Stealth helicopters on the horizon?

Interesting concept:

A Russian company announced its intention to build a next-generation helicopter capable of taking on fighter jets, soaring at up to 370 mph — and remaining invisible thanks to its ability to cloak itself from radar.

Vertolety Rossii (or “Russian Helicopter,” one of the country’s biggest helicopter manufactures) told the Russian press that his company would spend $1 billion on a project to develop a so-called fifth-generation radar-invisible copter. At the press conference in which the plans were unveiled, the company did not provide details on the futuristic vehicle.

I can imagine they didn’t. Other Russian sources said that such an aircraft would need to be near-invisible to radar, have an extended flying range (relative to other helos, that is), have a weapons control system that applies expert systems/intelligence, and have a top speed up toward 370 mph. Weapons control shouldn’t be too much of a problem, at least not any more so that any other aircraft. Some of the other ones are going to be a little tougher.

Helicopters are rotor-wing aircraft, meaning that their primary lift is from a spinning “propeller” called a rotor. As the helo begins to move, the airflow passing across the plane of the spinning rotor will actually produce lift much as a fixed-wing aircraft does. This is called “translational lift“. However, even though the rotor begins to act like a fixed wing and imparts a bit of the same feel as a fixed wing, it is most certainly not one. The rotor spins at a given speed and the tip of the rotor, as it passes from the nose back toward the tail, will actually slow down, relative to a fixed position in space, as it makes that “backward” trip. As the helo itself speeds up, there will come a point in time where the tip of the rotor blade will actually come to a standstill in space, effectively coming to a halt as the helo passes by. When that happens, that blade will no longer produce lift, effectively dropping 1 side of the helicopter out of the sky. That’s definitely in the Bad Thing™ category so it’s something that limits the top speed of a helicopter. Yes, it’s a matter of getting an engine that can spin the rotor fast enough to maintain stable lift, but it’s also a matter of building a rotor that can withstand that kind of force. The current speed record for a helicopter is 249 mph by a Westland Lynx. A Sikorsky design – the X2 – shows promise to have a top speed of 288 mph but hasn’t done so yet. We’re a long way from 370 mph.

The other issue is radar visibility. Great efforts have been made in stealth fighter design to hide the jet turbines from direct observation because those spinning blades make for a huge radar return. The blade on a helicopter is, of necessity, not only exposed but many multiples of times larger than a jet engine turbine. Given that they must be shaped in such as way as to provide vertical lift, there’s limits to what can be done to change the rotor’s position, size, and blade cross-section. With the current level of technology, I’m unsure how they could manage to reliably deflect radar energy away. Perhaps they can absorb it but that would require materials capable of far better absorption than is available today.

Could be a cloaking device, capable of electronically disrupting the radar, of course. You’ll pardon me if I don’t hold my breath on that one.

Anyway, should be interesting to see what they come up with.