Flight Simulators in Accident Investigation
Aviation crash investigations can be very difficult to undertake. The investigators must learn as much as they can about the conditions, timing, and events leading up to the incident sometimes from a very small amount of wreckage or evidence. This evidence is also often burned, charred, mangled, or corroded by the elements. Often there are no survivors or witnesses that can aid in determining the factors that led up to the event either. Government organizations like the NTSB and the FAA have to use their own insight into the conditions in place shortly before the accident in order to hypothesize about contributing factors and causes. Simulators have specific advantages and disadvantages as well as certain limitations that make them great tools for understanding part probable cause of a crash but poor tools for diagnosing the exact facts surrounding the crash. The crash facts are best recorded using equipment located within the plane itself as well as from witness statements and reports. Often there are few if any survivors of many crashes, so any information that can be used to determine the cause of a crash is extremely valuable. Full flight simulators help to synthesize this information as well as test theories and crew reactions to specific events and conditions.
Often all these agencies have to begin their investigations from are the flight data recorder and the cockpit voice recorders recovered from the crash site. These recorders are sometimes referred to as “black boxes” help to show investigators the exact conditions just prior to the crash. These recorders are invaluable to investigators. Besides the black boxes, investigators can help to recreate the accident environment using a full flight simulator. This allows the investigators to pause or rewind the conditions and aircraft and crew responses at any given time, so further, more in depth review can be accomplished from a stop-motion standpoint.
The flight data recorder provides a wealth of invaluable information. More specifically it monitors and records flight parameters such as airspeed, altitude, and heading as well as many others (NTSB, 2010). By regulation, newly manufactured aircraft must record a minimum of eighty-eight specific parameters. These measurements are stored in digital form unlike the older style which used magnetic tape to record the in-flight parameters, and which was sometimes damaged or destroyed to the point where the tapes were no longer readable. The flight data recorder is usually installed in the aircraft’s tail section, which is statistically the most survivable part of the aircraft. (NTSB, 2010) The recorders themselves also have a switch that is engaged after a certain G. limit is reached where a “pinger” begins to transmit a signal to recovery teams of the whereabouts of the recorders. These beacons are able to operate underwater at depths of over 14,000 feet as well as in any weather situation (NTSB, 2010). The flight data recorders are reviewed after an accident to get a clear picture of the aircraft’s behavior shortly before an accident. The investigators can also use this information to generate a video of the aircraft’s flight path and specific behavior that could possibly lead to explanations or theories about why the aircraft crashed.
Cockpit voice recorders are also key pieces of evidence in many crashes. These devices work in a similar way to the flight data recorder, except they record the cockpit conversations and interactions (NTSB, 2010). This can be crucial when there are no survivors to relate to the investigators exactly what occurred in the cockpit seconds before the crash. Besides recording voices they also record noises inside the cockpit like stall warning horns and other important happenings. When used in conjunction with other reported parameters, the cockpit voice recorded can help investigators come up with a probable cause.
Flight simulators are capable of not only simulating normal flight conditions, but like many other computer programs and modeling software, they can simulate conditions that may not be duplicated in real life, or abnormal conditions that the pilots and flight crew may have faced to see how a similarly-trained pilot or crew member would react. This can go a long way in explaining exactly how accidents occur. The parameters from the flight data recorders can be input into the simulator to give investigators a real-time account of how the plane was affected by certain conditions whether that means systems failures, weather issues, or crew issues (NTSB, 2010). This is very useful because air crashes are often the result of a complex mixture of factors both mechanical and human in nature. Simulators are excellent for analyzing malfunction and scenario-based situations and crash recreation. They often also help investigators successfully understand the sequence of malfunction or the manner and rate at which information is provided to the pilot. In this way, simulators are also excellent at evaluating time frames at which events occur (Tydeman, 2004).
Flight simulators are also excellent tools in evaluating exactly how a pilot or group of pilots responds to a scenario (Tydeman, 2004). This helps to assess exactly how each pilot was taught to deal with a problem, and if their training had anything to do with the events leading up to the crash. This form of analysis is common in many accident investigations that are investigating pilot errors or human judgment issues. They can even be used as tools to evaluate whether or not current training practices are sufficient or reliable when pilots have to use their training to avoid a crash (Anders, 2001). Pilot workloads and stress factors can be studied in the simulator in order to obtain clear information relative to how the pilots function and what points in the pilot’s routines are most dangerous or lacking of safety nets. In one such simulator study, pilots were asked to fly an approach and landing under different circumstances and conditions. The more stressful their surroundings and prevailing conditions were, the less likely they were able to successfully divide their attention in a way that was safe and comprehensive enough to complete a landing (Anders, 2001). This direct example of full flight simulator use to identify weak points in pilot training and actions helps to illustrate the power of these simulators as tools to diagnose the same weak points that could have possibly led to a crash.
