Make sure there is sufficient space for the helicopter to land and take off.
a. No Obstacles Present.
(1) An Iroquois helicopter requires a relatively level landing area at least 35
meters in diameter.
(2) A Blackhawk helicopter requires a landing area of 50 meters in diameter
if there are no obstacles.
(3) A CH-47 Chinook requires a landing site at least 80 meters in diameter if
there are no obstacles.
(4) This does not mean that a loaded helicopter can land and take off from
an area the size given above. Most helicopters cannot go straight up or down when
fully loaded. Therefore, a larger site and appropriate approach and departure routes
b. Obstacles Present. When obstacles are in the approach or departure route,
a 10-to-1 ratio must be used to lay out the landing site. For example, during the
approach and departure, if the helicopter must fly over trees that are 15 meters tall, then
the landing site must be at least 150 meters long (10 x 15 =150). Figure 5-22 shows
two other examples.
Figure 5-22. Landing site distance from obstacles.