If you manage a fleet or run a component shop, you have probably seen “DER repair” on a quote or a work order and wondered exactly what you were buying — and whether it holds up to the same airworthiness standard as an OEM part. The term gets used loosely, which makes it harder to evaluate. This primer sets the foundation for our DER series: what a DER repair actually is, who approves the engineering behind it, and where it fits alongside OEM new parts and PMA. The short version is that a DER repair is a documented, FAA-approved way to return an existing component to an approved condition.

What a DER Is

DER stands for Designated Engineering Representative. A DER is an individual engineer the FAA authorizes under 14 CFR Part 183 — specifically §183.29 — to act on the agency’s behalf within a defined specialty. Those specialties include structural, powerplant, engine, propeller, systems and equipment, radio, flight analyst, flight test, and acoustical engineering. In practice, the FAA cannot personally review every piece of engineering data in the national airspace system, so it delegates certain compliance findings to qualified private-sector engineers it has vetted and appointed. Organizations can hold equivalent authority through an Organization Designation Authorization (ODA), whose unit members make similar findings within a company.

The key idea is delegation. A DER is not a vendor selling a shortcut; a DER is a person carrying a slice of FAA authority to determine that engineering data complies with the applicable airworthiness standards. That authority, and the standard it is held to, is what gives a DER repair its credibility.

What a DER Repair Actually Is

A DER repair is an engineering-developed, FAA-approved repair process or configuration that restores an existing component to an approved condition. That is the whole distinction in one sentence. You are not manufacturing a new article — you are taking a part that already exists, is worn or damaged in a defined way, and returning it to a condition at least equal to its original or properly altered state. The engineering behind that repair, developed and substantiated by a DER, is what the FAA reviews and approves.

This matters because “repair” and “replace” are two fundamentally different paths through the regulations. When a component comes off an aircraft with damage that would otherwise scrap it, a qualified repair can bring it back into service without buying a new unit. The DER’s job is to prove, with data, that the specific repair does not compromise the part’s structural integrity, function, or life. When that proof is accepted, the repair becomes an approved way to address that condition — sometimes for a single part, sometimes for a whole class of recurring damage.

The Role of FAA Form 8110-3

The document at the center of a DER repair is FAA Form 8110-3, the Statement of Compliance with Airworthiness Requirements. It is worth being precise about what this form does and does not do, because it is widely misunderstood.

Form 8110-3 is how a DER approves — or recommends approval of — the engineering and technical data behind a repair. It documents findings of compliance: the DER is stating that the repair data meets the applicable airworthiness standards. That is its entire function on the data side. It applies across many project types, including type certificates, supplemental type certificates, PMA, major repairs, and major alterations.

What the 8110-3 is not is equally important. It is not a work order. It does not authorize anyone to manufacture a part. It does not grant operational approval to fly. And it does not, by itself, put a wrench on the component. It approves the recipe, not the meal. The physical work still has to be performed and released by the appropriate people under separate rules — which is where Part 43 comes in.

How the Physical Repair Gets Done — Part 43

Once the engineering data is approved, the actual repair is performed and returned to service under 14 CFR Part 43. An appropriately rated repair station or mechanic does the hands-on work, following the approved data, and then returns the article to service through the standard maintenance-record process. The 8110-3 supplies the approved data; Part 43 governs who may do the work and how it is signed off.

Part 43 also draws the line between “major” and “minor” repairs (its Appendix A gives the definitions). Major repairs — think engines, primary structure, landing gear — require approved data, and a DER’s 8110-3 is one recognized route to that approved data. When the repaired component is released, an FAA Form 8130-3 Authorized Release Certificate can accompany it, giving the buyer a clean airworthiness record. So the paper trail on a completed DER repair has two distinct pieces: the approved engineering data on one side, and the maintenance release under Part 43 on the other. We cover that documentation flow in detail in how a DER repair gets approved.

Where DER Repairs Sit — Between OEM New and PMA

It helps to picture three routes for keeping an aircraft supplied with airworthy parts. The first is OEM new: buy a factory-fresh replacement from the original manufacturer. The second is PMA — Parts Manufacturer Approval — where an approved supplier produces a new replacement article under its own FAA design and production approval. The third is the DER repair, which does not make a new part at all; it restores the part you already have.

Seen this way, a DER repair and a PMA part solve the same underlying problem — a serviceable, approved component — by opposite means. PMA produces; DER repair restores. Both are held to the airworthiness standard, and both add a qualified, competing source alongside the OEM. That competition is where the value sits: material cost is a meaningful share of maintenance spend, and a documented second source supports availability and cost discipline without lowering the bar. For a side-by-side comparison, see DER repair vs. PMA and, from the parts side, PMA vs. DER repair. You can also browse our repairs overview for the broader picture.

How AviaFix Approaches DER Repairs

AviaFix treats a DER repair as an engineering commitment, not a marketing label. That means the approval basis has to be substantiated before we put a component into a repair path — the compliance findings, the approved data, and the return-to-service records need to line up so the package clears a customer’s receiving inspection on the first pass. When a repair cannot be substantiated to that standard, we decline it rather than defend it after the fact. We do not disparage OEMs; we add an approved, documented alternative that has to meet the same airworthiness requirement, and we let the records speak for themselves.

Frequently Asked Questions

Is a DER repair as airworthy as an OEM part? A properly executed DER repair is held to the airworthiness standard in Part 43: the item must be restored to a condition at least equal to its original or properly altered condition. The engineering data is approved through a DER’s compliance findings, and the work is performed and released by a rated repair station or mechanic. The value it adds is a documented, competing source — not a relaxed standard.

Does FAA Form 8110-3 mean the repair is done? No. Form 8110-3 approves the engineering data behind the repair and documents findings of compliance. It is not a work order, it does not authorize production, and it does not grant operational approval. The physical repair is a separate step, performed and returned to service under 14 CFR Part 43, often with an FAA Form 8130-3 accompanying the released article.

How is a DER repair different from a PMA part? A PMA part is a newly manufactured replacement article approved under the FAA’s Parts Manufacturer Approval process. A DER repair restores an existing component to an approved condition instead of building a new one. They are distinct aftermarket routes that address the same need by different means; DER repair vs. PMA walks through when each fits.

Who is allowed to develop and approve a DER repair? The engineering data is developed and its compliance is found by a Designated Engineering Representative — an engineer the FAA authorizes under 14 CFR Part 183 within a specialty such as structures or powerplant — or by an ODA unit member holding equivalent authority. The hands-on repair is then carried out by an appropriately rated repair station or mechanic under Part 43.

Sources & Further Reading

Related reading: DER Repair vs. PMA · How a DER Repair Gets Approved · Repairs overview

← All DER Insights