Saturday, March 7, 2009

Black Box

As a frequent flier, I take quite an interest in the machinery used to get me from place to place. I took a couple of flight lessons and visited the Boeing factory in Everett, Washington twice (the first time, years ago, they were just rolling out the 777-200. More recently, they were hard at work on the 787 "Dream Liner").

One fact stuck in my mind from the last tour: every airplane is flown by test pilots for several hundred hours, before it's delivered to the airline that ordered it. During the test flights, the pilots simulate turning each one of the 4 engines off, and finally all 4 - to see how the plane would handle it. Talk about a job from hell - purposefully trying to crash a jumbo jet.

That and some recent accidents (and morbid curiosity) prompted me to read about the Flight Recorder, aka "Black Box". Here are some facts that might interest you, about a the only device on an airplane that is completely useless to its occupants:
  1. A black box is actually orange colored, so it'd be easier to find in a wreck.

  2. There are actually 2 flight recorders on every airplane. One records the flight data from all the gauges (FDR) and one records conversations in the cockpit (CVR).

  3. The recorders are placed in the tail of the aircraft, statistically the part of the plane that will survive most crashes (and to think I usually tell my travel agent to seat me up front).

  4. The recorders have a locator beacon to aid in their retrieval.

  5. The FDR records all the data points in the aircraft every 5 seconds, unless something goes wrong, and then it switches to 1 second or 0.2 second interval. It can hold up to 25 hours of data.

  6. The voice flight recorder retains the last 2 hours of conversations, using a cyclic buffer.
    Which brings up the question: with today's storage capacity and minimization, you can literally record hundreds of hours of flight data and voice without losing anything. Why isn't the technology upgraded?
In my opinion, the whole flight recorder aspect may be a bit outdated. With available wi-fi and radio technologies, you could, conceivably, transmit all data to several ground stations (for redundancy), so no on-board recorder will be needed (think about it: some of the airlines already have onboard wi-fi. Data can be easily transmitted). That way, many more people and much better computers on the ground can monitor planes in real time, and alert whenever something goes out of whack, long time before the pilots notice a problem (pro-active, rather than reactive, approach).

It's hard to put a number on how many accidents were prevented and lives saved due to lessons learned from black boxes salvaged from past accidents. From a pure, scientific point of view, this looks like one of the single instances in human progress where learning from past mistakes actually prevents repeating them.

Read more about flight recorders here.

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