Tag Archives: fatalities

Root Cause Analysis - Incident Investigation

Deadly Train Derailment Near Philadelphia

By Kim Smiley

On the evening of May 12, 2015, an Amtrak train derailed near Philadelphia, killing 8 and injuring more than 200.  The investigation is still ongoing with significant information about the accident still unknown, but changes are already being implemented to help reduce the risk of future rail accidents and improve investigations.

Data collected from the train’s onboard event recorder shows that the train sped up in the moments before the accident until it was traveling 106 mph in a 50 mph zone where the train track curved.  The excessive speed clearly played a role in the accident, but there has been little information released about why the train was traveling so fast going into a curve.  The engineer controlling the train suffered a head injury during the accident and has stated that he has no recollection of the accident. The engineer was familiar with the route and appears to have had all required training and qualifications.

As a result of this accident and the difficulty determining exactly what happened, Amtrak has announced that cameras will be installed inside locomotives to record the actions of engineers.  While the cameras may not directly reduce the risk of future accidents, the recorded data will help future investigations be more accurate and timely.

The excessive speed at the time of the accident is also fueling the ongoing debate about how trains should be controlled and the implementation of positive train control (PTC) systems that can automatically reduce speed.  There was no PTC system in place at the curve in the northbound direction where the derailment occurred and experts have speculated that one would have prevented the accident. In 2008, Congress mandated nationwide installation and operation of positive train control systems by 2015.  Prior to the recent accident, the Association of America Railroads stated that more than 80 percent of the track covered by the mandate will not have functional PTC systems by the deadline. The installation of PTC systems requires a large commitment of funds and resources as well as communication bandwidth that has been difficult to secure in some area and some think the end of year deadline is unrealistic. Congress is currently considering two different bills that would address some of the issues.  The recent deadly crash is sure to be front and center in their debates.

In response to the recent accident, the Federal Railroad Administration ordered Amtrak to submit plans for PTC systems at all curves where the speed limit is 20 mph less than the track leading to the curve for the main Northeast Corridor (running between Washington, D.C. and Boston).  Only time will tell how quickly positive train control systems will be implemented on the Northeast Corridor as well as the rest of the nation, and the debate on the best course of action will not be a simple one.

An initial Cause Map, a visual root cause analysis, can be created to capture the information that is known at this time.  Additional information can easily be incorporated into the Cause Map as it becomes available.  To view a high level initial Cause Map of this accident, click on “Download PDF”.

Root Cause Analysis - Incident Investigation

Earthquake Hits Nepal

By Kim Smiley

As anyone paying any attention to the news knows, a magnitude 7.8 earthquake hit Nepal on April 25, 2015.   The same forces that created the Himalayan Mountains are still at work in the region as the Indo-Australian Plate slowly slides under the Eurasian Plate and experts have long warned about the potential for an earthquake in this location.

At least 4,600 people were killed as a result of the earthquake and the United Nations has stated that 8 million people have been affected.  Many people impacted by the disaster lack adequate water and food and are living in temporary shelters without sanitation facilities.  Beyond the sheer scope of the natural disaster, providing emergency assistance has also been difficult because some of the affected villages are in remote locations that are challenging to access and many roads were damaged by the earthquake.  The long-term economic impacts are also predicted to be large because of the significant damage to infrastructure and the fact that local economies relay heavily on tourism.

A Cause Map, a visual root cause analysis, can be built to help understand this disaster better. A Cause Map lays out the cause-and-effect relationships in an intuitive format by asking “why” questions.  In this tragic example, asking why so many fatalities occurred shows that the majority of deaths were caused by collapsing buildings.  Many buildings in the impacted area were unreinforced masonry structures that couldn’t withstand the force of the earthquake.  These buildings are cheaper and quicker to build than more modern construction that would meet building codes designed to survive an earthquake.

Civil unrest in the region has resulted in rapid urbanization and a large demand for housing as people moved into cities. Rapid and relatively unregulated urbanization in a country with one of the lowest per capita incomes in the world proved to be a deadly combination in a region prone to earthquakes. Historically a major earthquake has struck this region about every 75 years and this one had long been predicted.  Says Susan Hough, a geologist with the U.S. Geological Survey, “It was clearly a disaster in the making that was getting worse faster than anyone was able to make it better. You’re up against a Himalayan-scale problem with Third World resources.”

