How Pilots Land Planes in Fog and the Tech They Use

Here’s how pilots safely land planes in dense fog relying on instruments alone. We explain the how the tech works.

The Indira Gandhi International airport supports CAT IIIB technology.

(Photo: The Quint)

It’s the same story every winter season in Delhi. Flustered flyers stranded at the Delhi airport waiting for hours for the green “Now Boarding” sign to pop up on the information display.

Wednesday, 3 January brought new troubles for fliers as air fares had been hiked by almost 28 percent due to cancellations and delays because of the dense fog.

What’s puzzling is that the Indira Gandhi International Airport in Delhi is equipped with the state of the art anti-fog landing system, which in more technical language is called CAT IIIB Instrument Landing System (ILS). This helps planes land during dense fog and inclement weather conditions when visibility is low. And yet there are delays.

Why this happens isn’t really what I am here to focus on. Rather, I am here to talk about the tech that helps planes land safely.

What is Instrument Landing System (ILS)?

ILS is a guidance system that helps planes land in low visibility conditions with the help of radio signals and also sometimes high-intensity lighting arrays. The Delhi airport has been equipped with the CAT IIIB system (short for category 3) which is operating on three runways.

A CAT IIIB system helps with a precision approach and landing when the runway visibility is at a distance no less than 50 feet (15m) and is at a visual range less than 200 meters and most certainly not less than 50 metres. The whole process is automated. There is a voice that prompts (via a countdown) how far the plane is away from the runway, when the flaps have to be deployed and subsequently when the brakes have to be applied.

The only other airports in India that support this technology are in Amritsar, Jaipur and Lucknow. The Netaji Subhas Chandra Bose International Airport in Kolkata is the latest one to receive CAT IIIB technology.

Currently, only the CAT IIIC system surpasses this technology, which can land planes even in zero visibility. There are only a few airports that use this tech including New York’s JFK International Airport and the Heathrow airport in London.

Are Flights, Pilots & Airports CAT IIIB Compliant?

Acquiring CAT IIIB certification requires the airline provider’s fleet to be equipped with the technology and have trained pilots to operate that tech. Flights which are not CAT IIIB compliant do not operate in regions where fog or low visibility is expected.

Some of the airlines that support CAT IIB in India are Vistara, Air India Express, Indigo and Jet Airways among others.

The real battle for airline companies is training the pilots who can operate CAT IIIB equipped planes as that seems to be the major problem.

Not all pilots flying domestic airplanes are trained to land on the CAT IIIB system. Presently, the DGCA is very strict about pilot training with regard to CAT IIIB system, but some domestic airlines tend to avoid this. It is an expensive affair too as the training can cost nearly Rs 10 lakh per pilot.

VP Agrawal, former chairman of Airport Authority of India to <a href="https://scroll.in/article/823934/delhi-airport-has-advanced-tech-for-low-visibility-landings-so-why-does-fog-still-disrupt-flights">The Scroll</a>

There is no other tech apart from this that the airports can install to battle low visibility. Although, there is some extra hardware like a glide slope station that needs to be installed near the runways and all around the airport in order for the ILS to work.

This equipment relays information like distance to the runway, angle of approach, etc to the computer on-board the plane in order to carry out a smooth landing.

Why the Delay?

Many a times it’s not the absence of pilots or the technology that is the problem. A lot of financial and logistical constraints too play a part in flight cancellation and delays due to fog. BJP lawmaker and party general secretary Ram Madhav realised this during his recent visit to the Delhi airport.

The initial cost of setting up the whole CAT IIIB system is an expensive affair. The initial cost of setting the system at an airport can go up to Rs 10 crore and the cost of maintaining such a setup can cost around Rs 50 lakh on a monthly basis.

The three factors that have to be considered for the CAT IIIB system to work at its optimum efficiency are — training of pilots and co-pilots on the system, cockpit (aircraft) compliance and airport compliance. Sadly, that’s not the case in India.

Another reason flights may be delayed is because of the cascading effect the delay of one flight has on the others to follow. This happens regardless of inclement weather or just a normal delay.

So, despite the tech, you can still expect some delays until a proper flight management and scheduling system is established and also pilots and airports are equipped to supports high tech anti-fog systems like the CAT IIIB ILS.