lauantai 9. joulukuuta 2017 7.57.41 UTC+2 FZ kirjoitti:
I'm driving past the nice grass field. Looks big, but it is surrounded on all sides by the 80 ft high trees. What should be a minimum length of this field, for a modern glider to safely land there? How to calculate it?

I would add 10 times the height of trees to required field length. Inexperienced pilots fly over treetops usually with too much altitude (yes it feels safer, but at same time is kind of dangerous if the field is short). Experienced pilot who aims for treetops (and with normal landing speed), 6 times tree height to touch-down should be doable.