Sometimes it takes a crisis to get us to rethink the way we do things. With the parking of thousands of aircraft worldwide, including the grounding 737 Max fleet it’s time to rethink some of our maintenance practices.
Let’s take wheels as an example.
Most wheel Component Maintenance Manuals require a major overhaul every certain number of tire changes, or on a calendar basis (frequently 24 months). In normal operation the calendar requirement is not much of an issue because tire changes happen frequently enough to drive the major overhaul. The major overhaul detailed in most CMMs requires complete disassembly of the wheel, stripping of all coatings, a non-destructive inspection, reapplication of the coatings, and return to service. This process is expensive, requires highly skilled labor, and produces a significant chemical waste stream. In roughly 95% of major overhauls of commercial wheels, no defects are found, and the wheels are returned to service.
When the pandemic abates, and the 737 MAX returns to the skies, countless wheels will likely be due for overhaul before they can return for service, most of which will have seen very little service since their last shop visit.
It seems like there would be a better way, and there is – Condition Based Maintenance. This approach focuses on performing maintenance based on the condition of the part, not a counter or a calendar. Resonance ultrasonic inspections are capable of monitoring wheel condition without removing the coatings from wheels at shop visits. Even more powerful, the technique can compare each wheel half to itself over time to monitor the accumulation of fatigue and damage that indicate the need for a major overhaul. PCRT has proven to reduce inspection costs and improve field reliability at the same time in several aerospace applications.
Perhaps this crisis will help us revisit CBM for wheels, and many other components.