Aircraft Maintenance Certification – Certifying Staff, License Categories and Internal Authorizations

Some time ago, after I have sent my first newsletter to all the subscribers (thank you all for signing up!), I have received an email from one of my readers, Mr. Adam Jenkins, asking whether I could write something about the license and internal approval requirements needed to release various types of aircraft maintenance. In particular, we engaged into an email conversation about the certification (maintenance release) of aircraft components. Nevertheless, I thought it may prove useful to write a short article about certification privileges in general. This matter seems a bit confusing to many people, and rightfully so as the regulations don’t spoil us with clarity. Thank you, Adam, for the inspiration!

Who can Work on an Aircraft and is a License Always Required?

Let’s start with the basic concept of who and when can perform maintenance on an aircraft or component. A common misconception is that in order to be allowed anywhere near an aircraft, one requires a Part-66 license. This is not correct.

Virtually anyone, after being hired by an approved Part 145 maintenance organization and after having undergone appropriate training, can be allowed to perform a set of maintenance tasks. In more formal terms “allowed” means that a person may obtain an internal company authorization allowing him or her to do specific jobs.

What needs to be stressed out, however, is that there is a big difference between actually doing a maintenance task (for example cleaning the wheel well from dirt and corrosion protective compound before an inspection) and certifying that this given task has been completed and, as EASA puts it, with respect to that task the aircraft is ready for release to service.

The latter – which is referred to as maintenance certification or maintenance release – can only be done by a person holding an appropriate EASA Part-66 license. And if this was not enough, a company internal authorization is still required, as the license alone does not constitute sufficient proof that the license holder has received sufficient recurring training and has been involved in a proper amount of maintenance activities in the last period (at present, at least six months of actual work in each 2 year period is considered a minimum) nor that he or she is adhering to Part 145 procedures while performing the work.

So, to keep a long story short: you don’t need a license to work an aircraft, but someone with a license will need to certify that what you did was correct and complete.

Certifying Staff in Line Maintenance

For line maintenance tasks, we can distinguish a total of four types of personnel engaged in the actual work. Those would be mechanics (sometimes referred to as fitters – generally people with no license, but with an internal company approval), category A certifying staff and category B certifying staff. But wait – didn’t I say four? That’s because the B certifying staff can actually be divided into B1 and B2, which is mechanical and avionics certifying staff, respectively.

Some may argue that there are more B categories, divided into aircraft, helicopters and small aircraft. True, of course. To make it simple, I just assume for now that an aircraft is an aircraft and for a given type we only have a B1 and a B2 person.

I have already described what line maintenance is and also pointed out the differences between line maintenance and base maintenance. For the purpose of this article, it’s enough to state that line maintenance would be carried out on the apron, with no need for a hangar, and would consist mainly of simple, regular maintenance tasks as well as the evaluation and rectification of minor defects. Please also keep in mind that the CRS (certificate of release to service) for line maintenance is typically located in the TLB (technical log book) of the aircraft and is not much more than a signature on the appropriate page, with specific tasks listed in the TLB as well.

In line maintenance a mechanic can perform whatever work the company has authorized him or her to do. This would, typically be preceded with appropriate on the job training and be limited only to a specific set of tasks. It is not all too common for unlicensed personnel to be present during line maintenance, because the nature of line maintenance often does not require more than just one person. And since a mechanic requires additional certifying staff to release the work, it would not be too economical to have that arrangement.

People with a category A license are allowed to certify certain maintenance tasks as per the internal company approval issued by the Part 145 aircraft maintenance organization. The Part 145 regulation lists typical tasks which type A certifying staff can normally certify. This would include things like wheel replacements, replacements of bulbs, filling up oil and hydraulic fluid, and several other things. An A rated person would normally not certify for defect rectification tasks, and particularly not for defect evaluation (like a new dent on the fuselage). An A rated person may also be permitted to release an aircraft after a daily check, for example. It is important that an A licensed person may only certify the work that they did themselves – they cannot certify work physically performed by unlicensed personnel or even their A licensed colleagues.

A category B license allows its holder to be authorized for a full release of the aircraft during line maintenance. This means that category B certifying staff, after obtaining the proper internal authorization from the Part 145 company, has sufficient skill and knowledge to deal with anything that may come up during such maintenance. In particular, apart from regular line maintenance tasks, such persons may perform defect rectification and evaluation and decide, whether a given defect may be rectified in a line maintenance environment or not. They also have the right to defer maintenance items and use the MEL (minimum equipment list) although only in agreement with the CAMO of the operator. B license staff can also supervise the certify the work carried out by other people, particularly mechanics and A licensed personnel performing tasks outside of their authorization scope.

Certifying Staff in Base Maintenance

Base maintenance checks are always complex projects which require the management of large teams of people. Therefore, the final CRS for base maintenance needs to be signed by a C licensed person (of course, that person also requires and internal company authorization). Interestingly enough, the C license holder does not to have mechanical skills – there is a so-called “academic path” to obtaining a C license, which allows university or college graduates become category C certifying staff without having actually worked on the aircraft. Why this actually makes sense, I will explain a bit later.

