Lack of underwater beacon hampers search for Indian air force plane

CHENNAI , India, Aug. 2 (UPI) -- The search for an Indian air force plane, missing over the Bay of Bengal with 29 people aboard, has been hampered by the plane's lack of an underwater locator.

The Russian-made AN-32 plane was not equipped with an underwater locator beacon, or ULB, a basic safety device. Emergency locator transmitters were installed during its September 2015 upgrade, but the ELTs are of little use underwater, officials said.

The search of 174,000 square miles covers water which has an average depth of nearly 10,000 feet.

The Indian Air Force has 101 planes of the model missing and lost in the Bay of Bengal, and is hurrying to equip each with ULBs, which are synchronized with flight data recorders and are activated if the plane goes underwater. A signal is transmitted on ultra-low frequencies, which can be heard by submarines and other underwater vessels, for one month.

Search teams are also seeking oil slicks and evidence of aviation fuel in the water.