# Bf-109K



## Nikademus (Dec 19, 2007)

Hello.

Looking for some more in-depth info on this last varient of the venerable 109 series. Also would like some opinions on how it stacks up in high alt combat vs. the P-47D. Done some self research online but so far havn't found enough to satisfy.

thx in advance.


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## Erich (Dec 19, 2007)

what books do you own on the K variant... ? JaPo actually has a good title or two covering this 109.

check you local Seattle hobby shops - the ones that carry a half decent line of WW 2 aviation titles, that should have something for you


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## Nikademus (Dec 19, 2007)

Erich said:


> what books do you own on the K variant... ? JaPo actually has a good title or two covering this 109.



None specifically. My knowledge base (aka, my "library") tends to be filled with sources on air history, development and campaigns vs. books devoted to a specific plane type. The detail level on the weapons (i.e. the "aircraft") can be extensive for some but not for all types. I'm well familiar with the 109 but don't have alot of info on the K varient.

Reason i'm curious relates to a comment i made on the "Best Aircraft III" sticky. On the board I have frequented most in the past several years, such discussions can't be held without the thread being locked because they ultimately degenerate into noxious appendage wagging flame-fests with the favorite plane/nationality taking the place of the appendage.  

The most recent contest flamed out litterally at 30,000 feet with one offender boasting that the P-47D beat the Bf-109K hands down in every catagory. I think the quote went along the lines of, It can outclimb it, out-turn it, out roll it, outgun it, out-run it, do a dance on the nazi plane's head etc etc. (you can quickly tell why the thread got locked shortly thereafter)

Now what I know....is that yes, the P-47D was arguably the best high alt fighter deployed given it's attributes. I know that the K varient for the 109 was a bit of a interim fix vs. a born high alt killer like the Ta-152H. Basically an over-muscled 109 that i've read was wicked in it's ability to accelerate but the engine was proving beyond the capabilities of the airframe by that point. (not that thats a mark of shame given the plane's been around and viable for nearly 10 years by 1945)

The usual set of stats were posted "PROVING" the P-47D's accendancy but only contained the basic stats most easily googled....i.e. climb rate and max speed which in RL are not absolutes but in messy threads like that one are treated as absolutes. 

Still, despite the sillyness, the thread did arouse my curiousity as the K is one of those planes i don't have a tremendous amount of info about. My best sources on the airwar over Germany only give it a paragraph or two and suprisingly, the Internet had not alot save for one website about an up and coming flight simm. 

I've seen some serious in depth analysis of planes here, most notably one in the Best Plane about the P-51D. Hoping someone can do that with the K.


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## Njaco (Dec 19, 2007)

Don't know if they'll help or if they have the info you're looking for but I have several books about the Bf 109. I'm not sure how accurate they are - I've read bad reviews about Squadron - but others on here may tell you if they're worth it. I would check Amazon or Ebay for them.

"Me 109" by Martin Caidin - part of Ballantine's Illustrated History of WWII:Weapons book # 4

"Messerschmitt Bf 109" by Dr. Alfred Price - Salamander Books, Ltd.

"Messerschmitt Me 109" by Uwe Feist - Aero Publishers 1965

Hope it helps. Check through some of the threads here as that argument has been done here too, with a little more grace.  Some here are VERY knowledgable about the Bf 109, P-47, etc.


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## Kurfürst (Dec 20, 2007)

There you go, some primary performance figures on the Bf 109K-4.

Kurfurst - Your resource on Messerschmitt Bf 109 performance

Taking a brief look at performance, I can`t see much of a difference. The 109K was a high altitude variant with a high altitude engine and propeller. It was competitive at any altitude.

Looking at a random July 1944 test the P-47D did 420 mph at 30 000 feet, or 676 km/h at 9144m. Cross checking that against the K-4 figures, the latter did 696 km/h at the same altitude.

The climb rate is an odd suggestion for the P-47 was known for everything but for it`s astonishing rate of climb.. I mean, looking at the figures, the 47D has lower ceiling (yup!), the RoC at 30k is ca 1300 fpm, or ca 6.6 m/sec vs K4`s 10 m/sec at the same altitude or about 1970 fpm.


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## Njaco (Dec 20, 2007)

Kurfurst, I was trying to remember your website for him.  Thanks.


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## Soren (Dec 20, 2007)

The Bf-109 K-4 was one of the hottest rides of WW2, boasting a top speed of 716 km/h and a climb rate well over 5,000 ft/min, as-well as being one of the very best turn fighters of the war. The Bf-109 K-4 would easily out-turn any American fighter in the ETO, and it would give the Spitfire a run for its money in both turn climb performance.


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## AL Schlageter (Dec 20, 2007)

Soren said:


> The Bf-109 K-4 was one of the hottest rides of WW2, boasting a top speed of 716 km/h and a climb rate well over 5,000 ft/min, as-well as being one of the very best turn fighters of the war. The Bf-109 K-4 would easily out-turn any American fighter in the ETO, and it would give the Spitfire a run for its money in both turn climb performance.


The climb rate graphs on the Kurfurst site don't back up your claim of a climb rate of well over 5000ft/m. The best climb rate shown is just under 25m/s or 4920ft/m and that is for under 1000m height.

Why anyone would want to compare the P-47 to the 109K-4 doesn't make sense unless it is to make the 109K-4 look better. The primary opponent of the 109K-4 would be the P-51.


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## davparlr (Dec 20, 2007)

Kurfürst said:


> There you go, some primary performance figures on the Bf 109K-4.
> 
> Kurfurst - Your resource on Messerschmitt Bf 109 performance
> 
> ...



P-47D-25 will do 433 mph (697 km/h) at 30k.



> The climb rate is an odd suggestion for the P-47 was known for everything but for it`s astonishing rate of climb.. I mean, looking at the figures,



The P-47D was no match for the Bf-109K in climb.



> the 47D has lower ceiling (yup!), [



Nope! The P-47D-25 had a service ceiling of 42k (100 f/m ROC). According to your charts the Bf-109K has .6 m/s ROC at 12.75 km (41,830 ft) or roughly equivalent.

All in all, the Bf-109K was superior to the P-47D at all altitudes. However, it was basically a stripped down, hopped up aircraft with a point defense mission. It is most probably like the Bf-109G-10, which had only a 350 mile range and had only two guns. Also, to be fair, since the Bf-109K was the last model, we should compare it to the last P-47, the N. If so, it appears that the P-47N and the Bf-109K is roughly equivalent at 25K (P-47 is faster, Bf-109 climbs better), but above that, the P-47N has both a speed advantage and climb advantage.


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## davparlr (Dec 20, 2007)

Soren said:


> The Bf-109 K-4 was one of the hottest rides of WW2, boasting a top speed of 716 km/h and a climb rate well over 5,000 ft/min, as-well as being one of the very best turn fighters of the war. The Bf-109 K-4 would easily out-turn any American fighter in the ETO, and it would give the Spitfire a run for its money in both turn climb performance.



I have no reason to doubt any of this.


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## Kurfürst (Dec 20, 2007)

The 109K wasn`t a 'stripped down, point defense' version. It was, basically, a normal fighter like the 109G with an aerodynamically refined airframe and a later, improved high altitude engine. Actually it`s the heaviest version, but the difference is not particularly great compared to other 109G models. Like all 109s, it`s benefitted from the base concept of combining a small, light airframe with a powerful engine.

Range of the Bf 109F/G/K was 1000 miles, not 350. It had three guns, one 30mm MK 108 and two 13mm MG 131s (the G-10/U4, G-14/U4, G-6/U4 carried the same), whereas the basic G-6, G-14, G-10 and their AS models carried the 20mm MG 151/20 cannon instead of the 30mm.

I fail to see any climb advantage for the P-47N. The figures show only up to 28k feet, or 8500 meter, where it does, and 14 000 lbs weight, something like 2200 fpm, or about 11.2 m/sec. Corresponding figure for the 109K is 11.4m/sec, the same for all practical purposes. Below that altitude the climb advantage of the 109K is pronounced. OTOH, the P-47N has speed advantage in the extreme altitude regions thanks to it`s sizeable turbocharger. Up to the most common altitudes however, the 109K holds some slight speed advantage, and considerable climb rate advantage.

Overall, I cannot see great difference, certainly not anything to justify any great claims of superiority, expect perhaps when it came to manouveribility it the turning plane - the P-47 wasn`t particularly hot in that regard, but it had great controllability in the lateral axis.

Basically, the two aircraft display typical qualities of a lightweight, high powered interceptor and a heavier, long range fighter with high fuel capacity. The former sports high performance and agility, high caliber weapons, the latter`s greatest virtue is it`s operational radius.


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## Soren (Dec 20, 2007)

AL,

Yes with the Dünnblatt Schraube, with the thicker std. prop climb went up and speed went down. With the std. prop the climb rate of the Bf-109 was well over 5,000 ft/min - also that kinda says itself with 1,975 HP ! 

Funny you didn't correct the speed I listed though as its 727 km/h with the Dünnblatt Schraube... Am I detecting bias ???


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## Crumpp (Dec 20, 2007)

> Nope! The P-47D-25 had a service ceiling of 42k (100 f/m ROC). According to your charts the Bf-109K has .6 m/s ROC at 12.75 km (41,830 ft) or roughly equivalent.



This does not make much sense to me. Is the contention that the Bf-109K4 high altitude performance is not as good as the P47's?

If that is the case, our figures show the Bf-109K4 is climbing 18% better than the P47 while only 170 ft below it. We still have not reached the 100fpm ceiling of the Bf-109K4 in this case.

Given that performance is a percentage variation over a mean average, it is reasonable to conclude that these aircraft were equal in high altitude performance.

All the best,

Crumpp


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## AL Schlageter (Dec 20, 2007)

Soren said:


> AL,
> 
> Yes with the Dünnblatt Schraube, with the thicker std. prop climb went up and speed went down. With the std. prop the climb rate of the Bf-109 was well over 5,000 ft/min - also that kinda says itself with 1,975 HP !
> 
> Funny you didn't correct the speed I listed though as its 727 km/h with the Dünnblatt Schraube... Am I detecting bias ???


No bias on my part but you sure you are not biased.

Not charts on the site give over 5000ft/min.

How many 1875hp K-4s?


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## AL Schlageter (Dec 20, 2007)

Kurfürst said:


> Range of the Bf 109F/G/K was 1000 miles, not 350. It had three guns, one 30mm MK 108 and two 13mm MG 131s (the G-10/U4, G-14/U4, G-6/U4 carried the same), whereas the basic G-6, G-14, G-10 and their AS models carried the 20mm MG 151/20 cannon instead of the 30mm.


Range at most economical cruise.  Not a good idea in a airspace dominated by the USAAF if one wants to live to old age.

P-47D-25-RE: range ~1500 miles. Range with maximum external fuel was 1800 miles

P-47N-5-RE included a maximum speed of 397 mph at 10,000 feet, 448 mph at at 25,000 feet, and 460 mph at 30,000 feet. Range (clean) was 800 miles at 10,000 feet.


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## Nikademus (Dec 20, 2007)

Kurfürst said:


> There you go, some primary performance figures on the Bf 109K-4.
> 
> Kurfurst - Your resource on Messerschmitt Bf 109 performance



Thank you. Excellent website.


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## Nikademus (Dec 20, 2007)

Crumpp said:


> This does not make much sense to me. Is the contention that the Bf-109K4 high altitude performance is not as good as the P47's?
> 
> Crumpp



Pretty much. I went back and reviewed the offending thread. Here's a posted example:



> ME109 K -- Max airspeed: 440 mph at 7500m (about 24,000 feet).
> ME109H -- Max airspeed 452 mph at 19,685 feet.
> ME109G8++ -- Max airspeed 426 mph at 24,280 feet
> ME109G1-G6 -- Max airspeed 386 mph at 22,640 feet
> ...



One trick the poster is using is quoting the max speed off the N varient which IIRC didn't see ETO service save for a few prototypes and was meant for high alt ops in the PTO. The poster though then switches to a generalization about "all" P-47's being superior (all encompasing) at alt's > 28K


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## Nikademus (Dec 20, 2007)

Kurfürst said:


> The 109K wasn`t a 'stripped down, point defense' version. It was, basically, a normal fighter like the 109G with an aerodynamically refined airframe and a later, improved high altitude engine. Actually it`s the heaviest version, but the difference is not particularly great compared to other 109G models. Like all 109s, it`s benefitted from the base concept of combining a small, light airframe with a powerful engine.



At 30K or higher, which plane, (P-47 or 109k) would turn better or have better "maneuverability"? From what i've read I gather thats a bit of a misnomer since the two planes are energy fighters and any attempt to maneuver into a turning contest will quickly burn off speed and altitude putting the 47 in particular at a more disadvantagous situation but the question of the Bolt's maneuver/agility is oft quoted. I've read that it did become suprisingly "nimble" or "agile" for such a heavy plane at high alt due to the supercharger allowing so much engine power in the thin air but at least one website put that into context saying "It was never a greatly agile but was "suprisingly" agile at high alt for such a big plane" This in heated discussions though is usually translated as "most maneuverable" and/or "most agile" I'm not sure thats the case.



> I fail to see any climb advantage for the P-47N. The figures show only up to 28k feet, or 8500 meter, where it does, and 14 000 lbs weight, something like 2200 fpm, or about 11.2 m/sec. Corresponding figure for the 109K is 11.4m/sec, the same for all practical purposes. Below that altitude the climb advantage of the 109K is pronounced. OTOH, the P-47N has speed advantage in the extreme altitude regions thanks to it`s sizeable turbocharger. Up to the most common altitudes however, the 109K holds some slight speed advantage, and considerable climb rate advantage.



I agree. I misread the old thread a bit. The person didn't specify out-climb but rather kept saying "out-accelerate" so lets turn the question towards that end. At high alt, (say 28-30K) which plane will accelerate faster? My guess would be the lighter plane (without trying to do the math which I try to avoid to save Axons and Dendrites!)



> Overall, I cannot see great difference, certainly not anything to justify any great claims of superiority, expect perhaps when it came to manouveribility it the turning plane - the P-47 wasn`t particularly hot in that regard, but it had great controllability in the lateral axis.



Again...agreed. Like I said, it's the usual appendage wagging contest with limited paper stats being posted to which sweeping generalizations are then added talking about superiority in an artificial 1:1 contest in which the superior plane allegedly holds all the cards. I call it "air combat in a box" type thinking. Chronic on the website i've fruquented. In RL such small differences in preformance don't mean squat in comparison to the other variables. (pilot exp...tactical setup...weather, alt advantage..numerical setup etc etc etc)



> Basically, the two aircraft display typical qualities of a lightweight, high powered interceptor and a heavier, long range fighter with high fuel capacity. The former sports high performance and agility, high caliber weapons, the latter`s greatest virtue is it`s operational radius.



