To reduce delay, Met to give runway specific fog forecast for Delhi airportUpdated: Dec 25, 2017 09:50 IST
Till now, the Met department used to issue airport-wise warning and many a time, runway 28/10 had enough visibility for landing and take-off but runway 29/11 was not available due to fog.(Virendra Singh Gosain/HT PHOTO)
Vast open spaces along with the longest runway of the country are affecting Delhi airport’s capacity to handle flights during dense fog.
An analysis of fog duration at two runways of Delhi’s Indira Gandhi International Airport (IGIA) has shown that runway 29/11, the longest in the country, faces almost two times hours of fog in comparison with runway 28/10.
To counter this, the Met department, for the first time, will issue runway-wise fog forecast, allowing airlines and airport operator to be better prepared for low-visibility operations.
Till now, Met department used to issue airport-wise warning and many a time, runway 28/10 had enough visibility for landing and take-off but runway 29/11 was not available due to fog.
“In such case, flights either hover around or are diverted to nearby airports. To avoid this, runway-wise forecast will be issued so that airlines can prepare themselves better before leaving for Delhi. Because there is less urbanisation around runway 29/11, it witnesses more hours of fog.
“In such a situation, only one runway is available for operation, reducing the airport’s capacity from 75 movements per hour to 35,” said a Delhi airport official, who did not wish to be named.
This time the Delhi airport has a radiometer-based fog monitoring system, which will help them to give runway visibility at every 10 second and then give region-wise forecasts.
A met official said the Delhi airport continued to be the worst fog-affected airport in the world in winter from December to February due to high air and passenger traffic. For the airport operator, a solution for this is timely stakeholder coordination and a collaborative decision making.
“An enhanced version for collaborative decision making (CDM) during fog has been put in place with the active involvement of all the stakeholders, including airlines and airport operator, DIAL. These measures improve predictability of flight operations and hence facilitate the travelling passengers during fog,” said an air traffic controller.
On an average, the Delhi airport witnesses 150 hours of dense fog in a season and the daytime fog affects flight operations heavily. Almost 300 flights get delayed or cancelled. Last year, during the first spell of fog, over 900 flights were affected and many had to land at nearby airports as visibility was bad at the Delhi airport.
According to an official of aviation regulator, Directorate General of Civil Aviation, this time airlines are better prepared this time and specific prediction will help in smooth operation.
The airport’s visibility woes
The Met dept will start issuing runway-wise fog forecast allowing airlines and airport operator to be better prepared for low visibility ops. Especially as Delhi’s Runway 29/11 sees heavier fog than the other two runways.
Runway Visibility Range (RVR) is categorised into CATI, CATII, CATIIIA, CATIIIB and CATIIIC
It has nothing to do with general visibility, under the CAT conditions, flight operates under the guidance of instrument landing system
Between 550m and 800m, flight operates under CATI
Between 300m and 550 m, flight operates under CATII
Between 175m and 300 m, flight operates under CATIIIA
Between 50m and 175m, flight operates under CATIIIB
Below 50m, CATIIIC conditions come in place, but at Delhi airport operations are shut in CATIIIC conditions
For landing the runway visibility has to be 75m and for take-off the RWR has to be 125m
Delhi airport has three runways: 29-11, 28-10 and 27-09 (this is not capable of CATIIIB ops)
Year-wise details of dense fog at different runways
Fog hours (RVR below 350)
Year Runway 29 Runway 28
2008-09 103 69
2009-10 125 108.3
2010-11 98 40
2011-12 75 43
2012-13 94 49
2013-14 118 86
2014-15 138 82
2015-16 45 22
2016-17 94 50
First Published: Dec 25, 2017 08:08 IST