Reverse Engineering Obsolete and Undocumented Aerospace Parts
Reverse engineering turns a physical part with no usable drawing into a documented design: measured geometry, identified material and processes, a new drawing, and a qualification plan. For flight hardware the new design is only usable once the design authority approves it, which means the FAA for civil aircraft parts and the responsible engineering support activity for military parts. Aerospace Sourcing coordinates that work through qualified suppliers and keeps you in control of every approval.
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When reverse engineering is the right path
Reverse engineering is usually the last option, used when a part cannot be bought and no usable drawing exists. Before starting, check the cheaper routes on our obsolete aerospace parts page: remaining authorized stock, a released replacement, an independent source with testing, or a drawing held by the original manufacturer, the prime or the government.
It makes sense when:
- The original manufacturer is gone or no longer supports the part, and no one holding the data will license it
- The drawing exists but is incomplete, illegible, or does not match the parts that actually flew
- The part is simple enough that its function depends mostly on geometry and material, such as brackets, fittings, spacers, housings and many machined details
- The quantity needed, or the cost of a grounded system, justifies the engineering effort
It is much harder for parts whose performance depends on things a sample cannot show: proprietary heat treat or coatings, internal residual stress, tight process controls, or electronic designs with firmware.
Legal and data rights cautions
Before anyone measures a part, confirm you have the right to copy it and to use the resulting data. This is a legal question, and you should have counsel review it for your situation. The general issues are:
- Patents. A part, or a feature of it, may still be under patent even if the product is old.
- Trade secrets and contracts. Your purchase agreements, license agreements or NDAs with the original supplier may limit copying or using its data.
- Copyright in drawings and documents. Copying an existing drawing is a different act from measuring a part.
- Government data rights. On DoD contracts, the clause at DFARS 252.227-7013 sorts technical data into unlimited rights, government purpose rights and limited rights. Limited rights data generally may only be used inside the government, and outside release normally needs the owner's written permission.
- Export control. If the original part or its data is ITAR or EAR controlled, the drawing you create is controlled data too.
Write down who owns the new drawing, the measurement data and any test data before work starts, and put it in the purchase order. We do not give legal advice, so confirm that review is done before any sample goes out for measurement.
Have a part like this?Send it in under a minute. A person replies within 1 business day.The steps from sample to approved part
Reverse engineering follows a predictable sequence, and skipping the early steps is how bad copies get made.
- Gather everything known. Old drawings, parts lists, specs, maintenance manuals, failure history and the next higher assembly drawing all constrain the design.
- Get representative samples. More than one sample where possible, ideally from different lots, so wear and part-to-part variation can be told apart from design intent.
- Measure the geometry. CMM, scanning or CT, depending on the features.
- Identify the material and processes. Chemistry, hardness, microstructure, coatings and treatments.
- Establish design intent. Turn measured values into nominal dimensions and tolerances that make sense for the function and the mating parts.
- Produce the drawing and model. To your drawing standard, with material and process specs called out.
- Qualify. Inspection, testing and analysis that show the new part does the job of the old one.
- Get design authority approval. Nothing goes into flight hardware until the authority for that product approves it.
Measurement methods: CMM, scanning and CT
The method follows the features. Prismatic, toleranced features are measured by contact CMM, freeform surfaces are captured by scanning, and internal features that cannot be reached without cutting the part call for CT.
| Method | Best for | Limits |
|---|---|---|
| Coordinate measuring machine (CMM) | Holes, bores, planes, datums, positional relationships, threads with suitable probing | Slow on freeform surfaces, cannot reach internal passages |
| Structured light or laser scanning | Freeform and cast surfaces, overall shape, comparison of several samples | Shiny or dark surfaces may need coating, edge and small-hole detail is weaker than contact probing |
| Industrial X-ray CT | Internal passages, cavities, wall thickness, assemblies that cannot be taken apart, internal defects | Part size and density limit penetration, resolution falls as the part gets larger |
ASTM E1441, the standard guide for computed tomography, describes CT as producing volume images from many X-ray measurements taken at different angles, so internal features can be seen without cutting the part, on metallic and non-metallic parts alike. A worn sample measures as worn, so critical surfaces are often measured on several samples and the results compared. Our inspection and metrology guide explains CMM capability and decision rules in more depth.
