Aircraft Accidents and Depleted Uranium

Hollywood has the uncanny ability to remove all realism from just about everything.  Their perception of the mechanisms of an aircraft accident, e.g. the mid-ocean disaster of the FedEx MD-11 in Cast Away is designed more to aid the shot than actually depict the hazards of an actual accident.  Chuck Noland (Tom Hanks’s character) ends up outside the crashed MD-11 in the ocean, surviving the impact, yet almost killed by a still operating #2 tail engine that slowly descends on him.

In Chuck’s case, it’s unlikely our hapless hero gets out of the fuselage unscathed, without getting sliced up on the jagged fuselage’s metal or turned to jelly by the incredible impact forces.  The ocean’s surface, where he’s treading water on, is mostly jet fuel and hydraulic fluid, two liquids that have a lower density than water and therefore float on the surface.  They give off noxious fumes; jet fuel can give a person second or third degree chemical burns, not to mention the damage they would do to his eyes and lungs.  Ironically, the only non-threatening item is the running #2 engine.  Why?  Well, you know that jet fuel feeding the engine?  Hapless Chuck has been splashing around in it on the ocean’s surface.  So, it’s safe to say that a movie set will be arranged for the most advantageous shot; aircraft debris is placed strategically to avoid shadows or block the actor’s close up.

So where am I going with this; what’s the point?  Aircraft accident scenes are very dangerous places.  Rescue workers/first responders face many dangers from the crashed aircraft and even the victims, themselves; things you would never consider hazardous upon arrival at an accident scene, e.g. American 587 in Belle Harbor, NY.

The Airbus A-300 fell onto a Queens neighborhood, killing several people on the ground.  Aside from the aircraft debris, there was concern over underground gas lines or unexploded automobile fuel in the neighborhood vehicles.  At Ground Zero, the dangers to first responders were more numerous, from the dust clouds generated during the Towers’ collapse to subway tunnels and sewer pipes below the surface.  However, these two disasters were unique in many ways, but they represent the unknown hazards in any disaster.

But all transportation accidents beget their own hazards, whether the mode is Marine, Rail, Highway or Pipeline; for the sake of my articles, I stick with Aviation.  Each accident, whether General Aviation or Commercial, is fraught with dangers to first responders.  To support the discussion, let’s put our imaginary accident scene in an empty field, miles from civilization; the origins of the risks to human safety would be limited to the accident aircraft and the victims within.  These hazards could be classified under three categories: Technological, Biological and Unexpected.  It is for these reasons that first responders and accident investigators are hopefully well protected by HAZ suits.

Technological hazards are those attributed to the aircraft; they are limited to those perils that one can expect to find and are therefore, usually, avoidable.  As mentioned earlier in the introduction, fuel plays an important part.  Fuel not consumed by post-crash fires could seep into the ground, giving off noxious fumes that can be ingested through the lungs or burn unprotected eyes from excessive exposure.  Any fuel that seeps into clothing can cause second and third degree chemical burns if not removed right away.  The fuel tanks that are breached can be a constant supply of more fume, until the sections are removed from the scene and isolated.

Jagged sections of aluminum and steel can be dangerous, piercing through the protective clothing or just cutting the human’s – or cadaver dog’s – skin with deep lacerations; these injuries could introduce other chemicals, e.g. hydraulic fluids or engine oils, directly into the interior of the body.  Carcinogenic fumes from burning aircraft fluids can be ingested into the lungs and directly into the bloodstream.  Broken or shattered composite materials can splinter; this makes these plastic fairings a danger to anyone without gloves; they can also be breathed in, introducing composite splinters directly into the lungs where it is impossible to expel.

Biological hazards are those related to the victims.  There are many harmful ailments carried by everyday people; diseases that, by themselves, are only limited to the host carrying them.  Since no one considers the worst, even the most careful carrier of, e.g. the Human Immunodeficiency Virus and Acquired Immune Deficiency Syndrome (HIV/AIDS) virus can end up being the victim of an aircraft accident.  Airborne Pathogens can be present at the smallest accident scene or a major accident scene.  Many that can survive the accident for hours, are a danger to first responders, e.g. medical personnel, local law enforcement or the farmer whose field the plane crashed in.  These people, who may come in contact with body parts, the victim’s seat or grasses near the accident site can be infected.  Since accidents often generate tremendous forces, the pathogens can be carried by the air or explosion for great distances.

Unexpected hazards are those that the most knowledgeable of first responders may not expect, e.g. Depleted Uranium (DU).  Though used in small quantities, DU or other ‘heavy’ metals are found in major airliners in places that no one would look; they are used as counterweights or balance weights.  Why?  Because of the amount needed for the job required.

Every airliner has primary flight controls (PFC): Ailerons, Elevators and Rudders.  When viewed from the side, each of these PFC airfoils resembles a teardrop: the rounded end, or leading edge (LE), is mounted forward in the direction of flight; the aft end tapers to a knife’s edge; this thinner end is called the trailing edge (TE).  Where the PFC swivels is the pivot point; it is only inches from the LE, yet several feet from the TE; this is because a majority of the PFC’s TE is used to ‘control’ the flow of air while the LE allows for swiveling inside a fairing in the wing, vertical or horizontal stabilizer.  One other caveat: these PFCs must be perfectly balanced or they will cause damaging vibrations, flutter or worse, e.g. departure of the flight control, altogether.  Every PFC must balance at the pivot point; the LE and TE must be in equilibrium.

Enter depleted uranium; DU is so dense that its weight to area ratio is very high; you only need a small amount to get the weight needed for balancing.  For instance, a block of depleted uranium 6 inches X 2 inches X 8 inches (96 square inches) can weigh close to two hundred pounds.  This smaller size can allow the PFC to swivel with less drag caused by an overly large counterweight.

Although enclosed and sealed in a lead casing, depleted uranium has been known to break down physically.  Back in 1990, my co-mechanic and I removed a counterweight off the upper rudder of a DC-10 for X-ray inspection of the attach bolts.  Although we were careful not to breach the lead casing, the bolts had already been damaged by contact with the DU, which had penetrated the casing and acted on three of the four attach bolts.  There was considerable danger from exposure.  Furthermore, the lead casing’s physical integrity had broken down, resulting in uranium ‘dust’, which could be inhaled or trapped in the oils of one’s skin.

This is the Unexpected hazard: exposure to the counterweights.  The casing doesn’t have to be compromised from time; instead it could be damaged from impact forces; the counterweight could be thrown free from the aircraft, the lead casing shell creased from collision with the ground … or something.  Oh, come on, you didn’t really think Indiana Jones actually survived a nuclear explosion hiding in a lead-lined refrigerator, did you?

It’s good that Hollywood creates ‘realities’ where stories, like Cast Away or Kingdom of the Crystal Skull, can be told.  If their desperate for ideas, I have two novels they can read, if they’re interested … just saying.  But I have always found that there is nothing Hollywood can dream up that is scarier than the non-fictional reality … of Reality.

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