Unless you are living underground, you’ve probably heard about Samsung’s Note 7 smartphones spontaneously catching fire due to a manufacturing defect that allows for excessive pressure to be applied to the lithium-ion battery, allowing for a short to occur which results in a fire.

There has already been at least one instance of the Note 7 catching fire on a Southwest Airlines aircraft still on the ramp, which occurred after airlines began asking passengers to refrain from charging or using the devices on the aircraft. Now, the FAA has completed banned the Note 7, making it a federal crime to bring one on an airplane at all, including in checked baggage or as cargo.

You can read the FAA’s Emergency Restriction/Prohibition Order No. FAA-2016- 9288 here.

So what kind of fire protection do modern airliners have should one of these explody-phones™ still make its way onto an airplane and start a fire?

Aircraft Design and Flame-Resistance

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Fire Resistance Testing.

The Federal Aviation Regulations lay out detailed requirements for containing flammable materials, detection and suppression, as well as the flame-resistance acceptable in materials such as seat cushions, carpets, etc. There are also several Advisory Circulars and Appendices that outline specific testing requirements for materials used on aircraft.

Airliners are required to use materials that meet the FAA’s Technical Standard Orders (TSO) for specified systems. This means that should a smoldering smartphone contact a seat or carpet on an airliner, the material should show a limited amount of heat release or smoking for a specified period or intensity.

You can read more about the detailed material testing requirements in the Aircraft Materials Fire Test Handbook (if you’ve got a lot of time on your hands!).

Fire Detection

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Smoke Detector Types (Boeing.com)

So how would a smartphone fire be detected on the aircraft to alert the crew? There are many different types of fire detection systems on aircraft, and the detector type utilized is determined by the area of the aircraft where it is employed. Detection systems may utilize photoelectric sensors, thermocouples, optical sensors, pressure sensors, or other means.

A burning smartphone in the cargo area would be detected by a smoke detector that either detects light refraction from the presence of smoke (light refraction type), or detecting a change in the density of ions present in the air due to smoke (ionization type). Upon detection of the smoke, the crew would receive a warning and be prompted to select a switch to discharge the contents of the suppression system. These detectors are often set up in a dual loop configuration or single loop configuration (with fault monitoring circuit) to prevent false alarms due to faulty sensors.

In the cabin, the first detection would likely be from a passenger of crewmember, though smoke and carbon monoxide detectors are employed as well.

Fire Suppression

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Fire Suppression system (FAA-H-8083-31, p. 17-17)

Once the fire is detected, how is it extinguished? That also depends on the area where the fire is located. For the cargo area, the crew receives the fire warning and is prompted to discharge the fire suppression system. When the crew discharges the suppression system a dump system would immediately flood the cargo area with an agent such as Halon 1301, an inert gas which disrupts the combustion process. To do this, an electrical current initiates small explosive devices called squibs. A metered system would follow this by controlling the rate of discharge from fire bottles via a flow regulator, ensuring that the fire remains extinguished for a longer period of time.

Once extinguished, the pilots would divert the aircraft to the nearest practical airport in order to ensure passenger safety.

Once on the ground, the aircraft indicates to maintenance personnel that the fire suppression system has been discharged by way of a small colored indicator disks on the exterior of the fuselage. In this case, the yellow disc would be ejected.

In a cabin fire scenario, crew members would rely on hand extinguishers, such as a Halon 1211 or water-type extinguisher which are located throughout the cabin.

So what does this mean?

While the FAA’s response to ban these dangerous phones from flights is certainly called for, travelers should feel comfortable knowing that the aircraft on which they fly are very thoughtfully designed to deal with these kind of events.

So go ahead and get some relaxed shut-eye on your next trip, armed with the knowledge that your airplane will isolate such an event and keep you safe.

If you are an aircraft operator, you’ve got to juggle important Department of Transportation (DOT)-determined hydrostatic inspection intervals in addition to the usual visual inspection schedule for your aircraft. Fire bottles must be tested every 5 years, with handheld bottles every 12.

Don’t let another lengthy inspection interval slip through the cracks when that Post-It note gets buried by years of paperwork. SynapseMX can help you keep your inspections in order with just a click or a swipe on your (non-explosive) smartphone.