1. Aircraft Wood Structures Spokane Community College
Airframe

2. Objectives
Understand the different species used in aircraft wood construction
Understand the defects found in wood construction

3. Current Wood Structure Applications
Why wood? Strength to weight ratio
Disadvantage
labor intense
Maintenance
Bellanca Viking
Still used for homebuilts and some production aircraft
Standards set for wood used in AC
AN quality standards
Best wood – Sitka Spruce – uniform, strength and shock resistance
Buy from reputable companies – derives from Alaska and B.C.
AN-W-2 specifications
Other substitutions are acceptable as long as they follow the criteria
AC B – outlines
SLIDE

4. Addison’s B-40

5. Oldest Flying Boeing

6. Great Lakes 2T1A-2

7. Fully Aerobatic

8. Substitutions are acceptable as long as they meet the original characteristics of the original product
Must be assessed by the mechanic Must be free of defects
SLIDE:

9. Wood Construction and Defects
Shake – Separation or crack
Check – Develops during drying

11. Good wood:
Slope of the grain – Slide
Growth rings per inch – six minimum in soft woods
Exceptions – Port Oxford white cedar and Douglas Fir – Eight minimum
Must be true, dry etc.
Talk about quality of wood.
Plywood – Manufactured form African Mahogany and birch veneers over hardwood cores of bass wood or popular
May also be basswood plywood – lighter and more flexible but less structural
Bonded 90 degrees to each other
Specifications – MIL-P-6070 – calls for testing after immersion in boiling water for 3 hours
Laminated wood – Each layer is bonded with the grain running parallel
Stronger but less flexible
Much more resistant to warping
Used for curved components – wing tip bows and fuselage formers

12. Reasons for rejection
Cross Grain – Wood in which the direction of the fibers/grain deviate from a line parallel to the sides in excess of listing.
Wavy, curly and interlocked grain – disruption in the grain pattern in the form of waves, bird’s eyes or alternate spirals in excess of limitations.
Hard Knots – solid knots which show weakness or decay surrounding them.

13. Reasons for rejection
Pin knot clusters – knots with diameters less than ½ inch in a grouping are not acceptable if the show a large affect on the grain.
Pitch pockets – pockets which may or may not contain pitch are not acceptable unless they fall within limitations.
Mineral streaks – discoloration which shows excessive minerals in the wood are acceptable only if they show no signs of rot or decay.

14. Reasons for rejection
Checks, shakes or splits – cracks either uniform or disruptive in the grain are reasons for rejection.
Compression wood – buckling of the grain that appear as streaks in the surface of the wood and are at right angles to the grain are reason for rejection.
Decay – attack by organisms such as fungi and insects and can be powdery (dry rot) or wet are always reasons for rejection.

15. Inspection What else would you use to inspect a wood structure? Tools:
Pick
Rule
Feeler gauge
Mirror, Flashlight
What else would you use to inspect a wood structure?