Last updated: October 2026
In aerospace, the integrity of every component matters. Parts are costly to produce, and many flaws that affect performance sit inside a part, out of sight. Manufacturers and maintenance teams rely on non-destructive testing (NDT) to check parts without damaging them.
X-ray imaging is one of the main NDT methods for looking inside a part, and micro-CT (micro-computed tomography) builds on it to create detailed 3D views of small parts and samples. This article explains how NDT is used in aerospace, what X-ray inspection can and cannot find, and when 2D dual-energy radiography or 3D micro-CT may fit best. It closes with how KA Imaging’s spectral X-ray detectors and 3D X-ray microscopes are designed to work alongside other established methods.
Importance of Quality Testing and NDT in Aerospace Industry
Safety comes first in aerospace, and NDT is central to it. Components can develop flaws that are not visible from the outside, and NDT helps confirm the integrity of aircraft, spacecraft, and their parts.
Destructive testing still has a role in qualifying materials and designs, but it destroys the sample. NDT lets teams check a component, such as an aircraft’s elevator, and keep it in use if it passes.
NDT is used throughout a part’s life:
- During manufacturing, to check materials, castings, welds, bonded joints, composite layups, and finished parts.
- During scheduled maintenance, to look for fatigue cracks, corrosion, wear, and impact damage.
- After repairs and unexpected events, such as hard landings, lightning strikes, or bird strikes.
Manufacturing inspections often use fixed or automated equipment in controlled settings. Maintenance inspections often use portable equipment on the aircraft, in hangars and tight spaces.
Standards, Procedures, and Qualified Inspectors
Engineering specifications and maintenance manuals usually define the method, the procedure, the inspection interval, and which flaw sizes are acceptable.
Aerospace NDT personnel are typically certified under NAS 410 in North America or EN 4179 in Europe, two harmonized documents. EN 4179 was most recently revised in 2026. Level 1 inspectors work under supervision, Level 2 inspectors make accept or reject decisions, and Level 3 personnel approve procedures and act as the technical authority. Many suppliers also hold Nadcap accreditation for NDT, an industry program run by the Performance Review Institute (PRI).
Method standards apply too. ASTM E2698 covers radiography with digital detector arrays (flat-panel detectors), and ASTM E2533 guides NDT method selection for aerospace polymer matrix composites. These standards control how an inspection is done. They do not replace the acceptance criteria in a part’s specifications.
Testing Methods in Aerospace NDT
Many NDT methods are used in aerospace. No single method finds every flaw in every material, so inspection plans often combine several. Common methods include:
- Visual Testing (VT): The most widely used method. Inspectors look for surface cracks, corrosion, dents, and deformation, using magnifiers or borescopes to reach areas such as engine interiors.
- Ultrasonic Testing (UT): Ultrasonic Testing sends high-frequency sound waves, well above the range of human hearing, into a part. Cracks, voids, delaminations, and disbonds reflect or weaken the sound, and the instrument records these echoes. UT is used on metals and is one of the main methods for inspecting composite structures and bonded joints.
- Eddy Current Testing (ET): Eddy Current Testing uses electromagnetic fields to find surface and near-surface cracks and corrosion in conductive materials such as aluminum. It is common in maintenance, for example around fastener holes.
- Magnetic Particle Inspection (MPI): Magnetic Particle Inspection works only on ferromagnetic materials, such as many steels. The part is magnetized, and fine magnetic particles gather where a crack at or just below the surface disturbs the magnetic field. In aerospace, it is used on some steel landing gear and engine parts. It cannot be used on aluminum, titanium, or composites.
- Fluorescent Penetrant Inspection (FPI): Fluorescent Penetrant Inspection finds flaws that break the surface of non-porous materials, such as aluminum, titanium, and nickel alloys. A low-viscosity fluorescent dye seeps into surface openings, and a developer draws it back out so flaws glow under ultraviolet light. It cannot find flaws that are fully below the surface.
- Radiographic Testing (RT): Radiographic Testing is what KA Imaging specializes in. RT uses X-rays or gamma rays to create an image of the inside of a part. Thicker or denser areas absorb more radiation, and these differences form the image that trained inspectors examine for internal flaws. It is similar in practice to medical radiography, but it examines parts and materials. Computed tomography (CT) is a 3D form of RT.
Thermography, shearography, and acoustic emission testing are also used, especially on composites.
What X-ray Inspection Can Find in Aerospace Components
X-ray imaging shows how much radiation passes through each area of an object. That makes it well suited to some flaws and less suited to others.
Flaws X-ray Imaging Can Reveal
X-ray imaging is best at finding volumetric flaws, which take up space inside a part. Examples include:
- Porosity and gas voids in castings, welds, and composite laminates
- Inclusions, or pieces of foreign material trapped inside a part
- Shrinkage cavities that form as castings cool
- Lack of fusion in welds
- Missing, shifted, or damaged internal features in assemblies
- Trapped water and core damage in honeycomb sandwich panels
Aerospace Components Commonly Inspected with X-ray
Radiography is used across many types of aerospace parts, including:
- Cast engine and structural parts
- Turbine blades with internal cooling passages
- Welded and brazed assemblies
- Metal parts made by additive manufacturing (3D printing)
- Composite and honeycomb structures
- Electronic assemblies used in avionics
Film, Computed, and Digital Radiography
Aerospace radiography captures images in three main ways:
- Film offers fine detail and a long track record, and it needs chemical processing.
