Another scare at Mangaluru airport: Why tabletop runways are trickyhttps://indianexpress.com/article/explained/another-scare-at-mangaluru-airport-why-tabletop-runways-are-tricky-5811766/

Another scare at Mangaluru airport: Why tabletop runways are tricky

The incident on runway number 24 — a tabletop runway — brought back memories of the May 22, 2010 crash of Air India Express flight IX 812.

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Passengers alight from the aircraft that veered off the Mangaluru runway on Sunday. (Express Photo)

On Sunday evening, Air India Express flight IX 384 from Dubai veered off the runway at Mangaluru International Airport and halted in soft ground, causing a scare for the 181 passengers on board.

The incident on runway number 24 — a tabletop runway — brought back memories of the May 22, 2010 crash of Air India Express flight IX 812. Both aircraft were Boeing 737-800s and flying the Dubai-Mangaluru route. In 2010, following landing errors by the pilots, the aircraft fell off the cliff at the end of the runway and burst into flames killing 158 of the 166 people on board.

The recent scare

While landing on Sunday, the aircraft veered off runway 24 and came to a halt near the end of the runway. The passengers disembarked at the site where the aircraft was stuck. The aircraft suffered minor damage.

“AI Express aircraft VT-AYA, operating IX 384, Dubai to Mangaluru on June 30, after landing on runway 24 while vacating the runway to the right side, has gone off the taxiway into soft ground,” Air India Express said in a statement. A wet runway, a tailwind and inadequate braking caused the minor mishap, it said.

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Tabletops demand skill

According to a court of inquiry report on the 2010 crash, prepared by former IAF vice chief of air staff  Air Marshal B N Gokhale and a team of experts, “these airfields require extra skill and caution while carrying out flight operations” due to “the undulating terrain and constraints of space”. “The hazard of undershooting and overshooting, in particular, can lead to grave situations,” the report said.

Apart from Mangaluru, Kozhikode airport in Kerala and Lengpui airport in Mizoram are tabletop ones. Runways at these airports, which are located on hilltops, create the optical illusion of being at the same level as the plains below when a pilot comes in for landing.

Until 2006, the Mangaluru airport was using only the 1,625-m runway number 27/06, which restricted usability to smaller aircraft. Runway 24/06, created later, is 2,450m.

“While the length of the runway 24/06 is adequate for operations by aircraft such as Airbus A320 and Boeing 737-800, the downward slope at end of R/W 24 leading into hill slope is not recommended if one is to consider the hazards of overshooting the paved surface during takeoff or landing,” states the court of inquiry report on the crash, dates October 31, 2010.

Why it crashed

The inquiry report cited pilot errors and flaws in the landing process that caused the aircraft overshooting the tabletop runway. “The final touchdown of the aircraft was at about 5,200 ft from the beginning of R/W 24, leaving only about 2,800 ft to the end of paved surface, to stop the aircraft. It is evident from the investigation that the flight crew had failed to plan the descent profile properly, due to which the aircraft was high and did not intercept the ILS (Instrument Landing System) Glide Slope from below, which is the standard procedure. This led to the aircraft being at almost twice the altitude on finals, as compared to a standard ILS approach,” the report said.

Air India Express also specified that “only the Pilot in Command (PIC) should carry out takeoff and landing procedures at Mangaluru airport. But the captain of flight IX 812 was asleep for most of the flight and his faculties may have been dulled by sleep when it was time to land, the inquiry report stated. “The Court of Inquiry determines that cause of this accident was the Captain’s failure to discontinue the ‘unstabilised approach’ and his persistence in continuing with the landing, despite three calls from the First Officer to ‘go around’ and a number of warnings from EGPWS (Enhanced Ground Proximity Warning System),” the report said.

As per the digital flight data recorder, the aircraft crossed the landing threshold “at about 200 ft altitude with indicated speed in excess of 160 kt [knots], as compared to 50 ft with target speed of 144 kt for the landing weight”.

What happened after

The inquiry report recommended installing of  Engineering Material Arresting System in the overshoot area of tabletop airports. “In case it is not cost effective, then at least a Soft Ground Arrestor (SGA) should be available as part of RESA (Runway End Safety Area),” the report said.

“Considering the large momentum of these aircraft, a downward slope in the overrun area can worsen the outcome. It is therefore recommended that such downward slopes as in Mangaluru, be brought to the same level of the runway surface. This also needs to be ensured at all tabletop airports in the country,” the report said.

In 2011, the Airports Authority of India raised the sloping terrain at the end of the runway to the same level as the runway. This was done at a cost of Rs 3.5 crore. Markers have been placed on the runway to indicate remaining distance for landing and takeoff.