CASA issued an airworthiness bulletin this week reminding engineers of the monitoring requirements for in-condition maintenance.
AWB 02-001 dated 23 July was issued in response to an ATSB investigation into a fire and fatal crash involving a Mooney M20 near Luskintyre, New South Wales in 2022.
The AWB says some engineers seem to have forgotten that “as-is” requires active monitoring such as repetitive inspections or testing to ensure the component or system remains functional.
“Some operators and maintainers, including some licensed aircraft maintenance engineers (LAMEs), have come to believe that ‘fit’ means ‘set it and forget it,’” the AWB points out. “They think it’s acceptable to do nothing until a failure occurs.
“Maintenance practices that incorrectly equate ‘as required’ with ‘fit and forget’ and/or ‘fit until failure’ will not achieve the levels of safety and reliability inherent in the aircraft design.
“At best, this can lead to operational surprises that could prove very costly. At worst, it can jeopardize the safety of an aircraft and its occupants.”
Condition-based maintenance refers to inspections and checks used to detect degradation in condition or performance. Items are left in service provided they continue to meet a desired standard of physical condition and performance.
Most often, private and aerial work category aircraft engines are conditionally operable, allowing the aircraft owner to bypass the TBO time provided an engineer is satisfied with the engine. An engine must be re-inspected and re-certified at the next periodic inspection.
“Article performance may include, but is not limited to, cleanliness, cracks, deformation, corrosion, wear, pressure or temperature limitations, leaks, loose or missing fasteners, and is published in the approved aircraft or aircraft component data,” the AWB states.
“Therefore, condition-based maintenance means an inspection/check that may result in the removal of an item before it fails in service.”
Mooney VH-UDQ crashed in 2022 after an O-ring seal on the engine-driven fuel pump failed due to deterioration, causing a fire in the engine compartment. Although the pilot attempted an emergency landing, the aircraft struck trees short of the airport. The pilot later died in hospital.