Chennai: The search for the AN-32 aircraft with 29 people on board that went missing on Friday morning, continued on Saturday with no sightings of any debris in the Bay of Bengal, said an official of Indian Air Force (IAF).
"The search is going on. If there is any substantial development it will be made known," Wing Commander Anupam Banerjee, Public Relations Officer for IAF told IANS over phone from New Delhi on Saturday.
A Coast Guard official told IANS that there was sightings of any aircraft debris in the Bay of Bengal by the search team.
Only a catastrophic accident in a "no talk/radio zone" or "dead zone" could destroy an aircraft suddenly, an experienced pilot with the Indian defence forces told IANS late Friday.
Those on board comprised six crew members, 15 personnel from the IAF, army, navy and Coast Guard, and eight civilians who were family members of the personnel.
The aircraft, an upgraded AN-32 belonging to 33 Squadron, took off from Tambaram Air Force Station in Chennai at 8.30 a.m., and was expected to land at Port Blair in the Andaman and Nicobar Islands at 11.30 a.m., officials said, describing it as a "routine sortie".
According to a report submitted to Defence Minister Manohar Parrikar by Air Force Chief Air Chief Marshal Arup Raha, according to the recorded transcript of Chennai air traffic radar, last pickup was 151 nautical miles east of Chennai, when the aircraft was observed to have carried out a left turn with rapid loss of height from 23,000 feet.
A massive search and rescue operation involving aircraft, helicopters, ships and a submarine was launched immediately to find the plane that went missing around 300 km off Chennai, and will continue through the night.
The last contact with the aircraft was established roughly around 15-20 minutes after the take-off, sources said.
According to IAF, the AN-32 is a twin engine turboprop, medium tactical transport aircraft of Russian origin. It can carry a maximum load of around 6.7 tonne or a 39 paratroopers.
The aircraft's maximum cruise speed is 530 kmph.
"Planes are designed to fly even during an emergency. There will be reaction time to the pilots facing an emergency to send out messages for help or turn towards safety," an Indian defence forces pilot told IANS.
According to the pilot, an AN-32 aircraft will not drop down like a stone or vanish into thin air in the case of normal emergency, as there will be reaction time.
"But in the case of a catastrophic threat, the pilots will not have the necessary reaction time," he said.
An aircraft will not always be on the radar, he noted.
"If the distance to be travelled is around 1,500 km for instance and travel path involves flying over sea then there are chances that the aircraft could not be in the radar from the city of departure after say around 300 km. And it would come into the radar on the other side only when it is around 300 km from its destination," he said.
"So effectively sometimes there will be a dead zone of 700 km. In smaller aircraft, the pilots switch on to the high frequency for being in touch," the pilot added.
Coming to the probable cause of its vanishing suddenly, he said: "The possibilities of different catastrophic events happening in the sky cannot be ruled out."
"For example if an aircraft is caught in a strong thunderstorm, then a plane is as good as a paper caught in the storm.
"The storm will throw the plane like a stone," he said.
According to him, there have been instances when an airplane that was flying at around 35,000 feet altitude dropped down to 5,000 feet but regained control after that.
The other catastrophic events that can happen to a plane were sudden failure of all the engines; devastasting fire; fuel leakage, jamming of flight controls, loss of flight controls due to fire; power and electrical failure and others.
He said in the best case scenario if the AN-32 had come down gradually then it would have been picked up by some radar or the pilots would have the time to react.
Normally a plane is fuelled taking into account the emergency deviations that may arise - the need to go back to the airport from where it took off or to some other nearby airport in case of an emergency, he added.
The incident comes a year after a Coast Guard Dornier aircraft with three crew members on board for a routine surveillance flight went missing.
The search team found its black box nearly a month later. The skeletal remains and personal belongings of the crew members were recovered from the sea bed off the Tamil Nadu coast.