Aviation authorities in India are not in favour of introducing the most advanced Instrument Landing System — CAT IIIC — that assists during zero visibility landings of aircraft. Currently, Delhi’s Indira Gandhi International Airport and Jaipur International Airport are equipped with the second-most advanced ILS system, CAT IIIB, while the other airports are equipped with the older ILS systems. The CAT IIIB system allows compatible aircraft to land in a minimum of 50-metre runway visibility, which is considered a safer option.
A category IIIB operation does not have a “decision height” (the lowest height or altitude while approaching descent) and a runway visual range not less than 150ft (50m), while a category IIIA operation is a precision instrument approach and landing with a runway visual range not less than 700ft (200m).
According to the Directorate General of Civil Aviation (DGCA), a total 1,168 flights have been affected due to poor visibility caused by the weather at Delhi’s Indira Gandhi International Airport during 16 December 2015 to 21 January 2016. “Delhi’s airport is the busiest in India. It handles over 850 domestic and international flights daily. In winters, when fog takes over, both domestic and short haul international flights are affected. Airlines have to change their flight schedules to Delhi and also to other airports in northern India like the ones in Amritsar, Chandigarh etc. But, at times, it proves to be very difficult as these changes happen on a very short notice. Fog is very unpredictable. Weather forecasts seldom help. Passengers reach the airport and then find that their flight is delayed or cancelled,” said M. Sathiyavathy who heads the DGCA.
“CAT IIIC is not a legal requirement. Airlines can choose to install compatible equipment in their airplanes. However, regulations on landing are very clear. For now, CAT IIIB remains the operating procedure. That is the safer alternative. This is the reason we have not pushed for CAT IIIC, even after demands from various sections,” he added. Category IIIC is a precision approach and landing system with no decision height and no runway visual range limitation. That essentially means that an aircraft can land even in zero visibility conditions. It is in place in airports across the world like JFK in New York, Heathrow in London, Hong Kong, Charles De Gaulle in Paris and many more. It is used only sparingly, when the diversion of a flight is not an option.
For an aircraft to land in zero visibility, it must approach a CAT IIIC enabled runway and be equipped with autoland systems that have CAT IIIC capability that take over from the pilot as soon as the plane flares and touches down on the tarmac. However, experts argue that delaying or diverting flights is an easier choice than risking the lives of passengers.
“Airports all across the world usually either cancel landing operations or divert approaching flights to some other airport when visibility drops below 50 meters. Both the airport authorities and the airlines do their utmost to minimise disruptions and inconvenience to passengers. But sometimes the situations are not in our hand. The fog, which is worsened by high levels of pollution, defeats us at times. Landing in zero visibility is not a wise choice. As it is, not all aircraft have CAT IIIC capability,” Marcel Hungerbuehler, chief operating officer of the Delhi’s Indira Gandhi International Airport, told The Sunday Guardian.
“There are many airports in the world which have CAT IIIC capability. It basically means landing in complete blindness. This is generally avoided, and rightly so, as the risks of unforeseen events are huge and can put lives of hundreds at risk. A technical operation like this should never be a gamble,” Amber Dubey, head of aerospace and defense practice at KPMG in India, told this newspaper.
“Operating in near zero or zero visibility also requires taxiways and support facilities at the runway specially designed for such conditions. Also, as takeoffs by civilian aircraft under zero visibility are not allowed by law, there is always a risk of ground congestion at the airport. What happens when the runways, taxiways and hangars are completely filled? CAT IIIC makes sense in emergency cases like when a plane has low fuel and diverting is not feasible, even in bad weather conditions. For tackling such emergency situations, the system should be installed in airports,” Dubey said.
“In CAT IIIB capable airports like in Delhi, compatible airplanes like the Boeing 737 and Airbus 320 are able to land with a minimum of 50 meters clear view. However, smaller aircrafts like the ATR turboprop, which serve short-haul destinations, are not allowed to arrive or depart in low visibility. Delays and cancellations have a cascading effect that creates a huge backlog. All airlines are committed to ensuring the safety of passengers. We have highly trained pilots. The systems in place currently are the ones that we should stick to. Even if we invest in CAT IIIC autoland systems, we would not prefer landing in zero visibility. We like to minimise risk,” said K.M. Unni, chief of operations, Jet Airways.