According to IAF sources, the trials began in the hot deserts of Jaisalmer in Rajasthan last week and will be followed by similar gruelling tests in the icy Himalayan heights of Ladakh in Jammu and Kashmir.
The sources said the competitors will demonstrate high altitude flight capability and maneuverability in Ladakh early next month.
They said the IAF requires a helicopter that is twin-engined with high maneuverability, adequate armour and all-weather and all-terrain capability.The US and Russian helicopters were left in the fray after two major competitors from Europe - the Eurocopter Tiger and the AgustaWestland A129 Mangusta - pulled out of the contest citing technical reasons.
The IAF urgently needs a new fleet of attack helicopters as its Mi-25s are being phased out. The $550 million-tender to replace the ageing helicopter fleet was issued last year. The tender had actually been released in early 2008 to six contenders - Sikorsky for the Black Hawk, Boeing for the Apache AH 64D, Bell for the Super Cobra (all three from the US), Eurocopter for the Tiger, Russian Mil for the Mi28 and AugustaWestland for the Mangusta.
Sikorski and Bell did not compete due to what they said were time constraints and procedural bottlenecks within their country.
The Mi-28 is an all-weather day-night two-seater anti-armour attack helicopter. It carries a single gun in an undernose barbette, plus external loads carried on pylons beneath stub wings. It has two heavily armoured cockpits. Its engines are two 2,200 hp Isotov TV-3-117VM (t/n 014) gas turbines.
The Boeing AH-64D Apache is a four-blade, twin-engine attack helicopter with tailwheel-type landing gear and a tandem cockpit for a crew of two. It is adaptable to numerous roles within its context as a close combat attack craft and has a customisable weapons payload.
Boeing has also developed capability in the Apache to control unmanned aerial vehicles (UAVs). While so far this ability is restricted to control over a single UAV, the company is building systems to allow airborne control over multiple UAVs. But this has not been offered to or requested by the IAF.
The sources said test field trials to select a heavy lift helicopter for the IAF will begin next month and the same US and Russian companies will be in race. Boeing's Chinook, which operates for NATO forces in Afghanistan, will compete with Russian Mi-26 for the deal for 15 heavy-lift choppers.
The IAF is looking to replace the ageing lot of the previous generation Mi-26s inducted in the mid 1980's.
The Chinook, which has contra-rotating twin-rotors to withstand rough weather, is being used extensively in Afghanistan to maintain steady supplies to the troops. It can also carry artillery guns slung under its belly to be dropped off at inaccessible locations.