Crane causes signal interference, risks fog landings at Delhi airport
Instrument landing system (ILS) is an important navigation system during extreme weather conditions where visibility even drops to zero.
A crane being used for construction work of an expressway kept aviation officials on their toes for nearly a week after it caused interference in the signals of the instrument landing system (ILS), raising safety concerns among officials.
The issue came up last week when Delhi airport faced more than 100 flight delays and diversions due to bad weather and other related issues.
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 concern to the airport and AAI (Airports Authority of India) officials,” one of the officials close to the matter said.
An ILS helps pilots land during poor visibility and is an important navigation system during extreme weather conditions where visibility even drops to zero.
Experts said the airport officials should have not allowed landings during the situation.
Mohan Ranganathan, an aviation safety consultant said, “ When an ILS faces disturbances, authorities should immediately act on it and downgrade the runway to CAT II (from CAT III).”
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, thus aiming to reduce travel time to reach the airport from two hours to 20 minutes.
“Hence, cranes are being used and are close to runway 11R that is CAT III compliant and hence was being used at the time of dense fog in the Capital last week,” an NHAI official said.
However, the cause of this deviation, when identified to be due to the height of a crane stationed near runway 11R, led the officials from AAI, DIAL (Delhi International Airport Ltd) and NHAI to conduct a meeting and resolve the matter.
“The incident was seen to be a serious safety concern. The crane was removed prioritising the safety of the passengers,” the NHAI official added.
Airport officials said that a group involving the three agencies had been formed.
An airport official in the know of the matter said, “The incident was seen to be a serious safety concern.”
“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,” he added.
A second airport official said, “ The SOPs stated that NHAI should not work near the runway after 8pm. This has been done because typically the fog window is considered to be from 9pm to 10. 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 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.”
An airport official said that the readings have been accurate since the crane has been shifted.
“The SOPs for 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.