Every disaster and the emergency response to it should be studied to see if there are any lessons learned that can be used to save lives and minimize damage in the future. There is clearly no “solution” that can prevent an earthquake, but even when dealing with a natural disaster there are ways the impact of a disaster could be mitigated.  The possible solutions may not be cheap or easy, but it is important to remember that it is possible. You can’t stop the earthquake, but you can work to build stronger buildings.

Root Cause Analysis - Incident Investigation

Concrete slab smashes truck killing 3

By Kim Smiley

On April 13, 2015, a large section of a concrete barrier fell from an overpass onto a truck in Bonney Lake, Washington. A couple and their baby were in the vehicle and were all killed instantly. Investigators are working to determine what caused this accident and to determine why the road under the overpass remained open to traffic while construction was being done on the overpass.

A Cause Map, a visual method of root causes analysis, can be built to help understand this accident. More information is still needed to understand the details of the accident, but an initial Cause Map can be created now to capture what is known and it can be easily expanded to include additional information as it becomes available. A Cause Map is created by asking “why” questions and visually laying out the answers to show the cause-and-effect relationships. (Click here to learn more about basics of Cause Mapping.)

In this accident, three people were killed because the vehicle they were riding in was smashed by a large slab of concrete. The vehicle was hit by the concrete slab because it was accidently dropped and the truck was under the overpass at the time it fell because the road was open to traffic. (When two causes are both needed to produce and effect, the causes are listed on vertically on the Cause Map and separated by and “and”.) The road would typically have been closed to traffic while heavy work was performed on the overpass, but the work plan for the construction project did not indicate that any heavy work would be performed on the day of the accident.   At some point the actual work schedule must have deviated from the planned schedule, but no change was made in plan for managing traffic resulting in traffic traveling under the overpass while potentially dangerous construction was performed.

Investigators are still working to understand exactly why the concrete slab fell, but early indication is that temporary metal bracing that was supporting the concrete may have failed due to buckling. The concrete barrier on the overpass were being cut into pieces at the time of the accident so that they could be removed as part of a $1.7 million construction project to improve pedestrian access which included adding sidewalks and lights.

Once the details of what causes this tragic accident are better understood, solutions can be developed and implemented that will help reduce the risk of something like this happening again. To view a high level Cause Map of this accident, click on “Download PDF” above.

You can also read a previous blog “Girder Fell on Car, Killing 3” to learn more about a similar accident that occurred in 2004.

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March 27, 1977: Two Jets Collide on Runway, Killing 583

By ThinkReliability Staff

March 27, 1977 was a difficult day for the aviation industry.  Just after noon, a bomb exploded at the Las Palmas passenger terminal in the Canary Islands.  Five large passenger planes were diverted to the Tenerife-Norte Los Rodeos Airport, where they completely covered the taxiway of the one-runway regional airport.  Less than five hours later, when the planes were finally given permission to takeoff, two collided on the runway, killing 583, making this the worst accident at the time (and second now only to the September 11, 2001 attacks in the US.)

With the benefit of nearly 40 years of hindsight, it is possible to review the causes of the accident, as well as look at the solutions implemented after this accident, which are still being used in the aviation industry today.  First we look at the impact to the goals as a result of this tragedy.  The deaths of 583 people (out of a total of 644 on both planes) are an impact to the safety goal.  The compensation to families of the victims (paid by the operating company of one of the planes) is an impact to the customer service goal.  The property goal was impacted due to the destruction of both the planes, and the labor goal was impacted by the rescue, response, and investigation costs that resulted from the accident.

Beginning with one of the impacted goals, we can ask why questions to diagram the cause-and-effect relationships related to the incident.  The deaths of the 583 people onboard were due to the runway collision of two planes.  The collision occurred when one plane was taking off on the runway, and the other was taxiing to takeoff position on the same runway (called backtracking).

Backtracking is not common (most airports have separate runways and taxiways), but was necessary in this case because the taxiway was unavailable for taxiing.  The taxiway was blocked by the three other large planes parked at the airport.  A total of five planes were diverted to Tenerife which, having only one runway and a parallel taxiway, was not built to accommodate this number of planes.  There were four turnoffs from the runway to the taxiway; the taxiing plane had been instructed to turn off at the third turn (the first turn that was not blocked by other planes).  For unknown reasons, it did not, and the collision resulted between the third and fourth turnoff.  (Experts disagree on whether the plane would have been able to successfully make the sharp turn at the third turnoff.)