- Computed radiography (CR) uses reusable imaging plates that are scanned after exposure. Flexible plates can bend around curved parts.
- Digital radiography (DR) uses flat-panel detectors, also called digital detector arrays, that produce an image within seconds.
All three remain in use. The choice depends on the part, the specification, the inspection site, and what a facility has qualified. In each case, image quality indicators (IQIs) help confirm that an image meets the required sensitivity.
Where X-ray Inspection Has Limits
Thin, flat flaws such as delaminations and tight cracks can be hard to see on a radiograph unless the beam runs nearly parallel to them. In carbon fiber composites, fibers and resin absorb X-rays in similar ways, which can limit contrast. This is one reason UT remains a main method for delaminations and disbonds in composites, and why X-ray and UT results are often used together.
A radiograph is also a 2D image. Everything along the beam’s path overlaps in one grayscale picture, which can hide flaws behind denser structures. CT and spectral imaging are two different ways to address that overlap.
What is Micro-CT Radiographic Non-Destructive Testing?
Micro-CT, or micro-computed tomography, produces high-resolution, three-dimensional images of an object’s internal structure without cutting it open. It works on the same principle as medical CT but at a much finer scale, often resolving features measured in micrometers. It is used in research, materials science, geology, and industrial NDT.
In most laboratory micro-CT systems, the object rotates while hundreds or thousands of X-ray images are taken. Software reconstructs them into a 3D volume that inspectors can slice in any direction and measure.
In aerospace, micro-CT is often used to:
- Measure porosity and void content in composite samples
- Check fiber orientation, ply layup, and resin distribution
- Find pores, lack of fusion, and trapped powder in additively manufactured parts and test coupons
- Compare printed or machined geometry with the design
- Support failure analysis and process development, often alongside surface methods (see SEM vs. micro-CT)
Micro-CT and Industrial CT for Full-Size Parts
Micro-CT is built for small objects. Higher resolution generally requires more magnification, and more magnification means a smaller sample. Laboratory micro-CT is typically used for material samples, test coupons, and small parts.
Full-size components, such as large castings or composite panels, usually call for larger industrial CT systems with higher-energy sources, or for 2D radiography. Many aerospace programs use both: large-format CT or radiography for production parts, and micro-CT for material studies, qualification work, and failure analysis.
What is SpectralDR Technology for Non-Destructive Testing?
SpectralDR® is KA Imaging’s patented technology for single-exposure dual-energy X-ray imaging. It adds information to a standard 2D radiograph without a second exposure.
Dual-energy imaging works because materials absorb low-energy and high-energy X-rays differently. Absorption depends on a material’s thickness, density, and elements. At lower energies, heavier elements, such as those in most metals, absorb much more strongly than lighter materials such as polymers and carbon fiber composites. At higher energies, the gap shrinks. This comes mainly from photoelectric absorption, which depends strongly on atomic number. Comparing lower- and higher-energy information lets software emphasize one group of materials and reduce another. This is called dual-energy subtraction.
Many dual-energy systems take two exposures at different tube voltages. If anything moves between them, the images may not line up, causing motion artifacts. SpectralDR captures both energy ranges in one exposure, so there is no time gap.
Spectral imaging adds a layer of information. It can help inspectors separate overlapping materials and read structures that are unclear in one grayscale image. It does not automatically identify a material, and results still need to be read against the part’s specifications and other inspection data. For examples, see 5 applications of effective atomic number differentiation.
Triple Stacked Layer Design
SpectralDR is made possible by a triple-layer detector design. The X-ray beam passes through three stacked detector layers, and each one responds to a different part of the energy spectrum reaching it. A peer-reviewed paper by KA Imaging researchers describes how this design produces three detector responses from one exposure.
The detector then produces three images at the same time:
- A conventional DR image, similar to a standard digital radiograph
- A high-density image, emphasizing materials that absorb X-rays strongly, such as metals
- A low-density image, emphasizing materials that absorb X-rays weakly, such as polymers, foams, and composites
These are sometimes called high-Z and low-Z images, after atomic number (Z). In aerospace, this may help where metal fasteners, fittings, or inserts overlap composite structures, or where an assembly mixes materials with very different absorption. For more detail, read SpectralDR technology explained.
Dual-Energy Radiography or Micro-CT: When Each Is Used
Dual-energy radiography and micro-CT answer different questions:
| Feature | Dual-energy radiography (2D) | Micro-CT (3D) |
|---|---|---|
| What it produces | A standard image plus high-density and low-density images from one exposure | A 3D volume built from many X-ray images taken as the object rotates |
| Object size | Full components and assemblies, within the detector's field of view | Small parts, material samples, and test coupons |
| Where it is used | Fixed setups, the shop floor, and portable or field inspections | Laboratories and quality labs |
| Well suited to | Separating overlapping materials and reviewing assemblies quickly | Measuring porosity, fiber architecture, and internal 3D features |
| Main trade-off | Shows depth as overlap, not as separate slices | Limits sample size, and scans take longer |
The two methods can work together. A team might review a full assembly with radiography, then study a flaw type in detail with micro-CT on a coupon. Both complement ultrasonic, eddy current, penetrant, and visual methods rather than replacing them.
