In fact, none of the upgraded AN32 aircraft, the main workhorse of the military, has an underwater locator, unlike the modern transport planes like C130J or C17.
This means that the search and rescue team has no exact idea about where the plane, with 29 military personnel on board, could have gone down on July 22.
"We are using sonars of submarine, ships and other naval assets to locate the aircraft. There is no signal available to track the missing aircraft," a defence source said, adding the search will continue.
The missing aircraft came with two Emergency Locator Transmitter (ELT) -- a stationary ARTEX C406-1 ELT manufactured by ACR Electronics/Artex Products, the US, and a French-made portable KANNAD 406AS ELT manufactured by Orolia.
In an emergency, the pilot has to activate the ELT beacon manually. The integrated ELT gets activated when the impact is about 2.3 G or 4.5 feet per second.
The sources said trials were already on to procure underwater ELTs for the aircraft and, as an emergency measure, effort is to have some kind of an underwater ELT on any aircraft that flies over water.
Also, the AN-32 aircraft does not have the Automatic Dependent Surveillance - Broadcast.
This system relies on navigational satellites to automatically transmit an aircraft's journey in real time and it can be switched on and off based on operational needs.
It was only at 1225 hours that Maritime Rescue and Coordination Centre, Chennai reported that an IAF AN-32 (AF-330) was not in contact. The weather at the time when the plane went missing was overcast with multi-layered clouds and embedded convection.
The pilot had asked for deviation to the right to avoid a thundershower cloud before disappearing.
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