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Major Structural Components

Major Structural Components

  1. Wings
  2. Fuselage
  3. Powerplant
  4. Empennage (Tail Section)
  5. Undercarriage (Landing Gear)


  1. Wing Position
  • Low Wing
  • Mid Wing
  • High Wing
  1. Wing Shape
  • Rectangular
  • Tapered
  • Swept (Slight, Moderate, Great, and Forward Sweep Wing)
  • Delta (Simple and Complex Delta Wing)
  1. Wing Number
  • Monoplane
  • Biplane / Multiple Wings
  • Triplane / Multiple Wings
  1. Others..
  • Canard
  • Winglet
  • Semi-Cantilever (braces)


  • Nose and Empennage


  • Longerons
  • Struts
  • Stingers
  • Bulkhead


  • Monocoque (Single Shell)
  • Semimonocoque


  1. Engine Position
  • On the wings
  • On the wing pylons
  • Close to the Fuselage
  • Rear Mounted
  1. Engine Number
  • Single Engine
  • Twin Engine
  • Triple Engine
  • Four (Multiple) Engine
  1. Kind of Engine
  • Piston (Propeller)
  • Turboprop (Propeller Turbine)
  • Jet Engine
  • Turbofan

Types of Powerplant

  • Tractor (front)
  • Pusher (back)
  • Variable Direction



  1. Conventional / Standard
  2. Twin Vertical Stabilizers
  3. Triple Vertical Stabilizers
  4. V-Butterfly Tail
  5. T- Tail


  1. Vertical (Fin) and Horizontal Stabilizers
  2. Dorsal (Top) and Ventral (Bottom) Fins
  3. Ruders (yaw and p-factor) and Elevators (pitch) 
  4. Right and Left Fin


  • Floaters / Hull
  • Wheel (Dual, Tricycle and Multiple)


  1. Nose Wheel (For Pusher Type)
  2. Main Landing Gear (fixed and retractable)
  3. Tail Wheel (For Tractor)


  1. Rough Field
  2. Soft Field


  1. Wing
  • Flaps
  • Ailerons
  1. Tail Unit
  • Rudders (yaw and p factor)
  • Elevators

Fairing – curving 

Property of Materials

  1. Hardness (resist abrasion) vs 
  2. Toughness (deformed w/o breaking)
  3. Elasticity (return orig shape) vs 
  4. Plasticity (recover shape after deform)
  5. Malleability (hammer into shape w/o breaking) vs 
  6. Ductility (bent w/o breaking)
  7. Strength (resist stress w/o deform) vs 
  8. Stiffness (resist elastic deform)
  9. Fusibility (heat – liquid)
  10. Conductivity (carry heat and electricity)
  11. Contraction and Expansion
  12. Density (weight of unit volume) m/v
  13. Brittleness (deform w/o shattering)

Non-Metallic Materials


Wood Structures

  • Solid Wood (pie)
  • Laminated Wood (2 – 3 pieces)
  • Ply Wood (3 or more layers)

2 Basic Species Used in Aircraft Construction

  1. Hardwood (deciduous trees w/ broad leaves)
  1. Mahogany (heavier than spruce, aircraft skin)
  2. Birch (shock resistant, wing spars and propellers)
  1. Softwood (coniferous trees w/ needle like leaves)
  1. Sitka Spruce (common, free from defects)
  2. Douglas Fir (strength exceed, heavier than spruce, tends to split)
  3. Noble Fir (lighter, superior all properties except hardness and shock resistance. Heavy bending such as spars)
  4. Balsa (light wood, lack structural strength)

Wood: Defects

Acceptable DefectsNon-Acceptable Defects
Cross GrainSpiral and Diagonal grain. Does not diverge from longitudinal axisGrain exceeds longitudinal axis
Wavy, Curly, and Interlocked grainIrregularities do not exceed spiral and diagonal grainWithin the limitations specified in the description of acceptable defects listed
Hard KnotsSound, hard knots up to 3/8 inch diameterWithin the limitations specified in the description of acceptable defects listed
Pin knot ClustersSmall clusters small deviation of grain directionProduce large effect on direction of the grain
Spike KnotsReject wood 
Pitch PocketsCenter portion of the beam atleast 14 inches apart at the same growth ring don’t exceed 1-1/2 inches length and 1/8 inch depthWithin the limitations specified in the description of acceptable defects listed
Mineral StreaksThere is no decayDecay wound
Checks, Shakes and SplitsReject
Compression WoodReject
Compression FailuresPerform microscopic test or toughness test
DecayRed heart or purple heart

Wood: Adhesives

  1. Casein Adhesive – powder from milk, deteriorates over the years
  1. Synthetic Resin Adhesives
  1. Resorcinol Glue – common, two part (resin and hardener)
  2. Phenol-formaldehyde – common aircraft grade plywood. Requires high curing temp and pressure, impractical in field
  3. Epoxy Resins – two part also. Requires less attention.
  1. Plastic Resin – urea-formaldehyde. Water, insect, and mold proof. Rapid deteriorates in hot, moist environment. 

