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Aircraft fire and rescue

Aircraft Fire

Introduction:

Despite the low chances of catching a fire, the prompt response to an aircraft fire can save catastrophic disaster. The onset of firing or smoke in aircraft is a dangerous incident to deal with, especially when the aircraft is on the air. The earlier it can be extinguished the less would be the catastrophe and loss. The crew and pilots on the aircraft should be well trained to deal with fire on during flight; they should get basic fire-fighting training and education before their first flight. The degree of damage and loss can be easily imaginable. With the aircraft in the air, where the cabins are air-tight and the flight is over 1000 feet above the ground, an uncontrolled fire can burn the plane completely like a piece of paper including all of its crews, passengers and pilots.

Statistical data show that the fourth highest cause of aircraft disaster is on-board fire. Fire is the seventh most frequently occurring cause of aircraft accidents in 2005. (Boeing, 2005). Two B747 aircraft went down with its crew since 2005 because of uncontrollable fire. Report shows that the probability of a passenger aircraft experiencing a fire during its flight is one to ten thousand. More than one aircraft per day fail its scheduled flight due to smoke around the world. (Shaw, 1999)

To indicate the importance of timeliness in case of fire event in aircraft on-board during flight, the report of FAA can be used, where it says that,

“A two-minute late in the descent of aircraft flight can make difference a successful landing and evacuation, and a complete loss of aircraft and its occupants.”

(Federal Aviation Administration, 2004)

However, there have been a noteworthy progress in dealing and controlling on-board fire over past few years; the aircraft on-board safety has been improved. There are still places for further improvements and safety, such as in,

  • Manufacturing standards,
  • Scheduled maintenance,
  • Airworthiness,
  • Inclusion of modern and improved firefighting technology on-board,
  • Firefighting training and education for the flight crews and pilots.

Due to the inherent nature of design of aircraft, the probability of catching fire cannot be eliminated. However, the chances of fire can be significantly reduced by following safety procedures and precautionary measures.

Background:

In-flight fire has the same historical age as the history of aviation. It has been a potential risk to aircraft aviation since the very onset of aircraft flight on the air. The first accident in the history of aviation reported to occur because of uncontrolled on-board fire. It was in July 1785, when a hydrogen balloon went down to English Channel in ashes due to fire.

In spite of safety mechanisms and precautions from the manufacturers and regulatory body and crews’ part, aircraft fire has been occurring regularly since past. The Federal Aviation Administration allegedly declared in their several publications that the complete eradication and elimination of the causes of aircraft fire are not possible because of the number of potential sources of fire is extremely high on-board. (Federal Aviation Administration, 2007)

This simple statement from the Federal Aviation Administration is a simple indication to the fact that multilayer safety against fire should be implemented in order to reduce the fire risk. These agency further states,

“To address the first part of this comprehensive safety regime, we have taken several steps to reduce the chances of ignition. Since 1996, we have imposed numerous airworthiness requirements (including airworthiness directives or ‘Ads’) directed at the elimination of fuel tank ignition sources. Special Federal Aviation Regulation No. 88 of 14 Code of Federal Regulations (CFR) part 21 (SFAR 88; 66 FR 23086, 7 May 2001) requires the detection and correction of potential system failures that can cause ignition. Although these measures should prevent some of the (report’s) four forecast explosions, our review of the current transport category airplane designs of all major manufacturers has shown that unanticipated failures and maintenance errors will continue to generate unexpected ignition sources.”

(Reduction of Fuel Tank Flammability in Transport Category Airplanes Final Rule,

Reducing the Chance of Ignition, Federal Aviation Administration, 2007)

It should be noted here that there are three components required to make a fire: oxygen, ignition source and fuel.

Few aircraft fire accidents are narrated here to demonstrate the level of severity.

