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Black Box

In designing an object an engineer must choose the proper material. Never is this more important than in the "black box" flight data recorder.

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Transcript If an airplane goes down, its the infamous black box that gives us information about the plane's speed and altitude before the crash. So, how do you make something that can record all that information, but still withstand impact 3000 times the force of gravity, and temperatures of up to 1000 degrees celsius?

Well, the answer isn't this flimsy outer casing, but instead it's this framework and especially the magazine held inside. This is made from steel, see here the delta airlines logo - I bought this on ebay for about 100 bucks.

The magazine shows the key component that allows the black box to record information so consistently and durably: Inconel steel. This metallic foil records flight parameters. They're engraved, or scratched on to this inconel sheet. In fact the real name for this device is a "foil oscillographic recorder."

Now tucked away in the black box we see instruments that measure altitude and airspeed.. they're right here.

Two other instruments are even tucked away in the black box they measure magnetic heading and vertical acceleration. Now look through the front and you can see a small arm attached to each instrument.

A very tough piece of metal on the tip cuts the gauge's readings into the roll of metal in the magazine. This system of gears move the foil at six inches per hour - a spool is two hundred feet long, meaning it can record 400 hours of footage, as you can see here on this gauge.

The key to making the black box work is the inconel metal used in the magazine. Typically used in furnaces, it is resistant to corrosion and oxidation, and when it is heated to high enough temperatures, it forms an oxide layer that protects the surface from further attack.

Now, today's Black Boxes are typically solid state, and, of course, digital, but, you know I still love these old flight data recorders - the show the ingenuity of the engineers in using inconel steel in the magazine, one of the few substances that could do the job. I'm Bill Hammack, the engineer guy.