Material identification
Material identification starts nondestructive and moves to destructive tests only if the samples allow it. The aim is to name a material specification, not just an alloy family, because the specification controls properties the chemistry alone does not.
- Positive material identification (PMI) by handheld X-ray fluorescence or optical emission spectroscopy gives alloy chemistry quickly. ASTM E1476, the guide for metals identification, grade verification and sorting, classes these spectrometric methods as quantitative.
- Indirect methods such as eddy current and thermoelectric sorting respond to properties shaped by chemistry and processing. E1476 classes them as qualitative.
- Laboratory chemistry on a cut sample resolves light elements and trace content that handheld units read poorly.
- Hardness and microstructure point to the temper or heat treat condition.
- Coating and finish analysis identifies plating, anodize, conversion coating or paint, and often their thickness.
For polymers, elastomers and composites, identification is harder and usually needs lab methods suited to the material. Where the evidence fits more than one specification, the drawing should name the one your engineering selects, with the reasoning recorded.
From measurements to a usable drawing
A measured part is not a design. The drawing has to state nominal dimensions and tolerances that reflect what the part must do, not just what one sample happened to measure.
Good practice when building the drawing:
- Round measured values to sensible nominals and check them against the mating parts and the next higher assembly
- Set tolerances from function and fit, and check that a normal qualified shop can hold them
- Call out material, temper and process specifications by number, not by description
- Flag every characteristic that was inferred rather than measured, so the qualification plan tests it
- Prepare the drawing to your ASME Y14 practices and give it your own drawing number, with a note tying it to the original part number it replaces
Once the drawing is released, making the part is ordinary build to print work, with first article inspection against the new drawing.
Qualification: showing the new part is equivalent
Qualification is the evidence that the new part does the job of the old one, and the design authority decides how much is enough. It usually combines several of these:
- First article inspection of the new parts against the new drawing
- Dimensional and material comparison against the original samples
- Fit checks in the next higher assembly
- Functional, environmental or life testing where the part's performance cannot be shown by inspection
- Engineering analysis, for example stress or thermal, where testing alone is not practical
Plan the qualification before the drawing is final, because the plan often shows which characteristics need more measurement or which samples need to be sacrificed for material testing.
Approval for civil aircraft parts: FAA PMA
A reverse engineered replacement part for a type certificated civil aircraft product is normally approved through FAA Parts Manufacturer Approval under 14 CFR part 21, subpart K. Under 14 CFR 21.303, the application includes design data and the test reports and computations needed to show the article meets the airworthiness requirements.
FAA guidance describes two main ways to show the design complies:
- Test and computation, which shows by test and analysis that the part meets the airworthiness requirements for the product it goes on
- Identicality, which shows the part is identical to the approved type design part. A licensing agreement from the design approval holder is one way to show identicality. Without a license, the applicant must supply data that verifies dimensions, materials, special processes, coatings and test and acceptance criteria.
FAA Order 8110.42D notes that identicality without access to the original design data is nearly impossible for sophisticated parts with proprietary processes or coatings, which is why reverse engineered PMA parts usually go the test and computation route. The applicant, not a sourcing service, holds the PMA.
Approval for military parts: the engineering support activity
For a military part, the government engineering support activity (ESA) for that item decides whether a reverse engineered design is acceptable. When DLA buys the part, a new source is normally added through a source approval request (SAR), and the ESA reviews the technical data package, data rights and item criticality.
DLA's published guidance says its Replenishment Parts Purchase or Borrow program can let prospective suppliers inspect, borrow or buy a government sample for reverse engineering, and that for alternate item SARs DLA obtains reverse engineering approval from the ESA before it evaluates the request. DLA also separates reverse engineering from reengineering: creating an alternative design goes through the engineering change process instead.
If you are a prime or subcontractor rather than DLA, the approval runs through your contract: your customer's engineering, and the government where the contract requires it. Ask early who the approving authority is, because it shapes the qualification plan.
What drives the effort and schedule
The engineering and qualification work, not the manufacturing, usually drives the cost and time of a reverse engineering job. The main drivers are:
- Geometry complexity: internal passages, freeform surfaces and tight positional relationships need more measurement time and often CT
- Number and condition of samples: worn or damaged samples need more analysis to recover design intent
- Material and process uncertainty: unknown heat treat, coatings or surface treatments add lab work
- Criticality: a structural or flight critical part needs far more qualification evidence than a ground support bracket
- The approval path: an FAA PMA or a military source approval sets its own evidence requirements and review time
Our obsolete parts cost page covers how these drivers compare with buying remaining stock or testing parts from independent sources.
