Author Topic: Fw190 D-9 2.03 ata  (Read 6977 times)

Offline Crumpp

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« Reply #75 on: June 13, 2005, 03:07:19 PM »
How do you explain the NACA drag test on the P51B Niklas posted.  Thanks for posting that Niklas BTW, I had forgotten about that investigation.

It clearly states "good agreement between windtunnel test and flight test".  

The report I saw from squadron complaints was in the 8th AF archives.  I will be heading back there in a few weeks and will grab a copy of it.  I did not get a copy because it was of little interest to me at the time.

All the best,

Crumpp
« Last Edit: June 13, 2005, 03:09:26 PM by Crumpp »

Offline LRRP22

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« Reply #76 on: June 13, 2005, 04:20:08 PM »
How do you explain AVIA 6/10618?  I think a report that deals with direct testing of operational aircraft has a lot more relevance to the discussion than a prop-less, unpowered and empty example towed to altitude and dropped over the desert.  The truth is that we have controlled tests of an operational Mustang in documented conditions.  This test showed that improving the paint surface from "very poor" to something approaching new condition yielded a 12 mph speed gain.  Even if the RAE underestimated the amount of speed loss caused by the wing racks (8 mph), they could, at most, be off by a couple of mph.  Both the USAAF and RAF found that wing racks cost the P-51 12 mph around 10,000 ft and up to 14 mph above 20-25,000 ft.  The RAE says 8 mph at sea level which is certainly *very* close to the actual value.

Just to get this straight: Is it your contention that NAA and USAAF P-51 performance numbers were derived from wind tunnel estimates and not from actual testing of production models?  Or is it that you believe the tested numbers were derived from exceptional, custom built examples?  You might be able to make that argument for the NAA numbers, but the fact is that the USAAF and RAF always tested from delivered production batches and, in the case of the P-51, the USAAF and RAF data invariably equalled or exceeded the NAA numbers.  

Further, do you believe that the P-51 ever achieved actual laminar flow during flight?  There really is no debate about that- it didn't.  Even in the late 50's the only way to achieve actual laminar flow involved a wierd system of boundary layer vents in the wing and a compressor system to pump air over the wing.

I'll be looking for the 8th AAF report...

Regards,
Brent




Quote
Originally posted by Crumpp
How do you explain the NACA drag test on the P51B Niklas posted.  Thanks for posting that Niklas BTW, I had forgotten about that investigation.

It clearly states "good agreement between windtunnel test and flight test".  

The report I saw from squadron complaints was in the 8th AF archives.  I will be heading back there in a few weeks and will grab a copy of it.  I did not get a copy because it was of little interest to me at the time.

All the best,

Crumpp
« Last Edit: June 13, 2005, 04:41:58 PM by LRRP22 »

Offline LRRP22

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« Reply #77 on: June 13, 2005, 04:52:48 PM »
Crumpp,

An honest question: how much speed, in mph, do you think the average operational P-51 lost compared to published USAAF figures?  How many mph do you think the average P-47, Spitfire or Focke Wulf suffered?  

Regards,
Brent

Offline Crumpp

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« Reply #78 on: June 13, 2005, 05:19:54 PM »
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This test showed that improving the paint surface from "very poor" to something approaching new condition yielded a 12 mph speed gain.


Seems they skipped the effect of the new exhaust stubs:



Which would change power, drag, and exhaust thrust.


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Is it your contention that NAA and USAAF P-51 performance numbers were derived from wind tunnel estimates and not from actual testing of production models? Or is it that you believe the tested numbers were derived from exceptional, custom built examples? You might be able to make that argument for the NAA numbers, but the fact is that the USAAF and RAF always tested from delivered production batches and, in the case of the P-51, the USAAF and RAF data invariably equalled or exceeded the NAA numbers.


It is my contention that the NACA was correct in its conclusions:

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For the best performance, manufacturing tolerances had to be perfect and maintenance of wing surfaces needed to be thorough.


And that the 8th AF experienced this historical fact recorded by the NACA:

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The rush of mass production during the war and the tasks of meticulous maintenance in combat zones never met the standards of NACA laboratories.


As with any manufacterer who subcontracts, quality control issues will arise.  Especially in the begining when subcontrators are tooling up and learning to make the product.

Add in the difficulties of maintaining the high degree of surface finish the Mustang required to achieve it's stated performance and it is not a surprise that the end users would voice some complaints.  

http://www.hq.nasa.gov/office/pao/History/SP-4406/chap2.html

The Mustang was very sensative to surface imperfections as covered in this report which is seeking to make general conclusions about the design and not specific ones about a modified aircraft as in AVIA 6/10618.

