Repair of Wooden structures Flashcards
List the common types of wooden spars used in aircraft construction.
Box beam spars
I-beam spars (single or double)
C-section spars
Plain rectangular spars
Routed box spars
What is the importance of using the same materials for repair as the original structure?
Using the same materials for repair as the original ensures compatibility in terms of strength, flexibility, and durability, maintaining the original performance characteristics of the structure.
What is the procedure for repairing a longitudinal crack in a solid wood spar?
Remove the finish on both sides of the spar, then apply reinforcing plates made of spruce or plywood on each side. The plates should be one-quarter as thick as the spar, extend each end of the crack by at least three times the spar thickness, and have ends beveled with a 5:1 taper.
Why must a repaired wooden aircraft structure be as strong as the original structure?
A repaired wooden aircraft structure must be as strong as the original structure to ensure the aircraft maintains its structural integrity and safety standards.
What types of repairs are not allowed on solid wood spars?
Splice repairs on solid wood spars are not permitted under the attachment fittings for the wing root, landing gear, engine mount, lift struts, or inter-plane struts. Additionally, more than two splice repairs on one spar are not allowed.
How should damage on the top or bottom edge of a solid wood spar be repaired?
Clean out the damaged material to a depth no more than one-quarter of the spar thickness, taper the ends of the area to a 5:1 slope, insert and glue a spruce block, and attach reinforcing plates on each side following the same process as for a longitudinal crack.
Describe the scarf repair method for wooden structures.
The scarf repair involves cutting the spar and new material to a proper scarf angle/taper of 1:10 or 1:12. The pieces are clamped, aligned, and a fine-toothed saw is used to ensure a precise match. Glue is applied, and even pressure is used for bonding. Reinforcement plates are glued over the scarf ends.
Why is the trailing edge of a wing prone to moisture damage, and how can it be repaired?
The trailing edge is prone to moisture damage due to clogged drainage grommets that prevent proper drainage. Repair involves cutting away the rotted area, fitting a spruce block, attaching reinforcing plates, and replacing the finishing materials.
How are wing ribs constructed and what materials are typically used?
Wing ribs are usually made of spruce strips with a cross-section of approximately 6-8 mm, softened with steam for bending or forming. Cap strips form the upper and lower surfaces that carry bending loads and attach to the wing skin.
What is the proper method for repairing a broken cap strip between upright members?
Cut the strip to 12 times its thickness, prepare a new matching piece, glue a reinforcing block of spruce to the inside, and cover with plywood faceplates secured until the glue dries.
List the common types of plywood skin repairs.
The common types of plywood skin repairs are:
Fabric patch repair
Splayed patch repair
Surface patch repair
Plug patch repair
Scarf patch repair
What is a splayed patch repair, and what are its limitations?
A splayed patch repair is a flush patch with edges tapered at a 5:1 slope. It is suitable for holes where the largest dimension is not more than 15 times the skin thickness and the skin is not thicker than 0.25 cm.
What is a fabric patch repair, and when is it used?
A fabric patch repair is the simplest method for repairing small holes (not exceeding 2.5 cm in diameter) in plywood. It involves sealing the edges of the hole, applying an approved fabric patch, and overlapping the skin by at least 2.5 cm.
Describe the plug patch repair method.
The plug patch repair involves cutting out the damaged area to a defined shape, creating a plug of the same size and material, and securing it with a doubler ring. The plug is held with glue and screws, and the doubler is nailed to the surrounding skin.
What is the difference between a scarf patch repair and a splayed patch repair?
A scarf patch has edges beveled at a 12:1 slope, is reinforced at the glue joints, and is used for curved or highly stressed areas. A splayed patch is beveled at a 5:1 slope and is used for less critical areas with smaller damage.