I do recall the flight simm analysis of the K varient suggested that the plane was not very nimble at higher speeds due to the airframe being unsuited to the hot-rotted 1850+HP engine. Truth to it?


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## Soren (Dec 20, 2007)

> No bias on my part


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## Crumpp (Dec 20, 2007)

> One trick the poster is using



Yes, the poster is also listing what appears to be TAS at higher altitude.

This tells us absolutely nothing about the relative velocity. To do that we must convert to EAS.

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.

Since the onset of compressibility errors was not and is not universal even today, we have no way of actually comparing the relative velocity without taking IAS, a PEC, and applying a universal standard of CEC to determine EAS velocities. 



> I do recall the flight simm analysis of the K varient suggested that the plane was not very nimble at higher speeds due to the airframe being unsuited to the hot-rotted 1850+HP engine. Truth to it?



All aircraft traveling at the same angle of bank and velocity will make exactly the same turn. There is no difference in maneuverability between a P-47 traveling at 200mph KEAS and a Bf-109K4 at 200mph KEAS. At a 60 degree bank both aircraft will exactly the same turn.

Sustained maneuvering envelope will be determined by the excess power characteristics and the shape of polars. 

The P47N generates a considerable amount of power at FL325. It also requires a considerable amount of power at FL325. A very quick SWAG of the Nzmax sustainable shows that at combat weight, the P47N is very close to the Bf-109K4 at 1.8ata at Take Off weight. The Bf-109K4 at 1.98ata has a substantial advantage.

In my SWAG I do convert using standard formulation from listed IAS with the types PEC.

All the best,

Crumpp


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## Nikademus (Dec 20, 2007)

Crumpp said:


> Yes, the poster is also listing what appears to be TAS at higher altitude.
> 
> This tells us absolutely nothing about the relative velocity. To do that we must convert to EAS.
> 
> ...



yikes. LoL. After reading posts like this along with others, it didn't suprise me that gentlemen like the one who authored the post i was using as an example chooses to hang out on a gaming website vs. a dedicated aviation forum on which to "educate" us with the _facts_  

Unfortunately, I must include myself in the "aviation for dummies" catagory at least when it comes to breaking down the science of flight itself. Can you walk me through the above a little more in terms of definition of terms/abreviations and how the formulas are used?




> All aircraft traveling at the same angle of bank and velocity will make exactly the same turn. There is no difference in maneuverability between a P-47 traveling at 200mph KEAS and a Bf-109K4 at 200mph KEAS. At a 60 degree bank both aircraft will exactly the same turn.
> 
> Sustained maneuvering envelope will be determined by the excess power characteristics and the shape of polars.



How would you factor in roll rate at x altitude and y speed and rate of turn? 



> The P47N generates a considerable amount of power at FL325. It also requires a considerable amount of power at FL325. A very quick SWAG of the Nzmax sustainable shows that at combat weight, the P47N is very close to the Bf-109K4 at 1.8ata at Take Off weight. The Bf-109K4 at 1.98ata has a substantial advantage.
> 
> In my SWAG I do convert using standard formulation from listed IAS with the types PEC.



SWAG?


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## Crumpp (Dec 20, 2007)

> How would you factor in roll rate at x altitude and y speed and rate of turn?



What is the importance of roll rate or how do I calculate it? 

Calculating it is far beyond the scope of this thread. I can give you some very rough ballpark techniques is all.

_t_ factor, _p_, and several other characteristics are generally derived from test data.

Lateral dynamics are extremely complicated.

Roll rate represents a designs agility or ability to change the orientation of the vector of lift.

SWAG - Scientific Wild Azz Guess

All the best,

Crumpp


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## Crumpp (Dec 20, 2007)

> Can you walk me through the above a little more in terms of definition of terms/abreviations and how the formulas are used?



SMOE - Standard means of evaluation - Term used to descibe 1/SQRT sigma. Sigma is the density ratio which equals pressure/pressure at sea level on a standard day. Pressure units are in slugs/ft^3

To convert velocity in EAS to TAS we have to account for density effects of the atmosphere. 

Here is a primer on airspeed:

Airspeed - Wikipedia, the free encyclopedia

All the best,

Crumpp


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## marshall (Dec 20, 2007)

Crumpp said:


> 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
> ...




I'm not sure that this is fair to say with that info that 109 is faster, because in the above calculations P-47 is 6500ft (2km) higher, so when it would be lower on the same alt as 109 it of course would have smaller max TAS but that still could be more than 440mph for example 441mph. I'm not saying that P-47 is faster, I just think it's not enough info to say that 109 is faster.


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## Crumpp (Dec 20, 2007)

Marshall,

Equivilent Airspeed removes the effects of altitude you understand that right? That is why engineer's use EAS to compare performance and not TAS.



> so when it would be lower on the same alt as 109



Altitude effects are removed so the aircraft ARE essentially at the same altitude or at least in a comparible condition of flight.

Understand?

All the best,

Crumpp


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## Crumpp (Dec 20, 2007)

> Range at most economical cruise. Not a good idea in a airspace dominated by the USAAF if one wants to live to old age.
> 
> P-47D-25-RE: range ~1500 miles. Range with maximum external fuel was 1800 miles



I am confused as to the point you where trying to make. Is Kurfurst somehow being deceitful for listing the range of the aircraft or are you simply pointing out that the range occurred at L/Dmax like every other airplane?

Was the P47 somehow more advantaged when flying at Best Range cruise velocity?

All the best,

Crumpp


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## marshall (Dec 20, 2007)

Crumpp said:


> Marshall,
> 
> Equivilent Airspeed removes the effects of altitude you understand that right? That is why engineer's use EAS to compare performance and not TAS.
> 
> ...




Yes now I understand, my bad but from where do you take the numbers that you divied TAS with them?


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## Crumpp (Dec 20, 2007)

> ME109 K -- Max airspeed: 440 mph at 7500m (about 24,000 feet).
> ME109H -- Max airspeed 452 mph at 19,685 feet.
> ME109G8++ -- Max airspeed 426 mph at 24,280 feet
> ME109G1-G6 -- Max airspeed 386 mph at 22,640 feet
> ...



No claims are made as to the validity of the data. I was just pointing out that unless you know what your doing, these comparison threads are really silly.

When you do know what you’re doing, they become even sillier. All aircraft performance is a percentage range over a mean average. The performance any aircraft exhibits as "normal" can have a very wide swath. 

IMHO, the middle of the envelope is the most interesting. The Prmin point, L/Dmax, and Cl^3/2/Cd are where we really find some unique differences in some of our WWII designs. That and the stability and control issues as it was a very new science at the time.

All the best,

Crumpp


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## AL Schlageter (Dec 21, 2007)

Crumpp said:


> I am confused as to the point you where trying to make. Is Kurfurst somehow being deceitful for listing the range of the aircraft or are you simply pointing out that the range occurred at L/Dmax like every other airplane?


I don't think it is that hard to understand what was said.

A 1000 miles might be good for a delivery flight to the EF where there was no chance of being bounced but once there the typical combat radius was ~140 miles.

I wouldn't say he was being deceitful but more like being dishonest as he failed to say if the range was clean, with drop tank, or with drop tanks.


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## Kurfürst (Dec 21, 2007)

You are just flamebaiting by posting false data in one of your many handles after the others have been banned, that much is clear.


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## Crumpp (Dec 21, 2007)

> A 1000 miles might be good for a delivery flight to the EF where there was no chance of being bounced



You understand that the same goes for the P47 or any other aircraft right?

The difference between Min Specific fuel consumption and Take Off power being 60 gallons per hour and 275 gallons per hour respectively for the P47.

All aircraft had to watch their fuel. The USAAF more so than the Luftwaffe when over Germany.

So these cruising Bf-109's are going be bounced by cruising P47's.

All the best,

Crumpp


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## Juha (Dec 21, 2007)

IMHO P-47 versions that were used same time in Europe than 109K were late Ds and Ms. The latter was used by the last remaining 8th AF P-47 group, 56FG in 1945.
Performance of the P-47M-1-RE included a maximum speed of 400 mph at 10,000 feet, 453 mph at at 25,000 feet, and 470 mph at 30,000 feet. Initial climb rate was 3500 feet per minute at 5000 feet and 2650 feet per minute at 20,000 feet.
In fact it seems that actual test gave the rate of climb for P-47M as at S/L 3960 ft/min, 3740 ft/min at 10000ft and 3300 ft/min at 20000ft.

Juha


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## Crumpp (Dec 21, 2007)

> Performance of the P-47M-1-RE included



AFAIK the first P-47M's arrived in Europe on 04 Mar 1945 but were grounded due to engine difficulties digesting their special fuel until April 1945, just days before the war ended. 

You could say the P-47M is a contemprary of the Ta-152H series and FW-190D13 series more so than the Bf-109K series. IIRC, the Bf-109K4 was operational much earlier in the war than the P47M.

All the best,

Crumpp


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## AL Schlageter (Dec 21, 2007)

Where did you get that mis information?

The first P-47M was delivered from the factory in December 1944 with the 56FG getting their first on *Jan 3 1945.*. On *Jan 14 1945* Paul Gonger made a claim of a 109.

There was problems with the high tension leads cracking (P-47Cs had a similar problem). There was some other problems like defective carb diaphrams, cylinder corrosion and over cooling but fuel was certainly not one of the problems.

On Feb 3 1945 a mission was flown to Berlin.

Yes they were grounded but all the FSs of the 56FG were flying P-47Ms by mid March 1945.


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## Crumpp (Dec 21, 2007)

> Where did you get that mis information?




No misinformation is posted. As I understand the documentation, they arrived at the group for _operational testing_ then but were not posted to operational status until 04 Mar 45. Only *half the squadron aborted* with mechanical difficulties on their first mission in January. The other half flew the mission for the operational trials. Assesments were still needed of types usefulness in combat.

If you want to say that the type was operational from Jan 45 you are free to do so. IMHO, it would be like claiming the FW-190D9 was operational in October 1944. That would not be true however as the type was undergoing operational trials, the last phase of the testing regime to asses its worth as a combat aircraft before acceptance by the gaining service.

The type maintained this dismal relability rate throughout the trials until Pratt and Whitney got involved. Unfortunately Pratt and Whitney's solution turn out not to be the answer and it appears the type was prematurely posted to operational status.

The 50% abort rate the operational trials averaged was never fixed so that when on the very first mission in operational status, it led to the type being grounded until April 1945 so that relability could be increased to an acceptable level for a USAAF Operational Squadron.

Once again, the P47M was not a contemporary of the Bf-109K but belongs alongside the Ta-152H series, FW-190D13 series, and other late war aircraft that were not developed designs by wars end.

That is my opinion. You are entitled to paint the aircraft as fully developed and a viable operational aircraft if you like.

All the best,

Crumpp


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## Juha (Dec 21, 2007)

Hello Crumpp
based on secondary sources only I tended to side Al here. It seems that 47M was grounded twice, a couple days in late Feb and from 16th to 24th March 45. Time to 31th March was troublesome but by leafing through McLaren’s Beware the Thunderbolt! abort rate wasn’t anywhere near 50% during first half of March. And 56th flew ops almost daily. Usually understreght, maybe 50% included also those not even booked for mission?

Juha


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## davparlr (Dec 21, 2007)

Kurfürst said:


> Kurfürst said:
> 
> 
> > The 109K wasn`t a 'stripped down, point defense' version. It was, basically, a normal fighter like the 109G with an aerodynamically refined airframe and a later, improved high altitude engine. Actually it`s the heaviest version, but the difference is not particularly great compared to other 109G models. Like all 109s, it`s benefitted from the base concept of combining a small, light airframe with a powerful engine.
> ...


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## Nikademus (Dec 21, 2007)

> I disagree with these comments. The first delivery of the Bf 109k was in October, 1944. The first delivery of the P-47N was September, 1944, one month earlier. I could not get a delivery start date for the P-47, but considering that in December, 1944, 130 P-47M were delivered and only 24 “N”s, it is reasonable to assume that delivery of the first P-47Ms was in the September, or before, time frame. This does not justify the statement that the P-47M or N was not a contemporary of the Bf-109K.



Well, for what it's worth, this website author would appear to agree with Crump's assertation regarding the hotrod versions of the P-47



> The performance of the YP-47M was excellent, with a top speed of 761 KPH (473 MPH), and the variant was rushed into production to counter the threat of the new German V-1 cruise missiles and German jet fighters. 130 P-47Ms were built, with the first arriving in Europe in early 1945. However, the type suffered persistent teething problems in the field and did not see much action until the war was all but over.



The Republic P-47 Thunderbolt

If the above has a fair degree of accuracy, I'd say it's probably more fair to rate the worked up P-47M/N series against the TA-152H which was Germany's next generation answer to the high alt fighter. The 109K varient I still consider somewhat of an interim fix using an aging airframe passing into obsolecense. They did a decent job considering but ultimately it was falling behind the curve of the newer airframes like the 47.


----------



## Nikademus (Dec 21, 2007)

Crumpp said:


> What is the importance of roll rate or how do I calculate it?



Actually I was referring to the straight up comparisons that usually occur in these "comparison type" threads. In this case (P-47 vs Me-109) at high altitude it was asserted that the Thunderbolt could "outroll" and "out-turn" the Me-109. 

As mentioned, I've read that the Thunderbolt was suprisingly agile and nimble for such a huge fighter in the thin air @ 30+K. But i'm wonder how much more agile it really is. I understand you to say that two planes turning in the same way are identical. The assertation is that one plane can turn/roll more sharply than the other at x speed.




> SWAG - Scientific Wild Azz Guess
> 
> All the best,
> 
> Crumpp



LoL. Thought that was what you meant.


----------



## Nikademus (Dec 21, 2007)

Crumpp said:


> 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.
> 
> ...



Wow....my head is spinning. How did you get the numbers?




> SMOE - Standard means of evaluation - Term used to descibe 1/SQRT sigma. Sigma is the density ratio which equals pressure/pressure at sea level on a standard day. Pressure units are in slugs/ft^3
> 
> To convert velocity in EAS to TAS we have to account for density effects of the atmosphere.
> 
> ...



Thx for the link. Started looking at it, but admitedly all the math is confusing the hell out of me.  I'm still not sure I understand why EAS is more accurate than TAS unless its because the TAS indicator is misleading the pilot because thats what his instrument states but his actual airspeed is calculated via the EAS formula.......

Almost makes me long for the days of Zero vs Wildcat. aieee.


