Flight Safety
Air
transport is expected to grow substantially in the coming decades. It enjoys a
good safety record, as can be derived from relative safety standards. But
public perception of safety is focused on the absolute safety record rather than
the relative one. This has stimulated to set new safety targets in air
transport. In order to achieve these, a good knowledge of root causes of
aviation accidents and the implications of new technologies and procedures must
be understood. The human factor plays an important role in aviation safety. The
environment in which aircraft operate is also an important contributing factor.
New safety standards are needed for the aircraft, engines, maintenance, ATC
etc., to prevent accidents from happening and to reduce the impact of accidents
by making them survivable.
In order to satisfy the needs of the modern citizen, air transport capacity
will have to grow. A growth rate of - an average - 5% per year, during the next
20 years is expected to be needed to satisfy the demand for passenger air
travel. This will result in at least twice as many aircraft and aircraft
movements in the global air transport system. It is expected that new, bigger, aeroplanes will be used to accommodate the growth in air
transport.
At the same time, society demands that the air transport system will generate
less noise, especially in the vicinity of airports, and pollution- both at
airports and in the global atmosphere. And the public acceptance of unsafety in air transport is decreasing: in fact a zero
fatal accident rate is requested from our mature industry, even though the air
transport passenger volume will nearly triple by 2020.
As traffic volumes are increasing, the absolute number of accidents increases
at the same rate. This not only results in a public image of unsafety, which could influence the demand for air
transport. It also results in a substantial increase in liability claims, which
ultimately will influence the cost of air travel. The main areas of future
research areas are the following:
System monitoring
Statistical data analysis provides a means to understand the causes of
accidents. Although, in most cases, accidents are the combined result of
several causes andconditions, analysis of causal
relationships has shown that there are a limited number of crucial factors that
contribute to accidents.
The human factor
The human factor plays an important role is aviation accidents and incidents.
Introducing new equipment without fully taking into account the Human Machine Interface
(HMI) will lead to increased error levels, increased training requirements and
resistance to use new technology. Furthermore, new products will not be used up
to their full potential.
One element in the HMI issue is operator workload, which is not only determined
by the taskload resulting from system factors:
workload is also determined by the abilities, experience and working
environment of the human operator. These elements are vital issues in a human-centred approach towards system design.
The operational environment
Aircraft operate in a harsh environment. Weather conditions often contribute to
aviation unsafety. Systems such as advanced onboard
warning systems, datalink communication, satellite navigation and
surveillance help the crew to maintain situational awareness, and prevent
un-controlled flight.
European research on external hazards - the understanding of the phenomena, the
prediction, detection, warning and avoidance - is supported by a network of
specialists: EXTHAZ.
Wake vortices are not only an air transport safety issue; the wake vortex of
aircraft also has a decisive impact on the capacity of the air transport
system. In Europe, substantial efforts are being made to better understand,
avoid, detect and reduce wake vortex phenomena.
Advanced aircraft systems and structures can help to prevent accidents and to
make accidents survivable.
Progress on European developments in pro-active warning systems and advanced
integrated avionics suites that provide increased situational awareness, i.e.
through sensor fusion, were highlighted.
Increasing engine and engine component safety is also important.
It
is expected that the current and future European research in safety related
issues, including supporting research to improve certification processes, will
enable the long-term safety goals to be met. The contributions in these
proceedings will certainly be a proof of the excellent expertise and
capabilities in the domain.
A series of well publicised aviation accidents and dramatic changes in airline industry structure during the sept 11 and some earlier crashes have fueled growing public concern about safety. The horrific consequences of major airline accidents have brought to public attention in a dramatic fashion by accidents such as ………………. While crashes of small commuter aircraft and private planes receive less attention than larger airlines, even these airlines have received relatively greater publicity than in the past because of deaths of well known sports entertainment and political figures.
HAS DEREGULATION REDUCED THE SAFETY OF AIRLINE INDUSTRY?
HAS AIRLINE SUFFERED DUE TO THE INCREASING PRESSURES OF COMPETITION RESULTING I N EQUIPMENT FAILURES?
HAS GREATER DEMAND ON ATC REDUCED THE SYSTEM SAFETY?
DOES THE GROWING USE OF COMMUTTER AIRLINE POSE A SAFETY THREAT TO TRAVELLING PUBLIC?
