KUALA LUMPUR, Malaysia, Apr 5 (NYT) : A Chinese vessel that is part of a multinational search for the missing Malaysia Airlines plane in the southern Indian Ocean reported on Saturday that an underwater sensor had picked up a “pulse signal,” China’s official news agency reported.
The signal had a frequency of 37.5 kHz per second, the report said, which is the frequency used for all standard underwater locator devices attached to aircraft data and voice recorders, commonly known as black boxes. But the China Maritime Search and Rescue Center cautioned against leaping to conclusions about the reported signal, according to Xinhua, the Chinese news agency.
“It cannot be confirmed that the pulse signal detected by the Haixun 01 is related to a black box from MH370,” the news service quoted the center as saying. False alerts can be triggered by sea life, including whales, or by noise from ships.
A spokesman for the Joint Agency Coordination Center, the Australian government organization coordinating the search, said it could not verify the report.
The Australians said an alert sounded on the British Royal Navy vessel HMS Echo last week, but it turned out to be false.
The Chinese vessel, Haixun 01, was searching about 1,020 miles northwest of Perth, Australia, on Saturday when it picked up the pulse signal, Xinhua reported.
In the four weeks since Flight 370 veered off its scheduled path from Kuala Lumpur to Beijing and dropped off civilian and military radar, no trace of the plane has been found. In the past week, searchers have concentrated their efforts in several areas of the Indian Ocean more than 900 miles off the coast of Perth, Australia. A flotilla of ships from various nations have combed the water as aircraft have conducted daily reconnaissance flights.
Crews aboard the planes and ships have spotted floating items nearly every day, but so far all the objects have turned out to be fishing equipment and other detritus not related to Flight 370.
On Saturday, 10 military planes, 3 civilian jets and 11 ships were scheduled to search an area about 1,050 miles northwest of Perth, and the signal reported by the Chinese ship appeared to come from that area, according to coordinates provided by Xinhua.
The Haixun 01 has been a regular member of the search flotilla for days and is one of at least eight vessels China has deployed to the Indian Ocean to help in the search.
On Friday, search coordinators announced that the underwater phase of the hunt had begun with the addition of two military ships — one from Australia and the other from Britain — equipped with underwater sensor technology.
Both those ships planned to resume their underwater search on Saturday, the Australian Coordination Center said in a statement early in the day. There was no mention, however, of the Haixun 01’s part in the underwater search or whether it was outfitted with technology for detecting black boxes.
The Haixun 01 went into service last year, when the Shanghai Maritime Safety Administration said it was the biggest of China’s civilian maritime administration vessels with the most advanced equipment.
Black boxes are equipped to emit a signal that can be detected by a receiver under the surface of the water. The maximum detection range is typically up to about two to three kilometers, or less than two miles, though the range is dependent on various factors including the sensitivity of the receiver, sea conditions, water temperature or whether the black boxes are buried by debris.
Much hope is riding on the effectiveness of the underwater listening devices. The black boxes’ batteries, which have a life span of about a month, are expected to expire as early as this week. When they die, so will the pinger signal, leaving the boxes to rest mutely on the seabed, making their discovery far more difficult.