Which Part-66 Module Is the Hardest? What the Syllabus Shows

The hardest Part-66 module is usually the biggest one for your category: Module 11A for B1.1, with 140 questions, and Module 13 for B2, with 188 questions under EASA rules. No authority publishes pass rates, so "hardest" can't be settled with data. What can be compared is what each module asks of you: paper size, knowledge level, essays and calculations. The Part-66 modules guide lists all 17 modules; this post ranks them by those four measures.

Part-66 Prep is an independent study aid. The figures below come from the exam standard (Appendix II) and the syllabus (Appendix I), as built into our papers.

What makes a Part-66 module hard?

A Part-66 module is hard when it combines a long paper, a deep knowledge level, an essay or a lot of calculation. Each one raises the difficulty in a different way.

1. Paper size. At 75 seconds a question, a 140-question paper runs for 175 minutes. Stamina and concentration become part of the test.
2. Knowledge level. Level 3 items need detailed knowledge and links between systems, not just definitions. Our post on Part-66 knowledge levels explains the three levels.
3. Essays. Essays are marked on key points at 75%, separately from the multiple choice. Under EASA rules only Module 7 has essays; under UK CAA rules Modules 7, 9 and 10 do.
4. Calculations. Numerical questions punish procedural slips, because the wrong options are built from them (a wrong unit conversion, a sign error).
5. A short margin. On a 20-question paper, the 75% pass mark leaves room for only five wrong answers.

The Part-66 exam format guide covers the rules behind each of these.

The hardest Part-66 modules for B1.1

For a B1.1 candidate, Module 11A is the hardest on every measure except calculation. The table scores each B1.1 paper on the four measures, using EASA sizes with the UK figure where it differs.

B1.1 module	Questions (EASA / UK)	Level 3 items	Essays (EASA / UK)	Calculation load
11A Turbine aeroplane	140 / 140	32	0 / 0	Low
15 Gas turbine engine	92 / 92	1	0 / 0	Medium (thrust and performance)
7 Maintenance practices	80 / 80	5	2 / 2	Medium (weight and balance)
6 Materials and hardware	80 / 72	1	0 / 0	Low
3 Electrical fundamentals	52 / 52	0	0 / 0	High
2 Physics	52 / 52	0	0 / 0	High
10 Aviation legislation	44 / 40	1	0 / 1	Low
5 Digital techniques	40 / 40	0	0 / 0	Medium (number conversions)
1 Mathematics	32 / 32	0	0 / 0	High
9 Human factors	28 / 20	0	0 / 1	Low
8 Basic aerodynamics	24 / 20	0	0 / 0	Medium
4 Electronic fundamentals	20 / 20	0	0 / 0	Medium

Calculation load is our judgement from the syllabus content, not an official rating. The size and level columns are the regulation's.

Key fact: Module 11A is also our largest B1.1 question bank, at 1,509 questions. Long papers need more practice papers, not just more reading. The Part-66 Module 11 questions guide breaks the paper down by sub-module.

The hardest Part-66 modules for B2

For a B2 candidate, Module 13 is the hardest by a wide margin. It is the largest paper in the whole Part-66 system and carries 24 level 3 items.

B2 module	Questions (EASA / UK)	Level 3 items	Why it is hard
13 Aircraft systems	188 / 180	24	Size; autoflight, communication, navigation and surveillance at level 3
5 Digital techniques	72 / 72	0	B2-only topics: microprocessors, multiplexing, logic diagrams
7 Maintenance practices	60 / 60	5	Essays under both systems
3 Electrical fundamentals	52 / 52	0	AC theory and calculations
4 Electronic fundamentals	40 / 40	0	Twice the B1 paper; servomechanisms and transistors at level 2
14 Propulsion	32 / 24	0	Short paper on engines a B2 rarely works on

The Part-66 Module 13 questions guide explains the B2L version, which is examined per system rating instead of as one paper.

Why do Modules 7 and 10 feel so hard?

Modules 7 and 10 feel hard because they test things experience doesn't teach in the right form: essays and law. They are also the two modules with the most searches in our keyword research, which suggests how many candidates worry about them.

• Module 7 combines one of the largest B1 papers (80 questions) with two 20-minute essays under both systems. Experienced mechanics often lose marks by answering the way their hangar does a task rather than the way the syllabus describes it. See the Part-66 Module 7 questions guide.
• Module 10 is a memory test of rules, organisations and numbers, and the EASA and UK versions now differ in content. UK candidates also write an essay. See the Part-66 Module 10 questions guide.

The Part-66 essay questions guide covers how essays are marked in Modules 7, 9 and 10.

The calculation modules: 1, 2 and 3

Modules 1, 2 and 3 are hard for a different reason: they are maths and physics without the tools you use at work. Calculator rules vary between exam centres, so prepare to work by hand. The Part-66 Module 3 questions and Part-66 Module 1 questions guides show the formulas that come up most.

Is Part-66 hard?

Part-66 is demanding but passable: for a B1 or B2 it is a series of 12 or 13 module exams at a 75% pass mark, not one very difficult exam. What makes it hard is the volume and the attempt rules, not any single question.

Rule	EASA	UK CAA
Pass mark	75%	75%
Wait after a fail	90 days (30 after tailored retraining)	90 days (30 after tailored retraining)
Attempt limit	3 in any 12 months	3 consecutive, then a 1-year wait

Each failed attempt costs at least three months on that module, which is why the hardest modules deserve the most preparation. The EASA Part-66 FAQs and the CAA's engineer licensing pages set out the rules for each system.

How to plan around the hardest modules

Plan the hardest modules for when you have the most time and the most relevant experience. Neither EASA nor the CAA sets a module order, so you choose.

1. Start with a foundation module you can pass, such as Module 1 or 8, to learn the exam format.
2. Take Modules 2 and 3 early, because later modules build on them.
3. Leave Module 11A (B1.1) or Module 13 (B2) until you have hangar exposure to the systems, and give it the longest run-in.
4. Space the essay modules apart so you can practise essays properly for each.
5. Book only when you are ready. Our rule is 85% on three different full papers; Part-66 mock exams explains how to sit and review them.

Module 15 for B1.1 sits between these: it is big, but it pairs well with Module 11A. The Part-66 Module 15 questions guide shows how.

Next step

Find your own hardest module rather than relying on averages: the free B1.1 diagnostic or B2 diagnostic samples every module for your category. Then sit a full free paper for your biggest module, such as Module 11A paper 1 for B1.1 or Module 13 paper 1 for B2. Papers 2 to 10 and sub-module drills for every module are in Pro.