The aircraft was operated by Captain Deepak Vasant Sathe, who is an experienced commander. In fact, according to Civil Aviation Minister Hardeep Singh Puri, Captain Deepak had landed aircraft on the Calicut Airport runway about 27 times. However, although the pilot was familiar with the runway, the weather condition in Kerala may not have worked in his favour. A red code alert was sounded in Kozhikode for August 7, and heavy rain had been lashing the district when the flight entered the state.
As the Digital Flight Data Recorder (black box) and Cockpit Voice Recorder of the aircraft have been retrieved, the Aircraft Accident Investigation Bureau (AAIB) is investigating various interdependent aspects that could have caused the crash at the Calicut International Airport. Here are some of the aspects that they could be probing:
Was the runway slippery or contaminated?
Ideally, a runway is dry and smooth. When it rains, irrespective of its intensity, the water will drain out as the slopes are designed to prevent waterlogging. However, the runway can still be damp, which, in this case, is a type of contamination, which can lead to hydroplaning. When the wheels come in contact with a film of water on the runway during a touchdown, the tires will not have enough friction (or grip) when landing, which can cause the aircraft to slip or glide over the runway. In such a situation, braking or manoeuvring will be ineffective, experts say.
It also has to be ascertained if a runway friction test, to ensure smoothness of the runway, was carried out before every landing at the airport.
On Saturday, Civil Aviation Minister Hardeep Singh Puri said that the Calicut International Airport had addressed all the safety concerns the Directorate General of Civil Aviation (DGCA) had pointed out in its 2019 report, including excess rubber deposits, cracks and water stagnation on parts of the runway. However, if these flaws were not addressed, it could reduce the friction of the runway.
Why the aircraft landed at unscheduled runway
The speed and direction of the wind will determine which runway the aircraft will use to land or take-off. In this case, according to reports, the Air India Express flight was scheduled to land on runway 28 (280°), which is in the direction of the westerly wind. When an aircraft lands in a particular direction, it should travel against the wind (headwind), which helps reduce the speed of the aircraft.
However, reports suggest that the aircraft, after two circles over the airport, attempted to land on runway numbered 10 (090°), where the wind is blowing towards the east. Here, the aircraft was travelling with the tailwind, or along the direction of the wind, which added to its velocity, thus reducing its time to reach or halt at the destination on the tabletop runway. This could have caused the aircraft to overshoot the tabletop runway.
Negligence by ATC?
There are allegations that the Air Traffic Control (ATC) at Karipur Airport did not warn the pilots of the unfavourable weather conditions on the ground and allowed the aircraft to land, instead of asking the pilots to divert. According to the preliminary information, the ATC also said that the aircraft landed 1,000 metres away from the threshold marking (beginning of the runway). The AAIB will investigate if the Karipur airport ATC informed the aircrew about the ground conditions.
Amidst these allegations, however, former IAF fighter pilot Group Captain Somala Sreenivas told TNM that it is neither the charter nor the duty of the ATC and other ground airport personnel to instruct the pilot to divert. “ATC is limited to their responsibility of giving advisories on the weather and runway condition. They are not supposed to advice a pilot to divert the aircraft; that is the decision of the pilot based on the inputs he receives from the ground personnel,” he explained.
He also pointed out that there are no blanket restrictions on landing in certain weather conditions. It depends on ground conditions, ratings of the pilot and the radio navigational aids to assist aircraft manoeuvre on the ground.
Landing gear failure?
The Air India Express flight made a belly land on the runway. An aircraft lands on its belly or underside when the landing gear fails to extend due to some mechanical malfunction. However, the former IAF pilot said that usually the pilot or the co-pilot reports such technical issues before landing. There is no question of landing, especially in bad weather conditions, if there was a landing gear problem, he said.
TNM Live: Former IAF fighter pilot Group Captain Somala Sreenivas speaks to TNM's Paul Oommen about the technical details about the #KeralaPlaneCrash https://t.co/Y6m9UvsoWn
— Dhanya Rajendran (@dhanyarajendran) August 8, 2020