Flight of fancy?

7 min read

As NASA prepares to trial its Small Aircraft Transportation System, is this the first step towards the Hollywood vision of 'flying cars' and 'highways in the sky'?

In a few months' time a small regional airport in the US will host an event that may one day be viewed as one of the most significant milestones in aviation history. From 5 to 7 June engineers, scientists and members of the public will gather at Danville Airfield in Virginia to witness a demonstration of NASA's Small Aircraft Transportation System (SATS).

With the media spotlight currently focused on the vast proportions of the Airbus A380, the five-year, $69m (£37m) SATS project has a very different vision of aviation's future — a future in which people use small, low-cost single-pilot jets to fly in and out of tiny, untowered airfields.

The SATS team, led by NASA but with input from the Federal Aviation Administration (FAA) and National Consortium for Aviation Mobility (NCAM), set out to develop some of the key technologies required for a 'highway in the sky' system.

In the longer term many believe that SATS could even provide the infrastructure for that stalwart of many a post-war futuristic vision and Hollywood movie: flying cars.

SATS manager Jerry Hefner, of NASA's Langley Research Centre, said that with 93 per cent of people in the US living within 30 minutes of underused rural airports, a huge national asset is currently not being exploited to the full.

While such systems have been suggested in the past — Richard Noble's Farnborough F1 project in the UK springs to mind — Hefner believes that SATS has done enough to show that they are practical.

One of the capabilities that will be demonstrated at Danville is the use of finely tuned GPS technology to enable plane-to-plane communication. Hefner explained that GPS-based systems that link to enhanced cockpit displays showing the precise location of every aircraft will remove the need for expensive ground-based equipment and enable large numbers of planes to operate safely around a small airport.

Hefner said that, coupled with a system that enables a pilot to follow predetermined flight-paths on a display screen, SATS also makes it possible for one pilot to operate as safely as two.

What's more, the project has developed technology to make landing in bad weather easier. Enhanced vision systems borrowed from the military can cut through fog using infrared andlow-light cameras and, using advanced cockpit display technology, give a pilot clear perspective of the surrounding airspace.

Hefner is effusive over the advantages of replacing traditional 'hub-and-spoke' air travel with a point-to-point system, an enthusiasm borne out of personal experience. As a senior NASA manager he's used to dodging about the country in the agency's fleet of private jets: 'You don't have to do that more than once or twice to appreciate the advantages. It reduces the hassle and saves time.'

June will see the SATS system tested on a number of NASA's own aircraft and those of external companies interested in the technology. Further research funding is yet to be announced, but Hefner is confident that while the demo may mark the end of the SATS project, it will provide a springboard for the SATS vision. 'Our successes will command that we do follow-on work,' he said. These additional projects are likely to focus on cost reduction, improved safety and security, and improving single pilot performance to a point that is acceptable to the insurance industry as well as the FAA.

Hefner pointed to political expediency as a further cause for optimism. 'SATS can bring air travel to communities that have never had air travel before. This can bring in business and create jobs, and if you're a congressman in that area it's good for you. You could very easily get all states to support and back SATS technologies.'There is also said to be a high level of interest from a number of aerospace companies, for whom the project potentially represents a significant commercial opportunity. These companies, which Hefner refers to as 'biz-jet dotcoms', are typically involved in the development of exactly the kind of small, fuel-efficient jets or turboprop-engine planes that are suited to a SATS environment.

Perhaps chief among these is the $1.2m Eclipse 500 vlj (very light jet), a single-pilot twin-engine jet that carries six passengers, cruises at 430mph and can take off and land in less than 1,000m. The aircraft's manufacturer, Eclipse Aviation of Alburquerque, recently began flight-testing and expects to deliver to customers late next year.

An even shorter take-off and landing distance is proposed by UK company Avcen with its Jetpod concept. Avcen, which hopes to have an aircraft ready for trials in around 18 months, claimed that its twin-jet plane will be capable of taking off and landing within 125m, enabling it to use tiny landing strips in city centres.

With the right support, Hefner believes that SATS could begin transforming air travel within the next few years, initially within the US, but ultimately across the UK and the rest of Europe. But if this prospect isn't tantalising enough, the longer-term vision is truly mouthwatering for many in the aerospace industry, Hefner included. This is that SATS is paving the way era of the flying car.

Enter NASA's Personal Air Vehicle (PAV) project, an initiative that, while distinct from SATS, is keeping a watchful eye on its progress. Andy Hahn who works on the project, said that though the vehicles envisaged by SATS are only 'personal' (if you can afford $1-2m (£500,000-1m, the PAV project is looking at day-to-day flight for all.

Perhaps unsurprisingly, Hahn is weary of the term 'flying car'. He said that the idea of vehicles driving along motorways and taking off as soon as they hit a traffic jam is unrealistic and misleading.

Instead, he prefers to talk about personal aircraft that are 'roadable' — short take-off and landing vehicles that trundle down the road to the nearest playing field and take off from there. 'You could start out in your driveway and waddle your way down to the baseball field, maybe a quarter of mile away, where you would take off and fly at 160mph, eventually landing very close to your final destination.'