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The tests results show that the drag characteristics of the test airplane can be predicted with satisfactory accuracy from tests in the Ames 16-foot high-speed wind tunnel of the Ames Aeronautical Laboratory at both high and low Mach numbers.  It is considered that this result is not unique with the airplane.


http://naca.larc.nasa.gov/reports/1948/naca-report-916/

All the best,

Crumpp

Offline Crumpp

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« Reply #79 on: June 13, 2005, 05:24:19 PM »
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An honest question: how much speed, in mph, do you think the average operational P-51 lost compared to published USAAF figures? How many mph do you think the average P-47, Spitfire or Focke Wulf suffered?


It depends on the drag characteristics of the aircraft in question.  It is not the same for each aircraft.  Some planes make larger gains than others.

That is what I explained earlier with the P&H scans and documents.  You should read up more on aerodynamics.  It can add some wonderful insights into the history of these aircraft.

All the best,

Crumpp

Offline LRRP22

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« Reply #80 on: June 13, 2005, 06:56:41 PM »
Quote
Originally posted by Crumpp
Seems they skipped the effect of the new exhaust stubs:

Which would change power, drag, and exhaust thrust.


Crumpp,

I've already posted the information regarding the exhaust stacks.  Two tests were conducted after the paintwork was cleaned up- the first before the exhaust stacks were replaced which yielded 403.5 mph at sea level, and one after the exhaust stacks were replaced which yielded 405 mph.  +1.5 mph- that is not disputable.    If you choose to discount that fact, so be it.




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It is my contention that the NACA was correct in its conclusions:


Yes, but its conclusion was that the quality of airflow achieveable with a wooden 1/3 scale model in a wind tunnel wasn't attainable by production airframes because of limitations in production methods and operational wear and tear.  It says nothing regarding squadron performance vs. manufacturer/service test performance.  That is a logical leap you have chosen to take, not NACA.  After all, the tested aircraft were subject to the same production limitations and quality  as any other example.  Service test performance numbers were based on production airframes that were pulled at random  from delivered production batches.    
 
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And that the 8th AF experienced this historical fact recorded by the NACA:


That may, or may not be the case.  I supect that when you find the above mentioned report, it is going to be far less damning than you seem to imply.  
 

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As with any manufacterer who subcontracts, quality control issues will arise.  Especially in the begining when subcontrators are tooling up and learning to make the product.

Add in the difficulties of maintaining the high degree of surface finish the Mustang required to achieve it's stated performance and it is not a surprise that the end users would voice some complaints.



Please make reference to which stated performance.  Again, manufacturing defects were already built-in to the service trial numbers.      


Quote

The Mustang was very sensative to surface imperfections as covered in this report which is seeking to make general conclusions about the design and not specific ones about a modified aircraft as in AVIA 6/10618.


Laminar flow was very sensitive to surface imperfections, prohibitively so.  The Mustang's laminar profile wing was less so.

I am a bit befuddled as to why you patently dismiss the results of a professionally conducted and documented service test report, yet extrapolate deep meaning from some general comments that don't specifically address the issue at hand.


I know you don't like to deal in specifics but, again, please tell me just how much slower you think a field worn P-51 should be vs. other fighters in the same condition.  I'll settle for a range, but you must be able to quantify this disparity to some degree.  It's my contention that any differences would be minor while you seem to believe that they were profound.


.
« Last Edit: June 13, 2005, 07:01:17 PM by LRRP22 »

Offline LRRP22

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« Reply #81 on: June 13, 2005, 06:58:35 PM »
Quote
Originally posted by Crumpp
It depends on the drag characteristics of the aircraft in question.  It is not the same for each aircraft.  Some planes make larger gains than others.

That is what I explained earlier with the P&H scans and documents.  You should read up more on aerodynamics.  It can add some wonderful insights into the history of these aircraft.

All the best,

Crumpp


 

Please spare me the condescension.  


.

Offline Crumpp

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« Reply #82 on: June 13, 2005, 08:24:47 PM »
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Please spare me the condescension.


Honestly I was not trying to be condescending.  It is just that you do not seem to understand some of the theory.

Evidenced by your statement below:

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I've already posted the information regarding the exhaust stacks. Two tests were conducted after the paintwork was cleaned up- the first before the exhaust stacks were replaced which yielded 403.5 mph at sea level, and one after the exhaust stacks were replaced which yielded 405 mph. +1.5 mph- that is not disputable. If you choose to discount that fact, so be it.


