Military air transporters are inherently multi-role as the same aircraft can perform a host of support operations. When modified, it can be used as air-to-air refuellers or, in extreme cases, be converted to act as heavy bombers.

Revolution in military technology has made it possible for a combat aircraft (bomber) to attack a target anywhere in the world and return to its home base without having to take recourse to landing at an intermediary base. The US B-1/B-2 bombers showcase such offensive capability. But this capability alone cannot win wars—for that, ‘boots’ are required on the ground. This is where military transport aircraft come to the fore, affording the fastest means available to ferry personnel and war material to the area of operations.

Military air transporters are inherently multi-role as the same aircraft can carry cargo/personnel, deliver para-trooping airborne forces directly into combat zone, evacuate casualties when required and, a host of support operations. When modified, it can be used as air-to-air refuellers or, in extreme cases, be converted to act as heavy bombers delivering tonnes of free fall weapons over enemy territory.

Fixed wing military transport aircraft, depending on their range capability, are categorised as strategic airlift or tactical airlift. These roughly correspond to the commercial flight length distinctions of long-haul (more than six hours), medium-haul (three to six hours) and short-haul (less than three hours), giving the corresponding aircraft intra-theatre, intertheatre and inter-continental capabilities. The other distinctive characteristics could be based on their payload capabilities such as light (less than five tonnes), utility/medium (five to 10 tonnes), medium-heavy (10 to 20 tonnes), heavy (20 to 40 tonnes) and very heavy (greater than 40 tonnes), respectively.

Design Parameters: Breaking New Ground

But the demands of modern warfare are such that irrespective of ranges or payloads capabilities, all aircraft are required to deliver their payloads at the very doorstep of operational locations, or as close to it as possible. It is this trend that has taken the centre stage of design parameters in all the military transport aircraft launched recently or under development. Take the case of the US Boeing C-17 Globemaster III, which is so ably supporting the US’ Global War on Terror. According to latest reports in the media, the Government of India has granted in-principle approval for the acquisition of 10 C-17 Globemaster III for the Indian Air Force (IAF) at an approximate cost of $2.5 billion (Rs 11,410 crore) through the Foreign Military Sales route.

The C-17 has been designed for strategic airlift of troops and cargo to not only the main operating bases but, also, forward operating bases throughout the world. It has the ability to rapidly deploy a combat unit to a potential battle area and sustain it with regular supplies. The C-17 is also capable of performing tactical airlift, medical evacuation and airdrop missions. The C-17 is designed to operate from runways as short as 3,500 ft and as narrow as 90 ft. In addition, the aircraft can operate out of unpaved and unimproved runways. For cargo operations, this massive aircraft with a max payload capacity of 77 tonnes needs a crew of just three (pilot, copilot and loadmaster). Cargo is loaded through a large aft door that can accommodate both rolling stock and palletized loads. Imagine the C-17 airlifting a 70-tonne M1 Abrams tank right into the heart of ground battle! Yes, it is entirely possible.

Other latest aircraft, such as the European Airbus A400M and the Ukraine/Russia An-70, though differing considerably in design (especially in the use of power plants) are striving for similar off-field capabilities. The A400M, that successfully completed its maiden flight on December 11 last year, has wings primarily made of carbon fibre reinforced plastic. The aircraft is powered by four Europrop TP400-D6 engines rated at 8,250 kW each which make them the second most powerful turboprop engines ever produced, next only to the D-27 propfans to be fitted on the bigger An-70 airlifter.

Another revolutionary concept showcased by the A400M is that the propellers on each wing of the aircraft turn in opposite directions, with the tips of the propellers advancing towards the midpoint between the two engines. The counter-rotation is achieved by the use of a gearbox fitted to two of the engines. Otherwise, all four engines are identical and turn in the same direction which eliminates the need to have two different handed engines for the same aircraft, thus simplifying maintenance and supply costs. The unique configuration, dubbed as DBE (Down Between Engines), allows the aircraft to produce more lift and lessens the torque and prop wash on each wing. It also reduces yaw in a worst-case scenario of an outboard engine failure. While using similar composite materials and ‘fly-by-wire’ systems, the An-70’s D-27 propfan engines, on the other hand, incorporate a pair of contra-rotating scimitar propellers each. With this arrangement the engines can reach 90 per cent efficiency in cruise at jet speeds but with turboprop fuel consumptions.

Brazil’s Embraer is another manufacturer which is trying to develop a twin-jet military transport in the 10-20 tonnes category. Once again, design goals include ability to operate from short and unpaved runways without need for ground support. Use of composites is also being planned with an intended max payload capacity of 19 tonnes.