The Part-66 B2L Licence and Its System Ratings

The Part-66 B2L licence is the least understood category in the system. People search "what is B2L" because it rarely appears in job adverts for airlines, and because it works differently from every other category: instead of one fixed set of modules, you build the licence from system ratings. This guide explains what a B2L engineer may certify, how the five system ratings work, which modules and papers each rating needs under EASA and UK CAA rules, how much experience you need, and how B2L compares with the full B2 licence.

Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. For how B2L sits among the other categories, see the Part-66 licence categories hub.

What the Part-66 B2L licence covers

The category is defined in 66.A.3 of Part-66: the B2L licence applies to all aircraft other than those in Group 1, and is divided into system ratings. A B2L licence must contain at least one rating. The wording is the same in the EU text in the EASA Easy Access Rules for Continuing Airworthiness and in the retained UK text on legislation.gov.uk.

Group 1 (66.A.5) is complex motor-powered aircraft, multi-engine helicopters, aeroplanes certified to operate above FL290, fly-by-wire aircraft, gas airships other than ELA2 and any other type the authority says needs a type rating. So a B2L engineer works on Group 2 aircraft (single turboprops, single-turbine and single-piston helicopters, and some lower-complexity types the authority places there), Group 3 piston aeroplanes and Group 4 sailplanes, balloons and airships. That is general aviation, flying schools, light business aircraft and helicopter operators, not airliners.

Privileges in plain English

Under 66.A.20, a B2L licence lets you issue certificates of release to service and act as B2L support staff for:

• maintenance on electrical systems
• maintenance on avionic systems, within the system ratings endorsed on your licence
• if you hold the airframe systems rating, electrical and avionic tasks within power plant and mechanical systems that need only simple tests to prove serviceability

As with every category, you also need a certification authorisation from the maintenance organisation you work for, and the recency rule in 66.A.20(b): six months of relevant maintenance experience in the previous two years.

The five B2L system ratings

System rating	Module 13 content	Module 14 needed?
Com/nav	13.4(a) communication and navigation	No
Instruments	13.8 instruments	Yes
Autoflight	13.3 and 13.7 autoflight and flight controls	No
Surveillance	13.4(b) surveillance (transponders, collision avoidance and similar)	No
Airframe systems	13.11 onwards (air conditioning, fire protection, fuel, hydraulics, ice and rain, landing gear, oxygen and similar systems)	Yes

Everyone also sits a Module 13 basic paper covering theory of flight, structures, electrical power and lights (13.1, 13.2, 13.5 and 13.9). Most B2L engineers start with the ratings that match the work they already do, often com/nav and instruments in an avionics shop, and add others later. Each added rating needs its Module 13 paper (and Module 14 if it is instruments or airframe systems, unless you have already passed it) plus three months of experience on that rating.

B2L modules and paper sizes: EASA and UK CAA

Modules 1 to 10

B2L sits the same Modules 1 to 10 papers as B2, at the same knowledge levels. Under UK rules Modules 7, 9 and 10 have essays; under EASA rules only Module 7 does.

Module	EASA questions	UK CAA questions
1 Mathematics	32	32
2 Physics	52	52
3 Electrical fundamentals	52	52
4 Electronic fundamentals	40	40
5 Digital techniques	72	72
6 Materials and hardware	60	60
7 Maintenance practices	60 + 2 essays	60 + 2 essays
8 Basic aerodynamics	24	20
9 Human factors	28	20 + 1 essay
10 Aviation legislation	44	40 + 1 essay
Total, Modules 1 to 10	464 + 2 essays	448 + 4 essays

Module 13 by system rating

This is where B2L differs from B2. The real exam splits Module 13 into rating papers. Sizes come from Appendix II: the EU version as replaced by Regulation (EU) 2023/989 and the retained UK version.

Module 13 paper (B2L)	EASA questions / time	UK CAA questions / time
Basic (13.1, 13.2, 13.5, 13.9)	32 / 40 min	28 / 35 min
Com/nav	24 / 30 min	24 / 30 min
Instruments	20 / 25 min	20 / 25 min
Autoflight	28 / 35 min	28 / 35 min
Surveillance	20 / 25 min	8 / 10 min
Airframe systems	52 / 65 min	32 / 40 min
Full B2 Module 13, for comparison	188 / 235 min	180 / 225 min

The UK airframe systems paper is much shorter because it draws on sub-modules 13.11 to 13.18, while the EU paper covers 13.11 to 13.19.

Module 14

Module 14 propulsion is needed only for the instruments and airframe systems ratings: 32 questions under EASA rules, 24 under UK rules.

Worked examples of a full B2L module set

Ratings chosen	EASA total questions	UK CAA total questions
Com/nav only	464 + 32 + 24 = 520	448 + 28 + 24 = 500
Instruments only	464 + 32 + 20 + 32 (M14) = 548	448 + 28 + 20 + 24 (M14) = 520
All five ratings	464 + 176 + 32 (M14) = 672	448 + 140 + 24 (M14) = 612

For comparison, the full B2 licence is 684 questions under EASA rules and 652 under UK rules. Even with every rating, B2L is a little shorter, mainly because the rating papers add up to less than the full Module 13.