Naval Aerospace Medical Institute
Peer Review Status: Internally Peer Reviewed
This chapter presents survivability principles and describes procedures for calculating crash forces. While the calculations more frequently fit aircraft without ejection seats, they are not restricted to such aircraft.
Every FSR should address crash survivability directly. The investigation of injuries and deaths from crashes which can be shown to be survivable will identify problems such as weak seat-to-floor tiedowns, noncrashworthy fuel systems, helmets that offer marginal head injury protection or that may themselves cause lethal injuries, and rudder pedals that fracture tibia and hinder escape. For too long it has been assumed that injuries or fatalities naturally occur in accident sequences. It is neither luck nor fate when an aviator survives
The Components of Survivability
Survivability requires two things - the presence of tolerable deceleration
forces and the maintenance of a volume of space consistent with life. This
section highlights the mathematics of crash force calculations and considers
the elemental components of survivability.
Calculating the crash forces in an accident is an imperfect art. Using known speeds, stopping distances, and gravity constants, it is relatively simple to calculate the deceleration forces imposed on an airframe. These numbers must then be viewed from the perspective of the aircrewman for whom other factors serve to increase or decrease the acceleration (G) forces he must tolerate to survive. A reference tool is the acronym "CREEP. " The CREEP factors are:
C = Container
R = Restraints
E = Environment
E = Energy absorption
P = Postcrash factors.
The Container.
An airframe which disintegrates, allows penetration by objects, or which fails
to otherwise preserve an appropriate volume of living space can produce or
contribute to injuries. The use in larger airframes of brittle alloys that
trade off pressurization integrity for impact resistance has been a source of
container problems. Another obvious examble is the
invasion of the aircrew living space by helicopter transmissions after the main
rotor blades strike the ground. The limited space between crew seats and
controls, dashboards, or outside objects with which the crew can collide is
also a container problem. The thoughtful investigator will evaluate the living
space remaining after impact forces have been dissipated, remembering that some
ductile metals can rebound after they have compromised volume, leaving few
traces of their brief invasion into the aircrew compartment.
The Restraint System.
To secure an aircrewman with a system of straps
designed to withstand a 10,000 pound load is futile unless the system is
maintained and used properly. Worn or damaged straps may fail at reduced
loading. Unused restraints speak for themselves. Loosely secured restraints
present a special problem because of dynamic overshoot. This occurs when the
aircraft has begun deceleration over time before the crewman actually impinges
on his straps, which may either fail or rebound. Crash force calculations under
the latter circumstances will be in error by at least a factor of two.
Ten thousand pound test straps affixed to a seat which in turn will separate from the floor with a 4 G deceleration in the x-axis or 1. 5 G deceleration in the y- and z-axes are a complete mismatch. Loose restraints invite submarining in which the aircrewman can exit the seat in whole or in part without unfastening the restraint buckle. Buckles that open under survivable deceleration forces or that cannot be opened with one hand must be identified. Those buckles that cannot be opened if suspended, inverted or that are so complex as to defy quick opening by nonaircrewmen must also be eliminated from the inventory. Inertial reels left unlocked may lock automatically as advertised, but only if the deceleration is in the x-axis, and then only after some amount of travel that equates with dynamic overshoot.
The aft-facing seat, which ostensibly requires a simpler restraint system, must withstand higher G-loading than its forward-facing counterpart because its center of gravity is higher. A seat designed as forward-facing which is installed facing aft will predictably fail under minor G-loads. The side-facing seat exposes its occupant to the least survivable G-loads, restraining systems not withstanding.
The Environment.
There are many features of the cockpit environment which affect the ability of
an aviator to withstand crash forces. Pyrolyzation
products from fires involving electrical insulation and polyurethane
sound-attenuating or decorative panels can produce in-flight incapacitation
which reduces survival chances. The same is true for the volatile hydrocarbons
present in a cockpit fire at low ambient pressures, with or without the
presence of open flame. The toxicological properties of substances in a sea
level environment may be substantially altered when the event occurs at
altitude.
Another environmental factor which influences crash survivability is the speed with which emergency egress can be accomplished. If an aircrewman or a nonaircrewman has been trained in specific emergency exit procedures, and he is then confronted with unanticipated impediments to a fast exit, survival chances decrease. The capability of a crewman to egress rapidly must be considered in assessing survivability.
Energy Absorption.
