Did you ever wonder how airplane "black boxes" survive devastating crashes?

By David McClelland

Again and again, we learn of horrible airplane crashes which are so bad that there are few, if any, survivors. Yet, in every case of which I am aware, the "black box" always remains intact, providing valuable information for investigators. The real name of the box is the Flight Information Data Recorder (FIDR) and it is painted orange, not black, for visibility.

Some wonder why they don't make the entire airplane out of the same material. The answer to that question is that it would make the aircraft too heavy. The FIDR is made of three boxes. The first is made of hardened stainless steel or titanium. The second is an insulation box. The third is a thermal block. The manufacturers put the boxes together with its "brain" inside the first box, which is placed inside the second and the second inside the third.  They make FIDR's to last. Each must survive a plane crash and function almost forever after that.

The "brain" of the box is the data storage unit, which is a magnetic tape or a memory board similar to that in your computer. Technicians mount the memory board in a thick thermal board, which sits inside an insulating box, which sits inside an armored capsule. The exterior of FIDR typically measures 5 x 6 x 9 inches, a little larger than a six-pack of Coke, and weighs about nine pounds.

What about heat and salt water? The manufacturers make the boxes so that they will withstand temperatures up to 2,000 degrees Fahrenheit. The box will also withstand being in salt water 20,000 feet deep for up to 30 days. The box also sends out a "pinging" signal to make it easier to find.

Finally, what data is recorded? The audio environment of the cockpit is recorded; i.e., every word spoken and every word received over the headsets of the cockpit crew, as well as ambient sounds. The FIDR also records all electronic instructions sent to the aircraft and the performance parameters of the aircraft. All of this data can be invaluable to investigators tasked with determining the cause(s) of the crash. This analysis can identify changes that are required in future aircraft design.