NEW DELHI, Sept. 8 -- Aircraft maker Hindustan Aeronautics Limited (HAL) on Sunday put the spotlight on the importance of maintenance for the continued airworthiness of the locally made Dhruv advanced light helicopters, adding that it was working closely with the Indian Army to ascertain the root cause of a defect in the chopper's tail drive shaft - a vital component of its transmission system. The development came a day after HT cited an official communication and reported that the army recorded a worrying incident involving damage to the helicopter's tail drive shaft (TDS) during flying operations, forcing it to immediately issue orders for a one-time, fleet-wide safety check. "One-Time Check (OTC) is a routine maintenance practice issued...