The short answer
B1 is the mechanical maintenance licence category; B2 is the avionics maintenance licence category. B1 has four subcategories based on aircraft and engine type. B2 covers avionics and electrical systems across aircraft types, subject to the licence’s scope and applicable ratings. Choose the privileges your work requires, then plan the training.
The difference between B1.1, B1.2, B1.3, B1.4 and B2
| Category | Aircraft or system focus | Sigma training |
|---|---|---|
| B1.1 | Turbine-engine aeroplanes | B1.1 course |
| B1.2 | Piston-engine aeroplanes | B1.2 course |
| B1.3 | Turbine-engine helicopters | B1.3 course |
| B1.4 | Piston-engine helicopters | B1.4 course |
| B2 | Avionics and electrical systems | Fixed-wing training or rotary-wing training |
B1 includes airframe, powerplant, mechanical and electrical maintenance. B2 is not simply “B1 with more electronics”; it addresses a different technical scope. Both can involve electrical work, so do not use the labels alone to decide whether a particular task is within your privileges.
Source: CASA Part 66 licence categories. Checked 31 October 2026.
The B2 fixed-wing and rotary-wing labels in Sigma’s catalogue identify training streams. They do not create two separate B2 categories on a CASA licence.
A category is only part of the certification picture
Before planning training for a job, read the current licence itself: category or subcategory, exclusions, limitations and aircraft ratings. Then consider the maintenance organisation’s authorisation requirements. A category licence does not give unrestricted authority to certify every aircraft or every maintenance task.
CASA explains how these requirements interact for engineers working in a Part 145 organisation. Use that guidance with your organisation’s procedures when deciding what authority a role needs.
New category
Your job needs a different technical scope.
An existing B1 engineer moving into B2 work needs the additional category requirements assessed. Experience in one field can support recognition, but does not establish all competence in the other.
Existing category
A specific privilege is missing.
You may need exclusion removal, an aircraft rating or another defined training outcome. Identify the restriction first so you enrol in the product that addresses it.
Can I add B2 to B1, or another B1 subcategory?
Yes, a licence can be extended when the relevant requirements are met. The useful question is what your current training and maintenance experience already cover for the new category. CASA requires the necessary theory and practical experience for an additional category or subcategory; the detail depends on the starting and target scopes.
- Name the destination
For example, B1.1 to B2, or B1.3 to B1.1. Include the aircraft and work your employer wants covered.
- Supply the starting evidence
Provide your current licence, completed units, examination records and relevant maintenance history.
- Plan the gap
Assess credit, identify remaining competence and exams, and arrange the practical exposure needed for the target.
- Complete and apply
Finish the required training and experience, then use the applicable CASA application process.
Read CASA’s instructions for adding a category or subcategory. Avoid treating an overseas regulator’s module list as an Australian training plan; use the CASA requirements and your assessed background.
Engineers training engineers
Build the capability your operation needs next.
An employer may need broader cover across its fleet or systems. Sigma can connect the engineer’s current experience with a practical training plan for the next outcome.
Do I need another diploma?
That depends on the result you want and the units already held. A qualification outcome and a licence-category outcome need to be specified separately. Start with our diploma and licence pathway guide, then choose the relevant category package for assessment of the remaining scope.
For a smaller set of systems, compare modular licensing. For a restriction already printed on your licence, use the exclusion course finder. For a particular aircraft, review maintenance type training. These are different training decisions.
Questions we hear from engineers
Which licence is better: B1 or B2?
Neither is a universal upgrade over the other. The right choice depends on the work, aircraft, available practical experience and the privileges your role needs.
Can I get both B1 and B2?
You can work towards both when you meet the requirements for each. Ask for an assessment of your starting evidence and the additional scope, rather than assuming one complete category automatically covers the other.
Your next step
Choose your next category and start the application.
Open the category course that matches your target. If several exclusions or another category are part of the plan, describe that in the application so we can assess the combined scope.
Reviewed 31 October 2026. Course details and regulatory requirements can change. Use the linked course information and current regulator guidance when planning your pathway.
