In support of FAA’s development of noise certification
and measurement criteria for unmanned aerial systems (UAS), the DOT’s John A. Volpe National Transportation Systems Center undertook research leading to a small, lightweight Global Navigation Satellite System-based
tracking system, a noise certification test on a relatively large, fixed wing UAS, and continued testing and progress on a
method of conducting noise tests on UAS.
The noise certification test on a Navmar TigerShark UAS was conducted according to CFR Title 14 Part 36 Appendix
G, Take-off Noise Requirements for Propeller-Driven Small Airplane and Propeller-Driven, Commuter Category Airplane Certification
Tests. “The TigerShark did not meet the Appendix G standard, we believe primarily because the aircraft was not optimized
for low noise operations,” the Volpe report concludes.
Volpe staff also conducted flight and noise
tests on their inhouse UAS vehicles, postulating that annoyance might be a function of the individual vehicle operational
mode. They made these recommendations:
• FAA should continue to fund the development of the Volpe tracking system so that the system can be utilized
in future UAS noise tests, with a focus on improving the software usability to work with intended applications more efficiently
and effectively in the field;
• FAA and Volpe should expand the number of vehicles tested, particularly those near the 55 pound cutoff,
to determine if this weight limit is adequate to protect the public from undue UAS noise;
• FAA should consider developing a set of recommendations to UAS manufacturers,
encouraging them to include noise mitigation in their UAS design criteria;
• FAA should engage with psychoacoustic subject matter experts from Volpe,
NASA, NPS, other federal agencies, and academia to determine which metrics adequately represent the human response to the
noise characteristics of different UAS modes of operation.
“Accurate position information of the UAS during noise testing is important for assuring
the quality of the test results,” according to Volpe’s report to FAA, the agency that sponsored the research. “The tracking system developed by
Volpe allows for various levels of accuracy depending on the system configuration and latency/real-time data requirements.
The system can achieve accuracy to the subfoot level with post-processing. [It] has been refined through inhouse UAS vehicle
tests but has not yet been optimized for field campaigns in a noise measurement environment.”