6.3.2 Flashcards
What are the main lengthwise members in a wing called?
Spars
What are wood spars normally made from?
Sitka spruce
What is meant by a solid wood spar?
When the spar is made from one whole piece of wood
What is meant by laminated wood spar?
When the spar is made from multiple pieces of wood glued together with the grain in the same direction
What forces does a box spar take?
Torsional and bending
What is the main cause of timber shrinkage?
Large cyclic changes of temperature and humidity
What will long exposure to weather or strong sunlight do to wooden aircraft?
It will destroy the weather-proofing qualities of fabrics and surface finishes
What happens when fabric covered ply structures are neglected?
Surface finish will crack allowing in moisture resulting in deterioration
How should you store a wooden aircraft?
In a dry, well ventilated hangar with all inspection panels removed
Before examining glued joints or carrying out repairs what must you ensure on a wooden aircraft?
That it is thoroughly dried out
Upon opening an inspection panel what should you check?
For a smell of fungal growth or dampness
Where does timber and glue deterioration often take place?
The inside of a structure
Why is assessment of glued joints in wooden aircraft structures difficult?
There is no NDT for it and lack of accessibility
Where access is required and no approved scheme exists who do you contact?
Aircraft manufacturer or a CAA approved organisation
How are access holes created?
With a sharp trepanning tool and in a circular shape
If a rectangle access hole is created, what must you ensure with the corners?
That they have the correct radii
When checking a glue line what must be removed?
All protective coatings of paint by scraping
When inspecting a glue line with a feeler gauge, what is the outcome if any penetration is possible?
The joint should be regarded a defective
How is dry rot detected?
Small patches of crumbling wood
What are the signs of water penetration?
Dark discolouration or grey streaks
How is bruising and Cushing caused on wooden aircraft?
Over tightening of bolts
How long is timber cut then stacked prior to shipment for?
60 days
How long is timber usually seasoned in air-drying sheds for?
1-3 years
What is the reason timber is seasoned?
It reduces moisture until it is the same moisture level as atmospheric moisture which allows ease of treatments
Before taking timber for testing what should happen?
Approximately 6 inches should be cut from the end as it might be drier than the rest
What are the two ways of testing for moisture content in timber?
Moisture meter and weighing before and after drying
What is the general correct moisture content levels for timber?
15% with +/-2%
If timber has a rate of growth of less than 6 rings per 25mm what should happen?
It should be rejected
What are the two types of sawing?
Rift sawing and tangential sawing
What is rift sawing?
When you cut timber along the radius of the rings
What is tangential sawing?
When you cut timber at a tangent of the rings
What sawing method is commonly known as flower-face?
Tangential sawing
What is the worst defect for timber to have?
Dote disease
What must you do if you find timber with dote disease?
Burn it
What should you do if you find heart-shake or ring-shake in timber?
Cut it out
When gluing wood together what is important?
Prevent end-grain gluing and apply pressure evenly over the surfaces
What should you do before gluing plywood together?
Sand it to remove surface glazing and loose fibres
What should happen to timber surfaces that are going to be glued?
They should be roughened to form a firm key for adhesives
Why is moisture content important before glueing two pieces of wood together?
The pieces of wood should have the same moisture content to prevent swelling or shrinkage
What should happen to temperature of the wood before gluing?
The wood should be left to settle at room temperature
When gluing two pieces of timber together how should the glue be applied?
To both pieces with a glue spreader
When using solvent adhesive why is it important to make sure it has all evaporated before using?
Bubbles may be created causing weakness
What will happen if you’re applying too much heat to timber and freshly applied glue?
It could scorch the timber and cause the glue to bubble
Where should tests of timber be carried out?
On off cuts
If off cuts aren’t available to test on what should be used?
Representative test pieces
When storing adhesives what should the temperature not exceed?
21C