----------



## Crumpp (Dec 21, 2007)

> The first delivery of the P-47*N* was September, 1944



My comments are about the P47*M*.



> It seems that 47M was grounded twice, a couple days in late Feb and from 16th to 24th March 45.



During the operational trials in Feb it was grounded, yes.

Don't confuse operational trials with operational service, however.

In operational service it was again grounded in March. The mission was flown on 04 March 45 as I understand it. The CO of the 56th FS grounded the type and reverted back to their D models which were still on the flight line.

AFAIK, It was grounded because the aircraft was unreliable and was maintaining an average of a 50% abort rate in the squadron.

This would have generated paperwork officially grounding the type and requesting the technical resources to address the problem and get the type ungrounded. I have no doubts those dates originate from such paperwork.

You are free to have your own opinion on this too.

As a pilot, IMHO, this is a really silly argument. The aircraft was not ready for service and had some serious difficulties due to its fuel. While it might seem really peachy to have such an aircraft when you just hit the reset button, a real pilot is risking death a large percentage of the time. He is gambling that he can make it safely to the ground in a machine that has a very good chance of not working properly. There was good reason to ground it and the operational trials were due to end in March. AFAIK, they did end in March after the grounding in February and Pratt and Whitney’s assurances the type would be reliable. 

It did not work out that way and the type was again grounded in March.



> Somewhere between the G-6 and K, 800 lbs was lost.



Several designs experienced this over their lifecycle. Look at the La series in service with the VVS. It does not mean they are "stripped down". Many times just changing a designs dimpling can have a large benefit in weight savings.

Be careful when reading specific engine charts if you do not understand what you are doing. Just warming up, the R-2800 requires 45 gallons of fuel and the P47 has 33 gallons of unusable fuel on board. Some range estimates do not include a reserve while others list a radius.

Make sure too that the engine is capable of operating at its maximum range settings at the altitude under discussion. 

Range data is also listed for a specific altitude in many cases. The range will change based on altitude!

I don't care to argue with game sim fans about when or where their favorite aircraft came into service or how much better it was than all the other game shapes. It's not my cup of tea.


All the best,

Crumpp


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## Crumpp (Dec 21, 2007)

> How did you get the numbers?



Using standard airspeed formulation and converting the numbers from True airspeed back to Equivalent airspeed.

Equivalent airspeed is what is used to compare aircraft performance from one type to another. True Airspeed is not used for comparison purposes.



> As mentioned, I've read that the Thunderbolt was suprisingly agile and nimble for such a huge fighter in the thin air @ 30+K. But i'm wonder how much more agile it really is. I understand you to say that two planes turning in the same way are identical. The assertation is that one plane can turn/roll more sharply than the other at x speed.



Yes agility is very important. The differences in any aircraft _sustained_ turning envelope is a very tiny percentage of the total maneuvering envelope.

An aircraft like the P47 which did have a good roll rate AFAIK, would be a formidable opponent. He can establish a turn faster than a less agile opponent and can use that agility to change the orientation of his vector of lift.

What does that mean? Well any time the vector of lift is pointed below the horizon, a component of weight adds directly to thrust.

AT a combat weight of 12,257lbs a P47D-22 adds 2128lbs of thrust if it drops the vector of lift just 10 degrees below the horizon. In power producers, the faster we go, the less thrust our aircraft produces.

So at 145KEAS our P47D-22 produces 4953lbs of thrust. If we roll our vector 10 degrees below the horizon, we now add 2128/4953 x 100 = 42.9% increase in our Thrust available. This directly translates to Nzmax sustainable and our aircraft can now turn much better. It is a shallow diving turn but our pilot can still pull lead and use the agility of the aircraft to roll the wings level and zoom to gun solution. In ACM, this is called a Yo-Yo.

At 280KEAS our P47 produces 2565lbs of thrust and we can increase our thrust by 2128/2565 x 100 = 82.9% with the same roll.

All the best,

Crumpp


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## Nikademus (Dec 21, 2007)

Crumpp said:


> Using standard airspeed formulation and converting the numbers from True airspeed back to Equivalent airspeed.



ok. In this case:
440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS

How did you calculate the 1.4678 and 1.71295. Thats where i was going "huh?"



> Equivalent airspeed is what is used to compare aircraft performance from one type to another. True Airspeed is not used for comparison purposes.



k. Dumb question. Why do we always see TAS listed for max speed on most sources? Are you saying it has no relevence what-so-ever?




> Yes agility is very important. The differences in any aircraft _sustained_ turning envelope is a very tiny percentage of the total maneuvering envelope.



Agreed. I noticed that in reading numerous accounts. Even in the case of the Zero at times. That and the influence of other outside variables.



> An aircraft like the P47 which did have a good roll rate AFAIK, would be a formidable opponent. He can establish a turn faster than a less agile opponent and can use that agility to change the orientation of his vector of lift.



Agreed. I read a similar attribute to the P-40. Unless at very high speeds it couldn't turn with say, an A6M or Ki-43, but it's very good roll rate might give it a window of opportunity during the initial manuever. The trick was knowing when that window expired leaving the P40 driver in a losing turning battle with a dangerous drop in speed/energy.

All that you wrote not withstanding, I'm still finding myself looking for a more definitive answer. (apologies) Was the P-47 more manueverable at high alt than the 109 in terms of roll/turning rate? equal? inferior? Thats the question i keep asking and that the texts....online and book source don't clearly answer. They say it was "formidable", "agile", "nimble" but its hard to put it into context in the face of simplistic comparisons like the one i posted. 

Sorry for being a math challenged pain the arse.


----------



## marshall (Dec 21, 2007)

Nikademus said:


> ok. In this case:
> 440mph / 1.4678<SMOE FL24> = 299 mph EAS
> 467mph / 1.71295<SMOE FL325 = 272mph EAS
> 
> How did you calculate the 1.4678 and 1.71295. Thats where i was going "huh?"




I also would like to know that.


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## Crumpp (Dec 21, 2007)

Nikademus,

I don't know that I am up to teaching an aerodynamics course in this thread.
My suggestion is that you all attend a college class at your local community college. You will certainly enjoy it and learn quite a bit.

We use equivalent airspeed to compare performance because the forces of flight are equal at the same EAS. Dynamic pressure is constant at the same EAS. 

True airspeed is very useful for flight planning purposes. A variety of information can be derived from it such as our ground speed. It is of little value if your goal is to compare one aircraft with another though, especially using data taken from differing altitudes.

Remember too that there was no standard atmosphere in WWII. The groundwork had been laid but nothing that bound any firm or country to a standard. There were atmospheric variations which can make a difference.

Here is the methodology I used to convert the listed airspeed. The atmospheric model I used was the NACA 1922 atmosphere which was a commonly used one in the US.

All the best,

Crumpp


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## Crumpp (Dec 21, 2007)

> How did you calculate the 1.4678 and 1.71295. Thats where i was going "huh?"



That comes off a standard atmospheric table.


----------



## Crumpp (Dec 21, 2007)

> All that you wrote not withstanding, I'm still finding myself looking for a more definitive answer. (apologies) Was the P-47 more manueverable at high alt than the 109 in terms of roll/turning rate? equal? inferior? Thats the question i keep asking and that the texts....online and book source don't clearly answer. They say it was "formidable", "agile", "nimble" but its hard to put it into context in the face of simplistic comparisons like the one i posted.



Good luck in your quest. My answer would be "It depends." The largest influence on performance being the man at the controls.

All the best,

Crumpp


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## davparlr (Dec 21, 2007)

Nikademus said:


> Well, for what it's worth, this website author would appear to agree with Crump's assertation regarding the hotrod versions of the P-47
> 
> 
> 
> ...



I disagree. The N, and most likely the M, certainly was produced before the Bf-109k and was no more complex than the mod of the Bf-109k only the k had a more mature engine design. Of course we don't know if the k had any engine problems. Again, had the need existed, both aircraft could have met the k within a month or two in spite of some engine corrections.


----------



## Crumpp (Dec 21, 2007)

> Republic rushed vice-president Hart Miller to England to aid in the problem-solving but this soon grew to nightmare proportions when it became obvious that every P-47M operated by the 56th was stricken with some form of problem. Since this was a major problem, the USAAF and P&W assigned their best maintenance crews. Ignition leads were suspect and they were replaced with a different type but the problem would not go away and it seemed that the -57 powerplant was an engine fated not to run.





> Using the WEP setting meant that P-47M pilots would be able to pass the fastest Mustangs at altitude but it would be at a distinct price since the engine at that setting would be consuming an astonishing 330 gallons per hour! The late D Model Thunderbolts could carry 370 gallons of fuel internally so it did not take a genius to figure out the range.





> Airflow to the cylinders was modified so that the heads could heat to the most efficient temperatures. It was discovered that the sensitive engine/turbosuper-- charger controls were not being correctly operated, so additional training for pilots was required along with some modifications. Considerable minor modifications and fine-tuning meant that the engine gradually gained a degree of reliability but, eventually plagued by just too many problems, the engines of every operational M were changed in an attempt to gain combat readiness.





> *As the war in Europe fought to a close, the P-47M was finally operationally deployed during April 1945*



High altitude thunderbolt Air Classics - Find Articles

All the Best,

Crumpp


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## AL Schlageter (Dec 21, 2007)

> AFAIK the first P-47M's arrived in Europe on 04 Mar 1945



Nice of you to ignore the fact the P-47Ms arrived in GB in early Jan 1945.

You have yet to post any info on this supposed fuel problem. 44-1 fuel passed testing in July 1944.

That is one heck of an operational trial flying a 5.5hr mission deep into enemy territory (Berlin) on Feb 3 1945.



> Don't confuse operational trials with operational service, however.



So you would say the Me262 did not have operational status with Erprobungskommando 262 and Kdo Nowotny. That would make the Gloster Meteor the first operational jet powered plane.

Same could be said for some of the Me109s like the 1.98ata one.


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## Nikademus (Dec 21, 2007)

Crumpp said:


> Good luck in your quest. My answer would be "It depends." The largest influence on performance being the man at the controls.
> 
> All the best,
> 
> Crumpp



I didn't realize it was the holy grail. Perhaps if i bring onto thee....a Shrubbery.  


Kidding aside, yes, i realize that the man at the controls as well as other outside variables ultimately impact the combat which is what makes stat-tic comparisons all the more meaningless when the testosterone starts to fly. At times though, some people manage to come up with figures like in the attached pic. I was wondering if similar information existed for the 109 and P-47.


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## Nikademus (Dec 21, 2007)

davparlr said:


> I disagree. The N, and most likely the M, certainly was produced before the Bf-109k and was no more complex than the mod of the Bf-109k only the k had a more mature engine design. Of course we don't know if the k had any engine problems. Again, had the need existed, both aircraft could have met the k within a month or two in spite of some engine corrections.



I'm not too big into the "had the need existed, it would have been done" line of reasoning. I've heard the same thing used in regards to Me-262 discussions. (i.e. the P-80 would have been deployed much sooner had the need existed) Yet in recent 8th AF literature, such a postulation is not put forward.


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## Nikademus (Dec 21, 2007)

Crumpp said:


> That comes off a standard atmospheric table.



Can one find a table on the Internet?


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## Nikademus (Dec 21, 2007)

Crumpp said:


> Nikademus,
> 
> I don't know that I am up to teaching an aerodynamics course in this thread.
> My suggestion is that you all attend a college class at your local community college. You will certainly enjoy it and learn quite a bit.
> Crumpp



Ok. Thx for the info and the chart. It'll give me something to fiddle with between Quarters. 8)


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## davparlr (Dec 21, 2007)

Crumpp said:


> Several designs experienced this over their lifecycle. Look at the La series in service with the VVS. It does not mean they are "stripped down". Many times just changing a designs dimpling can have a large benefit in weight savings.
> 
> Be careful when reading specific engine charts if you do not understand what you are doing. Just warming up, the R-2800 requires 45 gallons of fuel and the P47 has 33 gallons of unusable fuel on board. Some range estimates do not include a reserve while others list a radius.
> 
> ...



Of course. All these data points have many variables that we cannot control. We only have the data available to asertain aircraft performance. We typically try to find the most reliable available but it is often difficult to find if it exist. That doesn't stop us from debating and learning.



> I don't care to argue with game sim fans about when or where their favorite aircraft came into service or how much better it was than all the other game shapes. It's not my cup of tea.
> 
> 
> All the best,
> ...



I beg your pardon! There are many people on this site that are extremely knowledgable about various subjects and, while I might disagree with them, I admire them highly and respect their opinion and most of the young gamers tend to have interesting questions and make reasonable comments (or they don't stay here long). As for me, I have a bachelor in Math, a master in Aeronautical Systems, and have worked for over 30 years in the aerospace industry including time as a military pilot and a design engineer and manager for advanced military fighter and bomber aircraft. I am sorry that discussing war planes with us is not your cup of tea.


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## davparlr (Dec 21, 2007)

Crumpp said:


> Equivalent airspeed is what is used to compare aircraft performance from one type to another. True Airspeed is not used for comparison purposes.
> 
> Crumpp



I don't understand this comment. Almost all the data I have seen on aircraft is in TAS including record setting activity. In reality, at a given altitude, TAS is an accurate reflection of aircraft performance for comparison. Since combat is usually at roughly the same altitude, TAS performance between two aircaft is a accurate comparison. For example, if aircaft A can fly at 400 mph TAS at 20,000 ft and aircraft B can only fly 350 mph TAS at 20,000 ft, then if they are in combat at 20,000 ft, aircaft A has a clear airspeed advantage. And I am not sure I understand the value of the point you were trying to make on comparing the equivalent airspeeds at different altitudes-

440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS

Obviously, a plane going 467 mph may be slower than the other plane at the lower altitude and just maybe the one going 440 mph may go faster than the other plane at higher altitude, however, this does not necessarily reflect impact of EAS so much as it reflects the optimization of the superchargers. Could you explain the importance of EAS to aircraft performance comparison in more detail?

Also, just because the aircraft that is going at 299 mph EAS, it does not mean that it is going faster than the aircraft going 272mph EAS. If the plane going 467 mph TAS (272 mph EAS) leaves New York along with the plane going 440 mph TAS (299 mph EAS), and there is no wind factor between the various altitudes, the first plane (with the lower EAS) will arrive in Washington ahead of the other (with the higher EAS).


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## Crumpp (Dec 21, 2007)

> I beg your pardon!



If the shoe fits then wear it. If it does not, then it probably does not apply to you!

I certainly enjoy these aircraft. That is why I fly and work so hard at restoring these aircraft to flight. 

I am all for discussing aircraft, their history, and learning something or passing some knowledge on. 

