AIN Staff

Noise produced by helicopters flying overhead not only continues to be a concern, but it is becoming a greater irritant as communities expand and more helicopters take to the air.


While noise reduction remains an important goal of rotorcraft manufacturers and there are many cooperative efforts among helicopter operators, the FAA and communities about helicopter routing and altitudes, concerns and complaints about helicopter noise continue to increase.


What is perhaps not well known among some pilots are ways they can mitigate their helicopter’s noise footprint by the way they fly. Based on extensive research, these scientifically demonstrated techniques are rarely, if ever, taught in flight school, but they are now becoming more commonly used and some flight departments have begun to incorporate such techniques into their standard operating procedures.


At Heli-Expo 2017, Scott Burgess, Embry-Riddle Aeronautical University, and David Bjellos,  aviation manager, Agro Industrial Management, presented a session on “Fly Neighborly: Techniques for Noise Abatement” yesterday. This course qualified for FAA Wings Basic credit. Bjellos told AIN the intent is to continue this course at Heli-Expo 2018 and 2019 with FAA Wings Advanced and final Master-level credits. “As far as I know,” he explained, “this is the first time this type of presentation has been made using data from NASA and DOT/Volpe, both of whom contributed heavily to the presentation and vetted for accuracy.”


The well-attended presentation included real-world examples of standard operating procedures that can help mitigate noise. The information was extensive and well presented. Burgess and Bjellos even invited the audience to participate via text in an electronic survey, the results of which appeared on the big screen in front of the room. Among the questions: “If you are aware of noise-mitigation techniques, do you incorporate them in daily flight ops?” Seventeen percent answered less than 25 percent of the time; another 17 percent answered 25-50 percent of the time; and 67 percent answered more than 50 percent of the time.


Finally, and perhaps most impressively, Burgess and Bjellos presented a <a href="https://www.youtube.com/watch?v=axNHCLeyC4s&amp;index=7&amp;list=PLm_7Y91JGJbvtzBPAuHMHOjX3riok_B2K">video </a>of an experimental device that provides pilots with immediate and graphical information about the “Fly Neighborly” status of their route.


Burgess concluded, “This [noise abatement] is a big tree to chop down. We’re only taking a few swings at a time.”


The playlist can be found at:&nbsp;<a data-saferedirecturl="https://www.google.com/url?hl=en&amp;q=https://www.youtube.com/playlist?list%3DPLm_7Y91JGJbvtzBPAuHMHOjX3riok_B2K&amp;source=gmail&amp;ust=1489766609260000&amp;usg=AFQjCNEvjrLyuP7fMRiFtRk01RGQ4lbJcA" href="https://www.youtube.com/playlist?list=PLm_7Y91JGJbvtzBPAuHMHOjX3riok_B2K" target="_blank">https://www.youtube.com/playlist?list=PLm_7Y91JGJbvtzBPAuHMHOjX3riok_B2K</a>


[BOX]


So what can pilots do about flying neighborly right now?


Safe operations remain primary, of course, and Scott Burgess, Embry-Riddle Aeronautical University, and David Bjellos,  aviation manager, Agro Industrial Management, suggest that noise-reduction techniques can often be incorporated into flying procedures without compromising safety, but when they do conflict, safety takes priority. One thing some pilots (and passengers) may not know is that the noise they hear inside the helicopter is not representative of the noise that’s heard by people on the ground or recorded by noise sensors. The biggest factor of rotorcraft noise is blade-vortex interaction, which itself is affected by temperature and altitude.


All other things considered equal, flying at a higher altitude en route has noise-reduction benefits.


Higher altitude and slower forward speed are the quietest combination.


Suggested en route altitudes are: small helicopters—1,000 feet agl; medium helicopters—2,000 feet agl; large helicopters—4,000 feet agl.


On an approach to landing, steep descents create the least noise and moderate descents create the most noise. Shallow descents are in the middle of these two.


Avoid decelerating over a noise-sensitive area.


Every time the aircraft is maneuvered, it makes more noise. Smooth control inputs reduce the noise footprint.


In general, a single steady-state maneuver—turning, descending or increasing or decreasing airspeed—creates more noise than straight-and-level flight at a constant airspeed.


Deceleration in level flight creates noise.


The descent and decelerating phases of flight produce the highest levels of blade vortex interaction.


Doing multiple maneuvers simultaneously—turning while descending, reducing airspeed while turning or worst of all turning, descending and reducing airspeed at the same time—creates even more noise.


However, climbing turns are quieter than level/descending turns.


Accelerating climbs are quieter than steady-state decelerating climbs.


And probably the most counter-intuitive: turning away from the advancing blade in a turn is quieter than turning into it.


Descending, decelerating LEFT turns are quieter than descending, decelerating RIGHT turns for left-turning rotors. It is the opposite for right-turning rotors.


Route planning to avoid noise-sensitive areas requires comprehensive evaluation of these areas.


Noise-abatement procedures should be pursued by helicopter pilots (and operators) and ATC.

News and issues regarding all manner of civil and military rotorcraft and their powerplants, including helicopters, tilt rotors and unmanned air vehicles.

Heli-Expo Fly Neighborly Session Brings Some Surprises

Noise-mitigating flight techniques are rarely taught in flight school.

2024 Corporate Aviation Leadership Summit

AmyWilder

News about bills, laws, regulations and other governmental decisions affecting aviation and aerospace. Topics include FAA re-authorizations, taxes on fuel and aviation activities, environmental legislation, ICAO decisions, governmental mediation of labor conflicts and World Trade Organization disputes and decisions.

News about simulators and training procedures, as well as workforce.

Key innovations and safety updates event highlights

European Rotors 2024 Focuses on Vertical Flight Future

Matt Thurber

News and developments about aircraft engines, including turbofan, turboprop, turboshaft and piston.

News and issues relating to business, corporate and private aviation, primarily regarding turbine-engine-powered airplanes and helicopters. Subjects include aircraft, engines, maintenance, operations, personnel, acquisitions, accidents, safety, security, and training.

Preowned helicopter specialist is expanding its capabilities

Rotortrade Partners with Safran, Joins Mentor Program

Includes the sale of the 100th Bell 505 in Europe

Bell Logs Sales for 505 and 407GXi Helicopters

News and information on safety procedures and concerns.

Six accidents, two with fatalities, took place during calendar year 2023

FAA Releases 2023 Helo Air Ambulance Ops Data Summary

Charles Alcock

Both manufacturers announced new business during the European Rotors trade show

Helicopter Operators Sign Orders with Airbus and Leonardo

How a long-time fixed-wing pilot transitions to the rotary-wing world

Learning To Fly Helicopters in the Guimbal Cabri G2

Mark Huber

News about significant aircraft accidents and information from accident reports.

Jury awards $116 million for doors-off crash victim

FlyNYON Tragedy Results in Hefty Jury Award

News and issues about aviation maintenance, repair and overhaul (MRO), covering all segments of the aviation industry; and modifications for aircraft and engines. Subjects include product support of aircraft, engines and avionics, MRO company mergers, acquisitions, announcements and personnel, Airworthiness Directives, Supplemental Type Certificate approvals and other topics.

HAI Heli-Expo 2017

More In Rotorcraft