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18 The following list of potential strategies was developed from the literature review (in particular the HAI Fly Neighborly Guide and the Los Angeles Helicopter Noise Initiative Report), and the airport survey. The list is followed by relevant discussion of each strategy. As noted in the Los Angeles Heli- copter Noise Initiative Report, ensuring safety is the FAAâs primary mission and none of the potential measures should be considered where such a measure might compromise safety. LIST OF POTENTIAL STRATEGIES FOR USE BY AIRPORT AND HELIPORT OPERATORS â¢ Outreach â To both community and operators â Flight track monitoring maps to aid discussion with community and operators â Establish local or regional forum to address helicopter noise. â¢ Helicopter noise management program â Collect and analyze complaints â Flight track monitoring n Report helicopter compliance â Published guides or brochures. â¢ Technology â Quieter aircraft â Pilot aides; that is, Global Positioning System-based routes and use of visual landmarks. â¢ Noise abatement procedures â Noise abatement routes â Minimum altitudes â Reducing high-speed impulse and blade slap n Reduced speed effect n Minimize tight turns â Limit hovering. â¢ Media pooling â¢ Fees based on quiet technology â¢ Voluntary operational limits and curfews. DISCUSSION OF NOISE MITIGATION STRATEGIES Outreach The airport operators responding to the survey universally identified outreach as the number one component of their programs. The outreach refers to both outreach to the community and outreach to helicopter operators. Airports that have flight track monitoring systems use the flight track maps as a means of communication with both the community and operators. Because the establishment of helicopter routes and altitudes must be integrated with the safe separation of helicopters from fixed- wing aircraft it is imperative that the community understand the constraints and also understand that FAA, not the airport, controls all aircraft in flight. Some airports have been successful in establishing community noise forums (San Francisco International Airport, Oakland International Airport, and Los Angeles International Airport) and these forums have been useful in bringing the airport operator, chapter seven EFFECTIVE PRACTICES AND MITIGATION OF HELICOPTER NOISE
19 the community, FAA, and the aircraft operators into a forum or round table for discussing issues and developing noise management programs. Helicopter Noise Management Program A noise management program is a means to implement the goals of reducing helicopter noise in the community and track the progress toward meeting that goal. It is not possible here to develop a univer- sal noise management program that will fit all airports. Effective noise management programs require input from all stakeholders. The roundtable/noise forum structure described previously may be use- ful for complex situations or developed as part of another community outreach or public forum that the airport may already have in place. The keys to establishing a program are setting goals, developing implementation programs, and monitoring progress on meeting those goals. Periodically, new goals or modified goals and implementation measures may be needed. A helicopter noise management program that recommends routes and altitudes will have to be developed with FAA as only this agency may set routes and minimum altitudes. It may be possible in noncongested airspace for an airport to suggest voluntary routes and minimum altitudes; however, in congested airspace this program will need to be coordinated with FAA and only FAA can publish these routes and altitudes on official aeronautical charts. It is generally considered poor noise manage- ment practice to move noise from one community to another; therefore, establishing route structures requires looking for potential impacts created by new routes. Suggested means to monitor progress include tracking noise complaints and monitoring flight tracks. A good example of complaint tracking is the program designed for the Long Island (New York) area. Analyzing trends in noise complaints can identify progress or regression in terms of trends in the number and location of complaints. Complaint tracking is enhanced when complainers provide their location so that complaints can be mapped. The Los Angles Helicopter Noise Initiativeâs Auto- mated Complaint System is the first county-wide system dedicated to helicopter noise and uses flight track monitoring to correlate complaints with specific helicopter operations. Flight track monitoring is common at airports with noise monitoring systems and less common at smaller airports. There are multiple vendors that provide flight tracking systems and they can be costly. A relatively new feature of flight tracking systems is providing a web portal so that community members and operators can visually see aircraft flight tracks in near real time or historical data, although the ability to accurately identify helicopters varies with the system capabilities and the data feed. Some of these systems allow for online noise complaint entry. Examples of flight tracking web portals for the community can be found at the following airports websites: http://www.flysfo.com/flight-info/flight-tracker http://webtrak5.bksv.com/oak www.planenoise.com http://www.ocair.com/communityrelations/flighttracking/ http://www.portseattle.org/Environmental/Noise/Noise-Abatement/Pages/Aircraft-Monitoring- System.aspx http://heli-noise-la.com/. Note that these websites provide an example from each of the vendors of flight tracking