Aircraft Accident Investigation - Research Paper Example

Running head: AIRCRAFT ACCIDENT INVESTIGATION Aircraft Accident Investigation Abstract Aircraft accident investigation is of significance to the aviation industry to find out probable reasons that lead to aircraft accidents. These reasons are found through investigation to prevent such equipment or human error from recurring since aircraft accident leads to the loss of several lives. Thus transportation safety boards of respective governments take up the initiative to locate available clues and arrive at a conclusion about the reasons that lead to aircraft accidents. Aircraft accident investigation is not aimed to blame a person or company but to avoid the recurrence of such events in future flights of aircrafts. The details collected from accidents are studied to find possible solution for similar circumstances. Aircraft Accident Investigation Investigation into aircraft accidents or incidents is conducted to prevent the recurrence of such incidents and accidents in future. The investigation is not conducted to blame or hold someone liable but to prevent and find solution to similar circumstances. In the event of an aircraft accident, it is investigated by a government under whose area of jurisdiction, the plane has gone down. The investigation of aircraft accidents are conducted according to the recommended practice and international standards as laid down in ICAO Annex 13 that pertains to Aircraft accident and incident investigation. The initial phase of an aircraft accident investigation is usually concluded in a few weeks or days while the final investigation report and recommendations usually take years for completion. The final investigation report comprises of factual data about the aircraft accident, analysis and the probable cause and also has recommendations for safety (Accident investigation 2009). Aircraft Accident Investigation is carried out to find out the events that lead to the accident. The investigation begins with the search for the details of the airline’s data, equipment, people and environmental issues and then moves on to a broad discussion in the investigation process. Most of the investigation involves the reconstruction of the incident from available data. (Endsley & Garland 2000 p.101) Investigators may not be able to avail direct information related to the flight crew but have to arrive at a decision from the inferences obtained from flight data recorders. The data pertains to the personnel critical to the reason for the accident and the equipment and the environment when the particular personnel operated the equipment. Investigators verify the sample of data to gather the necessary information to fulfill the goals of the investigation. The quality of the data is important and should be internally logical, consistent and sequentially correct. The data collected from various sources pertaining to the accident investigation have to contain the parameters to apply comparable logic and description of similar events in a specific sequence that finally lead to the cause of the accident. Majority of aircraft accidents occur due to a series of errors or error committed by a person critical for handling the flight. The data collected by investigators explain the performance of the person’s task and the state of the person’s physical and behavioral health when the accident occurred. The source of information comprises personnel, medical and training records and the portrayal of the person with those who knew the person. The equipments that give information about the cause of the accident are control surface positions, non-volatile memory contents, instrument reading, circuit and switch breaker positions and site damage that give critical insight into the condition of the aircraft before the accident and offers clues to understanding the accident. For instance, pre-impact fire damage displays different patterns of smoke than post impact fire. Further, aircraft wreckage also gives clues about an accident while flying in the right path with concentrated wreckage thus explaining various types of accident causes and sequences. The most crucial equipment supplied data is obtained from the recorders used in air transport aircraft that consistently sample information on the operation and status of the aircraft (Endsley & Garland 2000 p.102) The probable cause of aircraft accidents is normally obtained from the Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR) which are called the Black boxes (CVR / FDR 2009). The transcription of ATC or CVR tape is not a definite science but it is a good method to arrive at conclusion about what happened during an aircraft accident. The transcript is not a definite science because if any of the message is understood out of context it can mislead the investigation. Hence, ATC or CVR transcripts should be considered only as an investigative tool that is used along with other available evidence. Therefore, interpretations and conclusions of an investigation should not be made solely by depending on the transcript as a source of information. In addition to the use of transcripts in investigation, it is used for educational purposes so that the reader can have a better knowledge about the