You are right offcourse, my mistake, 1/2*1/2*1/2 = 1/8

However, wouldn't that mean austins reasoning is even more true?
The shrunk smaller acft will have a higher "density" than the larger one...

So, a smaller aircraft has
- Larger relative weight
- More drag
- Less efficient engines (lower BR)
- Less airspeed (for the same relative thrust)

xpm

Research

Wing warping was abandoned early on. Why did NASA recently modify an F-18 with warping wings to investigate the domain? Lunacy? Doubtful. It is arguable that the agency is looking for money, but are we that cynical? I'm not convinced that tri jets are done. ETOPS is not bulletproof, for example. By waiver, ESOPS is allowed. (Extended range, single engine).

bear

@Mad,

When I was a student (not exactly yesterday...) we had sheets and sheets of 'parametric charts', with for instance, in this context, things like 'length vs weight' etc. etc. for dozens of widely different types of aircraft.
Some were really just 'scatter' charts with some effort at finding a trend, some were very interesting.
Probably mostly composed by student assistants with time to spare and a library at their disposal.

Do they still exist, are they still used as teaching tools, and are some of them on the 'net somewhere?

raptorva might like to see some of them.

CJ

Such charts certainly exist; such parametric studies usually form the basis fort initial designs at the very early stages, before people start to spend serious amounts of money. But they are rather closely held trade secrets obviously (at least the ones OEMs have developed)

The problem with using these parametric methods for a more modern design is that they depend greatly on a large enough set of data to make the parameterization valid. As aircraft programmes have got fewer with each generation, there's less and less data to work with. But they are still better than nothing. "Benchmarking" is basically the same thing, and is used all the time as a sanity check for designs.

EMBRAER will be suing you for that EC-20.

Nice drawings.. And you are being introduced to all the basic fundermentals of aircraft design and certification!:ok:

Just make sure you get top grades in Maths and Physics!!:eek:

I'm still trying to work out what kind of weights and performance I could expect if both the EC-20 and -30 were powered by turbofans possibly such as the GeNX or LEAP-X engines or even open rotor models.

Whilst looking at regional jet design, its worth bearing in mind that the customer requirements are quite different to those of large, long range jets.

There is no point in SleazyJet and the like, flying for an hour or two at high speed, only to sit on the ground for twenty minutes waiting for a set of steps to appear. If the same journey can be flown a little more slowly, whilst maintaining the number of journeys per day, then some aerodynamic compromises can be made.

One Airbus A320-sized replacement being proposed by them looked very much like an Ilyushin 76 with rear, fuselage-mounted engines. The low fuselage meant integral 'Air Stairs' were feasible, and the two engines nearer the centreline presumably meant that the excess power requirement for single engine operation was less, as the dead engine was closer to the centreline, and less fin and rudder were required to overcome its drag. The high wing also allowed larger high lift devices, less constrained by ground clearance than, say, the A321's three stage flap. The high-lift devices would allow a smaller wing in the cruise and/or the opportunity to use cheaper airfields with shorter runways.

Taking this last point a step further, presumably if both engines were in the fin, either next to each other 'a la' TU-22 Blinder, or one above the other, which as far as I know, no one has tried yet, with the possible exception of the Trident 3B (albeit two different engines), then the engine-out power requirement would be even less. Yes, it would be ugly; yes, it would be a maintenance nightmare, compared to dropping a wing mounted engine, but if the sums add up otherwise, we might see it, as engines aren't removed that frequently.

Speaking as a maintenance engineer, those #2 engines in the tail can be a bit of a pig to work. Extra downtime for the airlines!

When I was studying for my CAA licence, I found The Mechanics of Flight an excellent book for aerodynamics, fairly easy to understand;

Mechanics of Flight: Amazon.co.uk: Mr A.C. Kermode: Books

Keep up the interest in aviation. You'll be a lot warmer, drier, better paid, less worked, less stressed, less tired in many other industries, but I wouldn't exchange aviation for any of them! Good luck