The more energy absorption that occurs in the airframe before the aircrewman's body becomes the absorber, the safer the
crewman. Honeycomb construction, stroking seats, and expendable space and metal
are a few of the techniques available to the engineer for increasing
survivability. Landing gears that can absorb a sink rate of 35 feet per second
are expensive, but they are a reality and will increase the chances for
survival.
It is only necessary that energy absorption devices be built to absorb a portion of impact in a 40 G crash; man can normally handle the remaining 20.
Postcrash Factors.
Statistically, the single most important postcrash
factor affecting survivability is fire. It is a safe assumption that if fire is
not yet present at an accident scene, it will be shortly. The atomization of
fuels that occurs simultaneously with destructive impact renders all aviation
fuels of equally dangerous potential, regardless of flash points, vapor
pressures, or other laboratory-measured properties. The U. S. Army has led the
way in the evolution of crashworthy fuel systems designed to prevent spillage
or atomization. These breakaway, fail-safe valves, pipe connections, and tanks,
which all prevent escape of fuel, have dramatically changed the previously grim
statistics of helicopter postcrash fires. The
continued acceptance of belly fuel tanks located beneath or directly adjacent
to crew and passenger compartments, where impact and abrasive forces must
compromise these spaces, no longer merits tolerance.
Along with the direct thermal effects of fire, the attendant hazards from products of combustion must be recognized. Toxic gases, including carbon monoxide, cyanide, phosgene, and acrolein may all contribute to the injury or be fatal themselves. Carbon dioxide levels will also rise, promoting reflex hyperpnea. Particulate matter and smoke can not only interfere with breathing, but also decreases visibility, hindering egress and rescue efforts.
Use of thermal protective garments and readiness of firefighting equipment both in the aircraft and at the duty runway edge are standard procedures in the military. These measures are substantially less effective, however, than the designing of an airframe to absorb impact without fuel spillage and subsequent ignition. A survivable crash, with mild to moderate G-forces that produce associated limb fractures in passengers and crew, rapidly becomes a tragedy when postcrash fire occurs and timely egress becomes impossible.
There are myriad postcrash factors influencing survivability. Fire is the most important. Others, such as poor communications, inadequate rescue capabilities, water survival requirements, and training problems should be evident to the investigator as problems that may require corrective action on a local level. The problem of postcrash fire, however, remains nearly universal.
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Top 10 Airline Safety Tips |
Due to the events of 11
September 2001, there have been a variety of changes in the air travel in
the U.S. and elsewhere in the world. In addition to advice on this page, AirSafe.com
also provides other information related to the current air travel situation:
Airport Security Issues
Things You Should Not Bring On
Board
Ten Tips for Travel
Under Increased Hijack Threats
Other
items of interest:
Top 10 Safety Tips For Airline Passengers
Fact Sheet:
Improvements to Cabin Safety
Over the years, the FAA has conducted extensive research and significantly upgraded cabin safety requirements to increase the likelihood of passenger survivability in aviation accidents. Many aviation accidents are survivable and improvements to cabin safety and the prevention and control of in-flight fires have contributed to passenger survivability. Examples of advancements in cabin safety:
INDIAN FLIGHT SAFETY
Around 70 per cent of accidents in air are due to the human factor and almost all of these are avoidable, industry experts said at a seminar here on Friday. Most accidents can be avoided if utmost caution is taken and standards of safety norms enhanced, they added. Around 10 per cent accidents are due to problems in the carrier.
Though accidents have reduced over the years to about 1.5 per million departures and has remained at this level with no signs of declining, Flight Safety Foundation president and chief executive officer Stuart Matthews said. Statistics over the last decade have shown that 50 per cent of accidents have occurred during take-off and landing, he said.
Matthews also voiced concern on the accident rate in the Third World. A large increase in air traffic is expected from these nations which could translate into more accidents, Matthews said.
The aviation industry globally has to address the issue in a pro-active manner, he said. Use of the digital flight data recorder (DFDR) can be productive in identifying the fault and taking corrective measures.
Continuous analyses of the digital flight data recorder combined with confidential reporting and non-punitive systems especially by pilots can help prevent accidents, he added. The Airlines Association for Human Resources Management (AARHM) president AK Gujadhur, said that the entire staff from the top management to the grassroots level is responsible for safety levels.
HRD, however, plays an important role in enhancing flight safety by making sure that the training and other work assignments are carried out properly, he said. Besides, creation of cross-functional relationship, team building and total-quality management too need greater emphasis.
