Inside the Process of Qualifying Aircraft Seals for FAA Approval

A single failed seal can ground an aircraft. A non-compliant replacement can ground an entire program.

This is why the FAA requires rigorous approval for even the smallest components installed on certified aircraft. Seals may seem simple. In many cases, they are elastomer components designed to contain pressure or exclude contamination. But their performance directly affects safety and system integrity. In aerospace applications, they must function reliably through extreme temperature cycling, chemical exposure, and thousands of pressure changes over their service life.

In This Blog:

• What Is FAA PMA?

• Why Qualifying Aircraft Seals Is Especially Complex

• Reverse-Engineering an Aircraft Seal: Establishing Design Intent

• Why Ergoseal Is Pursuing the Test and Computation Path

• Why We’re Sharing This Work

For aircraft manufacturers, MROs, and aerospace engineers, replacing a seal is never a simple sourcing decision. Any component installed on an FAA-certified aircraft must meet strict airworthiness requirements that govern not only how the part performs, but how it is designed, validated, and produced.

FAA Parts Manufacturer Approval (PMA) exists to ensure replacement parts meet those requirements. This is the first in a three-part series that examines what that process involves, starting with the early stages of analysis and validation.

This series is intended to provide practical clarity. PMA is often referenced in procurement specifications and supplier conversations, but the work behind it is less visible. By documenting our journey, we aim to help aerospace teams understand what PMA really requires — and what it means when evaluating replacement component suppliers. Whether you're managing supply chain risk, qualifying new vendors, or troubleshooting availability issues, understanding this process can inform better decisions.

What Is FAA PMA?

FAA PMA is an authorization issued by the Federal Aviation Administration that allows a manufacturer to produce and sell replacement parts for type-certificated aircraft.

Importantly, PMA is not just a manufacturing approval. It includes two equally critical elements. Design approval demonstrates that the part meets applicable airworthiness requirements. Production approval verifies that the manufacturer can consistently produce the part to the approved design.

Only when both are satisfied can an approved part be legally installed on an FAA-certified aircraft.

“PMA shows that a part’s design meets airworthiness requirements and that it is manufactured under an FAA-approved quality system, so every part conforms to that design,” says Ergoseal Business Operations Manager for Aerospace, Lazarus Adamidis.

“The FAA separates design and production approval because they address different risks. Design approval ensures that the part is safe in concept, while production approval ensures it is consistently and correctly built. Approving only one would leave gaps, either a good design made poorly or a well-made but unsafe design. Requiring both ensures safety in theory and in practice.”

Why Qualifying Aircraft Seals Is Especially Complex

Unlike bolts, fasteners, or other standardized hardware, aerospace seals are often highly application-specific. A seal in a hydraulic actuator faces radically different conditions than one in a fuel system or environmental control system. Operating temperatures can range from subzero conditions at altitude to hundreds of degrees in engine environments. Pressures can cycle thousands of times. Fluids vary from hydraulic oils to aggressive solvents.

These variables drive specialized designs: proprietary geometries, custom material formulations, and performance requirements tied to the specific system environment. In most cases, OEM design data for these seals is not publicly available or licensable. That means manufacturers seeking PMA must independently demonstrate that their replacement part performs identically (or better) than the original.

For seal manufacturers, this raises the bar significantly. It's not enough to match dimensions. Material behavior, compression set resistance, durability, and functional performance all have to be proven through documented engineering analysis and rigorous testing.

The stakes are high, Adamidis explains:

“Seals are safety-critical in aerospace because they often sit at system boundaries (containing pressure, fluids, or fire), and a small failure can quickly escalate into a major safety issue. Their qualifications are more complex than expected because seal performance is highly sensitive to environment, aging, installation, and operating variability. Even minor changes in temperature, pressure cycling, or material condition can cause failures over time.”

Reverse-Engineering an Aircraft Seal: Establishing Design Intent

When original design data is not available, qualifying a replacement aircraft seal requires a fundamentally different approach. Rather than working from licensed drawings or specifications, manufacturers must establish design intent through direct analysis of the existing, certified part.

This process is often called reverse-engineering, but in an aerospace context, it's less about replication and more about understanding. The goal is to determine how the seal functions within its system, what performance characteristics are critical, and how those characteristics can be validated to FAA standards.

For Ergoseal, this initial phase focuses on building a clear technical baseline. That includes evaluating geometry, material behavior, and how the seal interfaces with surrounding components such as mating surfaces, tolerances, compression rates, and installation conditions. Each element informs how performance requirements are defined and how compliance with FAA airworthiness standards can ultimately be demonstrated.

At this stage, the emphasis is on discipline and documentation. Before any formal testing begins, assumptions must be challenged and design decisions clearly supported. This groundwork is essential for ensuring that later validation efforts are meaningful and defensible under FAA review.

“In an FAA approval context, reverse-engineering means more than copying a part’s shape,” Adamidis notes. “Approval means developing the complete, approved design data needed to show the part meets airworthiness requirements.”

In practice, this requires a detailed understanding of the seal’s materials, geometry, tolerances, and manufacturing processes, as well as how it performs in its installed environment. Establishing clear design intent allows critical characteristics to be defined, manufacturing controls to be put in place, and long-term airworthiness to be demonstrated. Without that foundation, it becomes impossible to validate performance or ensure consistent production over time.

Why Ergoseal Is Pursuing the Test and Computation Path

There are multiple pathways to FAA PMA. When original design data is licensed or otherwise available, manufacturers may pursue approval through identicality — essentially demonstrating that the replacement part matches the OEM design in every material aspect.

In many cases, that data is not accessible. For its current project, a specific aircraft seal, Ergoseal is pursuing the test and computation path. This method relies on independent engineering analysis and validation to demonstrate that the replacement part meets applicable airworthiness requirements.

While more demanding, this approach provides a clear, evidence-based foundation for approval. It allows performance to be demonstrated directly through testing and analysis, and ensures that design and production decisions are supported by documented engineering work rather than assumptions.

At this stage, the emphasis is on establishing that foundation. Requirements are being defined, engineering and quality disciplines are being aligned, and early design decisions are being documented to support later validation and FAA review.

Why We’re Sharing This Work

FAA PMAis often discussed as an outcome — a checkbox on a supplier qualification form or a line item in a parts catalog. But the work that leads to it is less visible. For aerospace teams managing programs, qualifying suppliers, or navigating component obsolescence, this can make it difficult to understand what approval really represents, why it takes time, or what differentiates one PMA holder from another.

By sharing this process, Ergoseal aims to provide greater transparency into how aircraft seals are qualified for FAA approval and what that rigor looks like in practice. This includes the early analysis, documentation, and quality system alignment required long before formal review begins.

This post marks the starting point. In the next installment, we'll examine how performance requirements are defined and validated as part of the reverse-engineering process, and how those efforts support eventual FAA review. By the end of this series, you'll understand not just what PMA means on paper, but what it requires in practice — and what to look for when evaluating PMA suppliers for your programs.

About this series

Ergoseal is documenting our FAA PMA process in real time. This three-part series provides aerospace engineers, MROs, and program managers with practical insight into what it takes to qualify a replacement aircraft seal for FAA approval — and why that level of rigor matters to program reliability and supply chain resilience.