I also not into your attitude towards me either. If you were more secure in your position, I don't think I would be explaining my comment to you. It would be self evident. If you have worked so hard in the industry, WHY AM I EXPLAINING EAS TO YOU???? I have never had to explain that to someone who is versed in aeronautical science, it is a given and industry standard.

For that matter why did I have to explain the basis for TBO determination in the other thread?



> I don't understand this comment.





> Could you explain the importance of EAS to aircraft performance comparison in more detail?



The dynamic pressure remains constant over EAS. Dynamic pressure changes over TAS.

Co-efficient of lift and drag are nothing more than the ratio of dynamic pressure to lift or drag pressures.

Holding our dynamic pressure steady gives a basis to compare aircraft performance. This is why engineers use EAS for performance comparison purposes. 

When we convert from EAS to TAS, the aircraft has nothing to do with it. The conversion is based on the physical properties of the atmosphere. 

EAS just eliminates the density differences in the atmosphere as a factor.

Since our original poster placed data from different altitudes, I simply eliminated the altitude as a factor for comparison. 



> Can one find a table on the Internet?



You should be able to find STD ATM charts on the internet. Most of them are the 1976 standard.

I have done an analysis of the Bf-109 series, Spitfire series, P 51 series as well as the P-47D-22, Nzmax sustained for one of the other members of this forum. That thread is in this forum. In fact I am supposed to do an analysis of the Me-262 for him too. Unfortunately, it just takes time and this a really busy part of the year. Just have not had the chance to work on it.

I would be happy to give it my best shot in teaching you some techniques for determining aircraft performance. PM me so we do not clutter up this thread.

All the best,

Crumpp


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## Crumpp (Dec 21, 2007)

> Nice of you to ignore the fact the P-47Ms arrived in GB in early Jan 1945.



Yes I it would have been more accurate to say they arrived in Jan 44 but were unable to pass operational trials until April 45.

It is not more accurate to characterize the aircraft as being on normal operational status from the date of their arrival on. That is just a misrepresentation IMHO.

Again, that is my opinion and you are free to form your own. 

Once again this is a very silly discussion IMHO. I don't think any pilot would be thrilled to have to fly an aircraft with such a high failure rate. They certainly would not have classified it as a viable operational type.



> That is one heck of an operational trial flying a 5.5hr mission deep into enemy territory (Berlin) on Feb 3 1945.



Well when that is the kind of operations your Air Force is doing, it only makes sense right?

All operational trials are conducted under actual operational conditions. That is why they are termed "Operational Trials". 



> Erprobungskommando 262



I don't think you have much knowledge of the language at all because your question is nonsensical.

Test Command 262......

Yes, the 262 was under operational testing status in Erprobungskommando 262.

Now the Luftwaffe did some unusual things. They formed test commands for specific types and on occasion these commands continued on with other aspects of testing while previous results entered operations.

The Luftwaffe formed these test units for specific test regiments. You would have to look to Erprobungskommando 262's specific mission for details on the scope of their responsibility.

Erprobungskommando 190 for example was jointly manned by Focke Wulf factory pilots and Rechlin pilots. Its final mission was to convert II/JG26 to type and then it was disbanded. II/JG26 conducted the operational trials of the FW190A.

All the best,

Crumpp


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## Kurfürst (Dec 22, 2007)

davparlr said:


> Kurfürst said:
> 
> 
> > Bf-109G-6 empty weight – approx 6000 lbs (multiple sources)
> ...


----------



## HoHun (Dec 22, 2007)

Hi Davparlr,

>I am not an armament guy but I suspect there are those that would argue that two 50 cals and a 30 mm does not exhibit better firepower than eight 50 cals. Especially for a fighter.

If you look at the actual firepower in terms of total energy at the muzzle, you'll realize that the MK108 really was in a class of its own.

Here is the firepower per barrel comparison for the three weapon types we're looking at:

MK 108: 5.03 MW
MG 131: 0.21 MW
12.7 mm Browning M2: 0.28 MW

Total battery:

Me 109K-4: 5.45 MW
Eight-gun P-47D: 2.27 MW
Six-gun P-51D: 1.70 MW

(See also WORLD WAR 2 FIGHTER GUN EFFECTIVENESS )

The Me 109K-4 has the additional advantages of having centreline armament that leads to a high concentration of fire regardless of range, and of featuring weapons with a low dispersion, contributing to the concentration.

The US types on the other hand have the advantage of a higher muzzle velocity, which is helpful for hitting manoeuvering targets. The wing-mounted guns on the other hand introduced convergence/divergence effects that reduced concentration of fire considerably. (Not all US-types, of course - the P-38 did have nose-guns, and was often praised for its great gunnery characteristics.)

Here you can find summaries of two comparative Luftwaffe reports on armament:

http://www.ww2aircraft.net/forum/aviation/info-me262-big-gun-nose-2905.html#post297044

Note that the second report concludes that the low velocity MK 108 armament is superior over the high-veloctiy MK 103 + MG 151/15 armament at ranges up to 600 m even against hypothetical Mosquito-sized jet bombers.

Regards,

Henning (HoHun)


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## AL Schlageter (Dec 22, 2007)

Crumpp said:


> I don't think you have much knowledge of the language at all because your question is nonsensical.
> 
> Test Command 262......


I know very well what Erprobungskommando is.  

The point I was trying to make, and you failed to comprehend, is that there are some who claim German planes had operational status whether with Erprobungskommando or regular LW units.


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## Crumpp (Dec 22, 2007)

> *is that there are some who claim* German planes had operational status



What in the world does this have to do with the thread or with me? 

_There are also *some who claim* you need a new pair of tennis shoes if you want to catch a ride on the mothership._



> All 39 were dressed in identical black shirts and sweat pants, brand new black-and-white Nike tennis shoes, and armband patches reading "Heaven's Gate Away Team."



http://en.wikipedia.org/wiki/Heaven's_Gate_(cult)

That would be different topic of discussion however than this one. The fact you would concoct a pointy tin foil hat theory that has nothing to do with me and then apply to an unrelated conversation speaks volumes.

I don't think it is productive to reply to you. Perhaps in the future, if you mature some, we can have some good conversations. You seem to have a good knowledge base about some things.

All the best,

Crumpp


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## Crumpp (Dec 22, 2007)

> If you look at the actual firepower in terms of total energy at the muzzle, you'll realize that the MK108 really was in a class of its own.
> 
> Here is the firepower per barrel comparison for the three weapon types we're looking at:
> 
> ...



Good post.

All the best,

Crumpp


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## Nikademus (Dec 22, 2007)

Kurfürst said:


> davparlr said:
> 
> 
> > In other words, the differences are not particularly considerable; not even at altitudes where air combat is rather rare to happen, and here we are comparing low-production run stripped, hotrod P-47 sporting only six .50 guns IIRC. It`s a nice and faster aircraft than the rest at altitude, but it`s performance profile is somewhat hard to take advantage of, isn`t it? OTOH, I am not at all convinced of it`s manouveribility at high altitude. The P-47 is a very high wingloading aircraft, and figures I have for early models display the worst turn times of all WW2 fighters I`ve seen.
> ...


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## Nikademus (Dec 22, 2007)

Crumpp said:


> Good post.
> 
> All the best,
> 
> Crumpp



seconded.  

The value of a centerline armament is often too lightly dismissed...esp when that centerline is a cannon!


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## evangilder (Dec 22, 2007)

Crumpp said:


> What in the world does this have to do with the thread or with me?
> 
> _There are also *some who claim* you need a new pair of tennis shoes if you want to catch a ride on the mothership._
> 
> ...



Speaking of off-topic, nothing to do with the thread...



Crumpp said:


> I don't think it is productive to reply to you.



Then maybe you shouldn't. You have a point to make, then do it. Leave your petty BS out of the thread.


----------



## Crumpp (Dec 22, 2007)

> One post says that it was one of the best turn fighters, yet other sources say the opposite.



If you learn to calculate it yourself, this will never be an issue to you!


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## Soren (Dec 22, 2007)

Evangilder,

I strongly disagree with you, Al had that one coming!


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## evangilder (Dec 22, 2007)

I suggest you stay out of it, Soren.


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## Crumpp (Dec 22, 2007)

It is not hard to do the math Nikademus. I know you would be able to do it.

Basic premise is to determine our lift/drag forces in 1 G level flight solve for parasitic component of drag, and then use our power available to find the increase in induced drag if we maximize our turn from that level condition of flight.

It does not sound that easy when I read back over it but if you started working it you will find it is not that hard to do.

All the best,

Crumpp


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## Soren (Dec 22, 2007)

No problem Evan.


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## lesofprimus (Dec 22, 2007)

And I second that... Aint nothin worse than second man in Soren, and u know that...


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## Soren (Dec 22, 2007)

Roger that Les.

Evan's response just puzzles me thats all, but I'll stay out of it, sorry for intervening.


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## Juha (Dec 22, 2007)

Hello Crumpp
a question, 
“During the operational trials in Feb it was grounded” 
I’m little puzzled, what sort of operational trials was that, because at the time of Feb grounding 56th FG, not squadron, had 67 P-47Ms, that more than ½ of the production run. Number is from Freeman’s 8th AF War Manual. IMHO it was odd to use best part of production run in operational test. Was that USAAF was more interested in the engine, which was more or less same than that used in 47N? 47N was much more important type to USAAF and was coming out from production lines and of which AAF had ordered some 1900 in summer 44.

and a couple points

“some serious difficulties due to its fuel.”
according to Freeman that was suspected during the problems in March but found untrue and the real reason was bad anti-corrosion treatment of engines before sending them to GB.

“the engines of every operational M were changed in an attempt to gain combat readiness.”
According to Freeman, only engines with under 50h run time were changed, they figured that if engine had run successfully over 50h it didn’t have corrosion problems.

Juha


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## Crumpp (Dec 22, 2007)

> I’m little puzzled, what sort of operational trials was that, because at the time of Feb grounding 56th FG, not squadron, had 67 P-47Ms,



AFAIK, the 56FG received the entire production run for the P47M for the types life history. All 130 examples produced over the variants lifecycle were given to the 56th FG, correct?

It is no different that III/JG54 receiving the entire production run of the FW-190D9 during its trials or all the stafflen conducting the trials. 



> anti-corrosion treatment of engines before sending them to GB.



That generally comes in the form of oil or fuel additives. 

It can involve all the way up to complete replacement of the oil with a "pickling" compound. This is generally done for long term storage and was not likely done IMHO to the P47M's.

All the best,

Crumpp


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## Juha (Dec 23, 2007)

Hello Crumpp
“AFAIK, the 56FG received the entire production run for the P47M for the types life history.”

I have read the same info from somewhere. That was my point, USAAF had decided to gave the whole production run to 56 FG, IIRC there were no plans for further M production. The P-47 which USAAF was interesting was extra long range P-47N which in essence was IIRC mating of extra long range -47K airframe with the powerplant of -47M ie P&W R-2800 C or in USAAF parlage R-2800-57, new turbocharger and automatic powerplant controls. So IMHO the only logical reason, other than some bureaucratic reason, for operational testing of M was to get info on reliability of R-2800 C engine in operational environment. The XP-47N was a modified YP-47M.

“It can involve all the way up to complete replacement of the oil with a "pickling" compound. This is generally done for long term storage and was not likely done IMHO to the P47M's.”

I have thought the reason was to protect engines from saltier sea air during shipment to GB. Of course in that case the assumption is that they went over by sea. I have no info how they crossed the Atlantic.


“Using the WEP setting meant that P-47M pilots would be able to pass the fastest Mustangs at altitude but it would be at a distinct price since the engine at that setting would be consuming an astonishing 330 gallons per hour! The late D Model Thunderbolts could carry 370 gallons of fuel internally so it did not take a genius to figure out the range.”

A bit provocative, I think. Who would use WEP an hour?

Anyway, if we go back to late 109s, in Finnish AF Bf109G combat missions usually lasted a bit under 1h and Finns saw it as a short range fighter as Fiat G.50 and definitely short legged when compared to Brewster Model 239 (export version of F2A-1) and even to Hawk 75A (export version of P-36). One example of ferrying 109Gs, from Wiener Neustadt (Austria) to Helsinki (Southern Finland), Wiener Neustadt – Schöngarten/Breslau – Thorn – Jesau/Köningsberg – Riga – Helsinki. Those towns in todays Poland with their German names.

Juha


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## davparlr (Dec 23, 2007)

Kurfürst said:


> davparlr said:
> 
> 
> > Leer-/ Abluggewichts (empty/takeoff weights) of G-6 through K-4, as per primary German datasheets from the war :
> ...


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## Crumpp (Dec 23, 2007)

> A bit provocative, I think. Who would use WEP an hour?



I certainly did not take the article as making a claim of the engine using WEP for an hour.

It is standard to give aircraft fuel consumption figures in volume used per unit of time. 

Gallons per Hour are in standard use in the United States. I think most European countries use Liters per Hour.

Not very provocative IMHO! Just airplane terminology is all.



> I have thought the reason was to protect engines from saltier sea air during shipment to GB.



It most certainly was reason, Juha. However the level of precaution needed amounts to what most coastal owners do! We don't need to pickle the motor as that entails added expense and difficulty bringing it back to service.

There are a variety of fuel or oil additives that will do the job additional corrosion protection without the complications of pickling.

This does not mean that some of the engines were not pickled from the manufacturer as they awaited installation. Re-pickling them after installation does not make much sense, however.

All the best,

Crumpp


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## Crumpp (Dec 23, 2007)

> It seems that the grounding was only for a month.



*You could characterize the service of the P47M as entering service in Jan 45 and continually operating in combat until VE day.* 

We can ignore the fact this assumes the USAAF did not conduct operational trials or testing of a product they purchased to ensure it could perform the job requirements it was purchased to fulfill. Despite the fact that makes no sense at all as operational testing was simple standard operating procedure for any service. 

Is that a true representation of design so troubled the Vice President of the company heads out to the field to personally supervise maintenance?

Is that a true representation when the abort rate averages 50% on every sortie the type attempts? 62nd Squadron in March 445 had 6 out of 14 aircraft abort due to mechanical difficulties resulting in several pilot fatalities. This isn't an airplane; it is a cleverly disguised game of Russian roulette at this point.

Is that a true representation when the official service adoption data is listed as March 45?

We are all free to make up our minds given the facts.

It all comes down to your subjective opinion and what you are willing to accept.

Is the P47M a fully operational adopted fighter from Jan 45 until VE day that contributed greatly to the war effort?

