HAZMAT in the Skies

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In the aftermath of the ValuJet 592 tragedy, carriage of hazardous materials HAZMAT aboard airliners has received a great deal of attention. But what about other operations? When you preflight your aircraft, do you consider what you and your passengers are bringing, along with the weight? AVweb's Kim Broadwell examines current regulations as well as several recent HAZMAT incidents aboard aircraft large and small.

Packaging Oxygen generators are improperly placed in a forward cargo compartment. A fire starts, and the airplane is destroyed. No one was killed when this happened to an American Trans Air DC-10 on the ground in Chicago in 1986, but the lesson went unlearned. Ten years later, oxygen generators fueled the fire that led to the ValuJet Flight 592 crash into the Florida Everglades on May 1996, focusing national attention briefly on the transportation of hazardous materials (HAZMAT) by air.

ValuJet logoHAZMAT's public "infamy" may have passed until the second accident, but in the wake of the ValuJet crash the FAA has gone on a HAZMAT inspection crusade over the past four years. The FAA now has five times the HAZMAT staff it did before ValuJet 592, and has collected more than $14 million in fines over the past three years. Although the FAA's crackdown is aimed mostly at shippers and commercial carriers, it's important to realize that the same HAZMAT rules apply to each and every one of us while flying. It doesn't matter if the flight is conducted under FAR Part 91, Part 135, or Part 121. The main concern for the average Joe should not be a potential FAA fine, however — it's what can happen if you're oblivious to your cargo. Much of the hazard comes from luggage or cargo that is not identified or handled as "dangerous." For example, the complete destruction of a FedEx DC-10 in 1996 by a fire that erupted in one of its cargo containers was never entirely explained by the NTSB, but was probably caused by flammable liquids in a lab machine that was not identified as hazardous freight.

Air carrier accidents grab national headlines, but HAZMAT problems are not the exclusive territory of the "big guys" of aviation. Ask the pilot of a Cessna Skymaster whose plane caught fire while landing — his passenger had attempted to right an overturned gasoline can, while holding a burning cigar in his hand. In the larger scheme of general aviation accidents, problems with hazardous materials cargo are not as significant as more familiar causes, such as continued flight into bad weather, controlled flight into terrain, or fuel exhaustion. On the other hand, if your cargo bites you in-flight, such statistics become irrelevant. A prudent pilot needs to be familiar with HAZMAT concerns.

What Are The Hazards?

Common, Everyday Materials...

Like many problems in aviation, a HAZMAT disaster is often something we do to ourselves. For those who are saying to themselves, "I'd never carry fuel in the passenger compartment," other hazards may be lurking among those loose items in the back of the plane. Pilot-owned aircraft tend to accumulate extra payload with the passing of time, just as certainly as desiccated French fries grow under the seats of the family car. Investigating the explosion of a Cessna 172 at a low altitude, the NTSB traced the probable cause to fumes from a container of TCP. A very volatile and flammable organic solvent, TCP is a fuel treatment that the pilot had probably hauled around for many flight hours without a second thought.

Air TractorBesides the risk of explosion, smoke or fire, a cargo of dangerous goods (another term for HAZMAT) can potentially incapacitate the crew because of direct toxic effects. Agricultural application pilots are well aware of these risks, even though the loads carried in their hoppers are technically exempt from HAZMAT regulations. Ag-pilots might be reluctant to admit it, but some of them carry an atropine antidote when they are applying organophosphate pesticides. They base their self-dosing on how "drooly" they are. Organophosphate pesticides are in the same chemical family as the nerve agents stockpiled by Iraq before the Persian Gulf War, and exposure can cause nervous system problems in humans, as well as the intended insect targets.

...And Others Not So Common

Keep frozenDry ice is an example of a more subtle risk, and the amount that may be carried on any flight is regulated. Dry ice becomes carbon dioxide vapor, and a build-up of this gas in a cabin can cause medical problems for both aircrew, passengers, and in some cases, animal cargo. If someone asks you to transport frozen steaks or other cargo likely to contain dry ice in a small aircraft, you should get a safety "reality check" from an experienced shipper or aeromedical professional. Theoretically, small pressurized aircraft present a greater opportunity for CO2 accumulation than an unpressurized or larger plane, because of less air circulation in the cabin, but dry ice can be a problem for even airline-size planes if the load is great enough. In 1998, a DC-8 freighter in Dallas was forced to taxi back and abort its takeoff after the entire cockpit crew was overwhelmed by carbon dioxide buildup from a cargo of dry ice.

