b. Size. Under ideal conditions, and provided the necessary clearance for the rotors exists, a helicopter can land on a plot of ground slightly larger than the spread of its landing gear. For night operations, however, a safety factor is allowed with the following criteria as a guide: 1. An area of 50 meters in diameter cleared to the ground. 2. An area beyond this, surrounding the cleared area, 20 meters wide and cleared to within 3 feet of the ground. 3. The completed LZ is thus a minimum of 90 meters in diameter (Figure 15).