Wednesday, November 28, 2012

Changing angle for that perfect landing

MUMBAI: In a bid to make landing at Mumbai airport more accurate, Mumbai International Airport Pvt Ltd (MIAL) and Airports Authority of India (AAI) are changing the glides path angle. The glide angle at the main runway (27) is 3.3 degrees now. It will be changed to 3 degrees.

On Tuesday, the main runway was unavailable for landing and the other end (09) was in use. Officials said that while work is under way, the glide scope on the main runway (27) will not be available for the coming two months. This means, that if visibility drops, all flights would land on the secondary runway or on the 09 end of the main runway. This may mean a delay of 10-15 minutes.

Airport officials say the glide angle on the main runway was steeper than globally recommended standards. This means aircraft descend at a steep angle and at a higher speed. This is now being changed so that aircraft can land more accurately and at the right speed. Glide path is an equipment that gives vertical guidance to a landing aircraft. The aircraft locks the signal and descent angle from the glide path and starts descending. Its function is to bring the aircraft to a proper spot or touchdown zone on the runway. Three degrees is considered optimum.

Though flights at Mumbai airport can land easily on runway 09, there are no rapid exit taxiways (RET). Hence, aircraft take 30-50 seconds extra to vacate the runway. Also, low visibility during winters can hamper flight operations. Officials said that without the glide path, main runway 27 will be used only when visibility is at least 2,800 meters. Else, runway 09 or the secondary runway will have to be used. These two face heavy tail wind conditions making it tough for big aircraft to land.

"With the glide path, the minimum required visibility on the main runway is 550m. Without it, it goes up to 2,800m. During winters, such high visibility is scarcely possible and landing will have to be moved to the other end of the runway where tail winds are heavy," said an airport official. "This means that certain airlines operating long haul flights on bigger aircraft will have to cut load and fly into Mumbai," he added. Officials also said that in case visibility drops below 1,800m (the required minimum for the 09 end and the secondary runway, the airport will have to be shut. "This, however, is an extreme case scenario," said an airport official.

An MIAL spokesperson said, "A higher glide angle has inherent operational disadvantages such as its unsuitability for Cat-II and Cat-III ILS approaches. MIAL is working jointly with AAI, Airlines and DGCA on this. Trials of the new flight procedures if successful will further enhance CSIA's operational efficiency and safety standards. Also taking all the historical weather pattern into consideration, the trial period is chosen at the best time of the year for getting desired results."