Fires started by faulty lithium batteries are a major concern for air freight haulers such as Federal Express. The expediter has teamed up with Ventura Aerospace to develop an electronics system that smothers fires with foam that lasts up to four hours.
The two companies collaborated on a system that monitors individual cargo containers. Its dedicated modules watch individual containers for potential fires and then fill them with retardants.
“The system monitors temperature. When it gets beyond a certain level, it will punch a 2.5-in hole in the container and inject foam,” said Bruce Popp, Strategic Products Manager, Federal Express.
The cargo foam was developed to handle class D lithium battery fires. It’s one of a few materials that work well with both lithium and sodium fires.
Sodium practically explodes when it is hit with CO2, while lithium will burn even in nitrogen, Popp explained. Even before Halon was banned, it provided fairly short-term help because it quickly sank to the bottom of the container.
“The foam has a lot of persistence. It fills the container and stays there,” said Jeremy Snow, President of Ventura Aerospace.
FedEx is currently finishing its first commercial application, with plans to expand usage rapidly. The rollout will begin on overseas flights since landing options are limited if a fire threatens the aircraft’s safety.
“We’ve approved this to go on all our international flights,” said Popp. “The foam will keep a fire down for four hours, which meets our requirements for international flights.”
Once high temperatures are detected, container contents are quickly covered. “It takes 10 minutes to fill a container with foam,” said Popp.
Currently, FedEx uses smoke detectors in the storage hold. However, they do not provide any input on where the fire is.
The new system consists of a fire control hub and individual fire control units for each of the containers. For example, there are 14 shipping containers on a Boeing MD-11. Each one has a dedicated fire control board, making a total of 15 boards including the fire control hub.
The control units are connected to the fire control board with a 16-port Ethernet switch that uses a variant of the popular TCP/IP internet protocols. Power is sent over Ethernet, so only one cable is needed.
Such modularity makes it simple to install systems in a variety of aircraft. The modules are built around CompactRIO boards from National Instruments. NI’s LabVIEW was used to program the system. That software will run on all production units.