotor blade.

Rotor Blades - Figure 3-14

• Shows the chord line of the rotor blade.

Rotor Blades - Figure 3-15

• Show different examples of spar designs and their relation to rotor blades, with various material types' spar examples.

Rotor Blades - Doublers

• Rotor blades can use flat plates (doublers) bonded to the root to strengthen them.
• Not all blades use doublers, though, as the spars themselves may already be strong enough.

Rotor Blades - Top

• Low-pressure side viewed from above the helicopter.
• Typically painted olive drab, gray, or black.

Rotor Blades - Bottom

• High-pressure side viewed from below the helicopter.
• Typically painted a matte-black finish.

Rotor Blades - Blade Stations

• Mast is station zero, numbers increase outward to blade tip.

Rotor Blades - Blade Construction - Single Pocket or Fairings

• One-piece skin covers both top and bottom (the 'fairings').
• Fabric extends past the spar.
• Easier and less complex constructions method.

Rotor Blades - Blade Construction - Multiple Pockets or Fairings

• Multiple pockets or compartments within the blades.
• Only the pocket (or fairing) needs to be replaced if damaged, allowing blades use for extended periods.
• More flexible with reduced vibration.

Rotor Blades - Internal Structural Components

• Ribs, I-beams, spanwise channels, and aluminum honeycomb are internal support structures.

Rotor Blades - Bonds and Bonding

• Bonding is a method where parts are joined using adhesives.
• Bonding decreases the need for hardware like bolts, rivets, and screws.

Rotor Blade Construction - However, Bonds React

• Bonds react to the chemical action of solvents such as paint thinners.
• Careless use of such solvents can damage the bonded joints.

Rotor Blades - Figure 3-19

• Depicts the bonding process and the faying surface of the blades.

Rotor Blades - Blade Balance

• Three types of weights are applied: mass, chordwise, spanwise, and tracking.
• Mass balance weights are positioned into the leading edge.
• Ensure that the chordwise balance is about 25 percent of the chord.

Rotor Blades - Figure 3-20

• Shows mass, spanwise, and tracking balance weights on the blade

Rotor Blades - Figure 3-21

• Shows three different examples of balance bars.

Rotor Blades - Blade Construction - The Repairer is Not Allowed

• Repairers are generally prohibited from changing weights.
• Moving weights repositions the center of gravity and effects balance and control.
• Spanwise balance weights are normally attached at the tip.

Rotor Blades - Figure 3-22

• Shows the application of weights to the blade bracket track to adjust its balance.

Rotor Blades - Blade Construction- When Movement Is Necessary

• When necessary to adjust weights, the repairer must account for its effect on the center of gravity.
• Weights are added or subtracted to balance the blade in one direction or another

Rotor Blades - Blade Construction - To Be Efficient

• Blades should track on the same plane for smooth rotation, avoiding damage and comfort reduction.
• Air turbulence from blades can cause a loss of performance.

Rotor Blades - Blade Construction - One Way of Retaining

• Tracking weights are attached to the front or back of the feathering axis at the blade tips.

Rotor Blades - Figure 3-23

• Shows how weights change the track of a rotor blade when applied in specific areas.

Rotor Blades - Blade Construction - Trim Tabs

• Another method using trim tabs to adjust rotor blades on the same plane of rotation
• This often involves adding a metal strip to the trailing edge.
• Trim tabs are employed to adjust the path to ensure proper lift operation.

Rotor Blades - Figure 3-24

• Illustrates the use of trim tabs to adjust the blade's track, showing the up or down adjustment effects.

Rotor Blades - Blade Construction - In Tracking Operations

• To change the leading edge positioning of the blade, adjustment of the trimming tabs.

Rotor Blades - Tail Rotor Blades

• Used exclusively for directional control.
• Similar construction methods as primary rotor blades, but often made of aluminum.

Rotor Blades - Blade Construction - Fiberglass Tail Blades

• These blades are constructed using fiberglass sheets and titanium spars.

Rotor Blades - Figure 3-25

• Displays the main components of fiberglass tail rotor blade, including the spar, channels, and other support areas.

Rotor Blades - Blade Construction - Metal Blades

• Metal blade skins encase the spar, supported with honeycomb and ribs.
• Some smaller blades lack these internal supports.

Rotor Blades - Blade Construction - Fiberglass Blades

• Fiberglass blade skins are wrapped around and bonded to H-shaped titanium spars.
• Supported from the inside, with aluminum honeycomb used to fill the space around the spars.

Rotor Blade Construction - Blade Balance - Spanwise

• Achieves balance by adding or subtracting washers at the blade tips in some designs.
• Other models will instead add washers to the blade-cuff attaching bolts.
• In other designs, chordwise balance is achieved by altering weights at the blade's tips that are placed behind the spanwise balance screws.

Rotor Blade Construction - Blade Balance - Other Models

• Blades may be balanced by adding weights to the trailing edge near the cuff end.
• Fully articulated tail rotor systems must have a trammeling step prior to the balancing procedure.

Rotor Blade Preservation and Storage

• Condemn and dispose of blades with irreparable damage.
• Tape holes to protect from moisture and foreign object damage (FOD).
• Clean blades thoroughly with mild soap and water.

Rotor Blade Preservation and Storage - Blade Protection

• Protect eroded areas of blades with a coating of corrosion preventative or primer.
• Protect any exposed bare metal, including components like bushing and pads, with a coating for corrosion protection.
• Secure the blade in shock-mounted supports and lid during packaging.

Rotor Blade Preservation and Storage - Documents

• Store manufacturer's records in a waterproof bag inside container tubes.
• Eliminate previous markings.
• Stencil the blade's national stock number (NSN), model and serial number.

Rotor Blade Construction - Various aspects

• Modern rotor blades commonly made of metal.
• Rotor blades are balanced to achieve even rotation (e.g., by moving weights or using trim tabs).

Test your knowledge on rotor blade maintenance and repair techniques. This quiz covers essential topics such as moisture protection, coatings, alignment, and the effects of weight adjustments on rotor performance. Understand best practices in rotor blade handling and management.