Is the P47M a troubled design that continued to have difficulty even after reaching Operational status in Mar 45? A design that, like its contemporaries the Ta-152 or Tempest II, represented the pinnacle of propeller driven technology that just was not quite ready for service during the war in Europe.

All the best,

Crumpp


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## Juha (Dec 23, 2007)

Hello Crumpp
I didn't mean the info itself but the end of quote "...The late D Model Thunderbolts could carry 370 gallons of fuel internally so it did not take a genius to figure out the range.”

Juha


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## Nikademus (Dec 23, 2007)

Crumpp said:


> It is not hard to do the math Nikademus. I know you would be able to do it.



I'm not so sure. I once made my 9th grade Algebra teacher throw up her hands in despair.  




> Basic premise is to determine our lift/drag forces in 1 G level flight solve for parasitic component of drag, and then use our power available to find the increase in induced drag if we maximize our turn from that level condition of flight.



I sense a PM coming your way pleading for mercy.


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## davparlr (Dec 23, 2007)

Crumpp said:


> I also not into your attitude towards me either. If you were more secure in your position, I don't think I would be explaining my comment to you. It would be self evident. If you have worked so hard in the industry, WHY AM I EXPLAINING EAS TO YOU???? I have never had to explain that to someone who is versed in aeronautical science, it is a given and industry standard.
> The dynamic pressure remains constant over EAS. Dynamic pressure changes over TAS.
> 
> Co-efficient of lift and drag are nothing more than the ratio of dynamic pressure to lift or drag pressures.
> ...



Perhaps the following will explain my confusion.

You wrote earlier-



> Yes, the poster is also listing what appears to be TAS at higher altitude.
> 
> This tells us absolutely nothing about the relative velocity. To do that we must convert to EAS.
> 
> ...



This statement is entirely incorrect. More in detail.



> Yes, the poster is also listing what appears to be TAS at higher altitude.
> 
> This tells us absolutely nothing about the relative velocity. To do that we must convert to EAS.
> 
> ...



Let’s look at TAS. It is defined like this-

*True airspeed (TAS)* is the speed of an aircraft relative to the airmass in which it flies, i.e. the magnitude of the *vector difference of the velocity of the aircraft and the velocity of the air*. *Under zero wind conditions and in horizontal flight, this is equal to the speed over the ground*.

So, in your example, assuming no wind, the first aircraft at sea level is going 200KEAS which equals 200KTAS. According to the definition above, the aircaft has a ground speed of 200 kts (also, a speed through the air mass of 200kts). Now the second aircraft at 35,000 ft is going 200KEAS or 326KTAS. Now, according to the TAS definition, this aircraft has a ground speed of 326 kts (and a speed through the air mass of 326kts). This is why high altitude aircraft can get such good milage.



> 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.



Both aircraft are indeed going the same EAS but the aircraft at 35000 ft. is going much faster, through the air and over the ground, than the one at sea level by everyone’s definition.



> 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*
> ...




You claim that the aircraft with the highest EAS is the faster of the two. We just showed that, in reality, the one with the TAS advantage is the faster (through the air and over the ground). Now, to show the uselessness of EAS without some other supporting data lets look at this set of data.

At 24000 ft the P-47M has a TAS of 451 mph. Now according to your formula, We have.

440mph / 1.4678<SMOE FL24> = *299 mph EAS*
451mph / 1.4678<SMOE FL24> = *307mph EAS*

Now you would say, that the P-47M was faster of the two aircraft. This is different from your initial conclusion.

Now, let’s do the reverse. The Bf109K4 at 32500 ft has a TAS of 430 mph. Now we have 

430mph / 1.71295<SMOE FL325> = *249 mph EAS*
467mph / 1.71295<SMOE FL325> = *272mph EAS*


Again the P-47M has a higher EAS (much higher), thus higher speed (according to you), but again, you originally said that the Bf-109K4 was the faster of the aircraft. There is a problem with your theory. It does not take into account the HP curves of the two aircraft. I think you will find that the Bf109K4 (and all aircraft, since EAS roughly represent F or drag on the aircarft) requires a certain fixed hp to maintain a constant EAS. However, as the aircraft climbs, the hp is not constant and starts to drop off and it cannot maintain EAS (supercharger operaion also affect hp curve). In this case it drops off quite a bit faster than the P-47M (they start out a roughly an equal EAS at 24k ft but the Bf-109K4 EAS drops quite a bit lower than that of the P-47M by 32.5k ft.

EAS is useless in comparing aircraft at different alitudes without some idea how hp is behaving. It is accurate at the same altitude but then TAS is by far a better estimate.

I was able to find a couple of charts that showed EAS in all the flight test reports and contractor reports. This was on the F4U and showed EAS as a function of hp. A light went on and I realized that this was very useful in calculating aircraft airspeed performance if you did not have a test. By knowing the hp required for an EAS (maybe by a test at sea level or computer), and by knowing the hp output of an engine at an altitude, the EAS can be found and one can calculate TAS of the aircaft at that altitude. I suspect this is one of the major uses for EAS. Apparently it is also used in other performance items other than speed.

For this site use, TAS at a specific altitude, which is data that is typically readily available, is the best method for comparing aircraft performance. And since air combat between two aircraft usually occur at roughly the same altitude (pre-AA missile environment), this is plainly satisfactory. EAS, which is not readily available, is not worth calculating and just confuses the issue. Again, without horsepower behavior over altitude, comparing aircraft airspeed of aircraft at different altitudes, whether using EAS or TAS, is not a valuable effort. 

I would bounce this off one of your aero friends. I am always willing to know when I am wrong.


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## Crumpp (Dec 24, 2007)

> You claim that the aircraft with the highest EAS is the faster of the two.



It is the faster of the two aircraft. Your whole argument is nonsensical.
Do you understand about the important of dynamic pressure and its relationship to aircraft performance? I really don’t think you have a clue about it.

This is lack of understanding of the basic fundamentals. 

I will give it my best shot to help you out.

For example:

It is a fact that the coefficients of Drag represents the ratio of drag pressure to dynamic pressure and equals DRAG PRESSURE / DYNAMIC PRESSURE.

If we want to compare our Bf-109 and our P47 using TAS, any idiot can see that the P47 is the much faster aircraft, right!

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=.5r*V^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.

Of course we can ignore the science and just go ahead with a silly comparison of airplanes under very different conditions using TAS.



> Both aircraft are indeed going the same EAS but the aircraft at 35000 ft. is going much faster, through the air and over the ground, than the one at sea level by everyone’s definition.



Only because of the density effects of altitude, because our air is less dense, our dynamic pressure is less at a given velocity. Hence we have a much larger difference in our TAS and our EAS.



> A light went on and I realized that this was very useful in calculating aircraft airspeed performance



*It is useful for all aspects of aircraft performance, see above.* 

Don't add any silly uninformed leaps of logic to it. Just leave it at that.

From an old college textbook:







> I was able to find a couple of charts that showed EAS in all the flight test reports and contractor reports. This was on the F4U and showed EAS as a function of hp. A light went on and I realized that this was very useful in calculating aircraft airspeed performance if you did not have a test. By knowing the hp required for an EAS (maybe by a test at sea level or computer), and by knowing the hp output of an engine at an altitude, the EAS can be found and one can calculate TAS of the aircaft at that altitude. *I suspect this is one of the major uses for EAS.* Apparently it is also used in other performance items other than speed.



It's my opinion that you have *never* worked on any aeronautical science field or related to aeronautical engineering. I think your posturing was complete baloney.

You would at least have a grasp of the *basic fundamentals*. 

Airspeed is a step by step process. You cannot skip one airspeed type and directly convert to another.

Your "discovery" is a simple basic fact of aerodynamics. If you want to know the TAS, you first have to know the EAS. If you want to know the EAS, you first have to know the CAS. In order to find the CAS, you have to have the IAS.

So the big mystery of finding EAS before finding TAS is solved!

On your other observation, you don't need EAS to get the effects of power. Power effects maintain the same ratios over any given velocity measurement. The effect is relative. Just keep track of your units!

Some airspeed’s are more useful for certain things. IAS is very useful for flying the plane. TAS is useful for finding our Ground Speed and flight planning.

EAS is useful for performance comparisons.

Neither EAS nor TAS is very useful for comparing aircraft data recorded over different atmospheric models with different standards for the application of compressibility affects. Comparing data recorded in Germany by Mtt directly with data recorded by North American is silly and meaningless unless the data is converted to the others standards.



> Again, without horsepower behavior over altitude,



Obviously you do not realize that if we have TAS we do not need power data to figure EAS. All we are doing is accounting for the density effects of the atmosphere on our airspeed. Eliminate the effects of altitude and we have our EAS.

Since you felt so compelled to brag about your being an engineer and working in the aerospace industry, what part of it did you work in, again? 

Honestly, this about as basic as you can get and all of this would be covered in a 100 level Aerodynamics course. It is readily apparent you have had absolutely no formal education whatsoever in this field.

All the best,

Crumpp


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## Nikademus (Dec 24, 2007)

Is it reasonable to suggest that TAS makes for an ok basic comparison if the two planes are at the same altitude?


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## Crumpp (Dec 24, 2007)

> Is it reasonable to suggest that TAS makes for an ok basic comparison if the two planes are at the same altitude?



Sure!

As long as the data is all converted using the same standards.

See, despite some uninformed speculation, all of this data is calculated. 

The "flight test data" still has to be converted from actual to standard conditions, the PEC, CEC, and density effects still have to be applied. 

When you get right down to it, all the data calculated!

All the Best,

Crumpp


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## Nikademus (Dec 24, 2007)

all-right. That clears up some confusion. 8) 

Now in regards to the chart I posted in post#51 on page 4 showing estimated roll and turning rates at x speeds for several major airframes. Is _that_ useful for a basic comparison and if so, does any similar info exist for the Bf-109K and P-47D/M?


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## Crumpp (Dec 24, 2007)

> all-right. That clears up some confusion.



You cannot use same altitude TAS when comparing a report written in Germany by Mtt on an airplane flown in March and make any meaningful comparison with a report written in Britian on a Plane flown in August by the Boscume Down.



> Is that useful for a basic comparison



I would say it is not useful. 

Some very large unknowns:

1. Condition of the aircraft?

2. Is all the data collected and processed using the same formulation and methodology?

3. Was the onset of CEC applied to a universal standard?

4. Was the atmospheric model the same?

I have some reports I can share. IIRC it has both the P47 and Bf-109 series roll rates. The data is not useful for specific comparison. You cannot say, plane X out rolls plane Y by a specific rate. Frise ailerons have a very wide swath of normal range. 

All you can do is get a general idea of most probable trends in performance. The term for it is "in the realm of significant digits it is correct". 

All the best,

Crumpp


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## HoHun (Dec 24, 2007)

Hi Crumpp,

>It is the faster of the two aircraft. Your whole argument is nonsensical.

Hm, I think Davprlr actually has a point. Equivalent Air Speed is a useful tool, but it works best when we can assume that the available propulsive power is proportional to the density of the ambient air, which is a commonly used approximation - but only an approximation.

Non-linear supercharger curves, the effect of exhaust thrust, Mach-dependend propeller efficiency etc. can affect the EAS comparison - Davprlr points out that top speed EAS varies with altitude even for one aircraft, which demonstrates that we can't simply pick one certain top speed EAS and consider it representative for the type.

EAS undisputedly is very useful to compare relative performance if only one data point for each aircraft is given ... as often the case with lesser known types.

Merry Christmas,

Henning (HoHun)


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## Juha (Dec 25, 2007)

Hello Crumpp
“A design that, like its contemporaries the Ta-152 or Tempest II, represented the pinnacle of propeller driven technology that just was not quite ready for service during the war in Europe.”

to my understanding Tempest II missed the war altogether so I’d say that it ‘s service entry was later than that P-47M.

If we look 56 FG missions from 10th March 45 onwards when the P-47M pilots got their second kill according to Frank Olynyk, 56 FG last P-47D kill had been very early in Feb 45 according him, 
10.3.45 23 Jugs up no mentions on aborts
11.3.45 49 Jugs up, one Jug crashed in England, pilot killed
12.3.45 51 Jugs up, six aborts and one landed in France on way home
14.3.45 “A” Group 36 Jugs and “B” Group ? Jugs, 3 Jugs landed on continent because of mechanical problems and one crashed into Channel, pilot killed.
15.3.45 again “A” and “B” Groups, no numbers, 6 hours mission, one take-off crash, pilot killed.
24.3.45 first mission, 24 Jugs up, no mention of aborts
24.3.45 second mission 36 Jugs up, no mention of aborts

Source McLaren’s Beware the Thunderbolt!
Clearly problems on some missions in the first half of March, but nothing near your 50% abort rate, may I ask Your source(s)?

Juha


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## davparlr (Dec 25, 2007)

Crumpp said:


> It is the faster of the two aircraft. Your whole argument is nonsensical.
> Do you understand about the important of dynamic pressure and its relationship to aircraft performance? I really don’t think you have a clue about it.
> 
> This is lack of understanding of the basic fundamentals.
> ...



Of course the pressure is higher in the second equation because the medium in which it is traveling is denser (more slugs)! The value of the force has increased because it requires more effort to go through a denser medium. You can ride in a boat at 10 mph with your hand out and feel a slight pressure from the air. If you put your hand in the water, it would feel it could be snatched off. That is not because you are going faster through the water than through the air, you are not; it is because the water has many times the density of air causing a lot more drag. This also occurs, to a lesser extent, in the air as we go from a higher altitude to a lower altitude. The increasing density of the air causes the force to increase without any change in airspeed.




> It's my opinion that you have *never* worked on any aeronautical science field or related to aeronautical engineering. I think your posturing was complete baloney.
> 
> You would at least have a grasp of the *basic fundamentals*.



You found me out. I am really a thirteen year old gamer.



> On your other observation, you don't need EAS to get the effects of power. Power effects maintain the same ratios over any given velocity measurement. The effect is relative. Just keep track of your units!



Huh? Let's see, we have TAS, EAS, and hp. Not many units to keep track of.



> Some airspeed’s are more useful for certain things. IAS is very useful for flying the plane. TAS is useful for finding our Ground Speed and flight planning.



This, I agree.



> EAS is useful for performance comparisons.



This is true for some aircraft performance parameters, just not for airspeed comparison at different altitudes




> Neither EAS nor TAS is very useful for comparing aircraft data recorded over different atmospheric models with different standards for the application of compressibility affects. Comparing data recorded in Germany by Mtt directly with data recorded by North American is silly and meaningless unless the data is converted to the others standards.



I did assume that Germany has the same atmosphere as the US. I wasn’t aware that compressibibity calculation were different in Germany. Soren, can you educate me on this? I guess you mean we must convert metrics to english or vice versa? I guess I should have thought of that.




