Instructions for Continued Airworthiness

Things used to be so straightforward. We had the manufacturer’s maintenance manual, and that was that. Now we have the "Type Certificate Holder’s Instructions for Continued Airworthiness (ICA)." Sometimes, we even see "Instructions for Continued Airworthiness or Manufacturer’s Maintenance Manual." Other than a bureaucratic tendency to never be satisfied with one word where half a dozen will do, what’s the difference?
In practice, not a lot. Obviously, the traditional maintenance manual contained instructions for continued airworthiness. Yet, a couple of points are worth noting. First, despite some regulatory references to the contrary, which will be amended in due course, ICAs are the responsibility of the type certificate holder, not the manufacturer. At one time, the two terms were synonymous, but that is no longer the case. That brings us to the second point — the new terminology coincided with the inclusion of ICA as a condition for type certification. In the case of transport category aeroplanes, STD 525.1529 requires the applicant to "—prepare Instructions for Continued Airworthiness in accordance with Appendix H to this chapter that are acceptable to the Minister." Similar provisions apply to other categories, and to modifications approved by Supplemental Type Certificate (STC).

Some "acceptable" confusion
That word "acceptable" has confused some people, leading them to ask whether ICAs are approved or not. The fact is, it really doesn’t matter. Actually, about the only maintenance recommendations that do need approval are those that result in a major change to the product. That’s why Structural Repair Manuals (SRMs) are sometimes approved, because the repairs described may cause the product to deviate from its original approved design. Even those approvals may not really be necessary under the Canadian domestic system, because the CARs recognize the concept of "specified data," i.e., data from sources the Minister has specified as not requiring approval. The SRM is one such source. However, since other authorities may not have similar provisions, SRMs might be approved for use in those foreign jurisdictions.
So, what does "acceptable" mean? Well, in this context, it’s merely the standard to be met. Unlike the design standards for structures and systems, which often involve quantitative criteria, this standard is qualitative. Instead of specifying a rigid format, style, and content; it simply states that ICAs have to be acceptable to the Minister. To avoid this standard being too subjective, the applicable appendices provide information on the main features to be included.
The appendices require ICAs to be in the form of a manual or manuals, leading to the question of whether or not service bulletins are included. In practice, that depends on the circumstances. Applicants for a type certificate have to submit a program to show how changes to the ICAs will be distributed, and the service bulletin system is often part of that program. For some small, basic aircraft, it may well constitute the entire program. Therefore, in the absence of a specific statement to the contrary, service bulletins and equivalent publications should be regarded as part of the ICA. A degree of judgment is required here, because some manufacturers, as a service to their customers, publish newsletters or other semi-official advisory publications that are not intended to be formal recommendations. Usually, such publications contain a disclaimer to that effect.

Do ICAs have to be followed?
Once again, it depends on the circumstances. CAR 571.02 requires all maintenance to be done using the most recent methods, techniques, practices, parts, materials, tools, equipment and test apparatus specified in the ICA; equivalent methods, techniques, and practices; or recognized industry practice. That clearly implies that ICAs are the default source for maintenance data, but also indicates that other sources may be acceptable. The main difference is we know for sure that ICAs are acceptable, because that was a requirement for type certification. We cannot be so certain of the other sources.
Included in equivalent methods, techniques and practices, etc., are sources the Minister has identified as generally acceptable, such as FAA Advisory Circulars 43.13 1 and 2, or the UK CAA Civil Aviation Inspection Procedures. ICAs for similar products may also be used for guidance. The acceptability of these sources is subject to an additional caveat — the AME must ensure that the information is applicable to the particular case, and not in conflict with the type certificate holder’s recommendations.

Show your work
In a perfect world, the various publications cited here would be all that were needed. Unfortunately, that’s not the world we live in. Sometimes we have to fall back on recognized industry practice — the general "folklore" of the profession that may not be written down anywhere. You should be aware that if you apply these kinds of practices, and are subsequently challenged as to their acceptability, you might have to show that they are indeed standard practice in the industry. That could mean proving they are recognized and widely used in the applicable context by your peers. Context is particularly important here — a technique that is appropriate for a small aircraft in the bush may not be acceptable for a transport category aircraft in scheduled passenger service.

What about schedules?
You may have noticed that an important element of the ICA is not mentioned at all in CAR 571.02. While it speaks of "methods, techniques and practices, etc.," there is no reference to schedules. In other words, this regulatory section covers the "how" of maintenance, but not the "what" or the "when." That’s because scheduled maintenance is an operational issue, addressed in the General Operating and Flight Rules. Every aircraft must be maintained to an approved schedule. That could be the standard (generically approved) annual inspection for small aircraft, or a schedule specifically approved for the operator. Accordingly, there is no regulatory requirement to follow the type certificate holder’s recommended schedules. They just have to be taken into account when developing the operator’s schedule, with any major differences supported by appropriate technical justification.