‘Causing signal interference’: Crane risks fog landings at Delhi airport

The National Highway Authority of India (NHAI) is constructing the Urban Extension Road– II (UER 2) which will connect North Delhi to the Delhi-Jaipur highway

New Delhi: A crane that was being used for construction work on an expressway at the Delhi airport became a nuisance for aviation officials for nearly a week after it caused interference in signals of the instrument landing system (ILS), raising safety concerns among officials.

ILS helps pilots to land amid poor to no visibility during extreme weather conditions (Representative Photo)

ILS helps pilots to land amid poor to no visibility during extreme weather conditions.

The National Highway Authority of India (NHAI) is constructing the Urban Extension Road– II (UER 2) that will connect North Delhi to the Delhi-Jaipur highway, and cranes are being used and are close to runway 11R, which is CAT III compliant.

CAT III or category III is an ILS that allows aircraft to land in low visibility situations where the visibility is 50m, like during rains, dense fog, and snow.

“The incident was seen to be a serious safety concern. The crane was removed prioritising the safety of the passengers,” an NHAI official said.

The issue came up last week when Delhi airport faced more than 100 flight delays and diversions due to bad weather and fog conditions, following which officials from the Airports Authority of India (AAI), Delhi International Airport Ltd and NHAI held a meeting to resolve the matter.

Officials in the know of the matter confirmed that there were disturbances in the ILS signals due to a crane placed near the 11R side of the runway.

“The interference in the ILS led the aircraft to make a deviated landing. They were observed to land 10-20 ft away from the centreline of the runway, causing safety concerns,” an official aware of the matter said.

“To ensure that such an incident is not repeated, the operations department of the three agencies have come up with a few standard operating procedures (SOPs) to be followed,” said an airport official.

The SOPs state that NHAI should not work near the runway after 8pm. The NHAI officials have also been asked to re-commence the work in the morning only after the shift in charge (an AAI official) gives clearance for the same after studying the weather conditions.

“The SOPs for the operation of ILS 29L during fog season are circulated to all concerned officials via emails and have been asked to implement them,” an AAI official said.

The NHAI official, however, said, “NHAI and AAI work through active coordination. The AAI informs us to lower the cranes whenever there is a visibility issue. It is only when we get a green signal from AAI that we resurrect the cranes. NHAI is sensitive about safety matters and AAI also ensures that none of our work is affected.”

Experts said the airport officials should have not allowed landings during the situation.

Mohan Ranganathan, an aviation safety consultant said that when an ILS faces disturbances, authorities should immediately act on it and downgrade the runway to CAT II (from CAT III).