The US Defense Science Board has just released its report on the VSTOL/STOL airlift requirements to support the US Army's concept of "mounted aerial manoeuvre" - flying a fully equipped armoured force from an intermediate land or sea base directly to the battlefield.
The report is important to two camps: the US Army backing the Joint Heavy Lift rotorcraft (left) and the US Air Force backing the AMC-X (right, aka AJACS) replacement for the C-130.
(Artwork via www.secretprojects.co.uk)
Both camps are eyeing the Army's requirement to airlift payloads of up to 30t over distances of 250-500nm, using either fixed- or rotary-wing aircraft. And the report has good news and bad news for both.
The DSB concludes that suitable aircraft, while technically possible, will be costly, risky and take a long time to field. The report says the "best single fit" is a hybrid aircraft combining rotary- and fixed-wing technology, but warns it is "likely to be very expensive".
This is good and bad for the JHL camp, which is focusing on a large tiltrotor. Good because a tiltrotor is a hybrid aircraft. Bad because the report makes clear the cost, risk and time required to build a 30t-payload VTOL lifter are inconsistent with the Army's near-term requirements.
As a result, the DSB recommends alternative concepts be explored. Specifically it believes a 20t payload and 250nm unrefuelled range is "a more achievable near-term goal for hybrid lifters". But - and it is a big but - that would require the Army to change its operational concept.
The problem is the Army's Future Combat Systems vehicles are getting heavier. They were planned to weigh 17-18t, so the original JHL studies assumed a 20t payload and C-130-sized cargo box. Now FCS vehicles are pushing 30t and JHL is growing to match. It's now A400M size. No-one has built a rotorcraft that big, no engine exists to power it, and no existing or planned ship has a deck strong to carry it.
Quad Tilt Rotor - how big can it get?
So the DSB is recommending the US Army goes back and re-examines how big a force it really needs to fly direct to the battle, whether it really needs to airlift its heaviest vehicles, and how small and austere the landing site really needs to be. Tough questions - the answers to which will be key to the future of both JHL and AMC-X.
Comments (3)
What people fail to understand is that an aircraft designed to pick up ~24 tons CAN pick up 30 tons. It may not go 250nm (without air refuel {doable}) and it may have to take off SSTOL, but it is not impossible.
The real key is that VTOL means you do not have to go to airfields that are about the most documented bits of the earth to make a mission to. A country does not have to go far to figure out where to drop artillery and render an airfield inop to airlanding. Nor do you have to worry as much about the condition of the soil after landing say 40 sorties to do a mission if you land in open terrain. In fact, if the mission calls for it, with VTOL you can land on water.
Another key is how fast you can put combat forces on the ground. You can only land one horizontally landing aircraft at a time in a field say 2,000ft in length (optimistic in extreme I suspect to fixed-wing folk). Even with a C-130-sized rotrcraft you can land (with huge saftey margins) five aircraft. In Air Force terms that means 5:1 MOG ratio rotorcraft to fixed wing.
There is more to JHL than moving 20 to 30 tons of vehicle around also. The ability to land 20+ tons of supplies directly to units in the field (not to mention moving bulk off of ships to disaster sites) may be as revolutionary as flying armor around.
I suspect that if you did a holistic analysis the cost of the VTOL platform would not be that much greater.
Posted by Anonymous | October 11, 2007 8:01 PM
Posted on October 11, 2007 20:01
The DSB report points out the JHL could carry a heavier payload by taking off vertically with reduced fuel then topping off the tanks in the cruise via aerial refuelling.
Bell Boeing at AUSA also pointed out that designing the JHL for a 6,000ft/95deg VTOL mission would enable it to carry heavier payloads at the more normal lower operating temperatures and altitudes. So 30t is doable.
The issue is cost, I think. Industry says it won't be as expensive, but I would bet we are looking at something that could cost as much as the C-17 does today. If someone wants to pay that much to fly heavy payloads into the fight, then industry can make it.
Posted by The Woracle | October 11, 2007 8:15 PM
Posted on October 11, 2007 20:15
I agree that it will not be as cheap as Industry wants to make everyone think, although I am not willing to say it will cost as much as a C-17.
However look at the "holistic" cost: if you take into account that an SSTOL aircraft will very likely never operate from ships (were much greater than 75% of logistics efforts will come from in an expeditionary environment), you will need more varied aircraft, trucks, loaders, docks, ports, etc. Let's look at a land-locked expeditionary effort. What is the cost to drive convoys down roads in Iraq and Afghanistan? How much has been invested in new vehicles, sensors, electronics, etc., to allow trucks to move the supplies from the airfield to the customer? What are the savings if you could take the supplies from the ship or a theater base directly to the customer?
While a fixed-wing aircraft may cost less to acquire, you do not reduce any of the required infrastructure (and under current warfare techniques the prime targets [i.e. convoys]). While I do not propose that a VTOL platform would solve world hunger, it does deal with many of the prime challenges faced in today's normal combat environment and reduces the number of moving parts in the supply chain.
That I think might be worth a bigger price tag.
Posted by Anonymous | October 11, 2007 8:49 PM
Posted on October 11, 2007 20:49