Section II Airframe Structures (wood structures) Flashcards
What species of wood is used as a standard for strength properties of other species of wood used an aircraft structures?
Spruce Wood is the benchmark to which all woods are compared.
Is Northern White Pine an acceptable substitute for spruce?
Yes, but only if the pine is a larger size to make up for its lower strength.
Are knots allowed an aircraft wood?
Factors that determine if not are acceptable include the type of knot, location, spacing, and number of knots.
What type of wood quality must be used in the repair of aircraft structures?
The wood must be of aircraft quality and equivalent to its original strength or greater.
What is the difference between laminated wood and plywood?
Laminated wood grain runs parallel and plywood runs 90° with adjacent ply.
What are the two types of glue used for aircraft wood structure repair?
Casein and synthetic resin glue.
What is the method used to prepare plywood for bending?
The water soaked in hot water, and then placed in a form until completely dry.
What are the results of insufficient gluing pressure when making a wooden joint?
The results will normally be thick glue lines, which indicate a weak joint.
What is the recommended clamping pressure for a glued joint?
125 to 150 PSI
how long should a wood glue joint be kept under pressure before removing the clamps?
The pressure time will vary depending on the temperature of the curing room. Higher temps will cause the glue to set faster. It is recommended that it remain under pressure for at least 7 hours.
What are some of the various methods used to apply pressure to joints in aircraft gluing operations?
Brads , nails , screws, clamps, or hydraulic and electrical power presses.
Why does the strength of a scarf joint depend on the accuracy of the two beveled surfaces?
because an inaccurate bevel will reduce the amount of effective glue area.
Why is sanding unacceptable when preparing a joint for splicing?
The dust created from sanding will clog the pores of the wood , preventing proper penetration of glue.
What type of patch is preferred for repair of stressed plywood skin and why?
A Scarf patch is the best repair for plywood , and is preferred for most skin repairs.It uses reinforcements under the patch where the glue joints occur.
Are mineral streaks acceptable in aircraft wood?
Yes, providing careful inspection fails to reveal any decay.
How would you inspect for decay/rot in wood?
Visual (dark discoloration or gray stains ), Odor (musty or moldy), Tapping (sharp solid report), Probe (sharp metal tool), Prying (bonded joints).
How can the moisture content of wood be determined?
Use a moisture meter. The most accurate method is to take a sample of the word, wet, dry it on an oven at a temperature of 100°C to 105°C, reweigh it, and then compute the moisture content by using the formula.
What area of the wood spar may not be spliced?
It may not be spliced under the wing attachment fittings, landing gear fittings, engine mount fittings or lift and interplain Strat fittings.
What type of joint is generally used in splicing structural members in an aircraft?
A scarf joint
What is compression wood and why is it not acceptable for the aircraft structures?
Compression worries would that is characterized by high specific gravity and has appearance of excessive growth of Summer wood (hard, non-porous). This defect is difficult to recognize and is very detrimental to strength. Reject all material containing compression wood.
What are three forms of wood ?
Solid , Ply , Laminate
What are two forms of wood that are acceptable for repair of wooden aircraft skin?
Plywood and laminated wood
What would be the greatest amount of spices placed into one spar?
Two
what is the largest hole diameter that can be repaired in a plywood wing spar when using fabric patch?
1 inch
