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EASA Part-66 Module 18 Cat B1.E only

Electric Power Plant EASA Part-66 — Module 18 Practice Questions

Module 18 is the newest module in the EASA Part-66 syllabus, created by Regulation (EU) 2025/111 for the B1.E subcategory alone. It covers electric machines, batteries, fuel cells, high-voltage distribution and engine control. Below: what is covered, the exam format, and seven sample questions in the same style you will meet on exam day.

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Every question comes with a worked, EASA-grounded explanation — understand why, don't just memorise.
400
Questions in bank
5
Syllabus sections
95 min
Exam time (B1/B2)
75 %
EASA pass mark

Syllabus at a glance

Full Module 18 syllabus
Section 18.1-18.2
Fundamentals and Performance
  • Principles of electric propulsion & thermal management
  • Power, torque, speed & efficiency relationships
  • Efficiency maps & operating envelopes
  • Effects of temperature, voltage & current on performance
Section 18.3
Engine Construction
  • PMSM, induction & switched reluctance machines
  • Stator, rotor, bearings, shafts & cooling arrangements
  • Insulation systems & protection classes
  • Inverter topologies, controllers & gearbox integration
Section 18.4.1-18.4.2
Batteries and Fuel Cells
  • Li-ion, LiPo & solid-state cells; cell, module & pack architecture
  • Battery management — state of charge, state of health, balancing
  • Thermal runaway, overcharge & deep-discharge hazards
  • Fuel cell principles, balance of plant & hydrogen storage
Section 18.4.3-18.4.4
Distribution and Control
  • High-voltage & low-voltage DC and AC architectures
  • Cables, connectors, shielding, contactors & circuit protection
  • Grounding, bonding, redundancy & fault-tolerant design
  • Control laws, sensor inputs & fault detection logic
Section 18.5-18.8
Indication, Installation and Operation
  • Power, torque, voltage, current & state-of-charge indications
  • Temperature monitoring; warning, caution & advisory alerts
  • Mounting, cooling, harness routing & EMC/EMI
  • Ground operation, storage & preservation

Three classic exam-day traps

Series count vs parallel count

In a pack written as 20P16S, the series count multiplies voltage and the parallel count multiplies capacity. Swap the two and both figures come out wrong at once — which is exactly the pair the distractors offer.

State of charge vs state of health

State of charge is how full the pack is right now; state of health is how much of its original capacity is left. A state of health of zero per cent means end of life, not a flat battery.

Inverter limits, not motor limits

The power electronics run out of thermal margin long before the machine does. Candidates check the motor temperature and stop there, when it is the controller that is already in its caution band.

What Module 18 covers — in plain English

Module 18 is the newest module in the EASA Part-66 syllabus. It was created by Commission Implementing Regulation (EU) 2025/111, which applies from 13 February 2026, and it exists for a single purpose: to support the new B1.E subcategory, covering aeroplanes with an electric power plant and a maximum take-off mass below 5 700 kg. No other licence category sits it — not A, not B1.1 to B1.4, not B2, not B2L and not B3. Where the rest of the syllabus mixes knowledge levels 1, 2 and 3 across its sections, every one of Module 18's eleven topics is set at level 3: detailed knowledge throughout, with no recognition-level sections to coast through. Combined with a 76-question paper, that makes it one of the longest and most demanding papers in Part-66.

The weight of the exam sits squarely on the electric energy system. Section 18.4 alone accounts for 38 of the 76 questions — half the paper — split between batteries and accessories (12), fuel cells and accessories (10), power distribution (10) and electronic engine control (6). Engine construction takes another 9, so machine types, stator and rotor construction, insulation classes and inverter topologies are worth studying properly rather than skimming. Much of this material has no counterpart anywhere else in Part-66: cell, module and pack architecture; battery management functions such as state of charge and state of health; thermal runaway and its containment; proton-exchange and solid-oxide fuel cells; and high-voltage DC distribution, where Paschen's law, partial discharge and altitude derating replace the familiar low-voltage thinking of Module 3. The remaining sections — indication, installation, ground operation, storage and preservation — are smaller, but they are examined at the same level 3 depth.

Because Module 18 belongs to one subcategory, the route into it is unusual. Under Appendix IV, Table B, a holder of a B1.1 or B1.2 licence extending to B1.E needs to pass Module 18 and nothing else. A separate transitional arrangement in Article 5(8) of Regulation (EU) No 1321/2014 allows an electric aeroplane below 5 700 kg to be endorsed on a B1.1 or B1.2 licence until 13 February 2028, subject to conditions, so the two routes run side by side for now. Candidates arriving from the gas turbine or piston engine modules should expect a different style of question: far less thermodynamics, far more electrochemistry, power electronics and protection logic. The full topic list and the questions-per-topic breakdown are on our Module 18 syllabus page.

