The Airports Authority of India (AAI) has installed a state-of-the-art Precision Approach Lighting System (PALS) on the runway of the Thiruvananthapuram International Airport, a measure which improves safety during aircraft landings.
Trials are in progress on the ₹5.83-crore Category-1 PALS on Runway 32 and it will be commissioned once the Directorate General of Civil Aviation (DGCA) gives the nod, airport director C.V. Ravindran said.
Simply put, an approach lighting system consists of a series of strategically placed lights extending outward from the approach end of a runway. It serves as a guide to pilots of incoming aircraft and plays a crucial role, especially during bad weather, in guaranteeing safe landings.
The advantage of the new PALS is that it allows pilots to safely land even if the visibility is down to 550 metres (it is 800 metres now). This reduces the chances of approaching aircraft having to be diverted due to poor visibility when the weather is bad.
Atop bridges
Another factor makes the ALS on Runway 32 special from an engineering point of view; a sizeable portion of the ALS — 360 metres out of the total 900 metres — is outside the actual operational area of the airport and installed atop bridges and the cantilevers over the Parvathi Puthanar canal.
Under the DGCA requirements, a full-length ALS is mandatory up to a distance of 900 metres for Category-1 runways. “In 2012, the DGCA had pointed out the requirement when renewing the aerodrome licence,” Mr. Ravindran said. The licence was granted on the condition that the requirement would be met.
Land scarcity
However, the runway was equipped with a distance-coded CAT-1 PALS up to a distance of only 540 metres due to scarcity of land and the proximity of public road and the Parvathy Puthanar canal.
“These factors meant that a conventional CAT-1 ALS was out of the question. The height of the Ponnara bridge and the need to install the light poles across the canal posed stiff challenges,” Roji R. Assistant general Manager (Engg-Electrical), AAI Thiruvananthapuram Airport, said.
To overcome the hurdle, the airport resorted to the barrette-type ALS. This system has a full length of 900 metres consisting of 30 bars of lights installed at 30-metre intervals and requires less land. Each bar has four fixed lights and one flashing light unit. “By providing sequenced flashing approach lights instead of wing-bars used in the conventional systems, we have reduced the land requirement,” Mr. Roji said.
Lights located above the canal have been installed atop cross-over bridges and cantilevers made of galvanized structural steel. There are two such bridges and three cantilevers on the canal.
