Airframe Mechanic Aircraft Structures Questions and Answers — Questions and Answers
Question 1: Which type of aircraft fuselage construction relies primarily on the strength of its skin or covering to carry the main structural loads?
- Truss
- Semi-monocoque
- Geodetic
- Monocoque (Correct answer)
Correct answer: Monocoque
A monocoque fuselage design, similar to an aluminum can, relies almost entirely on its skin to carry bending and torsional stresses. It has very few internal stiffening members, which differentiates it from the semi-monocoque design.
Question 2: A mechanic is inspecting a wing spar and notices that the lower surface of the spar is slightly elongated, while the upper surface is slightly compressed. Which type of stress is this indicative of?
- Torsion
- Shear
- Bending (Correct answer)
- Tension
Correct answer: Bending
Bending stress is a combination of tension and compression. When a wing bends upwards due to lift, the top surface is subjected to compression, and the bottom surface is subjected to tension.
Question 3: In a semi-monocoque fuselage, what are the primary functions of the longerons and stringers?
- To provide the aerodynamic shape and serve as the primary covering.
- To absorb landing shock and transfer it to the wing structure.
- To provide longitudinal strength and stiffen the skin against buckling. (Correct answer)
- To create separate compartments for fuel and cargo.
Correct answer: To provide longitudinal strength and stiffen the skin against buckling.
In semi-monocoque construction, longerons and stringers are longitudinal members that provide the primary bending strength and stiffen the skin, preventing it from buckling under load. The skin carries a significant portion of the load but is reinforced by this internal framework.
Question 4: While performing a 100-hour inspection on an aluminum aircraft operating in a coastal, high-humidity environment, a mechanic discovers fine, thread-like lines of corrosion under the paint, starting from a scratched area. What is this type of corrosion called?
- Pitting
- Filiform corrosion (Correct answer)
- Intergranular corrosion
- Fretting corrosion
Correct answer: Filiform corrosion
Filiform corrosion is a specific type of corrosion that occurs on metal surfaces with an organic coating. It appears as thread-like filaments that grow under the paint film, often starting from a break or scratch in the coating. It is common on aluminum in humid environments.
Question 5: What are the principal structural members of a wing that run from the root to the tip and carry most of the bending loads?
- Ribs
- Stringers
- Formers
- Spars (Correct answer)
Correct answer: Spars
Spars are the main spanwise structural members of the wing. They are designed to take the primary bending and shear loads generated by lift forces during flight.
Question 6: A twisting force is applied to an aircraft engine mount during operation. What is the primary type of stress this component must resist?
- Compression
- Shear
- Torsion (Correct answer)
- Tension
Correct answer: Torsion
Torsion is the stress that results from a twisting force. Engine torque creates a rotational force that the engine mounts and surrounding structure must be designed to withstand.