What sets KA Imaging's NDT products apart
KA Imaging is an X-ray imaging technology company in Waterloo, Ontario, that develops spectral X-ray detectors and 3D X-ray microscopes. Three product groups are most relevant to aerospace inspection.
Reveal 35C and Reveal R 35C Detectors
Reveal™ 35C is a 14 x 17 inch (35 x 43 cm) flat-panel detector with SpectralDR® technology. From a single exposure, it produces conventional DR, high-density, and low-density images. KA designs it to work with existing X-ray generators and established radiographic techniques, in fixed and portable setups, and lists aerospace among its applications. KA reports a detective quantum efficiency (DQE) of up to 75%. DQE measures how efficiently a detector turns incoming X-rays into useful image signal.
Reveal™ R 35C brings the same imaging to a ruggedized detector, with an IP55-rated enclosure, a tripod quick-mount bracket, strap points, and a 136 kg distributed load rating. It is designed for work outside the lab, such as industrial maintenance and remote field sites.
Because all three images come from the same exposure, they line up with one another, and inspectors can review them side by side. Like any digital radiograph, they can be stored and reviewed later, which supports traceability.
These images of a titanium composite wing sample all come from a single exposure. Left: conventional DR image. Middle: low-density (low-Z) image, which emphasizes lighter materials. Right: high-density (high-Z) image, which emphasizes denser materials such as metal.
Reveal NDT Packages
For teams that want a complete setup, KA offers Reveal NDT packages that pair a Reveal 35C or Reveal R 35C detector with an X-ray source. KA lists aerospace, industrial inspection, electronics, security, and construction among the intended applications.
inCiTe and inCiTe 2.0 3D X-ray Microscopes
inCiTe™ is a benchtop micro-CT system, or 3D X-ray microscope, for small samples. It uses KA’s BrillianSe™ direct-conversion detector (amorphous selenium on CMOS, 8 µm pixels) and propagation-based phase contrast. Phase contrast picks up small shifts in the X-ray wave as it passes through a material, which can improve the visibility of edges and of low-density materials such as polymers, foams, and fibers. KA reports a spatial resolution of 11 µm at 0.5 MTF, a measure of the smallest features the system can distinguish. KA’s gallery includes a phase-contrast image of a Kevlar composite showing individual fibers and layering.
inCiTe™ 2.0 is a larger, configurable system. It can use either a BrillianSe or a Reveal detector, adds spectral imaging to phase contrast, supports a higher-energy source, and has room for larger samples and in situ stages such as tensile rigs. KA lists aerospace component inspection among its applications.
Learn more about KA’s industrial and research solutions or how phase contrast and spectral imaging are expanding micro-CT.
Supporting Aerospace NDT with KA Imaging
Aerospace inspection relies on many methods, each suited to different materials and flaws. X-ray imaging shows the inside of parts, micro-CT adds detailed 3D views of small samples, and single-exposure dual-energy imaging separates materials that overlap in a single grayscale image.
KA Imaging’s Reveal detectors and inCiTe 3D X-ray microscopes are designed to work alongside ultrasonic, eddy current, penetrant, visual, and other established methods. Any new technique still needs to be qualified under the applicable specifications before use on production hardware. Explore KA’s quality control and NDT applications, or contact KA Imaging to discuss a part or arrange a sample test.
Frequently Asked Questions
What types of X-ray inspection systems are used in aerospace?
Aerospace teams use shielded cabinet systems for smaller parts, walk-in bays or gantry systems with motion control for large parts, and portable X-ray sources with film, CR plates, or flat-panel detectors for work on the aircraft. CT systems range from laboratory micro-CT to large industrial scanners. The right setup depends on part size, material, the specification, and where the inspection happens.
Does X-ray inspection make aerospace parts radioactive?
No. X-rays at the energies used for industrial radiography and CT pass through the part and do not make it radioactive. The safety concern is exposure for people nearby, which is why X-ray inspection uses shielding, controlled areas, and trained operators.
Can portable X-ray detectors be used on aircraft in a hangar?
Yes. Portable X-ray sources and detectors are used for on-aircraft inspections during maintenance, especially where parts are hard to remove. The work must follow an approved procedure, use qualified personnel, and set up radiation safety controls, such as a restricted area around the exposure.
How long does a micro-CT scan take?
It varies. A quick overview scan of a small sample may take minutes, while a high-resolution scan can take several hours. Scan time depends on the sample’s size and density, the resolution needed, and the number of images collected.
Does dual-energy X-ray work on all-composite parts?
It can help, but results depend on the materials. Dual-energy imaging separates materials best when they absorb X-rays differently, such as metal fittings over a composite skin. Many composite and polymer materials absorb X-rays in similar ways, so the separation between them may be limited. A sample test is the most reliable way to judge the benefit for a specific part.