circumstances that led to accident (Transcripts 2009). Flight 261 of Alaska Airlinenes plunged into the Pacific Ocean en route to Seattle, WA from Puerto Vallarta, Mexico. After one hour and forty five minutes flight there was a problem with the stabilizer trim of the plane. Though a ten minute effort was made by the pilots to fly the plane, the efforts went futile, killing all 88 people on board. There are several unanswered questions regarding the reasons that bring down the plane when there is an airplane crash. In the case of Flight 261, there were 48 parameteres of flight information and the CVR had recorded more than thirty minutes of conversation and other noises in the cockpit. Whenever an airplace accident takes place in the United States, the National Transportation Safety Board’s safety investigators start the search for the black boxes of the aircraft. Black boxes are recording devices that reveal details of the event that occur immediately before the accident and can survive crashes (Bonsor). According to L-3 communication’s documents, the Wright Brothers first used a device to register propeller rotations. But the wide use of aviation recorders began only after the Second World War period. The recording medium using black boxes have evolved since then to record as much information about the operations of an aircraft. Magnetic tape is used in many of the current black boxes which was the material first used in the 1960’s. The magnetic tape is now being replaced by solid state memory boards that came up in the 1990’s. A magnetic tape functions similar to a tape recorder where a Mylar tape pulls across an electromagnetic field that leaves a bit of information on the tape. Currently, Black box manufacturers do not use magnetic tape recorders, instead they have fully transitioned to use solid state technology (Bonsor p.1). Solid state recorders are preferred and are reliable than magnetic tape counterparts. Solid state technology uses stacked rows of memory chips without any moving parts. The absence of moving parts results in lesser maintenance problems and decreased chances of breaking when a crash occurs. The data from both FDR and CVR is stored in the stacked memory boards within the (CSMU) crash survivable memory unit. The recorders manufactured by L-3 communications have a CSMU with a cylindrical compartment in the recorder. The size of the stacked memory board is around 1 inch tall (2.54 cm) and 1.75 inches in diameter (4.45 cm). The memory boards in solid state has adequate digital storage space to record twenty five hours of flight information for FDRs and two hours of audio information for CVR. Airplanes are fitted with sensors that can collect informaiton. The airplane is also fitted with sensors that detect airspeed, acceleration, altitude, outside temperatur, flap setting, engine performance, cabin pressure and temperature and more. Solid state recorders can manage more 700 parameters in larger aircraft while magnetic tape recorders can manage only around 100 parameters. The information gathered by the sensors of the airplane is passed on to FDAU (Flight data acquisition unit) located in the front of the craft. The device is usually placed under the cockpit in a space called electrnoic equipment bay. The FDAU mediates and manages the complete data recording process. The FDAU collectes the data from sensors and passes it to the black boxes. Black boxes obtain power from one of the two power generators that gain power from the engines of the plane. One generator is 115 volt, 400 Hz AC power source and the other is 28 volt DC source power. These are the power supply measurements of a standard aircraft (Bonsor p.2). Almost all commercial aricrafts are built with a number of microphones in the cockpit in order to tract the details of communication of the crew in the flight. The microphones are also enabled to track probable ambiet sound in the cockpit like thuds, knocks or any switches being thrown. An aircraft has upto four microphones in the cockput that are connected to the CVR (cockpit voice recorder). In the CVR the recorded sound is digitized and stored. The associated control unit in the cockput provides pre amplification for the sounds that move into the CVR. The four microphones are placed in the pilot’s headset, co-pilot’s headset, center of the cockpit and in the headset of the third crew member in the cockpit. Most magnetic-tape CVRs store the last 30 minutes of sound. They use a continuous loop of tape that completes a cycle every 30 minutes. As new material is recorded, the oldest material is replaced. CVRs that used solid-state storage can record two hours of audio. Similar to the magnetic-tape recorders, solid-state recorders also record over old material (Bonsor p.3) CVR recordings hold significant clues to the reason for the accident. The conversation in the cockpit in Flight 261 of Alaska Airlines between the first officer and the captain gave clue to the NTSB investigators that the plance went down due to problems in the plane’s stabilizer (Bonsor p.4) The operating data of the plane’s system is recorded by the Flight Data Recorders. The sensors in the recorders are wired from differed areas of the aricraft to the flight information acquisition unit that is