Designated Engineering Representatives are individuals granted authority by the Federal Aviation Administration to perform specific certification tasks on behalf of the agency. The FAA Administrator delegates this power to highly qualified engineers who demonstrate both technical expertise and a thorough understanding of aviation regulations per CFR Part 21. DERs serve as an extension of the FAA’s certification office, allowing the agency to manage its workload while maintaining safety standards across the aviation industry.
For fleet operators managing AOG situations or repair stations working on aircraft component modifications, understanding how DERs function directly impacts lead time and operational continuity.
Learn How PAG Manufacturing/DER Services Help Operators Stay in the Air
At a Glance, DERs:
- Review Technical Data
- Confirm Regulatory Compliance
- Approve Engineering Documentation (on behalf of FAA)
The role requires meeting demanding standards in their technical discipline. Engineers must show years of hands-on experience in their specialized area, possess detailed knowledge of applicable airworthiness standards, and maintain a track record of reliable work in aviation. The FAA does not hand out these designations lightly. DERs essentially act with the same authority as FAA engineers when reviewing and approving technical data.
DER vs. Other Aviation Designees
The aviation certification system includes several types of designees, each serving distinct functions within the regulatory framework:
Designated Airworthiness Representatives (DARs) focus on physical inspection and conformity checks of aircraft. They examine actual hardware, verify that manufactured parts match approved designs, and issue airworthiness certificates. DARs typically work on certification activities for smaller aircraft, experimental aircraft, or individual projects requiring hands-on conformity verification.
Designated Engineering Representatives (DERs) review technical data and approve designs for DER repair and major repair projects. Rather than inspecting physical components, they evaluate engineering documentation—drawings, calculations, test reports, and compliance substantiation. Consultant DERs handle ongoing DER approvals for operators, airlines, and repair stations, providing the engineering expertise needed to certify modifications and repairs.
Organization Designation Authorization (ODA) represents a broader delegation where an entire company receives authority to perform certain certification functions—including DER repair and major repair approvals—through its engineering staff. ODAs allow manufacturers and large MROs to streamline internal certification processes.
Key distinction: DERs work as individuals, providing flexibility for smaller operators or specialized projects needing outside DER approval for aircraft parts, PMA parts, or aircraft component modifications. This makes them valuable for repair stations and MRO facilities that need responsive engineering support without building internal certification infrastructure.
Different Types of DERs and Specific Functions
The FAA organizes Designated Engineering Representatives into distinct categories based on their technical expertise and the certification work they perform. Each type serves a specific function within the aircraft certification process.
Manufacturing DERs
Manufacturing DERs work directly with production certificate holders to verify that aircraft components meet approved design specifications during manufacturing. Key responsibilities include:
- Reviewing manufacturing procedures and process documentation
- Inspecting production facilities for compliance
- Approving process changes that affect how aircraft parts are built
- Verifying that manufactured parts match exactly what was approved in technical data
- Evaluating whether new production techniques maintain conformity with original approved design data and FAA regulations
Design DERs
Design DERs handle the DER approval of engineering data for aircraft modifications, DER repair, and new designs. Their scope includes:
- Reviewing technical drawings and engineering calculations
- Analyzing structural and system changes for compliance with applicable airworthiness standards
- Evaluating modifications from new equipment installations to structural reinforcements
- Approving technical data that meets regulatory requirements
- Serving as the technical bridge between engineering teams and FAA certification for major repair and modifications
Flight Test DERs
Flight Test DERs oversee and approve flight testing programs required for aircraft certification and major modifications. Their work encompasses:
- Developing comprehensive flight test plans
- Monitoring test flights and collecting performance data
- Analyzing results to demonstrate compliance with applicable regulations
- Certifying test outcomes for type certification or supplemental type certificate approval
- Evaluating whether aircraft performance and handling meet safety standards
Specialized DER Categories
Beyond primary categories, DERs hold specialized authorizations in specific technical disciplines:
- Structures specialists: Airframe components, load analysis, and structural integrity evaluations
- Systems and equipment experts: Hydraulic systems, environmental controls, and mechanical installations
- Powerplant and propeller DERs: Aircraft engine installations, fuel systems, and propeller designs
- Avionics and electrical system DERs: Navigation equipment, communication systems, and electrical installations
This specialization allows complex aircraft projects to receive expert review in each technical area, with multiple designated engineering representative consultants often contributing their specific expertise to a single certification project.
Why DERs Matter
Designated engineering representatives serve as force multipliers in the aviation certification landscape. Their authorization to act on behalf of the FAA creates advantages that directly impact airlines, MROs, and repair stations.
Faster Certification Timelines
Engineering representatives help alleviate FAA approval bottlenecks that can stall projects for months:
- DER-approved technical data for repairs, modifications, or STCs returns aircraft to service faster than waiting for direct FAA review
- Critical during AOG situations where every hour of downtime translates to lost revenue
- Repair stations working with consultant DERs move through approval stages quickly, reducing lead time
- The difference between a two-week DER approval and a three-month wait can determine whether a fleet operator meets seasonal demand
Cost Savings for Operators and MROs
Project costs drop significantly when designated engineering representatives handle certification work:
- Operators avoid extended aircraft downtime during modifications
- Fewer wet lease arrangements needed to maintain flight schedules
- Engineering resources focus on problem-solving with aircraft components, PMA parts, and OEM parts rather than administrative delays
- Cost savings compound across fleet-wide modifications or recurring DER repair approvals
Maintaining Safety Standards
DERs operate under the same technical requirements as FAA engineers:
- Follow applicable airworthiness standards and CFR Part regulations
- Professional credentials and technical discipline expertise on the line for every approval
- FAA maintains oversight through regular audits with authority to revoke DER authorization
- Engineering representatives bridge technical expertise with regulatory knowledge
Supporting Innovation
DERs make certification pathways accessible beyond major manufacturers:
- Regional MROs can pursue STCs for specialized modifications without hiring full regulatory affairs departments
- Enables rapid response to operational needs—cargo conversions, avionics installations, aging fleet solutions
- Parts manufacturer approval evaluations for new parts versus like-new condition alternatives
- Supports industry evolution including sustainable aviation fuel adoption and emissions reduction initiatives
Partnering With DER-Supported Organizations
Designated engineering representatives bridge technical aviation expertise and FAA regulatory authority. Their ability to approve technical data and certify compliance keeps aircraft operational while maintaining the airworthiness standards that protect everyone in flight. For operators facing AOG situations, pursuing modifications, or managing DER repair needs, access to qualified DER support directly impacts lead time, cost, and operational continuity.
Why Precision Aviation Group
Aircraft modifications, DER repair services, and engineering certification support require a partner with both technical depth and regulatory knowledge. PAG’s team works directly with DER professionals to deliver rapid response times and full compliance for commercial aviation, military, and business aviation operators.
DER Compliance: PAG provides DER-approved solutions for hard-to-find parts and specialized operational repairs and upgrades
Integrated solutions: Our Inventory Supported Maintenance, Repair, and Overhaul (ISMRO®) business model provides spares and repairs in one program—speed and simplicity when you need both
Global consistency: Standardized service quality across all locations, backed by FAA, EASA, CAAC, and AS9110 certifications
24/7 Support: Round-the-clock reliability for critical operations and AOG situations