systems. Flight track monitoring is a useful tool for communicating with the public and with the operators. It clearly demonstrates where the helicopters actually are and at what altitudes. Sometimes helicop- ters are difficult to identify on these systems because they do not always broadcast their unique iden- tity. As part of the Los Angeles Helicopter Noise Initiative, FAA now has helicopters broadcasting a unique code identifying them as helicopters. Las Vegas and Washington D.C. also have helicopters that broadcast a unique code for easy identification. It might be useful for FAA to adopt this program throughout the country so that helicopters would be easier to identify in flight tracking systems. For example, currently when any aircraft is flying under Visual Flight Rules it broadcasts the common identifying number, 1200. This includes fixed-wing aircraft and helicopters. The new program in
20 Los Angeles has the helicopters broadcasting 1205 or 1206, which makes them distinguishable from fixed-wing aircraft. Where airports or FAA have established voluntary or mandatory helicopter routes, the flight tracking system can monitor and report adherence. An example of a helicopter flight track map used as part of helicopter noise management program is shown in Figure 1. The dissemination of the recommended noise management program is a key part of implementation. Published guides or brochures are a common tool, as well as the Internet to distribute information on helicopter noise management programs. Appendix E contains a few examples of helicopter brochures. Brochures are now more commonly published on the web; however, some airports use printed versions to distribute to the operators. The brochures, while intended for helicopter operators, are also useful in communicating with the community. The community can observe what efforts are being made by the airport to manage helicopter noise and may contribute to a better understanding of helicopter patterns. There is an additional tool available to airports. A commercial firm is providing a noise abatement program dissemination service to airports. This is relatively new and requires the airport to subscribe to the service, which provides a basic service for free and more advanced services for a fee. In addition, the Boeing Aircraft Company operates a very detailed website that publishes noise abatement programs from airports worldwide. Each airport provides the information to Boeing, and Boeing manages the database (information from this database should be confirmed with the airport in case of any updates): http://www.boeing.com/commercial/noise. Technology The important contribution of technology in reducing helicopter noise comes from designing and producing quieter helicopters. This is not under the control of the airport or heliport operator. The FIGURE 1 A plot of Las Vegas helicopter tracks for 1 week, September 2015. (Source: Track data courtesy of Las Vegas Department of Aviation, plotted in Google Earth Pro by L&B.) Legend Arrivals Departures Las Vegas Helicopter Tracks
21 literature search for this synthesis found research from agencies such as NASA, university consor- tiums, and industry about how to design helicopters to reduce noise. However, there is a compli- cating factor when it comes to quieter helicopter technology. Helicopters remain in the fleet much longer than fixed-wing air-carrier aircraft and there is no mandatory phase-out of older, noisier helicopters. Another technology development that may affect helicopter noise is the introduction of advanced navigation aids and the modernization of ATC systems. Helicopters are generally flown under visual flight rules and adherence to recommended or mandatory routes is generally by visual landmarks. The much-publicized FAA Next Generation (NextGen) ATC system has to date focused on fixed-wing aircraft; however, eventually Global Positioning System-based navigation may be used to improve adherence to helicopter flight routes. It can be noted that this program is not under the control of the airport or heliport operators; rather, it is solely the responsibility of FAA. The technology approach that is available to airport and heliport operators has already been described in terms of flight tracking technology and noise complaint tracking. Noise Abatement Procedures An airport or heliport operator has a role in the development of noise abatement procedures. Noise abatement procedures as used here specifically imply operating the helicopter in a way that reduces noise. Operational limits in terms of time, numbers, and type of aircraft are discussed later in this sec- tion. There are a number of resources available to help the airport operator develop recommendations for a noise abatement program. It is important for airport operators to note that it is beyond their role to tell operators how to fly an aircraft and that any such noise abatement recommendations must be consistent with the safe operation of the aircraft. The HAI Fly Neighborly Guide and the report on the Los Angeles Helicopter Noise Initiative are useful for this purpose. In addition, an airport opera- tor can review programs at other facilities; a prominent example of such a program is the Las Vegas helicopter noise management program (see brochure in Appendix E). This closing discussion of noise abatement programs is divided into the following four procedures: â¢ Noise abatement routes â¢ Establishing minimum altitudes â¢ Reducing high-speed impulse and blade slap noise â Reduced speed effect â Minimize tight turns â¢ Limiting hovering activity. Noise abatement routes are an important component of any noise abatement