Introduction
Over the past century, aviation has become a critical industry all across the world. Due to globalization, people and goods need to travel at a faster pace through longer distances. As air transportation increases in volume, implementing safety measures in aviation is a major concern for government agencies all over the world. The amount of general aviation accidents per year has been steadily declining over the years.
The National Transport Safety Board (NTSB) however notes that the relative portion of general aviation accidents due to weather-related issues has remained steady, ranging from between 6% to 9% of annual general aviation accidents (National Transport Safety Board [NTSB], 2014). Historically, about 66% of all weather-related aviation accidents are fatal, a rate that is three times higher than the overall fatality rate of general aviation accidents (Kulesa, 2002).
In 2014, there were 1213 general aviation accidents in the US, with 253 being fatal involving 405 deaths (General Aviation Manufacturers Association, 2015). According to the NTSB, over 25% of all these fatalities occurred during instrument meteorological conditions (IMC). Since the weather is a frequent cause for general aviation accidents, it is important to understand the mechanism with which it poses a threat to aviation and develop possible solutions to counter these threats. This paper looks at the accident involving Continental Airlines Flight 1404 and looks at how the weather played a part in the events surrounding the accident. The paper will also develop several recommendations based on the analysis of the case.
Background
Continental Airlines Flight 1404, departed from Denver International Airways on 20 December 2008. The plane utilized the left side of runway 34R but a post-crash fire ensued during take-off. According to the NTSB accident report, the initial preflight procedure proceeded as usual. After the pilots completed all the preflight checks, they taxied towards the runway without problems. The local traffic controller informed the pilots that the wind strength was 27 knots from 270°(NTSB, 2010).
The pilots received clearance to take off from runway 34R at a departure heading of 20°. After acknowledging the clearance, the first officer advised the captain on the power settings based on the data offered about wind conditions. At the time of acceleration, both the captain and the first mate observed that clouds were rolling in at a fast place and that the wind was picking up. During acceleration, when the plane had reached a speed of about 90 knots, the airplane began shifting towards the left of the runway. Investigations by the NTSB revealed that the airplane veered left 2600 feet away from the approach end of runway 34R (NTSB, 2010).
It then crossed an adjacent service road and taxiway before stopping near the airport’s fire station, at a heading of about 315°. The airplane had become airborne as it was crossing the uneven terrain causing a heavy impact as it touches the ground just before crashing to a stop. According to the pilot, the airplane acceleration was smooth until about reaching 90 knots after which he felt the wheels losing traction after the rear end of the plane slipped out hard to the right. He attributed the movement to high wind conditions or a slick patch of the runway. The airplane experienced significant damage but there were no fatalities. There were 6 serious injuries and 41 minor injuries. The airplane had a total of 110 passengers and 5 crewmembers (NTSB, 2010).
The pilot had accumulated 13 100 hours of flight experienced, with 6300 being in Boeing 737. Investigations carried out by the NTSB revealed that the captain was suitably competent and had no prior performance issues. The plane, manufactured in 1994 by Boeing, had accumulated 40,541 total flight hours. The plane had been inspected before the trip and all maintenance works carried out had been by FAA form 337 guidelines (NTSB, 2010). Considering both the pilot and the airplane was in prime condition during the flight, the NTSB determined that meteorological conditions played the largest role in this accident.
The NTSB used available information from the Flight Data Recorder (FDR), National Weather Service, and DEN wind sensors to estimate wind conditions at the time of the crash. At the time of the crash, the NTSB estimate revealed that the wind was from the west with a strength that varied between 35 and 40 knots. For that reason, runway 34R experienced a direct crosswind with a crosswind component that varied between 29 and 45 Knots.
At the time of the first skid marks, when the right rudder pedal initially shifted, the wind was at peak strength of 45 knots (NTSB, 2010). During takeoff, the DEN ATCT local controller had informed the pilots that wind strength was at 27 knots from 270°. However, 2 minutes before flight clearance, sensors at the runway departure point recorded winds at 29 to 39 knots from the west. At the time of clearance, airport winds (AW) displayed on the Ribbon Display Terminal would have shown 35 knots winds from the west. DEN official policy requires pilots to change runways when they encounter winds greater than 30 Knots. Since the pilot was acting on a lower figure, he undertook flight procedures that correlated to winds of 27 knots.
Analysis
The NTSB recognizes several weather-related issues that may affect aviation safety. These issues include wind, convective weather e.g. thunderstorms, in-flight icing, turbulence, ceiling and visibility, and ground de-icing. About this case, the wind was responsible as the plane did not gain sufficient altitude and the runway was dry.
The NTSB cites wind as the main contributing factor of weather-related accidents. During the years preceding this accident (2003-2007), wind conditions accounted for 1,149 accidents, more than half of all weather-related accidents (Federal Aviation Authority, 2008).
