Long-range German forces would require Britain to patrol the approaches to the Atlantic more closely. Once through, they would have many possible operating areas. The rule of thumb here allocates roughly one third of endurance to reaching the target area, one third to returning and one third to combat operations. On that basis, the cited 3,900-nautical-mile range difference implies about 1,300 nautical miles of operating radius. Replenishment by an Altmark-type support ship would change the calculation further. The figures are an illustration of planning constraints, not a precise fuel budget for a particular sortie.
Notable Point · 40:09-41:27
Turning endurance into a usable combat radius
A simple division of fuel between outward passage, operations and return explains why extra range matters after an Atlantic breakout.