I'd say that chances of the tube+wings airliner shape, so successfully established in the jet age by the 707, are maybe evens, at best, to pretty
Among the reasons for this are the issue surrounding evacuation times, as raised already in the 797 thread, there is also an elegant simplicity to the
layout which explains why you can buy an A340 today that looks pretty similar in general arrangement to the 707 of half a century earlier. Go back a
further half century and you are into Wright Brothers territory!
Having the engines hung under the wings on pylons is known to be less favourable than the rear mounted layout which was pioneered by France with its
Caravelle. This layout was openly mocked when the Caravelle was first revealed, yet it was quickly copied by the UK, with the BAC One Eleven, and
America, with the DC-9.
The advantages of rear mounted engines include a reduced likliehood of FOD, a quieter passenger cabin and a more aerodynamically efficient wing.
Despite that last one, when Boeing designed the 787 they STILL opted to mount the engines under the wings, even though its raison d’etre is
Disadvantages are mainly centred around engineering and maintainance reasons with the engines being more inaccessible than ones close to the ground.
Another disadvantage is the deep stall problem associated with mounting the tailplane at the top of the fin, however this was a self inflicted one by
the British and American designers of rear engined aircraft, it was not something that the Caravelle suffered from with is cruciform tail of similar
design to the Hawker Hunter.
Interestingly ALL the advantages and disadvantages mentioned above also apply to the Boeing and Airbus BWB designs. If the layout has been disowned by
designers of conventional airliners why should it be any different for these two marvellous new concepts? As far as I am aware the only new airliner
designed with rear engines is the Tu 334.
Here are some examples of advanced concepts for conventional (ie non SST) airliners;
It is quite unlikely that any of them will ever appear, but it illustrates the sort of ideas being bandied about to try and find that elusive design
Airbus Flying Wing
Both these designs, although different in detail, explore essentially identical concepts and are both aimed at accommodating around 1,000 passengers.
Airbus considers this a potential replacement for the A380 in 20 or so years time, though this decision would clearly be influenced by what Boeing
does with theirs.
In both designs the wing and fuselage are combined into a single, light weight, efficient structure. If a clean airflow can be achieved then
radically reduced fuel consumption is the prize that awaits.
A drawback, however, is the limited scope for modification of a flying wing from a technical viewpoint: whereas a conventional aircraft type can
simply be "stretched", it is likely that every model of a flying wing aircraft, and every size of every model, would require a dedicated design,
with the associated cost implications. Due to the complex structure, it would not be possible to insert or remove segments of the fuselage
Airbus Joined Wing
The aerodynamics of this concept are said to be particularly complex. It is of course very much reminiscent of an advanced tanker concept that was
designed by Lockheed at around the same time. Lest anyone think that Airbus merely copied Lockheed, it should be noted that this wing concept has been
around since the 1930’s.
The primary objective of this concept is to achieve a significant reduction in the size and structural weight of the wing. The design would only need
a very short span, which would be advantageous when manoeuvring on the ground. The joined wing would inevitably generate more drag than a conventional
wing however, but the aim of the study was to see if all the other advantages could overcome this and result in an overall increased fuel
Also, the raised upper fuselage line is aimed purely at reducing interference between the wings but it could also provide space for hydrogen fuels if
such development should ever bear fruit.
Airbus ‘Three Surface Layout’
Essentially this concept equates to a canard equipped A340, though if produced its actual design would have be at least as efficient and advanced as
the 787 of course. This design is said to be naturally unstable and with it Airbus was attempting to save weight by reducing the size of the rear
stabiliser. It is also considered that its various tr8imming possibilities will result in improved cruise efficiency and thus reduced fuel burn.
Another consideration is that for further developed stretch of high gross weight versions the overall lift can be increased by enlarging the canard
surfaces rather than increasing the wingspan.
Note also how both preceding designs still use wing mounted underslung engines despite the quest for low noise and low fuel burn that inspired
Despite all of the above it is my belief that there will be no commercial launch for any of the concepts we have seen here and the best they can hope
for is that these concepts lead to technological advances that can be built into aircraft which outwardly look just the same as jetliners always have,
just like is happening now with the 787.
[edit on 25-4-2006 by waynos]