Indian Armed Forces have an area of responsibility which extends to far corners of the nation. From deep seas in the south & dense jungles of the northeast to dry deserts of the west & icy heights of the north, men in uniform cover it all. There is one such territory that the Indian Army defends in the northernmost corner of Ladakh, the Siachen Glacier, a remote, isolated & extremely hostile area. Located at 21,000 feet, it is also the highest battlefield in the world. For reference, commercial aircraft fly at 35,000 feet. The real enemy here isn’t the Pakistani or Chinese Forces, it is the weather & the terrain.
The glacier has a massive span, with an area covering 2,500 sq. km where the Indian Army maintains a permanent military presence round the clock 12 months a year. To keep these brave souls supplied with rations, medical supplies, food & ammunition, Indian Air Force has an equally robust supply chain. And this supply chain depends on some truly radical machines.
Enter the HAL SA 315B “Cheetah”, a purpose-built helicopter capable of undertaking operations at hot and high conditions.
Before getting to know the Cheetah, understand the dynamics of high altitude flight. The turboshaft engines of a helicopter generate power by the combustion of fuel-air mixture. To perform at the optimal rated power, the engines need to suck in a lot of air & burn the oxygen in it. Now, with the increase of altitude, the air density (& hence oxygen) reduces. Air density decreases by 33% at 10,000 feet compared to what it is at sea level. With further rise in altitude, the air density drops further, which means lesser air is available for combustion & hence the engine produces lesser power. Thus, it needs to make more effort to keep the helicopter flying. Also the rotor blades slice through significantly lesser dense air which further reduces the lift capacity. Hence, to fly a helicopter in a mountainous terrain, it needs to have a lightweight airframe with tremendous amounts of power reserve margins.
Coming back to the Cheeta, This is a barebones helicopter with minimal essential equipment & body panels to keep the weight low so as to carry that extra kilogram of supply needed at high altitudes. Indian Forces specifically required this type of chopper because even relatively powerful medium-sized helicopters could not effectively operate in the challenging environment of the Siachen. Hence Aerospatiale, the original manufacturer of the Cheetah, combined the lightweight airframe of Alouette II with the powerful engine & transmission of Alouette III. As a result evolved the sports car of helicopters, the SA 315B Lama, which was called Cheetah as it started production with HAL in 1973. Production ended decades later after about 300 helicopters entered into service.
It is a simple design with a 360-degree high visibility polycarbonate canopy needed to manoeuvre in tight spaces & “matchbox” helipads, and comes with a rugged tubular frame construction. The cockpit is very basic with equipment only necessary for flying & communication. The engine, transmission & the 575 litre fuel tank are exposed to the environment. The empty weight is just over a ton but thanks to the high power to weight ratio, it can carry up to 1,100 kg in the underslung load. However, while operating in the high altitude regions such as the Siachen, the usable payload decreases to 225 kg. It has five seats in a classic 2 + 3 configuration, much like cars today. When fully fuelled, it has a range of 560 km & an endurance of 3 hours. The cruising speed is 192 kmph which is not very much as per modern helicopter standards but this chopper is not built for speeds.
It gained popularity & good reputation with the Indian Armed Forces as it proved to be capable of operating in difficult & remote areas like the Siachen & such heights in the J&K-Ladakh region with minimal ground support. In Siachen where the temperatures drop to -50 degree, the Cheetah is pretty much the lifeline of the troops. Even if a Disprin tablet has to go at an Indian Army post, it goes in a Cheetah from the No. 114 Helicopter Unit, also known as “Siachen Pioneers”. They are based out of Leh airbase at 11,500 feet & what they do can be summed up in the squadron’s motto “We do the difficult as a routine, the impossible may take a bit longer.”
The Cheetah is pushed to its technical limits on a daily basis for missions like logistics support, rescue operations, surveillance & MEDEVAC (medical evacuation) not only at Siachen but at all the high altitude posts in the region. Most medical emergencies at Siachen are due to the lack of oxygen, troops face altitude sickness or even Hypoxia. In this condition they urgently need medical support as every minute is crucial for survival. In these situations, Cheetah Helicopter units are pressed into action which can evacuate a soldier from Siachen & bring him to the Leh military hospital where he is provided the medical attention needed. An entire operation like this takes 40 minutes from start to end. On a typical day in Siachen, a helicopter takes off every 7 minutes & most missions are MEDEVAC missions.
The Sonam Post is the resupply base at Siachen which is also the world’s highest helipad at 21,000 feet. Interestingly the Cheetah has a service ceiling of 22,000 feet which just clears the altitude of Sonam Post. Ration, ammunition & medicines are lifted from Leh & Thoise to Sonam Post & other landing zones to keep the troops resupplied for sustained deployment.
The pilots too need to undergo a specialised training before operating at these altitudes because due to the difference in air density, the same Cheetah helicopter has a different behaviour when flying at Siachen than flying at “normal” altitudes. This training is also important because at Siachen, usually the landing zones are nothing but makeshift wooden platforms which are slightly bigger than the helicopter skids. The pilots need extensive training to be able to manoeuver the machine with pinpoint precision to be able to land on them.
Just like in fighter flying, every pilot needs to undergo a preflight medical exam before every flight to the Siachen. This is to make sure they are in the top of their health to face the extreme weather conditions they are going to face when the helicopter door opens in Siachen. The seriousness of this can be understood by the fact that till today, 14 pilots from “Siachen Pioneers” helicopter unit have laid down their lives in service of the nation in various accidents. In the last 50 years of existence, the No. 114 Helicopter unit has received 51 Gallantry Awards.
The maintenance crew have a different problem. Cheetah is a single engine helicopter which means there is zero margin of error. An engine failure cannot be tolerated & hence the crew servicing the helicopters need to ensure that the engines are in their best running condition round the clock. Considering the fact that the helicopters are 3-4 decades old, this job becomes even harder.
The Cheetah is almost half a century old design, but that has not stopped it from being a useful tool to support the military deployment in inhospitable terrain like Siachen. However, a modified version of Cheetah, the Cheetal was a planned replacement, It borrows the more powerful Turbomeca TM333 engine of the ALH Dhruv helicopter. Some Cheetal helicopters have been inducted but are in limited service. The more practical replacement of the Cheetah is the ALH Dhruv MkIII helicopter. The Dhruv MkIII is a bigger & more powerful helicopter with two 1,400 shaft horsepower engines. Being a twin engine helicopter it is not only safer to fly the Dhruv MkIII but it can also carry more payload. During tests, the Dhruv has carried 600 kg load to Sonam Post against the army’s requirement of 200 kg.
As they say, it is not the machine, but the man operating it that wins the war. Here at Siachen & other high altitude regions, it is an everyday war that the troops need to win every single day. This confidence comes from the belief that machines like Cheetah & now the Dhruv MkIII along with their crew are in a constant state of alert to bring them anything they need & also bring them out, if need be.