Hybrid Air Vehicles Aim For A Buoyant Future

 - July 15, 2014, 2:30 AM
After being packed and shipped to the UK, the Airlander 10, formerly known as the LEMV was air-inflated at Cardington in February of this year. One of the engine ducts can just been seen at left. The engines and tailfins were not yet attached.

The two huge hangars at Cardington airfield, 50 miles north of London, stand as witness to the golden age of the airships in the 1930s. Inside one of them, a successor to those giants of the sky is being prepared for flight. British company Hybrid Air Vehicles (HAV) is pursuing the goal held by so many proponents of lighter-than-air (LTA) and related technology for so many years. The goal of revolutionizing the air cargo market–and maybe also the persistent surveillance market–with buoyant lift.

In fact, this successor has already flown–just once. It is the former long-endurance multi-intelligence vehicle (LEMV) that Northrop Grumman (NG) was developing for the U.S. Army. HAV was the main subcontractor to NG on the LEMV, providing the non-rigid air vehicle design and structure.

The LEMV flew in August 2012 at Lakehurst, New Jersey, ten months later than promised and seven months after it was supposed to deploy to Afghanistan for an operational trial. These delays, and U.S. defense budget cuts, led to cancellation of the LEMV in February 2013. The Army had spent $297 million on the project.

HAV was able to purchase the deflated air vehicle for $301,000, gain an export license and ship it to the UK. Early this year, the company re-inflated the 300-foot long, 80-foot-high envelope with pressurized air.

The company’s aim is to complete the full reassembly, inflation with helium and first flight in the UK in the first quarter of next year. HAV now calls this vehicle the Airlander 10, indicating a payload of 10 metric tons. It will serve as the proof-of-concept for the Airlander 50, which will be 2.7 times larger by envelope volume. HAV says this vehicle “will revolutionize the air cargo transportation market enabling–for the first time ever–a truly point-to-point 50-[metric ton] cargo carrying capability that can operate with limited infrastructure and support.”

HAV claims a team that has more than 1,000 years of combined experience in building and certifying LTA aircraft (see box, “Roger Munk, R.I.P”). Since Munk’s death, new directors and executives have been appointed. They include chief executive officer Stephen McGlennan, who was formerly HAV’s legal advisor; technical director Mike Durham, who has worked on LTA projects for HAV and its predecessor companies for 25 years; and non-executive director Sam Macleod, a former RAF officer who led Goodrich’s UK-based surveillance and reconnaissance business for some years.

In a hybrid air vehicle, about 60 percent of the lift is aerostatic (from helium buoyancy) and 40 percent is aerodynamic (from the vehicle’s shape). During takeoff and landing, powered lift is also employed by vectoring the thrust from four ducted propulsors. In the case of the Airlander 10, these are four 350-hp turbocharged diesel engines.

The vehicle lands and rests on two pneumatic tubes-cum-skids on the underside of the two outer hulls that retract by suction during flight for a cleaner aerodynamic shape. The scaled-up Airlander 50 will be powered by four 2,350-shp turboshaft engines, and have a different, air-cushioned landing system (ACLS). It is essentially similar to that found on a hovercraft.

Better than an Airship?

The cost-per-ton mile of a hybrid lies somewhere between that of a ship and that of a conventional aircraft. But the key attractions of the design are its scalability; its endurance; and its ability to serve austere and remote locations. Unlike an airship, the Airlander has little need of a network of large mooring masts, or winch-and-cable devices.

The endurance characteristic of the hybrid led to the U.S. Army’s interest in the design as an ISR platform. The LEMV was supposed to stay airborne for 21 days in its unmanned configuration, at altitudes up to 22,000 feet. The payload was to be a mix of sensors including radar, SIGINT and full-motion video.

Not everyone in the LTA world buys into the hybrid’s potential. A technical paper for the American Institute of Aeronautics and Astronautics (AIAA) in 2010 concluded that conventional ellipsoidal airships were better-suited to long-endurance missions than lifting-body hybrids. The author claimed that most previous literature supported his conclusion. The paper was used in support of an alternative to the LEMV that was sponsored by the U.S. Air Force. This project, called Blue Devil 2, would have produced the biggest conventional airship since the 1960s. But like the LEMV, Blue Devil 2 also fell behind schedule and never made it to Afghanistan. It was cancelled by the air force in May 2012 before it could fly.

