Best Climb Speed Con't for Nashwan

[Karnak]

Crump,

No, he is saying that the Spitfire's curve is still above the 190's curve at 182mph, even though it is also below the peak of the Spitfire's curve.


For what you're second chart says to be true the Spitfire would have to have a lower climb rate than the Fw190 at 182mph.  According to your second chart the Spitfire's maximum sustained climb angle at 182mph is less than the Fw190's maximum sustained climb angle.  If that were true then the Spitfire would have shed more than 700fpm of climb rate for only 12mph gained in speed.  At that rate the Spitfire's ability to accelerate/climb would terminate at about 250mph.  That is far below the 336mph sea level speed of the LF.Mk IX at +18lbs Boost and the LF.MK IX's 364mph at +25lbs Boost.

[hitech]

Not what Im saying at all crump. Just saying the curves on your chart do not match the data we are discussing.

The terms we are talking about are Vx and Vy. The Y axis of that chart is climb rate. The resone I Know it is climb rate is 2 fold.

One notice how the curves drop to zero: That is the planes stall speed. By definition climb angle is the ratio of Climb to speed. The grey lines you draw are effectly climb angle.


Now the problem is that red curves max is not above the blue curves max. Therefore that chart data shows that the spitfires max climb rate dosn't excede the Fw's max climb rate. Hence the chart data is simply incorect.


HiTech

[Crumpp]

If that were true then the Spitfire would have shed more than 700fpm of climb rate for only 12mph gained in speed. At that rate the Spitfire's ability to accelerate/climb would terminate at about 250mph. That is far below the 336mph sea level speed of the LF.Mk IX at +18lbs Boost and the LF.MK IX's 364mph at +25lbs Boost.

Why? Explain the science behind that statement.


The Spifire had one of the best power to weight ratio's of any fighter in WWII and a phenomenal lift producing wing.  It makes perfect sense that it can draw upon that to achieve such a steep climb angle without much forward speed.

The only way this is not true is IF 170 mph is NOT the highest portion of the Spits power curve.
And if that is true the definition of Best Climbing Speed is wrong.

Crumpp

[Crumpp]

Hitech,

The Y axis represents VSI. It is plotted by points along the vector and represents a angle from the origin to the Power curve.  The higher the angle, the higher the VSI.


The red and blue represent the Power Curves of the Spitfire and the 190 and are plotted along the x-axis. Power Curves do not change but move up and down as a whole unit representing throttle settings.

Crumpp

[hitech]

Crump Lift does not produce climb rate.

HiTech

[Crumpp]

I know that Hitech.


I am not saying that lift does!  I am saying the Spitfire can climb at such a steep angle due to its high thrust to weight.  That does not mean that for each drop in angle you will get a proportionate increase in speed.  

You would think planes act like that but they do not.  Speed gains will be minimal until a certain point because the top of the power curve is flat.

Because the 190 moves closer to it's "rent-free" zone angle for angle, its speed will increase much faster per angle of change down and consequently it will drop faster angle for angle up.

Crumpp

[Karnak]

Originally posted by Crump:
Why? Explain the science behind that statement.

The high mucketymuck number figurin' is past me.  I'm just doing simple logic deductions here.

If the Spitfire obtains it's best climb rate by using a high angle of climb and it's peak climb rate of 4,700fpm is obtained at 170mph then in order for it to be unable to match the Fw190's climb angle only at only 12mph faster when the Fw190's climb angle is significantly shallower the Spitfire would have to have lost more than 700fpm.

If the Spitfire is losing 750fpm of climb rate for every 12mph it gains in speed it will be down to a 0fpm climb rate at about the time it hits 250mph.  Since climb and acceleration are functionally the same the Spitfire will also have reached a state of null acceleration.

These are only crude guestimates as I don't have the knowledge to calculate the drag effects, but it gets the idea across.


EDIT:
Why are the power curves the same?  They are different aircraft with different engines, wings and drag profiles.  Wouldn't the power curves also be different?

EDIT2:
Why does the flat part of the power curve not represent a ability to significantly increase flight speed while only slightly reducing the rate of climb rather than the reverse?

You seem to be saying that by lowering the climb angle the speed and climb rate don't change much until you get out of the flat portion of the power curve.  It seems that:

A) The Spitfire is climbing faster at the flat part of the power curve
B) With only 12mph separating the flat part of thew power curve the Fw190 and Spitfire are going to mostly overlap at their respective flat points
C) The Spitfire climbs faster at the flat points
D) Because they mostly overlap the Spitfire will climb faster than the Fw190 at 182mph.

[hitech]

Crumpp: Please answere the one question. Why is the excess power curve (yes it has to be exccess other wise how could it drop to 0 power) on the spit never above the fw, when you agree the max climb rate on the spit is higher than the fw.


HiTech

[GRUNHERZ]

Originally posted by hitech
Crump Lift does not produce climb rate.

HiTech

Hitech I'm curious does more lift or maybe more wing area play any role in climb rate?

Lets say you took an AH 190D9 and fitted it with a Ta152 wing, what would happend to climb rate?

Or if you took a 109G10 and swapped wings with a Spit 14?

[hitech]

Depends on the drag curv of the wing grunherz: And it will only slightly effect the climb rate. But more lift will effect where the best climb speed is. But the max climb would change only slightly.

[Crumpp]

The high mucketymuck number figurin' is past me. I'm just doing simply logic deductions here.

That's ok Karnack.  I teach some pretty difficult concepts to grasp at work.  

Please don't take my inability to get this point across an indication of my teaching ability!:eek:

I see people all the time who can "parrot".  There products will look exactly like the examples provided but in reality they have no understanding of the underlying concepts.  Somebody throwing co-efficients around to me, in aerodyamics, is a clear statement of their inability to grasp what they really mean.  

"Power + Atitude = Performance" is a clearly logical statement.  However the reality is not that logical.  

Here is a great graph showing the relationship of AoA to airspeed.  You can make some huge angle changes that really don't effect your airspeed much at all past the first few degrees.

http://www.av8n.com/how/htm/aoa.html#fig-ias-cl-aoa


Crumpp

[Crumpp]

Crumpp: Please answere the one question. Why is the excess power curve (yes it has to be exccess other wise how could it drop to 0 power) on the spit never above the fw, when you agree the max climb rate on the spit is higher than the fw.

Because the Spits curve is closer to the origin.  It's stall speed is much less than the 190's.


Here is the explaination of the Power Curve.


The three regions:

http://www.av8n.com/how/htm/energy.html#fig-power-curve-regimes

Various Power settings:

http://www.av8n.com/how/htm/energy.html#fig-three-power

Pulling the Yoke from Cruise:

http://www.av8n.com/how/htm/energy.html#fig-pull-yoke-cruise

Pulling the yoke form slow flight:

http://www.av8n.com/how/htm/energy.html#fig-pull-yoke-slow

Crumpp

[Crumpp]

Somebody throwing co-efficients around to me, in aerodyamics, is a clear statement of their inability to grasp what they really mean.

Let me caveat that by saying "at our level on this BBS".

Crumpp

[hitech]

Crump look at those power curves in the first link you posted. Notice how the Y axis is labeled?

Man it is right before your eyes. Your power curve shows the fw as having the beter max climb rate.


HiTech

[Crumpp]

I don't see it.

All I see is the engine at idle on that curve.


The Spitfires curve will be closer to the origin since it's stall speed is below the 190's.