More robots are going to war. In this case Afghanistan, which is where the Lockheed Martin-Kaman unmanned K-MAX helicopter is heading for a six month trial with the Marines after completing the Navy’s Quick Reaction Assessment. I’ve always loved Kaman’s funky intermeshing rotor design. There really haven’t been a lot of helicopters that use it. Most helicopters use the traditional layout of a single main rotor and an anti-torque tail rotor. The tail rotor is needed due to physics – fighting the equal and opposite reaction. When you spin the main rotor in one direction the fuselage wants to spin in the other. But the tail rotor doesn’t contribute to lift at all, and the power it uses is ‘lost’.

You can avoid this loss by having two counter-rotating main rotors. The torque is cancelled out, and all of the power can be used for lift. The most common system is tandem rotors, best known on the heavy lift Boeing Vertol CH-47 Chinook and the smaller CH-46 Sea Knight, and it was mainly pioneered by Piasecki before that. This system is only used on larger helicopters as you need to space the rotor hubs at least as far apart as half the diameter of the rotor disk. This has almost always been done fore-and-aft, though there have been a few oddball designs with rotors on outriggers on each side.

The other common approach is coaxial rotors. One shaft passing through the other, which is hollow. The two rotor discs are stacked one above the other. This isn’t as efficient in lift as tandem rotors, as there is more interaction between the two rotor discs. (In tandem layouts they only overlap for less than half of each disc with the arc from one disc crossing the arc of the other.) But it allows the system to be used on smaller helicopters as there is no need to separate the two discs. There haven’t been too many western designs using coaxial rotors, but Russia’s Kamov has had a long line of naval helicopters with coaxial rotors. They’re especially well suited to naval operations as the lack of a tail rotor means they don’t need a tail boom, and so can be more compact for deck operations. Coaxial rotors are seeing a resurgence due to another advantage – higher speeds.

But intermeshing rotors are rare. I think there have really only been four helicopters that used them. During WWII Germany had two early helicopter designs using intermeshing rotors. And then Kaman had their HH-43 Husky which was used from the 50s to the 70s, but intermeshing rotors languished until the K-MAX was developed. The K-MAX was aimed at commercial external lift operations such as helicopter logging and construction, but it struggled, competing in price with used helicopters, and only 38 were built. But now it may get a new lease on life, and further production. Lockheed Martin selected the K-MAX as the airframe for their unmanned, or optionally manned, aerial resupply system for the military. It is all about carrying heavy loads to forward operating bases and troops, and carrying heavy loads is the K-MAX’s forte.

The K-MAX is all work, with form following function. It is basically engines, rotors, fuel, and a one-person cockpit. It was designed from the ground up around carrying heavy external loads, so the hook is directly below the rotor mast and the fuselage is reinforced to carry the load through. The slim, minimalist body saves weight – which translates into more payload capacity. And the intermeshing rotors mean more power for lift, and better hot & high operating capabilities – which should be useful in the mountains of Afghanistan. Lockheed’s modifications give the K-MAX completely autonomous capabilities, flying supplies out to remote bases and returning without human intervention. The only human involvement is hooking up the load at the departure and programming the route – it can drop the load autonomously. If the field trial goes well there’s a chance the K-MAX will go back into production, this time for the military.

Note that in the videos you’ll see operators with controllers. The K-MAX can be remotely operated if necessary, such as for fine control in picking up a load or setting something into place when precision is required, but it is not normally remotely operated throughout all phases of flight. It also retains the cockpit and is optionally manned, which means it can be flown by a human if the mission requires it. Or for things like transitioning civilian airspace where unmanned vehicles are generally not permitted due to ‘see and avoid’ operational rules.

It is a pretty impressive system, and the hope is that it will be able to replace today’s system of truck convoys which are susceptible to ambush and IEDs. And that’s when they can even traverse the rough terrain. The K-MAX can deliver supplies night & day, in all weather, without putting so much as a single pilot at risk. I think it is a pretty cool gizmo. Check out the latest video:

Here’s some more videos, after the cut:
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