In the year 1946, a training aircraft of Trans World Airline was crashed near Pennsylvania due to fire. Within the minutes of take-off, the crews smelled that something is burning. They reported to the flight engineer who found that the whole cabin was burning in fire. All the efforts of the crews went in vain to extinguish the fire. Thick smoke covered all the compartments including the deck, masking the instrument panels. In an attempt to find an airport for emergency landing, the instructor opened the window, which causes him lose the control of the aircraft. The crash of aircraft killed all the crews and trainees. Only the instructor survived. In the report of the accident, cause of accident was determined to be the failure to control the fire and thick smoke. (Civil Aeronautics Board, 1946).

The replacement of traditional piston-engine aircraft with the jet aircraft greatly reduced the rate of fire incident in-flight. Jet aircraft has comparatively more reliable and robust design and state of the art firefighting technology on-board. The before checking was made more rigorous. All these steps together greatly decreased the risk of fire on-board. However, in the year 1973, two 707 Boeing experienced crash and damage due to fire and this brought further modification, regulation and design improvement in place for the upcoming aircrafts.

Recent history of fire in aircraft:

A Boeing 747, took-off from Dubai Airport and after 22 minutes of its flight on air, fire alarm started ringing. Hearing the ring, the crew found that the main cargo was on fire. With the fire in progress, the flight returned to the Dubai Airport. (United Arab Emirates Civil Aviation Authority, 2010)

In the year 2011, another Boeing 747 aircraft experienced disaster from in-flight fire. The aircraft was flying from South Korea to China. After 50 minutes later of ascent, a cargo fire was reported and the aircraft crash-landed into the sea.

A few dozens of similar fire events that took place on-board recently can be listed here. Eighteen major accidents caused from in-flight fire have been reported form year 1990 to year 2010. (Flight Safety Foundation).

Possible sources of fire in aircraft:

Several possible causes are likely to cause fire in aircraft. These are discussed below:

1.Electrical systems and wiring:

The most frequently occurring cause of fire in aircraft is faulty or inappropriately handled electrical system and wiring. The Federal Aviation Administration acknowledged the potential source of ignition in aircraft is the electrical system and wiring. A study on the causes of fire in aircraft found that, during a period of eight years starting from the year 1992 to 2000, more than 70% of the fire in aircraft was ignited by electrical spark. (Boeing, 2000). The wiring in the aircraft that carries electrical current is the root cause of electrical fire. A statistic shows that in an average sized aircraft there are about one fifty-kilometer long wire is used for electrical wiring. (Potter, 2003)

The amount of wire is growing in aircraft with the development of design and employment of new technology. This is consequently increasing the risk of electrical fire. It is obvious that the life expectancy of the wires are considerably smaller than that of the aircraft. Therefore, the aging of large amount of wire presents large amount of risk of electrical fire. (Teal, 2001).

There has been increasing complexity in the wiring due to the inclusion of several new technology into the aircraft, which is adding risk to the fire ignition. Electronically operated automated equipment, facilities for device charging etc. are associated with unique design, set of wiring and failure. Huge number of electrical equipment can cause overloading which might not be cleared by the circuit breaker or may cause spark at the joints or connecting lugs, which in turn may ignite fire on-board. One of the disadvantages of the electric fire is that it cannot be dealt with water and it grows faster. In a matter of minute, the fire can spread over a large area and can render its controlling impossible.

Equipment Failures – Cascading Effects:

Fire can be caused from equipment failure. Fire can spread very quickly and can cause several independent system failure in a minute, which in turn can cause new fire. A fire event caused a flight, Nimrod to be crashed in the sea where equipment failure occurred as a chain reaction effect. Following events took place in sequence:

  1. A DC wire caused an arc, which caused the wiring loom to fail and as a matter of seconds, several wires were melt together.
  2. The fusing of wires melt together, sent a false signal for opening the engine fours valves,
  3. The opening of this valve cased the turbine rotate at an over speed,
  4. The turbine flew out of the casing and hit fuel tank at the wing,

The resultant fire was disastrous and crashed the aircraft into the sea. Thus, a simple wiring loom finally resulted in a catastrophic disaster.

