Performance of the Fw 190A on the Deck?

[Harri Pihl]

Originally Posted by Crumpp

Baloney. You are arguing that the speed reduction is insignificant but you fail to see the entire picture.

What I and Graham have pointed out is that for these kind of aircraft the speed reduction is small at high speed near sea level. And we both do that correctly by using the polar and iteration method which accounts needed higher Cl/Aoa.

Your approach assumes constant Cl/AoA which is not a correct approach for this particular case because with given available power the plane can't maintain constant AoA at higher weight.

Originally Posted by Crumpp

I am very familiar with "your technique" btw. It's not new or original. In fact I use it in a spreadsheet I constructed to predict aircraft performance. I would be glad to share that spreadsheet with you.

It's not "my technique" but very basic use of the polar; Graham does the calculation with the very same principle and anyone with sound basic knowledge would use this technique. And I teached you to use it in Ubiforums some time ago:

http://forums.ubi.com/eve/forums/a/t...6131040055/p/1

You might remember that then you claimed this technique as "misuse of formulas" so I afraid that the sensible discussion is impossible in this case as well.

[Crumpp]

You are about to be ignored. I know very well what the formula's are for as I am degreed in Aeronautical Science.

Once more I am pilot and aircraft owner so I see these affects first hand every time I fly my family on a trip. It's not some academic exercise.

Now go back and find where I said anything about there not being a relatively small top level speed reduction due to weight affects. No one has ever claimed anything but that. Graham is the only one who has tried to narrow the issue to that one subject.

Instead of having a nice conversation, we are dealing with your lack of understanding on how a parametric study works to determine the affect of something. Parametric study is the most common and accepted way of determining the cause, effect, and magnitude.

My issue has always been that Graham's original post:

Actually, fuel state is not that important with regard to maximum speed.

Is not true because one cannot separate the affect as Lift, drag, and Angle of attack all have a fixed by design finite relationship. If the only affect of adding weight was small reduction in top level speed, then we could say it was insignificant.

It is not insignificant. That small drop in level speed represents a very significant reduction in the aircrafts entire maneuvering envelope.

In no way, shape, or form can we say that weight does not matter and has little affect on the airplane.

All considered it’s a healthy concept to keep in mind: the flying weight of your aircraft directly affects its performance. Each time. Every time. No exceptions.

http://www.principalair.ca/article-weight.htm

All the best,

Crumpp

[Harri Pihl]

Originally Posted by Crumpp

You are about to be ignored. I know very well what the formula's are for as I am degreed in Aeronautical Science.

I see that your knowledge has improved somewhat since the days you were posting to the AH board. However, you seem to still have serious problems to deal with basic performance calculations, this case being a good example.

Originally Posted by Crumpp

Now go back and find where I said anything about there not being a relatively small top level speed reduction due to weight affects. No one has ever claimed anything but that. Graham is the only one who has tried to narrow the issue to that one subject.

The thread is about the performance on deck and Graham (and I) have pointed out that the effect of the fuel state to the top speed at deck is small. And we did that by using the correct method which accounts the change of the Cl/AoA.

However, you posted a formula:

V2/V1 = SQRT(W2/W1)

Which is valid only for the constant Cl/AoA and therefore wrong for this particular case. And this is exactly what Graham responded to you in the first page of this thread.

Note that the polar approach used by Graham and me works for any given flying condition while your approach works at one exact Cl/AoA.

All considered it’s a healthy concept to keep in mind: the flying weight of your aircraft directly affects its performance. Each time. Every time. No exceptions.

That is true and no one denies that. However, Graham was correct when he noted that at these particular conditions the effect of the fuel state is not that important, just few km/h.

[Crumpp]

The thread is about the performance on deck and Graham (and I) have pointed out that the effect of the fuel state to the top speed at deck is small. And we did that by using the correct method which accounts the change of the Cl/AoA.

No that is what YOU think it is about and have tried really hard to make it that subject irregardless of what is actually posted.

Which is valid only for the constant Cl/AoA and therefore wrong for this particular case.

You keep repeating that as if parametric study is not valid.

I see that your knowledge has improved somewhat since the days you were posting to the AH board

That speaks volumes. You are a gamer with a bone to chew.

All the best,

Crumpp

[Harri Pihl]

Well, the polar method is the correct method as pointed out several times due to simple fact that it handles the changing Cl/AoA correctly for this kind of analysis. In otherwords the exact change of the speed due to weight can be easily and exactly calculated given that the parameters are correct.

