The National Transportation Safety Board (NTSB) says that fire protection regulations on cargo aircraft are "inadequate" and has issued a letter with three recommendations for how to reduce in-flight fires to the Federal Aviation Administration (FAA).
The NTSB is calling on the FAA to require fire suppression systems in all cargo containers and compartments. It also recommends implementing requirements to detect fires in cargo containers and pallets earlier, as well as developing standards for cargo container materials.
The NTSB has investigated three major in-flight cargo fires in the past six years, two of them fatal.
The NTSB says in February 2006, a United Parcel Service (UPS) Boeing DC-8 suffered damage after crews landed in Philadelphia after receiving an indication of cargo smoke. A preliminary report from the United Arab Emirates General Civil Aviation Authority showed that in September 2010, two crewmembers died when a UPS Boeing 747-400 freighter crashed outside of Dubai International Airport after crews received a fire main deck warning 22 minutes into the flight.
In July 2011, an Asiana Cargo Boeing 747-400 freighter fatally crashed into the East China Sea after a crew discovered a cargo fire and tried to divert to Jeju International Airport. Preliminary findings from Korean investigators showed that only 18 minutes had elapsed between when the fire was detected and when the aircraft was lost.
The NTSB says in the letter that in the last two incidents, only a short period of time elapsed between when crews were alerted of the fire and when aircraft systems started to fail.
"These fires quickly grew out of control, leaving the crew with little time to get the aircraft on the ground," said NTSB Chairman Deborah Hersman in a statement. "Detection, suppression and containment systems can give crews more time and more options. The current approach is not safe enough."
The NTSB ran tests to investigate the time it took for an aircraft smoke detection system to identify fires within two types of cargo containers. It found that the detection time ranged between 2min 30s to 18min 30s. Based on that data, NTSB says that not much time elapses between a smoke detection system identifying a fire and when it could reach the aircraft's structures.
NTSB's study also shows that smoke can be concealed within a pallet for a long time before a smoke detection system picks up on it, therefore reducing the amount of time the crew has to make emergency preparations before it takes over the system controls.
The NTSB says that under existing FAA regulations, materials used to construct cargo containers must undergo a "horizontal Bunsen burner test", but under this procedure highly combustible materials can still be used. The board cites collapsible containers made of corrugated polypropylene as a major contributor to the intensity of a fire. Therefore, the NTSB recommends that cargo containers are subject to the same flammability requirements as cargo compartments.
UPS says it has been working with the NTSB, FAA, its pilots union and the Independent Pilots Association to implement more safety measures in the cockpit and in the main cabin to prevent fires from starting. Some of those measures include installing an emergency vision assurance system for pilots to better see instruments through smoke as well as retrofitting its Boeing fleet with full-face oxygen masks and integrated smoke goggles.
UPS has also begun testing unit loaded devices with new materials and door configurations and has built a steel container to test fire suppressant agents. On 23 October, the airline tested a unit load device at with 215 packages by setting it on fire with lithium batteries and suppressed the fire for four hours. It also uses fire containment covers for palletized cargo that can contain a fire for the same period of time at temperatures of up to 1,500 degrees.
FedEx has also taken steps to install a fire suppression system on its MD-11 freighters and new Boeing 777 freighters, which uses a network of heat-seeking sensors to detect fires caused by paper of lumber, gasoline and kerosene and combustible metals.