Why aircraft engine borescope inspections are critical to aviation safety
High-bypass turbofan engines for commercial aircraft are some of the world’s most valuable and critical business assets, not just for aviation safety but also for the global economy as a whole.
Millions of passengers and businesses rely on them every day for safe and fast air travel, as well as air freight. Governments, heads of state and air forces around the world depend on serviceable jet engines for national security, emergency response and international co-operation. Quite literally, engines help the world go round.
Given the high operational stresses and extreme environmental conditions that aero engines endure, routine maintenance and inspections are paramount to ensuring safety, efficiency, and longevity. One of the most effective and non-invasive methods of inspecting an aircraft engine is the utilisation of a borescope.
Aircraft engine borescope inspections are a crucial part of preventive maintenance in the aviation industry. This technique allows inspectors to look inside the core of the engine and visually inspect the interior components, without the need for its disassembly, thereby saving time and huge costs, whilst still ensuring the engine is in a serviceable condition.
This article explores the borescope inspection process in greater depth, its importance in aviation safety, and how it helps in maintaining optimal engine performance.
What is a borescope inspection?
A borescope inspection is a non-destructive testing (NDT) method that allows inspectors to examine the internal components of an aircraft engine without disassembling it. A borescope is a flexible or rigid optical device equipped with a high-resolution camera and light source, enabling a detailed inspection of critical areas such as turbine blades, compressor sections, and combustion chambers. The real-time imagery captured by the borescope is displayed on a monitor, providing a highly detailed view of the engine's condition.
A borescope also allows inspectors to measure wear of components, including length, width and depth, to check that they are within safe operating parameters. If not, then these parts will require replacement.
The borescope inspection process
A borescope inspection involves several steps to ensure a thorough and accurate assessment:
- Preparation
Before starting the inspection, inspectors must review the aircraft's maintenance records and the engine manufacturer’s guidelines to determine inspection points and required procedures. They must also ensure that the borescope equipment is calibrated and functioning correctly.
Before beginning the inspection, it's essential to ensure the aircraft engine is completely cold. This prevents potential safety hazards and allows for a more thorough examination. The inspector(s) must gather all necessary equipment, including the borescope, protective gear, and any additional tools required for the procedure.
- Accessing the engine
Access panels, ports, or designated borescope entry points on the engine are carefully opened. This step requires precision to prevent damage to surrounding components.
The next step involves gaining access to the engine's interior. This may require removing access panels to expose the areas that need inspection. Inspectors must follow all safety protocols and guidelines during this process to avoid any risk of damage.
- Insertion of the borescope
The borescope probe is carefully inserted into the engine, manoeuvring through tight spaces to reach critical inspection areas. Advanced borescope models come with articulating tips, to control the direction and focus on specific areas of interest.
Once access is gained, the borescope is set up for the inspection. The device consists of a long, flexible tube with a high-resolution camera at one end and a light source at the other. The camera is connected to a monitor, allowing the inspector to view a live video feed of the engine's interior. Depending on the engine's design, different types of borescopes may be used, such as articulating borescopes, for navigating through intricate components.
- Inspection and data collection
High-resolution images and video of the engine's internal components are captured. Inspectors look for signs of wear, cracks, corrosion, foreign object damage (FOD), and other irregularities that could indicate potential issues.
The actual inspection involves carefully manoeuvring the borescope through various engine components, such as the turbine blades, fuel nozzles, combustion chambers compressor blades and cylinder walls and valves (for piston engines).
For more detailed examinations, inspectors may employ specialized techniques. For instance, when inspecting turbine blades, the borescope is often fixed in position while the turbine is slowly rotated. This method allows for efficient inspection of each blade. Some advanced systems even incorporate digital turning tools to automate the rotor shaft positioning process, further increasing efficiency.
In cases where access is extremely limited, such as in narrow cooling channels inside turbine blades or aircraft gearbox housings, ultra-thin video borescopes with an outer diameter of about 2mm may be used. These specialized tools allow for inspection of areas that would be inaccessible with standard borescopes.
Once the process is complete, the borescope is removed and all access panels are securely closed and checked off.
- Analysis and documentation
The collected data is analyzed to assess the severity of any identified issues. If necessary, additional inspections or corrective actions, such as part replacements or further maintenance, are recommended.
The mandatory documentation in the aircraft’s maintenance record serves as a valuable reference for future inspections and aids in making informed maintenance decisions.
Importance of Borescope Inspections in Aircraft Safety
Borescope inspections play a critical role in maintaining aircraft safety and reliability. Their significance extends to several key areas:
Early detection of issues: By providing a detailed internal view, borescope inspections help identify potential problems before they escalate. Detecting cracks, thermal damage, or debris build-up early can prevent catastrophic engine malfunctions. Borescope use allows for more frequent inspections, contributing to better trend monitoring and condition-based maintenance strategies.
Cost savings and reduced downtime: Traditional engine inspections require significant disassembly, leading to higher maintenance costs and aircraft downtime. Borescope inspections minimize the need for extensive dismantling, reducing labour hours and operational disruption.
Regulatory compliance: Aviation authorities, such as the Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA), mandate periodic engine inspections. Borescope inspections help ensure compliance with these regulations, keeping aircraft airworthy and safe for operation.
Engine efficiency and performance: Routine inspections enable monitoring of the condition of engine components and the recommendation of timely maintenance. A well-maintained engine operates more efficiently, consuming less fuel and reducing overall operational costs.
Improved safety and risk mitigation: Aircraft engine failures can have severe consequences, including in-flight shutdowns or emergency landings. Regular borescope inspections significantly reduce the likelihood of such events by proactively identifying potential hazards.
Aircraft engine borescope inspections are, therefore, an indispensable tool in aviation maintenance, providing detailed insights into the health of an engine without the need for extensive disassembly. By enabling early issue detection, ensuring regulatory compliance, and maintaining peak engine performance, borescope inspections play a crucial role in aviation safety. Airlines and MRO providers that prioritize these inspections not only enhance the reliability of their fleets but also contribute to the overall safety of air travel. As technology continues to evolve, advancements in borescope inspection techniques using AI will further improve efficiency and precision, making aircraft maintenance safer and more effective than ever before.
In its role as a Continuing Airworthiness Management Organisation (CAMO), Air Worthy manages responsibility for all continuing airworthiness activities, such as forecasting and compliance of the maintenance programme, Airworthiness Directive compliance, Service Bulletin evaluation and implementation, test flights, defect rectification and the safekeeping of accurate aircraft records. This includes witnessing aircraft engine borescope inspections.
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