It is a common occurrence during heavy fog and rain that pilots cannot see the runway to land and eventually divert the flight to another airport. But the Indian aviation industry has taken a historic step with a permanent solution to all these problems.
IndiGo’s Airbus A320 landing at Udaipur airport on June 27 was just a normal landing for the passengers. But it was the beginning of a new change in the history of Indian aviation.
For the first time in India, a passenger jet has successfully landed a passenger jet aircraft using India’s self-developed satellite-based navigation system ‘Gagan’ instead of conventional Ground Radio Systems (ILS) at airports.
Although the system has been tested by smaller turboprop aircraft, this is the first time a commercial jet aircraft carrying more than 100 passengers has landed via the ‘Gagan’. With this achievement, India has joined the list of few countries in the world that have utilized space technology for safe air travel for the common man.
Image Credit: Canva AI
∙ What is ‘Gagan’?
Gagan is a state-of-the-art system jointly developed by ISRO and the Airports Authority of India. Gagan signals are transmitted by the GSAT-8 and GSAT-10 communications satellites, which are positioned at the same position above the equator. This ensures uninterrupted coverage across Indian airspace.
Many people confuse Gagan with Navi, India’s own navigation system. But these two perform two tasks.
1. Navy: NAVIGATION is an independent network that helps pinpoint the location of a person or vehicle, just like GPS.
2. Gagan: But Gagan doesn’t provide navigation on its own. Rather, it is an ‘augmentation’ system that increases the accuracy and reliability of existing GPS signals. Simply put, Gagan checks the data provided by the GPS, corrects the errors, and ensures that it is safe for flying.
∙ Why is it not possible to land a plane using normal GPS?
The GPS in our smartphones is perfect for road trips. It shows us where we stand within a few meters. But this accuracy is not enough for a plane with hundreds of passengers descending from the sky at high speed. GPS signals can be distorted when they pass through the air, especially the ionosphere, an electrically charged region at the top of the Earth. Signals may slow down or get lost. This can lead to large errors in the location information received by the pilot.
For India the issue is somewhat more complicated. Because India is located in the region of ‘Equatorial Ionization Anomaly’. Here the atmospheric changes are very sudden and the GPS errors are more prone to increase. That’s why it is not possible to land the plane on the runway by relying only on normal GPS.
∙ How does Gagan work?
As part of the Gagan project, 15 reference stations have been set up across India to address these atmospheric errors in GPS signals. ISRO knows where these stations are located with centimeter accuracy. These stations receive GPS signals continuously. Then, the position shown by the GPS is compared with the actual position of the station.
Since the stations are stationary, the difference between these two measurements is detected as the error in the signal due to the atmosphere. A central processing center calculates these errors and prepares corrections which are sent to the GSAT satellites.
Satellites transmit this updated, accurate information to receivers on airplanes flying through the sky. The on-board computers automatically incorporate these corrections and find the correct path. All this process takes place in seconds. If the signal is unsafe for any reason, the pilot will also get an immediate warning.
∙ Landing and ‘LPV’ approach at Udaipur
At Udaipur, IndiGo operated the LPV approach. Conventional airports require massive ground radio equipment called Instrument Landing Systems (ILS) worth crores to land aircraft safely. These instruments tell the pilot how high to fly and where the center of the runway is.
With the Gagan-based LPV system, the pilot gets accurate horizontal and vertical guidance (direction and altitude) with the help of satellites without such bulky ground equipment at the airport. It helps the pilot to land the aircraft accurately on the runway.
∙ This is a boon for regional airports
India today is going ahead with projects like ‘UDAN’ which connect not only big cities but also small cities by air. But many smaller airports have a huge financial burden to spend crores to install and maintain ILS systems.
This is where Gagan is relevant. Without installing any special equipment at airports, Gagan will help land planes safely even in bad weather with the help of satellites. This will avoid flights being canceled or diverted to other airports due to bad weather. Airlines can operate on time. The development cost of airports in small cities can be halved.
∙ Leap into the future
Gagan’s aim is not only to increase safety in the field of civil aviation. It will help to make traffic management in Indian airspace more efficient and design new short-haul air routes. By this, the fuel economy and time saving of the planes can be ensured.
Gagan is designed to be compatible with other countries’ similar satellite systems (eg the US’s WAAS and Europe’s IGNOS). Hence, international flights can also avail this service while passing through India.
Gagan signals will also make a big difference in the future in the fields of railways, shipping, disaster management etc. That landing at Udaipur was not just an airplane landing, it was the beginning of a new era that would invoke the might of Indian science and make the skies safer.
