Aircraft Modifications

Implications for continued airworthiness and corrosion control

This concept was foreign to some of the maintenance industry since with most field approvals, continued airworthiness was considered to be handled just fine by the inspection/maintenance program issued by the manufacturer. Aircraft certification disagrees, so today an FAA Order is available to help us understand what must be included in any ICA created to support a major alteration or repair. That order, “FAA Order 8110.54 - Instructions for Continued Airworthiness Responsibilities, Requirements & Contents” is available at, thousands of modifications were performed well before the FAA began requiring ICAs. This is where the problem lies.

Those aircraft are still airworthy and the approvals are still valid, except in a couple of cases, such as moving aircraft operations from Part 91 to Part 135. When an aircraft undergoes an FAA conformity inspection in preparation for being added to the operations specifications for an air carrier under Part 135, some FAA offices are now requiring that all major modifications be reviewed. They may also require ICAs to be developed for those that do not already have one, even though the modification was approved when it was accomplished.

It seems ridiculous to me that the aircraft is airworthy when operating under Part 91 and suddenly not when being added to the air carrier certificate. I know that many of you have already been up against that, and as I mentioned before, the FAA Order can be an aide in making sure that all of the requirements have been met before providing an ICA to the FAA for approval.

Corrosion control
The second case that I’m referring to is the case in which a corrosion prevention and control program (CPCP) is required. Beginning with large scheduled airline aircraft, and as a result of the 737 that came apart in flight several years ago, the FAA implemented the CPCP concept. To begin with, an Airworthiness Directive is issued requiring that the operators of affected aircraft implement a CPCP. ADs were quickly issued for several of the large airline transport models.

The CPCP model used for the larger operators has been worked and modified over the last few years and seems to fit the major airlines well. Each of these operators generally operates tens and hundreds of these models, so implementing a CPCP into their standard program is relatively easy.

This will not be the case for the business aviation community. Soon business aircraft manufacturers will begin to incorporate CPCPs into their recommended inspection programs — some already have. On the surface, it sounds like the manufacturers are doing the ground work and all we will need to do is complete the inspections. Not quite — the manufacturer will set a starting point for the CPCPs they create and that inspection will cover all of the standard aircraft. The truth is the only standard aircraft is one that has not received a major modification.

When aircraft reach the CPCP implementation deadline defined by the manufacturer in hours, cycles, and/or date, the FAA will require that operators obtain a letter of authorization (LOA) for their aircraft-specific CPCP. This is similar to when an aircraft moves from Part 91 to Part 135. In order to receive that CPCP LOA, the operator will be required to review all major modifications (alterations and repairs) accomplished on that aircraft to determine if an ICA exists and if that ICA includes inspection criteria to ensure corrosion control for the structural elements of the modification.

It is the FAA’s position that any modifications performed after delivery must be reviewed and verified to meet the airworthiness requirements for the aircraft and provide for continued airworthiness ongoing. This won’t be easy.

Unlike the major airline operators, hundreds of operators will need to have help in developing new ICAs for their modifications that will include all of the necessary inspections, or include a statement from the FAA that the modification does not require any special inspections. Neither Flight Standards nor Aircraft Certification will have resources available to handle the effort with any reasonable timeframe. The only other option that we will have is to find industry engineers designated by the FAA to approve data and to help in the evaluation and creation of ICAs. Once created, the ICAs will still need to be reviewed by flight standards and an LOA issued for that aircraft.

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