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AC 150/5300-4B <br />6/24/75 <br />30. RUNWAY LONGITUDINAL GRADE. Figure 7-3 is a longitudinal profile of <br />grade limitations. For the safe operation of airplanes, the longi- <br />tudinal grades on runways should not exceed the limitations set forth <br />in this figure. In stage construction, it is important to consider <br />the sight distance for the ultimate runway length. <br />31. LINE -OF -SIGHT. Line -of -sight standards impose an additional restraint <br />on the determination of surface gradients. It is desirable to provide <br />an unobstructed line -of -sight along the entire length of an individual <br />runway or taxiway, as well as along the entire length of an intersecting <br />runway. The following paragraphs provide line -of -sight standards which <br />should be met as a minimum. <br />a. Along Individual Runways. <br />(1) Airports Not Having a 24-hour Control Tower. Runway grade <br />changes shall be such that any two points 5 feet above the <br />runway centerline will be mutually visible for the entire <br />runway length. However, if the runway has a parallel taxiway <br />for its full length, runway grade changes may be such that <br />an unobstructed line -of -sight will exist from any point 5 feet <br />above the runway centerline to all other points 5 feet above <br />the runway centerline within a distance of half the length of. <br />the runway. <br />(2) Airports Having a 24-hour Control Tower. Although it is <br />desirable to provide the above line -of -sight for the entire <br />runway length, adherence to longitudinal gradient <br />standards will provide an adequate line -of -sight at these <br />airports. However, before applying these criteria, a careful <br />analysis must be made of the control tower's operation to <br />assure that it will remain a 24-hour tower. Visibility <br />requirements from the air traffic control tower to airport <br />surface areas utilized in aircraft ground movement must also <br />be considered. <br />b. Between Intersecting Runways. <br />(1) <br />Page 30 <br />Airports Not Having a 24-hour Control Tower. Runway grades, <br />terrain, structures, and permanent objects must be such that <br />there will be unobstructed line -of -sight from any point 5 feet <br />above one runway centerline to any point 5 feet above an <br />intersecting runway centerline, both points being within the <br />area of the runway visibility zone. The runway visibility zone <br />is an area formed by imaginary lines connecting the two runways' <br />visibility points as shown in Figure 7-4. The location of each <br />runway's visibility points is determined in the following manner: <br />Chap 7 <br />Par 30 <br />