The helicopter drop off frequently spawns in erroneous locations that cause it to become instantly unusable - For instance, with the rotor blades touching a tree/building that makes them tear themselves off as soon as they start spinning. It also tends to favor spawning on hills where it will slide down even if there is a large space of flat ground close by (such as a road, even if I'm standing right on the road and there are no cars nearby, plus plenty of space for the helicopter)