program, but are impossible to generalize for all airports or heliports. The development of recommended helicopter routes is unique to each facility and must take into account the land use patterns, runway and flight corridors, airspace structure and congestion, local topography, and the missions of the helicopters using the facility. As expressed in the HAI Fly Neighborly Guide, as well as most literature on the subject, the goal is to avoid or minimize overflying noise-sensitive land uses whenever possible. The opportunity to do this is highly dependent on the land use patterns and geography surrounding any facility. A common approach is to recommend that helicopters overfly freeways or major highways. A note of caution regarding this strategy; if there is two-way traffic on this recommended route ATC will keep aircraft flying in one direction to one side of the road, and traffic in the other direction will be kept to the other side of the road, separating the two by at least several hundred feet. In effect, this keeps the airspace above the road free of helicopter noise. Instead, the noise is directed to the proper- ties that are to either side of the road. The effect on this procedureâs efficacy is dependent on how much helicopter traffic is using the route. Too much traffic will render the route significantly less effective than expected. In Las Vegas, the roads are generally overflown by one-way helicopter traffic only. The result is twofold, a tighter concentration of flight tracks over the roads and fewer flights over any particular road, and a concomitant use of additional roads to accommodate the one-way overflights. In Las Vegas this has been quite successful.
22 Establishing minimum altitudes can reduce helicopter noise. The altitude of the helicopter has a direct effect on the noise level experienced on the ground. It is common for communities with heli- copter noise issues to request higher minimum altitudes. Where altitudes can be raised the level of annoyance may be reduced as a result of both acoustic and nonacoustic factors. The noise may be diminished with higher altitudes and the concern over possible accidents or a sense of an invasion of privacy may also be reduced, particularly where the existing routes are on the order of 500 feet above ground level. However, safety concerns frequently limit the altitude at which helicopters are permitted to fly. The Los Angeles Helicopter Noise Initiative Report discusses the issues with raising helicopter altitudes in more detail: Due to their special operating characteristics, helicopters are allowed under federal regulations to operate at lower altitudes than fixed-wing aircraft. When establishing altitudes for helicopter routes, the FAA will con- sider the speed compatibility of aircraft operating in the same airspace. Despite the advancements in situational awareness technology, VFR [visual flight rule] pilots must abide by the see-and-avoid concept of flight. For safety reasons, helicopter routes are generally designed to be flown at altitudes below arrival and departure routes for fixed-wing aircraft to segregate the slower helicopter traffic to the extent possible. Having slower helicopters operate at the same altitude as fixed-wing aircraft that are two to three times faster increases the risk of evasive maneuvers occurring over congested areas and would create an unsafe environment. In addition, vertical separation must be maintained between aircraft due to the dangers of wake turbulence, which has been identified as the cause of numerous injuries to crew and passengers as well as a contributing factor in many fatal accidents. Wake turbulence is most dangerous at low altitudes and increases in strength depending on the size of the aircraft generating the wake. The Terminal Collision Avoidance System (TCAS) is another consideration. TCAS is deployed in air carrier aircraft and is designed to alert pilots to possible collisions with other aircraft. Takeoff and landing are consid- ered critical phases of flight, and it is important to avoid unnecessary TCAS alerts and potential resulting eva- sive actions that could result from increasing the numbers and types of aircraft operating within the same area. The FAA would subject any proposed altitude changes to an FAA Safety Risk Management Panel prior to publication on the VFR Helicopter Chart. This discussion from the FAA report shows that the ability to raise helicopter altitudes will be dependent on several complex airspace factors. The difference in speed between fixed-wing air- craft and helicopters presents a significant obstacle to having both types of aircraft at a common altitude. Within any given region there may be places where altitudes can be raised and others where they cannot. The inability to raise altitudes may be more difficult near airports and less constrained at farther distances. There are no simple guidelines that can be used to determine if altitudes can be raised. The airport operator will need to work with FAA and assess each situation on a case-by-case basis. Reducing high-speed impulse and blade slap noise is a major goal of the HAI Fly Neighborly program (HAI 2009). There is the so-called âfried eggâ diagram that relates the aircraft forward speed to descent rate and the potential to cause blade slap. Although multiple reports showed an example of such a plot, the plot was generally shown only for one aircraft type; the variables change by aircraft type. The HAI program provides specific procedures for a list of aircraft. Unfortunately, the list is not complete and has not been updated since 2009. The Fly Neighborly Program is well-established; however, an