What type of inspection can be classified as unscheduled?

The classification of an inspection as unscheduled is typically associated with the conditional inspection. A conditional inspection is conducted when specific conditions warrant a closer evaluation of an aircraft’s structure or systems; these conditions could arise unexpectedly due to operational circumstances, such as a hard landing or unusual vibrations. This type of inspection does not follow a systematic schedule like other inspections but instead is prompted by a particular event or concern that arises, reflecting its unscheduled nature.

In contrast, other inspection types like turnaround inspections, acceptance inspections, and phase inspections are performed according to predetermined schedules or criteria, making them routine rather than unscheduled. Turnaround inspections are conducted before an aircraft is made ready for the next flight, acceptance inspections occur when new equipment is received, and phase inspections are systematic evaluations occurring at specific intervals in the maintenance process. These types of inspections are planned and regular, which distinguishes them from the conditional inspection's reactive approach.