HAZMAT in the Skies

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.


PackagingOxygen generators are improperly placed in a forwardcargo compartment. A fire starts, and the airplane is destroyed. No one waskilled when this happened to an American Trans Air DC-10 on the ground inChicago in 1986, but the lesson went unlearned. Ten years later, oxygengenerators fueled the fire that led to the ValuJet Flight 592 crash into theFlorida Everglades on May 1996, focusing national attention briefly on thetransportation 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 inspectioncrusade over the past four years. The FAA now has five times the HAZMAT staff itdid before ValuJet 592, and has collected more than $14 million in fines overthe past three years. Although the FAA’s crackdown is aimed mostly at shippersand commercial carriers, it’s important to realize that the same HAZMAT rulesapply to each and every one of us while flying. It doesn’t matter if the flightis conducted under FAR Part 91, Part 135, or Part 121. The main concern for theaverage Joe should not be a potential FAA fine, however — it’s what can happenif you’re oblivious to your cargo. Much of the hazard comes from luggage orcargo 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 oneof its cargo containers was never entirely explained by the NTSB, but wasprobably caused by flammable liquids in a lab machine that was not identified ashazardous freight.

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

What Are The Hazards?

Common, Everyday Materials…

Like many problems in aviation, a HAZMAT disaster is often something we do toourselves. For those who are saying to themselves, "I’d never carry fuel inthe passenger compartment," other hazards may be lurking among those looseitems in the back of the plane. Pilot-owned aircraft tend to accumulate extrapayload with the passing of time, just as certainly as desiccated French friesgrow under the seats of the family car. Investigating the explosion of a Cessna172 at a low altitude, the NTSB traced the probable cause to fumes from acontainer of TCP. A very volatile and flammable organic solvent, TCP is a fueltreatment that the pilot had probably hauled around for many flight hourswithout 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 ofdirect toxic effects. Agricultural application pilots are well aware of theserisks, even though the loads carried in their hoppers are technically exemptfrom HAZMAT regulations. Ag-pilots might be reluctant to admit it, but some ofthem carry an atropine antidote when they are applying organophosphatepesticides. They base their self-dosing on how "drooly" they are.Organophosphate pesticides are in the same chemical family as the nerve agentsstockpiled by Iraq before the Persian Gulf War, and exposure can cause nervoussystem 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 becarried on any flight is regulated. Dry ice becomes carbon dioxide vapor, and abuild-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 transportfrozen steaks or other cargo likely to contain dry ice in a small aircraft, youshould get a safety "reality check" from an experienced shipper oraeromedical professional. Theoretically, small pressurized aircraft present agreater 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 foreven airline-size planes if the load is great enough. In 1998, a DC-8 freighterin Dallas was forced to taxi back and abort its takeoff after the entirecockpit crew was overwhelmed by carbon dioxide buildup from a cargo of dry ice.

BiohazardInfectious agents and radioactive materials are often problems for commercialHAZMAT cargo carriers, but represent delayed risks and are unlikely to cause anin-flight incident. These agents are more apt to cause grave concerns amongground cargo crews, or anyone who might have been inadvertently exposed to themat the airport. I encountered this scenario while managing the Logan Airportmedical facility in Boston, when a carton of live HIV (AIDS virus) appeared tobe leaking in transit. The box was ultimately determined to be wet only on theoutside, without any rupture of contents, but this information wasn’t availableuntil it was unpacked at a special laboratory. General aviation pilots areusually spared this kind of anxiety, but if your sneezing first officer with theflu has not had the sense to ground himself, he’s both an infectious diseaserisk 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 theshoulders of the commercial carriers and individual pilots, no matter how sneakyor ignorant the traveling public may be. Since 1994, all airlines, airports, andshippers have been required to display very prominent placards warning againstHAZMAT on commercial flights, threatening fines up to $25,000. All flights areforbidden by DOT Hazardous Material Regulations (HMR, 49 CFR Part 175) fromcarrying anything even remotely hazardous, although 175.10 lists manyexceptions (such as small aerosol cans and elaborately packaged wheelchairbatteries). There is even a regulation to "allow" a person to board anaircraft after they have been injected with a tiny amount of radioactive tracerfor a medical test (like a bone scan or Thallium treadmill test!) Yes, even theextra 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 fortransport on an aircraft meet requirements for container, labeling and quantitythat are material-specific. The FARs require each commercial operator tostructure their operations manuals to ensure everyone is trained to meet thisHMR Part 175 standard, but the details are left up to each operator.Unfortunately, at least for the airlines, the questions passengers are asked atthe ticket counter are directed entirely toward terrorism and bombs, to thedetriment of "Do you have any lighter fluid in your bags?" Every pilotin command should take a moment to ask the appropriate questions of passengersboarding the aircraft. A partial list of common hazards that are frequentlyreported as causing trouble, or forbidden by HMR Part 175, is shown in the tablebelow.

