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Then again, the Bf-109K was described by the flight simm website i linked as also having high speed handling issues due to it having a sup'd up HP engine mated to an aging airframe.
30,000 feet or higher
You are correct.
I was looking at Knots at a quick glance to an altitude table. Since the basic concepts are not correct, I did not bother to calculate anything out.
However that does not change the fact Mach .91 is well into the transonic realm and compressible theory applies. The drag forces it must over come are nothing on the scale of the P47 or Bf-109 experience in level flight.
It remains a very poor example.
It is definitely generating an order of magnitude more thrust than the P47 or Bf-109. This statement indicates you have no idea of the basics concepts of power producers and how they develop thrust.
The F-15 is a thrust producer and follows typical thrust producer characteristics. It has considerably more drag to overcome and needs all of that excess thrust to counter transonic drag rise.
Basic stuff, once again.
Baloney.
Name one TAS speed where aircraft performance occurs?
What is Vs1 at sea level in TAS? What is Vs1 at 20,000 ft?
There are very good reasons why EAS is used for comparing aircraft performance by engineers.
That is completely different from your original claim that EAS was not used for aircraft performance comparison. Now you are changing your tune.
"EAS is useful for performance comparisons"
"That is why it is industry standard.
TAS assumes density effects at altitude. Any values calculated using the TAS velocity are only appropriate for that specific altitude.
Using EAS eliminates this as a step and there is no need to recalculate all of our values for density effects.
It is then much easier to convert EAS to TAS if we want to account for density effects. The differences in EAS to TAS velocity are solely based on atmospheric properties alone. Two aircraft at the same EAS will have the same TAS if they are at the same altitude.
However if we want to compare aircraft performance, then using EAS puts the aircraft under the same conditions which is essential for a good comparison."
You gloss over this:
Well if we compare our DYNAMIC PRESSURE between these two aircraft using TAS:
P47 at FL325 467mph * 1.47 = 686fps
q=.5rV^2 = .5*.000840785 slugs * 686fps^2 = 197.8 psf
Bf-109 at FL24 440mph * 1.47 = 6478fps
q=.5rV^2 = .5*.00110327 slugs * 647fps^2 = 230.9 psf
"Dynamic pressure is a function of speed:"
In fact you regurgitate the very reasons we use EAS to compare performance. Using EAS eliminates the density effects of our altitude!
The equivalent airspeed is a direct measure of the incompressible free stream dynamic pressure. It is defined as the true airspeed multiplied by the square root of the density ratio (air density at some flight altitude over density at sea level). Physically the equivalent airspeed is the speed which the aircraft must fly at some altitude other than sea level to produce a dynamic pressure equal to a dynamic pressure at sea level.
Of course we can ignore the science and just go ahead with a silly comparison of airplanes under very different conditions using TAS.
Read questions 1 and 2. Notice what they want the answer's in when comparing aircraft performance!
That's because we cannot navigate without TAS speeds.
Ok, let me straighten things out here;
AFAIK Crumpp never claimed that because two aircraft feel the same EAS then they're going just as fast, he never claimed that.
The effect of altitude is to increase velocity by the SMOE. An aircraft traveling a velocity of 200KEAS at sea level is traveling 200KTAS.
An aircraft traveling 200KEAS at 35,000 ft is traveling 326KTAS.
Both aircraft however are traveling at exactly the same velocity of 200KEAS and neither aircraft has any speed advantage. One just benefits from the effects of altitude.
A quick SWAG of altitude effects using the data provided in this thread shows the Bf-109K4 to be traveling at an equivalent airspeed of 299mph while the P-47N is traveling at 272mph.
440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS
The Bf-109K4 is the faster of the two aircraft according to this data.
Well if we compare our DYNAMIC PRESSURE between these two aircraft using TAS:
P47 at FL325 467mph * 1.47 = 686fps
q=.5rV^2 = .5*.000840785 slugs * 686fps^2 = 197.8 psf
Bf-109 at FL24 440mph * 1.47 = 6478fps
q=.5rV^2 = .5*.00110327 slugs * 647fps^2 = 230.9 psf
Wow! Check that out. The slower aircraft has higher dynamic pressure! That can't be if our planes are under the same conditions.
