Expert: Ray Wilkinson - 4/14/2006

Question
I am currently stuck on a report for university.  The aim is to propose an aircraft configuration based on current designs used in the commercial industry (i.e. airbus, boeing etc)
which will be more environmentall friendly.  
Whilst i have looked into contributing polluting factors, i.e. noise and emissions etc, i really have no idea about how to actually draw and come up with a modification on any existing designs?  
Any help would be appreciated.  

Answer
Aishah

I can't help you with drawing up your design, I'm afraid, but the following may help:

'Environmentally friendly' is a wide subject. I would consider materials (recyclable, light weight, non-hazardous processes), saving weight and drag to reduce fuel burn, alternative fuels, and noise. Some of this comes down to improvements in engine technology, which is outside your brief. The rest comes from improving the design, which is. Modern airliners are extremely well optimised, but we are approaching the stage where we will see a step change in design, probably towards a belnded wing/body arranegement. This will have to be associated with new materials to make the design viable. Boeing are working on this, but it's expensive - you may find some details on their website. The problem with BWB is that you end up with a wide passenger cabin, which combines with the pressure loads to make for a difficult pressure-cabin design. Since a cylinder is an efficient pressure vessel, you can put several side by side to make the cabin. The drawback is that you want a smooth exterior surface to reduce drag, so you need an external skin on top. The alternative is to make a single, wide pressure vessel, and use lightweight materials such as composites to reinforce the fuselage against the bending loads created by a large non-cylindrical roof and floor.
The BWB layout does have other drawbacks, and a major issue with any new design is passenger evacuation - can you get enough doors to get everyone out in 90 seconds, even if the undercarriage collapses?
On the noise issue, the major problem is landing and take-off noise, which divides into two main areas - airframe noise and engine noise. Shielding the engnes from the ground can help with engine noise (and the BWB design allows this), and airframe noise can be reduced by apying attention to draggy bits like undercarriages and flaps, which generate much of the airframe noise.
I hope this helps you.

Regards, Ray.