Rain snag rein on flights

Calcutta: Flight operations came to a halt at Calcutta airport for around 20 minutes on Thursday afternoon, as a key component of the Category II Instrumental Landing System (Cat II-ILS) and three radar went out of order following a thunderstorm.
Five flights had to hover over the airport and three others were stranded on the parking bay, unable to land or take off because of poor visibility.
The airport has two instrumental landing systems to guide aircraft to take off or touch down — Cat I and Cat II. For Cat I, the minimum visibility should be 550 metres, while the more advanced Cat II can function even when the visibility drops to as low as 350 metres.
On Thursday, the visibility at the airport started falling as soon as the thunderstorm struck at 12.42pm.
Soon after, the fuse of mid-runway visual range, a key component of the Cat II-ILS, blew off due to a short-circuit and three radar, scanning aircraft movement in the south, west and east, became defunct.
At 12.50pm, the visibility dipped to below 500 metres, making it impossible for flights to land or take off as the CAT-II system was not working. Visibility shot up to 1,500 metres after around 20 minutes, but the flight operations had been disrupted by then.
Five flights scheduled to land at Calcutta had to be kept on hold.
14/09/07 The Telegraph

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Categories: Airports Sep 2007, Safety Sep 2007