Has your ARFF Department readied personnel for the possibility of a cargo hold fire? Everyday when I come to work, I want my personnel to be operationally ready to respond. With the constant demand to meet minimum training requirements, the rapid advancements of technology can outrun the current training curriculums as set forth by some local jurisdictions. As society demands more personal conveniences, that demand can require new design features and/or technology. And, we all know that with new technology comes new hazards for the ARFF industry. In this case, these personal devices have created the latest aviation travel concern: the Lithium Ion battery fire.
“It’s just a little battery Chief, how bad can it possibly get?” These are some comments I hear when holding a laptop battery in my hands when teaching ARFF classes. Well in 2016, the International Civil Aviation Organization (ICAO) put restrictions on all member countries to prevent the risk of in-flight cargo hold fires. The rule won’t affect the current guidance that allows electronic devices in the passenger cabin of planes though. Even the FAA’s current fact sheet suggests that these batteries should be carried in the passenger area of the aircraft and NOT in your checked luggage. Any device containing lithium metal or lithium ion batteries—including smartphones, tablets, and laptops—should be kept in our carry-on baggage. If these devices are stowed in the checked baggage, they should be turned off, batteries removed and protected from accidental physical damage.
What’s Happening in the Aircraft?
When heat, smoke, and hot gases are caused by a small incipient-stage fire located in a confined enclosure, AKA cargo hold, we hope for early warning or detection. But because of the small size of the fire and the location of the checked bag in relation to the cargo hold itself, these two factors can change the variables for early detection. For example, there may be a slight delay in activation of the aircraft alarm system should the bag be located on the floor of the cargo hold and covered with other checked luggage. The delay depends on the source of first ignited materials and what other contents are located within the bag.
Cargo Compartment Fire Protection Systems
On most commercial narrow-body aircraft and larger, the lower cargo compartments are equipped with smoke detectors that also detect heat. There are four detectors in the forward hold and six detectors in the aft compartments where they have individual Cargo Electronic Units (CEUs). These detectors sense smoke using photoelectric cells and sense heat by temperature sensors that trigger an alarm at ±230°F.
The four and six detectors connect by two electrical wiring loops that receive power from a DC source. With the “DETECTOR SELECT” switch in the normal mode, they both have to detect heat and smoke to activate the fire warning alarm in the flight deck. When one loop fails, the CEU automatically transfers the system into a single-loop operation—built in redundancy.
When both detectors are triggered, the respective compartment “FIRE” detection button will illuminate red on the cargo smoke detection and fire suppression module. This will drive a “MASTER FIRE WARNING” light in the cockpit. Most pilots will arm the fire protection system by pushing the “FWD” or “AFT” fire warning light. The pilot needs to lift the plastic guard and push the “DISCHARGE” button to fire the onboard Halon 1301 into the compartment. The extinguishing agent should be capable of suppressing a fire for approximately 60 minutes depending on the flight conditions. During descent, the compartment pressure will increase by allowing air into the compartment; while staying at altitude there should be no change of air in or out of the fire compartment. Cargo compartments are classified as Class C fire compartments because they are supposed to confine a fire during flight. They are pressurized compartments but do not offer fresh air circulation to potentially increase the fire.
When the cargo fire protection system is activated, another system that works in conjunction is the cabin pressure controller (CPC). When it receives a signal, it will increase the pressure in the passenger cabin directly above the fire compartment. This increase in pressure is done during the descent to decrease or prevent smoke from entering the passenger cabin.
Many ARFF personnel are not familiar with the entire fire protection system within a commercial aircraft. The design features, systems and components are all essential functions of the aircraft fire protection and suppression system. Now let’s take a quick look at a case study involving a cargo hold activation and fire involving a 737.
Case Study – AVIATION Safety Report
Date: 14 JUN 2018
Type: Boeing 737
WestJet flight WS113 returned to land at Calgary International Airport, Canada, after the flight crew received an indication of a cargo hold fire.
The Boeing 737-700 was on a flight from Calgary International Airport (CYYC) to Vancouver International Airport (CYVR), Canada, with two flight crew members, three cabin crew members, and 53 passengers on board. The aircraft departed from runway 35L at CYYC at approximately 06:39. The captain was the pilot flying, and the first officer was the pilot monitoring.
