The TPL-25 System locates emergency pingers on downed Navy and commercial aircraft to a maximum depth of 20,000 feet.
Authorities are all but certain Malaysia Airlines Flight 370 went down in the south Indian Ocean in water that may be as deep as 23,000 feet. That makes finding the all-important “black box” flight data recorder infinitely more difficult, and a job perfectly suited to the U.S. Navy’s tow fish.
The 70-pound tow fish, which is formally known in true Pentagon style as Towed Pinger Locator 25, is a hydrodynamic microphone designed specifically to listen for the acoustic signal of the data and cockpit voice recorders carried aboard all commercial and military aircraft. It can track the devices to depths of 20,000 feet.
“Basically, this super-sensitive hydrophone gets towed behind a commercial vessel very slowly and listens for black box pings,” says Commander Chris Budde, U.S. 7th Fleet operations officer.
The U.S. Navy deployed a pair of tow fish aboard the Seahorse Standard, a Royal Australian Navy Rescue Support vessel that will drag it through the search area west of Perth, Australia. The Standard joins a flotilla of a dozen ships scouring a vast swath of sea for any sign of the Boeing 777-200ER, which vanished March 8 enroute to Beijing from Kuala Lampur.
Although satellite images have revealed debris floating in the area, authorities have so far found no sign of the airplane or the 239 people aboard.
The Seahorse Standard will drag a TPL 25 through the search area at around 3 knots, while a second is on-hand as a backup. The device, tethered to the ship by 20,000 feet of cable, remains about 1,000 feet above the sea floor, listening for the telltale ping of the underwater locator beacon installed on black boxes (they’re actually orange) and cockpit voice recorders. It can detect a transponder signal between 3.5 and 50 kHz (most commercial airliner data systems transmit at 37.5 kHz) within a 2-mile radius, and cover about 150 square miles of ocean each day.
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