Dynamic pressure is a function of speed:
q=.5rV^2
If our planes are under the same conditions, then the faster one MUST have the higher dynamic pressure. It's our frame of reference and I am sure you know how important that is in physics.
Like Professor Dave Esser puts it:
"It is the EAS that the aircraft feels. EAS is a measure of the dynamic pressure exerted on the aircraft. This dynamic pressure plays a key role in the lift and drag created by the aircraft. For a given EAS the aircraft feels the same dynamic pressure, and therefore lift and drag, regardless of altitude. The higher the density altitude, the thinner the air, and the faster an aircraft must travel through the air mass to obtain the same EAS."
So lets say two identical are aircraft flying at the same EAS but at very different altitudes, one at SL and the other at 40kft. The a/c at SL needs much less TAS to reach the same EAS as the a/c at 40kft, this is because the air is thinner the higher you go, and therefore you need more speed to achieve the same dynamic pressure around the a/c as compared to at lower altitudes. So if you keep the EAS constant then the higher you go the faster you're going to go as-well. The reason EAS is used for comparing a/c is that at similar EAS similar a/c will have similar turn roll rates regardless of altitude, cause like has been said EAS is what the a/c feels, its the dynamic pressure exerted on the a/c.
Neither Crumpp nor Davparlr seem to be unaware of the above, they both do however seem to have completely misunderstood each other.
So my Conclusion is that Davparlr Crumpp are talking past each other.
PS: Davparlr, its the Ta-152H, not the Ta-154, the Ta-154 never got to see service.
Do you agree here also? Or do you think maybe dynamic pressure is also a function of air density?
This comment is unsupportable. Zero lift drag coefficient for the F-4 (which I am sure is no cleaner than the F-15) is as follows:
Mach .6 .022
Mach .8 .022
Mach .9 .022
No large increases.
This is not totally true, is it?
Dynamic pressure is a function of speed (ft/sec) AND density (slugs/ft^3).
One more time, removing the density effects is the entire reason why we use EAS. Think about that statement for a moment.
It is very hard to compare an airplane to another airplane with removing it.
Quote:
A quick SWAG of altitude effects using the data provided in this thread shows the Bf-109K4 to be traveling at an equivalent airspeed of 299mph while the P-47N is traveling at 272mph.
440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS
The Bf-109K4 is the faster of the two aircraft according to this data.
EAS
So, I understand that you agree with both of these statements? Am I right?
How about this statement
Crumpp said
Well if we compare our DYNAMIC PRESSURE between these two aircraft using TAS:
P47 at FL325 467mph * 1.47 = 686fps
q=.5rV^2 = .5*.000840785 slugs * 686fps^2 = 197.8 psf
Bf-109 at FL24 440mph * 1.47 = 6478fps
q=.5rV^2 = .5*.00110327 slugs * 647fps^2 = 230.9 psf
Wow! Check that out. The slower aircraft has higher dynamic pressure! That can't be if our planes are under the same conditions.
Dynamic pressure is a function of speed:
q=.5rV^2
If our planes are under the same conditions, then the faster one MUST have the higher dynamic pressure. It's our frame of reference and I am sure you know how important that is in physics.
TAS
And how about this example for horse sense. The Curtis P-6A, a biplane, has a top speed of 198 mph TAS at sea level, which equals to an EAS of 198mph. The Ta-154H, has a top speed of 426 mph TAS at 41k ft, which equates to an EAS of 172 mph. Now, according to you, the P-6A, a biplane, is flying faster than one of the fastest aircraft of WWII by over 25 mph! I am sure even Soren doesn't know this. The answer is that the V(42k) necessary have the same dynamic pressure as the P-6A at SL can not be obtained by the Ta-154 at 42k ft., but it is still really going fast anyway, a lot faster than the P-6A and will leave it far behind in no time flat.
Enough of the personal attacks, Crumpp. Any more of them and I will lock this thread.
Once again you have no formal education in Aerodynamics and that is obvious.
I did not point this out as you claimed to be an engineer working in the aerospace industry. There would be no need if you did have the background you claim.
Where did you go to school and take Aerodynamics again?
You do not understand aerodynamics. Your education is incomplete and has failed to link key concepts together for you.