• Journal of Aerospace System Engineering
• /
• v.18 no.5
• /
• pp.90-96
• /
• 2024

Previous researches on helicopter noise have often focused on hovering conditions or non-lifting conditions to facilitate testing and clearly identify noise sources. While these studies are beneficial for understanding noise sources and validating analysis tools, they may not align well with noise certification flight tests. To predict and analyze results from noise certification flight tests, it is necessary to study the characteristics of helicopter rotor noise depending on microphone and aircraft positions during flight tests. Results from noise flight tests indicate that high-speed impulsive (HSI) noise dominates during forward flight, with an increase in noise observed with an increase in forward Mach number. Broadband noise is predominant after the helicopter passes the microphone compared to blade noise. Noise during landing approaches exhibits complex and irregular characteristics due to interference between blades and tip vortex.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.187-192
• /
• 2006

Helicopter noise has been considered as one of major design factors like a performance and safety since the public acceptance, comfortability and stealth aspects were important for customers. According to the airworthiness regulation, the noise levels in throe different flight conditions shall comply with the specific limits. Main and tail rotors noise is most dominant in far field due to the low and mid range frequency characteristics. It is an air-born noise so That the accurate aerodynamic data is necessary for the accurate noise prediction. In KARI, low noise main and tail rotors as well as analysis codes have been developed since 2000. The approach for low noise main rotor is a kind of tip modifications, so called twin vortices tip to reduce the BVI noise. Analysis results show the 9.3dB reduction in terms of pseudo EPNL. The uneven spacing concept is applied for low noise tail rotor. Three or four decibel noise reduction is achieved by new optimized uneven spacing. Rotor noise and aerodynamic prediction codes have been improved also.

• Journal of Advanced Navigation Technology
• /
• v.24 no.5
• /
• pp.329-342
• /
• 2020

In this paper, we analyzed the requirements for the application of UAM, a new concept to solve the traffic congestion in large cities. First, the current domestic and foreign status of research and development related to UAM was investigated and the pros and cons and the time required for each mission radius were analyzed for various configurations of aircraft being commercialized. In addition, in order to analyze the market acceptance of the UAM, the individual's consciousness and reliability requirements were identified and safety requirements were analyzed through accident rate data for each aircraft type. Because it operates in a densely populated urban area, requirement analyses on noise and exhaust, which are environmental factors that can affect the community were performed, and requirements related to aircraft performance, certification standards, and airworthiness standards of FAA and EASA were also analyzed.

• Transactions of the KSME C: Technology and Education
• /
• v.3 no.1
• /
• pp.71-78
• /
• 2015

Although there are differences in the classification of category adopted by each country, small UAS is usually classified as the one less than 25 kg. UAS has been mainly used for military and public purposes, but in recent years, it has spread to the private sector for hobby, media, and so on. Especially, considering the nature of the operating region and applications, it is necessary to improve operating time, noise and vibration in small UAS to ensure the same level of safety with a manned aircraft. This is because the drone can pose health and safety hazard through collision with manned aircraft or crashing into the ground. In this paper, we investigated operational regulations in the United States and European countries. Based on the investigation, a domestic system development plan for small UAS operation is under development.