US accident investigators have recommended that all passenger planes making long flights over water carry improved technology that will allow them to be found more readily in the event of a crash.
Prompted in part by the disappearance of Malaysia Airlines flight 370 and its 239 passengers and crew last March, the National Transportation Safety Board said one way that could be accomplished was with tamper-resistant transmitters that send a plane's location minute by minute via satellite.
It also asked that the government require that planes carry low-frequency underwater beacons whose signals are more easily detected by search vessels. And it wants them to have longer-lasting batteries that can function for at least 90 days after a crash, instead of the 30 days required at present.
The board also asked the government to require that planes be equipped with cockpit video recorders.
But even with such technologies, black boxes deep under water can be difficult to find and retrieve. The board suggested they could be made ejectable, so they would float on the surface with a locator beacon.
Another possibility would be to require that planes, just before crashing, transmit crucial data, including airspeed, altitude, pitch and whether the engines were operating.
NTSB director of research and engineering Joe Kolly said on Thursday it was possible to automatically send such information if something catastrophic went wrong with the plane.
While the board said the technology was available, cost might be a barrier to its recommendations. Missing planes are rare, and none of the recent ocean crashes in which planes were hard to find involved US airliners.
Many airliners already have flight-tracking devices. The Malaysia Airlines Boeing 777, which remains missing, was equipped with a digital data-link system that can be configured to automatically report aircraft position periodically via satellite. But the airline was not paying for that service when the plane disappeared.
Air France flight 447, which crashed into the Atlantic Ocean on June 1, 2009, killing 228 passengers and crew, also had such a system, and it was in use. However, it was configured to report the plane's position once every 10 minutes. Given the plane's speed and altitude, this resulted in a search area of 40 nautical miles from its last reported position.
"Such a large area made the search much more challenging," the board said in a letter to the FAA.
Even though some flight 447 wreckage was discovered within days, it took nearly two years before its black boxes were recovered. In 2011, Air France modified its data-link communications systems on certain long-haul planes to report their position every minute.
Other options include systems that continually broadcast their identification, current position, altitude and speed to air traffic controllers and other aircraft using satellite links.
The FAA has required that all US airliners be equipped with such systems by 2020 as it transitions from a radar-based air traffic control system to one based on satellite technology, although some airlines have complained that they need more time.
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