Overview: Aircraft Emergency Evacuation

Introduction:

Public demand for air travel has increased steadily over the last 2 decades and, the aviation Industry has forecast that-further substantial growth, nearly doubling of the air traffic, into the next coming decades. These forecasts have led aircraft manufacturers to design and produce airframes capable of carrying as much as 800 to 900 passengers as well as newer generation airframes made of composites. One of the important aspects from the beginning of the aviation history is that the passenger safety has always been taken with high priority within the industry. Henceforth we have seen substantial improvement in the safety standard of the aviation from design prospective to better operations and maintenance procedures. However, though the rate of accident has decreased drastically in the last three decades, the percentage of passengers surviving after the accident/incident has not decreased in comparison to the improvements achieved in other areas.

 A survey by the European Transport Safety Council assesses that 40% out of the 1500 persons who die every year in aircraft accidents, around 600 passengers die in technically “survivable” accidents. This study shows that a little more than half of them die from the direct result of the impact, and the others die because of fire, smoke, or problems that arise during the emergency evacuation process. Due to these reasons, not only the issues concerned with the prevention of the occurrence of accidents are tackled with great care but also issues contributing to improving the survival rate in the event of an accident/incident. Accidents can be classified either as fatal (non-survivable), non-fatal (survivable) or technically survivable.

There are two ways to prevent fatalities in air travel:

       by preventing accidents;

       by protecting aircraft occupants when accidents occur.

A reduction in accidents rate provides an indication of the success of accident prevention. Examining occupant survivability can indicate the positive results from occupant protection. The importance of examining occupant survivability in aviation accidents is twofold:

• it can identify actors that can be realized to increase survivability in the accidents that do occur and

•  it can help to dispel a public perception that most air carrier accidents are not survivable

In order to increase the survivability of passengers in case of accident/incident, one major area that needs immediate attention as recognized by major stakeholder is Cabin safety. It is a well-known fact that the ultimate goals of the aviation community is the accident prevention but are far from producing or operating aircraft without introducing failure. Cabin safety hence cannot be defined precisely as it covers a very diverse responsibility and interests, which mainly includes crashworthiness, operations, human factors, psychology, and bio dynamics. However, it can be classified in three majors areas, interacting with each other namely: impact protection, fire survivability and emergency evacuation.

Emergency evacuation, which is an event which seldom occurs at the scale of airlines and that is extremely rare at that of individuals. However, it is under these scenarios that the roles of the effective cabin improvement at the design stage have to be taken into account in order to prevent the accident and to develop best methods to deal with the reality of emergency evacuation. Improving survivability will therefore necessitate comprehensive review of all promising options available to regulators and Industry. More research is necessary to be conducted, in order to better understand the reality and prepare effective solutions. These options could lead to incorporating new features to aircraft at the development stage (e.g. use of other tools during the certification exercise, put in place other technologies which will increase the efficiency during evacuation). In other cases the introduction of safety measures at retrofit stage could be of high interest. However, one of the fundamental limitation for introducing further measures are either limited research on the field in order to implement the process or the lack of adequate accident information from sufficient number of accident to allow full cost benefit analyses to be performed on statistical grounds.

The very limited number of accidents available for investigation means that the basis for determining priorities still relies heavily upon expert’s judgments rather than a truly numerically specific approach. As aircraft passengers and crew benefit from the continuous application of new technologies to deliver improvements in mobility and comfort, so continuously updating safety designs can be in line with current knowledge.

Accident with Emergency Evacuation

Some examples of severe accidents in the last decade illustrate some of the safety issues pertaining to Emergency Evacuation. The 2 severe accidents described briefly below points to the fact that some new immediate measures have to be taken in various areas in order to improve the survivability of passenger during emergency evacuation.

On February 1, 1991, a USAir Boeing 737 (737) and a Sky west Metroliner collided on the runway at Los Angeles International Airport . All passengers on the Sky west plane died on impact. None of the passengers on the 737 died on impact, but 19 passengers died from smoke inhalation and 1 died from thermal injuries. Of the 19 smoke-inhalation fatalities, 10 died in a queue to use the right over wing exit. The Aircraft Accident Investigation team (AAI) pointed out that two factors caused additional exit delays by several seconds: passengers’ delay in opening the exit, and a scuffle between two passengers.

On November 19, 1996, United Express flight 5925, a Beechcraft 1900C, collided with a King Air at the airport of Quincy in Illinois, seconds after landing [I.R3]. All 12 persons aboard the United Express flight and the 2 pilots on the King Air died from the effects of smoke and fumes from the post crash fire, even though they survived the impact. A pilot employed by the airport’s fixed-base operator and a Beech 1900C-qualified United Express pilot who had been waiting for the flight to arrive were the first persons to reach the accident scene. They ran to the forward left side of the commuter’s fuselage where the captain was asking them to get the door open. Both pilots attempted to open the forward air stair door but were unsuccessful. The Aircraft Accident Investigation team determined that the instructions for operating the door were inadequate for an emergency situation. The report examined the airport rescue and fire fighting response to the accident wherein, it was found that the first units of the Quincy Fire Department arrived on scene about 13 minutes after being notified of the accident. By then, both airplanes were completely engulfed by flames. The report identified that the lack of adequate aircraft rescue and fire fighting services contributed to the severity of the accident and the loss of life.

