The implications of wind and shear incidences on flight operations at JKIA in Kenya.

Abstract

Bad weather is the leading cause of flight delays. This is because it highly affects flight safety especially for aircrafts in approach-landing and take-off-climb out phases owing to their proximity to the ground. Delays affect the economy negatively due to the additional cost attached to them. This study thus analyzed the implications that wind shifts had on operations at JKIA and surrounding areas between 2007 and 2016. Runways are constructed to take advantage of the prevailing wind. However, the erratic nature of wind causes abrupt changes in wind velocities decreasing the optimal performance of an aircraft. The study examined the effects of wind shear on flight operations. A total of 319 wind shear incidences were reported by pilots. 90% were airborne of which 65% resulted in go arounds due to unstable approach caused by wind shear and turbulence. 2% diverted to other airports. The economic impact due to delays and diversions amounted to approximate USD 79,620 and USD 700,000 respectively. Tailwind shear was the common shear encountered. This is supported by 11% of pilots who specified the nature of shear. Both the allowable tailwind components of 10-15knots and the allowable crosswind components of 10.5-20 knots were encountered. A strong positive correlation was observed between wind shear presence and delays. In entirety, 1 in every 2983 flights encountered wind shear. Wind shear was reported for the entire year. Over the years wind shears had a downward trend while air traffic had an upward trend. The temporal variability was significant for air traffic as compared to wind shears. The seasonal transition months of February, August and November had high wind shear reports with exception of May. This was based on position of the ITCZ in the tropics. The wind characteristics displayed by seasonal wind roses showed a variability of wind direction in JJA. This can be explained by the influence of southern pressure cells during this season. In the rest of the months north east monsoon winds were dominant. From predictability analysis it was evident that nocturnal inversion caused wind shearing in the layer 800-750mb in the February case study. Wind speeds were at their maximum at the 800mb level. The wind shear was mainly light to moderate. In the August case study, directional shear was evident from 800mb to middle levels whose cause was convection. It persisted throughout the day. The different directions between the surface and middle levels enhanced instability.