The U.S. Army referred to “technical and performance challenges” in the LEMV project. The U.S. Government Accountability Office (GAO) reported that the vehicle was 12,000 pounds overweight, reducing the endurance to only four to five days (although 16 days could still be achieved if the LEMV flew at 16,000 feet instead of 20,000 feet). In its defense, HAV points to what was–in retrospect–an unrealistic schedule. There was not enough time to correct the weight growth on the first vehicle; the planned second and third LEMVs would have met the program’s goal for endurance, HAV’s Durham told AIN.

According to Durham, the LEMV reached 3,000 feet and flew for 90 minutes on that first flight at Lakehurst. It was flown by HAV’s own test pilot, David Burns, a British airship veteran with 9,000 LTA hours. The LEMV would have flown again three or four weeks later, but the U.S. Army reduced the number of inspectors overseeing the program from 30 to six, which slowed progress, Durham added.

“Even in modern times, there is no real software or CAD program to predict the response and aerodynamic coefficients of a lifting body,” one experienced airship pilot and consultant, who favors hybrids, told AIN. “Wind tunnels do not produce sensible results, even for normal airships. The only method that produces reliable results is the one used by the late Roger Munk and his team,” he added.

HAV has made a “modest” profit in some of its six years’ existence. AIN understands that the British company was paid about $90 million for its contribution to the LEMV–less than a third of the total expensed by the U.S. government. HAV claims to be well-funded, with a strong and stable shareholder base. Investors include Bruce Dickinson, co-owner of Cardiff Aviation, an MRO and training company. He is better known as the lead singer of Iron Maiden, a rock group. “I put in £250,000 via the Enterprise Investment Scheme,” Dickinson revealed earlier this year. “It’s a leap of faith–but this thing seizes the imagination!”

British Support

The British government has given HAV a vote of confidence. The Technology Strategy Board granted the company £2.5 million to develop specific engineering aspects of the hybrid. “Here is a British SME that has the potential to lead the world in its field,” commented the government’s Business Secretary, Vince Cable. The grant is conditional on HAV raising £1.5 million in matching funds. No easy task, perhaps, when the past has been littered with airship company failures, both in the UK and abroad.

At the height of the LEMV subcontract, HAV employed some 100 people, but that has now dropped to the current 20 full-time employees, plus consultants and contractors.

The government money is going toward development of the Airlander 50–HAV hopes to fly it in early 2017 and deliver it a year later. But with no current revenue stream, HAV must proceed cautiously. The company can’t afford to build the Airlander 50 without a launch customer. And it must first fly, prove and certify the smaller–but still very big–Airlander 10.

Certification Challenge

How do you certify a hybrid air vehicle? McGlennan told AIN that the Airlander 10 will meet British Civil Airworthiness Requirements Section B. HAV envisions a five-month flight test program before demonstration flights can take place. The company will then seek an EASA type certificate for both the Airlander 10 and the Airlander 50. It has already submitted documentation in support of the latter.

McGlennan admitted to AIN that although a European standard for large airships exists (numbered CS30T), mutual discussions would be necessary to define a new certification and regulatory framework. “There’s a strong desire to make progress. We are very environmentally friendly–and that’s one of EASA’s imperatives,” he noted.

Although the company’s focus has shifted toward civil operators, HAV directors told AIN that they still believe a customer in the surveillance market will emerge–perhaps a para-public operator. The Airlander 10 (ex-LEMV) is sized for this. HAV told AIN it might build a second one of these before embarking on the Airlander 50. The UK Ministry of Defence is showing considerable interest, the company claims. Two weeks ago, [on July 3] HAV hosted defense procurement minister Philip Dunne for lunch at Cardington.

The larger Airlander 50 will be more attractive for remote cargo transport. In August 2011 HAV announced that Canadian aviation operator Discovery Air was its commercial launch customer. “We believe this capability will enable economic development of remote, stranded resources with a low environmental impact,” Discovery Air said. But McGlennan now says that HAV has identified a different potential lead customer for the cargo-carrying version. [Rival hybrid airship builder Lockheed Martin also announced a Canadian tie-up that seems to have lapsed (see box “The Road Not Needed–By The Skunk Works”).]