The Central Scientific Instruments Organisation (CSIO) laboratory has developed drogue illumination system for light combat aircraft Tejas, making India third in the world after the US and France to have this technology. This will enable airto-air refuelling, which is not possible during night/cloudy skies for fighter aircraft. The system is expected to be ready by year-end. Also, the indigenous lighting system will be one fifth of the cost available with offshore vendors and have greater illumination even than Rafael.
The Rs 2.51 crore project is funded by Aeronautical Development Agency, Bangalore. The illumination system is fitted outside the cockpit. Presently, the illumination system is undergoing rigorous certification tests by the ‘Regional Centre for Military Airworthiness’, an agency under the IAF.
Usually in fighter aircraft, which carry ammunitions, the external fuel tank is removed to adjust weapons and therefore there is shortage of fuel after 45 minutes of flight time. “However, none of the fighter aircraft in our country has illumination system for night. A pilot cannot land during a military operation and therefore lighting system is significant,” said Harry Garg, a scientist at the CSIO associated with the project. He said, “We have been informed by the IAF that only France and US have drogue illumination systems.”
The drogue light is an external lighting equipment to provide illumination of mother aircraft/tanker (the heavy aircraft that is ahead of the receiver aircraft which needs the refuelling) during air-to-air refuelling at night or low visibility conditions.
During the flight, at high altitudes there is low pressure and lot of drag force that results in vibration. This makes it tough for air refuelling as the system needs to be stabilised during the flight. For correct alignment of the receiver aircraft, the drogue needs illumination. “We have made the system using 5 LEDs, reducing the consumption from 1100 watts t0 200watts. Due to our optical design, we have been able to provide light intensity of 12 LUX, which is the highest as compared to the systems provided in the aircraft by France and the US,” said RK Sinha, director, CSIO. What is drogue?
For air-to-air refuelling, there is a technician inside the tailend of the tanker aircraft (mother aircraft) who unspools a long hose from that side. At the end of the hose is a drogue, that looks like an umbrella and reduces the drag force that vibrates the plane. Once the hose is fully extended, the receiver pilot manoeuvres a retractable probe mounted on the plane’s nose into the drogue. Both the drogue and probe is used for airto-air refuelling.
“As the circumference of the drogue is 40 metres, the pilot of the receiver aircraft cannot see anything and therefore cannot manoeuvre the probe during refuelling during low visibility conditions. So, we have designed the system is such a way that both the technician who refuels and the pilot in the receiver aircraft can see the drogue and the probe getting attached for refuelling,” said Harry Garg, a scientist at the CSIO associated with the project.
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