TOKYO, JAPANThe Japan Aerospace Exploration Agency (JAXA) has partnered with Boeing on a joint research project to develop quieter mid-sized passenger planes.

The noise-print of airplanes is an issue that aircraft producers are trying to solve. Despite the recent fall in air traffic due to the Covid pandemic, the demand for air travel has significantly surged over time. The new routes have increased airport's both domestic and international arrivals resulting in many aircraft flying at low altitudes over big cities and the noise pollution problem.

Japan's Transport Ministry has tried different methods to fight the problem. It has even ordered planes to descend at steeper angles, which caused an increase in hard landings and forced some planes to divert to Narita, 70km outside Tokyo.

Aircraft and engine manufacturers have worked on the problem for a while, too. New-generation engines helped improving efficiency and dramatically reducing sound.

But continuously increasing air traffic volumes have made such improvements insufficient. All this puts the aviation industry in a bit of a tricky spot as it strives to meet future passenger traffic demands.

JAXA worked with Japanese aircraft industries, universities, and NASA to further quiet aircraft by tackling airframe noise for six years starting in 2013 through the Flight Demonstration of Quiet Technology to Reduce Noise from High-lift Configurations (FQUROH) project. FQUROH researchers have largely considered noise coming from flaps, slats, and landing gear – equipment that help planes to reduce their speeds while landing without sacrificing lift. The noise caused by turbulent airflow from these sources sometimes surpasses the engine noise during the final approach.

Probable solutions determined by FQUROH to reduce the noise-causing turbulent flow are practical flap-edge configuration devices, serrated lower parts of the slat to break down large-scale vortices, and perforated fairings on the landing gear.

Testing such designs with wind tunnels and computer simulations only gets you so far, hence JAXA's partnership with Boeing to build on the FQUROH research and their development of a plan for validating designs in-flight tests.

JAXA said it will continue working with Japanese manufacturers on the noise-reduction design concepts in the meantime. The agency also said it will finalize design concepts by March 2022 and that these would be ready for flight test in 2023 "or later."