Wood: Inspection

  1. Moisture Metering
  2. Tapping
  3. Probing
  4. Prying (movement – separation)
  5. Smelling
  6. Visual Inspection
  1. External
  2. Internal 

Wood: The bonding process

  1. Preparation
  2. Utilization
  1. Pot Life
  2. Open Assembly Time
  3. Closed Assembly Time
  4. Pressing

Clamping Pressure

  1. Performing


  1. Thermosetting resins – cannot softened and reshaped
  1. Themoplastic resins – can be soften by heat
  1. Cellulose Acetate – transparent and lightweight. Tendency to shrink and yellow. Acetone – softens (Aircraft windshield and side windows)
  2. Polyethylene – plastic bags, insulators, drums.
  3. Vinyl – seat covering, insulations, moldings, tubings. Flexible and resistant to chemical and moisture.
  4. Acrylic Resin – water clear plastic. Light transmission of 92%. (Aircraft windows and windshields) 
  5. Polytetraflouroethylene  (Teflon) – non-lubricated bearings, tubings, electrical devices and other applications. 


  • Process of covering aircraft open structures.

Fabric: Problem Areas

  1. Deterioration – exposure to UV radiation
  2. Tension – max airframe 350 degrees Fahrenheit 

Aircraft Dope

  • Adheres and protects fabric applied to other skin material

Aircraft Fabric and Synthetic 

  1. STC (Supplemental Type Certificate) approved covering material
  • Difference in fabric may be denier(linear density), tenacity (strength of fiber or yarn) , thread count, weight, shrink, tension and weave style
  1. Polyester Filaments 
  2. Covering Procedures 
  3. Installation 
  • Similar to natural fabric. Little slack as possible

Aircraft Fabric – Natural 

  • Used to recover and repair components of an aircraft. 

Recovering Aircraft – same quality used by manufacturer 

FAA – Fedaral Admissions and Regulations

Reinforcing tape – minimum 40 lbs resistance

Finishing tape – surface tape, should have same properties as fabric used in aircraft cover

Lacing Cord – minimum breaking strength of 40 lbs. Rib lace cord should have a micro-crystalline fungicidal wax, paraffin free wax, or beeswax coating to prevent wearing. 

Machine thread – minimum 5 lbs breaking strength 

Hand sewing thread – minimum 14 lbs break strength

Preparation of the structure for covering 

  1. Battery box treatment
  • Asphaltic, rubber based acid-proof coating application in the area of battery by box, brush (addtl. Protection from battery acid)
  1. Worn Holes 
  • Oversized screw holes or worn size 4 self tapping screw holes through ribs and other structures used to attach fabric may be redrilled a minimum 1-1/2 hole diameter distance from the original hole location with #44 drill bit.

Fairing Precaution – may cause a wrinkle to form in the fabric, at the edge of the lap joint. Trailing edges should be adequately secured to prevent movement and wrinkles.

Dope Protection – protective coating such as aluminum foil, cellulose tape, or dope proof paint to protect them against the action of the solvents in the dope.

Sealant Compound

  • used to contain fuel, maintain cabin pressure, reduce fire hazards, exclude moisture, prevent corrosion, and fill gaps and smooth discontinuities on the aircraft exterior.

SEALING – is a process that confines liquids and gases within a given area or prevents them from entering area from which they must be excluded.

Categories of Compounds 

  1. Silicone – white, red, grey. Used where heat resistance is required.
  2. Non-Silicone – any color. Heat resistance not required.

Specification and Classification 

Class A – Brushcoat Sealant. (Thinned with solvent to provide viscosity suitable for


Class B – Filleting Sealant. (Relatively heavy consistency with good thixotropic (low-

slump) properties).

Class C – Faying Surface Sealant. (Medium consistency for good spreadability).

Class D – Hole-Filling Sealant. (Similar to Class B but with very low slump).

Classes E and F – Sprayable sealant


Application Time (except class C)

Squeeze-out Life (class C) [ ex. C-20 minimum 20 hours]

Tack-free Time – hours after thawing 

Cure Time 

120 F or more – bubling may occur

Inside rib lacing [Rib – Fabric – Anti tear strip – reinforcement tape ] – surface tape

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