How Aerospace Sourcing handles reverse engineering
We are a sourcing service. We do not do the engineering ourselves and we do not hold design approvals. We coordinate qualified suppliers for each step and keep you, and your design authority, in control of the decisions.
- One quote, one point of contact and one purchase order across measurement, material analysis, drawing preparation and manufacture
- Data rights, ownership and export control requirements written into every supplier order, with flow-down NDAs before any supplier sees samples or data
- Every design intent question sent to your engineering in writing
- Inspection, lab and FAI reports checked before parts ship, with a certificate of conformance and the reports your request requires
Controlled samples and data move by secure transfer to US persons only. See our controlled programs page and confidentiality page. For buying risks on the parts you can still find, see our counterfeit parts avoidance page.
Start a reverse engineering request
Use the obsolete and reverse engineering request form to describe the part, the system it goes into, what documentation exists, how many samples you have, the quantity you need and who the design authority is. Telling us the approval path up front lets the measurement and test work be scoped to what that authority will actually accept. A person replies within one business day. Do not upload controlled data through the form.
Send the job. A person replies within 1 business day.
Part, quantity and date are enough to start. Drawings and the mutual NDA follow by reply, and controlled programs never send technical data through this site.
We have it.
Reference . A person replies within 1 business day. Watch for our email from [email protected].
Questions
Is it legal to reverse engineer an aerospace part?
It depends on the part and your agreements. Patents, trade secrets, contract and license terms, copyright in existing drawings, and government data rights can all limit copying a part or using the resulting data. Export control applies to the new data if the original was controlled. Have counsel review your specific situation before work starts, and record who owns the new drawing and data in the purchase order.
Can a reverse engineered part go on a certificated aircraft?
Only with an approval. For civil aircraft, a replacement part is normally approved through FAA Parts Manufacturer Approval under 14 CFR part 21, subpart K. Reverse engineered parts usually show compliance by test and computation, because FAA guidance says identicality without the original design data is nearly impossible for sophisticated parts. The applicant holds the PMA and is responsible for the design and production approval.
Who approves a reverse engineered military part?
The engineering support activity responsible for the item, through the buying activity's process. For parts DLA buys, a new source is usually added with a source approval request, and DLA states it obtains reverse engineering approval from the engineering support activity for alternate item requests. On prime or subcontract work, approval runs through your contract and your customer's engineering.
Which measurement method should be used, CMM, scanning or CT?
Whichever fits the features, and often more than one. A CMM measures toleranced prismatic features such as holes, bores and datums most accurately. Structured light or laser scanning captures freeform and cast surfaces quickly. Industrial CT shows internal passages, cavities and wall thickness without cutting the part. Measuring several samples helps separate wear and variation from the original design intent.
How is the material of an old part identified?
Usually by positive material identification with XRF or optical emission spectroscopy first, then laboratory chemistry, hardness testing and microstructure if a sample can be cut. Coating and finish analysis identifies plating, anodize or paint. The goal is to name a material specification and condition on the new drawing, because the specification controls properties that chemistry alone does not show.
How many samples do I need?
As many as you can spare, and at least one you can afford to cut if the material and heat treat must be confirmed. Several samples, ideally from different lots, let measured variation and wear be told apart from design intent. If you only have one sample and it must go back into service, say so, because it limits material testing to nondestructive methods.
Related
Sources
- Cornell LII: 14 CFR 21.303 Application (Parts Manufacturer Approval)
- FAA: Order 8110.42D Parts Manufacturer Approval Procedures
- FAA: 2019 PMA 101 Workshop
- Acquisition.gov: DFARS 252.227-7013 Rights in Technical Data
- DLA Aviation: Source approval briefing
- DLA Land and Maritime: Source approval request briefing
- NDIA/DTIC: DLA SAR and RPPOB breakout
- ASTM E1476 Standard Guide for Metals Identification, Grade Verification, and Sorting
- ASTM E1441 Standard Guide for Computed Tomography (CT)
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