Remote Visual Inspection in MRO
Deeper Insights on Multiple Levels
In aviation remote visual inspection (RVI) is a non‑destructive inspection method in aircraft maintenance that uses camera‑based tools to examine engines and various aircraft parts and structures. It enables maintenance personnel to assess internal or inaccessible areas and components quickly and safely. With recent improvements it also enables a higher quality of documentation.
Over the last decade RVI has evolved in a variety of ways. Firstly, it is moving on from the mere approach of looking and documenting findings towards enabling a more measuring-based, analytic and predictive approach to maintenance. In parallel, AI is becoming an essential element in RVI.
Over the last years there were also significant changes to the human element in the MRO process, increasing the need for better RVI technologies. The loss of the experience and tribal knowledge of the boomer generation will need to be replaced and/or bettered. At the same time an increased focus on the consequences of human errors in MRO requires a different approach to documentation discipline, evidence collection, and comparability.
Market developments
For engine maintenance in particular, the growth in demand is driven by the increase in the global aircraft fleet and related engine shop visits. Furthermore, the pressure on aircraft MRO turnaround times, general MRO capacity constraints, as well as increasing requirements from regulatory authorities for safety, traceability, and the better quantifiability of aircraft and engine inspections increases the demands on the industry.
In response to pressures from severe shop capacity constraints and material shortages there is also a trend towards the wider use of an MRE (Maintenance, Repair & Exchange) model. MRE is an evolution of the classic MRO model, but working on the module level, i.e. targeted module swaps and exchange pools, rather than traditional full engine overhauls. It offers a faster and modular alternative and enables the operator to keep engines longer on wings. By also using more Used Serviceable Materials (USM) in the process and offering more Mobile Engine Services (MES) to perform on-wing or near-wing inspections -obviously the natural habitat for more sophisticated RVI technologies- the industry tries to mitigate the above-mentioned risks.
The Evolution of Aircraft Engine Maintenance
Engine maintenance was the first area of the MRO world in which RVI was applied consistently. Engines are the most expensive subsystems of the aircraft and most important for the operation.
Driven by fleet growth and capacity constraints from various factors, RVI technology applied to engines is also the fastest moving segment. This includes the integration of digital workflows that use cloud computing and enable records to be linked to serial numbers.
RVI is literally and metaphorically at the core of aircraft engine maintenance because it enables the inspection of internal components such as compressors, turbines or bearings without disassembling the engine. That results in faster turnarounds for each engine, thus lower costs, higher engine availability and less risk of damage induced during teardown. Overall, RVI is shifting from a diagnostic tool that offers a snapshot of the engine status to becoming a source of data for predictive maintenance. In addition, the emergence of digital twins does not only help to avoid the disassembly of engines, but the creation of a complete digital replica of the engine enables much improved analysis and context information.
At the same time the trend towards MRE (Maintenance, Repair, exchange) for engines is becoming more mainstream.
Aircraft Engine Evolution as the Baseline for the RVI Development
The evolution of jet engines from their beginnings is well known to us all. The developments towards the latest generation of commercial turbofan engines (LEAP, GTF, Trent XWB, GE9X..) affected in particular three areas.
Engine Architecture and Geometry
The emergence of the geared turbo fan as an evolution of the direct-drive engine is the most significant development. It changed the engine architecture substantially by introducing a highly complex planetary gearbox which contains a multitude of gears operating at very high speeds and therefore naturally susceptible to damage and wear and tear. In this engine architecture RVI is applied to the various engine modules that range from compressors and combustors via turbines to the mentioned gearbox to detect cracks, burn, FOD (Foreign Object Damage), loss of coating, and erosion.
Engine Materials
The materials used to build and coat components and subassemblies of engines have also evolved. From the increased use of composites to new coatings, the change in materials has an impact on its maintainability and the diagnostic processes or tools required to detect defects. A classic example are highly reflective materials that, with older camera and lighting technology, might prevent the borescope operator to see issues clearly.
Digitalisation of engine related data
The latest-generation engines generate far more data than previous generations. Due to expanded sensor suites and integrated health‑monitoring architectures typically more than 5,000 parameters are recorded and streamed per flight, thus enabling predictive maintenance and real‑time health monitoring.
Also, the digitisation of maintenance on engines has changed in terms of the types, amounts, and structure of data that are now available. Furthermore, the increased ability to access and validate older data has a major impact on the overall engine maintenance knowledge pool, provided these data are integrated into the bigger MRO data landscape.
The Evolution of Core Techniques in Engine Maintenance
Parallel to the evolution of the engines themselves, the technologies used in the maintenance of engines are evolving.
The main technologies in use today are:
Borescopes and videoscopes: There are a few different types in operation:
Rigid borescopes: These are the first-generation borescopes and are used where there is a straight-line access to parts of the engine like e.g. some combustor elements. Their lack of flexibility limited their applicability.
Flexible fibre borescopes: These second-generation devices offered more flexibility and enabled entering other parts of the engines via various curved paths. Whilst offering better manoeuvrability, the image quality still could be improved.