One plane was attempting takeoff, when it ran into the second plane on the runway.  The plane  taking  off was unaware of the presence of the taxiing plane.  There was no ground radar and the airport was under heavy fog cover, so the control tower was relying on positions reported by radio.  At the time the taxiing plane reported its position, the first plane was discussing takeoff plans with the control tower, resulting in interference rendering most of the conversation inaudible.  The pilot of the plane taking off believed he had clearance, due to confusing communication between the plane and the air traffic control tower.  Not only did the flight crews and control tower speak different languages, the word “takeoff” was used during a conversation that was not intended to provide clearance for takeoff.  Based on discussions between the pilot and flight crew on the plane taking off have, investigators believed, but were not able to definitively determine, that other crew members may have questioned the clearance for takeoff, but not to the extent that the pilot asked the control tower for clarification or delayed the takeoff.

After the tragedy, the airport was upgraded to include ground radar.  Solutions that impacted the entire aviation industry included the use of English as the official control language (to be used when communicating between aircraft and control towers) and also prohibited the use of the word “takeoff” unless approving or revoking takeoff clearance.  The potential that action by one of the other crew members could have saved the flights aided in the concept of Crew Resource Management, to ensure that all flight crew members could and would speak up when they had questions related to the safety of the plane.

Though this is by far the runway collision with the greatest impact to human life, runway collisions are still a concern.  In 2011, an Airbus A380 clipped the wing of a Bombardier CRJ (see our previous blog).  Officials at Los Angeles International Airport (LAX) experienced 21 runway incursions in 2007, after which they redesigned the runways and taxiways so that they wouldn’t intersect, and installed radar-equipped warning lights to provide planes with a visual warning of potential collisions (see our previous blog).

To view the outline, Cause Map and recommended solutions from the Tenerife runway collision of 1977, click on “Download PDF” above.  Or, click here to read more.

Root Cause Analysis - Incident Investigation

Deadly Train-Car Collision

By Kim Smiley

On February 3, 2015, an SUV was struck by a commuter train near Valhalla, New York.  The driver of the vehicle and 5 train passengers were killed in the accident.  The National Transportation Safety Board (NTSB) is investigating the accident to determine what went wrong.

An initial Cause Map, a visual root cause analysis, can be built to analyze and document what is known about this train-car collision.  A Cause Map visually lays out the cause-and-effect relationships that contributed to an issue and focuses on understanding all the causes, not THE root cause.  Generally, identifying more causes results in a greater number of potential solutions being considered.

So why did the train hit a vehicle?  Eyewitnesses have stated that the SUV was hit by a crossing gate as it descended.    It is not clear why the SUV didn’t stop prior to entering the railroad crossing area. The driver pulled the SUV forward onto the tracks rather than backing up and the train struck the vehicle shortly after.  Investigators don’t know why the driver stopped on the tracks, but initial reports are that all safety features, such as the crossing gate, signs and train horn, were functioning properly at the time of the accident.

Unfortunately, it’s not unusual for passengers in a vehicle struck by a train to be injured or killed, but it is less common for fatalities among the train passengers.  Investigators are working to determine what made this accident particularly dangerous for train passengers.  The NTSB plans to use information about the passengers’ injuries and a diagram of where people were sitting on the train to try to understand what happened during the collision.  Post-accident photos of the train show that significant fire damage occurred, likely fueled by the gas in the SUV.

One of the open questions is whether the electrified third rail contributed to the accident and subsequent injuries. Metro-North uses an unusual “under-running” third rail design where power is taken from the bottom of the rail.  During the collision, 400 feet of the third rail broke apart and 12 pieces pierced both the SUV and the train. This rail design uses a metal shoe that slips underneath the third rail and some think that the force of the collision may have essentially pried up the rail and threw it into the train and vehicle.

Open questions can be documented on the initial Cause Map with a question mark.  As more information becomes available, the Cause Map can quickly be updated.  Typically, Cause Maps are built in Excel and different versions can be saved as different sheets to document the investigation process.

Click on “Download PDF” above to view an initial Cause Map of this accident, built from the information in the media articles on the accident.

