Oral non metallic structure questions

Wood questions only!

Which species of wood is considered to be the standard when comparing other woods for use in aircraft structure?

Stika spruce

What is the basic a difference between plywood and laminated wood?

Laminated wood grains runs in same direction, while plywood runs at 90 degrees or 40 degrees.

How is pressure applied to the glued joint when splicing a wooden aircraft wing spar?

With cabinetmakers parallel clamps.

How much pressure must be applied to a glue joint in a piece of softwood to produce a strong joint?

125 to 150 pounds per square inch

What is the correct repair to a wooden aircraft wing spar if the wing-attach bolt holes in the spar are elongated?

Splice in a new section of the spar and drill new holes.

What kind of repair is recommended for a hole in the plywood skin of an aircraft wing?

A scarf patch.

What is the recommended taper for a splayed patch in a plywood aircraft skin?

5 to 1.

What is the recommended taper for a scarf patch in a plywood aircraft skin?

12 to 1.

Why should sandpaper never be used when preparing a scarf joint in a wing spar for splicing?

The dust caused by sanding will plug the pores of the wood so the glue cannot get in to form a good bond.

What is the largest hole in a plywood wing skin that can be repaired with a fabric patch?

One inch in diameter.

Why are light steel bushings often used in bolt holes in a wooden wing spar?

The bushing keeps the spar from being crushed when the nut on the attachment bolt is tightened.

Which area of a wooden aircraft wing spar must not contain any splice?

Wing attachment fittings, landing gear fittings, engine mount fittings, or lift and interplane strut fittings.

How is compression wood identified?

High specific gravity, excessive growth of summerwood, and little contrast between teh spring wood and the summer wood.

What is done to a splice in a wooden aircraft wing spar to strengthen the splice?

Reinforcing plates are glued to both sides of the splice.

Why must abrupt changes in the cross-sectional area of a wooden structural member be avoided?

Abrupt changes in the cross-sectional area of a structural member concentrate stresses and can cause failure.