Yes.  I have seen this.  

Tell me:

How much is lost to extra drag of the exhaust stubs?

How much is gained due to power gains of larger exhaust?

How much exhaust thrust is added over a normal P51?


We know the end result but we do not know the relationship from this graph.  Nor was it calculated in the report.

And this statement:

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Increased cooling drag comes in addition to drag related to surface slickness, not in lieu of it.


Which I already showed you that cooling drag and form drag are all part of the total drag.

The larger a component is the greater the effect of it's reduction.

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Please make reference to which stated performance. Again, manufacturing defects were already built-in to the service trial numbers.


Not likely as evidenced by the NACA report's use of a high quality aircraft submitted for testing by North American.

All the best,

Crumpp
« Last Edit: June 13, 2005, 08:28:24 PM by Crumpp »

Offline LRRP22

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« Reply #83 on: June 13, 2005, 09:13:40 PM »
Quote
Originally posted by Crumpp
Honestly I was not trying to be condescending.  It is just that you do not seem to understand some of the theory.

Evidenced by your statement below:


Well Crumpp, If I didn't know better I would call that more condescension.

There is no "theory" involved in the fact that you claimed the changes made to the exhaust stacks had an unknown effect of the increaded performance.  That statement is patently absurd considering the fact that we know exactly how much extra speed was gained: exactly 1.5 mph.  'Extra Drag' caused by the very slightly larger exhaust stacks sounds like grasping at straws, Crumpp.  

If I need to read up on aerodynamics, you need to read up on logic- your statements just don't add up.   Sound logic and observation would tell you that  that the change in exhaust stacks is irrelevant to the topic at hand: The 12 mph gain in speed from paint restoration occurred before the exhaust stacks were replaced.

Please, quit being obtuse.  You have been presented with hard data from an infinitely credible source that you refuse to accept, period.

Reards,
Brent

Oh BTW, all production P-51's were 'high quality'.

Offline Crumpp

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« Reply #84 on: June 13, 2005, 10:18:42 PM »
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Please, quit being obtuse. You have been presented with hard data from an infinitely credible source that you refuse to accept, period.


It's not being obtuse to take more than one source.

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T'Extra Drag' caused by the very slightly larger exhaust stacks sounds like grasping at straws, Crumpp.


The change in performance is known.  It is the effect on the forces that is not.  Is that hard to understand?

Mute point anyway as this modification did not see production.  However my questions clearly showed your lack of understanding of the science.

You still do not understand the relationship of drag forces and want to hold one example up as typical of the entire series.  

Explain how the RAE is more credible than the NACA or the manufacturer of the aircraft?

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Oh BTW, all production P-51's were 'high quality'.


Sure they were, otherwise the NACA's would not have had to quantify their findings on Mustang performance.

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The rush of mass production during the war and the tasks of meticulous maintenance in combat zones never met the standards of NACA laboratories.


http://www.hq.nasa.gov/office/pao/History/SP-4406/chap2.html

All the best,

Crumpp

Offline LRRP22

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« Reply #85 on: June 14, 2005, 12:45:59 AM »
Quote
Originally posted by Crumpp
It's not being obtuse to take more than one source.


Crumpp,

It is in fact grossly obtuse to take data that directly addresses the issue of squadron service performance and discard it in favor of general comments from another source that only very indirectly address the subject at hand.  Obviously, since it doesn't fit your agenda, you have no use for it.  Perhaps you should take a more objective approach to selecting and weighting your sources.  

Since you can't seem to accept the idea that AVIA 6/10618's expressed purpose was to test the expected performance of average squadron aircraft:



 


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The change in performance is known.  It is the effect on the forces that is not.  Is that hard to understand?


Please don't lecture me on understanding.  You are showing a willful lack of understanding of the information provided to you.  There is no mysterious alchemy involved here- no secret science that I am not a party to.  Quite simply, a Mustang III (FB377) pulled directly from operational service (316 Sqn) achieved 383 mph at sea level with wing racks in place and a very  poor surface condition.  That same airplane, at exactly the same power setting, and under the same controlled and corrected test conditions achieved 403.5 mph after the wing racks and the small bracket at the base of the VHF aerial were removed, and the very poor surface condition restored.  The Royal Aircraft Establishment at Farnborough, an exceptionally qualified testing institution, attributed 8 mph of the increase to the removal of the wing racks, 1/2 mph to the removal of the aerial bracket and 12 mph to the resoration of the badly degrade paint surfaces.  In all other ways the airplane was identical.  

