"Lift Loading"

[Ack-Ack]

What you have just described is a situation where an aircraft has higher wing loading but also has a higher maximum coefficient of lift.

Badboy

Would the P-38 be an example of such a plane, if not, what planes would be?


ack-ack

[Cthulhu]

Would the P-38 be an example of such a plane, if not, what planes would be?


ack-ack

Could be. Anybody know what the effective AR of the 38 is?

[Stoney]

Would the P-38 be an example of such a plane, if not, what planes would be?


ack-ack

The P-38 never had a production version that used a different airfoil, that I know of.  Really, the best example would be an aircraft that had the exact same weight, same wing area, but with a different airfoil.  I can't think of anything like that off the top of my head.

Stall speed is a function of Clmax and wing loading, so, in my opinion, those are the two characteristics that should be considered.  For example, if you're trying to design a plane with a certain stall speed, you first look at the lift equation, and solve using the desired stall speed in the velocity term.  This would provide the necessary Clmax at that stall speed.  You could, if you know accurate stall speeds for two aircraft in a given configuration, compare their Clmax by using the lift equation, and solving for the lift coefficient at that stall speed.  Might even give you an indication of flap efficiency if you chose to keep weight the same, and test for stall speeds at each notch of flaps; it would provide the difference in Clmax created by the flaps.

[Golfer]

I can't think of any WWII airplanes off the top of my head that fit the bill.  In the 500 series of Cessna Citations a fair comparison can be made with the Citation II to the Citation S/II.  I don't have my books in front of me but the primary differences between the II and S/II was the wing design.  Replacing the inflatable boot deicing system with a weeping wing fluid system and also changing the shape of the airfoil.  I only flew the S/II one time as a contractor but I do remember being surprised at how well it accelerated when you pointed it down hill when compared with a regular II.  A similar wing designed was used on the Citation V and Ultra which incorporated some other improvements and weight increases so the comparison isn't quite as valid but the Vmo/Mmo of the Ultra was 292kts/.755M compared with the Citation II's 262kts/.705M IIRC.  You gain an extra 30kts and .05M with what amounts to just a change to the wing.

I could dig up the weights if it was really needed but I'm just as sure they're available with a google search if such a compairson was to be made.

[BnZs]

What you have just described is a situation where an aircraft has higher wing loading but also has a higher maximum coefficient of lift.

Badboy

Gotcha. I thought Clmax was only correctly applied to the airfoil section, not the entire wing as a whole. Thanks!

[Ack-Ack]

The P-38 never had a production version that used a different airfoil, that I know of.  Really, the best example would be an aircraft that had the exact same weight, same wing area, but with a different airfoil.  I can't think of anything like that off the top of my head.

Stall speed is a function of Clmax and wing loading, so, in my opinion, those are the two characteristics that should be considered.  For example, if you're trying to design a plane with a certain stall speed, you first look at the lift equation, and solve using the desired stall speed in the velocity term.  This would provide the necessary Clmax at that stall speed.  You could, if you know accurate stall speeds for two aircraft in a given configuration, compare their Clmax by using the lift equation, and solving for the lift coefficient at that stall speed.  Might even give you an indication of flap efficiency if you chose to keep weight the same, and test for stall speeds at each notch of flaps; it would provide the difference in Clmax created by the flaps.

Oh, so it's my awesome uber God like skills in the P-38 that let me turn it like a Spitfire.   


ack-ack

[hitech]

You could define lift loading simply as

(WingArea * MaxLCO) / Weight

In which case it is a very Usefull number to compare some numbers on plane performance.

HiTech

[Ex-jazz]

You could define lift loading simply as

(WingArea * MaxLCO) / Weight

In which case it is a very Usefull number to compare some numbers on plane performance.

HiTech

How this MaxLCo is relating to the wing Aspect Ratio?

[FLS]

Does MaxLCO = CLmax?

[Ex-jazz]

Does MaxLCO = CLmax?

I think the Hitech meant a CLmax, but is it a airfoil CLmax or wing CLmax? If later, then the aspect ration step in to the picture.

[Yeager]

I think the Hitech meant a CLmax, but is it a airfoil CLmax or wing CLmax? If later, then the aspect ration step in to the picture.

You guys talking about "CLimax"? 

[hitech]

Yes CLMax is the same as my Max Lift Coef.

We would be speaking plane CLmax which can be different then the airfoil and and wing. Basically the number is just comparing power off stall speeds of the plane.

HiTech

[gripen]

I've seen the term lift loading used sometimes same way as hitech described above. Theoretically it should give a better picture of lift capability of a airframe than wing loading because the airframes can have very different Clmax values. However, the problem is that there is rarely a consensus which is a proper value of Clmax for a given airframe at given conditions.

[thorsim]

hitech i asked you this on another board, sort of.

are there some planes that for one reason or another much more difficult for you to get a FM that you feel very successful about?

or aspects of flight in general that are just hard to get "right" on a computer ...

i ask just because i think of some things like say "how a 38 rolls" you know "neutral" torque not on the center line etc, slat effects in the 109 ...

i just think how the @$%$ would someone approach such different aircraft in a computer representation.

nothing but sincere interest and a chance for an interesting discussion, not suggesting you have not achieved good results sir, i just think insights into the problems and problem solving would be very interesting.

i understand if you might be apprehensive with this question and or me posting it considering past discussions.

i am just interested/curious ...

Yes CLMax is the same as my Max Lift Coef.

We would be speaking plane CLmax which can be different then the airfoil and and wing. Basically the number is just comparing power off stall speeds of the plane.

HiTech

[Stoney]

However, the problem is that there is rarely a consensus which is a proper value of Clmax for a given airframe at given conditions.

The lift equation is the consensus.  If you know the speed of an aircraft, you can compute the Clmax at any condition.  Now, if you're interested in breaking out the varying components of the plane, and their contribution to lift, there are different methods used (for example, to determine the fuselages contribution) but overall, the lift equation tells you everything you need to know.