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AVIATION SAFETY SERIES

Wow, We are Actually Flying Inside a Fireproof Cabin.

The requirement imposed to reduce the risk of inflight fire and discourage burning interior materials as the cause of death in a postcrash fire.

Gazing out through the window of an Airbus A350 at Penang International Airport. Image by Author.

The era when only the elite gets to fly was now a thing of the past. Nowadays a lot of people can take much affordable and reasonable priced airplane tickets around the world, with the longest flights— not in a particular order — would be from Singapore to New York, Doha to Auckland, San Francisco to Delhi, and much more, flying across the Atlantic, the Pacific, North Pole, and the vast Sahara desert. Ah, I miss flying so much.

Some people take flying as therapeutic as you are high up in the sky, looking down to the amazing view, away from problems for a moment. But, sitting in the cabin for hours and hours means anything could happen. Not to be paranoid, but one of those risks is an onboard fire.

Engineers need to think of thousands of possibilities that could trigger a fire and find a way to mitigate it but rest assured, there’s a solution for the problem. This article will explain how engineers are taking fire in the cabin into consideration when designing the material needed inside it.

In this safety series, we will take a look into why we shouldn’t probably feel fear when one board an aircraft.

Fireproof Cabin

The international aviation regulatory body has set some rules and regulations for aircraft cabin interior manufacturers to abide by, particularly regarding the material’s flammability.

In response to various incidents of a cabin fire, all the materials in the cabin of an aircraft, ranging from the carpets, seat covers, sidewalls, ceilings, and even the tray tables have to be made from fire retardant material.

These days, with the majority, if not all passengers having at least a smartphone make it even more compulsory mainly because of the lithium-ion batteries. The batteries will combust vigorously and even exploded if being compressed ( for example, stuck between seats ) or when it is overheated. That is why, if you happened to notice, some airlines insist that you notify their cabin crews if lithium-ion-powered devices are stuck between seats or in a narrow space.

The materials that make up the cabin need to be tested and proved to the authority that it has obeyed the fireproof requirement before they are approved to be inside an aircraft.

Why is it matter? We all know that the cabin will always be alert in case of a fire breakout because there are numerous fire extinguishers around on top of well-trained cabin crews in handling fire, so why does it play such a crucial matter?

It matters when you’re high up in the air and considering the time taken to make an emergency landing. Additionally, it could significantly improve the survival rate of postcrash fire when crash landing.

After all, about forty percent of passengers died because of fire even though they were alive when the crash or impact took place.

That is why the FAA introduces The Fire Resistant Material Program to zeroed out the chances of death from the burning of cabin materials within the next 10 to 15 years. Bear in mind that the program already commerces back in the late 1980s.

Fire safety requirements

The last thing you want to know when relaxing inside the cabin after enjoying your much-needed holiday is an onboard fire. One thing to realize is that there’s no fire alarm or smoke detector located throughout the interior except in each lavatory.

The cabin crews and you, yes YOU, are the eyes for any abnormality situation supervenes. That is why it is of utmost paramount to have the whole cabin made from fireproof materials that can be self-extinguished and doesn’t support combustion while emitting minimum smoke before it is too late.

Full cabin interior before it begins to be stripped out for maintenance ( but the carpets on the aisle have already been removed ). Image by Author.

The intention is to delay the flames from intensifying and minimize the burning rate so that it is under control thus avoiding it from spreading out through the cabin.

Before it worsens, the fire extinguisher can assist in putting out the fire. Another advantage of having this type of cabin material is that it can allow ample time for passengers to evacuate.

From the FAA Part 25 Appendix F;

Floor covering, textiles (including draperies and upholstery), seat cushions, padding, decorative and non-decorative coated fabrics, leather, trays and galley furnishings, electrical conduit, air ducting, joint and edge covering, liners of Class B and E cargo or baggage compartments, floor panels of Class B, C, E, or F cargo or baggage compartments, cargo covers and transparencies, molded and thermoformed parts, air ducting joints, and trim strips (decorative and chafing), that are constructed of materials not covered in paragraph (a)(1)(iv) below, must be self-extinguishing when tested vertically in accordance with the applicable portions of part I of this appendix or other approved equivalent means.

