The CAET exam covers 11 categories across 100 questions. But not all categories are weighted equally — some are worth double what others are. If you study each topic the same amount, you're leaving points on the table.
This is a category-by-category breakdown of what to expect, what to study, and where to focus for maximum impact. It's based on the CAET assessment objectives and real exam analysis, aligned to the knowledge domains defined in ASTM F3245-25.
Whether you're six months out from the test or cramming over a weekend, this guide tells you where to put your time.
CAET Exam Category Weights (Estimated)
Percentages are estimated based on alignment with ASTM F3245-25 knowledge domains and exam analysis. They are not official AEA figures. Actual category weights may vary by exam version.
Category 1: DC Fundamentals
~10% · HIGHWhat it covers: Ohm's law, Kirchhoff's laws, series/parallel circuits, power calculations, battery types, voltage dividers, Thevenin/Norton equivalents.
What to expect: Calculation-based questions. "What's the current through R2?" style. You'll be given a circuit and asked to solve for voltage, current, resistance, or power at specific points.
Sample concept: Given a series-parallel circuit, calculate total resistance, current through a branch, and voltage drop across a component. If you can do that confidently, you're solid on this category.
Study priority: HIGH — builds the foundation for everything else on the exam. If you don't know DC fundamentals, the systems categories will be harder to understand.
Pro tip: Know your formulas cold. V=IR, P=IV, series R adds, parallel R uses the reciprocal formula (1/Rt = 1/R1 + 1/R2 + ...). Practice enough circuits that these become automatic, not something you have to think about.
Category 2: AC Fundamentals
~8% · HIGHWhat it covers: Sine waves (frequency, period, amplitude, RMS), inductors, capacitors, impedance, reactance, power factor, transformers, resonance.
What to expect: Mix of conceptual and calculation. "What happens to XL when frequency doubles?" "If the transformer turns ratio is 10:1, what's the secondary voltage?" Expect questions that test whether you understand the relationships, not just whether you can plug into a formula.
Study priority: HIGH — AC concepts show up everywhere in avionics, from power systems to communication to navigation signals.
Pro tip: Focus on practical AC concepts — transformer ratios, impedance effects on circuits, power factor — not complex phasor math. The exam tests understanding of behavior, not your ability to solve j-notation equations.
Category 3: Solid-State Devices
~6% · MEDIUMWhat it covers: Diodes (rectifier, Zener, LED), transistors (BJT switching), voltage regulators, basic power supply circuits.
What to expect: Functional questions. "What does a Zener diode do in this circuit?" "What happens when the base of a transistor loses its bias voltage?" Not detailed semiconductor physics — they're testing whether you know what the components do in a real circuit.
Study priority: MEDIUM — a smaller portion of the exam, but the concepts are straightforward if you approach them practically.
Pro tip: Know what each device DOES in a circuit, not how it works at the atomic level. A Zener regulates voltage. A BJT acts as a switch. A full-wave bridge converts AC to DC. Practical, not academic.
Category 4: Digital Electronics & Data Buses
~16% · CRITICALWhat it covers: Binary/hex numbering, logic gates (AND, OR, NOT, NAND, NOR, XOR), flip-flops (basic concepts only), ARINC 429, MIL-STD-1553, RS-232/422/485, AFDX, CAN bus, Ethernet, fiber optic data links.
What to expect: Heavy on data bus protocols. "ARINC 429 uses what topology?" "What's the data rate of MIL-STD-1553?" "How many Remote Terminals can a 1553 bus support?" The logic gate questions are usually straightforward truth table or output prediction problems. The data bus questions require memorized facts about each protocol.
Study priority: CRITICAL — this is the highest-weighted category on the exam, and it's the biggest score opportunity. Mastering this section alone can make or break your pass.
This is where most candidates lose the most points. Data bus protocols are heavily tested and most study materials don't cover them well enough. Don't skip this.
Pro tip: For each bus protocol, know: data rate, topology (bus vs point-to-point vs star), word/message format, and typical aircraft applications. Make a comparison chart and memorize it. The table below is your starting point.
| Protocol | Data Rate | Topology | Wire Type | Typical Use |
|---|---|---|---|---|
| ARINC 429 | 12.5/100 Kbps | Point-to-point (1 TX, many RX) | Twisted pair | GA/commercial avionics |
| MIL-STD-1553 | 1 Mbps | Dual redundant bus | Twinax | Military aircraft |
| RS-232 | Up to 115 Kbps | Point-to-point | Single-ended | Legacy serial devices |
| RS-422 | Up to 10 Mbps | Point-to-point / multi-drop | Differential pair | Longer distance serial |
| RS-485 | Up to 10 Mbps | Multi-drop bus | Differential pair | Multi-device networks |
| AFDX | 100 Mbps | Switched Ethernet | Cat5 / fiber | Modern transport aircraft |
| CAN bus | Up to 1 Mbps | Multi-master bus | Twisted pair | Engine / systems data |
Category 5: Technical Documentation & Regulations
~7% · MEDIUMWhat it covers: FARs (Part 43, Part 91, Part 145), Advisory Circulars, STCs, PMAs, IPC, CMM, wiring diagram types (schematic, wiring, block), engineering orders.
What to expect: "Which FAR part governs repair station operations?" "What document provides part numbers for ordering?" "What's the difference between an STC and a PMA?" These are factual recall questions — you either know it or you don't.
Study priority: MEDIUM — not the heaviest section, but easy points if you study the right material.
Pro tip: Know WHAT each document type is FOR, not every detail in them. IPC = parts ordering. CMM = component overhaul procedures. AC 43.13 = acceptable methods, techniques, and practices. Part 43 = maintenance rules. Part 145 = repair station certification. That level of understanding is what they're testing.
