For calculating the time and distance to the Point of No Return (PNR), which parameters are needed?

To calculate the time and distance to the Point of No Return (PNR), it is essential to consider the ground speed of both the outbound journey to the destination and the return journey, alongside the aircraft's fuel endurance.

The ground speed going to the destination provides insight into how quickly the aircraft will reach the destination. However, to determine the PNR accurately, one must also know the ground speed that will be used for the return trip. This ensures an accurate assessment of how much time and distance are available before reaching a critical fuel state where returning is no longer feasible.

Additionally, understanding the fuel endurance is crucial because it indicates how long the aircraft can fly before running out of fuel. The combination of these three parameters—ground speed out, ground speed home, and fuel endurance—enables a pilot to calculate the maximum distance they can travel toward the destination while still having enough fuel to return safely.

The other options do not provide the necessary components to make this calculation. For instance, knowing only the ground speed going to the destination would not account for the return leg of the flight, and parameters like flight altitude and air temperature or just the endurance of fuel and weight of the aircraft alone do not inform the PNR calculation directly.