An aircraft’s structural elements and onboard systems are meticulously engineered to endure long service lives under great operational and environmental stress. However, design strength alone is not enough to guarantee longevity. The continued reliability of all components depends on consistent Maintenance, Repair, and Overhaul (MRO) practices, which we will explore further in this blog.
As we briefly touched on, MRO represents:
Together, these activities form a layered approach to safety and regulatory compliance.
Rather than delegating tasks during pre- and post- flight inspections or at random points, aviation authorities and manufacturers both mandate structured inspection cycles. The most common framework is A- through D-checks that each escalate in depth:
|
Check Type |
Approximate Interval |
Typical Focus |
Average Downtime |
|
A-Check |
Every 400–600 flight hours or 200–300 flight cycles |
Visual inspections, fluid servicing, lubrication, filter changes, and operational tests of emergency equipment |
~6–24 hours |
|
B-Check |
Every ~6–8 months or 600–800 flight hours |
Now mostly historic and combined with A-checks, involves deeper testing of things like avionics, hydraulics, and landing gear |
~1–3 days |
|
C-Check |
Every ~18–24 months or as designated by manufacturer |
Thorough structural and system inspection |
~1–4 weeks |
|
D-Check |
Every ~6–10 years |
Full disassembly and overhaul, removing paint, interiors, and systems |
Several weeks to months |
In addition to scheduled airframe checks, many components are subject to Time Between Overhaul (TBO) limits defined by manufacturers, which specify the maximum operational life before overhaul is mandatory. Many TBO-related inspections coincide with C-Checks or D-Checks, but more imperative components like engines or gearboxes tend to be addressed independently. Through observing TBO guidelines, operators can restore parts at the appropriate time before they reach fatigue thresholds, hopefully extending their years in service.
Engines are among the most maintenance-intensive components of an aircraft, as they are constantly exposed to extreme temperatures, pressures, and rotational forces. Between full overhauls, manufacturers often prescribe borescope inspections and hot section checks to detect for thermal damage, cracking, or material degradation before such issues compromise performance. Meanwhile, overhauls restore the engine to an airworthy condition, with particular attention paid to high-stress areas like turbine blades, bearings, and compressor sections.
Airframes and structural assemblies are subject to gradual degradation from corrosion, cracking, and material wear, so inspections are designed to identify early signs of such issues with non-destructive testing (NDT) techniques like eddy current, ultrasonic, and dye penetrant inspections. While manufacturers define baseline inspection intervals, many operators also adopt fatigue monitoring or usage-based inspection programs for these areas, that way MRO schedules are tailored more closely to their actual rate of wear.
Navigation, communication, flight control, and other avionics systems require specialized attention, with tasks largely covering diagnostic testing and software updates. In addition, specific components like sensors may be recalibrated to verify they will perform as intended.
Landing gear and braking assemblies experience significant stress while supporting aircraft in takeoffs and landings, making them a priority for life-extending maintenance practices. Routine servicing focuses on lubrication of joints and actuators, inspection of load-bearing structures, and functional testing of hydraulic and braking systems. In addition to being examined during scheduled maintenance events, these assemblies are usually overhauled based on a defined number of cycles or years in service as specified by the manufacturer to avoid fatigue-related issues.
In summary, a structured rhythm of MRO operations is what allows aircraft to exhibit safe, reliable service over extended use cycles. Scheduled checks catch issues on a rolling basis, overhauls effectively reset wear-heavy parts, and system-specific treatments make sure no area goes too long without in-depth care.
When you need access to quality aircraft components, turn to ASAP Parts Online. With billions of items from trusted manufacturers organized conveniently across our database, we make it easy to secure what you require for MRO tasks. More than that, we regularly present competitive quotes within 15 minutes of receiving a completed RFQ form, tailoring our solutions to meet the distinct specifications of each customer. With all of this in mind, we encourage you to connect with our experts at your convenience, as we are available 24/7x365.
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