Tutorial
6. Influences on Airport Layout
When runways are built, their layout is influenced by many factors:
These are all factors in runway and airport planning. Many issues are studied before final decisions on airport
location and runway layout are determined.
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Impact Report Maps for Ames Research Center, 1999 |
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Environmental impact requirements
for airports were first established with the National Environmental Policy Act
of 1969 and in 1970 with the Airport and Airway Development Act. These acts
ensure that due consideration is given to the effects on the quality of the
environment and the surrounding communities in regard to airport expansion,
use and development. Before building a new facility or expanding an existing
facility, an impact study or feasibility study must be done. These studies include
a critical assessment of all impact issues from soil to air quality.
Controlling water pollution from airports has been well-mastered by planners.
Airports can be major contributors to water pollution if suitable treatment
facilities are not provided for the various types of airport wastes. These wastes
include the following: domestic sewage, industrial wastes such as oil and fuel
spills and high temperature water degradation that stems from the heat of various
power plants in nearly constant use at an airport.
One of the most severe problems is that of aircraft noise in and around an airport. Laying out runways so that
air traffic patterns occur minimally over heavily populated areas is a practice now widely employed during runway
expansion and when building new airports. Controlling the land use around an airport also helps reduce the interference
of aircraft noise with the public. Noise abatement procedures during takeoff and landing make for quieter airport
operations. Such procedures consist of a faster takeoff speed quickly followed by slowing the engine once airborne
over a populated area, then returning the engines to full speed and resuming normal flight operations. This lessens
the amount of engine noise over the populated area without adversely affecting the flight. Improvements in engine
design have also been a successful factor in reducing aircraft noise.
Airports attract business and people, but airports are noisy. Businesses and people do not like airport noise.
There are very few airports in the world where no noise complaints have been recorded. Dallas/Ft. Worth International
Airport (DFW) records the time and track of every arriving and departing aircraft. If a complaint is received DFW
personnel can identify the aircraft that was the cause. There is an organization called the San Francisco Airport
Roundtable that keeps tabs on noise and other concerns at the San Francisco International Airport (SFO).
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| NASA Research A new approach to noise reduction is the active noise control effort. The primary principle of active noise control is to sense the noise disturbances in the engine and cancel them before they leave the engine. In effect, negative noise is made to cancel out the engine's sound waves so that no noise is heard. This is a multidisciplinary effort involving duct acoustics, controls, and actuator/sensor design. NASA Glenn has a unique facility for this testing. The Active Noise Control Fan is a 4-ft-diameter low-speed fan designed specifically for active noise control testing. To date, several concepts have shown successful cancellation of selected acoustic modes. Because noise is the sum of all possible acoustic modes, the effort is still in its infancy, but it has potentially high payoffs. Active noise control will contribute to the 6 db noise reduction goal of the AST program. |
The Federal Aviation Agency (FAA) makes the regulations
(CFR, Part 36) but airport operators are primarily responsible for planning and implementing action designed to
reduce the effect of noise on residents of the surrounding area. Such actions include optimal site location, improvements
in airport design, and noise abatement procedures. Noise abatement procedures can include designated arrival and/or
departure paths and procedures. Land acquisition and restrictions on airport use should not unjustly discriminate
against any user or impede the federal interest in safety and management of the air navigation system.
Over the last 10 years aircraft have been required to become less noisy. This change was accomplished with the
design of quieter engines and in some cases "hush kits" were installed on some older aircraft. The change
came in three stages where the aircraft noise level in decibels was reduced to less objectionable and less dangerous
levels. As of the first of January 2000 Stage 3, the final stage, was implemented.
The noise level of Stage 3 aircraft is comparable to a busy urban street and
is much quieter than the Stage 2 aircraft noise level which is similar to an
amplified rock music concert.
To find noise restrictions for individual airports check out the Boeing Corporation web site:
http://www.boeing.com/assocproducts/noise/airports.html
The ground on which the airport is to be built must have a stable stratum of earth upon which building foundations
can be anchored. The soil must be capable of supporting heavy loads without shifting or sinking. If the airport's
runways are to be used by heavy aircraft (airplanes with a gross weight 300,000 pounds and heavier) the underlying
soil and/or bedrock must be able to support the weight of the runway plus the aircraft's weight. Many airport runways
have several feet of reinforced concrete to support the airplanes without cracking.
Land at a greater elevation surrounding an airport such as mountains also have
a profound effect on winds. In the daytime, air next to a mountain slope is
heated by contact with the ground as it receives radiation from the sun. This
air usually becomes warmer than the air farther up the slope. Colder, denser
air in the area settles downward and forces the warmer air near the ground up
the mountain slope. This wind is called a "valley wind" because the
air is flowing up and out of the valley. At night, the air in contact with the
mountain slope is cooled by terrestrial radiation and becomes heavier than the
surrounding air. It sinks along the slope producing the "mountain wind"
which flows like water down the mountain slope. Mountain winds are usually stronger
than valley winds, especially in winter. The wind pattern on the leeward side
of a mountain contains dangerous downdrafts or "rotor waves". An aircraft
flying through such wind would encounter hazardous turbulence that would push
the airplane towards the ground. These are all considered when orienting runways
in an area near mountains.
There are many airports within mountainous areas where the
runway headings generally run parallel with the length of the valley in which they are located or run along neighboring
rivers. The terrain often influences development of the runways in the mountains. The airport runway at Aspen,
CO, Aspen-Pitkin County/Sandy Field (ASE) is located near the end of a long valley. Airplanes land up the valley
and takeoff down the valley. Mountains rise abruptly from the airport elevation of 7,815 feet to above 14,000 feet
on three sides of the airport.
Man-made obstructions like multi-storied high rises, transmissions towers and bridges can and do influence runway
orientation. Landing at Reagan National Airport on Runway 15 requires a curving approach that follows above the
Potomac River's course. Takeoff on Runway 33 from the same airport requires the reverse trip following above the
Potomac River because of government buildings to the north of the river and many high buildings south of the river.
Consideration of local weather patterns is also a factor in determining an airport's layout. The weather patterns
of an area, especially the prevailing winds, are a major factor in determining runway headings. Prevailing winds
are defined as the direction from which the winds blow most frequently. Remember that airplanes take off and land
into the wind. Let's say that at a given airport the prevailing winds blow in from the west 65% of the year, while
30% of the year the wind blows in from the east, and the remaining 5% coming from the northwest. It would be best
then to orient the runway W (27) and E (9). That would mean that approximately 95% of the year airplanes would
be landing and taking off into the wind. In most of Texas and Oklahoma the runways are generally N-S runways because
the winds are usually from either the North or South. In parts of the Eastern United States there are many airports
with NE-SW and NW-SE runways because the winds are more likely to change between those two directions.
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