While the aircraft was climbing through 9,000 feet above sea level, a lower aft cargo fire warning light illuminated at 06:41:10. The flight crew immediately followed the cargo fire procedures published in the company’s 737NG Quick Reference Handbook (QRH). The “CARGO FIRE DISCH” switch was activated, and one cargo fire extinguishing bottle was discharged.
At 06:46, the flight crew declared a MAYDAY emergency and initiated a return to CYYC. Ten minutes later, the aircraft landed on runway 35R at CYYC and exited onto Taxiway Delta. After clearing the active runway, the aircraft stopped on the taxiway and was inspected by ARFF services. No visual signs of fire were noted, and no hot spots were detected by infrared camera imaging.
In accordance with the QRH, the flight crew informed ground personnel not to open any cargo doors until all passengers and crew had exited the aircraft. The aircraft was cleared to taxi back to the gate, where the passengers and crew were deplaned. After all passengers were off the aircraft, ARFF and WestJet ground handling personnel opened the lower aft baggage compartment.
One passenger bag, found face-down near the cargo compartment door opening, showed signs of fire damage
The fire damage was isolated to the individual bag. Minor thermal damage was found to the cargo compartment’s fire-resistant liner near the bag.
The passenger whose bag caught fire flew frequently for business purposes and was aware of WestJet’s policies with respect to restricted items in checked baggage. The passenger packed his bag, a tactical-style nylon backpack, on the evening of June 13, 2018 and inadvertently packed two spare lithium-ion batteries for his e-cigarette, in the charger, in the front pocket of the bag. The pocket also contained a dry herb vaporizer, a portable speaker, and USB cables.
On the morning of June 14, 2018, the passenger arrived at the airport and checked his bag in. He took his e-cigarette and two other lithium-ion batteries into the passenger cabin, as required by WestJet’s policy on e-cigarettes.
The checked bag proceeded through the passenger baggage security screening and was loaded into the aircraft’s lower aft baggage compartment, while still containing the two spare lithium-ion batteries.
An investigation concluded that one battery in the charger experienced a thermal runaway, and the interior material of the battery was completely burnt out. The thermal runaway was likely caused by external damage. The investigation could not determine if the damage occurred before the battery arrived at the airport or during baggage handling. (Report Source: Aviationsafety.net)
The Concern of Thermal Runaway
A single personal electronic device that overheats and catches fire in checked luggage on an airliner can overpower the aircraft’s fire suppression system, potentially creating a fire that could rage uncontrolled, according to new government research.
Regulators had thought that single lithium-battery fires would be knocked down by the onboard fire extinguishing agent, currently used by all aircraft manufacturers—Halon 1301 which is required in passenger airliner cargo holds. But tests conducted by the U.S. Federal Aviation Administration found that the suppression systems can’t extinguish a battery fire that combines with another highly flammable material, such as the gases inside an aerosol can (hairspray) or cosmetics commonly carried by airline travelers. On another note, the ARFF industry should learn from the automotive industry where it has experienced secondary reignition of batteries involved in electric powered cars. Some of these reignitions happened hours or even days later after the original fire was extinguished.
The Use of Emergency Response Guidebook
Understanding the tools and equipment we have at the ready is powerful. Many people think that water is the only choice for lithium-ion battery fires. While many emergency responder guides state water is the primary agent of choice, it was interesting to see how the DOT-ERG manual breaks down the handling of these chemicals and fires involving them.
Diethyl Carbonate is one chemical solution found inside these battery packs, and if you use the US DOT Emergency Response Guidebook, you will note some interesting facts. Guide #128 says if lithium-ion batteries are involved, see Guide #147 for the off gassing of gases and liquids. The cross chemical mixing inside the battery packs is usually caused by external trauma. When these chemicals are mixed, it causes large amounts of heat. This heating process is called thermal runaway. Thermal runaway is when one small battery pack ignites, and the heat from the original fire causes the next closest battery or other chemical source to ignite as well.
The FAA hasn’t imposed any new restrictions on what passengers may pack in checked bags. Last year, in a notice to airlines, it said they should conduct a safety study to determine what more they should do to limit the risks of battery fires in cargo areas. Tests conducted by the FAA found that the halon gas suppression agent installed in cargo areas potentially wouldn’t be able to completely extinguish a lithium-battery fire, but it would prevent the blaze from spreading to adjacent material such as clothing or paper. However, aerosol cans located in the same bag exploded in tests even after being bathed in the halon gas. There is the potential for the event to exceed the capabilities of the aircraft’s suppression system when an aerosol can is exposed to the initial fire.
