For the record, let me repeat.
1) Landing an empty aircraft in under 3500 feet in New Delhi is not the same as landing an aircraft loaded with 160,000 pounds of cargo on a 3,500 foot runway. A few days ago, I posted a video of an An-124 landing in 4000 feet on Paine field (the home of the main Boeing plant in Seattle). It was probably empty. They would never have risked landing it on an actual 4000 foot RUNWAY.
2) Tests have demonstrated that the C-17 uses much more runway when the surface is wet than when it is dry. That is true of all aircraft, but in the case of the C-17 it is significantly higher.
From
this document
Current guidance indicates that the minimum size semi-prepared runway for C-17 operations is 4,100 feet long by 90 feet wide (AFCESA/CES, 97). This includes the 3,500 foot landing surface and two 300 foot overruns on each end of the runway. Given current procedures, a 4,100 foot runway would only be of use during dry runway conditions since planned stopping distance increases greatly under wet conditions when using an RCR of 4 as discussed previously. The Engineering Technical Letter, which provides guidance to civil engineers indicates that C-17s require a 7,000 foot runway during wet runway operations (AFCESA/CES, 1998). Obviously the requirement for an SBA could arise in any type of climate and weather and the ability to find 4,100 feet of useable surface is easier to find than 7,000 feet.
3) The aircraft has a high footprint that exceeds the capabilities of 99.9% of unpaved runways in the world (which is not the case of the IL-76 which was made to use the existing unpaved runways that are long enough)
I already posted this information but read again what this November 2009
GAO Report to the Subcommittee on Air and Land Forces, Committee on Armed Services, House of Representatives tells us:
However, there is a potential gap in the tactical airlift of medium weight loads beyond the capability of the C-130s. The C-17 is the only aircraft capable of moving this type of Army equipment within a theater of operation, although not to austere, short, or unimproved landing areas.
A potential capability gap exists in the department’s ability to airlift medium-weight vehicles to access-challenged areas within a theater of operations using dedicated tactical airlifters. C-17 aircraft have been employed to transport medium weight vehicles in theater, but cannot access austere, short, or unimproved landing areas. In 2007 C-17s flew 15,436 tactical sorties, 3,102 of which—approximately 20 percent—involved carrying objects too large for a C-130 to carry. Nevertheless, DOD officials do not consider the C-17 to be a viable long-term solution given access issues noted above. JFTL is expected to provide this long-term solution.
They are still pondering what form the JFTL will take. It might just turn out to be the Airbus A-400M.
