Coldest day in Delhi; dense fog envelops airport; visibility zero

NEW DELHI, Jan 12: Delhi experienced a severe cold wave on Friday, with the temperature dipping to a chilling 3.9 deg C in the wee hours. The city was also enveloped in a thick blanket of fog, reducing visibility significantly.

The day started with a dense fog that covered the city, causing a significant drop in temperature. The Indian Meteorological Department reported that the visibility at the Delhi airport was near zero in the early morning hours.

This dense fog is a common occurrence in Delhi during the winter months, particularly in January.

The cold wave conditions were severe, with the minimum temperature recorded at 3.9 deg C. This was a sharp drop from the previous day's minimum temperature of approximately 7 deg C. The maximum temperature for the previous day was less than 15 deg C, providing little respite from the cold.

The weather affected daily life and disrupted flight schedules. However, the use of advanced technology like the CAT III navigation system ensured the safety of air travel during these adverse conditions.

The foggy conditions triggered the activation of the CAT III navigation system at the Delhi airport. This system is designed to help planes land safely during dense fog and inclement weather conditions when visibility is low. It allows for landings with a minimum visibility of 50 metres. Despite this, the fog led to delays in several flights as some aircraft are not CAT III compliant.

Precautions for travel in fog: During dense fog, it's important to take certain precautions, especially if you're driving. Here are some expert suggestions:

Slow Down: Reduce your speed to ensure you have enough time to react if traffic slows or stops suddenly.
Use Low-Beam Headlights: Make your vehicle visible to others both ahead of you and behind you by using your low-beam headlights. This means your taillights will also be on.
Use Fog Lights: If your vehicle is equipped with fog lights, use them along with your low-beam headlights.
Avoid Abrupt Stops: Unless absolutely necessary, avoid making abrupt stops in the middle of the road.
Use Indicators: Always use your indicators when changing lanes or making turns to alert other drivers of your intentions.
Stay Updated: Keep track of the latest weather forecasts and take necessary precautions.

Remember, safety should always be your top priority. If the fog is too dense, it might be best to delay your trip until conditions improve. Stay safe!

What is CAT III: CAT III, or Category III, is an Instrument Landing System (ILS) used at airports, including Delhi's Indira Gandhi International Airport, to enable aircraft to land in low visibility conditions. This system is particularly useful during dense fog and inclement weather conditions when visibility is low.

The CAT III system at Delhi airport is a state-of-the-art anti-fog landing system known as CAT III B Instrument Landing System (ILS). It helps planes land with the aid of radio signals and sometimes high-intensity lighting arrays. The system allows for landings with a minimum visibility of 50 metres. CAT III B has an additional ability to stop itself after landing on the runway, compared to CAT A.

In the CAT II system, a pilot is guided by the signaling system till 100 feet above the ground, when the runway isn’t in sight. In CAT III-B, an aircraft can descend till 50 feet above the ground because of the advanced signaling system. Then the pilot would see the approach and touchdown zone-lighting system.

In category III B approach, the entire process is automated and a voice prompt tells using a countdown how far the plane is away from the runway, when the flaps have to be deployed and when the brakes need to be applied.

The initial cost of setting up the whole CAT III B system at an airport can go up to Rs 10 cr and the maintenance cost can go around Rs 50 lakh on a monthly basis.

CAT III B airports: The airports equipped with the CAT III B system to ensure the safety of air travel during adverse weather conditions in India are: Delhi's Indira Gandhi International Airport; Netaji Subhas Chandra Bose International Airport, Kolkata; Kempegowda International Airport, Bengaluru; Amritsar Airport.; Jaipur Airport; Lucknow Airport

CAT III is not airline-specific: It's important to note that the use of CAT III is not specific to any airline but rather depends on the equipped aircraft and the airport's facilities. Most modern commercial aircraft are equipped with CAT III ILS capabilities, and many airports around the world have CAT III ILS installed on at least one of their runways. Therefore, airlines operating these aircraft and flying to these airports would be able to use the CAT III system.

For safety reasons, aircraft must be certified and system-compliant and the pilots trained to use the CAT III systems.

Types of aircraft landing systems: There are several types of aircraft landing systems used around the world. Here are some of them: -

Instrument Landing System (ILS): This is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. It uses two directional radio signals, the localizer for horizontal guidance, and the glide slope for vertical guidance.
Microwave Landing System (MLS): This is a type of precision approach system that uses a set of radio signals to provide precise lateral and vertical guidance to an aircraft approaching and landing on a runway.
Joint Precision Approach and Landing System (JPALS): This is a differential, GPS-based precision landing system that guides aircraft onto a carrier deck or a land-based runway in all weather conditions.
Autoland: This is a system that fully automates the landing procedure of an aircraft's flight, with the flight crew supervising the process.
Transponder Landing System (TLS): This is an all-weather, aircraft-independent landing system that provides precision guidance for a variety of aircraft types.
Precision Approach Radar (PAR): This is a type of radar guidance system designed to provide lateral and vertical guidance to an aircraft pilot for landing, until the landing threshold is reached.

Each of these systems has its own unique features and is used under different circumstances depending on the requirements of the aircraft and the airport.