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OP Wood Composites
| Question | Answer |
|---|---|
| What are the three forms of wood commonly used in aircraft construction? | Solid, laminated, Plywood. |
| What type of wood should be used when splicing or reinforcing plywood webs? | The same type of plywood originally used. |
| Name at least four different types of defects found in wood? | Knots, checks, splits, pitch pockets, cross grain, curly grain, decay, dry rot. |
| Can a section of wood containing a hard knot be used? | Yes within limits that include size, location, type and number of knots. |
| What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration? | Casein glue. |
| What are the three types of glue used in modern aircraft construction and repair? | Casein and synthetic glue such as Resorcinol glue, Phenol=formaldehyde glue, Epoxy resin glue. |
| Is compression wood acceptable for structural repairs? | No. |
| Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining? | To allow the moisture content to equalize, thereby minimizing dimensional changes in the wood? |
| Why is it important to consider the open-assembly time when gluing wooden structures? | If the maximum open assembly time is exceeded, the joint may fail since the glue may begin setting up before the joint is assembled. |
| Why is it important to apply the proper clamping pressure to a glue joint? | Clamping forces air out of the joint, brings the wood surfaces together evenly and is, in part, responsible for the strength of the glue joint. |
| Describe some of the methods used to apply pressure to glue joints. | Clamps, nailing strips, power presses, brads, nails, small screws. |
| What minimum curing temperature should be observed when joing wood with various adhesives? | 70 degrees fahrenheit or as specified by the manufacturer. |
| When inspecting wood structures, why might it be important to consider stains and discolored areas? | Stains and discoloration may accompany decar and/or rot. |
| Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar? | Remove the section containing the elongated bolt holes and splice in a new section or replace the entire spar. |
| What type of joint is used to splice a solid or rectangular wood spar? | A scarf joint. |
| In what areas are splices to a wood spar prohibited? | Under an attachment fitting for a wing root, landing gear, engine mount, lift, or inter plane strut. |
| What is the maximum number of splices allowed for any single spar? | 2. |
| Describe the characteristics of a scarf joint? | The pieces to be joined are tapered or beveled to a slope of 1 to 10 or 1 to 12. |
| Why must the beveled cut be accurate to both pieces of wood being repaired with a scarfed joint. | The two pieces must match exactly to ensure a tight glue joint. |
| What are the two primary uses for ply wood in aircraft construction? | Gussets (reinforcing plates) and aircraft skin. |
| Provide examples of at least 3 types of plywood skin repairs? | Splayed patches, surface patches, plug patches, scarfed patches. |
| What type of patch should be used to repair small holes in thin plywood skin if the skin is less than 1/10 inch thick? | A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thicknesses of the skin. |
| What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded form the joint? | Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate. |
| Whay are lightweight steel bushings sometimes used in wooden structures? | Bushings prevent the wood from being crushed when bolts are tightened. |
| What is the purpose of large surface area washers when used on wooden structures? | Large washers provide additional bearing area for hardware to help preclude damage to wood when hardware is tightened. |
| Name several facings and core materials used in bonded honeycomb structures intended for special applications? | Stainless steel, titanium, magnesium, plywood, glass, nylon, cotton cloth. |
| Describe the construction of a bonded honeycomb structure? | It is a laminated structure that has a solid facing bonded to either side of a core consisting of open, six sided cells. |
| What must be done with a damaged area in a bonded honeycomb structure prior to beginning repairs? | The area must be inspected to determine the damaged area prior to completely removing the damaged material. |
| A drill bit used for drilling composites should operate at approximately what speed? | Use an air driven tool capable of a free speed of up to 20000 rpm. |
| What are the most common causes for delamination of a composite structure? | Sonic vibration, expansion of internal moisture, liquid leakage, manufacturing error. |
| What type of defect in, or damage to, a bonded honeycomb structure can be repaired using the potted repair method? | Filling a hole. |
| Name some of the factors that cause crazing in transparent plastic windows and windshields? | Ultra violet light, stress, solvents, improper handling. |
| How should a hole be drilled in Plexiglass to avoid damage to the hole when the drill breaks through to the underside? | Back up the plastic with a piece of wood and feed the drill slowly. |
| What species of wood is used as a standard in aircraft structures? | Spruce which all substitutions are compared to. |
| Is northern white pine an acceptable substitute for spruce? | Yes but of larger size to make up for lower strength. |
| What type of quality of wood must be used in repairs of aircraft structures? | Aviation grade and of equal strength as original manufacture. |
| What is the difference between laminated and plywood? | Both contain two or more layers, laminated layers run parallel to each other and ply run perpendicular to each other. |
| What method is used to bend plywood? | Soaked in the placed in a form until its dry. |
| What is the recommended clamping pressure for glue joints? | 125-150 PSI. |
| How long should a glued wood joint be kept under pressure before removing the clamps? | Cured at 70 degrees or above, at 85 degrees 7 hours is recommended. Full joint strength will be obtained after 48 hours. |
| Why is sanding not acceptable when preparing a joint for splicing? | Dust particles will get in the joint and prevent proper penetration of the glue. |
| What is the preferred method of repair for a stressed plywood skin? | Scarf patch with a 12-1 slope and reinforcements under the patch. |
| Are mineral streaks acceptable in wood? | Yes if inspection fails to reveal decay. |
| What are the two forms of wood acceptable for repair of an aircraft wooden skin? | Laminate or plywood. |
| What is the largest hole diameter that may be repaired with a fabric patch on a plywood skin? | 1 inch. |
| How is pressure applied to the glued joint when splicing a wooden aircraft wing spar? | With cabinetmakers parallel clamps. |
| 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 |
| 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? | Can concentrate stresses and cause failure. |
Created by:
g153511
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