ACS Cheat Sheet 2026

The 30 highest-yield ACS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which NDT method is most appropriate for detecting delaminations in a carbon fiber reinforced polymer (CFRP) aircraft panel? → Ultrasonic testing (pulse-echo or through-transmission)
2. Aircraft brake assemblies with multiple discs (stacked rotors and stators) are typically used on: → High-performance and large transport category aircraft requiring high heat capacity
3. Which inspection method is best for detecting surface cracks on aircraft structures? → Dye penetrant inspection
4. Which method is best for locating hydraulic leaks? → Visual and tactile inspection
5. Which tool is essential for checking the torque of aircraft fasteners? → Torque wrench
6. Which part of the regulations pertains to airworthiness certification? → Part 21
7. During a preflight fuel check, a pilot/mechanic finds a small amount of water in the fuel sample. The correct action is: → Continue sampling and draining until no water is found, verifying the sample is clear
8. On a radiographic film, a darker area (higher film density) typically indicates what about the inspected material? → A void, crack, or area of reduced material density allowing more radiation to pass through
9. When installing a new wheel bearing on aircraft landing gear, the bearing should be: → Packed with the correct grease per the AMM specification before installation
10. What is the correct tube material for a high-pressure aircraft fuel line (above 1,500 PSI)? → Corrosion-resistant steel (CRES / stainless steel) or titanium
11. Which part of the maintenance manual specifies troubleshooting steps? → Troubleshooting section
12. What is the most important ethical consideration for ACS professionals in composite materials & repair? → Maintaining objectivity, integrity, and confidentiality in all professional work
13. Which NDT method is LEAST effective for detecting defects in non-metallic composite materials? → Magnetic particle inspection
14. Which NDT method is most effective for detecting surface and near-surface cracks in ferromagnetic aircraft components? → Magnetic particle inspection
15. What is the minimum dwell time typically specified for dye penetrant inspection of standard discontinuities in aluminum alloy parts? → 5 to 30 minutes
16. Which condition requires immediate replacement of a landing gear actuating cylinder? → Internal bypass causing the gear to drift from locked position under load
17. What part regulates the speed of a propeller? → Governor
18. What continuing education is typically required in weight & balance? → Regular training to stay current with industry standards, regulations, and best practices
19. What type of rivet is commonly used for aircraft assembly? → Solid rivet
20. What is the main purpose of the carburetor in an aircraft engine? → Mix air and fuel
21. What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system? → To remove water and sediment from fuel before it reaches the carburetor or fuel injector
22. What is the primary purpose of an aircraft's hydraulic system? → Operate flight control surfaces
23. What is the purpose of Safety Management Systems (SMS)? → To manage and mitigate safety risks
24. When is it mandatory to bond and ground an aircraft during fueling? → Always, before fueling begins, to prevent static discharge ignition of fuel vapors
25. Which tool measures cylinder wear in an engine? → Cylinder bore gauge
26. What type of fuel is used in most turbine-powered aircraft operated in the United States? → Jet-A (kerosene-based turbine fuel)
27. When must a maintenance log entry be made? → Every time maintenance is performed
28. What continuing education is typically required in electrical systems & avionics? → Regular training to stay current with industry standards, regulations, and best practices
29. What type of seal is most commonly used in aircraft landing gear actuating cylinders? → Lip-type dynamic seals (O-rings with backup rings)
30. Which type of visual inspection tool is used to inspect the interior of an engine cylinder without disassembly? → Borescope