'Combat plan' for dense fog Hours at Delhi Airport

In recent years, increase in fog hours is noticed and there has been an increase in dense fog hours by 10 times over Delhi Airport, having visibility of less than 200m during the months of December and January. Fog is majorly prevalent in the north and north-west part of India due to the stable local atmospheric conditions which keeps the vehicular and industrial pollutants trapped in the lower atmosphere closer to the surface. The rapid increase in vehicular traffic and industrialization over the years is one of the major reasons for this increased concentration of the pollutants to the surface. Associated with the dropping of the ambient air temperature in the night and early morning time, the increased concentration of suspended pollutant particles facilitates the condensation of moisture that leads to the formation of fog.

Flight services to-and-from the national capital's Indira Gandhi International (IGI) Airport gets interrupted due to medium - heavy foggy conditions, which is expected to commence from the third week of this December. Foggy conditions to set in from the third week of December till mid-February around the Delhi IGI airport. It is estimated that the foggy conditions might last for 100-135 hours, this season.

A total of 286 flight diversions were caused due to fog in last three winters from Delhi IGI airport.
• In 2011, it was 54
• In 2012 it was 89
• In 2013 it was 143

In April, a panel of the aviation regulator (Directorate General of Civil Aviation) recommended several steps to achieve zero diversions from the Delhi airport:

• Airports near Delhi should be upgraded to category-III B level of instrument landing system (used by Delhi IGI airport), which provides visual and sensory guidance to land aircraft in range of 150-50 metres.

• An aircraft can land at the Delhi Airport with a visual range of around 50 metres by using the CAT-III B ILS system, however, it can only take-off between visibility range of 125-150 metres.

• Airlines are also advised not to operate propeller or other aircraft like ATRs or Q400s which are not equipped with CAT-III B ILS on-board. Special training to pilots and aircraft crew is also required under guidelines to operate to Delhi during the fog-period.

• Airlines and airport operators too have been advised by the DGCA to provide up-to-date flight information to passengers. Passenger carriers are also required to provide refreshment and resting facilities for passenger affected by fog delays under DGCA's guidelines.

• There are also 11 stand-by airports like Jaipur, Lucknow and Amritsar, which are prepared to handle diverted flights from Delhi during the season.

This year though the Delhi International Airport Limited (DIAL), seems confident of a smooth operations season during foggy conditions. All the mechanisms and infrastructure are in place to handle any situation during the fog condition.

In addition, DGCA might use runway 27 for take-offs for the first time this foggy season. This will provide them with great efficiency in de-clogging the airport during foggy conditions.