The aviation community has been having serious discussions about breaks in the aircraft parts supply chain since the beginning on Covid. It appears that the problems may continue to plague the industry. One of the issues with “supply chain problems” is that it is not just one problem. If it was one problem then we could focus on solving the one problem to eliminate the industry’s supply chain woes. Instead, we are seeing that Covid was just one in a series of issues that have impacted our supply chain, and that are likely to continue plaguing the aircraft parts supply chain.
Supply Chain Solutions
This article is focused on examining a few of the supply chain solutions that have been shown to be successful.
Of course, the most preferable solution is to solve the underlying problem by creating availability of the missing item; but this is not always realistic. As a consequence, it is often necessary to circumvent the supply chain disruption through some form of substitution.
A key concern in any substitution effort is airworthiness. Everything else is secondary to this concern. In the FAA’s system, FAA approval is an important strategy for supporting airworthiness questions.
Parts Manufacturer Approval (PMA)
One easy substitution option is articles produced under parts manufacturer approval, or PMA. This can be an easy option to adopt because FAA-PMA articles are typically approved three different ways. The design is approved by the FAA, showing that the design is consistent with the FAA’s airworthiness standards. The production quality system is approved by the FAA, showing that the production quality assurance system is adequate to ensure that each article conforms to its approved design and is in a condition for safe operation. Finally, the eligibility of the article is approved by the FAA, showing that it has been found safe for installation on at least one specific type of aircraft.
Because of the FAA’s approval system, an installer can have confidence that the article is safe and airworthy for installation in the approved installation eligibilities. But sometimes an operator may want to install a PMA article into an aircraft that is not listed on the eligibility list found on the PMA supplement. This particularly happens when the application for adding an eligible installation is pending, but this is not the only fact pattern in which an air carrier can make its own determination of installation eligibility.
If an operator may want to install a PMA article into an aircraft that is not listed on the eligibility list found on the PMA supplement, then the air carrier must make its own finding of eligibility. This is typically accomplished through an Engineering Order or EO (this can also be called by other names, like an Engineering Change Order or an Engineering Design Order). An air carrier can cooperate with the manufacturer of the article to develop the engineering data necessary to substantiate such an EO.
One important feature of the modern PMA marketplace is that PMA suppliers recognized many years ago that one of the problems that they are solving is availability; so most independent FAA-PMA companies will try to maintain inventory so that they can support the industry “on demand.” In the most extreme cases, even OEM repair stations who are unable to obtain needed articles have purchased PMA articles and used them in their repairs. This “OEM usage” was first reported by air carriers in the depth of Covid but we’ve confirmed in the past few months that the solution continues to be used by both repair stations and operators.
DER Repairs
The FAA approves technical data in the context of type certification of an aircraft, but what about technical data that is needed by the industry to support the aftermarket? Repair and alteration data is often approved by designated engineering representatives (DERs). DERs are individuals who have been granted the authority to assess and approve technical data. The approval means that the applicant has shown compliance with the relevant airworthiness standards, and the DER has made a corollary finding that the technical data adequately demonstrates compliance. This show-find sequence is at the root of most FAA approvals. The DER is authorized to stand in for the FAA and make technical findings on behalf of the FAA.
DERs typically have different function codes, and they usually can only approve data within the context of their authorized function codes. For example, a DER with RS-DER authorization is allowed to approve repair specifications on behalf of the FAA.
Repair specifications provide an alternative to the methods, techniques and practices contained in the current manufacturer’s manuals, service bulletins, and instructions for continued airworthiness. They typically involve the approval of data supporting a major repair. RS-DER data can be serial-number-specific or it can be general in nature.
When the industry talks about DER repairs, and parts that have been subject to DER repairs, they are talking about a repair that was not in the manufacturer’s manual system (or a repair that had limitations circumvented by the DER-approved data). The DER reviews and approves the data supporting the repair. This approval confirms that the data is consistent with the FAA’s airworthiness standards. When the DER is acting within his or her authorizations, the DER approval carries the same weight as an approval from an FAA employee.
In short, DER repairs represent an FAA-approved method for performing maintenance work to return the aircraft article to an airworthy condition.
Used Serviceable Material
Another popular source of aircraft articles is the used serviceable material (USM) market. These are used rotable components that are capable of being overhauled and approved for return to service.
In many cases, the USM market is being fed by disassembly of aircraft. An end-of-service aircraft may be disassembled before it is scrapped, with anywhere from 200 to over a thousand articles being removed from the aircraft and sent back through the MRO market for overhaul.
While the USM articles are “approved parts” at the time of production, they are not presumptively airworthy at the time of removal. Thus, they will typically be sent to a properly rated MRO for overhaul after being disassembled.
Historically, the weak link in this process was the disassembler: in the United States, disassembly of end-of-service aircraft is not directly regulated. Modern commercial and airworthiness practices have changed this, and have provided a higher level of safety assurance.
Many companies performing this disassembly are performing it under the auspices of the Aircraft Fleet Recycling Association (AFRA) Best Management Practices (BMP). The AFRA BMP is a management system with elements designed to protect the airworthiness of the removed articles. The AFRA BMP also has a heavy focus on environmental compliance during the disassembly process, to help meet both domestic and international environmental standards.
Disassembly companies can choose to implement a quality assurance system in accordance with the AFRA BMP; and then the AFRA auditors can audit the company to the AFRA BMP standards to ensure that the disassembly company has adequate airworthiness and environmental systems to meet international norms. The AFRA BMP is helping to raise the bar on safe handling of USM at the time of removal, which helps to ensure that parts are more recoverable (because they are less likely to be damaged upon removal).