3 ms·

IAAAE (I am an aerospace engineer). Actually, long (or wide, to use your term) wings tend to be more efficient. The term you're looking for is "high aspect rati

IAAAE (I am an aerospace engineer). Actually, long (or wide, to use your term) wings tend to be more efficient. The term you're looking for is "high aspect ratio," which efficient airplanes (see the Global Flyer, for example) have in abundance. It is the ratio of wing span squared to wing area (viewed from above, not the front). The explanation for why this is true is complicated, but this gives a good overview: http://en.wikipedia.org/wiki/Aspect_ratio_(wing) http://en.wikipedia.org/wiki/Aspect_ratio_(wing)

ajross 14y ago
Yeah, this isn't insane. Basically it's a T-tail horizontal stabilizer where the vertical stabilizer has been split in four sections and placed outboard to clear the rear-mounted propeller. There's nothing wrong about this. The stabilizer might be a little farther forward than some designs (it's not clear where the c.g. would be looking at that drawing, one assumes in the middle of the four passenger seats), but not radically so. That's not saying it's an amazing new design which will break records or anything (it can't be -- subsonic aerodynamics is literally an 80-year-old-mature technology). But it's attractive and looks like a clean design at first glance.
BenoitEssiambre 14y ago
If I understand correctly, this seems like yet another reason why this Synergy design would be sub optimal. The two sets of short low aspect ratio wings are theoretically less efficient than one set of long high aspect ratio wing. Correct?
- Scramblejams 14y ago
  I don't know what their numbers are, but for an aircraft of its class, the lower wings don't look like they have an abnormally low aspect ratio. The upper wings look to be of a higher aspect ratio than conventional elevators. Since elevators are a source of drag (they usually have to provide some downforce to trim the aircraft in level flight, and you can't make lift without making drag), that could be a win. But then they're close to the CG, so they'll need to provide more trim force (short lever arm as you mentioned), and the advantage might be lost. Of course there are other factors at work. For example, Jet A carries more energy per pound than 100LL and diesels are more efficient, so you carry less fuel for a given range. But the engine needs to be stronger to run a higher compression ratio, so that's some added weight. Every little design feature of an aircraft interacts with every other design feature. Aircraft design can be a tremendously unintuitive affair. That's why it's so fun. So, the proof's in the pudding. The ultimate arbiter of an efficient aerodynamic design is its lift-to-drag ratio, or how much drag is generated for a given amount of lift produced. (See http://en.wikipedia.org/wiki/Lift-to-drag_ratio http://en.wikipedia.org/wiki/Lift-to-drag_ratio) They should be getting good data off their scale model, and if the model's L/D ratio is high and they've done their homework to reflect the full size aerodynamics, then they might have something.
  - evilkillerwhale 14y ago
    Actually, if you read their Kickstarter, they claim to be getting better fuel efficiency with higher cargo weight. They claim this is because it somehow lowers their drag. They also claim that L/D is unimportant for their aircraft, which is why a scaled test is useless to them, even in a wind tunnel. This doesn't pass the smell test for this AE.

ajross 14y ago

Yeah, this isn't insane. Basically it's a T-tail horizontal stabilizer where the vertical stabilizer has been split in four sections and placed outboard to clear the rear-mounted propeller. There's nothing wrong about this. The stabilizer might be a little farther forward than some designs (it's not clear where the c.g. would be looking at that drawing, one assumes in the middle of the four passenger seats), but not radically so. That's not saying it's an amazing new design which will break records or anything (it can't be -- subsonic aerodynamics is literally an 80-year-old-mature technology). But it's attractive and looks like a clean design at first glance.

BenoitEssiambre 14y ago

If I understand correctly, this seems like yet another reason why this Synergy design would be sub optimal. The two sets of short low aspect ratio wings are theoretically less efficient than one set of long high aspect ratio wing. Correct?

Scramblejams 14y ago
I don't know what their numbers are, but for an aircraft of its class, the lower wings don't look like they have an abnormally low aspect ratio. The upper wings look to be of a higher aspect ratio than conventional elevators. Since elevators are a source of drag (they usually have to provide some downforce to trim the aircraft in level flight, and you can't make lift without making drag), that could be a win. But then they're close to the CG, so they'll need to provide more trim force (short lever arm as you mentioned), and the advantage might be lost. Of course there are other factors at work. For example, Jet A carries more energy per pound than 100LL and diesels are more efficient, so you carry less fuel for a given range. But the engine needs to be stronger to run a higher compression ratio, so that's some added weight. Every little design feature of an aircraft interacts with every other design feature. Aircraft design can be a tremendously unintuitive affair. That's why it's so fun. So, the proof's in the pudding. The ultimate arbiter of an efficient aerodynamic design is its lift-to-drag ratio, or how much drag is generated for a given amount of lift produced. (See http://en.wikipedia.org/wiki/Lift-to-drag_ratio http://en.wikipedia.org/wiki/Lift-to-drag_ratio) They should be getting good data off their scale model, and if the model's L/D ratio is high and they've done their homework to reflect the full size aerodynamics, then they might have something.
- evilkillerwhale 14y ago
  Actually, if you read their Kickstarter, they claim to be getting better fuel efficiency with higher cargo weight. They claim this is because it somehow lowers their drag. They also claim that L/D is unimportant for their aircraft, which is why a scaled test is useless to them, even in a wind tunnel. This doesn't pass the smell test for this AE.