Root Cause Analysis - Incident Investigation

TransAsia Plane Crashes into River in Taiwan

By Kim Smiley

On February 4, 2015, there were 53 passengers onboard TransAsia Airways Flight 235 when the plane crashed into the Keelung River shortly after taking off from the Taipei Shonshan Airport.  There were 15 survivors from this dramatic crash where the plane hit a bridge and taxi cab prior to turning upside down before hitting the river. (The crash was caught on video by dash cameras from a vehicle on the bridge and can be seen here.)

Investigators are still working to determine exactly what happened, but some early findings have been released.  The plane involved in this crash was a turboprop with two engines.  This model of plane can fly safely with only one engine, but both engines had issues immediately prior to the crash so the pilots were unable to control the plane.

Data from the flight recorder shows that the right engine idled 37 seconds after takeoff.  No details about what caused the problem with the right engine have been made available.  The initial investigation findings are that the left engine was likely manually shut down by the pilots.  It’s not clear why the functioning engine would have been intentionally shut down. Early speculation is that it was a mistake and that the pilots were attempting to restart the idled right engine when they hit the switch for the operating left engine.

The investigation into the crash is ongoing and the final report isn’t expected to be released for about a year, but based on the initial findings, a few solutions to help reduce the likelihood of future crashes have already been implemented.  TransAsia has grounded most of its turboprop aircraft pending additional pilot instruction and requalification because it is believed that pilot action may well have contributed to the deadly accident.  More than 100 domestic flights have been canceled as a result.  Additionally, Taiwan’s Civil Aeronautic Administration has announced that the carrier will be banned from adding new international routes for 12 months.  A previous crash in July 2014 had already tarnished TransAsia’s reputation and this latest disaster will certainly be scrutinized by the authorities.

An initial Cause Map, a visual root cause analysis, can be built to analyze the information that is available on this crash and to document where there are still open questions.  To view a Cause Map and Outline of this incident, click on “Download PDF” above.

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Working Conditions Raise Concerns at Fukushima Daiichi

By ThinkReliability Staff

The nearly 7,000 workers toiling to decommission the reactors at Fukushima Daiichi after they were destroyed by the earthquake and tsunami on March 11, 2011 face a daunting task (described in our previous blog). Recent events have led to questions about the working conditions and safety of these workers.

On January 16, 2015, the local labor bureau instructed the utility that owns the plants to reduce industrial accidents. (The site experienced 23 accidents in fiscal year 2013 and 55 so far this fiscal year.) Three days later, on January 19, a worker fell into a water storage tank and was taken to the hospital. He died the next day, as did a worker at Fukushima Daini when his head got caught in machinery. (Fukushima Daini is nearby and was less impacted by the 2011 event. It is now being used as a staging site for the decommissioning work at Fukushima Daiichi.)

Although looking at all industrial accidents will provide the most effective solutions, often digging into just one in greater detail will provide a starting point for site improvements. In this case, we will look at the January 19 fall at Fukushima Daiichi to identify some of the challenges facing the site that may be leading to worker injuries and fatalities.

A Cause Map, or visual form of root cause analysis, is begun by determining the organizational impacts as a result of an incident. In this case the worker fall impacted the safety goal due to the death of the worker. The environmental goal was not impacted. (Although the radiation levels at the site still require extensive personal protective equipment, the incident was not radiation-related.) Workers on site have noted difficult working conditions, which are thought to be at least partially responsible for the rise in incidents, as are the huge number of workers at the site (itself an impact to the labor/time goal). Lastly, local organizations have raised regulatory concerns due to the high number of incidents at the site.

An analysis of the issues begins with one impacted goal. In this case, the worker death resulted from a fall into a ten-meter empty tank. The worker was apparently not found immediately (though specific timeline details and whether or not that impacted the worker’s outcome have not been released) because it appears he was working alone, likely due to the massive manpower needs at the site. Additionally, the face masks worn by all workers (due to the high radiation levels still present) limit visibility.

The worker was checking for leaks at the top of the tank, which is being used to store water used to cool the reactors at the site. There is a general concern about lack of knowledge of workers (many of whom have been hired recently with little or no experience doing the types of tasks they are now performing), though again, it’s unclear whether this was applicable in this case. Of more concern is the ineffective safety equipment – apparently the worker did not securely fasten his safety harness.

