ACS Non-Destructive Testing (NDT) Methods 1 — Questions and Answers
Question 1: Which NDT method is most effective for detecting surface and near-surface cracks in ferromagnetic aircraft components?
- Ultrasonic testing
- Dye penetrant inspection
- Magnetic particle inspection (Correct answer)
- Eddy current testing
Correct answer: Magnetic particle inspection
Magnetic particle inspection (MPI) is specifically designed for ferromagnetic materials and can reveal both surface and subsurface discontinuities by applying a magnetic field and iron particles.
Question 2: What is the primary purpose of the developer in dye penetrant inspection?
- To clean the surface before penetrant application
- To draw the trapped penetrant back to the surface to form an indication (Correct answer)
- To increase the viscosity of the penetrant
- To remove excess penetrant from the surface
Correct answer: To draw the trapped penetrant back to the surface to form an indication
The developer acts as a blotter, drawing the entrapped penetrant out of discontinuities to form a visible indication on the surface.
Question 3: In dye penetrant inspection, what is the correct sequence of steps?
- Clean → Apply developer → Apply penetrant → Inspect
- Apply penetrant → Clean → Apply developer → Inspect
- Clean → Apply penetrant → Remove excess → Apply developer → Inspect (Correct answer)
- Apply developer → Apply penetrant → Clean → Inspect
Correct answer: Clean → Apply penetrant → Remove excess → Apply developer → Inspect
The correct sequence is: pre-clean the surface, apply penetrant and allow dwell time, remove excess penetrant, apply developer, then inspect under appropriate lighting.
Question 4: Which type of visual inspection tool is used to inspect the interior of an engine cylinder without disassembly?
- Micrometer
- Borescope (Correct answer)
- Dial indicator
- Feeler gauge
Correct answer: Borescope
A borescope is an optical instrument with a rigid or flexible tube used to inspect the interior of inaccessible areas such as engine cylinders without requiring disassembly.
Question 5: What is the minimum dwell time typically specified for dye penetrant inspection of standard discontinuities in aluminum alloy parts?
- 30 seconds
- 1 minute
- 5 to 30 minutes (Correct answer)
- 1 to 2 hours
Correct answer: 5 to 30 minutes
For most aluminum alloy parts, penetrant dwell times typically range from 5 to 30 minutes to allow adequate capillary action into discontinuities, as specified by the applicable process specification.
Question 6: Which NDT method is LEAST effective for detecting defects in non-metallic composite materials?
- Ultrasonic testing
- Radiographic inspection
- Magnetic particle inspection (Correct answer)
- Thermographic inspection
Correct answer: Magnetic particle inspection
Magnetic particle inspection requires the material to be ferromagnetic; composite materials are non-metallic and non-ferromagnetic, making MPI completely ineffective for composites.
Question 7: According to FAA regulations, who may perform NDT inspections on certificated aircraft?
- Any FAA-certificated pilot with instrument rating
- Only FAA-certificated airframe and powerplant mechanics with appropriate training and authorization (Correct answer)
- Any person supervised by a licensed mechanic
- Only FAA inspectors
Correct answer: Only FAA-certificated airframe and powerplant mechanics with appropriate training and authorization
NDT inspections on certificated aircraft must be performed by FAA-certificated A&P mechanics who have received specific training and authorization in the applicable NDT method per the manufacturer's approved data.
ACS Non-Destructive Testing (NDT) Methods 1
Which NDT method is most effective for detecting surface and near-surface cracks in ferromagnetic aircraft components?