Insulation:

Aircraft contains huge quantity of insulation blanket in order to create pressurized wall and air regulation. This insulations act as the combustion materials for fire to develop. The inflammability of insulation can cause the fire grow faster than anticipation.

To add insult to injury, these insulation blankets accumulates lubricants, several chemical fluids used as corrosion inhibitors and for other purposes over the ages. As a result, the inflammability of the insulation materials increases dramatically with ages and it causes fire self-sustaining.

Standards have been declared in order to make sure that the insulation used in aircraft would be made of flammability resistance materials. However, in some cases it is found that the panel materials can provide necessary combustion materials for fire to grow. (Keegan, 2001).

However, breakdown, damage or fault in the insulation of electrical wire is also a common cause of fire in aircraft. The insulation of electrical wire should be checked and tested after a certain period to mitigate the chances of fire.

Batteries:

The transportation of lithium batteries in flight found to be one of the major causes of fire in aircraft. Heat, fire, smoke, explosion from the lithium batteries and battery powered devices cause the fire.

Lithium ion batteries can also be found in the mobile phone, camera, and laptop etc. devices carried by the passengers on-board. Lithium batteries can supply spark or arcing to ignite fire. Thus, lithium ion batteries become a potential source of fire in aircraft.

Fire Fighting: Detection, Prevention and Rescue:

All the modern aircraft are equipped with on-board firefighting tools and redundant source of power supply unit in order to supply the aircraft with power in case of emergency. Detection and prevention can mitigate the damage and degree of catastrophe. In order to detect fire on-board, sensitive detection tools like smoke detectors are installed in all the compartment of the aircraft starting from the deck to lavatories with smart and automatic fire alarm and fire extinguisher equipment. However, it is not possible to cover every corner of the aircraft with fire detection and extinguisher equipment. There are places like middle of the cabin, where the observation and fire-fighting skill of the crews are the only hope for rescue and prevention.

It is obvious from the above discussion is that due to the inherent nature and design of the aircraft, it is virtually impossible to eliminate all the sources of fire completely. Therefore, prevention and mitigation are the only lines of defense here. The prevention and successful extinguishing of fire largely depends on the early detection and prompt response. Smell of burning materials and smoke is the main source of identification of fire. However, the smell cannot direct properly to the place of fire in case of aircraft. It is because that, due to the air circulation system in the cabin, the smell is hard to detect its source from. In an average aircraft the rate of air exchange is one per two or three minutes. It means that the air in the cabin is completely replaced with fresh air in every two or three minutes, which makes the fire detection task with the help of burning smell. Therefore, only source of detection remains to be the smoke. However, the situation become even worse when all the air conditioning packs work together since it causes the smoke to be diluted and dispersed throughout the cabin. The result is the breathing problem of passengers and crews and fume which blurs the sight. Potential solution to this problem is to train the crews for changing air flow pattern in the cabin such that the smell of burning can lead to the location of fire. Besides, they should also know how shut the air conditioning packs off in order to detect from where the smoke is coming from. The shutting down of air conditioning packs may necessitates some means to maintain positive pressure in the cockpit.

Another possible solution of this problem is to increase the number of detectors in the aircraft. Reports say that more than 70% of the fire origin in the aircraft is electrical spark and arc. Therefore, the most likely places to set the detectors are near electrical installations, power houses, and especially the location which remain out of sight during flight. One such area is the cargo area.

