Author Topic: Aspect Ratio (Read 738 times)

Wilbus · « **on:** September 11, 2002, 06:17:39 AM »

Just wanted to know what it really was so looked it up.

NASA

Basicly, if I've undrestood it right, the HIGHER aspect ratio a plane has, the less drag it has, or have I missunderstood?

If I've understood right, that means that a plane, with, let's say aspect ratio 4 will have more drag then a plane with aspect ratio 8, right?

When it comes to drag, a plane with less drag, should maintain E and accelerate better, right?

Imp · « **Reply #1 on:** September 11, 2002, 06:28:58 AM »

I think you are mostly right

But accelaration is mostly affected by Power loading (as is climb)
Weight divided by Power = Power loading (I think

As for retaining E I think your absolutly right.

Wilbus · « **Reply #2 on:** September 11, 2002, 08:09:09 AM »

Thank you

F4UDOA · « **Reply #3 on:** September 11, 2002, 09:07:56 AM »

Wilbus,

Aspect ratio is slightly over rated sometimes I believe.

It only lowers induced drag or drag caused by lift not parasite drag or drag caused by sheer bulk.

Aspect ratio is most used in A/C that need to fly long distance and create allot of lift and need to cruise a long distance. IE an airliner or spy plane like a U-2.

If you want to really maintain speed through turns and then go fast you will find that A/C with a very low aspect ratio are ideal. Ala the F8F Bearcat or any of the A/C racing at Reno. The first thing they do is chop the wing tips lowering the aspect ratio. If a high aspect ratio was ideal they would add wing span, not reduce it.

Wilbus · « **Reply #4 on:** September 11, 2002, 09:20:49 AM »

Ok, how about maintaining E in the vertical?

Wilbus · « **Reply #5 on:** September 11, 2002, 09:22:15 AM »

Btw, does it mean that they climb very good with high aspect ratio as they need to create much lift?

Mitsu · « **Reply #6 on:** September 11, 2002, 09:39:20 AM »

I heard that high aspect ratio wing is better maneuverability than lower one in vertical.
Takeo Doi, Ki-61 Tony's designer fitted Ki-61's wing with that.
He gave importance to "Span Loading".

Mitsu · « **Reply #7 on:** September 11, 2002, 09:54:39 AM »

Also higher aspect wing has large lift-drag ratio.
it gives good rate of climb, long endurance, good performance at takeoff.

Wilbus · « **Reply #8 on:** September 11, 2002, 11:55:53 AM »

Thanks, reason I am asking, is partly that the Ta152 had a very high aspect ratio wing, spit had about 5.6-5.7 while the Ta152 has got about 6.5.

Should be better in the vertical in such case. P51 had about 6.0.

Mitsu · « **Reply #9 on:** September 11, 2002, 12:16:49 PM »

6.5?

I think Ta152H-1's wing aspect ratio is 8.94...

(14.5)^2 / 23.5 = 8.94

Ta152H1's wing span: 14.5m
wing area: 23.5m^2

F4UDOA · « **Reply #10 on:** September 11, 2002, 12:43:33 PM »

Wilbus,

Another advantage of high aspect ratio is lift at high altitutudes. A/C that operate at extreme alt often have high aspect ratio.

Takeoff and climb are affected by aspect ratio however they are a small part. Take a look at any Carrier fighter and it's aspect ratio. They are all lower than there Army counter parts and they need better low speed hadling and short takeoff run.

Various aspect ratios

F8F-1 = 4.1
F4U = 5.4
F6F = 5.5
P-51 = 5.9
P-38 = 8.3

Wilbus · « **Reply #11 on:** September 11, 2002, 01:40:16 PM »

Yes Mitsu, thought there was something wrong with my calculations as my book say 8.93.

Anyway, should the Ta152 keep energy very well in a zoom as the drag is very low?

funkedup · « **Reply #12 on:** September 11, 2002, 03:08:35 PM »

No lift needed in vertical -> no induced drag -> aspect ratio doesn't matter.

"Keeping energy" is a function of drag AND thrust so you have to look at both if you want that answer.

Aspect ratio is important for induced drag, but equally important is Oswald's efficiency factor (a function of planform shape). More important though is wingloading, because induced drag increases with the square of wingloading for a given speed and turn rate. A good aspect ratio won't help much if you have a high wingloading.

Good discussion here:
http://142.26.194.131/aerodynamics1/Drag/Page6.html
http://142.26.194.131/aerodynamics1/Drag/Page7.html
http://142.26.194.131/aerodynamics1/Drag/Page8.html

dtango · « **Reply #13 on:** September 11, 2002, 03:38:25 PM »

Funked beat me to it

.

Also - It's an oversimplification to only use AR as a key predictor of induced drag. Keep in mind that induced drag varies also with angle of attack (or the amount of lift generated). You can see it in this relationship:

Coeff-ind-drag = Coeff-lift (or AoA) / pi*span eff.*AR

E.g. - Compare the P-51D and Spitfire9 in level flight. The P-51D has more induced drag than the Spitfire9 though the P-51 has a higher AR. The reason is the P-51 has a higher wing-loading (more weight to wing area)--> more lift needed --> more AoA --> more induced drag.

Tango, XO
412th FS Braunco Mustangs

Wilbus · « **Reply #14 on:** September 11, 2002, 04:16:45 PM »

Uhmmm, ok, so what is the meaning of aspect ratio?

Will go read those 3 links, thanks guys