If you have ever felt that landing at Chennai airport is a jerkier experience than at any other airport, you are not without reason. Wind shear, which was initially suspected to be one of the reasons for an Emirates Airlines taking a plunge of more than 1,000 feet above Goa on Sunday morning, is the prime culprit here.
Chennai is prone to low level wind shear — a sudden shift in speed or direction of wind — especially during the summer months. Though considered an aviation hazard, the airport met department is struggling to make an efficient forecast of wind shear as pilots seldom report the experience, denying adequate data. "Indian pilots rarely report the experience since they think it is a usual phenomenon, while expat pilots do inform us sometimes," said an airport official.
Wind shear at heights of 3,300 feet or less is considered to be dangerous for aircraft because it will lose its altitude unexpectedly, causing it to overshoot the runway. Pilots will be able to correct the altitude even after hitting a wind shear if they are flying sufficiently high. But, if the aircraft is flying at less than 1,000 feet, a wind shear can even cause a crash.
Hence, reporting a wind shear is considered mandatory so that airport met department will have enough data to warn flights.
According to statistics, only 221 instances of wind shear have been reported by cockpit crew between 1987 and 2007 at Chennai airport. "We should be getting at least 500 reports a day. Airline crew are often reminded at meetings to report the occurrence, but only a few cases are reported," said R Suresh, director airport meteorological office (AMO).
World over wind shear lasts only for a short spell of two to five minutes. But in Chennai, it may even stretch to 10 hours as it was noticed in 2006. Hills around the city, the sea breeze and the Westerlies at both ends of the main runway are cited as reasons.
The met department currently depends on Doppler radar to gauge winds but reports by pilots are important to validate the findings.
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