B1 or B2? Choosing your Part 66 licence

B1 and B2 are not a beginner and an advanced licence — they are two different trades. B1 is the mechanical side: airframe, engines, and the electrical systems that go with them. B2 is avionics: the instruments, navigation, communication and autoflight systems, across every aircraft type. Neither is a step towards the other.

Most of the decision is about what you want to spend your working days doing. But the module paths diverge sharply too, so it is worth understanding both before committing two years of exams.

What each licence lets you certify

There is deliberate overlap at the boundary. A B1 licence includes privileges for electrical systems and for some avionics work that can be done by simple tests, which is why a B1 engineer is not helpless in front of a wiring fault. Where the line falls in practice is set by your organisation's maintenance data and procedures.

How the study paths differ

Both categories sit the same ten fundamentals, Modules 1 through 10 — although not always the same paper. Modules 4 and 5 are examined more deeply for B2, because electronics and digital techniques are the foundation of the avionics trade; Modules 6 and 7 are examined more deeply for B1, because materials and hands-on maintenance practice are the foundation of the mechanical one.

After Module 10 the paths separate completely.

The B1 back half

Three or four modules matched to the aircraft you will work on: Module 11 for aeroplanes or Module 12 for helicopters, a powerplant module — Module 15 for turbine or Module 16 for piston — and, on the aeroplane path, Module 17.

Module 11 is the big one. At 140 questions over 175 minutes for B1.1, it is the longest paper on the mechanical path and the one candidates most often under-estimate.

The B2 back half

Only two modules — but Module 13 is the single largest exam in the entire Part-66 system at 180 questions over 225 minutes, and some organisations split it across two sittings. Module 14 is small by comparison and covers engines from the instrumentation and control side rather than as machinery you would strip.

So B2 is fewer exams but more concentrated: one enormous paper carries most of the weight, where B1 spreads a similar total across several.

Questions worth asking before you choose

• Which work do you actually enjoy? The honest version of this question predicts more about finishing the licence than anything about job markets. Exams take years, and interest is what carries you through the third attempt at a module you dislike.
• What does your employer need? If you are already in a maintenance organisation, ask which category they are short of and whether they will support the training. Many will fund the path that solves their own rostering problem.
• Do you want to be tied to an aircraft type? B1 sub-categories bind you to aeroplane or helicopter, turbine or piston. B2 is a single category across all of them, which can mean more flexibility if you move between fleets.
• How comfortable are you with electronics? If Module 4 and Module 5 feel like the interesting part rather than the obstacle, that is a genuine signal for B2. Try the free questions in both and see which ones you want to keep answering.

Can you hold both?

Yes — plenty of engineers do, and a combined B1/B2 is valuable, particularly at smaller organisations where one person covers more ground. Because the fundamentals overlap, adding the second category later means sitting the modules unique to it plus any of the shared modules where the other category is examined at a higher level.

It is a serious undertaking rather than a formality, though. Most people qualify in one category, work in it for a few years, and add the second once they know the trade well enough to know they want it.