On the measures taken by local authorities to improve safety standards, the director general of civil aviation, HS Khola said that the department is making sure that all the airlines flying through India would install aircraft-collision avoidance system (A-CAS) in their aircraft by December 31. Domestic airlines, including Air India and Indian Airlines, are already nearing completion of the process.
He said the Airports Authority of India has decided to increase the runway lengths from 6,000 feet to 7,500 feet for jet aircraft. The additional length is to provide a "cushion" for aircraft. Khola said safety steps initiated by the DGCA had helped airlines save Rs 100 crore through insurance premium during the last three years.
Installations of secondary surveillance air route radar at Delhi, Calcutta, Ahmedabad, Mumbai, Chennai, Hyderabad, Guwahati and Thiruvananthapuram would help aircraft maintenance safety standards. Nagpur, Varanasi and Jharsuguda airports will be equipped with such radars by the end of next year. This would help cover the entire air route, he said adding that by 2000, all the radars would be inter-linked, enabling an ATC to examine position of an aircraft more efficiently.
Khola said that the International Civil Aviation Organization (ICAO) has made English mandatory for the cockpit staff. This caused the mid-air collision of Saudia Arabia airlines and Khazakistan airlines two years ago. The regulatory body has forwarded the inquiry report to both airlines, Khola added.
The report of the Elbee F-27 cargo flight, which went into the Arabian Sea shortly after take off from Mumbai last year was under examination, he added.
Safety is a concern of everyone who flies or contemplates it. I can provide you with volumes of information about the attention to safety given by the airline industry. No other form of transportation is as scrutinized, investigated and monitored as commercial aviation.
Yet if you decide to hold onto the belief that flying is dangerous, then these reassuring safety facts are lost to you. Statistics and figures that prove airline transportation to be the safest way to travel relate to our logical, reasoning, rational mind. Worry about safety is an intrusion that seems to bypass those faculties of logic and go directly to our emotions. And you will always find another article about some "near miss" or "the crowded skies" that will reinforce your belief.
Even if you hold the belief, "Statistics about flying don't help me," give yourself another chance to reexamine your judgment as you read through this section. After all, your goal is to feel as comfortable as possible when you fly, and there are some very comforting numbers here.
Most passengers who have knowledge of the commercial airline industry believe that flying is safe. But when something occurs that we don't understand, any of us can become quickly frightened. That's why I encourage you to study as much as you need to reassure yourself about the industry and to take some of the mystery out of commercial flight.
However, some small thing may occur on one of your flights that you haven't studied. If you become startled or frightened at that time, the statistics that I am about to present may come in handy. An airline accident is so rare, when some unfamiliar noise or bump occurs, your response need not be, "Oh, no! What's wrong?!" Instead, it can be something like, "I'm not sure what that sound was, but there's nothing to worry about." Feel free to press your overhead call button to page a flight attendant whenever you want to ask about unfamiliar sights or sounds. But you needn't jump to fearful conclusions.
Now, you may notice something a little morbid about this section: most of these statistics have to do with DEATH! This isn't the most pleasant of subjects, I know. But many people who are worried about flying concentrate on the fear that something will go wrong during the flight, and that the outcome of that error would be their own death. So let's put this possibility in perspective.
Dr. Arnold Barnett, of the Massachusetts Institute of Technology, has done extensive research in the field of commercial flight safety. He found that over the fifteen years between 1975 and 1994, the death risk per flight was one in seven million. This statistic is the probability that someone who randomly selected one of the airline's flights over the 19-year study period would be killed in route. That means that any time you board a flight on a major carrier in this country, your chance of being in a fatal accident is one in seven million. It doesn't matter whether you fly once every three years or every day of the year.
In fact, based on this incredible safety record, if you did fly every day of your life, probability indicates that it would take you nineteen thousand years before you would succumb to a fatal accident. Nineteen thousand years!
Perhaps you have occasionally taken the train for your travels, believing that it would be safer. Think again. Based on train accidents over the past twenty years, your chances of dying on a transcontinental train journey are one in a million. Those are great odds, mind you. But flying coast-to-coast is ten times safer than making the trip by train.
How about driving, our typical form of transportation? There are approximately one hundred and thirty people killed daily in auto accidents. That's every day -- yesterday, today and tomorrow. And that's forty-seven thousand killed per year.