The FAA requires the manufacturer to test the materials by introducing a direct bunsen burner flame to the test kit for several seconds to a minute. It shouldn’t, of course, vigorously burn but maintain the rate of burning as well as completely extinguish by not exceeding 15 seconds after removing the source.

Quote from the FAA’s Aircraft Materials Fire Test Handbook, Chapter 1,

The average flame time for all of the specimens tested will not exceed 15 seconds for either the 12-second or the 60-second vertical test.

It is the reason why the manufacturer’s interior brochure doesn’t have a lot of variety in terms of material and design. Consequently, you see multiple airlines sometimes have the same style and even material in their fleet, maybe a little change here and there. It is expensive for the interior manufacturer to maintain the approval as a qualified firm let alone in R&D-ing, testing, and getting it approved from the authority.

With all the precautionary measures taken on selecting the right materials to incorporate inside the cabin, it is not practical if there are still some other things that can be ignited and burn. Those things are mainly debris and accumulated dust.

These unwanted materials that are left behind — usually on the other side of the sidewalls, ceilings, narrow passages, and along the cables run — can act as solid fuel that could support combustion if ignited.

That’s why when the aircraft arrived to do heavy maintenance that includes stripping out the whole cabin, one of the tasks to be accomplished is deep cleaning on the exposed areas in it together with the air conditioning ducts, conduit, structures, and so forth. Eliminating one of the elements necessary for a fire to take place — which in this case is fuel (dust) — can help in decreasing the chances of fire.

I promise you this is not a haunted house of some sort but a fully stripped-out cabin of an airplane for inspection, deep cleaning, and any other works. The only things that are visible here are the airframe structure and floorboards. Image by Author.

Passenger to Freighter

As you go down deeper and understand the requirements, you happen to notice that as this pandemic takes place, many airlines opt to convert their passenger fleet into cargo-carrying-only aircraft. You might think that “oh, just stack those boxes on top of each other or put it in the overhead baggage compartments” but unfortunately, no, it is not that simple.

Airlines are required to obtain approval from their local authority and obey the international standards and regulations before they can conduct those flights.

One of the rules that need to be obliged is the policy for someone to monitor the goods if there’s a fire or smoke as the cabin doesn’t have a fire or smoke detection system. It is contrary to the cargo compartment below.

It not only has an obligatory smoke detection system but a fire extinguisher system as well. The persons need to be aware if there is a sign of smoke or flame from the loaded cargo and extinguish it as trained and inform the flight crews immediately.

Other fun facts to know regarding the regulation required for transporting cargo inside the cabin are;

  • The amount of weight on the seats cannot exceed the weight limit itself. These could be dangerous if the flight experience severe turbulence mid-flight or hard landing when touchdown as it may damage the seat and the structure underneath it because of higher than usual G-force acting on it. Yes, the seat itself is approved to withstand certain G-force with the weight of a person on it though it may not be able to hold on to a higher density item.
  • The operator must provide the means of securing loose items such as boxes to avoid shifting from one place to another. Some airlines opt to remove the seats and installed the void area with cargo pallets, whereas others only stack the loose items and boxes on top of the seats. Both of these methods require a strong point of mountings to adequately secured the cargo with cargo nets.
After seats are removed, airlines can load up the deck with multiple pallets of cargo. Photo by SriLankan Airlines.

So, next time when you take a flight while gazing through the window and admiring the scenic view below of a snow-capped mountain, or even better the aurora, be sure to appreciate the engineers’ effort in bringing your safety to the utmost level. Their time and effort in analyzing and testing countless times to obey the strict regulation while keeping the simplicity and lightweight makes the job two times harder.

Cabin fire rarely happens, but when they do, panic and anxiety attacks overwhelm our minds to think properly hence reducing the overall action.

Thanks to the requirement in fire proof-ing the materials inside the cabin, it can slow down a fire before it becomes worse, and more importantly, it helps in preventing death caused by the smoke and flame from the burning wreckage of a postcrash fire.

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