About the exam
CAA Part-66 Exam structure
An independent, route-aware study guide for the current UK Part-66 aircraft maintenance licence categories, Appendix I and Appendix VII basic-knowledge modules, and Appendix II and Appendix VIII examination standards.
Issuer and path
UK CAA Part-66 Aircraft Maintenance Licence Study Guide is administered through UK Civil Aviation Authority. Check official resources before booking, retesting, or relying on a stale requirement.
UK Part-66 Aircraft Maintenance Licence Basic Knowledge
0 scored + 0 pretest
The route-specific Appendix I and Appendix VII basic-knowledge modules and examination standards for current UK Part-66 licence categories and subcategories.
Before booking a module
Confirm the licence route, module variant and whether an MCQ or essay component is needed; then use the CAA portal or approved Part-147 organisation's current instructions for the actual date, venue, identification and permitted materials.
How to use this guide
How to prepare for UK Part-66 basic-knowledge examinations
Fix the intended A, B1, B2, B2L, B3, L or C route; use the regulatory module matrix and knowledge levels; then rehearse the exact MCQ and essay components that apply to each selected module.
1. Identify licence scope
Start from the aircraft group, propulsion type, intended certification privilege and applicable category or subcategory.
2. Read the matrix cell
Select Appendix I or VII and record the exact module subjects and knowledge levels for that route.
3. Apply maintenance reasoning
Connect theory to hazards, inspection evidence, approved data, system interaction and release-to-service decisions.
4. Match the paper standard
Retrieve the exact Appendix II or VIII MCQ count, time, essay requirement and re-sit rule before timed practice.
Categories, Subcategories and Scope
Selecting among A1-A4, B1.1-B1.4, B2, B2L, B3, L1C-L5 and C before applying a module matrix or experience route.
Key rules
Rule 1
Category A covers limited authorised line-maintenance tasks, while B1 is the mechanical route divided by aeroplane or helicopter and turbine or piston powerplant.
Exam cue: Choose aircraft class, powerplant and intended certification privilege before choosing modules.
Rule 2
B2 covers avionics on all aircraft; B2L excludes Group 1 aircraft and is built from one or more system ratings; B3 is limited to piston-engine non-pressurised aeroplanes at or below 2,000 kg MTOM.
Exam cue: For B2L, identify the exact system ratings rather than treating it as a smaller universal B2.
Rule 3
Category L covers defined light-aircraft, sailplane, balloon and airship subcategories, while Category C is the base-maintenance certification category for aeroplanes and helicopters.
Exam cue: Separate basic licence category, aircraft rating, organisation authorisation and task competence.
Common traps
Using B1.1 and B1.3 interchangeably because both involve turbine engines.
Prevention: Do not mix Category A, B1, B2/B2L, B3 or Category L module variants, or treat the aggregate 601-item study allocation as an official CAA examination total.
Assuming B2L applies to Group 1 aircraft.
Prevention: Do not mix Category A, B1, B2/B2L, B3 or Category L module variants, or treat the aggregate 601-item study allocation as an official CAA examination total.
Treating an unendorsed basic category as authority to certify every aircraft type.
Prevention: Do not mix Category A, B1, B2/B2L, B3 or Category L module variants, or treat the aggregate 601-item study allocation as an official CAA examination total.
Memory anchors
A
Limited authorised line maintenance and simple defect rectification personally performed.
B1
Mechanical route divided by aircraft kind and turbine or piston powerplant.
B2 / B2L
B2 is the full avionics route; B2L is non-Group-1 and system-rating limited.
B3 / L
B3 covers defined light piston aeroplanes; L covers specified light-aircraft and lighter-than-air subcategories.
C
Category C supports release following base maintenance on aeroplanes and helicopters.
Next best moves
Quick check-up
Use a short quiz to confirm the rule pattern is actually sticking.
Check-up Questions
Which Part-66 subcategory applies to turbine aeroplanes on the Category A route?
A mechanic wants the B1 route for piston helicopters. Which subcategory matches?
Answer all questions to submit.
Next step personalized recommendations
Open another topic next
Official resources
Verify the details with the official sources
Use these links for eligibility, scheduling, handbook rules, and issuer updates. Our guide helps you study; official sources tell you what the testing partner currently requires.
