Airframe Structures and Repair Flashcards
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Read the first 6 Airframe Structures and Repair flashcards as text
A technician discovers a small, localized area of corrosion on an aluminum alloy surface characterized by small holes or cavities. When the white-gray powdery deposit is removed, tiny pits are visible. What type of corrosion is this?
Answer: Pitting corrosion
Pitting corrosion is a localized form of corrosion that creates small holes or pits in the metal. It is commonly identified by a white or gray powdery deposit, and upon removal, small cavities are visible on the surface. It is a serious issue, especially on aluminum and magnesium alloys.
When performing a repair on a composite structure, a technician uses a scarf patch. What is the primary advantage of a scarf repair compared to an external patch repair?
Answer: It provides a smooth, aerodynamic surface and efficient load transfer.
A scarf repair involves tapering the edges of the damaged area and the patch, creating a flush, bonded joint. This technique is preferred for its ability to restore a smooth aerodynamic profile and for providing a more uniform distribution of stress across the repair, leading to efficient load transfer.
A maintenance technician needs to install a solid shank rivet with the identification code AN470AD4-8. What does the '4' in this code represent?
Answer: The rivet diameter in thirty-seconds of an inch.
In the AN (Army-Navy) and MS (Military Standard) rivet identification system, the number immediately following the material code indicates the rivet's shank diameter in 32nds of an inch. Therefore, a '4' represents a diameter of 4/32 or 1/8 inch.
What is the primary structural difference between a monocoque and a semi-monocoque fuselage construction?
Answer: Semi-monocoque fuselages use a substructure of stringers and formers to reinforce the skin.
A true monocoque fuselage relies almost entirely on its skin to carry bending and twisting loads. A semi-monocoque design, which is far more common in modern aircraft, reinforces the skin with longitudinal members (stringers and longerons) and transverse members (frames, formers, and bulkheads). This substructure shares the loads with the skin, preventing buckling and increasing overall strength.
A technician finds a crack in a non-critical aluminum skin panel during an inspection. As a temporary repair to prevent the crack from propagating, what is the most appropriate immediate action?
Answer: Stop-drill the ends of the crack.
Stop-drilling is a common and accepted procedure to arrest the propagation of a crack. By drilling a small hole at each tip of the crack, the stress concentration at the crack's sharp end is redistributed around the radius of the hole, which effectively stops or slows its growth until a permanent repair can be made.
The process of heating an aluminum alloy to a specific temperature, holding it there for a predetermined time, and then rapidly cooling it (quenching) is performed primarily to:
Answer: Improve its strength and hardness.
This process describes solution heat treatment followed by quenching. For heat-treatable aluminum alloys (like the 2xxx, 6xxx, and 7xxx series), this procedure is the first step in a hardening process. It puts the alloying elements into a solid solution, and the rapid quench traps them, significantly increasing the material's strength and hardness after aging.