Wooden Structures Flashcards
What type of wings are truss type mainly used on?
Fabric covered
Main woods used in truss type wings?
Spars- Sitka spruce
Compression members- steel or aluminium alloy
Drag and anti-drag wires- steel
What is a box spar?
A box structure built into the wing to take all of the bending and torsional loads. This also helps form the shape of the wing
What are some factors that can weaken glued structures?
Chemical damage Blocked drainage holes Mechanical damage Microbiological Oil leak or fuel contamination
What can be done to preserve woods?
Store in dry clean hangar
Keep out of strong sunlight or bad weather
What should be done before inspecting a wooden aircraft?
Externally inspected for signs of gross deformation or structure failure
What should be checked for when opening panels?
Check for a musty smell which indicated damp or fungus development
What should be done when splits are encountered?
Investigate for cause or further damage
How can the timber and glue joints inspected?
Certain “trouble spots” can be cut out for inspection or just a detailed inspection around those areas
What are access holes and how are they cut?
The cut outs for inspecting timber or glue joints.
Cut with sharp trepanning tool to prevent jagged edges
What should be done first when checking glue lines?
Carefully scrape the paint off, stopping at the wood.
How are the glue lines inspected?
Using a magnifying glass.
If defect is suspected, then probe with thin feeler gauge
What would indicate dry rot and water penetration?
Dry rot- small patches of crumbling wood
Water penetration- dark colouration and grey streaks along the grain.
What is a way to confirm water penetration in the structure?
Remove some screws and check the level of corrosion on them, which indicates what the damage is in the surrounding structure.
What should be done if water penetration is suspected on the surface?
Peel back the fabric and inspect the ply skin for damage
What are some other defects to look for on wooden aircraft?
Shrinkage Elongated bolt holes Bruising and crushing Compression failures Previous repairs
What is joint failure?
When a joint fails due to excessive mechanical loads
How long is timber stacked for before shipping?
60 days
How is timber seasoned?
Naturally in air dryer sheds for 1-3 years
Artificially (ie. kiln-dried)
Why is seasoning done?
To reduce the moisture content to almost be in equilibrium with the surrounding atmosphere.
Allows it to be pretreated.
How can the moisture levels be checked in seasoned wood test pedicels?
Moisture meter
Using an oven to see if the weight changes after heating
How is density measured?
The weight and volume are measured and compared to the level it should be based on the moisture level standard.
How is brittleness checked?
Drop weight machine
Izoid impact test
How is rate of growth measured?
Rings per inch