However, a potential flight problem arises as the number of detectors increase. It is the false alarm. A study found that almost 12% of the flight diverted due to false fire alarm and more than half of the fire alarms come from cargo areas are false.  (International Air Transport Association, 2005). These false fire alarms cause many of the true alarms to be ignored and unattended. Therefore, a trade-off should be made between the number and placement of fire detectors and the speed of the fire warnings. Detectors should be checked for false alarm regularly. Old detectors tend to become insensitive or oversensitive. These should be replaced by newer ones. Another possible solution to the false alarm is to set up detectors with multiple sensors, which buzz only when all the sensors sense smoke or fire. Modern aircraft are equipped with special fire detectors namely dual loop detectors which ring the fire alarm only when both the loop detect fire. These type of special detectors should be placed in location which remains unmonitored or which are not easy to go for a check.

Different types of sensors can also be used to mitigate the false alarm, like thermal and smoke detectors. It only goes on when both the detectors detect fire simultaneously. It should be worthwhile to mention that, there are several sources which imitates the symptoms of fire to the detector like overheated electrical equipment, odors from bleed air etc.

The rescue operation is the key to reduce loss of damage and life. A prompt evacuation and supply of oxygen in time at the event of fire can save lives. The cabin crew should be well trained with the fire-fighting training. They should take prompt action in order to extinguish fire. There are fire extinguisher, automatic water sprayer on-board. Crews should know how to use them in case of fire. They also should have the training to mitigate panic from the passengers in case of fire. If panic spread among the passengers it might make the rescue and recover activities more difficult. In most of cases, an early detection of fire and early initiative can remove risk of hazard. Crew should also trained with first-aid treatment.

Future technologies:

Numerous research is ongoing to reduce the risk and hazard of fire from the aircraft. Incorporation of state of the art fire detection system and, automatic and intelligent fire-extinguishing mechanism on-board is a matter of time. Automatic air circulation pattern changers are also going to be included in the aircraft. Intensive research is going in order to reduce the number of wires in the aircraft, which are main culprit in electrical fire. Design improvements and perfect placement of electrical devices can reduce the volume of wires used in the aircraft. Engineers are finding wires with light weight and, overvoltage and current carrying capacity for wiring in the aircraft. Redundant system of power sources, which switches automatically in case of failure of other are also being installed in the future aircraft. Insulation, as discussed, one of the potential fuel for sustained fire, are undergoing research to be replaced with materials that are not inflammable. (Blake, 2003)

Few aircraft are being equipped with fire-fighting bots, which can extinguish fire in a systematic way and can travel locations, where man cannot go in-flight.

Conclusion:

Fire on-board is one of the most damaging hazard in the history of aircraft accidents. Every year large number of accidents happen due to unduly attended fire on-board. A well trained team of crews and modern fire-fighting equipment on-board can help mitigate the hazard and facilitate the rescue operation in case of fire. Fire should not be treated with fear rather with respect.

 

References

Boeing,. (2005). Statistical Summary of Commercial Jet Airplane Accidents:  Worldwide Operations 1959-2004. Seattle.

C, K. (2001). NTSB: Investigations involving in-flight fire. Presentation, Atlantic City.

Civil Aeronautics Board,. (1946). Accident investigation report: Transcontinental and Western Air. Washington DC: Civil Aeronautics Board.

Federal Aviation Administration,. (2004). Advisory Circular (pp. 120-80). Washington: Federal Aviation Administration.

Federal Aviation Administration,. (2007). Enhanced Airworthiness  Program forAirplane Systems/Fuel Tank Safety (EAPAS/FTS). Washington: Federal Aviation Administration.

International Air Trasport Association,. (2014). On-board fire analysis: From January 2002 to December 2004. Quebec: International Air Trasport Association.

Potter, T., Lavado, M., & Pellon, C. (2003). Methods of characterizing arc fault signatures in aerospace  applications. Presentation, Attleboro.

Shaw, J. (2000). A review of smoke and potential in-flight fire events in 1999. Orion, 2009, 07--12.

Teal, C. (2001). Health management for avionics performance. Presentation, Florida.

Research Paper:

Number of pages

10

Urgency

48 hours

Academic level

College 3d year

Subject area

Managment

Style

APA

Number of sources

9

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