Which inspection translates flying hour utilization rates into calendar periods?

The isochronal inspection is specifically designed to correlate flying hour utilization with maintenance intervals based on calendar time. This type of inspection takes into account not just the number of hours an aircraft has been in operation but also the elapsed calendar time since the last maintenance check. The purpose of isochronal inspections is to ensure that aircraft are maintained and serviced at regular intervals, ensuring safety and operational readiness across a specified timeframe, regardless of actual flying hours.

In contrast, other inspections such as annual, supplemental, and operational readiness inspections do not focus on translating usage rates into a calendar-based schedule as effectively as isochronal inspections do. While annual inspections typically occur once a year, they do not specifically address the relationship between flying hours and calendar periods in the same way. Hence, isochronal inspections are key for aligning maintenance with both usage and time, making it the correct choice for this question.