movement and position relative to the airfield surface areas. Proper depth perception is provided when
the controller's line-of-sight is perpendicular or oblique to the line established by aircraft and ground
vehicle movement, and where the line-of-sight intersects the airfield surface at a vertical angle of 35
minutes or more. Required eye level elevation is determined using the following formula:
E e = E as + D tan (35 min + G s )
E e = Eye-level elevation (1.5 m (5') above control cab floor).
E as = Average elevation for section of airfield traffic surface in question.
D = Distance from proposed tower site to section of airfield traffic surface in question.
G s = Angular slope of airfield traffic surface measured from horizontal and in direction of
proposed tower site (negative value if slope is downward towards the tower, positive value if slope
is upward towards the tower).
A18.2.7. Siting should conform to airfield and airspace criteria in Chapter 3. Deviations should only
be considered when they are absolutely necessary. Any siting deviations that would normally require a
waiver must be subjected to a TERPS analysis performed by the appropriate MAJCOM TERPS office
and AFFSA TERPS. If the analysis reveals that the control tower will not adversely affect instrument
procedures, the ATCT siting may be considered a permissible deviation with coordination from
AFFSA/XRE and the MAJCOM DO and CE.
A18.2.8. Siting should provide an acceptable orientation of the tower cab. The preferred tower cab
orientation in relation to the runway is obtained when the long axis of the equipment console is parallel
to the primary runway. The reason for this orientation is to allow controllers to face the runway and
the ATCT instrument panel without frequently turning their heads to observe events on the runway.
Preferred direction should be north (or alternatively, east, south, or west, in that order of preference)
when sited in the Northern Hemisphere. Also, locations that place the runway approach in line with
the rising or setting sun should be avoided.
A18.2.9. Siting should be such that visibility is not impaired by external lights such as floodlights on
the ramp, rotating beacons, reflective surfaces, and similar sources.
A18.2.10. Siting should consider local weather phenomena to keep visibility restriction due to fog or
ground haze to a minimum.
A18.2.11. Siting should be in an area relatively free of jet exhaust fumes and other visibility
impairments such as industrial smoke, dust, and fire training areas.
A18.2.12. The tower should be sited in an area where exterior noise sources are minimized. For noise
level determination, site selection project engineers should enlist the assistance of a host base civil
engineer and a bioenvironmental engineer. They should also make use of the Air Force
Bioenvironmental Noise Data Handbook (AMRL-TR-7550) and noise level data available in the Base
Comprehensive Plan. Special efforts should be made to separate the ATCT from aircraft engine test
cells, engine run-up area, aircraft parking areas, and other sources of noise.
A18.2.13. Efforts should be made to site the ATCT so that access can be gained without crossing areas
of aircraft operations.