quinta-feira, 4 de agosto de 2016

In-Flight Fire - Batteries Travelling in Passenger Baggage

Halon replacement deadlines

In 2010, the European Commission adopted cutoff and end dates for essential-use exemptions for halon on airplanes operating in the European Union. The International Civil Aviation Organization adopted halon replacement deadlines in 2011, and Underwriters Laboratories will withdraw its standard for halon in handheld fire extinguishers in 2014.

Aggressively Pursue 
Aggressively pursuing a fire means taking immediate action to determine the source of hot spots, smoke, and/or flames. The crew should quickly evaluate the situation, gain access to the fire, and attack the fire using all available resources, which may include deadheading crewmembers or able-bodied persons (ABP).

Cheek Area
This term describes the area just below the floor, outboard of the cargo compartment areas. In narrow and widebody aircraft, this area houses wire bundles, hydraulic lines, and other electrical components. (See Appendix 2, Typical Widebody Cross-Section.) c. Circuit Breaker. Circuit breakers are designed to open an electrical circuit automatically at a predetermined overload of current. d. 

Halon is a liquefied gas that extinguishes fires by chemically interrupting a fire’s combustion chain reaction, rather than physically smothering it. This characteristic is one of the main reasons that halon extinguishers are effective when the exact source of the fire cannot be positively determined. Halon fire extinguishing agents that have been approved for use in aircraft include Halon 1211, Halon 1301, and a combination of the two (Halon 1211/1301). Both are typified as “clean agents,” leaving no agent residue after discharge. Approved halon-type extinguishers are three times as effective as carbon dioxide (CO2) extinguishers with the same weight of extinguishing agent.

Insulation blanket burn-through protection
Fire-protective insulation blankets are designed to resist burn-through from a fuel fire next to the bottom half of the fuselage

Photoelectric-area type. These detectors are designed to detect the presence of smoke particles in the air by reflection of scattered light. They also rely on particles in the air being convectively carried into a sensing chamber where light from a pilot lamp is transmitted through a sensing chamber. If smoke is present, it will reflect light onto a photocell and trigger an alarm. Newer production airplanes use photoelectric detectors based on an advanced smoke sensor utilizing two discrete wavelengths to determine the presence of smoke and to distinguish between smoke and nonsmoke aerosols. These are also mounted in the ceiling or upper sidewalls of the protected space.

Photoelectric-ducted type. These detectors are similar to photoelectric-area type detectors, but they are typically mounted behind the walls of the protected space. They differ from the area detectors in that fans draw air samples from the protected space into a series of air sampling ports in the monument walls and ceiling, and then through an aluminum tube manifold to the detectors. Current production airplanes use the more advanced area detectors mentioned above, rather than ducted photoelectric detectors.
Each smoke detection system has a built-in electronic test capability switch. This allows for the system’s electrical and detector sensor integrity to be checked at any time.
Detection of smoke is affected by compartment volume and contour, air distribution, and the amount and buoyancy of the combustion particles. Boeing conducts extensive laboratory and flight testing to determine the best location for the detector sensors to enable them to most effectively detect smoke under all conditions.

One of the largest trends in the growth of in-flight fire is due to the transportation of lithium batteries. From March 1991 to October 2012, the FAA office of Security and Hazardous Materials Safety recorded 132 cases of aviation incidents involving smoke, fire, extreme heat or explosion involving batteries and battery powered devices (Federal Aviation Administration, 2012). Lithium batteries were the majority of battery types in the incidents. (Levin, 2011)

Lithium ion batteries (Li-ion) are used to power portable electronic devices such as cellular phones, portable tablets, EFBs and digital cameras; Li-ion batteries are rechargeable. Non-rechargeable lithium batteries (Li-metal) are similar to Li-ion, but use a different electrode material – metallic lithium.

All lithium batteries present a potential fire hazard. These batteries are carried on aeroplanes as cargo, within passenger baggage, and by passengers directly. Like some other batteries lithium batteries are capable of delivering sufficient energy to start an in-flight fire (Kolly). Lithium batteries present a greater risk of an in-flight fire than some other battery types because they are also unable to contain their own energy in the event of a catastrophic failure (Kolly).

Only a small fire source is needed to start a lithium battery fire. The material around lithium battery powered devices (often plastic) melts easily and ignites adjacent cells or batteries, contributing to higher fire intensity (Webster, 2004). When shipped as cargo, batteries are packed on pallets.
Aviation accidents and incidents, believed to be caused by Li-ion battery initiated fire, have occurred when battery shipments were placed next to other cargo on the aeroplane. On 3 September 2010, UPS Flight 006, a cargo flight from Dubai, United Arab Emirates, to Cologne, Germany, crashed off airport near Dubai resulting in the deaths of the two crewmembers. The Boeing 747-400F departed Dubai but returned due to smoke in the cockpit and the indication of major fire on the main deck.

The investigation revealed that a large quantity of lithium batteries were on the flight.
Following the accident the FAA issued a SAFO stating that Halon was inefficient in fighting fires involving a large quantity of lithium batteries. A restriction was also put in place to restrict the carriage of lithium batteries carried in bulk as cargo on passenger flights. (Federal Aviation Administration, 2010)

Additionally, IATA modified the Dangerous Goods Regulations to improve risk reduction for the shipment of lithium batteries. (International Air Transport Association IATA, 2012).