linked to the FDR. In the event of turning on or off of a switch it is recorded in the FDR. The Fedreal Aviation Administration of the United States requires all commercial airlines to record at least eleven to twenty nine parameters based on the aircraft’s size. According to FAA’s July 17, 1997, Code of Regulation, it requires aircrafts manufactured post August 19, 2002 to record a minimum of 88 parameters during a flight. Some of the parametrs usually recorded by FDR’s are pressure altitude, time, airspeed, magnetic heading, vertical acceleration, control-column position, control-wheel position, rudder-pedal position, fuel flow and horizontal stabilizer. Solid state recorders are capable of tracking more parameters when compared to magnetic tape because it allows faster flow of data. The capability of solid state FDR ro store 25 hours of flight data and the recording of every additional parameters by the FDR provides investigators with more clues towards the reason for the accident. (Bonsor p.5) The devices that survive airline accidents are only the CSMU or crash survivable memory units comprising the cockpit voice recorders and flight data recorders. The accessory units of recorders like inner components and chassis are mangled. Crash survivable memory unit is a large cylinder that is fixed into the flat part of the recorder. The device is engineered to survive extres heat, tons of pressure and violent crashes. In the magnetic tape recorders, the crash survivable memory units were placed within a rectangular box.The CSMU protects and insulates the solid state black box with three layers of materials that stack memory boards and store the digitized data (Bonsor p.6). When a crash occurs, investigators search for the black boxes. The aviation recorders are painted bright orange with strips of reflective tape on the exteriors to assist the investigators to locate them after an accident. The color is of specific help when a plane goes down in the water. The name black box has been given to the recording boxes because the early recorderes were black in color and another reason is because the boxes turn black after accident fires. Black boxes are also fitted with Underwater Locator Beacon (ULB), a cylindrical object at the end of the device which serves additionally as a handle. When a place lands in water, the beacon emanates ultrasonic pulse not audible to human ears but that can be easily detected by an acoustical and sonal locating equipment. A submergence sensor is fitted to the side of beacon which resembles a bull’s eye. The beacon is activated when the sensor touches water. The beacon emanates pulses at 37.5 kHz that transmits sound from a depth of 14000 feet or 4,267m. After the beacon starts pinging, the continues once for every second for 30 days. The battery fitted in the beacon has a six year shelf life though in rare circumstances, the beacon gets snapped off after high impact collision. During Aircraft Accident Investigation in United States, the investigators take the black box to computers labs of the NTSB (National Transportation Safety Board). Due care is given while transporting the devices to prevent damage to the recorders. While investing aircraft water accidents, the recorders are covered with cool water to avoid drying out of the devices. This is to preserve the condition of the recorder until it can be technically handled. By placing it in a bucket of water, the recorders are being placed in the same environment from where it was retrieved before it is properly disassembled (Bonsor p.8). The data from the black boxes is downloaded by the investigators at a lab and they try to recreate the incidents that led to the accident. The process of downloading information from the recorders may take months or weeks to complete. The manufactures of black box in the United States supply the NTSB with the required software and readout system required for the complete analysis of the information stored in the recorders. Invetigators can quickly play the recorder back by connected the device to a readout system in case there is no damage to the FDR. When solid state recorders are used, investigators can read out the stored information in a few minutes. Usually, the recorders retrieved from accidents are burned or dented. Recorders retrieved in this state are disconnected from the memory boards, cleaned up and then a new cable with memory interface is installed. The memory board is then connected to a recorder in working condition. The recorders is fitted with a special software to support the retrieval of information without overwriting the data in the black boxes. The data stores in the CVR is interpreted by availing the services of a team of experts. The team usually comprises of representation from the aircraft’s manufacture, an expert from the airline, a special from NTSB transportation safety and an investigator from NTSB air safety. A language specialist of the FBI also joins the expert team in certain cases with the services of an interpreter if required. The board makes effort to interpret at least thirty minutes of conversation that includes sounds and words recorded by the CVR. The process can be painstaking and take weeks for its completion. The CVR and FDR are invaluable devices