UK Part-66 licence categories and subcategories
Current A, B1, B2, B2L, B3, L and C category definitions, including B2L system ratings and Category L subcategories.
66.A.25 basic-knowledge requirements
Applicable Appendix, approved examination bodies and the 10-year basic-training and examination window.
Appendix I basic-knowledge requirements
Knowledge-level definitions and the detailed Modules 1-17 matrix for Categories A, B1, B2, B2L, B3 and C.
Appendix II basic-examination standard
MCQ and essay construction, pass and re-sit rules, plus route-specific question counts and examination times.
Appendix VII Category L knowledge requirements
Modules 1L-12L, knowledge levels and the L1C-L5 subcategory module matrix.
Appendix VIII Category L examination standard
Category L MCQ format, pass and attempt rules, and exact module question counts and times.
CAA engineer knowledge requirements
CAA overview of basic knowledge, examination credits, essay requirements and the 10-year application window.
CAA aircraft-maintenance licence examinations
Current CAA e-examination booking, identification, permitted materials, results and credit guidance.
CAA Part-66 application guidance
Application routes, experience evidence, examination acceptance, Category C pathways and licence validity.
CAA aircraft-maintenance exam timetable
Current session pattern and reminder that the booking portal controls actual availability.
FAQ
Common CAA Part-66 questions
Is this an official CAA course or examination question bank?
No. This is an independent study guide with original practice questions, not official or recalled CAA examination content. Basic examinations must be passed through an appropriately approved UK Part-147 maintenance training organisation or the CAA, as applicable.
Why does one slug cover so many Part-66 routes?
The tracker defines one caa-part-66 slug. These assets preserve that granularity while keeping the actual routes explicit: A1-A4, B1.1-B1.4, B2, B2L, B3, nine Category L subcategories and Category C. The route matrix must be selected before the module list or paper format is used.
What do knowledge levels 1, 2 and 3 mean?
Appendix I scales the required depth from familiarity with principal elements at Level 1, through general theoretical and practical knowledge at Level 2, to detailed theoretical and practical knowledge with integrated application at Level 3. The level is set per subject cell and licence route, not once for an entire module.
Does Category A take Module 4 Electronic Fundamentals?
No separate Category A Module 4 paper is specified in Appendix II, and Appendix I shows no Category A knowledge-level requirement for its Module 4 subjects. Category A route arrays in this guide therefore omit Module 4.
How do B2 and B2L differ?
B2 applies to all aircraft and uses the full Module 13 plus Module 14. B2L excludes Group 1 aircraft and is built from at least one of five system ratings. Its Module 13 paper combines a basic block with the selected rating block, and Module 14 is required only for the Instruments and Airframe Systems ratings.
What is the Category B3 scope?
B3 is for piston-engine non-pressurised aeroplanes of 2,000 kg maximum take-off mass and below. Its knowledge route uses the B3-specific Modules 7B, 9B, 11C and 17B rather than the corresponding A/B1/B2 variants.
How does Category L differ from the standard route?
Category L uses its own Appendix VII syllabus, Modules 1L-12L, and Appendix VIII examination standard. Papers are multiple-choice only. The exact modules depend on whether the aircraft is a sailplane, powered sailplane or ELA1 aeroplane, balloon, ELA2 airship, or larger gas airship.
Does Category C have separate basic-knowledge examinations?
No. For basic knowledge, a Category C applicant must meet either the B1 or B2 knowledge levels. The application pathway and experience evidence still depend on the applicant's route, so Category C should not be treated as a stand-alone paper set.
What happens after a failed Part-66 module?
Appendix II normally requires 90 days before re-sitting a failed module, reduced to 30 days after an approved retraining course tailored to the failed subjects. It permits three consecutive attempts, then requires a one-year wait before another set. Category L Appendix VIII uses its own rule of no more than three attempts in a rolling 12-month period.
Can an MCQ pass be retained if the essay part is failed?
Yes. Appendix II treats module parts separately for re-examination: only the failed part is retaken. Each required essay is allowed 20 minutes, and Modules 7A, 7B, 9A, 9B and 10 are the essay-bearing variants.
How should I use the published paper counts?
Use the count and time only after selecting the route and module variant. For example, Module 5 differs between A, turbine and piston B1 branches, B2/B2L and B3; full B2 Module 13 may be split into two examinations; B2L instead uses basic and rating blocks.