The U.S. Federal Aviation Administration (FAA) last week issued a safety alert for operators (SAFO) about the risk of fire or explosion when transporting lithium batteries as cargo on passenger and cargo aircraft. In issuing the SAFO, FAA urged the carriers to manage the risks associated with carrying the batteries as cargo and also issued guidance to FAA inspectors to help them determine whether the airlines have “adequately assessed the risk” of handling and carrying the batteries as cargo.
It is worth considering the seriousness of the FAA’s call for risk assessments. I think it requires more than just air carriers. Knowing every specific detail about the hazards and the risk path is difficult for anyone stakeholder in the aviation industry. In this case, it involves multiple organizations and stakeholders outside the industry, including battery manufacturers, the makers of the goods in which the batteries will be installed, distributors and shippers. Thus, more than ever, there is a need to share data and knowledge about the probability and consequences for every safety barrier and every safety fault tree branch that can lead to the unwanted event onboard (a BIG FIRE).
Here are the things so many of the experts can agree on:
- Lithium batteries pack significantly more energy per cubic space that past power sources. The energy density of a lithium ion battery is typically twice that of the standard nickel-cadmium battery.
- One of the most dangerous scenarios is when lithium batteries, packed in close proximity to one another and/or to other flammable materials, fail and go into thermal runaway. FAA testing has shown that a single lithium battery (cell), whether metal or ion, in thermal runway will spread to the neighboring batteries in the package and to adjacent packages.
- The technical standards and quality under which the batteries and battery-powered products are manufactured varies. For example, in a recent press release, PRBA – The Rechargeable Battery Association said that “compliance failures have unfairly jeopardized the integrity of legitimate and high-quality lithium battery and product manufacturers.”
- Commercial aircraft in use today have detection and suppression systems that are not capable of handling even a modest volume shipment of lithium batteries should the worst scenario happen. “In 2015, FAA Tech Center testing showed that the ignition of the unburned flammable gases associated with a lithium battery fire could lead to a catastrophic explosion. The current design of the Halon 1301 fire suppression system (concentration 5%) in a Class C cargo compartment in passenger airplanes is incapable of preventing such an explosion. In addition, tests also revealed that the ignition of a mixture of flammable gases could produce an over pressure, dislodging pressure relief panels, and thereby allowing leakage from the associated cargo compartment. This could lead to the spread of smoke and gases from the fire into occupied areas of the airplane. The number of cells necessary to produce this condition is small and can occur with just a few packages,” the SAFO said. Ten minutes could be all the time you have.
Work is underway to gather data, analyze and offer mitigations via the ICAO Dangerous Goods Panel. Some claim that the U.S. should just ignore this important work and press ahead with making their own laws to lead the world in safety and are frustrated that the U.S. has committed to not establishing something more restrictive than ICAO. But I would have to ask, where is the data that says it’s clear what rules should be made?
Let’s not forget the reality of cargo shipments – the quality concerns of worldwide manufacturers and shipping agents. There is a long chain of organizations in the distribution of these batteries. Knowing who and where the weak link is unknowingly or intentionally ducking the standards is nearly impossible. This affects the ultimate risks.
So a short list on mitigation options (and their limitations) might be:
- Ban the battery shipments on aircraft — doesn’t solve the ultimate risk
- Build a robust containment and suppression system to handle the energy — takes a long time, gets very expensive, doesn’t solve any near term risk
- Better identify where the batteries are and have a process to protect against hazardous situations — underway but not completely effective
- Improve standards and testing of original manufacture of batteries to protect against cell failures
Shouldn’t the ultimate solution should be a continued combination of these things with specific risks in mind and highest, quickest risk reductions used as a priority?
Mark Millam is vice president, technical, at Flight Safety Foundation.