Author Topic: Max CL and its effect on performance (Read 2452 times)

Crumpp · « **on:** October 12, 2004, 08:48:57 PM »

Anybody know the nuts and bolts of exactly how a high Max CL affects performance. I know Max CL determines the envelope edge so I assume a high Max CL will mean good high-speed maneuverability and ability to carry a heavier useful load.

Any comments or anything to add?

F4UDOA · « **Reply #1 on:** October 13, 2004, 08:18:38 AM »

I know it effects instantanious turn performance although it is not the only factor. Wingloading is the other half of that equation I believe.

Crumpp · « **Reply #2 on:** October 13, 2004, 08:42:43 AM »

Thanks F4UDOA.

I got a report from Focke-Wulf Bremen and it list's the FW-190 Max CL.

It's title is "Drag Data for Aircraft" and lists not only the Drag Polars but all kinds of aeronautical data. Even has the prop efficiency calculations for all the props mounted on the FW-190.

Right now the FW-190's high speed manuverability is primarily a function of it's drag in AH. Doing drag calculations based on the data in this document the FW-190 has less drag throughout a very large portion of the flight envelope than the Spitfire Mk IX.

I suspect the FW-190's high speed manuverability was more of a function of it's Max CL.

Crumpp

Angus · « **Reply #3 on:** October 13, 2004, 08:55:06 AM »

CL=Coefficiency of lift, right?
I have somewhere a big thick book about the principles of flight. I'll take a dip into it and post if I find something useful.
Regards.
Angus

F4UDOA · « **Reply #4 on:** October 13, 2004, 09:10:37 AM »

Crummp,

What does it list as the clmax? Does it list stall speeds power on/off?

Sounds like some great stuff. Any chance of scanning and posting the doc?

Also does it have a flight envelope chart or EM diagram? I have never seen one for the 190.

Sorry about all the questions, sounds like good stuff.

Crumpp · « **Reply #5 on:** October 13, 2004, 12:35:46 PM »

Quote

Sounds like some great stuff. Any chance of scanning and posting the doc?

It turned out to be a very hard document to get my hands on and it cost me a nice chunk of change. Not so sure I just want to give it out just yet. You can bet it will be in my book.

I did send Pyro a copy of the data sheet but I think he might need some help translating some of it. I had native German speakers pulling their hair out with some of the terminology and notations.

I will promise you F4UDOA, you will get a copy of it to post on your sight. You have shared way too much data not to get one.

Hope you understand. BTW I will be making some trips to various archives if I come across any interesting Corsair data I will grab it for you.

Quote

Also does it have a flight envelope chart or EM diagram?

No but it does have all the information needed to construct one.

Quote

CL=Coefficiency of lift, right?

Yes. The Max CL represents the maximum amount of lift a wing can produce AFAIK.

Anybody know the Max CL for the Spitfire, P51, 109, or other A/C to compare?

Crumpp

F4UDOA · « **Reply #6 on:** October 13, 2004, 01:10:14 PM »

Quote

I will promise you F4UDOA, you will get a copy of it to post on your sight. You have shared way too much data not to get one.

Hope you understand. BTW I will be making some trips to various archives if I come across any interesting Corsair data I will grab it for you.

Outstanding!!

GRUNHERZ · « **Reply #7 on:** October 13, 2004, 02:29:51 PM »

Quote

Originally posted by Crumpp
It turned out to be a very hard document to get my hands on and it cost me a nice chunk of change.

Crumpp

Who sells this data? Somehow I imagined these types of war records would be part of some government archive..

Vermillion · « **Reply #8 on:** October 13, 2004, 03:50:14 PM »

Ok, I'm far from an expert and I'm greatly simplfying things to laymans terms, so true aeronautical engineers please correct me.

CLmax as was said is the maximum lift coefficent. Typically the higher the CLmax, the more lift your wing produces (per area) and the the higher the maximum angle of attack (AoA) you can pull in a manuever (lets call it a turn). I *think* its more applicable to sustained manuevers, not instantaneous.

So generally, if two planes have the same sized wing and the same wingloading, the one with the higher CLmax would be more manueverable. But nothing is without cost.

In general, to get a wing with a higher CLmax, you must have a thicker wing. Which means you have more drag, and a lower speed (all other things held equal).

This is all very simplified, but you get the idea.

Crumpp · « **Reply #9 on:** October 13, 2004, 05:22:29 PM »

Thanks Vermillion!

I thought it had something to do with turning ability.

I understand the Spitfire Mk IX had a MAX CL of 1.3. Can anyone confirm this?

Crumpp

Furball · « **Reply #10 on:** October 13, 2004, 05:27:22 PM »

I understand you are completely biased to 190's, and thus a book you write about them will not be an accurate resource to quote or base opinions on. Its like that isigrim guy writing a book on 109's.

Just from what i have seen, i wish you the best of luck writing it though.

Crumpp · « **Reply #11 on:** October 13, 2004, 05:55:22 PM »

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I understand you are completely biased to 190's, and thus a book you write about them will not be an accurate resource to quote or base opinions on. Its like that isigrim guy writing a book on 109's.

You don't even know me Furball. How can you say I am biased?

Crumpp

Furball · « **Reply #12 on:** October 13, 2004, 06:02:11 PM »

I have read what you have posted on here before, and it seems to me that you are that way. Seems you are almost selective in the information you give out to highlight your point.

I often read the more technical posts, i find it fascinating reading about how the real aircraft performed, even though i am unable to comment or really add to the posts myself.

as i said: -

Quote

Originally posted by Furball

Just from what i have seen, i wish you the best of luck writing it though.

bozon · « **Reply #13 on:** October 13, 2004, 06:02:29 PM »

the way I understand it,
the CL_{max} is the maximum lift coeff, obtained when the wing is at the critical AoA. Actually, this is how you define the stall angle.

as said above, this only sets the lift per surface area of the wing - I'm sure you know the formula. Having higher CL_{max} will allow using smaller wing for the same lift produced. The number usually quoted for it is the weighted average for the entire wing so you can just multiply (use the entire-wing lift formula) instead of integrating, when it's a non-uniform wing.

In terms of preformance, this sets the maximum lift (F) of the wing at a given speed and therefor the maximum attainable G load: G=F/m
Higher CL_{max} can be achived by wing profile design or by means of obtaining higher critical AoA - it does not nececerily mean a thicker wing, but it does 'usually' mean a dragier wing (per area).

Bozon

Angus · « **Reply #14 on:** October 13, 2004, 06:06:52 PM »

CL max is multi functional, and tops out at a given speed for a certain design as far as I can see.
My bedtime book for tonight will be a book a got from a pilot friend of mine, "Principles of flight"
I will be back with some simple lines tomorrow.
Regards

Angus