Developing an Airport Runway

Airport runway design takes many factors into account, no matter the type of aircraft that will be using it. There are set standards for runways and parts of runways such as shoulders, blast pads, safety areas, obstacle-free areas and stopways.

The planning of a runway has to take FAA regulations into consideration. Annual weather patterns, noise, environmental concerns and existing obstructions (natural or man-made) also need to be taken into account.Runway width and length will vary depending upon the needs of the facility and type of aircraft, as well as slope and direction.Elevation and terrain must also be considered, as well as prevailing winds, wind speeds and visibility.

This paper will cover the basic requirements to be taken into consideration when developing a runway.Selecting a SiteWhen selecting the ground for a runway, the stability of the ground is critical. The soil must be capable of supporting heavy loads without shifting or sinking and must be able to anchor building foundations. In the case of large aircraft, the earth must also be able to support the weight of the concrete runway and the aircraft using it. Several feet of reinforced concrete are recommended for heavy use without cracking (NASA Virtual Skies website, Tutorial 6, 2006).

Assessment of orientation to airport facilities, existing runways (if any), natural or man-made obstacles must be conducted. The orientation of the runway will be determined by the above, as well as the locations weather patterns.The site of the runway must allow for reduction of noise from aircraft taking off and landing near communities and businesses. Statistics of weather patterns must be gathered and analyzed so that the orientation of the runway will be optimal for service to aircraft. It is most desirable for aircraft to take off and land into the wind (NASA Virtual Skies, Tutorial 6).There must also be adequate drainage of airport waste and water, to prevent a buildup of water on the finished runway.

The site must also allow for the length and width of the runway, which can be anywhere between 1000 and 10,000 feet in length, minimum 100 feet in width, depending upon the air traffic using the facility (FAA Airport Design Circular Advisory, 1989, p.33).Any obstacles such as trees, etc. must be removed from the runway site, and appropriate grading must be applied with a slope within the range of accepted FAA regulations for the type of aircraft being considered.

PaperworkThere is an enormous amount of processing that goes with building a runway, and according to the FAA, it takes about 10 years to complete a runway. Environmental Impact Statements, Planning and building permits, communications and filings with the EPA, The Dept. of Fish and Wildlife and other agencies, the securing of contractors, and processes with the public are factors that add to the long delay (Subcommittee on Aviation Hearing on Airport Runway Construction Challenges, 2001).Runway MaterialsThe aggregate of concrete used to build the runway must be able to withstand extremes in temperatures and moisture, as well as de-icing chemicals. Most airports use an asphalt/concrete mix varying in thickness depending upon the weight of the aircraft that will be using the runway. The aggregate is customarily poured on top of a layer of crushed rock.

The layer of crushed rock will be minimum 8 inches thick for light aircraft, with the paved surface minimum 5 inches thick. Variances of thicknesses of both the crushed rock base and the pavement will depend upon planed use of the runway.With continual research into concrete aggregates that are conducted, the choosing of material for the paving of the runway will be a factor in determining overall cost, such as longevity of the material, maintenance/repair projections, etc.Parts Of the RunwayIn addition to the runway itself, there are also areas to be built that serve to complete the facility, and these are:The Shoulder: This is the area adjacent to the runway that serves as a transition area supporting the aircraft should it go off the runway. The shoulder also serves as a drainage area as well as a blast protection area. The shoulder also must allow for the passage of emergency vehicles.

The Stopway: A well defined rectangular area beyond the end of the runway for emergency use in the event that an aircraft must abort takeoff. The stopway is designed for zero damage to the aircraft in such an event. Because of a longer runway used in both directions being more cost effective than a stopway, not many airports use stopways.The Taxiway: A path designated for air traffic to maneuver the aircraft from one part of the airport to another.The markings and lights are standard for all runways according to FAA regulations.

The diagram outlines the minimum features of a runway that need to be installed once the runway is oriented and built. On the outer edges (on the shoulders) are the VASI (Visual Approach Slope Indicator) lights. The slope cannot be any more than 1.5% in longitudinal gradient for the entire runway, with the exception of the first and last quarters of the runway, which must be no more than 0.

8% (FAA Airport Design Advisory Circular, p. 62). The VASI lights help aid the pilot in approaching the runway at the proper angle.The taxiway is indicated by blue lights as opposed to the runway itself, which will display white or amber lights on both sides.

The threshold lights will be green, indicating the beginning of the runway.The runway must also have an airport beacon as well as a wind vane (wind sock) indicating the direction of the wind at the runway’s surface.The eight lines at the beginning of the runway indicate the threshold, or beginning of the runway. Placed 500 feet beyond the threshold markers are the touchdown zone markings, indicating where the wheels should land on the runway. Running the length of the runway is the centerline, which should align with the front wheel of the aircraft.

After the touchdown markings are fixed distance markings, placed every 500 feet.With all of the necessary construction regulations being followed, the appropriate amount of material used for a solid runway, the installation of the required lights, markers, indicators and runway support roads, the runway is complete.Financial ConsiderationsDue to the ever-fluctuating prices of fuels and goods, it is difficult to estimate the cost of building a new runway. Most airports will extend current runways or make alterations to what is in place to avoid the hundreds of millions of dollars involved in building an entirely new runway.