BiohazardInfectious agents and radioactive materials are often problems for commercial HAZMAT cargo carriers, but represent delayed risks and are unlikely to cause an in-flight incident. These agents are more apt to cause grave concerns among ground cargo crews, or anyone who might have been inadvertently exposed to them at the airport. I encountered this scenario while managing the Logan Airport medical facility in Boston, when a carton of live HIV (AIDS virus) appeared to be leaking in transit. The box was ultimately determined to be wet only on the outside, without any rupture of contents, but this information wasn't available until it was unpacked at a special laboratory. General aviation pilots are usually spared this kind of anxiety, but if your sneezing first officer with the flu has not had the sense to ground himself, he's both an infectious disease risk as well as a hazard to safe flight.

The Regs

RSPA logoThe government places the responsibility for not accepting "improper" hazardous materials aboard aircraft squarely on the shoulders of the commercial carriers and individual pilots, no matter how sneaky or ignorant the traveling public may be. Since 1994, all airlines, airports, and shippers have been required to display very prominent placards warning against HAZMAT on commercial flights, threatening fines up to $25,000. All flights are forbidden by DOT Hazardous Material Regulations (HMR, 49 CFR Part 175) from carrying anything even remotely hazardous, although 175.10 lists many exceptions (such as small aerosol cans and elaborately packaged wheelchair batteries). There is even a regulation to "allow" a person to board an aircraft after they have been injected with a tiny amount of radioactive tracer for a medical test (like a bone scan or Thallium treadmill test!) Yes, even the extra quart of oil you carry in your plane is probably illegal unless it is "properly packaged and labeled."

What the HMR regulations actually demand is that any HAZMAT accepted for transport on an aircraft meet requirements for container, labeling and quantity that are material-specific. The FARs require each commercial operator to structure their operations manuals to ensure everyone is trained to meet this HMR Part 175 standard, but the details are left up to each operator. Unfortunately, at least for the airlines, the questions passengers are asked at the ticket counter are directed entirely toward terrorism and bombs, to the detriment of "Do you have any lighter fluid in your bags?" Every pilot in command should take a moment to ask the appropriate questions of passengers boarding the aircraft. A partial list of common hazards that are frequently reported as causing trouble, or forbidden by HMR Part 175, is shown in the table below.

Common HAZMAT Troublemakers

  • Butane cigarette lighters or other lighters with "flammable liquid reservoirs."

  • Any kind of lighter refill.

  • Refills for butane curling irons.

  • Standard "spillable" lead-acid batteries (often attached to an electric wheel-chair and not noticed).

  • Large aerosol cans (like spray paint).

  • Compressed gas cylinders, such as scuba tanks or welding equipment.

  • Machines or machine parts that may contain flammable liquids (e.g., fuel left in chainsaws, generators, and other powered equipment).

  • Improperly packaged firearms or ammunition.

  • Common household chemicals: solvents, bleach, cleaners, paint.

  • Improperly packaged mercury-filled barometers and thermometers.

  • "Strike-anywhere" matches.

Learning From The Misfortunes Of Others

The Resources...

NTSB reports are valuable to pilots trying to avoid the repetition of someone else's mistakes. These reports are limited by definition to incidents or accidents that have met NTSB notification criteria, as set forth in NTSB regulations (Part 830). It is also useful, in the best tradition of hangar flying, to learn from incidents where the crew was able to avert disaster and avoid becoming a headline. One source of such information is the Department of Transportation's Research and Special Projects Administration (RSPA), which compiles data on incidents involving the transportation of hazardous materials by all modes, including air. I used this database to obtain a broader picture of in-flight incidents or near-disasters that were caused by hazardous materials. These reports are admittedly slanted towards larger operations that have better mechanisms for tracking and reporting such events. It could also be argued that they have more incentive to report, since their size makes their activities a much bigger target for official scrutiny. Reports made to the NASA Aviation Safety Reporting System (ASRS) also offer insight into disasters that could have happened.

