Component MRO isn't always a simple case of "replace the part." A large share of the work is repair: figuring out whether a damaged component can be brought back to a serviceable, airworthy condition instead of scrapped and replaced outright. Three terms come up constantly in that conversation — DER, FOD, and sub-assembly repair — and they're worth unpacking.
DER repairs
A DER (Designated Engineering Representative) repair is one performed under an engineering repair approval that goes beyond what the original OEM manual covers. When damage falls outside the manual's standard repair limits, a DER-approved engineering disposition provides an airworthy, regulator-recognised path to repair the part anyway — rather than defaulting straight to scrap.
FOD repairs
FOD stands for foreign object damage: dents, nicks, or impact damage caused by debris, tools, or other objects coming into contact with a component. Not all FOD is critical — much of it falls within standard repairable limits — but assessing it correctly requires careful inspection against the applicable damage tolerance data before deciding whether a repair, a DER disposition, or replacement is the right call.
Sub-assembly repairs
Many components are themselves built from smaller sub-assemblies. When only one sub-assembly has failed or is worn beyond limits, replacing the entire unit is often unnecessary — and expensive. A sub-assembly repair targets just the failed portion, which typically costs less and takes less time than a full-unit exchange, provided the rest of the component checks out during inspection.
Why this matters for cost
Together, these three capabilities are what separate a component MRO provider that can only replace parts from one that can genuinely repair them. Every DER repair, FOD assessment, or sub-assembly fix that avoids an unnecessary full-unit replacement is money and lead time saved — which is exactly why RepMan treats these as core capabilities rather than exceptions.
Curious whether a specific component in your fleet is a repair or replacement candidate? Send us the details and we'll take a look.