Batteries travelling in passenger baggage can also start an in-flight fire. The FAA recommends that lithium batteries should not be packed in checked luggage, but kept in hand luggage and stowed in overhead aeroplane’s compartments during flight. On 17 April 2012, an in-flight battery fire incident occurred on Pinnacle Flight 4290 from Toronto, Canada to Minneapolis/Saint Paul, Minnesota (LitBat Fire TransCanada October 2011). While at 28,000ft, a passenger’s personal electronic device (an air purifier) caught fire.

During the in-flight service, the flight attendant noted that the device was on fire on the floor; its battery was burning several feet from the device. Using water from the  service cart, the flight attendant put out the fire using wet paper towels. She then submerged the battery in a cup of water because the battery was still smouldering.
On the flight deck, the Captain sensed very strong burning electrical odour coming from the cabin. An emergency was declared and the flight diverted and landed safety at Traverse City, Michigan (Avherald). Li-Ion batteries such as the one described in the incident above do not need to be operating in an active circuit to catch fire and do not require a short to overheat. Incidents like this one are becoming more common as the number of personal electronic devices increase as shown in the FAA office of Security and Hazardous Materials Safety data. It is not uncommon for a passenger to carry several devices with lithium batteries.

Devices include, but are not limited to, laptop computers, tablet computers, mobile phones, electronic watches, flashlights, EFBs, and e-readers.
On a typical flight, a single aisle jet carrying 100 passengers could have over 500 lithium batteries on board. These devices are not tested or certified nor are they necessarily maintained to manufacture’s recommendations. Replacement batteries from questionable sources (‘grey’ market) can be contained within devices.

‘Grey’ market batteries may not be manufactured in accordance with international standards. It is possible that they have a greater probability than original equipment to overheat and cause a fire. Aircraft crew have no means to determine the presence of ‘grey’ market batteries or the physical condition of batteries on board.
The FAA Fire Safety Branch through cooperation with the International Aircraft Systems Fire Protection Working Group conducted several tests using standard Lithium-Ion batteries.
The tests used a standard air exchange rate of one cabin air exchange every 60 seconds using one air conditioning pack (system) with the gasper fans operating; the flight deck door was closed for all tests. The results for the first test showed that there was no visible smoke or audible warning prior to the battery event. After the battery went into thermal runaway the smoke percentage was greater than 10% light obscuration per foot for a period of approximately 90 seconds (Summer, 2012). The second test performed outlined similar results. In conclusion, the outcome of the tests prove that even in a high ventilation rate a typical COTS Li-Ion battery could pose a “significant hazard within the flight deck environment and could potentially present a catastrophic risk” (Summer, 2012).

 Lavatory fire protection

Lavatories include systems to both detect and extinguish fires

One type of electronic device that is rapidly gaining use in all forms of aviation is the EFB. These devices are used by pilots to replace paper materials found inside the flight deck. EFBs can be divided into groups by Classes:

·         Class I: Portable electronic devices (PEDs), Commercial off the shelfequipment (COTS), used as loose equipment and stowed during portions of flight.
·         Class II: PED can be COTS equipment, mounted and connected via aeroplane power supply for use in flight and for charging.
·         Class III: Not PEDs or COTS. Class 3 is considered installed aeroplane equipment. These are built and tested specifically for aeroplane EFB use (Summer, 2012) Class I and II are not subject to FAA airworthiness standards. However, Class II mounting and charging connections are. Class III is subject to airworthiness standards for all aspects of their operation. Because Class I and II are not subject to FAA airworthiness standards, they bring potential hazards when used as EFBs. All classes of EFBs utilize lithium-ion batteries as their primary power source.

As the number of Class I and II devices increase in their use inside the flight deck, the number of potential hazards also increases.

The FAA Technical Center conducted research on all classes of EFBs. They cited the primary concern as thermal runway of lithium batteries.

“The primary concern is the resulting fire/smoke hazards should one of the lithium-ion (Li-ion) batteries installed in these units fail and experience thermal runaway, a failure causing rapid increases in temperature, significant smoke production and at times, explosion and/or rocketing of the battery cell.”

Furthermore, the FAA tests found that:

The testing showed that even with a very high ventilation rate of one air exchange per minute within the cockpit, a typical COTS Li-ion battery could pose a significant smoke hazard within the flight deck environment. . The initial battery event occurred, at times, without warning (i.e. no visible smoke or audible event prior to failure). The battery cells failed in a very vigorous manner, at one point with enough pressure to forcefully push open the unlatched cockpit door. The most striking safety hazard however, was the volume and density of smoke that emanated from the failed battery cells.
During one test in which only four of the nine battery cells went into thermal runaway, the installed smoke meter recorded greater than 10% light obscuration/ft for a period of greater than 5 minutes and a peak value of greater than 50% light obscuration/ft, resulting in severe lack of visibility within the flight deck. (Federal Aviation Administration, 2012)

As portable electronic devices become more powerful, so will their batteries. The increasing energy densities of the batteries will also increase the likelihood of producing an uncontrollable in-flight fire. The proliferation of portable electronic devices will also increase the risk of battery failure incidents (Keegan, 2001).

Technologies are available to lessen the spread of lithium battery-fuelled fires. The FAA has requested that ISO develop a standard for Fire Containment Covers. They have also conducted testing of intumescent paint, which acts as a thermal barrier, when used in the packaging of lithium batteries. (Pennetta, 2012).

Ceiling-mounted smoke detectors
Typical faceplate of a ceiling-mounted ionization smoke detector (left) and a photoelectric smoke detector (right)

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