HAZMAT workersIn two years of RSPA reports, 2.5 percent of the almost 500 HAZMAT-by-air incidents involved emergency actions by the crew, such as diversion to an alternate destination, deployment and use of oxygen masks, expedited landings, or aircraft evacuations. Another 3.5 percent of occurrences were close calls, with pilots and ground crews identifying fires, smoke, or other emergencies while taxiing, or in the immediate post-flight period. Nearly half of these events were caused by cargo not identified as hazardous. Many examples of these so-called "hidden shipments" were items buried wittingly or unwittingly in passenger luggage.

The 1988 loss of an American Airlines DC-9 was caused by this kind of package in the cargo hold. An improperly packed drum containing hydrogen peroxide and a product for "stone washing" jeans was not declared as a hazardous shipment, and was loaded in the cargo hold on its side. The shipment leaked, starting a serious fire shortly before the flight landed in Nashville. All the injuries were minor, but the plane was destroyed.

...The Lessons...

Within my study period, one clerk in Alaska did avert a potential problem by questioning a woman about the bright orange rope she had tied around her package for air shipment. The string she had conveniently found in her husband's tool shed turned out to be blasting cord! This illustrates another theme running through the HAZMAT incident reports: People in the Alaskan bush are likely to ship anything and everything by air, including chainsaws loaded with gasoline. One hidden shipment from Homer, Alaska, to Tucson, Ariz., contained undeclared fireworks, gunpowder, propellants and a tank of acetylene welding gas.

Sometimes poor maintenance and bad luck will catch up with a pilot at the same time, as in the case of an air taxi pilot whose plane caught fire while delivering fuel at a remote landing strip. He was able to land and put out the fire, which was being fueled by a leaking drum. A charred wire beneath the floorboard identified the ignition source: The lower rotating beacon had been removed in the past, but when the cockpit panel beacon switch was activated the old wiring was still "hot."

...And Murphy

FlammableSources of combustion are guaranteed to be both unpredictable and inconvenient. The ASRS recently reported incidents that prove a corollary to Murphy's Law — if a source of combustion can light off, it will. The juggling of luggage can produce enough friction to cause kitchen matches to ignite, which will leave the back of your family cruiser in sad shape. One pilot of a Cessna 172 reported that a spare nine-volt battery he had packed for his headset had shorted out across the metal of a zipper. He was fortunately able to reach the bag and put out the fire before it got out of control. A Cessna 182 pilot reported an explosion in his baggage compartment caused by an overheated nine-volt alkaline battery that had shorted out on a piece of metal in his flight case.

The majority of non-incendiary HAZMAT events in the study involved leaky or damaged containers. Some of the incidents were caused by serious chemical toxins, such as hydrogen sulfide trapped in a shipment of oil field gear. This was reported twice, and in one case sent seven ground crew to the hospital when they opened the hold.

Many reported incidents in the RSPA database were caused by odors emanating from leaky cargo packages that, in retrospect, did not represent a serious toxic hazard to the crew. Nonetheless, pilots generally have no way to distinguish between a smell that is merely obnoxious and an odor that represents a serious hazard. The crew is usually compelled to take emergency action when strange odors start wafting in from the back. The flight crew's options at that point are limited: Increase cockpit ventilation (if possible), don oxygen masks and smoke goggles (if available), and land as soon as practicable.

The Sermon

What can a careful pilot learn from the bad experiences of others? Here are a few tips for preventing problems with hazardous materials:

  • Maintain a healthy paranoia about all cargo loaded on your aircraft, including baggage contents and how they are packed. As you perform your pre-flight weight and balance calculations, ask your passengers what they are bringing with them, in addition to considering the weight.

  • Leave spare batteries in the original packaging, or use well-secured terminal protectors.

  • Take the time to tie down and secure cargo. We all know this protects against flying missiles in turbulence, but proper tie-down is also insurance against upsetting a poorly packed hazard.

  • Lastly, but probably the most important: Don't ask for trouble — carrying fuel anywhere other than the fuel tanks is a big risk. Be sure and check any cargo (like camp stoves) that might contain residual gasoline or other flammable liquid.

Usual Disclaimer: This article is intended as a safety advisory for pilots, and is based on data published by the National Transportation Safety Board, the Aviation Safety Reporting System, and the Research and Special Programs Administration's Hazardous Material Information System. It is not intended to judge or reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.