How often should the PM calculate the total Fuel-On-Board upon entering a holding pattern?

The requirement for the Pilot Monitoring (PM) to calculate the total Fuel-On-Board while entering a holding pattern is based on maintaining a clear understanding of fuel status, especially during prolonged holding periods. Performing this calculation every 15 minutes allows the PM to have an accurate assessment of the aircraft's fuel consumption relative to the time spent in the hold.

This regular interval is crucial for planning purposes. It enables the flight crew to make informed decisions regarding fuel management, potential diversions, and ensuring they have adequate fuel for safe operation, both in the hold and for any required go-around or alternate airfields. By adhering to this timeframe, the crew can respond proactively to any changes in fuel status, ensuring safety and compliance with operational standards.