Airline failed to service pingers on black boxes?

The acoustic pingers on the missing Malaysia Airlines plane's two black boxes were due for overhauls and battery replacements in 2012 but were never returned to their manufacturer, according to a media report.

Anish Patel, president of pinger manufacturer Dukane Seacom of Sarasota, Florida, said the US National Transportation Safety Board has told his company that it manufactured the pingers on the Boeing 777-200's black boxes, formally known as the flight data recorder and the cockpit voice recorder.

The devices were manufactured in late 2005 and late 2006 and were due for overhauls and new batteries in 2012, Patel, the Indian-origin top executive, said. But "we have no record of those units ever coming back for a battery replacement," he said.

It leaves three possibilities, Patel said: The airline could have replaced the old pingers with new ones, it could have had another company perform the necessary maintenance, or it could have let the scheduled maintenance lapse, meaning the pingers would have a shortened battery life.

"If the original batteries remain in the pingers, the battery life probably will have dropped from the required 30 days to 20 or 25 days," Patel, said.

Commenting on reports of a number of underwater sounds detected in the southern Indian Ocean and whether it came from the flight recorder of MH370, Patel said: The signal reported "is the standard beacon frequency" for the plane's cockpit voice recorder and the flight data recorder. But he said additional equipment should be deployed quickly to the area from where the signals were detected.

"I'd like to see some additional assets on site quickly - maybe some sonobuoys," Patel said, referring to 13-centimetre-long sonar systems that are dropped from aircraft or ships.