Eurocopter is reporting a new breakthrough in the test flight program for its X3 high-speed, long-range Hybrid Helicopter demonstrator. The aircraft is equipped with two turboshaft engines that power a five-blade main rotor system and two propellers installed on short-span fixed wings, combining the vertical takeoff and landing (VTOL) capabilities and full hover flight capabilities of a helicopter with the fast cruise speeds of a turboprop-powered aircraft. On November 29, the X3 reached the program’s Step 1 speed objective by attaining a true airspeed of 180 knots (333 km/h or 207 mph) in level flight at a reduced engine power level.

The X3 demonstrator’s maiden flight took place on September 6, 2010 in Southern France at the Istres Center of “DGA Flight Testing”, and since then the basic hybrid demonstrator aircraft’s stability and handling has been tested both with and without autopilot. It has reached an altitude of 12,500 feet (3,810 m) and performed maneuvers with left and right turns at bank angles of up to 60 degrees. With initial testing operating on reduced power, the flight envelope was progressively opened to achieve the 180 knot milestone.

The X3 has performed extremely well, demonstrating handling and flight qualities that are exactly in line with our ground-based simulator evaluations,” said Eurocopter test pilot Hervé Jammayrac. “This helicopter is really built for speed, and our test team looks forward to taking the X3 to the next steps of its flight regime.”

After a three-month upgrade the X3 is set to enter a second set of flight tests in March 2011, with the goal of reaching sustained cruise speeds in excess of 220 knots (407 km/h or 253 mph) – which, it should be noted, still falls short of the 250 knots (463 km/h or 287.69 mph) record achieved by Sikorsky Aircraft’s coaxial X2 Technology demonstrator in September this year.

The X3 is built around a Eurocopter Dauphin helicopter frame and is designed to suit a wide range of applications, including long-distance search and rescue (SAR) missions, coast guard duties, border patrol missions, passenger transportation and inter-city shuttle services. Eurocopter says it could also be well-tailored for military missions in Special Force’s operations, troop transportation, combat SAR and medical evacuation.

The Skylifter airship concept

For decades, fans of airships have been hoping for a large-scale revival of the majestic floating aircraft. Every few years, lighter than air flying concepts come along to raise those hopes, such as Northrop Grumman’s Long Endurance Multi-Intelligence Vehicle, Skyhook’s JHL-40, and DARPA’s Walrus, which led to the current Aeroscraft ML866 project. Now there’s another unique contender to the throw into the mix – Australia’s Skylifter. If it ever makes it to the skies, however, it’s sure to be the source of some bogus UFO sightings.

Purpose

Skylifter is a dirigible gas balloon system which, as its name implies, is intended for transporting cargo too heavy, bulky or fragile for conventional aircraft – its carrying capacity is rated at 150 tonnes (165 US tons). While the company’s immediate plans are for traditional payloads, down the road it would be interested in developing prefabricated buildings that Skylifter could drop into hard-to-reach locations, or luxury pod units that would take up to 80 passengers at a time on air cruises.

Design

The aircraft would consist of three main sections. Floating at the top would be the symmetrical discus aerostat, which is a fancy way of saying “saucer-shaped balloon.” It would be permanently filled with lighter-than-air gas. Hanging on suspension lines below it would be the cylindrical control pod, with the two-pilot flight deck mounted on the bottom. Cargo would hang from cables below that.

Propulsion

Biodiesel engines, augmented by solar panels on top of the balloon, would generate electricity to power three propellers mounted on the sides of the control pod. The propellers would be cycloidal, meaning that the blades would be arranged horizontally. The main advantage of such propellers would be that they could be rapidly controlled via a helicopter-style collective – this would definitely come in handy for the precise maneuvering involved in the collecting and depositing of cargo.

The airship would have an estimated cruising air speed of 45 knots (83 km/h or 52mph), and a range of at least 2,000 kilometers (1,243 miles).

Advantages

As with other lighter-than-air vehicles, Skylifter’s main bragging points are its lifting abilities, the fact that it could stay aloft for days at a time, and its relatively low fuel usage and CO2 emissions (as compared to an airplane or helicopter).

Unlike traditional blimp-shaped airships, Skylifter would have no front or rear end, meaning that keeping it turned into the wind would not be an issue, and it could easily spin 360 degrees. It also wouldn’t be limited to landing at airfields with masts, which is the case with blimps. Instead, the pod and balloon would be moored to the ground, and the balloon could be lowered down close to the pod to minimize the effects of wind – the designers estimate that it could withstand gusts of up to 148 km/h (92 mph).

So, will we ever see a Skylifter in real life? Well, the designers have already built two proof-of-concept models of the lift system, and plan to build at least two more that are bigger and better. In the meantime, here’s hoping.

Officially announced at AirVenture 2010, Sikorsky’s Project Firefly sets out to demonstrate the feasibility and showcase the benefits of electrically powered helicopters. The technology demonstrator is based on an S-300C light helicopter, with a 190-horsepower electric motor replacing the standard piston-engine and lithium ion battery packs added to either side of the cabin. The result is a significantly more efficient system that – although it’s expected to fall short of typical helicopter performance when the first flight takes place later this year – is just the tip of the iceberg for the new era of manned electric rotorcraft.

