Figure 33. Dirt packed against base of cone.
the mast should be as close to the obstacle as possi-
(4) Obstacle Lights Installation.
(a) In noncombat areas where obstacle
ble, and located so that the obstacle is between the
lights are needed near the ends of the runway. they
mast and the runway (figure 34). If the mast cannot
must be above the elevation of the obstacle; TM 5-
be placed immediately adjacent to the obstacle, it
330, paragraph 12-20 discusses the subject of ob-
should be placed so that the top of the mast is above
struction lighting. The mast set supplied in the sup-
the obstacle, and a line drawn from the top of the
mast to the highest point on the obstacle forms an
plementary set is used for this purpose. The mast
angle with the horizontal which is no less than the
set contains four telescoping masts, each of which is
9 feet, 5 inches (2.87 meters) long, when telescoped.
maximum glide angle for the airfield. In addition,
and 41 feet (12.5 meters) long when fully extended.
the line of sight drawn from the threshold lights to
(b) Where possible, the obstacle light
the obstacle light on the mast should clear the
should be mounted on top of the obstacle. Otherwise
Figure 34. Position of obstacle light mast with respect to obstacle.