> Obviously you do not realize that if we have TAS we do not need power data to figure EAS. All we are doing is accounting for the density effects of the atmosphere on our airspeed. Eliminate the effects of altitude and we have our EAS.



All I was saying is that in order to maintain an EAS as you climb, hp must be constaint. Since hp is never constant in climb, predicting EAS at a different altitude, without the hp generated at that altitude cannot be done. If an aircraft is making 350 mph EAS at sea level generating 1000 hp and it climbs to 10000 ft. the EAS cannot be predicted because the engine may only be generating 800 hp therefore the plane is going to be going slower and having a lower EAS. If the engine was still generating 1000 hp, the EAS would still be 350 mph.



> Since you felt so compelled to brag about your being an engineer and working in the aerospace industry, what part of it did you work in, again?



Only because you called me a gamer. 



> It's my opinion that you have never worked on any aeronautical science field or related to aeronautical engineering. I think your posturing was complete baloney.
> 
> You would at least have a grasp of the basic fundamentals.





> If we want to compare our Bf-109 and our P47 using TAS, any idiot can see that the P47 is the much faster aircraft, right!


 
And now I am an uneducated idiot gamer?



> Honestly, this about as basic as you can get and all of this would be covered in a 100 level Aerodynamics course. It is readily apparent you have had absolutely no formal education whatsoever in this field.
> 
> All the best,
> 
> Crumpp





Using your quotation, here is a simpler example of the difference between EAS and actual speed. If you drive at 50 mph at sea level and stick you hand out, you will feel a certain amount of pressure, this represent EAS which would also represent TAS. If you go to the mountains at 10000 ft., and 50 mph, and stick you hand out, the pressure on your hand would be less. It is not less because you are going slower through the air, you are not, but rather because the density of the air is less (the air is thinner). You are now going at a lower EAS (< 50mph) but your actual speed through the air is the same (50mph). In order to calculate your actual speed from measuring the pressure on you hand (assuming there is no wind) you would have to correct the pressure felt by some factor to correct for the density change in the air (in other words calculate TAS). This is an accurate representation of what is required in finding your true speed in an airplane. First you measure dynamic and static airpressue (indicated airspeed), correct for any installation error (calibrated airspeed), correct for compressability (air is compressable and therefore generates error) (equivalent airspeed), and then you must correct for atmospheric density changes (air pressure and temperature) (true airspeed), which would then show your actual speed through the air mass.

Crumpp, you have taken a specific altitude and a specific airspeed for a Bf-109K4 and compared that with a specific altitude and specific airspeed for a P-47M an stated that the K is faster than the M. I have shown that you can take other specific airspeed and altitudes and, using your logic, come up with a completely different conclusions. You have ignored commenting about that. Instead of addressing these descripancies, you have become abusive.

Two more examples I would like you to explain:

F-15 flying at 600 mph TAS at 55,000 ft. Using your calculations the F-15 EAS is 209 mph. Using your logic, the F-15 is flying at 70% of the speed of the Bf-109K4. This is not logical nor aerodynamically true.

SR-71 flying at Mach 3 at 100,000 ft. Using all the appropiate formulas for calculating TAS and EAS for supersonic flow we get a TAS of 2048 mph and a EAS of 238 mph. You may say that both the P-47M and Bf-109K4 is going faster than the SR-71 because their EAS is higher but I bet you a bottom dollar that the SR-71 would make it from LA to NY in a whole lot less time than the other two aircraft.

Boy, I hope I kept track of my units!

So here is a list of the plane discussed in descending EAS values , and according to you, the fastest one is at the top and the slowest one is at the bottom.

Bf-109K4, at 24k ft, TAS = 440mph, *EAS = 299 mph*

P-47M, at 32.5k ft, TAS = 467mph, *EAS = 272 m*ph 

SR-71, at Mach 3, 100k ft, TAS = 2048 mph, *EAS = 238 mph*

F-15, at 55k ft, TAS = 600 mph, *EAS = 209 mph*

It appears intuitively obvious to me that EAS is not an accurate way to compare aircraft airspeed, but what do I know, I’m an idiot.

Crumpp please address these items:

1. 440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS

440mph / 1.4678<SMOE FL24> = 299 mph EAS
451mph / 1.4678<SMOE FL24> = 307mph EAS

430mph / 1.71295<SMOE FL325> = 249 mph EAS
467mph / 1.71295<SMOE FL325> = 272mph EAS


Why does the first equations make the Bf-109K4 faster than the P-47M (“The Bf-109K4 is the faster of the two aircraft according to this data”) and the other two do not make the P-47M faster than the Bf-109?

2. If EAS represent the true (verses true airspeed) airspeed of an aircraft, would you say that the two piston power planes are faster than the F-15 and SR-71? 


True airspeed is called true because it represents the actual speed of an aircraft through an air mass. EAS does not.

If my question above confuse you, take them to one of your aero buddies which I really think you should do anyway.


There are many young airplane enthusist on this site that are seeking to understand the froces that affect aircraft and I feel that are you are misleading them in relation to EAS and airspeed comparison.

Sorry guys for writing so much but I think that it is important for everyone to understand accurately the relationships of the various airspeeds.


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## davparlr (Dec 25, 2007)

MERRY CHRISTMAS everyone. I hope you all have a great holiday time.


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## Soren (Dec 25, 2007)

A Merry Christmas to you as-well Davparlr!


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## evangilder (Dec 25, 2007)

Crumpp said:


> "It's my opinion that you have *never* worked on any aeronautical science field or related to aeronautical engineering. I think your posturing was complete baloney.
> 
> You would at least have a grasp of the *basic fundamentals*. "
> 
> ...



While you give good information in your posts, the above examples are the kind of statements that I will again ask you to stop. You have information to share, great, please do. Keep the insults and personal attacks out of it.


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## Crumpp (Dec 25, 2007)

> Non-linear supercharger curves, the effect of exhaust thrust, Mach-dependend propeller efficiency etc.



Merry Christmas, Henning. I hope things are going well for you!

He does not have a point. He does not understand the basics and that is obvious. 

*Power effects are irrelevant to the type of airspeed as long as you maintain the same airspeed classification and the ratio relationship.*

Using EAS makes "altitude changes much easier to do this in fact. Only difference in using EAS and "changing altitude" is that we only have ONE parameter to change in our analysis, the power!

You understand what I am saying right? If you want to change altitude, all we have to do if our analysis uses EAS is change the power available to the value at that altitude.

*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. 

All the best,

Crumpp


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## Soren (Dec 25, 2007)

You're right Crumpp but perhaps Davparlr has forgotten some of this. I haven't experienced Davparlr ever being dishonest, just so you know.

Merry Christmas all!


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## Crumpp (Dec 25, 2007)

> This is true for some aircraft performance parameters, just not for airspeed comparison at different altitudes



EAS is the only acceptable way to compare aircraft speeds at dissimilar altitudes. Otherwise it is impossible to tell if the plane is really faster or if it is just receiving the benefits of being higher in altitude.



> I did assume that Germany has the same atmosphere as the US. I wasn’t aware that compressibibity calculation were different in Germany. Soren, can you educate me on this? I guess you mean we must convert metrics to english or vice versa? I guess I should have thought of that.



Any basic or entry level aerodynamics class will teach you this!



> All I was saying is that in order to maintain an EAS as you climb, hp must be constaint.



Climbing is a different condition of flight and uses different formulation. If you had some formal education in aerodynamics, you would know this. You would also know that using some basic calculus to derive the change in one value based of the relationship of another value is very much in the realm of possibility.

There are different techniques and formulation out there in the community but most are based on this simple principle.



> Using your quotation, here is a simpler example of the difference between EAS and actual speed. If you drive at 50 mph at sea level and stick you hand out, you will feel a certain amount of pressure, this represent EAS which would also represent TAS. If you go to the mountains at 10000 ft., and 50 mph, and stick you hand out, the pressure on your hand would be less. *It is not less because you are going slower through the air, you are not, but rather because the density of the air is less (the air is thinner).*
> 
> *Wrong. Your speed through the AIR is slower. Your hand is at a lower dynamic pressure. I have already shown you the math on this and if you have any education in physics then you know this is fact.*
> 
> ...



Here is where you are making your errors in logic.

You think like you’re in a car.

Aircraft are machines of the air. 

On the units, you have completely misunderstood what I wrote to you.

We have to maintain the same ratio relationship and units.

In other words, if we wanted to figure our _power required_ at a new velocity, we could use the ratios:






We could use IAS, CAS, TAS, or EAS for our Velocity as long as we are consistent.

These boards do not accept MathType fonts so it makes it very hard to display equations.

All the best,

Crumpp


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## HoHun (Dec 25, 2007)

Hi Crumpp,

>If you want to change altitude, all we have to do if our analysis uses EAS is change the power available to the value at that altitude.

I believe that's what Davprlr meant to point out too when he contrasted speed data points of the Me 109 and the P-47 for identical altitudes 

It's my impression that at the core of the issue, there isn't actually that much of a disagreement after all.

In any case, this looks like a good example for my personal hobbyhorse - the overriding influence power plants have on aircraft performance! 

Regards,

Henning (HoHun)


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## davparlr (Dec 25, 2007)

Crumpp said:


> Merry Christmas, Henning. I hope things are going well for you!
> 
> He does not have a point. He does not understand the basics and that is obvious.
> 
> ...



Actually, I don't think I have ever disagreed with any of this except the last statement for comparing airspeed at different altitudes with different aircraft using EAS.


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## Crumpp (Dec 25, 2007)

> Davparlr has forgotten some of this.



Certainly that could be the case. He has forgotten a considerable amount of information.



> Keep the insults and personal attacks out of it.



Look. I am really trying not to insult anyone in this or make any personal attacks. 

We are having some stumbling blocks over some very basic concepts. I will try not to put it in terms of credibility.

I know some folks on these boards who have worked in the aerospace industry some time ago and have forgotten things. However the conversations are still on an entirely different level. Every case is different.



> In any case, this looks like a good example for my personal hobbyhorse - the overriding influence power plants have on aircraft performance!



Absolutely! Power available to Power required IS the fundamental relationship that determines aircraft performance.




> I believe that's what Davprlr meant to point out too when he contrasted speed data points of the Me 109 and the P-47 for identical altitudes



Over the same altitude, there is no need to convert to TAS. The relative performance remains the same as TAS is soley a function of the properties of the atmosphere.

Merry Christmas All! 

All the best,

Crumpp


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## davparlr (Dec 25, 2007)

Soren said:


> You're right Crumpp but perhaps Davparlr has forgotten some of this. I haven't experienced Davparlr ever being dishonest, just so you know.
> 
> Merry Christmas all!



So, you agree with this statement.

"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"

If so, you must agree with this-

So here is a list of the plane discussed in descending EAS values , and according to Crumpp, the fastest one is at the top and the slowest one is at the bottom.

Bf-109K4, at 24k ft, TAS = 440mph, *EAS = 299 mph*

P-47M, at 32.5k ft, TAS = 467mph, *EAS = 272 mph *

SR-71, at Mach 3, 100k ft, TAS = 2048 mph, *EAS = 238 mph*

F-15, at 55k ft, TAS = 600 mph, *EAS = 209 mph*

Therefore, the Bf-109K4 and the P-47M are both faster than the SR-71 and F-15 because they have a higher EAS.


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## davparlr (Dec 25, 2007)

Crumpp said:


> Certainly that could be the case. He has forgotten a considerable amount of information.
> 
> 
> 
> ...




You still have refuse to answer my inquiry on the following examples

Crumpp, you have taken a specific altitude and a specific airspeed for a Bf-109K4 and compared that with a specific altitude and specific airspeed for a P-47M an stated that the K is faster than the M. I have shown that you can take other specific airspeed and altitudes and, using your logic, come up with a completely different conclusions. You have ignored commenting about that. Instead of addressing these descripancies, you have become abusive.

Two more examples I would like you to explain:

F-15 flying at 600 mph TAS at 55,000 ft. Using your calculations the F-15 EAS is 209 mph. Using your logic, the F-15 is flying at 70% of the speed of the Bf-109K4. This is not logical nor aerodynamically true.

SR-71 flying at Mach 3 at 100,000 ft. Using all the appropiate formulas for calculating TAS and EAS for supersonic flow we get a TAS of 2048 mph and a EAS of 238 mph. You may say that both the P-47M and Bf-109K4 is going faster than the SR-71 because their EAS is higher but I bet you a bottom dollar that the SR-71 would make it from LA to NY in a whole lot less time than the other two aircraft.


So here is a list of the plane discussed in descending EAS values , and according to you, the fastest one is at the top and the slowest one is at the bottom.

Bf-109K4, at 24k ft, TAS = 440mph, EAS = 299 mph

P-47M, at 32.5k ft, TAS = 467mph, EAS = 272 mph 

SR-71, at Mach 3, 100k ft, TAS = 2048 mph, EAS = 238 mph

F-15, at 55k ft, TAS = 600 mph, EAS = 209 mph

It seems intuitively obvious to me that EAS is not an accurate way to compare aircraft airspeed.

Crumpp please address these items:

1. 440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS

440mph / 1.4678<SMOE FL24> = 299 mph EAS
451mph / 1.4678<SMOE FL24> = 307mph EAS

430mph / 1.71295<SMOE FL325> = 249 mph EAS
467mph / 1.71295<SMOE FL325> = 272mph EAS


Why does the first equations make the Bf-109K4 faster than the P-47M (“The Bf-109K4 is the faster of the two aircraft according to this data”) and the other two do not make the P-47M faster than the Bf-109?

2. If EAS represent the true (verses true airspeed) airspeed of an aircraft, would you say that the two piston power planes are faster than the F-15 and SR-71?


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## Crumpp (Dec 25, 2007)

> Actually, I don't think I have ever disagreed with any of this except the last statement for comparing airspeed at different altitudes with different aircraft using EAS.



I think this statement is self evident and a good indicator.



> SR-71, at Mach 3, 100k ft, TAS = 2048 mph, EAS = 238 mph
> 
> F-15, at 55k ft, TAS = 600 mph, EAS = 209 mph
> 
> Therefore, the Bf-109K4 and the P-47M are both faster than the SR-71 and F-15 because they have a higher EAS.



There is no need for me to be insulting.


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## davparlr (Dec 25, 2007)

Soren said:


> You're right Crumpp but perhaps Davparlr has forgotten some of this. I haven't experienced Davparlr ever being dishonest, just so you know.
> 
> Merry Christmas all!



Soren, because of mutliple discussion we have had, I have gained a high regard for your aerodyamic expertise. I know it would be a pain, but could you review my comments and discuss with me any errors I could have made or if they are confusing?


