Monthly Archives: March 2015

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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

Houston Ship Channel Closed After Ships Collide

By Kim Smiley

On March 9, 2015, two large ships collided in the Houston Ship Channel, one of the busiest waterways in the United States.  There were no major injuries reported, but the accident resulted in the release of methyl tertiary-butyl ether, commonly called MTBE, a chemical that is used as a fuel additive.  The clean-up and investigation of the collision closed the channel from the afternoon of March 9 until the morning of March 12.

At the time of the collision, the tanker Carla Maersk was traveling outbound in the channel transporting MTBE.  The bulk carrier Conti Perido was heading inbound with a load of steel.  Both ships were significantly damaged by the collision and three cargo tanks ruptured on the Carla Maersk, spilling the MTBE. Limited information has been released about what caused the accident, but a National Transportation Safety Board investigation is underway.  Initial reports are that both vessels were traveling at about 9 knots, which is typical for this stretch so excessive speed does not appear to be a cause.  It has also been reported that it was foggy at the time of the accident which may have played a role in the accident.

An initial Cause Map can be built using the information that is available.  The first step in the Cause Mapping process is to fill in an Outline with the basic background information along with the impacts to the goals.  Like many incidents, this collision impacted several different goals.  The safety goal was impacted because MTBE is toxic and has the potential to cause injuries.  The environmental goal was clearly impacted by the release of MTBE.  The multiple-day closure of the Houston Ship Channel is an impact to the production/schedule goal and the impact to local businesses resulting from closure is an impact to the economic goal.  The damage to the ships is an impact to the equipment goal.

On the outline, there is also a line to record the frequency of how often a similar event has occurred.  It’s important to consider the frequency because a small problem that occurs often may very well warrant a more detailed investigation than a small problem that has only been seen once.  In this example, there have been previous ship collisions.  This accident was the second ship collision to occur in the channel in a week.  Two large ships bumped on March 5, 2015, which did not result in any injuries or pollution.

Release of MTBE is a significant concern, but the impacts of this ship collision could easily have been worse.  MTBE is volatile and flammable so there could have been a fire or the ships could have been carrying something more dangerous.  It may be difficult to get the data, but it would be interesting to know how many near misses have occurred between ships traveling in the channel. The frequency that accidents are occurring needs to be considered along with the details of any individual incident when conducting an investigation. Two collisions in a week is a pretty clear indication that there is potential for more to occur in the future if nothing is changed.

Root Cause Analysis - Incident Investigation

Plane Narrowly Avoids Rolling into Bay

By ThinkReliability Staff

Passengers landing at LaGuardia airport in New York amidst a heavy snowfall on March 5, 2015, were stunned (and 23 suffered minor injuries) when their plane overran the runway and approached Flushing Bay.  The National Transportation Safety Board (NTSB) is currently investigating the accident to determine not only what went wrong in this particular case, but what standards can be implemented to reduce the risk of runway overruns in the future.

Says Steven Wallace, the former director of the FAA’s accident investigations office (2000-2008), “Runway overruns are the accident that never goes away.  There has been a huge emphasis on runway safety and different improvements, but landing too long and too fast can result in an overrun.”  Runway overruns are the most frequent type of accident (there are about 30 runway overruns due to wet or icy runways across the globe every year), and runway overruns are the primary cause of major damage to airliners.

Currently, the NTSB is collecting data (evidence) to aid in its investigation of the accident.  The plane is being physically examined, and the crew is being interviewed.  The data recorders on the flight are being downloaded and analyzed.  While little information is able to be verified or ruled out at this point, there is still value in organizing the questions related to the investigation in a logical way.

We can do this using the Cause Mapping method of root cause analysis, which organizes cause-and-effect relationships related to an incident.  We begin by capturing the impact to an organization’s goals.  In this case, 23 minor passenger injuries were reported, an impact to the safety goal.  There was a fuel leak of unknown quantity, which impacts the environmental goal.  Customer service was impacted due to a scary landing and evacuation from the aircraft via slides.  Air traffic at LaGuardia was shut down for 3 hours, impacting the production goal.  Both the airplane and the airport perimeter fence suffered major damage, which impacts the property/equipment goal.  The labor goal was also impacted due to the response and ongoing investigation.

By beginning with an impacted goal and asking “why” questions, we can begin to diagram the potential causes that may have resulted in an incident.  Potential causes are causes without evidence.  If evidence is obtained that supports a cause, it becomes a cause and it is no longer followed by a question mark.  If evidence rules out a cause, it can be crossed out but left on the Cause Map.  This reduces uncertainty as to whether a potential cause has been considered and ruled out, or not considered at all.

In this case, the NTSB will be looking into runway conditions, landing procedures, and the condition of the plane.   According to the airport, the runway was cleared within a few minutes of the plane landing, although the crew has said it appeared all white during landing.  The National Weather Service reported 7″ of snow in the New York area on the day of the overrun.  Procedures for closing runways or aborting landings are also being considered.  Just prior to the landing, other pilots who had recently landed reported braking conditions as good.

The crew has also reported that although the auto brakes were set to max, they did not feel any deceleration. The entire braking system will be investigated to determine if equipment failure was involved in the accident.  (Previous overruns have been due to brake system failures or the failure of reverse thrust from one of the engines, causing the plane to veer.)  The pilot also reported the automatic spoiler did not deploy, but they were deployed manually.

Also being investigated are the landing speed and position, though there is no evidence to suggest that there was any issue with crew performance.  As more information is released, it can be added to the investigation.  When the cause-and-effect relationships are better determined, the NTSB can begin looking at recommendations to reduce future runway overruns.

Root Cause Analysis - Incident Investigation

Train Derails in West Virginia

By Kim Smiley

On February 16, 2015, a train hauling 109 tank cars of crude oil derailed in Mount Carbon, West Virginia.  It has been reported that 27 tank cars in the train derailed.  Some of the tank cars were damaged and released an unknown amount of crude oil, resulting in a large fire.  Hundreds of families in the surrounding area were evacuated, but only one injury was reported.

The accident investigation is still ongoing, but what information is known can be used to build an initial Cause Map, a visual format for performing a root cause analysis.  The Cause Map can be easily expanded as needed to document additional information as it becomes available.

The first step in the Cause Mapping process is to fill in an Outline with the basic background information for the issue as well as how the overall goals were impacted. In this example, there were many impacted goals.  The safety goal is impacted because there was an injury, the property goal is impacted because of the damage to the train, the environmental goal is impacted because of the release of oil, etc.  Once the Outline is complete, the Cause Map itself is built by starting with an impact to a goal, asking “why” questions, and laying out all the causes that contributed to an issue.

The significant aftermath of this derailment is known, but little has been released about what specifically caused the train to derail.  It was snowing heavily at the time of the accident, which may have played a role, but since more evidence is needed, a “?” is included on the Cause Map.  Data from the digital data recorder has shown that the train was not speeding at the time of the accident, which has been a factor in previous derailments.  Another fact worth noting is that the damaged train cars were a newer design that incorporated modern safety upgrades.

With so many unknowns, the Federal Railroad Administration is conducting a full-scale investigation to determine exactly what happened.  The damaged tank cars, track, and other components along with relevant maintenance and inspection records will be all be analyzed to better understand this derailment.

Unfortunately, crude oil train accidents are predicted to become increasingly common as the volume of flammable liquids being transported by rail continues to rise.  According to the Association of American Railroad, 40 times more oil was transported by rail in 2012 than in 2008. Hopefully, the lessons learned from this derailment can be used to help reduce the risk of future rail accidents.

To view the Outline and initial Cause Map for this accident, click on “Download PDF” above.