Hahn and his colleagues are investigating a range of technologies and concepts that could lead to the next generation of personal air vehicles, and over the next five years will help determine the destination of $32m (£17m) worth of investment to research promising technologies.

Clearly, to make personal flight truly democratic, much of the effort and cost involved in learning to fly must be removed. Hahn dismissed autonomous air vehicles as a solution: 'I wouldn't put a bag of groceries in one, let alone my daughter.' Instead, he believes that a semi-autonomous system allowing limited pilot control will be the safest option.

To this end, $24m (£13m) of PAV funding is being put into HAPTIC, a flight control system under development by Ken Goodrich, a senior research engineer at the Langley Research Centre. Hahn explained that this system is also referred to as the 'h-mode' because its use is analogous to riding a horse. 'When you ride a horse you don't tell it where to put each hoof, and if you tried to ride off a cliff it wouldn't jump. The same thing would happen with the h-mode. It will figure out your intent and if you have a course set in, it will tend to follow the course.'

As well as relieving pilots of much of the skill-based flying that requires so much training, a HAPTIC system would also be key in allaying the inevitable fear of groups of terrorists taking to the skies in personal air vehicles by preventing people from deliberately crashing. Hahn said that although a full HAPTIC system hasn't yet been assembled, much of the actuator and sensor technology required is currently used by the military on UAVs.

The PAV team has drawn up concept plans for a whole range of exotic-looking vehicles, but one of its first goals is to develop what Hahn called a 'transitional' craft. This vehicle, known as EQuiPT (Easy-to-use Quiet Personal Transportation), will look like a conventional plane, but cost around $150,000 (£80,000) and feature technology destined for more advanced personal air vehicles.

Within the next five years Hahn hopes to have an EQuiPT demonstrator featuring Goodrich's HAPTIC control system as well as 'enhanced roadability features' such as folding wings. As for when these vehicles take to the skies, Hahn's estimates are conservative. 'It's a chicken and egg scenario. No-one's going to build the infrastructure unless it's needed and no-one's going to have the planes to go into the infrastructure if it doesn't exist. I think it will be at least 25 years.

'But while the PAV project is still largely theoretical, Moller International, based in Davis, California, has actually built a flying car and the firm is itching to take it to the skies. The M400 Skycar, a 'roadable' vertical take-off and landing vehicle designed to carry four passengers for 900 miles at over 300mph, is the brainchild of Paul Moller, an aeronautical engineer who has perhaps harboured the flying car dream for longer than anyone else.

The vehicle features eight high-performance rotary engines, attached to fans and housed within each of the four nacelles. These nacelles are mounted horizontally and a thrust deflection system is used to ease the transition from hover mode to forward flight. Thrust generated by the fans is deflected downward by vanes at the rear of each nacelle.

Moller agreed with Hahn that the SATS project is an important stepping stone to the vision of personal air vehicles, although unlike his fellow researcher he believes it would be dangerous to have anything other than fully autonomous vehicles. 'If pilots are going to be involved we're never going to be talking about a highway in the sky for the average individual.'

The M400 is effectively ready to fly, the electronic systems necessary for autonomous operation are in place and during the next few months it will be fitted with new high-powered engines that will enable it to undergo untethered manned flight tests for the first time. These tests will be carried out above a specially built lake at the company's California headquarters.

But while the Skycar may be ready, Moller claimed that a centralised aerial highway system capable of handling even relatively small numbers of vehicles is still on the drawing board. He said that the key to establishing the control and accuracy required will be WAAS (Wide Area Augmentation System) and LAAS (Local Area Augmentation System), two systems based on geo-stationery satellites that improve the accuracy of GPS to a point where it meets the exacting demands of the FAA. WAAS has recently been approved by the FAA, while LAAS is now being developed by Honeywell.

Despite the work that still needs to be done, and in contrast to Hahn's conservative estimates, Moller believes that personal air transport will happen sooner rather than later. He feels that it will become a reality because we will have no other choice when the current road system grinds to a standstill. Governments will be left with no alternative but to fast-track implementation of a highway in the sky. Road building, he claimed, is not an option. 'The Department of Transport can tell you that the high cost of building new roads, coupled with the fact that almost as soon as a road is built it's overpopulated, means that there's no intention of building any more highways. With traffic growing at 30 per cent every 10 years, it's not hard to see that this is a terminal situation.

'Within five years many highways are going to be virtually useless, and there's going to be a time when you can't get products around. Most products are shipped around the US by truck, and if the trucks can't move you don't eat.'

He suggested that at this point Congress will be forced to do something. In the meantime, we must wait to see what becomes of SATS. If further funding comes along, personal air vehicles may not befar behind.

As he prepares to demonstrate the fruits of his research, SATS' Hefner is full of optimism. 'This is an exciting time for future engineers, who will take traditional aeronautical pursuits and integrate them with AI, nanotechnology and robotics.

'I believe the 21st century will be known as the century for personal air transportation, and people will look back and see that SATS led to that.'