EASA Part-66 Module 11: Aeroplane Aerodynamics, Structures and Systems

The whole aeroplane, in three unequal parts. Aerodynamics comes first and is the smallest: how the aeroplane flies, how the flight controls change what it is doing, and then the other aerodynamic devices, the vortex generators, stall wedges and wing fences, the small hardware bolted to a wing to make the airflow behave. Structures follow, and everything after that is systems, which are most of the module and the reason EASA’s list runs to 56 topics and reads less like a syllabus than an inventory. The references from here on are EASA’s; the UK divides the same aeroplane into 33 topics under numbers of its own, and the regimes section below has the differences.

The bracketed numbers running down the table were not invented by the regulation. They are ATA chapters, the numbering the industry files its technical documentation under, and they are the same numbers on the aeroplane’s maintenance manual, its wiring diagrams, its task cards and its defect entries: 21 is air conditioning, 24 electrical power, 26 fire protection, 27 flight controls, 28 fuel, 29 hydraulic power, 30 ice and rain protection, 32 landing gear, 36 pneumatics, 38 water and waste. Module 11 is the only one of the thirteen papers written in that order, so learning it is learning where things live. A job card headed 32 is landing gear, and you know that before you have ever opened a manual in anger.

Structures are treated as construction rather than repair, so 11.2 asks what an airframe is made to withstand and how it is put together, and 11.3 walks the aeroplane part by part: fuselage, doors and windows, wings, stabilisers, flight control surfaces, nacelles and pylons. Airworthiness requirements for structural strength gets a row of its own, which in practice means the fail safe, safe life and damage tolerance thinking behind why a structure may crack and keep flying, and why an inspection interval is the interval it is. Airborne towing devices get a row too, at level 1.

The systems run is the long middle of the module, and the level column stays at 3 through nearly all of it, with hydraulic power the place where that bites hardest. A green system that won’t hold pressure is a question about a pump, a reservoir, an accumulator and a transfer unit all at once, and the schematic is the only thing that tells you which of them the symptom is pointing at. Air conditioning makes the same demand from the other end, because the air has been tapped off an engine compressor, cooled through a pack and mixed before an outflow valve decides the cabin differential, so a complaint about cabin temperature can start almost anywhere along that chain. The rest of the run is asked at the same depth, and the syllabus even lists corrosion under water and waste, which anyone who has lifted a floor panel under a galley will call the right decision.

The far end of the table holds the newest entries, and they are the clearest sign this syllabus has been rewritten for aeroplanes built this century. “On-board maintenance systems” (ATA 45) puts a central computer between you and the fault, so the skill being examined is reading the messages it has collected rather than chasing them round the aeroplane with a meter. “Integrated modular avionics” (ATA 42) took apart the old design of one box for each job and put shared processing in a cabinet instead, which is why the syllabus asks for the overall theory and then for typical layouts. Cabin and information systems bring the entertainment, the network and the electronic library into a module that once stopped at the galley. All of these sit at level 2, one step below the level 3 carried by the run of systems above them.

The EASA paper is 140 questions long, with 175 minutes to answer them, and the UK CAA’s is the same: the largest examination either authority sets for this category. Length buys width rather than depth: a paper this size can put a question on far more of the table than a short one can reach, while asking each question in the form every other module asks its own. Nothing about the size changes what one question can do, only how much of the aeroplane gets visited before the paper runs out.

Here 75% comes to 105 answers right, with 35 allowed to be wrong, and in absolute terms that is the widest allowance in the set. Facing it are 56 topics under the EASA table, every one it requires for category B1.1 feeding the paper, and 33 under the UK CAA’s. This is the module where a gap costs differently from a slip: a system you never got round to, oxygen say, or water and waste, doesn’t cost you a question here and there. It costs you whatever the paper drew from it, and although EASA’s guidance sets an acceptable spread, from a single question on the smallest rows to 5 on the avionics line, a paper may depart from it with justification, so no system is promised and none can be safely written off.

Under EASA, and only under EASA, a paper this long may be taken as two complementary parts of similar allowed time, both sat within the same organisation and each passed in its own right. The UK’s assimilated text is older than that provision, so its Module 11A is one sitting, and that is a long time in one chair. Whichever authority you sit under, the shape of the day matters more here than on any other module in the set, so have a plan for the paper before you walk in, not halfway down it.

The EASA table comes first and carries the question count on every required row, and the depth in both tables isn’t spread about. It gathers: between 11.4 and 11.17, from air conditioning through to water and waste, the level barely comes off 3 at all, and on either side of that stretch it thins away, with the aerodynamics and structures rows a level below it and the avionics line lower still. Nothing in the reference column warns you, because the numbering climbs at a steady rate whatever the depth beside it is doing. Where the two authorities differ in what they actually ask, rather than only in how they number it, the section after this one has the list.

Not in the paper: the UK CAA’s is 140 questions, 175 minutes and no essay, like EASA’s, and that is where the agreement ends, because this is the module the two texts have drifted furthest apart on. EASA calls it Module 11. The UK CAA calls it Module 11A, Turbine Aeroplane Aerodynamics, Structures and Systems, and the difference isn’t cosmetic: the UK still divides the aeroplane module by powerplant and keeps the lettered module names that EASA abolished under Regulation (EU) 2023/989 in favour of a single table with a column for each category.

Numbering splits next, which is why the syllabus above needs two tables. EASA divides theory of flight into 11.1(a) and (b), where the UK folds both into 11.1.1 and adds 11.1.2, High Speed Flight, which EASA examines in Module 8; EASA cuts air conditioning into 11.4(a) to 11.4(e) where the UK cuts the same ground into 11.4.1 to 11.4.4, in a different order. The trap is 11.2(b), one code carrying a different subject under each authority: “airworthiness requirements for structural strength” under EASA, and “construction methods” under the UK CAA, which EASA numbers 11.2(c).

Two content differences change what you revise, and high speed flight is the larger: the UK’s Module 8 has no high speed topic, so the material sits here instead, as 11.1.2, “High Speed Flight”, and a UK candidate meets Mach number, compressibility and shock waves in this paper where an EASA candidate met them at 8.4. The rest is smaller: EASA’s fuel row cites ATA 28 and ATA 47 where the UK’s cites ATA 28 alone.

The knowledge levels split too, and the renumbering hides half of it. The visible case is “portable fire extinguisher” at 11.8(b), the only code both texts number alike and then set at different depths: level 1 under EASA and level 2 under the UK CAA, familiarity under one, and under the other a general knowledge of the theory and practice with the ability to apply it. The buried case is “air supply”, which EASA sets at level 3 as 11.4(b) and the UK CAA at level 2 as 11.4.1, where nothing in the reference tells you it is the same subject. EASA’s text moved here most recently too: Regulation (EU) 2025/111 replaced this module’s title row and rows 11.8 and 11.10, so an older printed copy of Appendix I will not match the table above.

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.