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## davparlr (Dec 25, 2007)

Crumpp said:


> I think this statement is self evident and a good indicator.
> 
> 
> 
> There is no need for me to be insulting.



I am not asking you to be insulting, I am asking you to exlain an apparent descreptancy. I will make it simpler. Just tell me why you have determined that the Bf-109K4 is faster because of this comparison

440mph / 1.4678<SMOE FL24> = 299 mph EAS
467mph / 1.71295<SMOE FL325 = 272mph EAS

and yet this comparison is disregarded. The calculations are the same, only the conclusion is different. If your statement was true, wouldn't the Bf-109K4 still have a higher EAS?

440mph / 1.4678<SMOE FL24> = 299 mph EAS
451mph / 1.4678<SMOE FL24> = 307mph EAS


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## davparlr (Dec 25, 2007)

Crumpp said:


> You think like you’re in a car.
> 
> Aircraft are machines of the air.
> 
> ...



Okay, lets talk about this at the molecular level. You're in a car at sea level traveling 50 mph. Up ahead is a sign and a single air molecule is hanging around in the air beside it. You stick out your hand and hit the air molecule. You and your hand are going 50 mph and the molecule is moving zero. The collision make a minute impact on your hand. You are now a 10000 ft and ahead of you is a sign and beside the sign is an air molecule not moving. You stick out your hand and strike that air molecule. You hand is going 50 mph realtive to the air molecule (the same closure speed as to the sign), the same speed as it was at sea level. Since the weight is the same for molecule, and the impact speed of your hand on the molecule is the same, the impact pressure of that one molecule is the same as the one at sea level. Lets see, two molecules, same mass struck by a hand going the same speed, 50 mph, therefore, same impact force. The difference in real life, and why the force is different, is because your hand strikes many more molecules at that instant at sea level than it does at 10,000. The speed hasn't changed, only the amount of air molecules struck. It doesn't matter if you are in car or an aircraft, the aerodynamics is the same.


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## Crumpp (Dec 25, 2007)

> F-15 flying at 600 mph TAS at 55,000 ft. Using your calculations the F-15 EAS is 209 mph. Using your logic, the F-15 is flying at 70% of the speed of the Bf-109K4. This is not logical nor aerodynamically true.



It is logical and it is aerodynamically true. 

That is really a crappy comparison too if you know anything about supersonic aerodynamics. The P47 and the Bf-109K are not contending with the same level of drag rise. The rules have changed.

Same goes with your F-15 comparison. It's nonsensical comparison as the P47 and Bf-109 are both subsonic designs.

However we will put on our pretend caps and pretend that there is validity to your argument simply to illustrate the value of EAS.

*Neither the P47 or the Bf-109 can achieve 0 mph EAS at 100K.* _They are unable to produce any power at that altitude._

However aerodynamically, the P47 and Bf-109K are traveling faster through the air. 

The SR-71 requires a large amount of thrust in comparison to either of the WWII fighters. It has much higher drag forces acting on it.



> I am asking you to exlain an apparent descreptancy.



There is no discrepancy. Your taking 1/2 the picture and trying make it the whole picture.

It's a nonsensical argument as explained. 

I think I see where your erroneous thinking has come into this. You think I made a case that the Bf-109K is faster than the P47M, right?

You do think like a gamer. You are not well versed in the basics of aerodynamics. Those are not meant to be insults, just the facts of your behavior.

Assuming the altitude listed for the P47M data represents FTH of the turbocharger system.

It is very easy to gauge general performance trends when we use EAS. That quick SWAG tells me that in general anything below FTH for the Bf-109K it will be faster than the P47M. However, this trend will change as we pass FTH as the Bf-109 does not have as high a ceiling as the P47M.

That is what my SWAG showed. Not some asinine blanket statement.


All the best,

Crumpp


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## Nikademus (Dec 25, 2007)

So.........can anyone add further thought on how maneuverable a 109K is at high altitude in comparison to the P-47? 

oh and Merry X-mas everyone.


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## Erich (Dec 25, 2007)

so Nik did you get any books on the Bf 109K from Klaus ? you need to instead of dependence on what others are telling you and the net.........


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## Njaco (Dec 25, 2007)

Nik, after reading this thread, I'm still confused.


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## Crumpp (Dec 25, 2007)

> I'm still confused.



You should be confused. A wonderful job of muddying up the waters has been done in this thread to the benefit of one.

Now instead of folks learning something, everyone reading this is confused.

Why? A supersonic flow problem such as the one below is well beyond the scope of this thread. That fact it was even used as an example speaks volumes.



> SR-71, at Mach 3, 100k ft, TAS = 2048 mph, EAS = 238 mph
> 
> F-15, at 55k ft, TAS = 600 mph, EAS = 209 mph
> 
> Therefore, the Bf-109K4 and the P-47M are both faster than the SR-71 and F-15 because they have a higher EAS.



The forces the aircraft traveling in the supersonic realm are not on the same scale as what the P47 and Bf-109 are experiencing. We can make no comparison between supersonic and subsonic flight.

It is a nonsensical comparison.

There are some methods of estimating transonic drag rise but none of the work in the supersonic realm. We could SWAG the RAM rise too but that would be useless exercise since our drag rise does not work for supersonic flow. It only works for from the transonic realm up to Mach .95.





All the best,

Crumpp


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## Soundbreaker Welch? (Dec 25, 2007)

Merry Christmas!


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## Nikademus (Dec 25, 2007)

Erich said:


> so Nik did you get any books on the Bf 109K from Klaus ? you need to instead of dependence on what others are telling you and the net.........



Not usually. I always prefer acredited book sources over Google, or what others are telling (or yelling in some cases) However I did just recently spend close to $1000.00 purchasing most of Christopher Shores' series detailing day to day air operations as part of my reserach project. (Including his out of print "Fighters over x" series.) Apologies for the name dropping but as one might imagine, my budget for new book purchases is up for the time being.  I'm not above taking advice or listening to someone who knows what they are talking about or happens to know something I don't. 

As I mentioned in the beginning of the thread, my library purchases also tend to focus on air history and campaigns vs. books dedicated to individual aircraft types. I'd need a whole new bookcase if I did that. Worse....even if i purchased the recommended books, i'm not sure that they would have the info I was curious about as not all do. (for example, the old title I have devoted to USN naval fighters of WWII....it has the expected stats.....ceiling, powerplant specs....max speed etc...but nothing regarding roll and turn rates etc) Should I ever win Lotto however, concerns over the size and cost of my library would go out the window along with my crap job.  

Having come across this site recently, and having read one poster in the Best Fighter III thread give one of the better P-51 breakdowns i've seen recently, I thought maybe someone might have some info on the 109K and how it stacks up.

I didn't expect the responses to be so complicated or etherial however!


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## Nikademus (Dec 25, 2007)

Njaco said:


> Nik, after reading this thread, I'm still confused.



I'm glad I'm not alone. I was starting to feel like the guy Ron White talks about when he says "you can't fix stupid...."  8)


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## davparlr (Dec 25, 2007)

Crumpp said:


> It is logical and it is aerodynamically true.
> 
> That is really a crappy comparison too if you know anything about supersonic aerodynamics. The P47 and the Bf-109K are not contending with the same level of drag rise. The rules have changed.



I won't disagree with you on this on the SR-71. I only wanted to show that no matter how fast your aircraft is going, EAS will drop off with altitude. By the way, I did see that you verified my data for the SR-71. But in general, supersonic comparisons with non supersonic performance is not a safe place to be.



> Same goes with your F-15 comparison. It's nonsensical comparison as the P47 and Bf-109 are both subsonic designs.



I don't agree with you on this. I selected 600 mph TAS because I thought it was subsonic and indeed it is .91. Except for limiting Mach on the prop jobs, if they could produce the same thrust at 55k as they did at the points noted, it is reasonable to assume they could achieve a similar TAS, in other words, maintain the same EAS. In fact, of course the F-15 is considerable larger than these planes, proportionally, it is probably not generating a whole lot more thrust than the piston powered planes at there optimum.



> However we will put on our pretend caps and pretend that there is validity to your argument simply to illustrate the value of EAS.



No doubt about it. But when estimating airspeed performance for an aircraft at various altitudes, thrust available must be considered.



> *Neither the P47 or the Bf-109 can achieve 0 mph EAS at 100K.* _They are unable to produce any power at that altitude._



Exactly! The reason the Bf-109K cannot meet the airspeed of the P-47M at 32k ft is that it is unable to generate the necessary thrust to make the EAS.



> However aerodynamically, the P47 and Bf-109K are traveling faster through the air.



This is where we continue to disagree. In reality, there is only one airspeed for airplane. That speed is the rate at which that aircraft passes a molecule of air, or a mass of molecules of air. When an SR-71 at Mach 3 passes a non-moving (no wind) molecule of air, the speed differential between the molecule and the SR-71 is approximately 2000 mph. or TAS. Now, how those molecules affects the aircraft maneuvering and flight characteristics is another thing. In addition to TAS, that depends mostly on how many molecules are impacting, causing drag, lift, etc. For this kind of performance, TAS is modified by density (no. of molecules in a given volume) and EAS is generated that gives equivalent performance over a constant EAS value. There is nothing in the air that passes the aircraft at the EAS velocity. TAS is real speed, EAS is calculated. You claim all airspeed is calculated. That is usually true because of errors in measureing. However if we could measure the air molecules passing the aircraft directly, say with a laser, which I know they were working on once (I was the responsible engineer for the air data computers for the TACIT BLUE aircraft which is now in the AF museum), it would show TAS and not EAS.



> The SR-71 requires a large amount of thrust in comparison to either of the WWII fighters. It has much higher drag forces acting on it.



Yeah, the supersonic flight tends break down the thrust vs. EAS curve.





> There is no discrepancy. Your taking 1/2 the picture and trying make it the whole picture.
> 
> 
> It's a nonsensical argument as explained.



I will agree with this on supersonic airflow



> I think I see where your erroneous thinking has come into this. You think I made a case that the Bf-109K is faster than the P47M, right?



Right!



> You do think like a gamer. You are not well versed in the basics of aerodynamics. Those are not meant to be insults, just the facts of your behavior.



"The Bf-109K4 is the faster of the two aircraft according to this data."

I am not sure I am the only one who read it that way



> Assuming the altitude listed for the P47M data represents FTH of the turbocharger system.
> 
> It is very easy to gauge general performance trends when we use EAS. That quick SWAG tells me that in general anything below FTH for the Bf-109K it will be faster than the P47M. However, this trend will change as we pass FTH as the Bf-109 does not have as high a ceiling as the P47M.
> 
> That is what my SWAG showed. Not some asinine blanket statement.



Well, it was confusing, especially when I calculated that the EAS of the P-47M was higher at the same altitude where the Bf-109k was calculated.


My argument was (and is) that EAS alone, without the understanding of the thrust available to maintain EAS, is not a valid way to predict aircraft performance at other altitudes.


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## Njaco (Dec 25, 2007)

Nik, I get the feeling only one person has all the answers and the rest of us are just too stupid to know better.

I learnead alots.


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## Crumpp (Dec 25, 2007)

> I selected 600 mph TAS because I thought it was subsonic and indeed it is .91.



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.



> In fact, of course the F-15 is considerable larger than these planes, proportionally, it is probably not generating a whole lot more thrust than the piston powered planes at there optimum.



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.



> In reality, there is only one airspeed for airplane.



Baloney.



> There is nothing in the air that passes the aircraft at the EAS velocity. TAS is real speed, EAS is calculated. You claim all airspeed is calculated. That is usually true because of errors in measureing. However if we could measure the air molecules passing the aircraft directly, say with a laser, which I know they were working on once (I was the responsible engineer for the air data computers for the TACIT BLUE aircraft which is now in the AF museum), it would show TAS and not EAS.



Name one TAS speed where aircraft performance occurs?

You cannot other than Vy. Vy only because of the density relationship with CAS. There is a reason we use EAS for performance comparison. It has been proven mathmatically and by the laws of physics.

What is Vs1 at sea level in TAS? What is Vs1 at 20,000 ft?

For the reader,

L/D ratio and angle of attack is fixed by design. The same L/D ratio occurs at the exact same Angle of Attack every time. Only a design change or a configuration change will alter this relationship. 

There are very good reasons why EAS is used for comparing aircraft performance by engineers.




> My argument was (and is) that EAS alone, without the understanding of the thrust available to maintain EAS, is not a valid way to predict aircraft performance at other altitudes.



That is completely different from your original claim that EAS was not used for aircraft performance comparison. Now you are changing your tune.
 
I don't really care what you claim to have done or worked on. Your grasp of the basics is rickety at best.

All the best,

Crumpp


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## Crumpp (Dec 25, 2007)

You gloss over this:




> Originally Posted by Crumpp
> 
> It is the faster of the two aircraft. Your whole argument is nonsensical.
> Do you understand about the important of dynamic pressure and its relationship to aircraft performance? I really don’t think you have a clue about it.
> ...




In fact you regurgitate the very reasons we use EAS to compare performance. Using EAS eliminates the density effects of our altitude!



> davparlr says:
> *Of course the pressure is higher in the second equation because the medium in which it is traveling is denser (more slugs)!* The value of the force has increased because it requires more effort to go through a denser medium. You can ride in a boat at 10 mph with your hand out and feel a slight pressure from the air. If you put your hand in the water, it would feel it could be snatched off. That is not because you are going faster through the water than through the air, you are not; it is because the water has many times the density of air causing a lot more drag. This also occurs, to a lesser extent, in the air as we go from a higher altitude to a lower altitude. The increasing density of the air causes the force to increase without any change in airspeed.





> 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.*



Read questions 1 and 2. Notice what they want the answer’s in when comparing aircraft performance!

http://www.aer.bris.ac.uk/course_material/1st_year/papers/05aeng11301q.pdf



> it would show TAS and not EAS.



That’s because we cannot navigate without TAS speeds.

All the best,

Crumpp


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## Crumpp (Dec 25, 2007)

I don't see any credible way that anyone who attended an aerodynamics class on any level could forget having to deliver the vast majority of answers in EAS.

All the best,

Crumpp


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## Soren (Dec 25, 2007)

All who are confused please read this article by Professor Dave Esser:
Measuring Air Speeds


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## Crumpp (Dec 26, 2007)

Let's get this discussion back on track.



> Looking for some more in-depth info on this last varient of the venerable 109 series. Also would like some opinions on how it stacks up in high alt combat vs. the P-47D. Done some self research online but so far havn't found enough to satisfy.



What altitude Nik?

