A Designated Engineering Representative (DER) can be the difference between sitting in an Original Equipment Manufacturer (OEM) queue and returning to service on time. Leaders don’t choose repair methods—engineering does under approved data—but you do approve scope, risk, schedule, and evidence. This guide shows when DER vs OEM matters, what documents to expect, and how to green-light a fast, defensible path to return to service (RTS).
A DER is an FAA-appointed expert who can approve technical data for repairs/alterations (e.g., structures, systems, avionics). The DER’s output is the data approval (commonly documented via FAA Form 8110-3). Maintenance then executes the work per that data and issues the release to service (e.g., FAA Form 8130-3 or EASA Form 1, as applicable).
Goal: pick the fastest compliant route that preserves asset value.
As a leader, you approve the plan—not the method. Confirm the data basis (SRM/OEM or DER), where it will be executed (on-site vs. facility), the turnaround time (TAT) and budget, and the evidence pack you’ll receive at release.
On-site feasibility (field or AOG).
When approved data permits maintenance away from the approved location, some composite and structural work can be completed at the aircraft.
Typical on-site candidates include radomes, nacelle structures such as inlet or fan cowls, selected thrust-reverser and fairing panels, flight-control surfaces like ailerons, flaps, slats, spoilers, and localized skin or panel repairs within published limits.
Field execution is appropriate only when environmental control and inspection can be assured under your procedures. This approach avoids ferrying and reduces queue risk, which can shorten the return-to-service window.
When a fixed facility is required.
Some repairs belong in a shop environment. This is true when specifications require fixed assets or tightly controlled conditions, or when access and dimensional control would be compromised in the field.
Plan the shop sequence and run planning, documentation, and materials preparation in parallel so turnaround stays predictable while meeting the technical standard.
What leaders should require.
Ask for one decision brief that names the data basis, whether Structural Repair Manual (SRM), original equipment manufacturer (OEM), or Designated Engineering Representative (DER)-approved. Confirm the proposed execution location and the reason it was chosen. Require a realistic turnaround-time and cost profile that operations can plan against.
Define the evidence to be captured for audit, including defined as-run process records, appropriate non-destructive testing (NDT) results, and the release documentation. Request milestone reporting aligned to your procedures for maintenance away from the approved location so the maintenance control center can schedule confidently toward a firm return-to-service date.
Think in three lanes: (1) engineering data, (2) maintenance evidence, (3) RTS paperwork.
Is a DER repair “less official” than an OEM method?
No. A DER approves the data (Form 8110-3). A certificated repair station performs the work and issues the normal RTS (8130-3/Form 1). Both paths are valid when executed correctly.
When should I prefer DER over OEM?
When OEM support is unavailable, slow, replace-only, or cost-prohibitive—and when a DER repair can meet airworthiness requirements and your schedule.
How do I keep audits painless on a DER job?
Require a traceable file: traveler tied to the approved data, material COCs, as-run process evidence, NDT reports, inspection sign-offs, and the correct RTS document—no post-release fixes.
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