The reasons for this, and the worker falling in the first place, are likely due to worker fatigue or lack of concentration. Workers at the site face difficult conditions doing difficult work all day (or night) long, and have to travel far afterwards, as the surrounding area is still evacuated. Reports of mental health issues and fatigue in these workers has led to the opening of a new site providing meals and rest for these workers.

These factors are likely contributing to the increase in accidents, as is the number of workers at the site, which doubled from December 2013 to December 2014. Local organizations are still calling for action to reduce these actions. “It’s not just the number of accidents that has been on the rise. It’s the serious cases, including deaths and serious injuries that have risen, so we asked Tokyo Electric to improve the situation,” says Katsuyoshi Ito, a local labor standards inspector.

In addition to improving working conditions, the site is implementing improved worker training – and looking at discharging wastewater instead of storing it, which would reduce the pieces of equipment required to be monitored and maintained. Improvements must be made, because decades of work remains before work at the site will be completed.

Click here to sign up for our FREE webinar “Root Cause Analysis Case Study: Fukushima Daiichi” at 2:00 pm EDT on March 12 to learn more about how the earthquake and tsunami on March 11, 2011 impacted the plant.

Root Cause Analysis - Incident Investigation

Prison Bus Collides With Freight Train

By Kim Smiley

On the morning of January 14, 2015, a prison bus went off an overpass and collided with a moving freight train.  Ten were killed and five more injured.  Investigators believe the accident was weather-related.

This tragic accident can be analyzed by building a Cause Map, a visual root cause analysis.  A Cause Map visually lays out the cause-and-effect relationships to show all the causes (not just a single root cause) that contributed to an accident.  The first step in the Cause Mapping method is to determine how the incident impacted the overall organizational goals.  Typically, more than one goal needs to be considered.  Clearly the safety goal was impacted because of the deaths and injuries.  The property goal is impacted because of the damage to both the bus and train (two train cars carrying UPS packages were damaged).  The schedule goal is impacted because of the delays in the train schedule and the impact on vehicle traffic.

The Cause Map itself is built by starting at one of the impacted goals and asking “why” questions. So why were there fatalities and injuries?  This occurred because there were 15 people on a bus and the bus collided with a train.  The bus was traveling between two prison facilities and drove over an overpass.  While on the overpass, the bus hit a patch of ice and slid off the road, falling onto a moving freight train that was passing under the roadway.  No one onboard the train was injured and the train did not derail, but it was significantly damaged.  The bus was severely damaged.

The prisoners onboard the bus were not wearing seat belts, as is typical on many buses.  They were also handcuffed together, although it’s difficult to say how much this contributed to the injuries and fatalities.

Useful solutions to prevent these types of accidents can be tricky.  The prison system may want to review how they evaluate road conditions prior to transporting prisoners.  This accident occurred early in the morning and waiting until later in the day when temperatures had increased may have reduced the risk of a bus accident.  Transportation officials may also want to look at how roads, especially overpasses, are treated in freezing weather to see if additional efforts are warranted.

To view a high level Cause Map of this accident, click on “Download PDF” above.

You can also read our previous blogs to learn more about other train collisions:

Freight Trains Collide Head-on in Arkansas

Freight Train Carrying Crude Oil Explodes After Colliding with Another

“Ghost Train” Causes Head-on Collision in Chicago

Deadly Train Collision in Poland

Root Cause Analysis - Incident Investigation

Bad Weather Believed to Have Brought Down AirAsia Flight QZ8501

By ThinkReliability Staff

AirAsia flight QZ8501, and the 162 people on-board, was lost on December 28, 2014 while flying through high-altitude thunderstorms. Because of a delay in finding the plane and continuing bad weather in the area, the black box, which contains data that will give investigators more detail on why the plane went down, has not yet been recovered. Even without the black box’s data, experts believe that the terrible weather in the area was a likely cause of the crash.

“From our data it looks like the last location of the plane had very bad weather and it was the biggest factor in behind the crash. These icy conditions can stall the engines of the plane and freeze and damage the plane’s machinery,” says Edvin Aldrian, the head of Research at an Indonesian weather agency. Beyond the icing of engines, there are other theories on how weather-related issue may have brought down the plane.

