Part-66 Module 6: Materials and Hardware

Two halves, joined in the middle by corrosion. The first half is materials, and it starts with the ferrous metals. The two authorities word that opening row differently: EASA calls it “alloy steels used in aircraft”, the UK calls it “characteristics, identification, heat treatment”. Either way the question underneath is the same: why a landing gear leg is forged from a high tensile steel when a control rod isn’t, what carbon content and alloying elements do to what a steel will bear, and what annealing, normalising, hardening and tempering each leave behind. Testing of ferrous materials drops to level 1, so hardness, tensile and impact testing are things you describe rather than carry out.

The metals without iron take the next block of rows, and on a B1.1 airframe they are most of the aeroplane: aluminium alloys and what cladding, solution treatment and artificial ageing do to them, titanium where heat and strength meet in a pylon, magnesium in a gearbox casing, and copper alloys in bushes and terminals. EASA then adds a row the UK hasn’t got, “repair and inspection procedures”, twice over, once for each family of metals, which reads as the current EASA text treating repair as a subject of its own rather than something you pick up in Module 7.

Composites and the other materials that aren’t metal come next, and these days carry the weight the metals used to, so the syllabus wants the character of a laminate: fibre and resin doing different jobs, and a honeycomb core carrying shear between two thin skins. Then it wants the detection of defects, where disbond, delamination, water soaked into a core and impact damage that leaves almost no mark on the surface all live, along with the tap testing that finds them. The UK adds repair to that row’s title, calling it “detection of defects and repair”, and it names “sealants and bonding agents” in the characteristics row above. Wooden structures and fabric covering follow, still in a syllabus written for turbine aeroplanes: solid and laminated timber, the glues and the dope, and inspecting a covered surface for rot and for slack.

The hardware half never asks you to work anything out, because every row of it, from screw threads through to electrical cables and connectors, is a choice between parts that somebody else designed and wrote down. That’s why the whole of it sits at level 2, and why you learn it by what each part is chosen for rather than by what it is. Grip length is the clearest case: a bolt is the right bolt when the plain shank, not the thread, lies across the shear plane, so the question is never how long the bolt is but which part of it carries the load. A castellated nut with a split pin through it is positively locked and a friction nut isn’t, which settles the choice on any joint that turns in service. Edge distance on a blind rivet is the same reasoning, this time about how close to the edge of a sheet you can put a load before the sheet tears out instead of the rivet failing.

On the EASA paper you get 80 questions in 100 minutes; on the UK CAA’s you get 72 in 90. What separates the two is ground rather than standard: the EASA table carries repair and inspection rows for the metals that the UK text has no counterpart for, and the longer list goes with the longer paper. So the first piece of work on this module is settling which paper you’re booked on, because that decides how much of the table above is yours and how much is somebody else’s problem.

You pass the EASA paper with 60 correct answers and can drop 20, while the UK paper takes 54, with 18 to drop, and the 75% behind both is the same. Don’t read the bigger of those two allowances as the bigger concession. Both authorities take the same proportion, so the extra answers an EASA candidate can lose come attached to the extra rows an EASA candidate has to know, and the two margins buy the same comfort. Only the EASA paper is long enough to be sat as two complementary halves under Appendix II point 1.12, and the assimilated UK text makes no provision of the sort.

What makes this module heavy is the shape of the list, not the length of the paper. The fasteners take a run of rows to themselves, screw threads through to rivets; pipes and unions take another; and bearings, springs, transmissions and control cables sit together in a third. That grouping is the one kindness in it, because you can revise the table block by block instead of row by row, and every block you finish is a visible piece of the exam put away.

EASA gives repair and inspection a row of its own three times over, once for each family of metals and once for composites, while the UK table has none of the three, keeping what it wants on repair inside the composite defect row. Those are absences, not rewordings, so a revision list built from the wrong column will either miss a subject or prepare one that isn’t on your paper. The other pair is wooden structures and fabric covering, where the UK column sits a level above the EASA one on our reading of the assimilated text. Wherever the two texts word a title differently, the UK CAA’s own version is printed underneath the EASA one.

Yes: Module 6 is the first paper in the set where they part company, one of the four papers out of thirteen where the two authorities set exams of different lengths, 80 questions in 100 minutes under EASA against 72 in 90 under the UK CAA. The name is the part that matches: both call it Module 6, both title it Materials and Hardware, and neither hangs a letter on it the way the UK still does with 7A and 9A.

The syllabus beneath the paper is where the difference has substance: EASA lists 24 topics and the UK 21, and the missing ones all point the same way. EASA asks separately about repair and inspection procedures for each family of metals and for composites, while the UK has no repair row for either kind of metal and folds its composite repair content into 6.3.1(b), whose title reads “detection of defects and repair”. So an EASA candidate meets repair as a subject here, and a UK candidate meets repair methods under 7.18(b) in Module 7A instead.

The levels disagree in one place, and it looks like a period piece: EASA sets wooden structures and fabric covering at level 1, and our reading of the assimilated UK text puts both a level higher, which would ask a UK candidate for the same depth on a doped fabric surface as on a bonded composite panel, on a licence for turbine aeroplanes. Chronology explains it better than policy does: the UK text is the copy of Part-66 that stopped moving at the end of 2020, and EASA has rewritten Appendix I twice since.

A few titles are worded differently, and these are the ones worth knowing about: both metals rows put heat treatment into the UK heading where EASA writes “alloy steels used in aircraft” and “characteristics”. The composite characteristics row gains “sealants and bonding agents”. Hardest to read past is 6.4(b), the module’s only level 3, which EASA titles “types of corrosion” and the UK titles “types, identification and causes”.

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.