All the best,

Crumpp


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## Nikademus (Dec 26, 2007)

30,000 feet or higher. The P-47 is often described as being suprisingly nimble and agile at very high alts thx to it's high wing loading and supracharged big engine. Nothing specific though. The website I linked a few pages back described it as "suprisingly nimble" for a plane it's weight and size but didn't suggest it was "more" nimble or agile than a FW or Bf at similar altitudes.

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.


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## Crumpp (Dec 26, 2007)

> 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.



That is pretty much true for any of the WWII fighter designs that stuck around the entire war. The handling issues stem from the airframe outgrowing its design stability points.

The exact same thing happened to the Spitfire and P51 series too. It takes a design change to expand these limits. Increasing the weights, increases the moments, and affects the handling. It’s just simple physics.

I think this tends to be overemphasized by non-pilots. While it is present and can sometimes be "unpleasant", it does not detract from design performance and none of these changes resulted in a design that was no longer a viable, safe, and controllable aircraft. If it did the design is simply scrapped.

When I say "safe" I am speaking in a relative term as it applies to airplanes!



> 30,000 feet or higher



I might have some engine charts and as a FTH analysis has been done already on both aircraft we can change the power to see the results.

It's not definitive by any means for specific performance but it will most certainly give us performance trends. It is accurate within the realm of significant digits.

All the best,

Crumpp


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## davparlr (Dec 30, 2007)

Crumpp said:


> 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.
> 
> ...



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.

Also, NASA wing drag coefficient for transonic flight for 45 degree wing sweep (F-15) shows very small increase in drag coefficient up to about .94 Mach (see graph).
Of course if that makes you uncomfortable, I could lower the example Mach to .87, which is getting into the realm of commercial jet cruise, with very low transonic effects. Then, at 55kft, we get at TAS of 575 mph and an EAS of 194. Again, from your perspective, the Bf-109k is faster than the F-15 by 100 mph.



> 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.



Remember EAS for the F-15 is only 209 mph, or 181 knots, probably approach speed. The F-15 is not generating a lot of thrust at approach speed, even in level flight, only enough to counter the low drag at that airspeed. I maybe slighty higher due to some transonic drag, but I have already shown that this would not be significant.

Having flown jet aircraft above 45000 ft I can tell you fuel flow is quite low.



> Baloney.



I think it is philosophically correct but is confusing. I won’t try to defend any more than to say that speed is a distance, divided by time the distance is traversed. If a Bf-109k is going 299 mph EAS at 24k ft, in one hour it must go 299 miles, right? 299 miles relative to what? It certainly is not over land in a no wind environment, which would be TAS, or 440 miles. it is not in the air mass, that would be TAS also, 440 miles. In the real physical world made up of air mass and earth distance, EAS has no plane of reference. Neither does IAS or CAS. All of these are just comparisons of total pressure and static pressure with many errors. These errors can be correct to get the real velocity through or over air or ground. If you fly IAS or CAS, or try to apply EAS to get any real distance measured for flying an hour, you have to convert it. Now this doesn’t mean that IAS, CAS and EAS are not important. They do represent the actual aerodynamic loads on an aircraft and, as a result, is vital for how an aircraft maneuvers and handles, and therefore, either IAS or CAS is mandatory in flying the aircraft. The wings only see and react to, IAS, CAS, EAS, the aircraft as a whole, in relating to the world, either in the air or over the ground, only knows TAS.



> Name one TAS speed where aircraft performance occurs?



It tells you the actual velocity that the aircraft is going through the air mass. As a result:
1. With wind speed, you can calculate your speed over the ground.
2. With fuel flow and wind speed You can calculate how far you can go with the fuel you have on board.
3. You can calculate how long it will take you to reach a destination.
4. You can compare your aircraft performance to another. For instance, If You are in a P-47M at 32.5k ft and you see a Bf-109K below you at 24k, and you know your max TAS is 467 mph at 32.k, and you know his max TAS at 24k is 440 mph, you know that even though his EAS if higher than yours, it is useless information because, with your higher TAS, you can catch him without losing altitude. On the other hand, if you were in the Bf-109K and saw the P-47M was ahead of you, you would know that, if he saw you, you could never catch him, even if you didn’t climb, even with your higher EAS, because you have a lower TAS.

You can do none of the above with EAS.



> What is Vs1 at sea level in TAS? What is Vs1 at 20,000 ft?



A lot faster since to maintain the same dynamic pressure at Vs1(sl), Vs1(20k) must be much higher in the low density environment. See discussion on this later. 




> There are very good reasons why EAS is used for comparing aircraft performance by engineers.



I have no argument now, or ever, with EAS being used for predicting aircraft performance such as stall speeds, maneuverability, climb rates, etc. My argument is that, one, you can’t predict aircraft airspeed performance at a higher altitude using EAS alone without hp data, and two, a higher EAS does not mean you are going faster than another aircraft at a higher altitude, but lower EAS.




> That is completely different from your original claim that EAS was not used for aircraft performance comparison. Now you are changing your tune.



This is disingenuous. I have never claimed in this post that I thought EAS was NOT used for aircraft performance comparisons other than airspeed comparisons at different altitudes. I have NOT changed my tune.

You said



> “EAS is useful for performance comparisons”



I replied “This is true for some aircraft performance parameters, just not for airspeed comparison at different altitudes”

You later said,



> “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.
> 
> ...



I said “Actually, I don't think I have ever disagreed with any of this except the last statement for comparing airspeed at different altitudes with different aircraft.”

Somehow, you have twisted my comments to imply I think EAS is worthless when I have not.


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## davparlr (Dec 30, 2007)

Crumpp said:


> You gloss over this:



Believe me, this misapplication of mathematical logic is difficult to ignore. You ignored my answer so I will restate it. Here is your work.



> Well if we compare our DYNAMIC PRESSURE between these two aircraft using TAS:
> 
> P47 at FL325 467mph * 1.47 = 686fps
> 
> ...



Note here that there is only two speed values (ft/sec) expressed. No others, and these are 686 fps for the P-47 and 647 fps for the Bf-109. There is density (slugs/ft^3), there is pressure (lbs/ft^2). There is no other reference to speed noted. The speed of the P-47 is 686 fps and the speed of the Bf-109 is 647 fps. No more, no less.



> “Dynamic pressure is a function of speed:”



This is not totally true, is it?

Dynamic pressure is a function of speed (ft/sec) *AND density (slugs/ft^3).* 

In other words, mathematically speaking, *dynamic pressure can go up by increasing density and not changing speed.* Increased dynamic pressure can reflect an increase if only density is increased and with NO increase in speed! This is basically what is reflected in these two equations.





> 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.



Okay, let’s use your formula 
q=.5r(sl)V(sl)^2

Lets use an aircraft going 300 mph EAS at SL and we want to fly at 300 mph at 10k. So, since EAS(SL) = EAS(10k), and since equal EAS means equal dynamic pressure, we have q=q or .5*r(sl)*V(sl)^2 =.5*r(10k)*V(10k)^2

Plugging in the known values, we get,

.5*.0023769 (SLugs/ft^3)*441 (ft/sec)^2 =.5*.001756 (slugs/ft^3)*V(10k)^2

Then {(.0023769*441^2)/.001756}^.5 = V(10k)

Or V(10k) = 513 ft/sec or 349 mph

So, in order to have a dynamic pressure at 10k that you have at SL, V(10k) must be 513 fps. This is greater than V(sl) at 441 ft/sec. In other words, to keep your dynamic pressure constant as you get into a thinner atmosphere (less dense), you must increase V(10). This is mathematically correct and is horse sense. As resistance gets less due to thinner air, speed must increase to maintain the same dynamic pressure.



> Of course we can ignore the science and just go ahead with a silly comparison of airplanes under very different conditions using TAS.



Or, we could ignore mathematics and use EAS for airspeed comparison.

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. 




> Read questions 1 and 2. Notice what they want the answer’s in when comparing aircraft performance!



I never argued these points. Check my posts. EAS is what you want to work issues of climb, turn rate etc. What I have argued and only the items I have argued is as follows:

1. While EAS is very helpful in comparing aerodynamic performance, like stall, turn rates, etc., at various altitudes, it cannot predict an aircraft’s airspeed performance at a different altitude without knowledge of horsepower/thrust available.

2. For aircraft at different altitudes, a larger EAS does not necessarily mean a higher airspeed. Something I think is intuitively obvious and something I have proved mathematically, and demonstrated by multiple examples!





> That’s because we cannot navigate without TAS speeds.



Huh? And what does this have to do with the price of tea in China? It is because the air mass is passing by at TAS.


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## magnocain (Dec 30, 2007)

wow davparlr, you did your homework.


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## Soren (Dec 30, 2007)

Ok, let me straighten things out here;

First of all the reason Crumpp wants to use EAS for comparison reason is like he says _*"using EAS puts the aircraft under the same conditions"*_, which is very true when you want to compare the maneuverability of a/c. AFAIK Crumpp never claimed that because two aircraft feel the same EAS then they're going just as fast, he never claimed that.

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.


For the newcomers:

EAS = Estimated Air Speed
TAS = True Air Speed
IAS = Indicated Air Speed
CAS = Calibrated Air speed


PS: Davparlr, its the Ta-152H, not the Ta-154, the Ta-154 never got to see service.


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## HoHun (Dec 30, 2007)

Hi Davparlr,

>Also, NASA wing drag coefficient for transonic flight for 45 degree wing sweep (F-15) shows very small increase in drag coefficient up to about .94 Mach (see graph).

Is this graph from a NACA/NASA report? In that case, I'd very much appreciate a pointer to the report because it is interesting for me in a completely different context.

Thanks in advance! 

Henning (HoHun)


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## Nikademus (Dec 30, 2007)

yea! bump to the front.


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## Soren (Dec 30, 2007)

Nik, do you understand better now or are you still confused ?


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## davparlr (Dec 30, 2007)

Soren said:


> 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.



He may have not made that statement but he did say the equivalent.

Crumpp stated 


> 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
> ...



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
> 
> ...



Do you agree here also? Or do you think maybe dynamic pressure is also a function of air density?




> 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.



This exactly what I have been stating, maybe not a fluent, but the same and I have not varied from it.

"Now this doesn’t mean that IAS, CAS and EAS are not important. They do represent the actual aerodynamic loads on an aircraft and, as a result, is vital for how an aircraft maneuvers and handles, and therefore, either IAS or CAS is mandatory in flying the aircraft. The wings only see and react to, IAS, CAS, EAS, the aircraft as a whole, in relating to the world, either in the air or over the ground, only knows TAS."

and, "So, in order to have a dynamic pressure at 10k that you have at SL, V(10k) must be 513 fps. This is greater than V(sl) at 441 ft/sec. In other words, to keep your dynamic pressure constant as you get into a thinner atmosphere (less dense), you must increase V(10). This is mathematically correct and is horse sense. As resistance gets less due to thinner air, speed must increase to maintain the same dynamic pressure."



> 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.



So, tell me, what did he say that passed me by? Remember I was never arguing the benefits of EAS on comparisons of maneuvering performance, only his comments in the above quotes relative to airspeed comparison.



> PS: Davparlr, its the Ta-152H, not the Ta-154, the Ta-154 never got to see service.



Sorry, late night typo. I know better.


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## Soren (Dec 30, 2007)

Davparlr,

With all due respect you're nitpicking right now.



> Do you agree here also? Or do you think maybe dynamic pressure is also a function of air density?



Notice the 'r' in the equation Crumpp presented:

q=.5rV^2

Speed can be different at the same altitude, density can not, density is stuck to alt - hence Crumpp's comment. This seems to have went passed your nose.

And now I have a question Davparlr;

AFAIK you're an engineer, but I've never seen you claim that you were an aeronautical engineer, so are you ? Just to make it clear.

Finally don't take the above as a blow to your nose davparlr, I'd like to point out that I can't see where I disagree with both of you on the subject at hand, so I'm not taking any sides here, my perception of both of you is that you're both unbiased honest individuals.

Lets keep the debate friendly people.


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## Crumpp (Dec 30, 2007)

> 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.*



Once again you have no formal education in Aerodynamics and that is obvious. 





The exact onset of Drag rise due to compressibility is not a set standard in Aerodynamics. However it universally agreed upon that by Mach .8 you will be encountering the effects. Commonly it is applied at Mach .3 and above.

Here is the one method of estimating that drag rise due to compressibility:









> > This is not totally true, is it?
> >
> > Dynamic pressure is a function of speed (ft/sec) AND density (slugs/ft^3).
> 
> ...



TAS is EAS *with density effects*.

It's just basic aerodynamics. 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. Anyone trained in aerodynamics would recognize the density differences and understand we must be using TAS.

It would also be quite obvious to you as EAS is corrected for density effects by definition. That is why it is used for comparison of all aircraft performance!

*Therefore in our dynamic pressure equation, only Velocity can change as our density is fixed when using EAS.*

Once again, this is a given by the very definition of EAS. Where did you go to school and take Aerodynamics again?



> 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.



The Ta-152 can travel at some 405KTAS at *FTH* at 29,527ft. This means it is doing 251 KEAS and is a much faster airplane than the P6A.

Now if we do go to FL41 then our Ta-152H is only producing ~700PS at 12.5KM. Using your numbers, 172mph EAS is not bad considering we are using only 1/3 the Ta 152H's power production capability at an altitude the P6A is incapable of producing any power at all.

There is no misunderstanding nor are we talking past each other. You do not understand aerodynamics. Your education is incomplete and has failed to link key concepts together for you.

All the best,

Crumpp


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## evangilder (Dec 30, 2007)

Enough of the personal attacks, Crumpp. Any more of them and I will lock this thread.


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## DerAdlerIstGelandet (Dec 30, 2007)

You beat me to the punch Eric.

Seriously guys everyone can learn from one another in a peaceful manner.


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## Crumpp (Dec 30, 2007)




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## Crumpp (Dec 30, 2007)

> Enough of the personal attacks, Crumpp. Any more of them and I will lock this thread.



It's not a personal attack, Evan. It is just facts. Saying someone is ignorant is not the same as claiming they are stupid. Ignorance is just a lack of correct information. We are all ignorant depending on the circumstances! 

If someone comes along and claims that the moon is made of green cheese are you attacking them when you say, "No, you are ignorant of the facts. While some fairy tales my claim the Moon is made of green cheese, we know from science it is not".

It also becomes a fact and not a personal attack when we say such claims do not come from a formal education in astronomy.

All the best,

Crumpp


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## evangilder (Dec 30, 2007)

> 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.
> 
> ...



Since you clearly cannot talk rationally, and think that those statements are NOT a personal attack, I am locking this thread. You clearly cannot be civil.


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