Lockheed Martin is studying a bigger Hercules to meet the potential requirement to carry the Army's ever-heavier FCS vehicles (see Bill's Ares post), but doesn't think the "C-130XL" would ever replace today's C-130J.
C-130XL concept: Lockheed Martin
In addition to stealthy STOL and tiltrotor VTOL concepts for the embryonic US Air Force/Army Joint Future Theater Lift (JFTL) requirement, Lockheed's Skunk Works is looking at three notional sizes of C-130XL with 62,000lb, 72,000lb and 80,000-85,000lb payload capacities. The C-130J's payload is around 42,000lb, while the larger Airbus A400M's is around 82,000lb (it says here).
Jim Grant, Lockheed's vp of business development for global mobility, thinks a C-130XL would be a niche product, only needed out in the 2020 timeframe to carry those 10% of battlefield loads (like FCS vehicles) that will be too big for the C-130J. And he doesn't see too much demand for a C-130XL to compete with the A400M. Instead he sees operators having a "fleet within a fleet" - say 12 Js and two or three XLs.
A driver will be the runway requirement that emerges from the STOL versus VTOL debate under way as the Air Force and Army try to merge their theater airlift requirements into JFTL. One extreme is to stick with prepared runways and use the C-5 and C-17; the other is to push for super-STOL or VTOL so unprepared strips can be used. A C-130 derivative would be somewhere between those extremes.
So Lockheed is doing studies to see how much it could do with the C-130, and how much it would need to change the C-130 to do more in terms of payload, range and STOL. Bigger wing? Bigger engines? The bigger the change, the more expensive the development, Grant cautions. Meanwhile those of us who frequent secretprojects.co.uk will know there have been previous 'Fat Herk" studies...