AET Cheat Sheet 2026

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

1. When calibrating a pressure transducer used in an aircraft fuel quantity system, which test equipment is most appropriate? → Dead-weight tester or precision pneumatic pressure calibrator
2. What is the purpose of a Continued Airworthiness document issued with an STC? → To provide the maintenance instructions necessary to keep the STC'd modification airworthy
3. What does the international ESD symbol (a hand inside a triangle with a diagonal bar) on an avionics component label indicate? → The component is ESD-sensitive and requires proper ESD handling procedures
4. A strobe light on an aircraft fails to flash but the power supply capacitor charges correctly. The fault most likely lies in the: → Flash tube or trigger circuit
5. In an aircraft bus tie system, what is the function of a Bus Tie Breaker (BTB)? → Connect or isolate AC buses to allow power transfer between sources
6. In a microcontroller used in aircraft fuel management, what is the purpose of a watchdog timer? → To reset the processor if software fails to service the timer within a set interval
7. Which set of flight instruments receives input directly from the pitot-static system? → Altimeter, airspeed indicator, and vertical speed indicator (VSI)
8. A 4-bit binary counter has a modulus of: → 16
9. Which bus architecture is commonly used in modern commercial aircraft for avionics data communication? → ARINC 429
10. What is the significance of documentation in Avionics Systems? → It provides a record for accountability, quality assurance, and legal compliance
11. Which regulatory body oversees the airworthiness standards for transport-category aircraft avionics installations? → FAA Aircraft Certification Service
12. What is the purpose of IRS (Inertial Reference System) alignment and why must it be performed stationary? → To establish a precise north reference and initial position before computing navigation
13. Aircraft wiring that shows discoloration (brown or black insulation) most likely indicates: → Overheating due to excessive current or poor connection
14. When performing a continuity check on an aircraft wiring harness, the technician should FIRST: → Disconnect power and verify the circuit is de-energized before testing
15. What is the primary architectural characteristic of the ARINC 429 data bus used in commercial transport avionics? → Unidirectional simplex bus with one transmitter and up to 20 receivers
16. What is the role of a Distance Measuring Equipment (DME) transponder ground station? → Reply to aircraft interrogation pulses to allow slant-range distance computation
17. When an avionics technician discovers a discrepancy during an inspection that cannot be corrected before flight, what document must be used to record it? → Discrepancy log in the aircraft maintenance record
18. Ground-wave propagation is associated with which frequency range used in aviation? → HF (2–30 MHz)
19. When analyzing data from an avionics test set, which of the following is a crucial aspect to verify? → The accuracy of the measurements and comparison with expected values
20. In an Inertial Reference System (IRS), what sensors are used to measure angular rate? → Ring laser gyroscopes or fiber optic gyroscopes
21. On a horizontal situation indicator (HSI), what does the course deviation indicator (CDI) needle represent when centered? → Aircraft is on the selected VOR radial or localizer course
22. Which test instrument captures and simultaneously displays multiple digital signal states to aid in troubleshooting microprocessor-based avionics? → Logic analyzer
23. An Aircraft Service Difficulty Report (SDR) is required when? → When a failure, malfunction, or defect that could endanger safe operation is discovered
24. Under 14 CFR Part 91.411, altimeter systems and altitude reporting equipment used in controlled airspace must be tested and inspected within the preceding: → 24 calendar months
25. What is the nominal voltage of a standard 14-volt aircraft electrical system when measured at the bus with the alternator online? → 13.8–14.5 volts
26. What is the best practice for communicating maintenance findings to other team members? → Provide clear, concise, and understandable information
27. When troubleshooting an aircraft electrical system and the ammeter shows a discharge indication with the engine running, what is the most likely cause? → The alternator is not producing output or is off-line
28. What does 'BITE' stand for in avionics maintenance contexts? → Built-In Test Equipment
29. An ARINC 664 (AFDX) network in a modern aircraft serves as a replacement for which older avionics data bus architecture? → ARINC 429 point-to-point buses
30. Under 14 CFR Part 39, an Airworthiness Directive (AD) is legally classified as: → A Federal Regulation with the force of law