“Study of low frequency flight recorder detection.”


I Yun Su – r07525010@ntu.edu.tw

Wen-Yang Liu – r06525035@ntu.edu.tw

Chi-Fang Chen – chifang@ntu.edu.tw


Engineering Science and Ocean Engineering,

National Taiwan University,

No. 1 Roosevelt Road Sec.#4

Taipei City, Taiwan


Li-Chang Chuang – eric@ttsb.gov.tw

Kai-Hong Fang – khfang@ttsb.gov.tw


Taiwan Transportation Safety Board

11th Floor, 200, Section 3,

Beixin Road, Xindian District,

New Taipei City, Taiwan


Popular version of paper 2pUWb2

Presented Tuesday afternoon, December 8, 2020

179th ASA Meeting, Acoustics Virtually Everywhere


A flight recorder is installed in every aircraft to record the flight status. When the aviation accident occurs, this recorder can help clarify the cause of the incident. Furthermore, if the plane crashes into the ocean, the underwater locater beacon (ULB) inside the flight recorder will be triggered which would make a sound that could be located by the rescue team.


In 2009, there was a serious accident involving the Air French flight 447. According to the final report, French Civil Aviation Safety Investigation Authority suggested that the ULB should acquire extended transmission time up to 90 days and increased transmission range. In Taiwan, the flight recorder has already been installed with a 37.5 kHz ULB inside the tail section of every vehicle, and now Taiwan Transportation Safety Board considered to put in an additional 8.8 kHz ULB in the flight belly. (Picture 1)

Picture 1: The positions of the 37.5 kHz and 8.8 kHz ULB on the plane.


The main propose of this study is to understand the performance of the newly bought 8.8 kHz ULB – DUKANE SEACOM DK180. Firsts off, I did the simulation on both ULB to compare the detection ranges (DR), and according to the beacon specifications, the source level (SL) of the both is 160 dB re 1μPa.


For the DR to be simulated, the transmission loss (TL) which is affected by a lot of different environmental parameters must be determined first. This study is based on the Taiwan database, and using the Gaussian beam propagation to calculate the TL. After the TL is acquired, the noise level (NL) which also has certain impact on the DR has to be determined. Generally, the lower the frequency, the longer the DR. DR can be determined by passive sonar equation, and can be derive the FOM = SL – NL – DT. The DT is Detection Threshold and the FOM is Figure of Merit, which is the maximum TL that can detect. The intersection of the TL and FOM is DR. In the study, the DT is set to be zero. At the Point A, the NL of the 8.8 kHz is 78 dB re 1μPa and for 37.5 kHz is 65 dB re 1μPa, so the FOM of the 8.8 kHz is 82 dB re 1μPa and for 37.5 kHz is 95 dB re 1μPa. The DR in 8.8 kHz ULB is about twice than 37.5 kHz ULB at Point A. (Picture 2)


Picture 2: Detection Ranges of 8.8 kHz ULB and 37.5 kHz ULB in the Point A.


In the study, I have also done the experiment in Taiwan Miaoli offshore. The results also show that the newly bought 8.8 kHz ULB would have a smaller TL and longer DR. In summary, with an additional 8.8 ULB, the more precise prediction of the beacon location could be obtained.

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