However, the constant Cl/AoA approach which you presented can't be really used for analysis because it does not actually answer the question in hand; it just demonstrates that at different weight, different speed (or power) is needed to maintain constant Cl/AoA.

As a friendly advice I suggest that you should change your attitude and try to actually listen and understand the other people instead keeping lectures on the subjects which the other people might understand better than you. The problem is that you tend to post on number of boards and you continously keep involved on heated discussions where you rarely admit that the problem might be on your side. This thread being a good example.

Perhaps you should actually thank people who help you instead attack; I teached you how to use the polar for turning performance analysis but for one reason or another I tend to receive a lot of harsh words from you.

[Crumpp]

Well, the polar method is the correct method

Once again, an argument of your own determination. The specific performance determination for an individual aircraft has not ever been disputed with the exception of pointing out that you do not couple the affects and take the calculation to it's conclusion.

You simply fail to see the forest for the trees. Your informal education is telling when you fail to recognize the value and mechanics of a simple parametric study.

Credit to James E. Lewis, "Modern Jet Transport Performance":

I teached you how to use the polar

What? Stop with the creepy weirdness.

I am sorry but Embry Riddle taught me to performance calculations in courses like ASCI 310 and ASCI 510.

From my online unofficial transcript in my undergrad days. That is my GPA in bold at the time I completed ASCI 310:

ASCI 310 01D4 Aircraft Performance 3.00 3.00I/A 12.00

Term 4.000 3.00 3.00 12.00
Cum 4.000 6.00 81.00 24.00

Some gamer with an internet education had nothing to do with my aeronautical science education. In fact most internet educated individuals suffer from exactly the same problem with an inability to put it all together.

Good Luck. Find someone else to stalk please.

Crumpp

[Harri Pihl]

Originally Posted by Crumpp

Once again, an argument of your own determination. The specific performance determination for an individual aircraft has not ever been disputed with the exception of pointing out that you do not couple the affects and take the calculation to it's conclusion.

I think that I have said several times that the polar method handles all the variables correctly and works for any given flight condition while the your approach is limited to one given Cl/AoA. Therefore for this particular case, speed change due to weight change, the polar method is the correct one.

And if want to disagree, please prove that with calculation.

Originally Posted by Crumpp

What? Stop with the creepy weirdness.

I am sorry but Embry Riddle taught me to performance calculations in courses like ASCI 310 and ASCI 510.

I quess that you have missed some lectures then or why I had to show the correct method and point out your errors here:

http://forums.ubi.com/eve/forums/a/t...6131040055/p/1

[drgondog]

Originally Posted by Harri Pihl

However, you posted a formula:

V2/V1 = SQRT(W2/W1)

Which is valid only for the constant Cl/AoA and therefore wrong for this particular case. And this is exactly what Graham responded to you in the first page of this thread.

Actually if you look at the equations and substitute Weight for Lift and uses say a 5% increase in Fuel, your CL must increase by 5%. CL varies directly with Weight for Constant Velocity.

Also when the weight increases at the max Power setting for a given altitude, then the Velocity cannot increase, so the CL has to change, thereby increasing induced drag.

CD= CDi + CDp = Cl**2/(pi*AR*e) + CDp

CL=296*W/(S*density ratio*V**2)

For the case in which the velocity was maxed out at the lower weight and max power setting, the velocity must be reduced to achieve the required CL (increased by 5% in e.g.)



Note that the polar approach used by Graham and me works for any given flying condition while your approach works at one exact Cl/AoA.

I believe Crumpp is 100% correct

That is true and no one denies that. However, Graham was correct when he noted that at these particular conditions the effect of the fuel state is not that important, just few km/h.

Use the 51D versus the 51B-15 with the same 1650-7 engine. The weight increase was about 6%, the aerodynamics for Parasite Drag and Induced drag are the same for both airframes.

The 51B with same fuel load was about 600+ pounds lighter - mostly due to the extra pair of 50 cal plus 880 rounds extra ammo.

under these TO conditions the P-51B-15 was about SQRT (Wp51d/Wp51b) difference ~ 1.03 faster than the D... on the deck and at 25,000 feet and everywhere in between.

10+ mph is not insignificant - important enough for NAA to redesign the P-51B/D to the P-51H