Owner Produced (DIY) Parts for Certificated Aircraft
Presenter: Mike Bush, President of Savvy Aviation Incorporated, FAA Aviation Maintenance Technician of the Year (2008), Certified Flight Instructor, A&P Mechanic with Inspection Authorization (IA) privileges.
Core Concepts and Key Insights
Context and Problem:
- The aviation fleet is aging, with many aircraft 40–50 years old or older.
- Many parts are hard to find, absurdly expensive, or no longer available due to manufacturers going out of business or low demand.
- "Unobtanium" is the joking term used for these elusive, unavailable parts.
- High costs often stem from product liability insurance and low production volumes.
FAA Regulation on Owner Produced Parts:
- The FAA allows owners of certificated aircraft to produce parts for their own aircraft only. These parts cannot be sold or used on other owners' aircraft.
- This is not a loophole but a necessary lifeline to keep older aircraft flying when original parts are inaccessible.
- Regulations do not explicitly define owner produced parts, but a key legal interpretation known as the "Byrne Interpretation" clarifies the rules.
Byrne Interpretation – Defining Owner Produced Parts:
Owners don't have to personally fabricate parts; they must, however, participate meaningfully in the production process in at least one of five ways:
| No. | Method of Meaningful Owner Participation | Description |
| 1 | Provide specifications | Often involves reverse engineering if original specs unavailable. |
| 2 | Provide the raw materials | Owner supplies the material used for the part. |
| 3 | Specify fabrication methods | E.g., CNC machining, 3D printing, or other specific processes. |
| 4 | Conduct quality assurance (QA) | Owner oversees the quality and conformity checks. |
| 5 | Supervise the manufacturing | Owner supervises the production, without necessarily doing the work. |
Options for Obtaining Hard-to-Find Parts:
- Buy from Manufacturer or PMA (Parts Manufacturer Approval) Supplier: Preferred if available and reasonably priced.
- Salvage Yard Parts:
- Highly recommended for "nonwear" parts (e.g., wing ribs, fairings, wheel halves), which do not wear out but may need cleaning or corrosion treatment.
- Salvage yard parts typically cost about half or less of new parts.
- They are sold "on approval"—inspect and return if not satisfactory, usually with no restocking charge.
- Wear parts (e.g., bearings, pumps) are generally not good candidates due to unpredictable wear.
- Owner Produced Parts: Used when parts are unavailable, prohibitively expensive, or have long lead times.
Minor vs. Major Repairs:
- Owner produced parts are usually suitable for minor repairs, which require acceptable data, a standard that does not require FAA or DER (Designated Engineering Representative) signature.
- Major repairs and alterations require approved data—data signed off by FAA or a DER. This often means hiring a DER for reverse engineering, which can be costly and complex.
- Examples:
- Minor repair: Replace a cracked nonstructural bracket or a battery box.
- Major repair: Fabrication of a wing spar or structural flight control component.
Mechanic Produced Parts:
- The FAA expanded rules to allow mechanics to produce parts under two conditions:
- The parts must be consumed in the repair (not stockpiled or sold).
- The mechanic must have a quality system in place (recordkeeping, calibration, etc.), though this is loosely defined.
- Mechanics can either produce the part themselves or collaborate with the owner during owner produced part fabrication.
Documentation:
- Proper documentation is critical to defend the legitimacy of owner produced parts during inspections.
- Recommended procedure:
- Owner logbook entry: Describes how the owner participated (referencing one of the five Byrne methods) and certifies the part is equal or better than the original per regulatory requirements (e.g., 14 CFR Part 43.13).
- Mechanic logbook entry: Documents installation and acceptance of the part.
- Lack of documentation can lead to parts being classified as Suspected Unapproved Parts (SUPs) during inspections.
Ownership Transfer:
Owner produced parts remain valid on the aircraft if ownership changes—removal is not required.
Summary of Regulatory and Technical Details
| Topic | Details |
| Regulation Citation | 14 CFR Part 21.9 (owner produced parts), 14 CFR Part 43.13 (repair standards) |
| FAA's Definition Source | The "Byrne Interpretation" (a legal opinion, not in the regulations themselves) |
| Owner Produced Parts Allowed For | Owner's own certificated aircraft only, non-commercial, non-sale parts |
| Approved vs. Acceptable Data | Major repairs/alterations require approved data (FAA or DER sign-off) |
| Quality System for Mechanics | Loosely defined; includes recordkeeping, calibration, procedures documented |
| Salvage Yard Parts Ideal For | Nonwear parts: structural items, panels, fairings, wheel halves, etc. |
| Salvage Yard Parts Not Ideal For | Wear parts: bearings, pumps, alternators, items with service life or wear limitations |
Highlights from Q&A Session
- Co-Ownership: Either or both owners may produce a part.
- Use in Minor Alterations: Owner produced parts can be used for minor alterations; major ones require approved data.
- Cost Justification: Owner produced parts can be legally made even if OEM parts are available but unaffordable.
- Reverse Engineering: Not sufficient as approved data for major repairs without DER involvement.
- STC (Supplemental Type Certificate): Never required for owner produced parts; major alterations may require field approvals or DER input.
- Improving Parts: Parts must meet form, fit, and function and be at least equal to original; improvements are considered alterations.
- Missing Documentation: Undocumented owner produced parts are a liability and may be treated as unapproved.
- Sharing Plans: Sharing production methods is possible but does not provide legal approval for others to produce the part.
- Type Clubs Producing Parts: Not allowed; only the individual owner can produce owner produced parts.
Closing Remarks and Additional Resources
- Mike Bush offers a monthly newsletter, podcasts, and ongoing webinars for aircraft maintenance topics.
- Upcoming webinars cover topics like supply chain issues from ADs, history of O-ring materials, and cylinder compression troubleshooting.
In conclusion, the presentation emphatically underscores that owner produced parts are an essential, FAA-recognized solution to maintainability of aging aircraft, provided that owners meaningfully participate in their production and carefully document their work. Salvage yards remain a valuable source of affordable parts, and collaboration with a qualified mechanic is highly recommended to ensure airworthiness and regulatory compliance.
