The Drishti system at Delhi airport
Drishti - an indigenous transmissometer - would soon help pilots land aircraft at Jayaprakash Narayan International Airport and take off safely in poor visibility condition.
The city airport is in the list of the aerodromes to be equipped with the indigenous runway-visibility instrument Drishti. It helps pilots during landing and take-off, especially in poor visibility conditions.
India Meteorological Department (IMD) had sent a proposal to the Airports Authority of India (AAI) in January to install costly imported transmissometers. But the Delhi headquarters of the Met department recently decided to install four Drishtis along the Patna airport runway.
Drishti is designed and developed by the Council of Scientific and Industrial Research-National Aerospace Laboratories (CSIR-NAL) for IMD.
Informing about the decision to install Drishti, Patna meteorological centre director Ashish Sen told The Telegraph: "Drishti would be fitted at 27 airports across the country. Patna is among the eight airports where the gadget would be fitted in the first phase. Two pairs of Drishtis would be installed on the either side of the runway at the Patna airport. IMD and AAI officials have conducted joint inspection. The procurement order for the equipment has been made to AAI. Now, they just have to deliver them to us."
Aviation experts claimed that the transmissometers installed at Indian airports till now were imported. But their high cost necessitated the development of a cost-effective and highly precise gadget indigenously, which would be on a par with imported transmissometers. This prompted the development of Drishti.
CSIR-NAL and IMD on May 20 entered into an agreement for the joint production of Drishti, which covers a wide range of visibility condition - 25m to 2,000m. Sources claimed that it costs just one-third of imported transmissometers and gives more accurate readings. The price of an imported transmissometer is around Rs 1 crore.
Seven Drishti systems have so far been installed at three international airports - Indira Gandhi International Airport of New Delhi (five systems), Lucknow International Airport (one) and NSCBI Airport of Kolkata (one).
Visibility condition has always been a prime concern at the city airport because of its short runways. It still lacks any digital machinery for measuring the visibility. The visibility for operation of aircraft at this critical airport is assessed through human eyes.
"The present system of using eye estimates for the assessment of the visibility condition is a conventional method and does not give accurate information as required by the modern-day aviation industry. Moreover, it is quite challenging for pilots, as it requires manual calibration with the Air Traffic Controller (ATC). Such a practice is highly unsafe because majority of the accidents in the aviation sector are linked to weather-based situations," said Atul Singh, the executive director of Delhi's Centre for Aviation, Policy, Safety and Research.
Every airport in the country, including Patna, has a meteorological office for providing weather-related information, including visibility condition and forecast required for flight planning and operations, to the ATC.
The ATC at the source airport then conveys the information to ATCs at other locations and all airlines operating their aircraft to and from the airport.
According to the modern-day practices and guidelines of International Civil Aviation Organisation (ICAO), various state-of-the-art-equipment, including transmissometer and instrument landing system (ILS), are used to calibrate the visibility.
A category-1 ILS is functional at Patna airport but it lacks a transmissometer - mandatory at all airports according to the International Civil Aviation Organisation and World Meteorological Organisation.
What is Drishti
Drishti is the only indigenously developed transmissometer, which helps in determining runway visibility range at airports
Requirement of transmissometer
The assessment of visibility at Patna airport is done using human eyes and a detailed scientific map is drawn up using Global Positioning System (GIS). This practice is unsafe and international agencies like International Civil Aviation Organisation and World Meteorological Organisation insist on the use of transmissometer for this purpose
Drishti is the only indigenously built transmissometer of its kind. Its cost is just one-third of imported transmissometers and is considered more accurate
Features of Drishti
Capable of handling both low (25m) and high (2000m) visibility accurately
Remote access and control provided
Web-enabled data accessibility system
How Drishti works
Drishti is suitable for installation in all categories of airports — CAT I, CAT II, CAT III A and CAT III B
It comprises a transmitter that sends collimated beam of light and a receiver that is set up at a distance to collect the transmitted beam
The instrument is set up parallel to airport runway
A detector collects the transmitted light beam and measures the attenuation of light intensity while traversing through the atmosphere
It works on the principle of higher the attenuation factor lower is the visibility of the runway
Data from field site is transmitted to ATC room through cable and Wi-Fi.
A plane touches down at Patna airport amid foggy conditions on Friday afternoon.