New Delhi, Delhi, India

A passenger plane carrying 190 passengers had crashed at the Calicut airport in the southern Indian state of Kerala last year. Now, an investigation has concluded that the crash might have happened due to 'human error'.

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The Air India Express was bringing 190 passengers from Dubai to India as part of repatriation flights in times of the Covid pandemic.

During landing, the Boeing 737 skidded off the runway in rain and crashed landed by breaking in two parts. The crash ended up taking lives of 21 people, including both the pilots and injured nearly 75 passengers.

The extensive probe report cited several factors that led to the tragedy. Here are the main points:

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Bad weather

The aircraft was attempting to land repeatedly in bad weather. First attempt was aborted as the pilots did not find the appropriate conditions to land the plane. However, in their final attempt, the investigators claim, the pilots ended up making several violations.

In such bad weather, a miss on the runway can lead to a disastrous outcome, like the one observed during the Calicut crash.

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Inadequate briefing

The report by India's Aircraft Accident Investigation Bureau claims that the pilots did not carry out "adequate briefing" for landing with tailwinds in the poor weather. The experts believe that a failure to "quickly calculate accurate landing data in adverse weather conditions" led to the deadly crash.

In addition, the pilots also failed to "make the mandatory announcement for the cabin crew to be seated on the first approach for landing... This is a very serious omission and compromises cabin crew".

The pilot also failed to follow the proper protocol and instead of aborting the landing mission, he continued to descend the plane in unstabilised conditions. 

"The probable cause of the accident was the non-adherence to standard operating procedures by the pilot flying, wherein, he continued an unstabilised approach and landed beyond the touchdown zone, halfway down the runway, in spite of a go around call by the pilot monitoring, which warranted a mandatory go around and the failure of the pilot monitoring to take over controls and execute a go around," the report said.

Faulty parts

The windshield wiper of the aircraft was also not functioning properly, the report claims. Experts have concluded that windshield wiper on the PIC side stopped functioning. The pilot in command (PIC) was also recorded giving an unusual detailed briefing to flight officer (FO), which raises doubts that the crew was already familiar with the unreliable windshield but had failed to raise the issue.

Landing in heavy rain with a faulty wiper was not an ideal approach and should have been avoided or delayed, the experts believe.

Compromise on safety

The pilots and the crew members were seasoned experts who were aware of the Indian monsoon. Even then, the PIC continued for second approach of the Kozhikode runway without assessing the risk involved, the report claims. The FO, too, ignored the violation of the SOP.

In addition to this, the Pilot Monitoring failed to make the mandatory announcement for the cabin crew to be seated during the first approach to the Kozhikode runway, which results in another omission of SOP and puts the lives of cabin crew in danger.

The pilot, experts believe, should have assessed the risk involved due to the Indian monsoon and decided to not to divert even after the 'missed approach'. This decision was taken by the pilots even though alternate airfields were available and the aircraft had enough fuel to redirect.

Unprescribed medicines, cognitive deficits

The report has also hinted that there might be a possibility that the PIC was taking some unprescribed medicines that may have "caused subtle cognitive deficits".

Experts said the PIC was taking anti-diabetic drugs which were not prescribed to him by any doctor and those may have caused mild hypoglycaemia.

This "probably contributed to errors in complex decision making as well as susceptibility to perceptual errors. The possibility of visual illusions causing errors in distance and depth perception cannot be ruled out due to degraded visual cues of orientation due to low visibility and sub optimal performance of the PIC's windshield wiper in rain," the report claims.

Human errors and system failures have contributed to the crash of the aircraft, as per experts. "These usually occur due to prevailing safety culture that give rise to errors, mistakes and violation of routine tasks performed by people operating within the system," the report says.