The recent articles about the new AC 66-08 Part 66 aircraft engineer licences have generated several more enquiries regarding licence coverage and certification for specific tasks.

In summary the enquiries were about:


  • Motor driven actuators in Mechanical ATA chapters
  • Radio checks
  • Radar checks

The radio and radar system checks had been raised with us previously and the questions basically came down to whether the serviceability tests fell within the definitions of a “simple test” under the Part 66 MOS and could be certified by a Category B1 LAME.

The motor driven actuator question came down to the classification of the component. Was it a mechanical component, an electrical sub-system, or was it an electrical sub-system of a mechanical system?

Although we had views on what the answers were, we consulted CASA for confirmation.


Motor Driven Actuators

In relation to the motor driven actuator- in this case the example was for a door but it could apply to many other areas. The advice received was that the actuator is a mechanical unit but has electrical parts which constitute “an electrical subsystem” for maintenance purposes.

Therefore, the removal and installation, and the adjustment is covered by Category B1. As a B1 with electrical exclusions has the privileges for simple twist or terminal connectors they are also permitted to certify for the maintenance with respect to removal/installation and adjustment.

A Category B2 and B1 LAME has coverage over any maintenance permitted by the Instructions for Continuing Airworthiness of the electrical subsystem of the actuator such as the microswitch, motor and plug . A Category B1 LAME with E1,4 and 5 exclusions does not have this privilege.

In most cases an actuator in a Mechanical ATA falls within the above classification. The excerpt of the specific advice from CASA is reproduced below.


Even if the information currently provided in the Part 66 MOS or the recently published AC66-08 does not appear to provide the clarity your member(s) seek with regards to determining whether an electrically driven actuator is considered to be a part of a mechanical system, or part or an electrical system, it’s very clear that the actual steps outlined in the task card for the removal/installation of the actuator (the question which has been raised here) is very much a category B1 task (it’s all mechanical in nature). Yes, the actuator may very well be electrically driven, but the actual installation of the actuator is mechanical and not the type of work you would expect a category B2 licence holder to perform.


CASA’s advice is a good guide as to how you should approach the task. If it is mechanical in nature, despite being motor driven treat it as mechanical.


Interpretation of test results

In relation to radio and radar operational checks either as a standalone task or following an Avionic LRU change. Prior to commencing a functional check in an Avionic system or replacing an Avionic LRU a B1 LAME must first determine whether the serviceability of the system/LRU can be established using simple tests. Simple tests are defined in the Part 66 MOS 66.5 Definitions, additionally, the AC66-08 introduces the 10 step limit for a simple test. Without reproducing the MOS the basic principles are that the test is done using the aircraft’s in-built systems and/or controls or with simple external test equipment AND the test result is a unique go/no indication or parameter.

A test that involves the LAME making an interpretation of the test outcome does not fit within the simple test criteria. A radio communications quality check (i.e. call to the tower) or an assessment of whether a display is showing a valid picture of local weather or local cloud conditions requires a level of interpretation of the results. These assessments are not a unique go/no go indication or parameter.

 An Avionics LRU that requires post installation testing that does not fit within the “simple test” definitions and guidance is not permitted to be replaced and certified by a B1 LAME. 


The AC 66-08 Appendix A part 2 provides additional guidance for avionic system maintenance.

If you have any further questions in relation to licence coverage feel free to email them in to

Stay Safe, Stay Compliant

Steve Re