Your attempts to obfuscate the results with repeated referrals to the exhaust stubs and resulting exhaust thrust ring hollow, I'm afraid.  Further, I'm sure the realization that a well-used squadron service Mustang III with a six coats of badly chipped paintwork was faster than the fastes production Focke Wulf doesn't sit well with you, either.

Your patronizing attempts to convince me that I'm just too thick to understand the forces at work here are just a way for you to avoid directly addressing the findings of the report.   The report doesn't support your premise so you want simply to ignore it.  



Quote

Mute point anyway as this modification did not see production.  However my questions clearly showed your lack of understanding of the science.

You still do not understand the relationship of drag forces and want to hold one example up as typical of the entire series.


I'm glad that you have finally accepted that the larger Spitfire-type exhausts fitted are moot to this argument.  After all, the increase in speed attributed to the cleaned-up surfaces was determined before the exhaust stacks were replaced. It is you who exhibits a shocking lack of understanding of logic and reason here, Crumpp.   And once again Crumpp, it was the Royal Aircraft Establishment, not me, that held this example as representative of the average operational aircraft.  For the last time, either tell me why they were wrong and you are right, or finally accept the uncomfortable truth.  


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Explain how the RAE is more credible than the NACA or the manufacturer of the aircraft?


I never said the RAE was more credible than NACA.  Unfortunately for your argument, NACA never performed tests of operational P-51's expressly designed to determine how much speed could be gained in squadron service through a number of quantified actions.  The Royal Aircraft Establishment, however, did.

 
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Sure they were, otherwise the NACA's would not have had to quantify their findings on Mustang performance.


You can post that link until you're blue in the face, but that still won't cause the document to say something that it doesn't.  You want to believe that it says P-51's taken on charge by the USAAF and RAF were of a much lower quality than the ones experimented on by NACA.  It doesn't.  It simply states that the manufacturing technologies of the day  were not capable of producing the type of surface smoothness that was required to achieve laminar air flow in the wind tunnel.  Even if the production tolerances were capable in that manner, it wouold have been impossible to maintain that surface quality in operational surface.   Is it suprising that a production line, even a very capable one, was not capable of assembly hundreds of parts made from different materials with the same level of precision as the 1/3 and 1/4 scale  hand-made mahogany and metal  wind tunnel models.  Even these custom creations with five layers of hand-rubbed lacquer only achieved laminar flow in brief fits and starts.  What's so hard to understand about that?      

Finally, I'm sure you will take no comfort from the fact that none of the USAAF's or RAF's official P-51 speed performance results were ever quoted from NACA data.

Regards,
Brent Erickson

Offline moot

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« Reply #86 on: June 14, 2005, 01:04:23 AM »
This is about the D9 engine, right?
Hello ant
running very fast
I squish you

Offline Kurfürst

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« Reply #87 on: June 14, 2005, 05:08:48 AM »
Yeah but as usual LRRP2 got into his favourite agenda about that single stripped down Mustang, represenative of all.
Reminds me when Mike cried all over the place about that weirdo +25lbs Spit on the same graph.
The Messerschmitt Bf 109 Performance Resource Site
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Offline Crumpp

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« Reply #88 on: June 14, 2005, 05:49:23 AM »
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Lrrp says:

Please, quit being obtuse. You have been presented with hard data from an infinitely credible source that you refuse to accept, period.


Is the NACA not a credible source?  

I fully accept the RAE report, LRRP2.  It is you who refuses to acknowledge the NACA findings.  If I jumped to bait everytime I came across one report...well, my book would say the FW-190 flew around with air to air guided missiles in the Geschwaders.


I just don't understand how you can ignore that FACT that the NACA concludes wartime performance testing of the P 51 was not representative of a frontline fighter.

All of the NACA's and North American's testing was designed to represent a frontline fighter at the time as well.  

That is why it is called a "mistake".

Why don't you post the entire report instead of just piecemeal, BTW.  It would make it easier to discuss.  Having many PRO documents myself, I understand the expense and would gladly trade you a document of equal value.

All the best,

Crumpp
« Last Edit: June 14, 2005, 06:06:32 AM by Crumpp »

Offline gripen

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« Reply #89 on: June 14, 2005, 05:55:08 AM »
Quote
Originally posted by Crumpp

I just don't understand how you can ignore that FACT that the NACA admits wartime performance testing of the P 51 was not representative a frontline fighter.


Could you please show where NACA did such statement.

gripen