The accidents quoted above highlight just few of the safety issues related to the evacuation of commercial airplanes. Furthermore, in addition to accident investigations, various groups such as Safety Board, Transportation Safety Board of Canada, FAA, European safety group have performed different safety studies. Also different independent researches have examined specific aspects that affect the successful evacuation of commercial airplanes. Though these studies provide insight on various specific factors such as crew’s member’s trainings, passengers behaviors, design improvement methodologies and environmental factors but still several limitations are present:

• In most of the cases, the successful evacuations were not fully analyzed and hence no comprehensive analysis has been performed on various aspects related to successful evacuation like which equipments did work well, passenger behaviors and the role of cabin crew during these evacuations.

• Most of the researches have been conducted around accidents but not is the case of incidents, which can provide more insight on actual improvement methodologies, and moreover to better understand human behavior when there is currently a dramatic lack of data.

• Many studies were led as a retrospective analysis of accident evacuations, which limited the researcher to information collected during the original investigation rather then collecting consistent information on the set of evacuation.

• Furthermore very little research has been performed on examination of most basic questions about how often commercial airplane are evacuated and how many peoples are injured during evacuation, and the reason for the injuries. In Chapter II, an analysis of data about commercial aviation accident/incident with evacuations is performed.

Moreover, based on these different accidents analysis the following safety issues pertaining to emergency evacuations can be identified:

• Certification issues related to airplane evacuation,

• the effectiveness of evacuation equipment,

• the adequacy of air carrier and Airport Rescue & Fire Fighting (ARFF) guidance and procedures related to evacuations,

• communication issues related to evacuations.

Emergency Evacuation Demonstration for Certification

The aviation authorities require certificate holders to conduct full-scale evacuation demonstrations to provide a benchmark by which the authorities can consistently evaluate evacuation capability using various seating and exit configurations. In some cases, under specified conditions, the results of a successful demonstration conducted by either the manufacturer or another airline along with other adequate tests or other acceptable means can be judged sufficient rather than conduct a new test. However, it is well understood that the demonstration is not an acceptable evacuation performance standard. That is, manufacturers must also comply with specific equipment and minimum configuration requirements in addition to successfully demonstrating complete evacuation within a standard delay fixed to 90 seconds . In addition to the 90-second time limit, the evacuation demonstration criteria includes the following:

• the demonstration must be conducted during the dark of night or with the dark of night, the simulated airplane’s emergency lighting system can provide the only illumination of exit paths and slides;

• a specified mix of passengers “in normal health” must be used--for example, at least 30 percent must be females and at least 5 percent must be over 60 years of age;

• the passengers may not have participated in a demonstration in the previous 6 months;

• and no more than 50 percent of the emergency exits may be used.

However, there are several limitations to the full-scale demonstration of which the major ones are identified below:

• Reduced acquired knowledge: The emergency evacuation scenario used in full-scale demonstrations does not represent most real accident conditions, where impact forces and fire effects frequently impair passengers. In situations involving smoke, fire and debris, the certification trial may provide little useful information with respect to the suitability of the cabin layout and of the cabin crew procedures in the event of a real emergency. The Manchester disaster of 1985, in which 53 people lost their lives, serves as a tragic example: It took more than 5 minutes for the last passenger to escape from the burning B737 aircraft while in a certification trial, the entire load of passengers and crew evacuated the aircraft in 75 seconds.

• Lack of realism: Participants- in demonstration knows they face no such danger in their efforts to quickly exit the aircraft, so panic is not present. In general the demonstrations are not performed realistically since the figurants are not subject to trauma or to the stress of a real emergency. In the certification trial, while passengers are keen to exit as quickly as possible, the behaviour exhibited is essentially co-operative, whereas in real accident situations the behaviour may become competitive.

• Furthermore, the test exposes participants to a range of injuries, from bumps and bruises to serious, permanent injuries. During seven full-scale demonstrations conducted by manufacturers between 1972 and 1980, 166 of 2,571 total participants received injuries, or 6.5 %. Of the 3,761 participants in 12 demonstrations conducted between1981 and 1991, 212 received injuries (5.6 %).

• Full-scale demonstrations of evacuation systems are both hazardous and costly. The cost of conducting full-scale evacuation demonstrations, including test set-up, payments to volunteers, analysis, and so forth, reaches upward of $2 million for wide-body transports.