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 someoneelse’s mistakes. These reports are limited by definition to incidents oraccidents that have met NTSB notification criteria, as set forth in NTSBregulations (Part 830). It is also useful, in the best tradition of hangarflying, to learn from incidents where the crew was able to avert disaster andavoid becoming a headline. One source of such information is the Department ofTransportation’s Research and SpecialProjects Administration (RSPA), which compiles data on incidents involvingthe transportation of hazardous materials by all modes, including air. I used this database to obtain a broader picture of in-flight incidents ornear-disasters that were caused by hazardous materials. These reports areadmittedly slanted towards larger operations that have better mechanisms fortracking and reporting such events. It could also be argued that they have moreincentive to report, since their size makes their activities a much biggertarget for official scrutiny. Reports made to the NASAAviation Safety Reporting System (ASRS) also offer insight into disastersthat could have happened.

HAZMAT workersIn two years of RSPA reports, 2.5 percent of the almost 500 HAZMAT-by-airincidents involved emergency actions by the crew, such as diversion to analternate 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 emergencieswhile taxiing, or in the immediate post-flight period. Nearly half of theseevents were caused by cargo not identified as hazardous. Many examples of theseso-called "hidden shipments" were items buried wittingly orunwittingly in passenger luggage.

The 1988 loss of an American Airlines DC-9 was caused by this kind of packagein the cargo hold. An improperly packed drum containing hydrogen peroxide and aproduct for "stone washing" jeans was not declared as a hazardousshipment, 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 theinjuries were minor, but the plane was destroyed.

…The Lessons…

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

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

…And Murphy

FlammableSources of combustion are guaranteed to be both unpredictable andinconvenient. The ASRS recently reported incidents that prove a corollary toMurphy’s Law — if a source of combustion can light off, it will. The jugglingof luggage can produce enough friction to cause kitchen matches to ignite, whichwill leave the back of your family cruiser in sad shape. One pilot of a Cessna172 reported that a spare nine-volt battery he had packed for his headset hadshorted out across the metal of a zipper. He was fortunately able to reach thebag and put out the fire before it got out of control. A Cessna 182 pilotreported an explosion in his baggage compartment caused by an overheatednine-volt alkaline battery that had shorted out on a piece of metal in hisflight case.

The majority of non-incendiary HAZMAT events in the study involved leaky ordamaged containers. Some of the incidents were caused by serious chemicaltoxins, such as hydrogen sulfide trapped in a shipment of oil field gear. Thiswas reported twice, and in one case sent seven ground crew to the hospital whenthey opened the hold.

Many reported incidents in the RSPA database were caused by odors emanatingfrom leaky cargo packages that, in retrospect, did not represent a serious toxichazard to the crew. Nonetheless, pilots generally have no way to distinguishbetween a smell that is merely obnoxious and an odor that represents a serioushazard. The crew is usually compelled to take emergency action when strangeodors start wafting in from the back. The flight crew’s options at that pointare limited: Increase cockpit ventilation (if possible), don oxygen masks andsmoke 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 afew 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.