Video borescopes / videoscopes: These last-generation tools are standard in modern advanced engine MRO. They typically feature high‑resolution sensors, high degrees of articulation, and come with interchangeable tips with integrated lighting and inbuilt measuring (2D/3D) capabilities generating 3-dimensional measurements with the help of photogrammetry. That way the maintainer can establish immediately and more accurately the length of cracks, depth of pits, or any foreign object damage (FOD). The introduction of these devices resulted in a step change for quantitative defect sizing as well as the automatic recording of data and images.
Digital Transition driving further developments
Some of the most impactful and efficiency generating developments in MRO RVI technology can be found in the digital world.
AI‑powered visual inspections
With its capacity to handle vast amounts of data and the ability to recognise correlations and patterns far beyond what humans are able to see, AI can identify potential defects in real time. Its learning capability helps to quantify and classify defects (Assisted Defect Recognition – ADR). Things like burn marks, cracks, erosions, or loss of coating can be conclusively identified with far higher consistency than a human-only inspection could ever do. They immediately support the inspector in the decision on next steps or even give recommendations. As a result, there will be fewer missed defects as well as fewer unnecessary removals.
The AI-supported defect identification will also bring more decision consistency by eliminating operator variability between inspections by the same inspector, between different inspectors, and across several MRO entities. It will help inspectors to focus on the most relevant data a/o images. Some sources state that AI is cutting inspection time by 50–75%, thus resulting in much faster inspections, shorter ground times and improved fleet availability. Naturally these data feed also perfectly into the overall predictive maintenance landscape.
Overall, AI is not just analysing images, it is changing how images are captured and interpreted, resulting in substantially richer data, much more automated measurements, and less subjective judgements.
Cloud platforms as data backbone
The cloud-enabled centralized storage of reports, images, measurements, and their remote accessibility by different people enables fleet‑level predictive maintenance that results in insights which in turn will optimise shop visits and thus supports better long‑term fleet planning. This shift from managing individual inspection events to building a structured lifecycle record for each asset by serial number is the capability that will enable fleet-level predictive maintenance.
Digital workflows
Another important aspect of the evolution of RVI tools is how they address and guide inspection workflows. Traditional workflows typically have interruptions between steps. Digitisation, and a more standardised approach supports more consistency and continuity. It reduces the variability between inspections and inspectors whilst speeding up the overall process for repetitive engine inspections. Furthermore, the digitisation-driven much easier integration with maintenance management systems and digital twins enables the deeper and more immediate embedding of the RVI process into the wider MRO landscape. This is particularly relevant for the latest generation engines. They tend to be too complex for legacy RVI workflows, which is why new advanced RVI tools offer a range of features that optimise and integrate workflows (viewing, measuring, recording, changing probes etc.) and with that provide repeatable and quantifiable data for MRO decisions.
Naturally the benefits of the improved digital workflows are applicable to all parts of the aircraft where RVI is used, not just for engines.
Aircraft Maintenance Beyond Engines
As newer aircraft are becoming increasingly complex and most fleets are currently aging more than originally planned, RVI is becoming a universally applicable inspection method across the entire aircraft. As more aircraft are now flying beyond the 20 to 25-year horizon, the need for corrosion and structural inspections is inevitably growing. Also, regulatory pressures e.g. regarding EWIS requirements (Electrical Wiring Interconnection System) or the need for more focused corrosion prevention programs require more frequent visual checks.
The RVI technologies used outside engine maintenance are largely similar. Naturally videoscopes or borescopes are being used for any confined spaces. Similarly, articulating snake cameras are very useful in the inspection of wiring and ducts. In large structures like cargo bays or wings robotic crawlers -not yet used a lot in engines- can be used as well.
The aircraft sections where RVI is increasingly used are:
APU (Auxiliary Power Unit): The use here is naturally similar to engines.
Airframe structures: Particularly the inspection of fuselage cavities, wing boxes, cargo bays, spars, ribs, and stringers benefits from the use of RVI technology to detect corrosion, moisture ingress, cracking, or delamination.
Aircraft fluid systems (fuel, hydraulics, pneumatic): Similar to the airframe structures, tanks and fuel lines need inspections by RVI. It enables the inspection of internal tubes and reservoirs and is able to detect contamination, wear, foreign objects and microbial growths.
Landing gear: Considering the stresses the landing gear takes; the frequent inspection of the whole assembly is central in MRO. Internal bores of shock struts, actuators, or linkages need to be checked for corrosion, contamination or seal damage.
Environmental control systems: These systems are complex, large and, whilst not critical to the immediate operability of the aircraft, do have a big impact on the passenger experience. For example, ducts and heat exchangers need to be checked for blockages or contamination.
Wiring and avionics: Especially the detailed inspection of wiring bundles in tight spaces to identify chafing, insulation damage, or loose connectors benefit from RVI technology.
Key Industry Contributors
The market for high-end RVI solutions -whether for engines or other aircraft parts – is dominated by two companies. These are Evident (formerly Olympus Scientific Solutions), and Waygate Technologies (now part of Hexagon). There is also Karl Storz, a company that focusses on RVI endoscopy in a wide range of industries, as well as some regional specialists and several NDT and MRO integrators that bundle RVI hardware with inspection services and data.
