Decisions, Decisions

Installing a radio and GPS system — what’s involved?


“There have been several occurrences of smoke and fires erupting from failures of lithium-ion batteries such as those used within laptop computers. A more recent incident involved a lithium battery powered portable air purifier which caught fire resulting in injuries to several passengers and diversion of the flight. The NTSB is investigating this incident. Such batteries tend to electrically short and quickly overheat when rapid discharging or unregulated charging occurs. One prominent battery manufacturer, recently highlighted in the media, produces a “regulated” battery type that has been subjected to recalls after several cases where battery failures caused fires. Other battery manufacturers, who produce “unregulated” batteries which provide higher capacity (such as those used in cameras, electronic games, medical equipment, flashlights, air purifying devices, etc.), are not necessarily aware of their vulnerabilities. Thus, the probability for such battery failures resulting from overheating caused by rapid discharging is higher with unregulated types in greater number of uses.”

The SAFO goes on to recommend that all crew members be properly trained in recognizing the type of fire and then choosing a suitable extinguishing method. In the case of lithium batteries, halon will have no effect on the shorting battery but may prevent fire spreading in the surrounding area. Only a category “D” extinguisher will have a positive impact on this type of combustion.

Battery testing research

There are published results derived from FAA sponsored testing of lithium batteries and in summary the results state:

Primary battery major findings

  • A relatively small fire source is sufficient to start a lithium battery fire.
  • The ignition of a single battery produces enough heat to ignite adjacent batteries.
  • Halon 1301 is ineffective in suppressing a lithium battery fire.
  • Batteries of the same type but from different manufacturers exhibit varying flammability characteristics.

The entire report can be accessed on the internet at http://www.fire.tc.faa.gov/pdf/systems/Lithium-ion_battery_04112006.pdf

Technical Standard Order (TSO) C-179 was issued Aug. 4, 2006 and the purpose states: This TSO affects new applications submitted after its effective date. Major design changes to rechargeable lithium cells and lithium batteries approved under this TSO will require a new authorization. See Title 14 of the Code of Federal Regulations (14 CFR) § 21.611(b). The method of testing these batteries is one of the highlighted items (See table below).

Tests for Fire Safety Requirements
Test
Procedures
Criteria to Pass
External short circuit Measure direct connection between terminals through electric wire with resistance of 2m-ohm. State of charge (SoC) of a cell: 100% No venting of gases/vapors. No smoke produced. No ignition or fire. No explosion.
Crush Test battery by dropping an iron ball (9.1 kg) from the height of 61 cm. SoC of a cell: 100% No venting of gases/vapors. No smoke produced. No ignition or fire. No explosion.
Over discharge Test battery by discharging with a current of 1A for one hour (or to the maximum discharge time for the battery operation). SoC of a cell: 100% No venting of gases/vapors. No smoke produced. No ignition or fire. No explosion.
Overheat Test battery by heating up to 115 C in the oven. SoC of a cell: 100% No venting of gases/vapors. No smoke produced. No ignition or fire. No explosion.
Fire Test equipment unit with battery in place for fire penetration by igniting a single unit. SoC of a cell: 100% Unit must contain the fragments/debris from explosion but not gases/vapors/smoke. Fire within the unit must self-extinguish. Note that a fire-extinguishing or suppression system outside the battery (such as in the equipment compartment) may be used to provide this feature if the system is designed to handle this fire threat.

Installation challenges

Based on the above criteria, our resolve was to make sure the battery was not installed in the GPS during flight operations. It would only be installed prior to aircraft power shutdown to retain the waypoints and then of course would be used on the ground vehicles as loose equipment that could easily be jettisoned in the event of fire. Recharging of the battery was accomplished by a car charger during ground operations.

Another challenge encountered was how to make the XM Satellite Radio available to the cabin occupants. In this aircraft all passengers wear headsets and all internal communications is through the aircraft intercom system. Unfortunately, the audio amplifier was a bit antiquated so a direct patch in through a switchable control was not possible. After consultation with the flight crew, it was decided a direct input was to be made to the intercom panel just like a passenger headset so any crew comments or ground to air communications would automatically take precedence and the XM volume control was to be used as the only cutoff control. It worked as advertised.

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