Part-66 Module 3: Electrical Fundamentals

Electricity from first principles, in twenty topics, and the first three rows are about charge and about words rather than circuits. Topic 3.1, electron theory, opens at level 1 with the structure of the atom and what makes one material a conductor and another an insulator. Static electricity and conduction follows at level 2, and it’s more practical than the name suggests: an aeroplane collects charge in flight and sheds it through the static wicks on its trailing edges, and a bowser gets bonded to the airframe before a fuel cap comes off. Electrical terminology at 3.3 then settles what the words mean, potential difference, electromotive force, current and resistance, before the systems papers start using them without introduction.

The DC half does most of the arithmetic. Generation of electricity sits at 3.4 and its sources at 3.5, which in practice means the battery, the ground power unit and the bus everything arrives on, while DC circuits at 3.6 is where Ohm’s law, series and parallel networks and voltage drop begin earning their place. The circuit on an aeroplane isn’t the circuit in the textbook, though. Most metal aeroplanes are wired with a single conductor and use the airframe itself as the return path, which is why a corroded earth stud shows up as a dim landing light rather than a dead one, and why the return is worth checking before you condemn a component.

Resistance and power take the next three rows, and they’re the practical heart of the DC material. Topic 3.7(a) is resistance itself, and the UK’s wording of it, “Resistance/resistor: resistance and affecting factors”, names what varies: length, the area of the cross section, the material and the temperature. Topic 3.7(b) covers the resistors as components and sits at level 1, while power at 3.8 turns all of it into heat and watts, which is where cable sizing and breaker ratings come from. Capacitance at 3.9 brings in the first component that stores energy in a field instead of losing it as heat.

At topic 3.13 the module changes gear, and the quantities stop sitting still. AC theory is followed by resistive, capacitive and inductive circuits at 3.14, transformers at 3.15, filters at 3.16, and AC generators and AC motors at 3.17 and 3.18. A large aeroplane makes most of its power as alternating current at 400 Hz rather than at the frequency of a domestic socket, and it does that for weight: the faster the field alternates, the smaller a transformer or a motor can be. Reactance is the idea to get straight here, because once current and voltage stop being in step, an intuition built on DC gives confident wrong answers.

None of this gets taught as aeroplane systems, and that’s deliberate: Module 3 stops at the machine on the bench and the circuit on the page. The installed article, with a bus bar behind it and a control unit deciding when it comes on line, is electrical power at topic 11.6, which both authorities set at level 3, and that paper assumes this one and never repeats it.

52 questions, 65 minutes, and not a single dash in Module 3’s B1.1 column of the EASA text, so nothing in the module is excused for this category. A paper of that size has room to ask about every row of the table, the four rows the EASA text keeps at level 1 included. So this is one of the few syllabuses in the set you can read straight through as a list of things you’ll be asked about, with no part of it set aside for somebody else’s licence.

The 75% pass mark lands on 39 correct answers here, leaving 13 in hand, and that allowance doesn’t travel: each of the thirteen papers carries its own 75%, with no aggregate across the set and no averaging of a poor afternoon against a good one. A comfortable Module 1 or Module 2 counts for nothing on the day you sit this one, and a difficult Module 3 takes nothing back from the modules you’ve already banked. Every result stands as its own verdict.

Nothing in the EASA column for Module 3 reaches level 3, and the assimilated text on legislation.gov.uk, as we read it, matches that row for row: the same twenty codes, in the same order, at the same depth. Three rows carry a mark below, and what’s marked is wording rather than depth: they are 3.5, 3.7(a) and 3.7(b), all in the DC half, where the UK CAA has lifted part of the regulation’s descriptor up into the heading. Read the level column before the titles. It’s almost flat, and a flat column means the real question is which rows you haven’t met yet, never which of them goes deepest.

No, and this is one of the cleanest agreements in the whole set. Both authorities call it Module 3 with no letter suffix, which deserves a second look on a UK table that still carries 7A, 9A, 11A and 17A from the text Great Britain froze at the end of 2020. Judge it by the codes and the two tables are a single table: 3.1 through to 3.18 in an unbroken sequence, with nothing numbered by either authority that the other numbers differently, no code carrying two different subjects, and, as we read the UK text, the same level against every row in both columns above. Add 52 questions in 65 minutes on both sides and Module 3 sits with the nine, and in the smaller group inside that whose syllabus holds up as well. Modules 2, 5, 7, 11 and 15 match on the question count and part company somewhere underneath it.

The only difference anywhere in the table is in how three titles are written, and all three sit in the DC half. At 3.5, EASA writes “Sources of DC electricity” and the UK writes “DC sources of electricity”, which is the same four words in a different order and nothing more. At 3.7(a), EASA has “Resistance/resistor: resistance” against the UK’s “Resistance/resistor: resistance and affecting factors”, and at 3.7(b) it has “Resistance/resistor: resistors” against “Resistance/resistor: construction and temperature coefficient”.

A title in Appendix I is a heading rather than the syllabus itself, and the regulation carries a fuller descriptor underneath each one. We haven’t set the two regimes’ descriptors side by side, so we won’t tell you they say the same thing. The two 3.7 rows are the pair to look at, because the UK headings there read as instructions rather than labels. “Affecting factors” turns a noun into a job: go and find out what changes a conductor’s resistance, and “construction and temperature coefficient” puts how a resistor is built, and how it drifts as it warms up, inside a row whose EASA title stops at “resistors”.

The wider split between the two authorities is on the EASA versus UK CAA page: mutual recognition, which licence to go for, and what happened to the conversion route.

This page covers one of the 13 papers. The rest of the guide covers the route they sit inside: what the exam is, what else you must have done besides passing it, and how the two authorities differ.

Both authorities require the same thirteen subjects. Only the numbering and some of the titles differ, and the UK still uses the A suffix on four of them where EASA has dropped it. Each has a page of its own.