MUMBAI: For the Air India Express flight that crashed in Calicut on Friday, the problems appear to have begun during descent in heavy rains, with difficulty in spotting the runway from the cockpit.
What followed was a host of factors that had the pilots opt to land instead in unfavourable tailwinds, touching down on a wet runway, probably face problems with braking action of aircraft all of which had the Boeing 737 aircraft overshoot the tabletop runway to speed into a gorge, crash and kill 18 people.
It began well with the AIX pilots overflying the runway to line up for an approach to land on runway 28, according to data from flightradar24, a live flight tracking app. The norm is to land an aircraft into the wind and runway 28 had headwinds, favourable for safe landing. But during the descent the pilots appear to have encountered their first problem with weather. Aviation weather report (called METAR, issued every 30 minutes) for that time showed few light clouds at 300 feet. “The pilots probably couldnt spot runway 28 from their cockpit by the time the aircraft descended to 265 feet above ground level. For Calicut airport, this is the height at which pilots have to discontinue the descend to land and carry out a go-around if the runway isnt in sight, said a senior commander, requesting anonymity.
The pilots then decided to try an approach and land from the opposite end, that is on runway 10. They have to seek permission from the air traffic controller, who in turn, consults METAR for wind speed and direction on the runway the pilots have sought permission to land on. “If the runway has tailwinds of 15 kt or higher, it isnt considered safe for landing, said a senior commander. Other pilots said that a tailwind of more than 10 kt for a table-top runway like Calicut should be considered unsafe for landing. The METAR report for the time of accident showed a windspeed of 12 kt, from “direction 260”. It essentially translates to a tailwind of 11 kt for runway 10. But pilots spoke about possible inaccuracies in the METAR report. For instance: in August 2017, a SpiceJet aircraft went off the runway during landing in Calicut airport. The investigation report noted that METAR showed zero winds at the time of incident, but the flight crew experienced winds over 12-15 kt. “From the position of the wreckage it does look like the aircraft landed in tailwinds that were stronger than what METAR reported, said an examiner on B737 aircraft.
There are other crucial questions. The photographs of the wreckage shows the aircraft wings with speed brakes not deployed. Said the senior commander: “We dont know what happened after touchdown. But the AIX commander appears to have switched off the engines. After all, he was an IAF pilot, he would have had the presence of mind to switch off the engine and prevent a possible fire following the impact.
Another factor that a number of pilots spoke about was “aquaplaning, which refers to a condition wherein a layer of water builds between aircraft wheel and runway surface leading to loss of braking action. “Apart from aquaplaning, if there are significant rubber deposits from previous touchdowns as well, then the braking action would be really poRead More – Source