• The full-scale evacuation trials are performed only once. Therefore, without the benefit of repeated trials, one cannot be confident that a single certification test result truly represents an aircraft evacuation system’s capability. Neither a margin of error or confidence level can be determined.

Aviation Authority and industry use the benchmark of 90 seconds to gauge whether different cabin seating and exit configurations provide a minimum level of aircraft evacuation safety. However, human performance, a dominant variable in successful evacuations under real or imagined emergency situations, is not easily controlled. The other factors that greatly affect the outcome of an actual emergency evacuation performance can be summarized as follows:

• absence of behavioural aspects: e.g. absence of surprise, trauma, fright and panic produces optimistic indications of an aircraft’s evacuation safety capability.

• passenger demographics, percent of seats occupied, and amount and mix of carry on luggage;

• the mix of test participants required is often not representative of the flying public on a given flight (for e.g. tests conducted using passenger loads with higher percentages of women and elderly persons, or with children and persons with disabilities, would likely generate longer average evacuation times.).

• cabin and flight crew capabilities (e.g., training, experience, and physical/mental condition);

• aircraft integrity and evacuation technologies, ambient lighting and, actual accident conditions.

Emergency Evacuation: Operational View 

The difference between a successful and an unsuccessful evacuation can be a matter of minutes or seconds during real emergency evacuation scenario. And the crew members conducting an emergency evacuation might be doing so for their firstly or likely only one time as it is rare to have emergency evacuation situation on a day to day basis, taking into account the level of reliability the aviation industry has achieved. Therefore, one important cause which plays a major role during the survivability aspect after survivable accident are either directly caused by inadequately executed evacuation procedures from the plane or “erratic” actions by some Cabin Crew Members. Therefore, the efficiency of the training of the cabin crewmember and the operations procedures implemented within the operator play an important role during the actual emergency evacuation. Furthermore, clear and precise procedures must be put in place and readily available to assist the crew, during the evacuation.

The rarity of the actual emergency evacuations can in no case allow an adequate “in line” practice. And therefore airlines have to rely on the training and practice out of line, which raises genuine challenges of realism and frequency. Furthermore, this very rarity of actual emergencies generates a feeling of low usefulness as far as such training is involved, which puts a physiological added value on the added value of training related to emergency evacuation. Therefore more emphasis on these aspects has to be put in place, to make the cabin crewmembers aware of the importance of the training. Other area, which needs immediate attention, is the management of emergency evacuations, which remains a possible direction for improvement.

A study conducted by Service de la Formation Aéronautique et du Contr?le Technique (SFACT) identified other areas with regard to cabin crew members during the actual emergency:

• The actual efficiency of the action of the Cabin Crew Members and how training related to cabin crew deals with this area.

• The adequacy of the existing regulations with regards to cabin crewmembers training.

• The clarity of the rules and regulations and the implementation standards within the airlines.

• The adequacy of the Cabin Crew Members training to deal with emergency situations.During the crew training, importance has been given by the authorities and manufacturers towards crew resource management (CRM), which is recognized as a key factor in flight crew adherence to procedures in normal and abnormal situations. The research performed by different organisations has identified that CRM issues are involved to some degree in every incident or accident and have been considered as circumstantial factors in more than 70 % of approach-and-landing incidents or accidents. Among many different factors associated with incidents and accidents the first line of error are embedded in the organization whereas the flight crew is considered to be the last link in the error-chain but it is also the last line-of-defence. And hence the influence of human factors and CRM issues in incidents or accidents is of recognized importance.However, flight attendant groups argue that, the manufacturers are using “flow control” incorrectly equivocated to “exit by-pass”, attempting to make up for configuration problems in an evacuation demonstration. The flight attendant society has been arguing that flight attendant procedures are sometime designed to compensate for cabin design deficiencies. One of the examples quoted is the following:It is clear within this example that the only way the airplane could pass its evacuation demonstration tests is to put a flight attendant in the back who will "push people" forward and thus maximize the use of the over wing exits.

• The good communication between all airplane crewmembers and between the crew and the passengers is as important as other factors described above for the successful emergency evacuations. Communication is a momentous concept for the preparation and the carrying out of emergency evacuations; the conditions and constraints of communication change according to the interlocutors that the cabin crewmembers have in front of them. One research  has identified that the way of addressing the passengers has an influence on the speed of execution of the emergency evacuations. According to the authors, addressing the passengers in a firm and authoritarian manner is a good means of limiting panic and getting an organized evacuation. However speaking in this way to the passengers is a contradiction with the service practices of the cabin flight hostesses and stewards. This problem of tasks and even of contradictory assignments displays the duality of the parts played by the cabin crewmembers. Two different methods of communication are typically used by the air carriers to inform passengers what they should do if an evacuation is conducted: the pre-flight verbal briefing from the crew and a written safety-briefing card.

