EASA Part-66 Module 5: Digital Techniques / Electronic Instrument Systems

seventeen topics, and they arrive in a deliberate order: the module opens with electronic instrument systems, the row that names what a glass flight deck is made of. That’s a survey row at level 1 in EASA’s table, though EASA’s guidance still gives it 4 questions, and the UK CAA sets it at level 2. Then it goes underneath, to numbering systems, because the machine works in binary and the fault codes it hands you are usually written in hexadecimal; to data conversion, because the world outside is a continuously varying voltage from a thermocouple or a synchro while the world inside is a string of ones and zeros; and to data buses at level 2, which on the EASA table is the first real step up in depth.

Logic and computing are each cut in half, and each time the half that goes is the one inside the chip. Logic circuits split into identification and applications at level 2, interpretation of logic diagrams at no level at all; basic computer structure divides the same way, terminology and technology at level 2, computer operation left blank. You’re expected to recognise an AND gate, know what a NAND gate is used for, and follow the vocabulary of buses, memory and word length, but not to trace a ladder of gates through a diagram or explain how a processor runs its instructions. Microprocessors, integrated circuits and multiplexing come next, and the B1 column asks for none of them.

Fibre optics sits at level 1, worth 3 questions, and earns its place on newer types, where a bundle of glass has replaced a loom of copper on the busiest data paths, because it shrugs off the magnetic field around a generator feeder and carries far more for far less weight. Level 1 means familiarity rather than fluency, so in practice that’s knowing why an end face gets cleaned and capped, why a cable has a minimum bend radius, and why a fibre run isn’t something you splice on a wet stand. Electronic displays sit at level 2 immediately after, and that’s the row that explains the flight deck you’ll stand in.

Some of the level 2 rows near the end are maintenance practice filed under an electronic name: electrostatic sensitive devices covers the wrist strap, the bonded mat, the conductive bag, and the card that passes every test on the bench and dies in service six months later. Software management control treats a software load as a part: it has a number, it has a version, it can be the wrong one, and a load nobody recorded is a configuration nobody can account for. Electromagnetic environment is electromagnetic compatibility, interference, HIRF and lightning, and it’s the reason bonding leads, shield terminations and loom separation are drawn the way they are.

The module closes with typical electronic/digital aircraft systems, the row that puts everything before it back on an aeroplane and looks at real installations. EASA’s guidance lists them: the datalink that files a fault to the ground before anybody has opened a door, fly by wire, the flight management and inertial reference systems, the electronic flight instruments and the engine and warning displays, satellite navigation, collision avoidance, integrated modular avionics, and the cabin and information systems, each with the built in test equipment behind it. It sits at level 1, and it carries 5 questions, more than any other row in the module.

EASA gives category B1 40 multiple choice questions across 50 minutes, with no essay, for a module whose title carries a slash through the middle: digital techniques on one side, electronic instrument systems on the other. One paper examines both, the questions don’t arrive labelled, and a stem about a display and a stem about the bus feeding it belong to the same afternoon, where they may well sit next to each other. Reading the module as two subjects is fair enough while you revise, and useless the moment the paper is in front of you.

EASA’s acceptable means of compliance spread the 40 more evenly than the levels suggest. The level 1 rows, electronic instrument systems, numbering systems, data conversion, fibre optics and the typical aircraft systems, carry nearly half the paper between them, and 5.15 on its own carries 5, the most of any row, while the blank rows carry none. EASA calls those numbers acceptable rather than fixed, so they describe the shape of the paper rather than any one sitting.

Clearing 75% takes 30 right answers and leaves 10 to spend, and the awkward thing about that allowance here is that it can go anywhere without announcing itself. Software management control and the electromagnetic environment read like administration beside logic circuits and data conversion, yet the EASA text puts them at the same depth as data buses and electronic displays. Marks lost one answer at a time, across rows the syllabus treats as equals, leave nothing for you to point at afterwards: a margin spent that way looks exactly like bad luck, and it tells you nothing about where to go next.

What the module gives back is that some of its questions can be worked out rather than remembered, since a hexadecimal value converted the long way round, a gate named from its symbol and a truth table filled in line by line are all answers you can reach with nothing in front of you but the stem. The condition is that you treat an unfamiliar question as a piece of work rather than a loss, and give it the minutes it wants instead of moving past it.

The two authorities use the same codes for every row here, and the same heading wherever the UK prints one, so this is a table to read down rather than across. Reading down, the dashes come first: they mark the rows category B1.1 is never asked about, and they’re the reason a syllabus of seventeen rows is a good deal smaller than it looks. Then come the level 2 rows, which are the whole of the depth EASA asks for, and the question counts against every required row, which hold the surprise: the level 1 rows carry nearly as many questions as the level 2 ones. The rows marked in the table are the two, 5.1 and 5.15, where the UK CAA sets a different level; the five blanks carry a dot in place of a level, and the section below the table explains the difference.

Barely, and where it does it runs in one direction. Take the codes and the titles first and there’s nothing to mark up at all: not a number, not a heading, not a word inside a heading, which is more than can be said for most of this licence. The UK CAA’s paper agrees as well, 40 questions, 50 minutes, no essay and no letter on the module number, so Module 5 belongs with the nine papers the authorities agree on rather than the four they set differently, and the whole of the difference sits in two cells of the level column.

The syllabus isn’t quite identical, though, and the distinction is worth holding on to, because an identical paper is no guarantee of an identical syllabus, and Module 5 is the module that proves it. At topic 5.1, electronic instrument systems, EASA sets level 1 and the UK CAA level 2, and at 5.15, typical electronic/digital aircraft systems, the same thing happens again. Those are the first and last rows of the module, and they’re the two that describe real installations rather than the theory sitting underneath them.

So the UK’s version of Module 5 leans a little more towards the aircraft at both ends. Level 2 asks you to understand the theory, read schematics and apply the knowledge using detailed procedures, where level 1 asks for familiarity and a plain description. That means a UK candidate is expected to work with a display system or a datalink installation where an EASA candidate is expected to recognise one. Everything between those two rows is set identically, so a candidate under either authority can revise from the other’s list with more confidence here than this licence usually allows.

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.

EASA requires thirteen modules for category B1.1, and the UK CAA examines the same thirteen subjects. The UK CAA syllabus differs in nine of them, and the UK still adds an A to four module numbers where EASA dropped it, so its number follows the EASA one here, as in 7/7A. Each module has a page of its own, with the EASA paper first and the UK CAA differences marked.