Dangers of Lithium-Ion Batteries Aboard Aircraft

Sydney, Australia, Nov. 25 2011
A Saab 340B flown by Regional Express landed in Sydney, Australia on November 25, 2011 when a passenger’s Apple I-Phone began to emit dense smoke and to glow from intense heat. A flight attendant used a fire extinguisher to cool the battery. So why did this happen?

Thermal Runaway
According to the FAA (SAFO 09013), there are two types of batteries that are most commonly used to power PEDs. One is a lithium battery which is disposable, and the other is a lithium-ion battery which is rechargeable. Both are capable of igniting and exploding due to overheating. When a lithium battery overheats it can result in what is known as a thermal runaway. The danger of a thermal runaway is that the battery will release either molten burning lithium or a flammable electrolyte. There are also adjacent cells to the one that is experiencing the runaway, and the heat from the runaway cell can cause the other cells in the battery to heat up as well. According to Matt Thurber of AIN Magazine, “lithium-ion batteries have an energy density as high as six times that of a lead-acid battery, and lithium-ion batteries are somewhat sensitive to design and manufacturing flaws.” Matt Thurber, Aviation International News, February 2012
When a lithium battery experiences thermal runaway it releases stored energy very rapidly. The lithium-ion batteries hold more stored energy, and thus can release more intense heat during a runaway event. Because the runway is occurring within the cell, the gasses will be released through vent ports resulting in a small torch of flame which can reach temperatures of 1,100 degrees F. Matt Thurber, Aviation International News, February 2012

How do we fight the fire?
According to the FAA’s SAFO 09013, we must first extinguish the fire. The best way to do this is with a halon fire extinguisher or a water fire extinguisher. However, one problem is that once the fire is out the battery cells can reignite. Therefore, once the fire is out use water to cover the battery to prevent the cells from reheating. This is why a water extinguisher is the first choice as you can both put the fire out and cool the device. Any non-alcoholic liquid will work. Since the batteries are encased in hard plastic, it will be difficult or impossible for the liquid to penetrate the plastic shell until the heat or fire melts completely through the outer covering. This is why a fire proof container is valuable for putting the hot battery inside, and then extinguishing the fire followed by covering in liquid to prevent re-ignition. Do not use ice to cover a battery experiencing thermal runaway as the ice will actually insulate the battery, and thus keeping it from cooling.

Fire Containment Options
Several companies offer options for fire containment. One such company is Industrial Fire Products which manufactures the Fire-Fighter Hot-Stop containment bag. Since the runaway battery has the hard plastic shell and thus prevents liquid from penetrating the hot cell, this bag allows for a place to store the extremely hot battery. Assistance makes a fire sock which is cheaper than the Fire Fighter Containment bag, and can be used to store the overheating battery. Matt Thurber, Aviation International News, February 2012

Warning: Do not attempt to pick up or move a component that is experiencing thermal runaway as severe injury can occur. So, how do we us the fire containment bag? If you experience an overheating battery you might be able to get it into the bag before it begins to smoke and burn, but you must be careful. If may be better to set the devise on the ground, use the fire extinguisher to put out the fire once it begins, and then use water to cool it down. Once the battery begins to burn it will “torch” and eventually experience small explosions if you do not get it cooled down. You do not want to be holding the battery when this occurs. Another problem with using fire containment bags is that it might prevent the gasses from the battery cells from venting.

What are the Odds?
The odds are that you will never have a thermal runaway on your PED, but it is most likely to occur after or during charging. It is good policy to not charge your lithium-ion battery during flight. Pilots should also consider charging their cell phone and lap top batteries well before a flight or waiting until after the flight. If the PED is not vital to the actual flight then consider carrying the device at a low state of charge until after landing.
As aviators we must always plan for the worse such as engine failure, electrical failures, etc., and it is prudent that we approach the possibility of a thermal runaway of our lithium-ion batteries in much the same way. What will you do if you are flying single-pilot, and you experience a thermal runaway on your cell phone or lap-top? Do you have a working fire extinguisher? Do you have non-alcoholic liquid on board to keep the battery cool, and finally, do you have a place to store the hot battery until you can get the aircraft safely on the ground?

One Flight Department’s Solution
One corporate flight department based in South Carolina has adopted a policy to deal with the possibility of thermal runaways. They have purchased the Fire-Fighter Hot-Stop fire containment bags which also contain fire gloves for picking up the PED that is on fire or overheating. They have created checklist for both the flight crews as well as their passengers. The checklist reads as follows:
1. Identify the threat
2. Notify the flight crew immediately
3. Retrieve the fire containment bag from the closet at the back of the aircraft (behind the AED)
4. Don fire-fighting gloves
5. Carefully pick up the threat and place inside of the fire containment bag WARNING: Do not attempt to move the battery if it is already smoking or burning.
6. If an actual fire exists use the halon fire extinguisher to put out the fire
7. Pour non-alcoholic liquid inside the containment bag and over the battery until covered with liquid
8. Pull on the red tab marked pull
9. Press along the top of bag to insure absolute seal, thus eliminating escape of flames, smoke, etc.
The policy of this flight department is that the pilots will declare an emergency immediately after being notified of the thermal runaway, don emergency oxygen masks, and land as soon as safely possible, regardless of whether or not the fire is extinguished.

Single-Pilot Operations
An aviator who is flying alone does not have the luxury of another crewmember or passengers to assist him or her. Therefore it is imperative that each individual pilot have a plan of action should a PED experience thermal runaway during a flight. The FAA says in SAFO 09013 not to attempt to pick up the hot device as severe burns can occur. In the event of thermal runaway during single pilot operations, the pilot should declare an emergency with ATC, and land as soon as possible, to include landing on an off airport location. A runway battery that reaches 1,100 degrees F can actually burn through the aircraft floor, possibly burning through control cables, and igniting other parts of the aircraft. Pilots should not take this casually.
Another consideration is where you are flying. Are you IMC? Over mountains? Over water for an extended period of time? All of these things should be considered since it may take longer to get safely on the ground. Pilots operating in these environments will want to consider purchasing a fire containment device as they will not have the luxury of landing as quickly. This may be a situation where it is worth the risk of attempting to pick up the PED and putting it in the containment bag? The best situation is to have the ability to put out the fire with an extinguisher and then cool with non-alcoholic liquid, but in single pilot operations the containment bag may be the best option.

Wrap up
Although the likelihood of a lithium-ion battery experiencing an over-heat or fire is relatively unlikely, the possibility does exist. Pilots should develop personal procedures to deal with this likelihood such as not charging lithium-ion batteries in flight, and charging several hours before a flight if a device is needed for the flight itself. If a PED is not required for a flight consider carrying the device in battery charge depleted state. Single pilots may want to consider using a fire containment bag to store the PED during the flight. At least then it will be contained until you can land the aircraft.
Pilots should also know what to do in the event of a thermal runaway of a battery on their PED. Use a Halon or water fire extinguisher to put out the fire, use non-alcoholic liquid to keep the battery from re-igniting, consider purchasing a fire containment device, and land as soon as possible.

Resources
AIN Magazine, February 2012
FAA SAFO 09013
FAA Website