摘要 :
The results are ultimately used to estimate the potential for damage to a wide variety of cultural resources from operations of commercial helicopters. Comparison of measured vibration levels with criteria for damage based on stru...
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The results are ultimately used to estimate the potential for damage to a wide variety of cultural resources from operations of commercial helicopters. Comparison of measured vibration levels with criteria for damage based on structural velocities will provide a family of restrictions on aircraft operations in the vicinity of sensitive structures. Such restrictions could take the form of minimum separation distances and prohibited maneuvers for helicopters. The results of the study would be presented in a report as a set of recommended procedures for helicopter operations to avoid damage to prehistoric, historic, sensitive and conventional structures.
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摘要 :
The report summarizes the available literature on aircraft noise-induced vibrations of structures, with a focus on damage to historical and cultural resources. An important effect of aircraft noise may be the initiation of cracks ...
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The report summarizes the available literature on aircraft noise-induced vibrations of structures, with a focus on damage to historical and cultural resources. An important effect of aircraft noise may be the initiation of cracks in the surfaces of structures. This apparent insignificant event can be the first step to further damage in the long term by the forces of nature. Perhaps the most significant finding from the literature review is the potential damage risk from helicopters. The noise characteristics of helicopters are such that they tend to excite nearby structural elements at their resonance frequency, causing low frequency vibrations, rattle, and in some cases, damage. The sound pressure is greatest at structures in the plane of the main rotor, such as could be the case for a helicopter approaching a cliff dwelling. Each of the four experienced some risk of damage from overflights, including: Fort Jefferson National Monument: Fragile mortar may be susceptible to damage from sonic booms. White Sands National Monument: Flat roof with viga construction is susceptible to damage from helicopter noise. San Antonio Mission National Historic Park: Masonry buildings with intact roofs are in the very high risk category for sonic booms, low-flying subsonic multi-engine bombers, and heavy (greater than 20,000 lbs) helicopters. Chaco Culture National Historic Park: Rubble-core adobe walls are somewhat susceptible to damage from helicopter noise.
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This report describes the results of studies of the sensitivity of the noise exposure contours to various model parameters and assumptions presently in the NOISEMAP procedure. The areas within Day/Night Level (LDN) contours for te...
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This report describes the results of studies of the sensitivity of the noise exposure contours to various model parameters and assumptions presently in the NOISEMAP procedure. The areas within Day/Night Level (LDN) contours for ten Air Force airbases increased by 11 to 4O percent when the noise measure was adjusted for the presence of pure tones. The contour areas for typical mixed fighter, bomber/tanker, and training airbases were reduced by 3 to 11 percent by substitution of the SAE algorithms for ground-to-ground propagation and transition models, whereas adding the fuselage shielding algorithm reduced the contour areas by 13 to 22 percent. Since there is little firm evidence showing one set of algorithm more accurate than the other, the present NIOISEMAP models will be retained until further technical analyses or new data show a clear basis for alteration. The contour areas for typical National Guard and combined bomber/tanker/fighter airbases for standard day weather conditions were reduced by up to 10 percent using sumner-type climate conditions, but were reduced by 18 to 60 percent by winter weather conditions. Although use of standard dry conditions results in contours that are quite representative for most bases, it is recommended that contours be developed based on a simple review of the absorption coefficients (for the 1000 Hz one-third octave frequency band) determined from the set of monthly average temperatures and relative humidities.
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The relative effectiveness of three changes in aircraft operating procedures and/or aircraft hardware in reducing noise exposure around three major airports (O'Hare International Airport, Chicago, John F. Kennedy Airport, New York...
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The relative effectiveness of three changes in aircraft operating procedures and/or aircraft hardware in reducing noise exposure around three major airports (O'Hare International Airport, Chicago, John F. Kennedy Airport, New York, and Los Angeles International Airport) were rated by determining the relative change in land areas falling within Noise Exposure Forecast (NEF) 30 and 40 contours. For projected 1975 operations, sets of NEF contours were calculated for changes which included: power cutbacks after takeoff and two segment approaches for all aircraft, and retrofit of current four-engine turbofan aircraft with either acoustically - lined nacelles or with a 'quiet' engine under development by NASA. (Author)
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摘要 :
The effectiveness of changes in aircraft operating procedures and aircraft hardware regarding the reduction noise near airports were rated by determining the changes in land areas falling within the Noise Exposure Forecast contour...
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The effectiveness of changes in aircraft operating procedures and aircraft hardware regarding the reduction noise near airports were rated by determining the changes in land areas falling within the Noise Exposure Forecast contours. Sets of NEF contours were constructed for two different aircraft types operating from a single runway airport; the number of operations per day was varied from 200 to 1000. The changes included power cutbacks after takeoff, two segment approaches and retrofit of four-engine turbofan aircraft with acoustically-lined nacelles or with a 'quiet engine'. (Author)
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摘要 :
Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at Chicago O'Hare International Airport are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with resp...
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Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at Chicago O'Hare International Airport are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with respect to aircraft noise; hence, the NEF areas may be used as a guide to land-use planning or zoning. The NEF areas are based upon aircraft noise described in terms of effective perceived noise levels, plus consideration of the number of operations per daytime and nighttime period. NEF areas B and C show sizable increases between 1965 and 1970, particularly in northeast and southwest directions. Between 1970 and 1975, further moderate increases in NEF areas B and C are forecast.
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摘要 :
Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at John F. Kennedy Airport, New York, are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with respec...
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Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at John F. Kennedy Airport, New York, are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with respect to aircraft noise; hence, the NEF areas may be used as a guide to land-use planning or zoning. The NEF areas are based upon aircraft noise described in terms of effective perceived noise levels, plus consideration of the number of operations per daytime and nighttime period. NEF areas B and C show sizable increases between 1965 and 1970. Between 1970 and 1975, a very moderate increase in NEF areas B and C is forecast.
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摘要 :
Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at Los Angeles International Airport are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with respect...
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Noise Exposure Forecast (NEF) areas resulting from takeoff and landing operations at Los Angeles International Airport are shown for 1965, 1970, and 1975. The NEF areas depict areas of differing land-use compatibility with respect to aircraft noise; hence, the NEF areas may be used as a guide to land-use planning or zoning. The NEF areas are based upon aircraft noise described in terms of effective perceived noise levels, plus consideration of the number of operations per daytime and nighttime period. NEF areas B and C show a relatively large increase between 1965 and 1970 reflecting a large increase in the number of airport operations and expanded use of Runways 24L and 24R in 1970. Between 1970 and 1975, only a slight increase in NEF areas B and C is observed, since only a moderate increase in total number of operations has been forecast.
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