92 Ill. Adm. Code 14.520
Design and Layout Requirements
Section 14.520 Design and Layout Requirements
The minimum airport design and layout requirements shall be
in accordance with subsections (a) and (b) of this Section, and with the
standards and limitations shown in Section 14.Appendix A, Illustrations A, B, C
and D.
a) Multiple
Runway Airport. Relative to the minimum standards for an airport, the
Division will not recognize any additional landing area as a runway or landing
strip, unless the proposed second or additional landing area has a runway
length of at least 80% of the effective length of the primary runway, or unless
it is a designated STOL runway. To be a designated STOL runway, it must meet
the criteria as prescribed in Section 14.Appendix A, Illustrations C and D.
b) Line
of Sight (LOS). Runway grades, terrain, structures, and permanent objects must
be such that there will be an unobstructed LOS from any point five feet above
one runway centerline to a point five feet above an intersecting runway
centerline, both points being within the area of the runway's visibility zone.
The runway's visibility zone is an area formed by connecting points located 50%
of the distance between runway ends and the runway intersection. Additionally,
LOS between same runway ends from a point five feet above the ends must be
maintained. (See Section 14.Appendix A, Illustration E.)