Early speculation was that the plane was struck by lighting; while it may have been struck by lightning, experts say it’s unlikely it would have brought the plane down, because modern planes are fairly well-equipped to deal with direct lightning strikes. High levels of turbulence can also result in stalling due to a loss of airflow over the wings. There are also some who believe the plane (an Airbus A320) may have been pushed into a vertical climb past the limit for safe operation (to escape the weather) which resulted in a stall.

While the actual mechanism of how the weather (or an unrelated issue) brought the plane down is still to be determined, aviation safety organizations are already implementing some interventions to increase the safety of air travel in the area based on some specific areas of concern. (These areas of concern can be viewed visually in a Cause Map, or visual root cause analysis, by clicking on “Download PDF” above.)

AirAsia pilots relied on “self-briefings” regarding the weather. Pilots in other locations have expressed concern about the adequacy of weather information pilots obtain using this method. Direct pilot briefings with dispatchers based on detailed weather reporting are recommended to ensure that pilots have the information they need to safely traverse areas of poor weather (or stay out of them altogether).

Heavy air traffic in the area delayed approval to climb out of storm. At 6:12 local time the flight crew requested to climb to higher altitude to attempt to escape the storm. Air traffic control did not attempt to respond to the plane until 6:17, at which point it could no longer be contacted. Air traffic in the area was heavy, possibly because:

The plane did not have permission to fly the route it was on. AirAsia was licensed to fly the route it was taking at the time of the crash four days a week, but not the day of the crash. The takeoff airport used incorrect information in allowing the plane to take off in the first place (and the airline certainly used incorrect information in trying to fly the route as well). The selection of the route has been determined not to be a factor in the crash, but it certainly may have resulted in the overcrowding that led to the delayed response from air traffic control. It also resulted in the airline’s flights on that route being suspended.

It took almost three days to find the plane. The delay is renewing calls for universal tracking of aircraft or real-time streaming of flight data that were initially raised after the loss of Malaysia Airline flight MH370, which is still missing ten months after losing radar contact. (See our previous blog on the difficulties finding it.) Not only would this reduce the suffering of families while waiting to hear their loved ones’ fates, it would reduce resources required to find lost aircraft and, in cases where survival is possible, increase the chance of survival of those on the plane.

 

Root Cause Analysis - Incident Investigation

Hundreds Saved by Arduous Helicopter Rescue From Ferry Fire

By Kim Smiley

In a grueling rescue effort, 427 people were saved from a passenger ferry, Norman Atlantic, which caught fire December 28, 2014 off the coast of Greece.  About 150 people managed to escape the fire in lifeboats, but the remaining passengers were lifted to safety via helicopter.  Gale force winds, heavy rain and darkness all combined to make a difficult rescue operation even more daunting. Ten people died as a result of the accident with few details known about what caused the fatalities.

A Cause Map, a visual root cause analysis, can be built to analyze this incident.  The investigation is just beginning and there are still many unknowns, but an initial Cause Map can be begun that can easily be expanded to incorporate new information as it becomes available.  Even the exact number of people onboard has been difficult to determine because there were several stowaways discovered during the rescue operations that weren’t listed on the ship’s manifest.

What is known is that the fire began early in the morning of December 28th and 427 people were rescued off the ferry. Early reports are that the fire started on the parking deck where there were tanker trucks filled with oil.  Witness accounts indicate that the fire spread fairly quickly, leading to speculation that the fire doors failed.  As the fire progressed, the ship lost power.  Once power was gone, the lifeboats were useless because they require electricity to be lowered.  The heat from the fire drove passengers to the top deck and bridge where they were bombarded by cold, rain and thick smoke for many miserable and likely terrifying hours.  Helicopters pulled passengers to safety one by one, working through the windy night with night vision goggles.

In a stark contrast to the South Korea ferry that capsized off Byungpoong in April, the captain was the last person to leave the Norman Atlantic. The rescue effort was truly impressive.  As Greek Prime Minister Antonis Samaras said, the “massive and unprecedented operation saved the lives of hundreds of passengers following the fire on the ship in the Adriatic Sea under the most difficult circumstances.”

The Italian Transport Ministry has seized the vessel pending an investigation into the fire and thorough inspection of the ship.  Whenever a disaster of this magnitude occurs, it is worth understanding exactly what happened and reviewing what could be done better in the future.  There will be many lessons to learn from this incident, both in how to prevent and fight shipboard fires and how to perform helicopter rescues at sea.

To view a high level Cause Map of this incident, click on “Download PDF” above.