Holding the energy

[Debrody]

Thank you for answering sirs 

[bozon]

In level flight.... Your trying to use a blanket statement for all conditions and this is incorrect.
The lower the aspect ratio of a wing the higher the angle of attack the wing stalls at.

You just replaced one blanket statement with another.
High aspect ratio lower the inefficiency caused by wingtip turbulence. These turbulence increase with angle of attack, so a rough statement that high aspect ratio lowers induced drag is justified. Also, the effect will be felt in low speeds and turns where angle of attack is higher than in level high speed flight. Planes that want to fly high use high aspect ratios because the IAS (as opposed to TAS), which is what matters for aerodynamics is quite low and close to the stall speed.

Also, the effects aspect ratio are a bit hard to compare because you cannot keep all the other variables constant. If you keep the area constant it means shorter cord. To then keep the cross section proportional, the wing must be thinner. Then due to the overall down-scaling of the profile you also need to increase the speed to keep the Reynolds number constant - but then the total parasitic drag on a constant area wing will increase...
I think broad statements are justified in this case.

[drgondog]

In level flight.... Your trying to use a blanket statement for all conditions and this is incorrect.
The lower the aspect ratio of a wing the higher the angle of attack the wing stalls at.

At zero lift, there is no difference but as the aspect ratio Increases, the slope of the CL to alpha increases and  drag coefficents decrease with increasing AR.  Reducing AR is desirable for high speed as Cdo dominates but in high CL (like turning and climbing) the higher the aspect ratio the better.

If you have a copy of Abbot and VonDoenhoff you could review this on pages 2-8.

As you know there is no induced drag for a 2-D airfoil (i.e 'infinite' AR, and maximum CDi for AR =1 (or less).  Consider which airframe stalls the fastest with increasing AoA - an F-104 or a U-2? 

Higher aspect ratio wings will reverse any benefit if the airfoil is asked to perform at a high angle of attack. Stalling the airfoil induces drag.
For the same airfoil and all other factors being equal, the lower AR will have higher CDi. This was certainly a factor in Oswald's studies as he pondered the differences in differences between various configuration types in context of total added components of viscous drag.

The question should be as follows. "What plane holds its energy better under certain maneuvers?"

The best example I can come up with to address both issues would be the f-14. It can change its aspect ratio by simple changing its wingspan. It adjusts its aspect ratio to the best configuration for any type of maneuver.

But the F-14 sweeps its wing back to reduce high speed drag effects, and sweep forward to increase Lift and lower CDi for low speed manuevers..

[jamdive]

You just replaced one blanket statement with another.
High aspect ratio lower the inefficiency caused by wingtip turbulence. These turbulence increase with angle of attack, so a rough statement that high aspect ratio lowers induced drag is justified. Also, the effect will be felt in low speeds and turns where angle of attack is higher than in level high speed flight. Planes that want to fly high use high aspect ratios because the IAS (as opposed to TAS), which is what matters for aerodynamics is quite low and close to the stall speed.

Also, the effects aspect ratio are a bit hard to compare because you cannot keep all the other variables constant. If you keep the area constant it means shorter cord. To then keep the cross section proportional, the wing must be thinner. Then due to the overall down-scaling of the profile you also need to increase the speed to keep the Reynolds number constant - but then the total parasitic drag on a constant area wing will increase...
I think broad statements are justified in this case.

So what you are saying is the lift factor is actually changing the effects of the angle of attack, or actually canceling them out with a higher A/R?  I can see this.

[FLS]

Aspect ratio is important when considering the difference between the Ta152 and the FW190 but when you're talking about the F-14 the sweep wing is optimizing supersonic flight vs subsonic handling and it's not the same issue.

[bozon]

So what you are saying is the lift factor is actually changing the effects of the angle of attack, or actually canceling them out with a higher A/R?  I can see this.

You'll have to explain what do you mean by "lift factor" and "A/R". I apologize if these are standard terms, but I am not familiar with them in English.

[drgondog]

Aspect ratio is important when considering the difference between the Ta152 and the FW190 but when you're talking about the F-14 the sweep wing is optimizing supersonic flight vs subsonic handling and it's not the same issue.

Strictly speaking Aspect Ratio is Span>>2/Wing Area. 

When the F-14 extends its wings, both the wing span and AR increases. The swept wing a.) increases the 1/4 chord angle to the Free Stream Velocity vector, optimizing transonic drag rise versus the unswept wing - and b.) decreases parasite drag - but it also reduces AR and increases Induced Drag.

When the wing extends, it decreases the CDi, it increases max CL and optimizes for subsonic manueverability and lowers landing speed dramatically.


It is exactly the same 'thing'

[FLS]

I didn't say it was a different "thing". I said it was a different issue than the thread topic of why different WW2 aircraft bled energy at different rates.

[drgondog]

I didn't say it was a different "thing". I said it was a different issue than the thread topic of why different WW2 aircraft bled energy at different rates.

Fair 'nuff

[FLS]

Fair 'nuff

I'm often overly concise. I appreciate the input.