Thiruvananthapuram:The fatal crash of an Air India jet at Kozhikode airport in Kerala on Friday has put the spotlight on what is referred to as 'table top runways and how safe they are to land a plane.
Eighteen people including the plane's pilots were killed. There were 190 passengers on board.
As per preliminary reports, the Boeing 737 aircraft touched down at the mid part of the runway before rolling off a cliff at the end of the airfield.
The captain of the doomed flight Deepak V Sathe, a highly experienced fighter pilot, was a former Wing Commander with the Indian Air Force, who flew MIG 21 aircraft. Later, he was a test pilot with the IAF, before joining Air India. His experience and presence of mind could have helped minimise the fatalities in the plane crash, many experts say.
Sathe’s experience could have given him the confidence to touch down even at the middle of the tabletop runway and land safely. He might have thought that he would be able to control the plane within the 90 metres of runway space - called the Runway End Safety Area (RESA).
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Unfortunately, the aircraft landed on the opposite side RESA, perhaps due to poor runway visibility and bad weather. Strong winds at the time of landing might have also contributed to pushing the aircraft to the end. The heavy downpour might have caused the plane to skid as well.
The flight's black box and the cockpit voice recorder have been retrieved by the Directorate General of Civil Aviation, and a thorough investigation is on into cause of the accident.
A table top runway is built on top of a plateau or a hill. It resembles the top of a table, as it will have gorges at one or all the ends of the runway.
Table Top Runway
However, aviation experts point out that the aviation statutory bodies in India - Directorate General of Civil Aviation (DGCA) and the Airports Authority of India- does not have the term ‘Table Top’ mentioned anywhere in their rulebooks.
We are just using a non-existent, attractive term for our convenience to refer to the runway. Technically speaking, Kozhikode - Karipur airport being referred to as a 'table top airport' itself is wrong. Even the International Civil Aviation Organisation (ICAO), an agency under the United Nations, which changes and forms the principles and techniques of international aviation, does not have any reference to ‘Table Top runways’, the aviation experts say.
The runways at the airports in Mangaluru in Karnataka and Leh in Kashmir are geographically similar to the Karipur airport, as they both have one thing in common - deep gorges at all the ends. Even Kannur Airport in Kerala which began operations recently, have some ends of the runway similar to that of Karipur.
Are Table Top runways safe?
The flight crashed at Karipur during landing, as the aircraft had a Runway Excursion (a term used to refer to a veer off or overrun from the runway as per ICAO) and rolled off the table top, not able to stop and dived into the gorge. This brings forth the question of the safety of such runways.
Many might even think that the mishap could have been averted, perhaps, if the runway was in a plainland rather than the top of a plateau.
The civil aviation techniques and principles in 200 countries, including India, are regulated by the International Civil Aviation Organisation (ICAO) under the United Nations. India, being a member of the organisation, also complies with the rules, regulations and amendments set by the ICAO regarding civil aviation techniques.
READ:|Pilot of crashed AI Express flight earlier flew MiG-21s in IAF
The permission for operations of runways in airports is received according to Article 14 of the ICAO rules. DGCA, which is India’s statutory body in civil aviation, also follows the article 14 of ICAO rules while granting operational permission to the airports in India. DGCA had given permissions to the Karipur Airport only as per the ICAO guidelines.
This means Karipur Airport has been given permissions to operate, based on the guidelines set by the ICAO, under the UN, which is followed in most countries.
Considering these, the experts opined that the statements like ‘flying from the Kozhikode airport is not safe’ and questioning the airport’s safety are baseless.
The runway at Karipur
Each and every airport in India has its own unique and peculiar geographical features. The take-off and landing at each of these airports will be done by the pilots considering these features. Based on the peculiar geographical features of each airport in India, a system has been developed by the DGCA, named Instrument Approach and Landing (IAL) system. Accordingly, there are set guidelines and directions to be followed to land and take off the plane at each airport in India.
For example, the manner in which an aircraft lands in Thiruvananthapuram Airport will not be how the same aircraft lands in New Delhi Airport. The landing and take-off rules at each of the airports they fly to are thoroughly known to all the commercial pilots in India.
In the recent incident, Captain Deepak Sathe did surely know how to land the aircraft at Karipur and did know of the terrain.
Experts pointed out that the runway at Karipur is fairly very long. It is more than 2700 metre, i.e. about 9000 feet, in length. This length is adequate even for jumbo jets to land. So, there is no point in the allegation that the runway at Karipur Airport is not long enough.
The Air India Express flight, a Boeing 737 aircraft, which crashed at Karipur on Friday, is listed under the 4th category as per ICAO rules and regulations. For such aeroplanes, a runway length of 6000-7000 feet would suffice to land smoothly, according to ICAO.
Factors that could have led to the accident:
During landing, the point on the runway at which the aircraft flies down and touches the runway is called the touchdown point. It is not the pilot who decides on this point. There is an automated system in the cockpit which fixes the touchdown point. The pilot only needs to ensure that the automated system operates correctly.
The touchdown point usually is about 200 feet from the point where the runway begins. But, in the presence of strong gusty winds in the runway area at the time of landing, the touchdown point will move a little further. In such cases, the plane will have to run a little longer than normal before pulling to stop.
In case it rains during landing, even if the aircraft touches down on the dot, because of the wetness on the runway, the breaking action may not happen as in normal cases. Then, the aircraft is more likely to run further longer on the runway before breaking.
The rains during landing are generally assessed as an external cause for accidents by aviation experts, much like strong gusty winds, snow, whirlwinds and dust storms.
READ:|Air India crash: Why tabletop runways are tricky to land
It is a fact that when the Air India Express flight landed at Karipur on Friday night, there were heavy rains and strong winds.
Preliminary investigations suggest that the aircraft touched down only past half of the runway length. Why did the Pilot let the aircraft touch down on the runway only after passing half the runway length is not known yet.
The aircraft took a runway excursion and overrun through the runway length and the Runway End Safety Area (RESA) in high speed and nose-dived off into the deep gorge at the end and split into three, killing both the pilots, 18 passengers and leaving many injured. Because the aircraft did not catch fire for whatever reasons, the fatalities could be minimal unlike in the Mangalore flight crash.
It is also assumed that the breaking action did not function effectively due to the heavy rains during landing. The possibility of the tyres being jammed cannot be ruled out, the experts agree.