Category 6: Wire & Harness Fabrication
~7% · MEDIUMWhat it covers: Wire types (Tefzel, Kapton, PTFE), wire gauges (AWG), crimp vs solder, connector types (D-sub, MIL-C-38999, Molex), shielding, wire marking, harness routing, breakout.
What to expect: Practical bench knowledge. "What crimping standard applies?" "What's the minimum bend radius for a wire bundle?" "Why is Kapton wire being replaced?" If you've built harnesses on the job, many of these questions will feel familiar.
Study priority: MEDIUM — a smaller category, but very practical and accessible for anyone with hands-on experience.
Pro tip: If you've built harnesses, this is easy. If not, focus on standards — MIL-T-22520 (crimping), wire identification methods, and connector pin numbering conventions. Know why crimp is preferred over solder in aircraft applications (vibration, reliability, inspectability).
Category 7: Safety & Human Factors
~5% · LOW-MEDIUMWhat it covers: ESD prevention, FOD prevention, LOTO procedures, chemical safety (MSDS/SDS), human error models (Dirty Dozen), fatigue management, shift turnover.
What to expect: Common-sense safety questions. "What should you do before working on a powered bus?" "What ESD precaution is most important when handling avionics LRUs?" These are mostly intuitive for experienced technicians, but the Dirty Dozen human factors list is a specific knowledge point you need to study.
Study priority: LOW-MEDIUM — quick to study, mostly intuitive for experienced techs. Don't spend a lot of time here, but don't ignore it either.
Pro tip: Learn the "Dirty Dozen" human factors: lack of communication, complacency, lack of knowledge, distraction, lack of teamwork, fatigue, lack of resources, pressure, lack of assertiveness, stress, lack of awareness, and norms. These come up on the exam, and they're easy to memorize.
Category 8: Aircraft Electrical Systems
~10% · HIGHWhat it covers: Aircraft power generation (generators, alternators), voltage regulators, battery systems, power distribution (buses, bus ties, contactors), circuit protection (breakers, fuses, current limiters), grounding/bonding, load analysis.
What to expect: System-level questions. "What happens when the main bus tie contactor opens?" "Which bus is powered during emergency operations?" "What's the purpose of a current limiter vs a circuit breaker?" This category connects your fundamentals knowledge to how real aircraft electrical systems work.
Study priority: HIGH — connects fundamentals to aircraft-specific applications. This is where your DC and AC knowledge becomes practical.
Pro tip: Understand electrical system architecture — normal, essential, and emergency buses. Know what loads are on which bus and what happens during a failure scenario. If you can trace power flow through an aircraft electrical system from generator to load, you're ready for this section.
Category 9: Communication Systems
~9% · MEDIUM-HIGHWhat it covers: VHF comm, HF comm, SATCOM, audio panels, intercom systems, ELT, CVR, antenna theory (basic), transmission line basics.
What to expect: System-level understanding. "What frequency range is VHF comm?" "How does a SATCOM system route voice calls?" "What's the purpose of an audio panel in the comm system?" The questions test whether you understand how these systems function and interconnect, not RF engineering theory.
Study priority: MEDIUM-HIGH — a solid chunk of the exam, and the systems are interconnected enough that studying one helps you with others.
Pro tip: Know frequency ranges (VHF: 118-136.975 MHz, HF: 2-30 MHz), basic antenna types (dipole, monopole, blade), and how audio integrates across comm, nav, and intercom systems. Don't get lost in deep RF theory — the exam stays at the technician level.
Category 11: Surveillance & Flight Instruments
~12% · HIGHWhat it covers: Transponders (Mode A/C/S), ADS-B (Out and In), TCAS/ACAS, EGPWS/TAWS, weather radar, pitot-static system, air data computers, EFIS, glass cockpit basics.
What to expect: Modern surveillance systems are heavily tested. "What does ADS-B Out broadcast?" "What's the difference between a TCAS RA and TA?" "What happens to the altimeter if the static port is blocked?" This category combines newer technology (ADS-B, EGPWS) with traditional instruments (pitot-static), so you need to know both.
Study priority: HIGH — the second highest-weighted category and a mix of modern and traditional systems.
Pro tip: ADS-B is a big focus. Know the difference between ADS-B Out (mandatory, broadcasts position/altitude/velocity) and ADS-B In (optional, receives traffic and weather data). Know the equipment types: 1090ES for aircraft above 18,000 ft (and all airlines), 978 UAT for below 18,000 ft. For pitot-static, know the classic failure modes — blocked pitot, blocked static — and what each does to the airspeed indicator, altimeter, and VSI.
Putting It All Together: Where to Focus
Here's every category ranked by estimated exam weight, with the study priority you should assign to each. If you're short on time, work from the top down.
- 1 Digital Electronics & Data Buses — 16% Critical
- 2 Surveillance & Flight Instruments — 12% High
- 3 DC Fundamentals — 10% High
- 4 Aircraft Electrical Systems — 10% High
- 5 Navigation Systems — 10% Med-High
- 6 Communication Systems — 9% Med-High
- 7 AC Fundamentals — 8% High
- 8 Technical Documentation & Regulations — 7% Medium
- 9 Wire & Harness Fabrication — 7% Medium
- 10 Solid-State Devices — 6% Medium
- 11 Safety & Human Factors — 5% Low-Med
If you're short on time: master the top 5 categories (58% of the exam), and you'll likely pass. But don't ignore the fundamentals — DC and AC knowledge underlies everything else. A weak foundation makes every systems question harder than it needs to be.
The candidates who pass on the first try aren't the ones who studied everything equally. They're the ones who spent the most time where the most points are. Digital data buses and surveillance systems alone account for 28% of your score. That's 28 questions. If you nail those two categories and hold your own on the fundamentals, you're in strong shape.