The physical work during a base maintenance check requires a lot of tedious, and not overly complex, tasks. It is necessary to remove seats, internal panels, galleys, lavatories, external panels, clean the aircraft for inspection purposes, and last but not least – put everything back together at the end of the check. This work can be (and often is) performed by mechanics. They have no Part-66 license, but they have been trained on the job and obtained a company approval to do certain tasks.

The work performed by the mechanics is overseen by category B support staff. Category B support staff, in most cases, also perform work on the aircraft. However, they will not work alone and may have separate teams of mechanics working on different tasks at the same time. It is the responsibility of the category B personnel to sign off for each individual task and take responsibility for the correct accomplishment of such task. Those people are free to decide with what level of trust they approach the mechanics and to what extend they want to interfere and physically check the work that they perform. This is important, because a majority of single tasks may be too complex for one person to complete, and yet there needs to be one person managing it. Category B support staff certifies each task by signing the appropriate task card. This serves as proof that this particular task has been carried out in accordance with all the applicable standards.

Now we can go back to the category C certifying staff. This is the person who signs the final CRS after the check. A typical heavy structural check may consist of several boxes full of signed task cards. It is the duty of the C license holder to ensure that every task has been completed, that every card has been correctly signed and that the overall work package contains all the required documents (release certificates for components, NDT reports, etc.). Only then can he or she sign the CRS. This is why it is not necessary for a C license holder to have practical experience on the aircraft – in a heavy maintenance environment they will never touch the aircraft, as they will have more than enough to do just by going through all the paperwork.

When talking about base maintenance we cannot forget so called “specialized services”. A great example is always NDT (non-destructive testing), although tasks such as composite repairs or metal work would also fit into that category. People performing such work normally do not hold EASA Part-66 licenses. This doesn’t mean that they are not licensed – NDT staff in particular has to undergo very strict training and adhere to several international norms which are way too broad to be described here. But from the Part-66 perspective, they remain unlicensed. Based on internal company procedures, they receive approvals to perform a specific set of tasks (for example ultrasonic or eddy current inspections, borescope inspections, etc.). After performing such a task, specialized staff is allowed to sign for that particular task only, and such a sign off is not a release to service of such task. The final release to service of the task can only be made by category B support staff, and then later included in the work pack certified by category C certifying staff. So, the specialized personnel only takes accountability for the specialized process, like a thickness measurement or thermography results.

Certifying Aircraft Component Maintenance

I already touched a bit upon component maintenance in a previous article. However, it makes sense to review it again, as it is part of an overall aircraft back to service release.

There are no EASA regulations for people meant to certify shop maintenance (the maintenance of components). Part 145 will send you to Part-66, but there is no information in Part-66 either. The overall regulations stated that component certify staff should adhere to national regulations. If you’re lucky enough and your CAA has them, you can get the procedure directly the CAA.

In most cases, the authorities expect that a Part 145 workshop will include in their MOE (Maintenance Organization Exposition) procedures on how they intend to qualify and authorize personnel responsible for signing the EASA Form One (which is a component airworthiness release certificate). If the authorities are happy with the procedure, they will approve it and from that moment it will become “law” within the given Part 145 shop.

Therefore, there is no license requirement (or even no license at all) for people working on component maintenance. They training and evaluation procedures should be clear and adhered to at all times, but apart from that anyone can be employed by a shop to do the work.

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Posted in Aircraft Engineers and Mechanics, Aircraft Maintenance Management, Aircraft Maintenance Regulations, Maintenance, Maintenance of Aircraft, Maintenance of Components
7 comments on “Aircraft Maintenance Certification – Certifying Staff, License Categories and Internal Authorizations
  1. Sam says:

    I really appreciate that….. This article was so useful
    Thanks alot

  2. Ricardo Nunes says:

    Please can you answer to my question , becouse for me it is not clear if a B2 certifing staff can sign a certificate of release to service during base maintenance for a small helicopter single engine piston used in Commercial Air transport operations..
    Can you please help me?
    Thanks in advance

  3. Ricardo Nunes says:

    Reformulating :
    Please can you answer to my question , becouse for me it is not clear if a B1 or B2 certifing staff can sign a certificate of release to service during base maintenance for a small helicopter single engine piston used in Commercial Air transport operations..
    Can you please help me?
    Thanks in advance

  4. Ron Taber says:

    Hello there,
    I am really impressed along with your writing skills and also with the format on your blog. thanks for the informative post.

  5. Habib says:

    Very useful and Interesting. Please, is it mandatory for Line maintenance activities to have both B1 & B2 Certifying staff?

  6. Andrew says:

    Good day Sir,
    Your articles in airline basics are enlightening and I thank you for that. Could you please explain the difference between “maintenance release” and “airworthiness release” to me? Thank you

  7. Global Aviation Infrastructure LLC says:

    Thanks for the post. very informative and well described post it was. Really helpful for many people.

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