WASHINGTON (AP) - The government should require fire suppression systems in all cargo containers or compartments of planes to prevent the kind of ferocious in-flight blazes that have killed four cargo pilots over the past six years, federal accident investigators said Wednesday.
The National Transportation Safety Board didn't specify what kind of technology the Federal Aviation Administration should require airlines to install. But the board's letter to the FAA came a day after United Parcel Service said it has developed systems that can prevent or contain even fires in shipments of lithium batteries, which burn at very high temperatures.
Lithium batteries are suspected to have caused or contributed to the severity of the fire in the crashes of a UPS jumbo freight airplane in Dubai in 2010 and an Asiana Cargo plane off the coast of South Korea in 2011. In 2006, two UPS pilots were able to escape a plane shortly after landing in Philadelphia before it was consumed by flames. That plane also contained lithium batteries.
Current fire protection regulations for cargo planes are inadequate, according to the board's letter.
"These fires quickly grew out of control, leaving the crew with little time to get the aircraft on the ground," NTSB Chairman Deborah Hersman said in a statement. "Detection, suppression and containment systems can give crews more time and more options; the current approach is not safe enough."
FAA rules say airplane fire warning systems must be able to detect fire in a cargo container within a minute of its ignition. But the NTSB said its tests of two types of cargo containers showed a time lapse between ignition and detection ranging from 2 1/2 minutes to more than 18 minutes.
In the tests, the fires "grew very large, capable of causing significant damage to an aircraft" before they were detected, the letter said.
Current FAA regulations require halon gas fire suppression systems in below-deck cargo holds, but not in the main cargo compartment above deck. The main strategy for fighting fires above deck is to deprive them of oxygen by taking the plane to an altitude where depressurization is achieved.
In the case of the UPS plane that crashed in Dubai, however, there was a lapse of 2 1/2 minutes between detection of the fire and depressurization, which was enough time for the fire to damage the plane and affect the pilots' ability to control the aircraft, the NTSB said.
Also, halon systems don't work on fires involving lithium metal batteries, which are found in a watches, calculators and a wide range of consumer goods.
Unlike other kinds of batteries, lithium metal batteries can spontaneously ignite if exposed to air. Also, the positive and negative poles in some lithium batteries are close together, leading more easily to short circuiting, which can cause a fire.
Rechargeable lithium-ion batteries, which power devices such as laptop computers, cellphones and MP3 players, are a fire concern, too. Fires involving lithium-ion batteries can reach 1,100 degrees, close to the melting point of aluminum, a key material in airplane construction. Lithium-metal battery fires are far hotter, capable of reaching 4,000 degrees.
FAA officials didn't immediately reply to a request for comment. A report two years ago by the agency concluded that the cost of installing fire suppression systems in main-deck cargo compartments was too expensive to justify requiring airlines to add them.
UPS said tests last month of a new type of cargo container it has developed showed the container can suppress and contain lithium-ion battery fires for as long as four hours , which is enough time in most instances for pilots to safely land the plane. The tests were conducted at the FAA's technology center in Atlantic City, N.J., with FAA and NTSB officials looking on.
The container is made from fiber-reinforced plastic akin to materials used in body armor and suits for race-car drivers. Temperatures during the test reached as high as 1,200 degrees, but a powdered flame suppressant released inside the container prevented most of its contents from being damaged, UPS said. The airline is also testing a new type of flame-suppressing cover for cargo pallets.
While the new technologies require further testing, "we believe they have the potential to revolutionize cargo safety," UPS spokesman Mike Mangeot said.