In 1990, five hundred million airline passengers were transported an average distance of eight hundred miles, through more than seven million takeoffs and landings, in all kinds of weather conditions, with a loss of only thirty-nine lives. During that same year the National Transportation Safety Board's report shows that over forty-six thousand people were killed in auto accidents. A sold-out 727 jet would have to crash every day of the week, with no survivors, to equal the highway deaths per year in this country.
Dr. Barnett of MIT compared the chance of dying from an airline accident versus a driving accident, after accounting for the greater number of people who drive each day. Can you guess what he found? You are nineteen times safer in a plane than in a car. Every single time you step on a plane, no matter how many times you fly, you are nineteen times less likely to die than in your car.
The Airline Deregulation Act of 1978 permitted the airlines to be competitive both in the routes they flew and the fares they charged. When the price of air travel decreased, the number who flew increased. In 1977, two hundred and seventy million passengers flew on U.S. scheduled airlines. In 1987 four hundred and fifty million flew. For passengers, that resulted in the frustration of crowded terminals and delayed boardings and takeoffs. But did deregulation cause safety to be compromised? Definitely not!
Accident statistics provided by the National Transportation Safety Board show that -- despite a fifty percent increase in passengers during the ten years after deregulation -- there was a forty percent decrease in the number of fatal accidents and a twenty-five percent decrease in the number of fatalities, compared to the ten years before deregulation.
If you are going to worry about dying, there are many more probable ways to die than on a commercial jet. Take a look at the chart below, which shows the chance of fatalities on a commercial flight compared to other causes of death in the United States. Notice that you are more likely to die from a bee sting than from a commercial flight. The number one killer in the United States is cardiovascular disease, with about eight hundred and eighty-five thousand deaths per year. Each of us has about a fifty percent (50%) chance of dying of cardiovascular disease. Whenever we fly, we have a one one-hundred-thousandth of one percent (.000014%) chance of dying!
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Odds of Death |
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DEATH BY: YOUR ODDS · Cardiovascular disease: 1 in 2 · Smoking (by/before age 35): 1 in 600 · Car trip, coast-to-coast: 1 in 14,000 · Bicycle accident: 1 in 88,000 · Tornado: 1 in 450,000 · Train, coast-to-coast: 1 in 1,000,000 · Lightning: 1 in 1.9 million · Bee sting: 1 in 5.5 million · U.S. commercial jet airline: 1 in 7 million Sources: Natural History Museum of Los Angeles County, Massachusetts Institute of Technology, University of California at Berkeley |
How about accidental deaths? In the chart below you can compare the average number of airline fatalities per year (not including commuter airlines) from 1981 to 1994 with the most recent figures for other forms of accidental death. Again, you can see that flying is relatively insignificant compared to other causes of death.
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Number of Accidental Deaths Per Year By Cause |
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· 100 on commercial flight · 850 by electrical current · 1000 on a bicycle · 1452 by accidental gunfire · 3000 by complications to medical procedures · 3600 by inhaling or ingesting objects · 5000 by fire · 5000 by drowning · 5300 by accidental poisoning · 8000 as pedestrians · 11,000 at work · 12,000 by falls · 22,500 at home · 46,000 in auto accidents SOURCES: Bureau of Safety Statistics, National Transportation Safety Board |
I'm not trying to encourage you to become afraid of your bicycle or of walking down the stairs in your home. My most important point is that no one can anticipate all of your questions about flight safety and the airline industry. You may have specific questions about maintenance or security or pilot error that are not simple to address. I want to assure you that regardless of your worries, you are putting your life in the hands of an industry that has a tremendous record of dedicating its creative intelligence to your safety. And the Federal Aviation Administration, the air traffic controllers, the airline companies, the pilots, the flight attendants, the mechanics, the manufacturers are all striving to make every year safer than the year before within a highly professional industry.
Next time you begin to focus on the possibility of something going wrong on a plane, think about the probability instead. Then you will have little to worry about.
ACKNOWLEDGEMENTS
why Aeroplanes
crash : Aviation safety in the changing world
By Clinton V Master, John S Strong, C Kurt
Zorn
Crash Survivability http://wwwvnh.org/FSManual.htm
Human Tolerance limits http://wwwvnh.org/FSManual.htm
How
to Survive an air crash
The Sunday Mirror newspaper 12 June 1999
Web site : //fly.to/rak
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