Weather is another key factor in many accidents and crashes. It is nearly impossible to exactly duplicate the weather conditions during any particular point, but the aircraft’s systems, avionics, and pilots all react differently to certain weather conditions. Flight simulators can be used to both test theories about probable causes of a crash due to weather as well as determine if a weather-related incident was survivable based upon a similarly trained pilot flying the scenario in the simulator (Tydeman, 2004). There are some major limitations when using flight simulators to conduct weather-related research and investigations.
First of all, each pilot has a unique experience base, which can include more or less experience with inclement weather. This experience can play a major role in aircraft accidents due to the fact that experienced pilots often feel overly confident of their abilities in poor weather situations. This can lead to bad decisions being made or a chain of events that starts with a single error in judgment (Schwartz and Hahn, 2006). This is not something that can be simulated in a full flight simulator. Also, the aircraft itself stresses and fatigues in its own way, and if weather did play a role in an air crash, it is often hard to recreate or simulate the exact role it played given that each aircraft is in a different mechanical condition at the time of flight.
Flight simulators also have limitations that real-life scenarios do not. Author Robin Tydeman (2004) describes some of these limitations in his paper. These limitations include the fact that the simulator itself is not an exact model of the cockpit and surrounding areas as well as the fact that the simulator can be used to predict or give a “best guess” or hypothesis, but it cannot definitively give answers to some of the most troubling of questions surrounding air crashes. Another key limitation to full flight simulators is the fact that during stalls and upset flight attitudes, the gravitational forces and accompanying disorientation are not easily duplicated (Levin, 2010). This leads investigators to draw certain conclusions based upon how a pilot might react in a situation that cannot be simulated. This represents another unknown in the world of accident investigation and often leaves investigators frustrated.
Full flight simulators are invaluable crash investigation tools that help to both recreate certain conditions as well as test hypotheses. They are an excellent way to analyze fault systems and timelines as well as give investigators additional insight into what the pilot and crew may have been thinking moments before the crash. They have been used extensively to develop training material and methods to better prepare flight crews for specific situations and scenarios they are likely to encounter. However, full flight simulators also have some limitations, which make them poor tools for research and investigations depending on the specifics of the crash and the needs for the investigators reviewing the case.
Full flight simulators do not accurately simulate severe aircraft flight attitudes and conditions. They are also not perfect modelers of reality, as they cannot model the specific conditions that the aircraft itself as well as the flight crew were under. However, since there are rarely survivors of major plane crashes, it is difficult to interview witnesses or people who were on board the aircraft in order to obtain some sort of picture of the time leading up to the crash. Full flight simulators can be used to simulate conditions without risking people or machinery in the process. They are excellent tools for “best Guess” and probable cause findings, but they should be used in conjunction with more traditional investigational methods in order to come up with any concrete findings. Full flight simulators will likely be used in the future to help in accident investigations. They are a key component in the investigators’ toolbox along with the actual records that are stored digitally on devices located inside the aircraft itself. The cockpit voice recorder as well as the flight data recorders can be analyzed to come up with a viable model for the crash, which can then be modeled and tested in a full flight simulator.
References
Anders, G. (2001). “Pilot’s Attention Allocation During Approach and Landing.” Institute for Aeronautics and Astronautics. Berlin.
Levin, Alan. (2010). “Simulator training flaws tied to air crashes.” USA Today. Website accessed 15 Oct. 2010 at: http://travel.usatoday.com/flights/2010-08-31-1Acockpits31_ST_N.htm.
National Transportation Safety Board. (2010). “Cockpit Voice Recorders and Flight Data
Recorders.” NTSB Website accessed 15 Oct. 2010 at: http://www.ntsb.gov/aviation/cvr_fdr.htm.
Schwarz, Carsten Walter and Hahn, Klaus-Uwe. “Full-flight simulator study for wake vortex hazard area investigation.” Aerospace Science and Technology. Vol. 10, No. 2. Pp. 136-143.
Tydeman, Robin. (2004). The Use of Full Flight Simulators for Accident Investigation. The Australian Society of Accident Investigators Presentation, Sydney.
