An extract from official documents dealing with the Chennai airport, sourced by Captain A. Ranganathan.
The heart and soul of an airport is the runway. Unfortunately, there appears to be a drift away from safety and more of political bombast. A recent video I received, showing corrosion cracks on the underside of the secondary runway bridge at the Chennai airport and the rhetoric about pushing ahead with an environmental disaster, called the Parandur airport project, is something that should worry people of Chennai. During an inspection in 2012 by me, as a member of the Civil Aviation Safety Advisory Council (CASAC), I had documented several portions of the underside of the bridge showing corrosion and cracks. I had warned that, with time, the poor construction would result in a disaster. The Chennai airport was flooded on October 27, 2005, owing to heavy rain, but the main runway was above water and flight operations were not affected. The terrain sloping down towards the Adyar and no obstacles on the path of the river ensured free flow of water into the sea. Only low-lying areas on either side of the Adyar were affected
Stipulation violated
The Tamil Nadu PWD had informed Airports Authority of India (AAI) that the maximum flood level was 10.5 metres, and with free board of 0.5 metres, it would amount to 11 metres. When AAI applied for environmental clearance for building the runway bridge across the Adyar, it was allowed to build above 12.4 metres. This would mean that the pier cap would be 1.65m above this, the girder of 1m and the runway surface concrete of 1m thickness. This would make the elevation of the runway surface on top of the bridge 15.5m, which will be 50.5 feet. The threshold of the secondary runway, before the bridge was built, was 36 feet.
The Ministry of Environment and Forests had permitted a bridge of 200m by 415m, but AAI built a bridge of 200m x 462.5m in violation of the stipulations. What was worse was the pillars that were to be of 1.2m diameter were only 0.86m. The runway surface elevation on top of the bridge was only 42 feet as per the Type A Obstacle chart issued by AAI in 2010, 4m short and 47m wider than the permitted level. It had also built an embankment wall of 12 feet height. The destruction caused by the 2015 floods was made worse by this. The main runway elevation at the intersection was 46 feet and the bridge was 42 feet and the mid-section was only 33 feet, the area through which the floodwaters rushed, destroying everything on the way. The December 2015 flood level was 13.4m, well above the secondary runway bridge.
The floodwaters were not only from the Chembarambakkam lake (which contributed a mere 30%) but also from all the waterbodies west of Chennai: Mudichur, Sriperumbudur, and Parandur. We survived the 2015 floods, but if the waterbodies at Parandur are filled with concrete, it is unlikely that the bridge will survive severe floods. The fact is that even after 13 years, very few flights operate out of the secondary runway and no wide-body aircraft will use it as it does not have Instrument Landing System (ILS). AAI has been misleading the Tamil Nadu government to get land allotted for building a Approach Light System for the two ends. Without an ILS, the runway will only be a non-precision runway and all that you need is a Simple Approach Light System, and the land AAI is asking for is not needed at all. It must be more for commercial reasons than for operational reasons.
How to increase capacity
The Chennai airport’s runway capacity can be increased by building a parallel runway with a separation of 200m, north of the main runway. AAI could negotiate with the Defence Ministry for the Army and Coast Guard land. The areas occupied by them around the airport will meet the requirement for infrastructure. We have the Metro Rail and the GST Road in place and the Central and State governments should consider this option. Take the London Gatwick Airport as an example. The parallel runway can be used for the aircraft, like A320 and B737 family, to take off and it could also be used for landing from the Pallavaram-end, as is being done at Port Blair, Leh, and Bagdogra.
Of late, there seems to be an effort by AAI to convince the State government to allot land for use of the secondary runway by wide-body aircraft. No wide-body aircraft will use a non-precision runway, especially at night. An ILS Localiser requires clear space behind the antenna array; it has to be located in a vibration-free area. Owing to the Metro Rail and heavy traffic on the GST Road, the vibration levels are too high for an ILS Localiser. The aircraft movement on main runways and taxiways will also cause deflection of Localiser beams and they can never install an ILS for Runway 12. Similarly, the position of Localiser for Runway 30 is not possible owing to the beams getting deflected from the Coast Guard hangar and other structures.
Late touchdown
If one goes through airport charts issued by AAI from the time the secondary runway bridge was constructed, one would see figures ranging from 32 feet to 46 feet as the runway threshold for Runway 12. This is dangerous as the landing distances are based on crossing the threshold at 50 above the runway surface. This could result in a late touchdown and late landing. We should also consider the landing overrun if an aircraft lands late on Runway 12. One should remember that beyond the compound wall is the Metro Rail roof holding 25,000-volt cables and the crowded GST Road traffic. We also have two petrol stations across the road. Is it worth the risk to push for operations from a dangerously unsafe runway? If Chennai has to regain lost traffic, this is the best solution. Demolish the bridge across the river before the next floods. The old secondary runway was working perfectly well for smaller aircraft and one does not need more than 8,000 feet of runway. Build the parallel runway and use it for smaller aircraft and wide-body aircraft from the main runway. The government would save crores of taxpayers’ money — and also lives in the event of a disaster.
(Captain A. (Mohan) Ranganathan is a former airline instructor pilot and aviation safety adviser. He is also a former member of the Civil Aviation Safety Advisory Council, India.)
Published – March 30, 2025 10:50 pm IST