Technologies that might still make it...

1 Diesel engine

The standard general aviation piston engine delivers a pedestrian 30hp or so per litre, via antiquated technology and obsolete avgas fuel. Its only merits are that it is more reliable than frantic microlight engines, and most bush mechanics know how to change a cylinder on one. It is as if engine development stopped in 1939.

The new-generation diesels are mostly small, light, high-revving and economical (none of which accusations could be levelled at the 1930s Junkers Jumo vertically opposed two-stroke). These were at least better than the lamentable Beardmore Tornados whose excess weight contributed so much to the R101 airship's inability to manoeuvre out of trouble in 1931. Modern diesels are so good that it would be staggering if a conventional avgas-fuelled piston GA engine is still being offered by the end of this decade.2 Tiltrotor

After several shaky starts going all the way back to the late 1940s, it looks like a tiltrotor might actually enter service in the near future. It has not been an easy road - the Bell Boeing V-22 project, for example, has been dogged with political and technical problems.

But the Bell/Agusta 609 civil tiltrotor is now flying. Other proposed designs would allow the aircraft to land or take off in conventional aircraft mode, too. This is one with a bright future.

3 Hypersonic flight

Despite the demise of Concorde, there is still the enduring dream of very long-distance, high-speed travel. The next versions of the Airbus A340 and Boeing 747 might promise UK-Australia non-stop, but does anybody want to spend over 20h doing that?

The dream of doing it sub-orbitally instead has been there for a very long time (the British HOTOL from 30 years ago was the last halfway-credible embodiment of it), but the affordable technology has not. Perhaps the new-generation air-breathing scramjet engines will do it, but who will pay for it?

4 Flying car

The Aerocar was conceived in the 1940s, California's Moller International is still at it today. But a flying car is always going to be a compromise that does nothing as well as its non-hybrid parents do. The Aerocar, uniquely, was a bad car, and a bad aircraft. The trouble is that aviation and automobile legislation are largely incompatible - but perhaps somebody out there can still satisfy both sets of legislators - and a few customers.

5) The truly personal jet

Yet another of the great aviation dreams. Maybe the Lear 23 came closest, but since then customers have wanted more performance, range and space, and the regulators have demanded so much more as well. There have been hundreds of such projects, but they are almost always under-funded, and there never is order-of-magnitude cheaper technology.

What is needed is the ability to stamp out a fully Federal Aviation Administration/Joint Aviation Authorities-compliant structure like they do a modern car, and to fill it with Japanese-style integrated systems.

6 Unducted fan and propfan

Remember the GE36, buzz-sawing its way around the air show circuit in the early 1990s on the back of an MD-80? Or the so-nearly successful Antonov An-70? They may be much more efficient than turbofans, but even the worst fuel price rises so far have failed to scare the airlines into demanding a much more efficient propulsion system. Nor has the ever-tightening noose of environmental legislation. So far, it is just a clever technology with a too-high cost/benefit ratio.

7 Airship

Santos Dumont was flying around quite happily in his airship well before the Wrights flew. The Germans were running long-distance bombing raids with Zeppelins long before the British could respond with their big Handley Pages, and they did it again with long-endurance intelligence-gathering flights early in the Second World War. It was an airship (R-34) that first crossed the Atlantic non-stop, and an airship which operated the first non-stop transatlantic air services.

But the conventional aircraft has always caught up and overtaken the airship in every aspect except comfort and endurance.

8 Large composite structures

So far there are complete composite fuselages on Hawker business jets and small helicopters, along with Airbus tailfins and now metal-composite skins on the A380, and composite wings on military aircraft. The next big breakthrough will be on the Boeing 7E7, which will have a composite fuselage and wings but relatively conventional aerodynamics and controls. But processing structures of this size and complexity in composite materials is no lightweight matter.

9 Blended body

This should be the way forward, giving stronger, lighter structures with better aerodynamics, and interior space more suited to the needs of the passenger than to the needs of the stress analyst.

That is why every manufacturer's glossy brochures are full of blended-body proposals. But with the exception of weird and wonderful things such as Northrop's B-2 (the most expensive aircraft ever to go into production and service), they never come to fruition. We always seem to end up with wings halfway down a tubular fuselage and conventional tail surfaces. Who will be brave enough to do it on a mainstream aircraft?

10 Adaptive wing

Almost back to the future: the Wrights' principles of aerodynamics are still with us. We still control aircraft through differential lift and drag, but by sticking big discrete panels out into the airflow, rather than by bending, twisting and reshaping the whole wing. But the work now going on, with the materials like composites that are now available, is slowly bringing us back to the dream that man has had since the middle ages - using birdlike technology to really fly like a bird.

Source: Flight International