for an aircraft investigation since these are the only survicors of aircraft accidents and provide clues for the reason of the accident which is otherwise impossible to obtain through any other means. With the evolution of technology, black boxes will have a considerably more important role in the investigation of aircraft accidents (Bonsor p.9). The investigation of aricraft accidents are set to reach a milestone with the development of black boxes that can record video images of the cockpit according to the black box manufacturers L3 communications. With such black boxes, the recorders can store video clips in the memory of solid state (Bonsor p.10). The NTSB begins the investigation of aircraft accidents by forming a Go Team. A Go team is a team of investigators on call for emergency assignments during the investigation of major aircraft accidents. Laboratory support and specialists are provided from the Office of Research and Engineering and the Office of Aviation Safety. Regional investigators form a member of the Go Team when the investigators from the headquarters are unavailable and as per the requirement of the investigation. A complete Go Team comprises of specialists in meteorology, air traffic control, human performance, systems, structures, operations, power plants, survival factors, maintenance records, aircraft performance, flight data recorder, cockpit voice recorder and metallurgy (National Transportation Safety Board 2002 p.1). Early data regarding the circumstances and facts of the accident will be erroneous and incomplete. Therefore factual information availed for alerting purpose has to be handled with required discretion. The preliminary status of the information should be notified to all concerned in the investigation. Aircraft accident investigation begins when the Safety Board’s Communication Centers receives notification about an accident (National Transportation Safety Board 2002 p.2). The center offers a centralized operation to assist all modes of transportation during the investigative process. The Go Team is given important preliminary information about the accident before beginning the investigation. Required logistic support is also provided and the Go Team then forms an on scene command post. The investigation then continues with the number of fatalities / injuries, type of aircraft and the like (National Transportation Safety Board 2002 p.3). The Safety Board offers the status of a party to organizations that provide required technical support to the investigation which include labor organizations, power plant manufacturers, aircraft, systems and operator due to the circumstances of the accident (National Transportation Safety Board 2002 p.5) A room for press meeting has to be arranged at the command post (National Transportation Safety Board 2002 p.9). Progress meeting are conducted at the site to broadcast information received during a particular day and discuss activities for further investigation. Factual information is given to the media and to the family (National Transportation Safety Board 2002 p.20). The parts of the wreckage is listed in detail with description of components and parts and those significant for the investigation is retained by the National Transportation Safety Board for subsequent examination. Other parts are sent to the owner of the aircraft (National Transportation Safety Board 2002 p.25) A status or progress report is prepared regarding the latest investigation inferences with a summary for factual reports. If there is a public hearing the accident investigation report is given to the public simultaneously when the report is given to the press (National Transportation Safety Board 2002 p.32). In conclusion, aircraft accident investigations are crucial to prevent the recurrence of similar crashes that are caused due to human or equipment error. The information gathered after an accident is compiled to reach a conclusion about the reasons for the accidents. The retrieval of black boxes from the wreckage whether it is in land or in water, is important because it serves as a key source to obtain information about the last few minutes of the flight’s operation. Further, the black boxes record the conversation and noise in the cockpit which gives information about the problems faced by the crew. The initiative of transportation safety boards to investigate aircraft accidents as per procedures enables airline operators to use safety measures and recommendations in flights to prevent loss of lives. Reference Accident investigation 2009 Available: http://aviation-safety.net/investigation/ Accessed on July 12, 2009. Bonsor, K. How Black Boxes Work Available: http://electronics.howstuffworks.com/gadgets/other-gadgets/black-box1.htm Accessed on July 12, 2009. CVR / FDR 2009 Available: http://aviation-safety.net/investigation/cvr/ Accessed on July 12, 2009. Endsley, M.R. & Garland, D.J. 2000 Situation Awareness Analysis and Measurement Philadelphia: Lawrence Erlbaum Associates National Transportation Safety Board 2002 Available: http://www.ntsb.gov/Aviation/Manuals/MajorInvestigationsManual.pdf Accessed on July 12, 2009. Transcripts 2009 Available: http://aviation-safety.net/investigation/cvr/transcripts/ Accessed on July 12, 2009. Read More