The reason I am writing this article is because the fire service is built on a strong tradition of putting out the fire as fast as possible! The ARFF industry requires us to maintain operational readiness and this often breeds young aircraft rescue fire fighters to practice speed drills for rapid extinguishment. But, the airline industry has put fire protection systems onboard aircraft that will enhance the likelihood of a safe return to the gate. A common practice that firefighters want to do is hold an aircraft at a remote parking area to check on the potential cargo fire. Should the cargo compartment be aggressively opened for inspection, the onboard protection system can be negated. The design features of closed compartment space, flooding of said compartment with the onboard extinguishing agent prior to arrival, and the ability to increase pressurization of the main cabin area above to reduce the amount of smoke from gaining control of the occupant space are all positive features that the ARFF Department must take into consideration and enhance. If you are required by policy to stop and hold to check before the aircraft taxis to the gate, I suggest considering a few of these things.
- The aircraft shall be stopped for a quick Risk Assessment by ARFF personnel.
- Aircraft shall be inspected by fixed-mount and/or hand held thermal imaging cameras.
- ARFF personnel should be wearing full PPE, SCBA, and be protected with fire suppression.
- If approaching the aircraft, consider controlling engine intake and/or exhaust hazards.
- If a heat signature is determined by the TIC and/or confirmed with the report from the cockpit crew of an odor or increase in temperatures, the firefighters should check the cargo compartment and cargo door for physical heat (with the back of their hand)
- Risk/Gain Assessment: Command should include the concern to passenger and crew should you deem an emergency evacuation over emergency slides, verse taxiing the aircraft to the gate for a quick deplaning process via the main door and jet bridge.
- Statistics show a controlled deplaning will yield far less personal injuries and claims should the level of threat warrant a slower more controlled deplaning vs. evacuation.
- Controlling the passengers on the sterile AOA once the emergency exit evacuation is completed creates additional concerns that must be handled by ARFF, airport management and/or airport operations teams.
Should the incident escalate to warrant an aggressive attack on the fire by ARFF personnel on the AOA, consider the following:
- Position ARFF apparatus to establish fire suppression on the cargo hold.
- Position ARFF apparatus to protect the rescue side for passenger evacuation.
- Stabilize and/or secure the aircraft. (wheel chocks).
- Control all aircraft hazards. (engine shut down procedures).
- Request an emergency evacuation. Command communicate through the pilot, the desire to evacuate to the non-hazard side of the aircraft.
- Establish fire suppression lines before opening the cargo hold.
- All personnel working in the IDLH environment must be on SCBA air before opening the cargo compartment, respiratory protection is mandatory.
- Consider the use of a penetrating nozzle to apply extinguishing agent directly into the cargo compartment.
- Control the opening of the cargo door. Slow, methodical opening reduces the rapid inrush of air. This will prevent any potential backdraft or smoke explosion.
- Apply the TIC to locate the seat of the fire and remove the source bag(s) or extinguish source bag in place.
- Overhaul the compartment. Remove all baggage and check for any fire extension.
The fire service tends to want to race to the seat, and even if we decide to go interior on this type of incident, we must maintain composure and control when opening the access door to reduce fire growth, lessen damage to the aircraft, and reduce the hazards for ARFF personnel. While the FAA does not prohibit lithium-ion batteries today, most major airlines have prohibited them in all checked baggage. This is why, at passenger check in, both the baggage kiosk and/or the gate agent will ask passengers if they are carrying any of these items in their baggage. This also includes so-called smart bags, which rely on the use of lithium-ion batteries to work. According records from the FAA, there were 46 incidents involving lithium-ion batteries on aircraft in 2017. That statistic was up from 31 incidents that were reported in 2016. Statistics don’t lie. ARFF personnel need to be operationally ready for the possibility of a cargo hold fire on their very next shift.
WILLIAM GREENWOOD is a 26-year veteran of the fire service. He is currently the Assistant Fire Chief of Training at the Manchester-Boston Regional Airport. He is a Senior Staff Instructor for the New Hampshire Fire Academy and owns Fire Emergency Training Consultation Services, FETC provides advanced firefighter and leadership training throughout the United States. He is also a national speaker for FDIC International and has been published in Fire Engineering and Fire Rescue.