Guest Analysis: Aircraft Black Box Survivability

By David Luke

Date: September 26, 2001

Note:  The black box that I discuss below is one that I had dissected at a friends alloy recovery center. This was about 8 years ago. It (the black box) got there for one of several possible reasons -- i.e., the box quit working, upgrades / replacements, or advancements.  This technology was very stable, but time moves on and quite probably left this technology behind.  I cannot say with certainty that the metal film is still being used.  I must also state that I am unfamiliar with the newer and what appears to be less "survival friendly" technologies claimed to be in use today.

Over the last 25 years I have worked on "hot section" parts in the aerospace industry.  These parts have this name because of where they perform -- in the hot section of jet engines. They are high nickel/cobalt alloys. Their benefit is that they retain the majority of their strength characteristics at extremely high temperatures -- temperatures that would turn normal steel plastic or even liquid. These are the alloys that are used in the manufacture of the so-called aircraft "black boxes" and the recording medium inside of them.

Very well, you say, but so what?  There is more to it...

I have seen these black boxes as well as their contents.  They are incredibly simple, but also incredibly ingenious.  Picture a pile of newspapers or magazines thrown away and in the dump.  Twenty-five years later, the inner pages can still be read.  The same is true for magazines or papers in a fire, only the outer edges are damaged while the inner pages are often well preserved.

And these objects are only made of paper.

On the other hand, black boxes are made of extremely strong and resilient materials and designed to withstand every conceivable possibility for destruction. More importantly, the material that holds the information is not what the FBI would like you to know about. This material will survive even if the black box is TOTALLY DESTROYED (which in itself is highly unlikely by design).

These materials, high temperature nickel alloys, are some of the most indestructible materials known to man. They can take temperatures over 2000 Deg. F. and never know that they have been hot!  They can survive salt water immersion for a lot longer (years) than would ever likely happen in an accident investigation where they are usually found within a few days.

But most importantly, the recording medium is not simple tapes or cassettes made of plastic, but thin strips of this "hot-section" type "super" alloy. The same type used in the afterburner sections of the F-15's and F-16's -- the parts that get white hot, over, and over, and over and still keep on working.

But, and here is the beginning of what is truly brilliant, they are marked with a stylus not so much different than that of our old 33 1/3 vinyl albums, but in reverse. The information is scribed onto this alloy along with timing "nicks" for time/date reference.

Here comes the good part: Now, the marked strip is "rolled" up into a continuous roll of high temperature alloy. The tight circular roll now resembles a solid. A solid piece of material that by design protects itself by only allowing the EDGES of the roll to be exposed to damage -- THE DATA ITSELF IS SAFE IN THE CENTER OF THE STRIP.  So designed, the mass of the continuous rolled strip shields the "whole" from damage.

What we have is a nearly indestructible roll of material with its data stored neatly and safely inside of a nearly indestructible box that, in some ways, is not unlike the magazines or newspapers thrown away in dumps that last forever -- papers that survive years of exposure and can still be read but are are still merely paper.

Now keep in mind that the FBI finds bomb parts and detonators after blasts; parts that were meant to be consumed -- certainly, perpetrators hope them to be destroyed, leaving no trace.  Yet Black Boxes were meant to be FOUND with information kept inside and INTACT.

So, when the FBI tells us that the boxes were nearly destroyed -- you can think, "This is possible"... BUT, during the highly unlikely event of box's near destruction, it is doing what it is designed to do -- the casing absorbs energy to protect the metal roll that by design is nearly indestructible by itself.

So when flight recorders come up blank, I ask the question, "NO DATA... For Whom?"


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