Reducing Form Drag, streamlining Options

[Saltman66]

If you look closely, you'll notice that the 777 has a side-mounted APU exhaust port inside of a faired tail cone. I wonder if other planes could be retro-fitted, eliminating the high drag round and conically-shaped tail cones so common to commercial aircraft? They've done it with the "blended winglets."

[ChillSpiller]

It would be really nice and helpfull if you would add some pictures to your assumption. By doing so one wouldn't have to search for a picture and would know precisely what you mean. Somehow I don't really understand your second sentence and what do blended winglets have to do with APUs?

If you are interested in what shapes are drag efficient as in Cw-value, or just to get an idea:
part1
part2
part3

[Saltman66]

Blended winglets have nothing to do with APU's. What I meant was, Could the conically-shaped tail cones that are so common to most planes be replaced with more streamlined fairings like the ones seen on the 777 and MD-90?
I mentioned the "blended winglets" as an analogy to that because Boeing now offers the airlines the option to increase the performance of their NG737's and 757's by fitting their wing tips with "blended winglets."

[Aspiring Boeing ...]

Blended winglets have nothing to do with APU's. What I meant was, Could the conically-shaped tail cones that are so common to most planes be replaced with more streamlined fairings like the ones seen on the 777 and MD-90?
I mentioned the "blended winglets" as an analogy to that because Boeing now offers the airlines the option to increase the performance of their NG737's and 757's by fitting their wing tips with "blended winglets."

I know what you mean. Probably not is the answer. It would mean fitting a whole new tailcone then having to (maybe) install a different APU to fit into the revised cone. It would also be expensive to do I would imagine.

Blended winglets cost nearly $1 million a set. So any other drag reducing devices would cost a lot too.

Have a look at the Aviation partners website: www.aviationpartnersboeing.com
Regards,
Chris

[Kilrah]

What I'd say is that the current tail cones aren't actually bad... If you have a look at those drag coefficient figures, it's pretty close to what has the lowest drag. I wouldn't really see a significant margin for improvement.

[ChillSpiller]

Thanks for looking into the cw-scedule Kilrah. It actually explains it all. The tailcones on most aircraft are, as the entire A/C itsself is too, well thought threw designs. Sometimesthe engineers try something new just to find out that there is too little improvement for a "retro-fitting". The induced drag that results from the relative small flat area is negligible to the light improvement of a tapered tailcone (if you have a look at the cw numbers). The improvement of cw would be in an area of max.0,02 and only at the very end of the tailcone. The new place for the exhaust will cause a negative change in airflow at its new location. In the end you need to have an exhaust somewhere and wherever it is it cares for a slight amount of drag. A lot of designs have the exhaust at the end such as the A318, A380 or the 787. Since those include the newest designes I will dare to say that that solution is the best.

Blended winglets cost nearly $1 million a set. So any other drag reducing devices would cost a lot too.

That analogy of yours is to be treated carefully. Even a simple idea and an easy implementation of which can have positive effects on the drag. It doesn't necesarily have to be expensive although most A/C parts are.