Key fact: On Part-66 Prep, the B2L Module 13 paper uses the full B2 Module 13 size (188 questions under EASA rules, 180 under UK rules), because it covers every rating at once. Per-rating Module 13 papers are not built yet. If you are sitting one rating paper, drill the Module 13 sub-modules for that rating.

B2L experience requirements

Basic experience is set by 66.A.30. It must be practical maintenance experience on operating aircraft and must cover the system ratings you apply for.

Route	EASA	UK CAA
No relevant technical training	3 years	3 years
Skilled worker in a technical trade	2 years	2 years in the rule, but the CAA recognises no qualifying course
Part-147 approved basic course	1 year	1 year
Each system rating added later	3 months relevant experience	3 months relevant experience

The CAA's application page states that the skilled worker reduction is not available because no course is currently recognised. As with every category, at least one year of the experience should be recent, and exams and experience must fall within the 10 years before you apply. The experience requirements guide covers logbooks and evidence.

Compare that with B2: 5 years without training, or 2 years after a Part-147 course. For someone already working on light aircraft avionics, the shorter experience is the main attraction of B2L.

Aircraft ratings on a B2L licence

The system ratings decide which systems you may certify. Aircraft ratings, under 66.A.45, decide which aircraft. B2L holders do not get individual type ratings, because Group 1 aircraft are outside the category. Instead:

• Group 2: a manufacturer subgroup rating or a full subgroup rating (2a, 2b or 2c), based on demonstrated practical experience relevant to the subgroup and to your system ratings
• Group 3: the full Group 3 rating, based on practical experience
• Group 4: the full Group 4 rating, based on practical experience

A B2L holder endorsed with full subgroup 2a or 2b is entitled to Groups 3 and 4 as well, and full subgroup 2b also brings 2c. The type ratings guide explains groups and ratings in more depth.

B2L vs B2: which should you aim for?

	B2L	B2
Aircraft	All except Group 1	All aircraft
Systems	Only the endorsed system ratings	All avionic and electrical systems
Module 13	Basic paper plus one paper per rating	One full paper (188 EASA / 180 UK)
Module 14	Only for instruments and airframe systems	Always
Experience, no training	3 years	5 years
Experience, Part-147 course	1 year	2 years
Typical employers	General aviation, flying schools, light helicopter operators, avionics shops	Airlines, large MROs, business jet operators, plus everything B2L covers

If you want to work on airliners or business jets, aim for the B2 licence. If your work is light aircraft avionics and you want a licence sooner, B2L is the faster route, and it is not a dead end. Under 66.B.110, the authority will replace a B2L with a B2 carrying the same aircraft ratings once you have passed exams on the difference in basic knowledge and gained the experience set out in Appendix IV, which is 12 months from B2L to B2, reduced by half after a relevant Part-147 course. The difference exams typically cover the Module 13 content you have not yet passed, and Module 14 if you do not hold it; your authority confirms exactly what is needed.

The B1 vs B2 licence guide covers the mechanical versus avionics decision if you are still choosing between those.

Where B2L engineers work and how long it takes

B2L fits organisations that maintain aircraft outside Group 1: general aviation maintenance organisations, flying schools with piston and single-turboprop fleets, operators of single-engine helicopters, and avionics workshops that install and maintain radios, transponders, navigation equipment and glass cockpit displays in light aircraft. Many of these organisations hold Part-145 or Part-CAO approvals, and the certification authorisation they give you sets the scope you actually use day to day.

How long the licence takes depends on the route. The experience minimum is one year after a Part-147 basic course or three years without one, and the exams usually run in parallel with that experience. Nobody publishes an official figure for how long the modules take to pass, and it varies with how many hours a week you can study and whether you sit at a Part-147 organisation or at a CAA exam venue. Plan it module by module, and remember that every pass stays valid for a licence application for 10 years. The licence application guide explains what to send once you meet both requirements.

How to prepare for B2L exams

The B2L route uses the same Modules 1 to 10 as B2, so most of your study is shared with B2 candidates. The usual order is Modules 1, 2 and 3 first, then the short Modules 8, 9 and 10, then 4, 5, 6 and 7, and finally the Module 13 rating papers and Module 14. Module 5 (72 questions) and Module 7 (with essays) are the two big papers before you reach the aircraft systems.

On Part-66 Prep, every B2L paper is sized to the B2L figures under EASA or UK CAA rules, chosen on the start screen. The free B2L practice hub lists every module, and the free B2L diagnostic gives you 20 questions across the category's modules to see where to start. For Module 13, start with Module 13 paper 1 for B2L, keeping in mind it is the full B2 size. The free licence categories note summarises privileges, modules and experience for every category.

Your study plan

1. Choose your first system ratings based on the work you do now, and confirm with your employer which ratings they need.
2. Take the free B2L diagnostic to find your weak modules.
3. Work through Modules 1 to 10 using the free paper 1 and quick practice for each module in the B2L hub.
4. For Module 13, focus on the basic sub-modules and the sub-modules for your ratings, then sit full papers.
5. Add Module 14 if you chose instruments or airframe systems.
6. When you need papers 2 to 10, sub-module drills and all study notes for every module, see Pro. Book each exam when you score 85% or more on three different papers.