These samples are drawn from our live Module 18 question bank of 400 questions. The full timed practice quiz draws 76 questions per attempt, scored against the official EASA 75 % pass mark, with weak-area tracking across attempts.

7 free sample questions

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Q1 Fundamentals - Shaft Power

An electric engine gives 200 Nm at 2350 rpm. What shaft power is that?

  1. A About 4.9 kW
  2. B About 49 kW
  3. C About 470 kW
Reveal answer + explanation Hide answer
Correct answer: B — About 49 kW
Shaft power is torque times angular velocity, and angular velocity in radians per second is the speed in revolutions per minute times two pi over sixty, so 200 Nm at 2350 rpm gives about 49 kW. A result ten times smaller is a decimal slip, and multiplying torque by the speed in revolutions per minute leaves out the conversion and inflates the answer roughly tenfold.
Q2 Engine Construction - Machine Types

A switched reluctance machine is stripped for inspection. What does its rotor carry?

  1. A Wound copper coils
  2. B Bonded surface magnets
  3. C Toothed iron poles
Reveal answer + explanation Hide answer
Correct answer: C — Toothed iron poles
A switched reluctance rotor is plain laminated iron with salient teeth and carries no excitation, no magnet and no cage, which is why it is mechanically rugged and generates little heat. Copper coils sit only on the stator of this machine type. Surface magnets belong to a permanent magnet rotor, where the field comes from the magnets rather than from reluctance.
Q3 Batteries - Pack Architecture

A module holds cells of 3.6 V and 3 Ah in a 20P16S arrangement. What are its nominal voltage and capacity?

  1. A 57.6 V and 60 Ah
  2. B 57.6 V and 48 Ah
  3. C 72.0 V and 48 Ah
Reveal answer + explanation Hide answer
Correct answer: A — 57.6 V and 60 Ah
Series count multiplies voltage and parallel count multiplies capacity, so sixteen cells in series give 16 x 3.6 V and twenty groups in parallel give 20 x 3 Ah. Reading the capacity from the series count gives 48 Ah, and reading the voltage from the parallel count gives 72 V; both swap the two roles of the arrangement.
Q4 Fuel Cells - Electrodes

Hydrogen supplied to a fuel cell goes to which electrode, and what is its polarity?

  1. A Cathode, positive
  2. B Anode, negative
  3. C Anode, positive
Reveal answer + explanation Hide answer
Correct answer: B — Anode, negative
DOE describes a fuel cell as two electrodes sandwiched around an electrolyte: a negative electrode, the anode, and a positive electrode, the cathode. Fuel such as hydrogen is fed to the anode and air to the cathode, where oxygen combines with the protons and electrons. The cathode is the positive, air-fed electrode, and the anode is the negative one.
Q5 Distribution - HV Architecture

An aircraft power system is redesigned to run at a higher transmission voltage for the same power. Which benefit follows directly?

  1. A Simpler and cheaper connectors
  2. B Smaller and lighter conductors
  3. C Thinner and lighter insulation
Reveal answer + explanation Hide answer
Correct answer: B — Smaller and lighter conductors
Power is the product of voltage and current, so a higher transmission voltage lowers the current needed for the same power, which allows smaller and lighter conductors and reduces resistive losses. It works the other way for insulation and terminations: a review reported operational voltages limited to 540 V by common insulation and termination practice at flight altitudes.
Q6 Engine Control - Motor Controllers

A motor controller uses sensorless field-oriented control. Which quantity does it still have to measure?

  1. A Rotor position
  2. B Shaft torque
  3. C Phase current
Reveal answer + explanation Hide answer
Correct answer: C — Phase current
Sensorless means there is no position encoder: rotor angle and speed are estimated, but the phase currents are still measured and form the only feedback path, so the quality of that measurement decides stability and performance. Rotor position is the quantity the observer computes rather than reads, and shaft torque is inferred from current.
Q7 Indication - Temperature Limits

On the Velis Electro, the motor reads 95 degC and the controller 68 degC. Which unit is in its caution range?

