Building Variations of Old Airplane Designs: Legal and Practical Considerations

Airplane enthusiasts often find themselves captivated by vintage aircraft designs, leading them to question whether they can recreate these classics or derive new designs from them. This article explores the legal and practical aspects of building variations of old airplane designs, highlighting key considerations and potential challenges.

Legal Considerations: Permissions and Ownership

Can you legally build a variation on an old airplane design from a defunct company? The answer largely depends on the intellectual property (IP) rights and the current ownership of any relevant designs or patents. If the company's assets have been sold to another aviation company or if the design has been abandoned, you may have the freedom to create your variation. However, due diligence is crucial.

Due Diligence

To determine the legal status of the design rights, conduct thorough research. This includes:

Identifying any companies that might have acquired the assets or design rights of the defunct company. Checking for existing intellectual property (IP) filings, such as patents or trademarks. Verifying if the design has been abandoned or is in the public domain.

Engaging with industry associations, such as the Experimental Aircraft Association (EAA), might provide valuable insights into the current ownership of specific designs.

Practical Considerations: FAA Approval and Safety Standards

Building and flying a variation of an old airplane design requires proper certification and compliance with aviation safety standards. Here are the key steps and considerations:

FAA Airworthiness Certificate

If you wish to fly a variation of an old design for any commercial or public use, you will need to obtain an airworthiness certificate. This involves:

Preparing a comprehensive engineering report to demonstrate that the design meets all regulatory requirements. Securing the sign-off of a certifying aeronautical engineer to validate the safety and integrity of your design. Submitting your design to the nearest FAA Flight Standards District Office (FSDO) for review.

Design and Engineering

To design a safe and compliant variation, consider the following:

Utilize modern materials and construction techniques to improve performance and longevity. Ensure your design incorporates the latest advances in aeronautical engineering. Create a unique design that minimizes dependencies on the original plan to avoid licensing issues.

For instance, the Denney Kitfox is a spectacular example of modernizing a classic design, employing advanced materials and construction methods while maintaining a recognizable form.

Examples of Successful Derivation

Let's explore a couple of examples that illustrate successful design derivations:

The Fieseler Storch and Slepcev Storch

The Fieseler Storch is one of the most famous WWII light planes, known for its STOL (Short Takeoff and Landing) capabilities. The Slepcev Storch, though inspired by the Fieseler, is a unique design with distinct differences, such as different wing shapes and construction details.

If you wish to upscale a scaled-down version of the Slepcev Storch to a full-size aircraft, it can be considered a new design requiring a fresh engineering report and certification.

Pilatus PC-9 and Custom Paper Model

The Pilatus PC-9 is a military trainer with well-publicized plans and construction details. However, even with these resources, one can design a high-performance profile-scale paper model that is distinctly derived from the PC-9.

This custom design not only looks like a PC-9 but performs excellently in both scale and full-size manifestations. Similarly, a full-sized homage to the PC-9 exists in the form of the Kai KT-1 Woongbi, a Korean-designed Turboprop military trainer with optimally engineered wings and empennage.

Conclusion

Building variations of old airplane designs can be a rewarding endeavor, provided you understand the legal and practical ramifications. With the right approach, you can innovate and create unique aircraft designs that comply with safety standards and regulations.