When using a flight computer for PNR, which parameter is necessary for calculation?

For calculating the Pilot's Navigation Reference (PNR) using a flight computer, knowing both the ground speed out and the total distance is essential. Ground speed out refers to the speed of the aircraft over the ground in the direction of flight, which is necessary to determine how long it will take to reach a specific point, while the total distance gives a clear measure of how far that point is.

By having both of these parameters, a pilot can effectively compute the estimated time en route to the point of no return, enabling informed decision-making regarding fuel management and safety during flight. This ensures that enough fuel is onboard to return or reach another safe destination.

The other parameters listed, such as ground speed home, the aircraft's weight, or the length of the flight plan, do not provide the specific information needed to calculate PNR. Ground speed home would not help in determining the outbound leg of the flight. The aircraft's weight, while significant in performance calculations, does not directly affect the PNR calculations, nor does the length of the flight plan alone, without the necessary speed and distance data.