Wednesday, March 08, 2017

Helicopter Noise-Reduction Study Focuses on Unconventional Flying Techniques: Quicker, steeper descents for some approaches tend to minimize noise footprint on the ground, report says

The Wall Street Journal
Updated March 8, 2017 6:54 p.m. ET

Facing persistent public complaints about helicopter noise in some parts of the U.S., researchers on Wednesday released what is believed to be the first operational analysis of different ways pilots can maneuver choppers in midair—rather than just change areas they fly over—to reduce decibel levels for residents.

The report, presented by a team of industry and government experts during a helicopter conference in Dallas, includes some unexpected findings. It concludes, for example, that more-rapid and steeper descents during portions of some approaches tend to minimize a helicopter’s noise footprint on the ground. Pilots are trained to typically execute gradual descents.

The study also determined that depending on whether a helicopter turns left or right to change direction—even if it subsequently follows the same course after the maneuver—can help reduce certain noise patterns.

And perhaps the most counterintuitive part of the study notes that at least in some circumstances, accelerating descents could mitigate the impact of noise. But more study is required to demonstrate their usefulness.

All of the noise-reducing concepts have been studied over the years by academics, scientists from various federal agencies and other experts. But contributors to the report see it as the most comprehensive effort yet to encourage pilots to put theories into everyday practice.

“For the first time, we’ve taken scientific data and put it out there for average pilots to use,” according to David Bjellos, who manages a corporate fleet based in South Florida and is the principal author of the white paper.

By educating the industry about acoustics and eventually providing noise-generation models for specific helicopter types, Mr. Bjellos predicts pilots will be able to more accurately visualize where they are projecting noise “and therefore they will fly more quietly.”

Noise complaints are especially significant around Long Island and the Los Angeles metropolitan area. Often, traffic restrictions, congested airspace and air-traffic controller commands make it difficult to avoid disrupting residential areas with noise from choppers.

The report emphasizes that in the long run, routine adherence to certain in-flight techniques can ensure that the helicopter industry embraces standard noise abatement measures the same way commercial and business jets do at most busy airports.

The study is part of a multiyear effort by Helicopter Association International, the global industry’s primary safety and advocacy organization. Some of the findings are slated to be formally endorsed by the association, and then distributed to members.

“Until such time as manufacturers develop truly quiet rotor systems with lower noise emission levels,” according to the report, “the future of our industry is dependent” on flying trajectories that apply scientific principles and learned from everyday operations.

On a local level, Mr. Bjellos said that he already has discussed the possibility of the Federal Aviation Administration agreeing to use the international airport serving the Palm Beach region of Florida as part of a pilot noise-mitigation program for helicopters.

The goal would be establishing precision approach and landing routes for helicopters—including detailed altitude and position requirements—similar to those that are now commonplace for jets at most busy U.S. airports.

Original article can be found here:


  1. Is it safe to ask the helicopter pilot to adopt a steep descent path? It is the one flying object that cannot glide if engine failure.

  2. I would definitely consider the risk/reward in asking pilots to "modify" how they approach things solely for the purpose of noise reduction. Most pilots are trained to minimize rotor flap anyways but wind direction often affects this, with no pilot inputs. The worst thing for a helicopter to get into is its own rotor wash and losing the ability to pull out of it because of a reduction in airspeed. There are some pinnacle approaches that will not allow for a "run on" type landing to minimize some noise. So in some instances this may contribute to unnecessary safety compromises. And the last thing anyone wants to be a part of is an accident resulting in injury or worse because of a subsequent "noise abatement" policy put forth. If there are all things considered (glide slope, air speed, pilot's ability to maneuver for engine/clutch/rotor failure) and a safe, less noisy approach can be figured out by manufacturers and the institutions involved, then I am all for it. But noiseless approaches are most definitely not worth putting anyone's life in more danger than they already are while operating that aircraft, including those in the surrounding area.