Drastic changes in wind direction and strength (wind shear) affect planes mostly during takeoff and landing. Wind shear makes it hard to control the airplane and maintain direction during takeoff and landing. The FAA has developed alert systems to recognize wind shear conditions around the airport. The DEN was equipped with the most advanced wind shear alert system at the time of the crash. Two minutes before the crash, the LLWAS sensors recorded wind speeds of 40 knots on the runway. This data was however not relayed to the pilots promptly and the pilots could not make the necessary adjustments.
Due to the position of the Denver International Airport (DEN), mountain wave conditions play a big role in preflight and flight decision making. According to the FAA, mountain wave conditions usually occur in high terrain where wind speeds increase as the terrain rises, with top wind speeds reaching 20 knots at the peak elevations (Federal Aviation Authority, 2008). The conditions above the mountain are usually stable, and wind directions flowing across the mountain ridge have little variation.
Due to the nature of airflow over the mountain, a harmonic oscillation occurs resulting in an atmospheric wave. This wave, composed of uplifts and down lifts, has a wide reach and can at times lead in turbulence. The FAA warns that mountain wave conditions pose problems during landing and take-offs such as the loss of directional control (NTSB, 2014).
NTSB notes that the captain could have taken control of the plane if he had applied the appropriate Right Rudder Pedal input as the plane was turning to the left (NTSB, 2010). While the gusty winds made it hard to maintain directional control, the pilot could undertake corrective measures within an appropriate timeline to prevent the plane from leaving the runway.
The crash of Continental Flight 1404 occurred due to a combination of factors. First, the wind information provided at the time of takeoff clearance differed from that experienced during takeoff acceleration. Secondly, the captain did not receive the most adverse wind information, and as such could not delay takeoff. Third, Denver Airport had not instituted crosswind components in the runway selection process. Fourth, the airport’s simulation training did not take into account gusting crosswinds and ground-level disturbances. The pilot was thus unequipped to handle the conditions at the time of the crash.
Recommendations
This paper has looked at the conditions surrounding the crash of Continental Airlines Flight 1404 on 20 December 2008. From the causes identified and the research on the subject, the paper recommends the following.
- Improve the training of air traffic controllers to ensure they can read and analyze various types of weather-related data.
- Development of technology that will allow pilots to access critical weather information such as mountain wave activity as they change.
- The NTSB should research ways to enhance the communication of hazardous weather information across the country. According to the NTSB, a method that allows wind conditions to be measured remotely using laser technology is under development.
- Airports should work together to analyze flight data to better understand the impact of winds on runway excursion and to develop strategies that mitigate all related wind-related problems.
- The NTSB in conjunction with airline operators should collect meteorological data at airports across the country and use this data to develop a more realistic simulation system that incorporates real-time gusty crosswind profiles.
Conclusion
“The wind blows where it wills, and you hear the sound of it, but you do not know whence it comes or whither it goes” (John 3:8 New International Version).
Over thousands of years, man has been able to fashion devices that make life easier. However, nature has always posed a challenge for man’s bid to conquer all that surrounds him. During the past century, air travel has become a very important part of life as well as a means for economic growth. According to NTSB, weather-related issues are responsible for more fatal general aviation accidents that all the other potential causes.
In the US, weather-related accidents result in over 25% of all fatalities in general aviation accidents. To mitigate these fatalities, it is important to institute mechanisms that allow better retrieval of weather information and the expedient dissemination of this information. Continental Airlines Flight 1404 suffered an accident during takeoff procedures. The investigation that followed indicated that weather conditions played a major role in causing this accident. The investigations also indicated that the pilot was not well accustomed to maneuvering through extreme weather. It is therefore important for the aviation industry to develop better weather monitoring and communication system as well as create better simulation exercises for pilots.
References
Federal Aviation Authority (2008). Weather-related Aviation Accident Study. Web.
General Aviation Manufacturers Association (2015). 2014 General Aviation Statistical Databook & 2015 Industry Outlook. Web.
Kulesa, G. (2002). Weather and Aviation: How Does Weather Affect the Safety and Operations of Airports and Aviation, and How Does FAA Work to Manage Weather-related Effects? Web.
National Transportation Safety Board (2010). Runway Side Excursion During Attempted Takeoff in Strong and Gusty Crosswind Conditions Continental Airlines Flight 1404 Boeing 737‐500, N18611 Denver, Colorado December 20, 2008. (NTSB/AAR-10/04 Report No. PB2010-910404). Washington D.C.: National Transport Safety Board.
National Transportation Safety Board (2014). NTSB Most Wanted List. Web.
National Transportation Safety Board (2016). Aviation Accident Reports. Web.