army study measured the noise generated by a helicopter abiding by those landing proce- dures and offered evidence that the glide slopes and landing approach speeds that made for the quietest approaches did not always match those recommended in the Fly Neighborly guidelines. This could be the result in part to a discrepancy this study highlighted between the measurements of sound levels from aboard and outside of the helicopter of focus, with the former being what was used in the creation of the Fly Neighborly recommendations, even though the latter would better reflect the surrounding communityâs experience of helicopter noise. It is also unclear how definitive the âFly Neighborlyâ charts are. Because they were gathered in near ideal conditions, it raises the question of whether they adequately predict the likely occurrence of blade slap during turbulence or maneuvering flight. Although the Fly Neighborly program is a good reference, additional work for each helicopter type under a variety of conditions would be a useful expansion of the program. This would require substantial additional research and measurements. The state of the art of helicopter noise abatement could benefit from helicopter manufacturers pub- lishing clear procedures for each aircraft type, at which time HAI could update its recommendations. There are two other variables that may be used to reduce helicopter noise. Reduced helicopter speed
23 effect, by even a few knots, can have a significant effect on the noise experienced on the ground. Also, tight turns can focus increased noise on a particular location. Again, the ranges of speed and tightness of turn may be helicopter type dependent. More work by helicopter manufacturers on these topics, along with an effective method for transferring this technology to airports and helicopter operators is essential. Limiting hovering activity is a method of reducing helicopter noise. Hovering not only increases the length of the noise event, the turn radius and directionality of the noise may increase noise and annoyance. However, hovering activity associated with law enforcement activity may be difficult to limit. Airports and heliports can work with the news media, photographers and paparazzi, air tours and other commercial operators to avoid extended hovering or circling and raise the altitudes of the their activity voluntarily. Media pooling is a recent effort to avoid having multiple news outlets covering the same event with multiple helicopters. The high cost of operating helicopters has contributed to a trend in news outlets of subscribing to a single-source helicopter service to provide video coverage of events of interest. This program reduces the number of helicopters in a given area at any given time and with less congestion the potential to remain over less noise-sensitive areas is improved. Fees based on quiet technology are being used in one location; however, this may be difficult to implement elsewhere. Tour operators that fly over the Grand Canyon must pay a fee for each flight. FAA and the National Park Service have implemented a reduced fee program for tour operators that use newer, quieter technology helicopters. However, this measure is not available to public airports or heliports. FAA in its Report on the Los Angeles Helicopter Noise Initiative summarizes the legal problem with a public airport attempting to implement a fee based on noise: The FAA is specifically prohibited from imposing any new aviation user fees (Consolidated and Continuing Appropriations Act of 2012, Pub. L.112-55). Airport proprietors who have accepted federal funds are bound by the terms of their grant assurances, which require them to make the airport available as an airport for public use on reasonable terms and without unjust discrimination to all types, kinds and classes of aeronautical activities, including commercial aeronautical activities offering services to the public at the airport (FAA Airport Grant Assurance 22 (a)). In addition, charges or fees that are designed to, or have the effect of, controlling noise or restricting access to the airport must comply with the requirements of ANCA and 14 CFR part 161. Voluntary operational limits and curfews are always available to an airport or heliport operator. Working with the helicopter operators and understanding their needs and looking for opportunities to reduce noise impacts by voluntarily limiting the number of daily operations; requesting use of quieter aircraft types, approaches, or departures to or from advantageous directions (wind permitting); or voluntary night time restrictions may achieve at least some of the goals that the community desires in terms of reduced helicopter noise impact. Note that some airports have a letter of agreement (LOA) with ATC describing the procedures that ATC will use to manage helicopters in the vicinity of the airport. An example letter of agreement is provided in Appendix F. In conclusion, although modern light- and medium-weight civil helicopters are much quieter than older helicopters and much quieter than heavy military helicopters they are still the focus of much community concern. This synthesis provides information to airports and communities in a concise and readable format on helicopter noise acoustics and helicopter operational attributes. It also provides helicopter noise mitigation strategies that have been used effectively by airports, pilots, and effected communities with approval by FAA to ensure aviation safety. The appendices include additional resources, as do two additional research projects that will be published through ACRP and available on the FAA website.