EVIDENT
Evident is a major supplier of industrial borescopes and videoscopes that are widely used in aircraft MRO, esp. engines. Evident offers hardware, software, and services in a portfolio that includes guided inspection workflows to enable repeatable borescope paths, on‑device annotation and reporting, cloud connectivity for storing images and videos, measurement validation tools for regulatory compliance, and the integration with wider MRO record systems.
In the market Evident is particularly recognised for their family of IPLEX videoscopes which feature highly articulated probes with interchangeable diameters to be able to negotiate the tighter geometries of modern engines. They feature high‑resolution optics (Swoptix) for sharper imaging supported by bright, uniform LED illumination. Swoptix works in conjunction with MultiView, an application that lets the inspector switch between views (different sides, near/far) and enables 3D measurement for crack and corrosion sizing. In addition, an app named ViSOL helps to connect the inspection data into cloud storage, various analytics dashboards and ultimately into the bigger asset management workflow. ViSOL’s latest release introduces the Blueprint/Asset model that supports the overall shift from only managing individual inspection events to building a structured lifecycle record for each asset by serial number. This capability makes fleet-level predictive maintenance possible. Evident has clearly taken on the challenges of the next generation engines and used them as a catalyst to refocus their solution development efforts, having realised that a very big value lies in how these technologically optimised and much more capable tools on the frontline are embedded into the wider MRO landscape. To that effect they are focussing beyond the immediate inspection technology (smaller hardware, maximised optics and lighting (Swoptix)) on optimising in-engine workflows and on integrating documentation and AI-supported analytics processes.
Often Evident is perceived as the default choice for line maintenance teams because of their portability and reliability. However, their move from hardware-centric to software-platform thinking shows a strategic repositioning in the above-mentioned direction. This additional focus on post-inspection workflows will also reduce the need for further inspections in the future.
In an interview Evident addressed the opportunities more digitalised RVI processes offer also for training and skill development. Inasmuch as the digitally enhanced and optimised data from inspections enable more efficient workflows for the inspector on the engine, they can also create much more effective training material which should help to overcome the skill gap that boomers will be leaving behind.
Asked about future developments, Evident sees that even smaller, higher‑resolution probes that enable more advanced 3D measurements and AI‑assisted defect recognition will create even better RVI findings that will feed into a growing cloud‑native inspection ecosystem.
WAYGATE
Waygate Technologies (now Hexagon) is particularly strong in aerospace, power generation, and the oil & gas industry. Like Evident, Waygate is one of the two global leaders in industrial RVI and NDT in aviation MRO. Their key products are the Mentor Visual iQ videoscopes, the InspectionWorks suite of software for workflow management, as well as automated defect recognition, AI analytics, 3D measurements and the resulting data for MRO intelligence.
Through their focus on AI and cloud connectivity Waygate has also realised that the integration of guided workflows and process support functions like e.g. automated labeling to ensure consistent global MRO processes result in better data which in turn leads to fewer repeat inspections and more reliable maintenance decisions. By partnering with engine OEMs such as Rolls-Royce, Waygate is making sure to maximise the value from engine borescope inspections for the MRO.
Future Developments & Conclusions
The market for latest generation RVI solutions will be growing steadily. Within that engine MRO is the fastest moving segment, driven by fleet expansions, MRO capacity constraints, the need to reduce asset downtime and human risk, as well as the increasing demands from the regulatory side.
The following trends are likely to continue or emerge:
The high‑value segments of the market are clearly shifting towards a more integrated hardware‑plus‑software ecosystems.
RVI continues to move from a sporadic reactive diagnostic tool to become a more integrated element in the proactive predictive maintenance world.
The availability of ultra‑high‑resolution sensors and routine 3D measurement on most mid‑ to high‑end scopes will result in higher resolution imagery. Smaller and more manoeuvrable probes will cope with tighter, more complex engine architectures.
AI’s impact on the industry will grow exponentially by enabling much more robust automated defect classification (ADR) processes as well as more accurate severity scoring.
AI will help to develop pre‑programmed borescope paths and will be able to learn optimal routes through specific new engine models, resulting in improved repeatability and speed.
AI will result in on‑device inference for real‑time guidance and defect flagging during the inspection process.
There will be a much deeper digital integration into cloud‑native inspection ecosystems that host standardized templates and processes for automated report generation and supports multiple processes, incl. e.g. the remote sign‑off by OEMs or lessors.
The use of digital twins to assess situations and for training purposes will expand drastically, enabled by the links to RVI imagery and measurements.
UAV / drone-based inspections are maturing rapidly, especially for external surfaces. Similarly, robotics will become more relevant with e.g. robotic crawlers becoming more prevalent.
These technological trends and capabilities will result in better defect detection, more consistent inspections, much richer data for fleet‑level analytics, faster turnaround times, as well as more effective training for new technicians, thus mitigating the risks from labour shortages. All of this will ultimately result in lower lifecycle maintenance costs and higher aviation safety.
By Markus Gilges
