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Airframe
WOOD STRUCTURES
Question | Answer |
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Which species of wood is considered to be the standard when comparing other woods for use in aircraft structure? | Sitka spruce. |
What is the basic difference between plywood and laminated wood? | The grain in each layer of laminated wood runs in the same direction. The grain in the layers of plywood runs at 90 degrees or 45 degrees to each other. |
What kind of glue is recommended for making a repair to a wooden aircraft structure? | Synthetic resin glue. |
How is aircraft plywood prepared for making a compound bend? | The wood is soaked in hot water until it is pliable. |
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. |
How long should a glue joint be kept under pressure when splicing a wooden aircraft wing spar? | For at least seven hours. |
Are mineral streaks in a piece of structural aircraft wood reason for rejecting the wood? | No, if there is no evidence of decay in the wood. |
Which area of a wooden aircraft wing spar must not contain any splice? | There must be no splice under wing-attach fittings, landing gear fittings, engine mount fittings, or lift and interplane strut fittings. |
How is compression wood identified? | It has a high specific gravity, it appears to have an excessive growth of summer wood, and little contrast between the 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. |