Aircraft Structures and Composites Flashcards

In a semi-monocoque fuselage, what is the primary function of stringers?

Answer: To transfer skin stress to the formers and prevent buckling of the skin.

Stringers are longitudinal members that run the length of the fuselage. Their main purpose is to stiffen the skin and prevent it from buckling under compression and shear loads. They also transfer the stresses from the skin to the transverse frames (formers).

An AME is inspecting a composite control surface and finds a defect where the layers of the laminate have separated. What is this type of damage called?

Answer: Delamination

Delamination is the specific term for the separation of layers or plies within a laminated composite material. Debonding refers to the failure of an adhesive joint between two separate components, such as the skin and a stiffener.

Which of the following NDT (Non-Destructive Testing) methods is most suitable for detecting subsurface delaminations in a carbon fiber composite wing skin that are not visible from the surface?

Answer: Ultrasonic Inspection

Ultrasonic inspection is the most widely used and effective method for detecting subsurface defects like delaminations and disbonds in composite structures. High-frequency sound waves are introduced into the material, and the reflections are analyzed to identify internal flaws. Dye penetrant and visual inspections are limited to surface defects, and eddy current is primarily used for conductive materials.

A technician is performing a sheet metal repair on a non-pressurized fuselage section. The maintenance manual specifies installing a doubler over the damaged area. What is the standard practice for the material thickness of this doubler?

Answer: One gauge thicker than the original skin.

For a standard doubler repair, the doubler should be made of the same material as the original skin but should be one gauge (or size) thicker to ensure the repair restores the required strength to the damaged area.

What is the primary aerodynamic benefit of installing winglets on an aircraft's wingtips?

Answer: To reduce induced drag by weakening wingtip vortices.

Winglets are designed to reduce induced drag, which is created by wingtip vortices. By limiting the formation and strength of these vortices, winglets improve the wing's efficiency, leading to benefits like reduced fuel consumption and increased range.

During an inspection of an aluminum alloy landing gear component, a type of corrosion is found that proceeds along the grain boundaries of the metal. This form of corrosion is not readily visible on the surface in its early stages. What is this type of corrosion called?

Answer: Intergranular Corrosion

Intergranular corrosion is an attack along the grain boundaries of an alloy. It is often caused by improper heat treatment and can significantly weaken the material from within, making it difficult to detect visually until it becomes severe.