黑匣子的工作原理

A possible break in the mystery of the missing Malaysia Airlines Flight 370 plane came when ships detected "pings" consistent with the aircraft's black box. But how does a black box actually work?

Black boxes, or flight recorders, are electronic devices that record information on an airplane to be used in the event of a severe incident such as a crash. Usually, an aircraft carries two types of recorders.

The first, a flight data recorder, makes a record of instructions sent to a plane's electronic systems; the second, a cockpit voice recorder, makes a record of conversations, radio communications and other sounds in the cockpit. Sometimes, the recorders are part of the same unit.

Black boxes, which are actually bright orange, are designed to withstand extreme forces and temperatures, and are usually located in the tail of the aircraft, where they are least likely to encounter an impact.

Clues to missing flight

The recorders could offer clues about what happened to Malaysia Airlines Flight 370, which disappeared enroute from Kuala Lumpur to Beijing on March 8, with 239 people on board. Investigators have been searching for the plane in the southern Indian Ocean west of Australia, where satellite data suggests the aircraft may have crashed.

The black boxes emit underwater locator beacon signals, or pings, at depths of up to 20,000 feet (6,000 meters), for up to 30 days before their batteries die.

An Australian navy ship picked up signals with the same frequency as those emitted by the missing plane's black boxes in the northern part of the search area, officials announced Monday (April 7), according to CBS News. The ship Ocean Shield heard the pings from a towed pinger locator. The first series of pings lasted two hours and 20 minutes, and a second signal lasted for 13 minutes.

A Chinese ship also reported hearing pings consistent with a plane's recorder signals on Friday and Saturday (April 4 and 5), according to Xinhua, China's official news agency. This ship heard pings about 345 miles (555 kilometers) away from those detected by the Australian ship.

Awaiting confirmation

But investigators have yet to confirm the pings came from the missing aircraft. Sea life (such as whales) and shipping noise can trigger false alerts. Last week, a British Royal Navy ship called the H.M.S. Echo detected signals that sounded like those from a black box, Australian officials reported, but the signals were false, according to The New York Times.

The Australian and Chinese ships will attempt to detect the pings again. If they do, they will probably deploy underwater robots to search for plane wreckage on the seafloor, a mission that could take many days, investigators said. The black box pinger has a range of only a few miles. And the black box itself is small and doesn't float, so it could be tough to locate.

Finding the flight recorders and the plane's wreckage would provide confirmation that the flight crashed, but the recordings themselves may not be able to resolve the causes of the crash.

The flight voice recorder only stores the most recent two hours of flight, but the key events in the Malaysia Airlines flight may have taken place earlier, officials have said. The flight data recorder would be much more useful, however, because it may allow investigators to reconstruct the flight path, a former pilot told BBC News.據Livescience網站報道，搜尋船隻探測到疑似客機黑匣子的脈衝信號，這是失聯航班MH370謎團中一個重大突破。但是黑匣子到底如何工作？

黑匣子，或稱飛行記錄器，是一個電子設備，用於在飛機上記錄信息以備重大事故時使用，如墜機。通常飛機會裝有兩種類型的記錄器。

一種是飛行數據記錄器，記錄發送到飛機電子系統上的指令；另一種是駕駛艙話音記錄器，記錄艙內對話，無線電通信以及其他聲音。有時候，這兩種記錄器是同一設備的不同部分。

黑匣子實際上是亮桔色，可以承受極端力量和溫度。黑匣子通常位於機尾，那裏受到直接衝擊的可能性最小。

失聯航班線索

這兩個記錄器可以提供與載有239名乘客的馬來西亞航班370的相關線索：飛機爲何會在吉隆坡飛往北京的途中失聯？在澳大利亞以西的南印度洋海域已經展開調查，那裏的衛星數據顯示飛機可能已經墜毀。

黑匣子可在深達2萬英尺（約6000米）的水下發出水下定位信標信號，或者說脈衝信號。電量可維持30天。

據哥倫比亞廣播公司新聞4月7日消息，當天澳方官員宣佈，一艘澳大利亞軍艦在搜尋區域北部接收到失聯客機黑匣子頻率相符的水下信號。這艘“海洋之盾”號軍艦由一個拖曳式“黑匣子”水下探測設備監聽到信號。第一次信號持續了大約2個小時20分鐘，第二次信號持續了13分鐘。

中國官方通訊社新華社報道，一艘中國船隻也報告稱於週五和週六（4月4日和4月5日）監聽到與飛機記錄器頻率一致的脈衝信號。這艘船隻監聽到信號的地點離澳方船隻相距555千米。

等待確認

但是調查員還在確認這些信號是否來自失聯航班。海洋生物（例如鯨魚）以及船舶噪音同樣可引發錯誤的警報。上週，一艘名爲英國皇家海軍“回聲號”軍艦探測到疑似黑匣子發出的脈衝信號，而據《紐約時報》報道，澳大利亞官方報告稱這個信號並非黑匣子所發出。

調查人員說，澳大利亞以及中方軍艦嘗試再次探測到脈衝信號。如果再次探測到信號，他們可能將部署水下機器人在海底搜尋飛機殘骸，這一任務可能需要很多天。黑匣子脈衝發射器的發射範圍只有幾英里。並且黑匣子本身很小，不會漂浮,所以很難找到它。

找到黑匣子和飛機的殘骸可以確認飛機墜毀，但記錄本身可能無法提供墜機的原因。

官方稱，飛機語音記錄器僅儲存航班最近兩個小時的飛行記錄，但馬來西亞航空公司失聯航班上的關鍵事件可能在此之前就已經發生。一位前飛行員告訴BBC記者，飛行數據記錄器將更有用，因爲它能讓調查人員重構飛行路徑。