• Consider an airplane that is not equipped with exits in the back but has floor level exits in the front and exits over the wings. These kinds of airplanes are operated with two flight attendants, one flight attendant being located at the forward doors. Logic would dictate that this flight attendant be located near the over-wing exits in a passenger seat converted to meet the requirements of a flight attendant seat in the exit row. A flight attendant seated in this location would be able to assist in opening the exits and could direct passengers to use the best available exits. But, this is not where the second flight attendant is in general located. The second flight attendant uses to be located all the way aft in the cabin. One reason given for this is that the flight attendants could see all the passengers and not have passengers behind them. This excuse seems to ignore the fact that the flight attendant in the front of the cabin can see all the passengers, and would provide the necessary oversight. The aft-seated flight attendant is supposed to climb over the seat backs to get to the over-wing area and at the same time give oral commands for passengers to come this way.

• On the operational side, another aspect, which has to be taken into account, is passengers flow control procedures put in place within airlines, as it is an integral part of the evacuation system of an aircraft. The procedures that have to be used either during the full-scale evacuation demonstration or as part of the analysis, are incorporated into the Flight Standards Board (FSB) report for a given aircraft, and become part of the standard for flight attendant qualification for that aircraft. This is mainly used in order to facilitate passenger egress from aircraft during an emergency evacuation for in general flight attendants use flow control when they direct passengers to come toward an exit and thereby accomplish maximum use of that exit. If an assigned exit cannot be opened, flight attendants must once again practice flow control by directing passengers to another exit. Therefore at all phase of the emergency evacuation flight attendants are required to control passenger’s flows.

• Aviation community and the researchers have questioned the fact that flight attendant training, performed in cabin mockups without passengers, could provide crew members with sufficient skills for assessing flow control problems and motivating passengers to evacuate more efficiently.

It is evident that if the passengers are attentive to pre-flight safety briefing, it will play an important role during the real evacuation scenario and hence efforts have to be made in order to improve the standard of safety briefing, like more state of the art technology, such that passengers are attracted to pay more intention to the safety briefing.

Furthermore, most of the regulations requires that safety briefing be supplemented by safety briefing cards which contain information related to safety measures for that models of aircraft and are consistent with the air carrier procedures. The safety cards must contain aircraft diagrams and methods of operations for all emergency exits and instructions for operating any other emergency equipment. However, studies have revealed that passengers do not read the safety cards and hence efforts in order to attract the attention of passenger towards safety briefing cards. 

Behavioral Aspects related to Emergency Evacuation

Success in evacuating from aircraft in an emergency can be summarized by the comparison of two quantities: the time people need to evacuate and the time available for them to do so. The human behaviour analyzed during the 90 seconds evacuation certification test can be utilized in order to empirically model and understand real behavioural aspects during actual emergency evacuation but cannot yet be reliably “simulated” due to the lack of realism in the evacuation demonstration procedures. Aviation industry has sufficient data to estimates the average reaction times and egress rates for the controlled condition (many evacuation demonstrations have been already performed by manufacturers). However, very few reliable data exist on human behaviour during accidents. The variations in human judgment and decision-making during the life threatening conditions cannot be exactly predicted since they can vary from very calm behaviour to conflicting situations between the passengers. These data cannot be obtained from current demonstration requirements, which do not address motivational effects or other behavioural factors that often exist in a real emergency.

Furthermore, data from the actual emergency evacuation investigations are unevenly collected and analyzed and these data are in general not classified nor analyzed in respect to egress behaviours during such life-threatening scenario. Different researches have suggested that there are many different ways in which individual passengers respond to an aircraft emergency situation. Responses may include fear, anxiety, disorientation, depersonalisation, panic, behavioural inaction and group following behaviours. Other characteristics which can also be observed during real emergency evacuations are: Most people generally do not panic, people demonstrate altruistic, most people will try to exit through the door they entered, people will move through smoke when necessary, people will try to remain together with a travelling companion and will try to keep their luggage.

Unfortunately, as yet, limited research effort has centred on the impact of passengers behaviour on aircraft emergencies and evacuation. The aviation industry (EASA, FAA and other independent researchers) has begun concentrating on developing computer simulators. This may provide the technology base for a dynamic aircraft evacuation simulation capability. However, additional research needs to be performed along with another difficult challenge, which is to collect additional psychological data required for validating behavioural assumptions.

Conclusion:

Big aviation manufacturer are already undertaking projects to develop flying cars notably Airbus, uber are testing the prototype which could be a reality in coming years. However, it is needed that more research in the field of human behaviour and design improvements are needed to develop safer aircrafts in case of emergency evacuations and imperative that human behaviours is thoroughly studied if "projects" on-going to develop flying cars are to be made reality but also not to forgot research on passengers Aircrafts.