  1. A The power controller
  2. B The electric motor
  3. C The motor and controller
Reveal answer + explanation Hide answer
Correct answer: A — The power controller
The approved EPSI570C markings put the power controller caution band at 65 to 69 degC with a red line at 70 degC, and the motor caution band at 100 to 109 degC with a red line at 110 degC. At 68 degC the controller is in caution, while 95 degC is still inside the motor green band, which shows how much lower the power electronics limits are.
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Module 18 — frequently asked questions

How many questions are in the EASA Part-66 Module 18 exam?
The Module 18 paper is 76 multiple-choice questions, with no essay section. AMC1 to Appendix II sets the split by topic: Fundamentals 7, Engine performance 5, Engine construction 9, Batteries and accessories 12, Fuel cells and accessories 10, Power distribution systems 10, Electronic engine control 6, Engine indication systems 5, Power plant installation 4, Engine monitoring and ground operation 5, and Engine storage and preservation 3. Only B1.E candidates sit the paper, so there is no shorter Category A version of it.
What is the pass mark for EASA Part-66 Module 18?
The pass mark is 75%, the same threshold as every other EASA Part-66 module. On a 76-question paper that means at least 57 correct answers. Each question has three options with a single correct answer and there is no negative marking, so an attempted question always beats a blank one.
How long is the Module 18 exam?
B1.E candidates get 95 minutes for the 76 questions, which works out at 75 seconds per question — the standard Part-66 allowance. The paper is long rather than rushed, but because every topic is examined at knowledge level 3 the stems tend to describe a situation rather than ask for a definition, so the reading time per question is higher than in the shorter modules.
Which EASA licence categories require Module 18?
Module 18 is sat by subcategory B1.E only — aeroplanes with an electric power plant and a maximum take-off mass below 5 700 kg. Every other category is marked not applicable for this module in Part-66 Appendix I: Category A, B1.1 to B1.4, B2, B2L and B3 candidates do not sit it. Under Appendix IV, Table B, an existing B1.1 or B1.2 licence holder extending to B1.E needs to pass Module 18 and nothing else.
What does Module 18 cover, and what do students find hardest?
Module 18 covers fundamentals of electric propulsion, engine performance and construction, the electric energy system (batteries, fuel cells, power distribution and electronic engine control), engine indication systems, power plant installation, ground operation and monitoring, and storage and preservation. The electric energy system carries 38 of the 76 questions, so that is where most of the difficulty sits. Three traps recur: the series count of a pack sets voltage while the parallel count sets capacity, and swapping them gets both figures wrong; state of charge and state of health measure different things, and a state of health of zero per cent means end of life rather than a flat battery; and the power electronics reach their thermal limits well before the machine does, so the controller can be in its caution band while the motor is still in the green.
How should I revise for EASA Part-66 Module 18?
Start with the electric energy system, because it is half the paper: cell, module and pack architecture, battery management functions and protections, charging modes, thermal runaway and its containment, fuel cell types and the balance of plant, and high-voltage DC distribution with its contactors, isolation monitoring and altitude derating. Give engine construction a proper pass as well — permanent magnet, induction and switched reluctance machines each behave differently, and inverter topologies come up regularly. Because every topic is examined at knowledge level 3, recognition is not enough: practise explaining why a system behaves the way it does, not just naming its parts. Module 18 is a new module, so drill against exam-style questions rather than relying on general electrical knowledge from Module 3.
Can I practise in a language other than English?

Yes. Every quiz question, all of its answer options and the written explanation can be read in 13 languages besides English — Chinese (Traditional), French, German, Greek, Hindi, Italian, Norwegian, Polish, Portuguese, Romanian, Russian, Spanish and Turkish. It is included for every signed-in member at no extra cost, and you can switch language in the middle of a quiz without losing your answers or your timer.

The English original stays one click away on every question, which is the point: the EASA Part-66 examination is sat in English, so you can read a question in your own language, answer it, then switch it back to English to check yourself against the wording you will actually meet.

Two caveats worth knowing. It is machine translation — checked so that no two answer options drift into meaning the same thing and that numerals and units survive intact, but it is not a human technical translation. And technical designations such as A320, LEAP-1A, Part-145, CS-25 and ATA chapter numbers are deliberately left in English, because those are the strings on the aircraft, in the manual and on the exam paper. Translation covers the quizzes; the study notes and reference pages are in English.

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Other EASA Part-66 modules

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1. Mathematics
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2. Physics
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3. Electrical fundamentals
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4. Electronic fundamentals
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5. Digital techniques / Electronic instrument systems
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6. Materials & hardware
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7. Maintenance practices
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8. Basic aerodynamics
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9. Human factors
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10. Aviation legislation
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11. Aeroplane aerodynamics, structures and systems
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12. Helicopter aerodynamics, structures and systems
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13. Aircraft aerodynamics, structures and systems
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14. Propulsion
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15. Gas turbine engine
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16. Piston engine
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17. Propeller

Module 18 study resources

Module 18 detailed syllabus
Per Commission Regulation (EU) 2023/989
Module 18 study notes
Topic-by-topic explanations
Q&A Forum
Ask about tricky Module 18 questions
EASA licence categories
A · B1 · B2 · B2L · B3 overview

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