Airframe Mechanic Certification Aircraft Structures 2 — Questions and Answers
Question 1: What type of stress acts perpendicular to the cross-section of a structural member and tends to pull it apart?
- Compression
- Shear
- Tension (Correct answer)
- Torsion
Correct answer: Tension
Tension is a pulling force that acts perpendicular to the cross-section and tends to elongate or pull a structural member apart.
Question 2: In a semi-monocoque fuselage, which structural members run longitudinally and carry primary bending loads?
- Formers
- Stringers (Correct answer)
- Bulkheads
- Gussets
Correct answer: Stringers
Stringers run longitudinally along the fuselage and carry primary bending and axial loads in a semi-monocoque structure.
Question 3: What is the primary purpose of a wing's main spar?
- Provide attachment points for control surfaces
- Carry bending and shear loads from lift (Correct answer)
- Maintain the aerodynamic contour of the wing
- Prevent fuel from leaking between bays
Correct answer: Carry bending and shear loads from lift
The main spar is the primary load-carrying member of the wing, designed to resist bending and shear forces generated by lift.
Question 4: Which aluminum alloy series is most commonly used in aircraft primary structure due to its high strength-to-weight ratio?
- 1100 series
- 3003 series
- 2024 series (Correct answer)
- 5052 series
Correct answer: 2024 series
2024-T3 aluminum alloy is widely used in aircraft primary structure because of its excellent strength-to-weight ratio and fatigue resistance.
Question 5: A crack found running parallel to the length of a fuselage stringer is most likely caused by which type of stress?
- Torsional stress
- Compressive stress
- Hoop stress (Correct answer)
- Shear stress
Correct answer: Hoop stress
Hoop (circumferential) stress from pressurization acts perpendicular to the fuselage axis, causing cracks that run parallel to longitudinal members.
Question 6: What document defines the allowable damage limits and repair procedures for a specific aircraft structure?
- Aircraft Flight Manual (AFM)
- Structural Repair Manual (SRM) (Correct answer)
- Minimum Equipment List (MEL)
- Weight and Balance Manual
Correct answer: Structural Repair Manual (SRM)
The Structural Repair Manual (SRM) provides manufacturer-approved damage limits, inspection criteria, and repair procedures for the airframe.
Question 7: In aircraft construction, what is the function of a gusset plate?
- Seal fuel bay boundaries
- Reinforce joints between structural members (Correct answer)
- Provide aerodynamic fairings at wing roots
- Support engine mounts
Correct answer: Reinforce joints between structural members
Gusset plates are triangular or shaped reinforcing plates used to strengthen joints and distribute loads between intersecting structural members.
Airframe Mechanic Certification Aircraft Structures 2
What type of stress acts perpendicular to the cross-section of a structural member and tends to pull it apart?