Along with the electric motor and battery packs, the demonstrator includes a new digital motor controller and next generation cockpit display. The drive train, rotors and flight controls from the S-300C have been retained and very little has been changed on the airframe, as the electric motor has been designed to pick up the same hard points as the piston engine it replaces.

The 190 hp (142 kW) motor built by Californian firm U.S. Hybrid from California is derived from a unit developed for ground based vehicles but, as Sikorsky’s Tim Lauder explained to Gizmag, it’s been specifically tailored for use in rotorcraft. These changes include an additional 40 horsepower, constant operation at 3200 RPM and forced air cooling as opposed to water cooling.

The battery pack from German manufacturer GAIA consists of 300 cells – 150 in each bay – with an energy density of 0.13 kW per kilogram.

Inside, real-time aircraft information including temperature for left and right battery packs, flight time remaining and voltage is shown on an interactive LCD monitor.

Performance and efficiency

The comparative figures Sikorsky has released for the testbed helicopter show huge improvements in efficiency. The main rotor output, for example, is 76.3 percent efficient in the electric version versus 25.5 percent for a Sikorsky 76D running two PW210S turboshaft engines on JetA fuel. The other notable comparison is heat loss, where the electrical system loses just 15 percent compared to 73.4 percent on the 76D according.

“Through the electrical conversion, propulsion efficiency of the aircraft has been increased roughly 300 percent from baseline," said Mark Miller, Vice President, Sikorsky Research & Engineering. "Electric propulsion also inherently simplifies the complexity of the propulsion system by reducing the quantity of moving parts, increasing reliability while reducing direct operating costs.”

While both the cruising speed of 79 knots and the gross weight of 2150 lbs are comparable to the S-300C helicopter, the big issue, as with electric cars, is range. The demonstrator has an expected flight time of 15 minutes (compare this to the 3.7 hrs the S-300C gets from its 32 gallons of fuel) but as battery technologies get better, this will improve exponentially.

Lauder sees lithium air batteries as one of the most promising of these developing technologies. "Lithium air batteries would be lighter (because they have no anode) and provide nine times the energy density of the current batteries, enabling three hour flights and rivaling combustion engines."

The problem at this stage is that these batteries are non-rechargeable, but research and development of rechargeable versions is ongoing.

It’s safe to say that the future for electric helicopters is bright. As battery technology matures the value of the systems showcased on Sikorsky’s testbed can only increase. Although the company has chosen to use an existing airframe to showcase the technology at this early stage of development, it is already looking towards ground-up designs that will run two electric motors – one in the main rotor and another in the tail rotor. This approach, like electric car designs that place motors at or in each wheel, will further reduce weight and improve efficiency by bypassing the need for any conventional drivetrain.

Sikorsky electric helicopter specifications

Max Gross weight – 2,150 lb

Power 190 hp (142 kW) Permanent Magnet electric motor

Lithium Ion Battery – 45 Ah, 3.6 V, 3 cells in Parallel = 135 Ah, 100 set in series = 360 V

Forced Air Cooling

Endurance – 15 min

Max Velocity – 79 kt

System Efficiency – 79 % (Cruise), 91 % (Max Power efficiency)

The Puffin in full flight … electric motors deliver a top speed of around 150mph and a range of 50 miles – plenty for that daily journey to work and back!

Be honest. Who hasn’t dreamed about flying in their own personal aircraft? NASA aerospace engineer Mark Moore moved his dreams one step closer to reality by devising this concept – the Puffin personal air vehicle. It’s a vertical take-off and landing tail-sitter that has generated quite a lot of interest from those inside and outside of NASA. It’s definitely a weird-looking craft, with a tail that splits into four "legs" that serve as landing gear. It lifts off like a helicopter, hovers, and then leans forward to fly horizontally with the pilot lying down like in a hang-glider.

The Puffin, if ever built, would be an electric-powered, 12-ft (3.7m) long, 14.5-ft (4.4m) wingspan personal air vehicle. It evolved as part of Moore’s coursework for his doctoral degree. NASA then paid for much of the research to devise how the Puffin could actually fly. Moore is a nationally recognized expert on personal air vehicles and other small aircraft systems.

The proposed aircraft would be small and very lightweight – about 300lbs (136kg) empty weight, plus another 100lbs (45kg) of battery and 200lbs (91kg) for the pilot or payload. To get off the ground, the Puffin would be propelled by 60hp of electric motors, designed to still be able to produce the required power to hover even if any two of the powertrain components on either side failed.

To take in the views on offer (or complete a mission), the Puffin would have a top speed of 150mph (241kph), but could cruise more efficiently at lower speeds. Current battery technology dictates the range would be around 50 miles (80km) before the Puffin would be looking for a safe place to land.

Why is it called Puffin? "If you’ve ever seen a puffin on the ground, it looks very awkward, with wings too small to fly, and that’s exactly what our vehicle looks like," Moore told Scientific American.

Moore adds that the puffin is known as an environmentally-friendly bird, because it hides its poop, and the vehicle is environmentally-friendly because it essentially has no emissions. Also, puffins tend to live in solitude and this is a one-person vehicle.

The National Institute of Aerospace hopes to fly a remote control one-third size model to test whether Moore’s academic studies are right, and in particular, if the Puffin can move from hover mode to forward flight.