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. What is the primary function of a static inverter in an aircraft? → To convert DC power to AC power for avionics and instruments
3. In a wet layup repair, the pot life of a two-part epoxy refers to: → The time after mixing during which the resin remains usable for application
4. When checking valve clearance (tappet clearance) on a reciprocating engine, the piston of the cylinder being checked must be positioned at: → TDC on the compression stroke
5. When curing a composite repair using a heat blanket, which parameter is MOST important to monitor continuously? → Cure temperature ramp rate and hold temperature at the part surface
6. 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
7. What type of hydraulic pump is most commonly used in high-performance aircraft as an engine-driven pump due to its variable output capability? → Variable displacement piston pump
8. An A&P mechanic with an Inspection Authorization (IA) may perform which of the following that a basic A&P may not? → Approve major repairs and alterations for return to service
9. An aircraft engine fails to develop full static RPM during a pre-takeoff run-up. The magneto check is normal. What should be checked next? → Propeller pitch setting and governor operation
10. The purpose of a 'joggle' in a sheet metal part is to: → Allow two overlapping sheets to lie in the same plane where they join a common surface
11. Under the ACS standards, a mechanic must demonstrate knowledge of quality assurance by understanding that an Inspection Authorization (IA) is required to: → Approve an aircraft for return to service after an annual inspection
12. A turbocharged engine's manifold pressure continues to rise after the throttle is advanced to a set position. What component has likely failed? → Wastegate controller
13. Which inspection method is best for detecting surface cracks on aircraft structures? → Dye penetrant inspection
14. FAA Form 337 (Major Repair and Alteration) must be submitted to the FAA within: → 30 days of work completion
15. What is the purpose of 'lapping' valves during engine overhaul? → Create a precise, gas-tight seal between the valve face and the valve seat
16. When drilling holes in a carbon fiber composite for fasteners, which drill bit type is preferred? → Carbide-tipped or solid carbide drill bit
17. After engine overhaul, a break-in run is performed. What oil type should NOT be used during engine break-in? → Synthetic oil
18. Continuing education for a certificated mechanic is: → Not legally mandated but strongly encouraged for professional development
19. A suspected unapproved part (SUP) is discovered during maintenance. The correct action is to: → Tag it, remove it from service, and report it to the FAA
20. What does 'spectrometric oil analysis' (SOAP) detect in aircraft engine maintenance? → Trace metal particles in engine oil that indicate wear of specific engine components
21. An engine oil analysis report shows elevated iron and chrome levels. What engine components are most likely experiencing abnormal wear? → Piston rings and cylinder walls
22. Which method is best for locating hydraulic leaks? → Visual and tactile inspection
23. What is 'nitriding' as applied to aircraft engine crankshafts? → A surface hardening process using nitrogen gas to increase wear resistance
24. What is the MAIN reason that cure pressure is applied during composite repair? → To consolidate plies, remove voids, and ensure intimate fiber-to-matrix contact
25. Which tool is essential for checking the torque of aircraft fasteners? → Torque wrench
26. Which part of the regulations pertains to airworthiness certification? → Part 21
27. What is the primary purpose of Advisory Circular AC 43.13-1B? → To provide acceptable methods and techniques for aircraft inspection and repair
28. Which instrument uses a Wheatstone bridge circuit to measure fuel quantity? → The capacitance-type fuel quantity system
29. An aircraft with an expired annual inspection is considered: → Unairworthy and may not be operated
30. 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