New Delhi: The air force has warned of a crisis looming on the troops at the world’s highest battleground, Siachen Glacier , as Hindustan Aeronautics Limited (HAL) fails to manufacture the rotor blades critical for its light helicopters.The soldiers deployed at an altitude above 20,000 feet depend heavily on the hardy fleet of Cheetah and Cheetal choppers for missions like casualty evacuation and critical supplies.The French-origin light choppers are now manufactured by the state-owned HAL. The specialised rotors blades give them adequate lift for operating at those punishing altitudes in unpredictable weather. HAL started making the Cheetah choppers in India in 1972. The air force expressed deep concern on the future of the ageing Cheetah fleet as well as its order for 10 Cheetal helicopters after HAL failed to produce the 85-series main rotor blades after their French parent stopped making the blades in 2012.The defence ministry was informed late last year that the 12 blades HAL had manufactured with transfer of technology from the original manufacturer Airbus Helicopters showed high level of vibration and were rendered unsuitable.The aircraft manufacturer is now down to its last few lots of rotor blades that were ordered before 2012, questioning their ability to support the helicopters in service. The availability of the fleet could come down if replacements are not in place, the air force informed. The air force is also concerned that its September 2015 order for 10 Cheetal helicopters will be impacted because of the non-availability of the 85-series blades. The helicopters were to be delivered last year as per the original schedule. The worries of the air force were compounded by the fact that a larger plan to replace the ageing fleet with the Russian-made Kamov Ka 226 helicopters has not taken off yet.