Actually Kurfurst write "During the tests, 1.3-1.32 ata and 2540 RPM was realized, though such small variations were within tolerance, the lower RPM and/or other factors appear to have somewhat impaired the supercharger`s performance, and thus may have reduced altitude performance, as seen from the performance curves : the rammed rated altitude of 6,3 km was considerably below not only the nominal value (of 7 km) of the DB 605 A, but also the typically obtained, avarage 6,6-6,7 km rated altitude"
Greg strikes again - Bf 109G-6 was so slow compared to P-51D
- Thread starter drgondog
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Hi,
I am not going to join this argument. However, there are a couple of points I would make. Reference the 2 Stage Merlin, you should be specific with the British terms. The Merlin had a small water passage in the casing between the first and second stages, although I don't recall it being much referenced and it would only make a very small change of mixture temperature. Possibly this was more for the benefit of the casting or materials and impellor/case fit.
Edit: You can see the waterpassage in post #13 by Shortround6, marked "Interstage water cooling passages".
The Merlin Intercooler is how R-R described the large heat-exchanger after the supercharger.
Now, DB 605 A performance. It should be understood that the DB 605 A/B were limited to their 100% rating between Summer 1942 and about Autumn 1943. That meant a reduced Max ata and RPM of 1.30/2600. Only after the engines were repaired with better valves, pistons, sparkplugs and injectors etc was the full rating of 110% restored, that gave a 1.42/2800 performance upto rated altitude and as helped by RAM pressure to give a higher rated altitude.
The German performance tables are out there but, they often relate to the lower 1.30/2600 power.
Cheers
Eng
I am not going to join this argument. However, there are a couple of points I would make. Reference the 2 Stage Merlin, you should be specific with the British terms. The Merlin had a small water passage in the casing between the first and second stages, although I don't recall it being much referenced and it would only make a very small change of mixture temperature. Possibly this was more for the benefit of the casting or materials and impellor/case fit.
Edit: You can see the waterpassage in post #13 by Shortround6, marked "Interstage water cooling passages".
The Merlin Intercooler is how R-R described the large heat-exchanger after the supercharger.
Now, DB 605 A performance. It should be understood that the DB 605 A/B were limited to their 100% rating between Summer 1942 and about Autumn 1943. That meant a reduced Max ata and RPM of 1.30/2600. Only after the engines were repaired with better valves, pistons, sparkplugs and injectors etc was the full rating of 110% restored, that gave a 1.42/2800 performance upto rated altitude and as helped by RAM pressure to give a higher rated altitude.
The German performance tables are out there but, they often relate to the lower 1.30/2600 power.
Cheers
Eng
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As you can see from the testtable I posted, somehow Kurfürst succeeded to pick up the real RPM but not the real altitude which was 6,420 m, The altimeter in the MT-215 showed 130 - 100 m too low figure and the tachometer 40 rpm too high figure. The max power used was that of Steig- und Kampfleistung, which was the highest allowed at that time.
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- #24
drgondog
Major
I remember now, the context. What I took at face value 60 years ago, I now question the statment "the skinfriction drag and induced drag as minimum limit of the useful drag, the efficiency of the Me-109 is but 40%".
Specifically he defines Skin Friction = 33%, and Induced Drag =7% = 40% of the total as Useful (Duseful) Drag
If you examine the tabulation above (12) Naero=Duseful/Dtotal, notice that "Skin Friction drag (smooth surface) =33% and Induced drag = 7% for the total of the two 'useful". He postulates by eliminating Surface Roughness (15%), Exposed Parts (33%), Interference Drag (6%), Influence of Compressibility (6%) as driving the sum of those components to from 60% to zero.
The slight caveat "This figure indicates that more than half of the total drag of this airplane coould be theoretically be avoided due to extremely clean design and faultless construction of skin and details". If the 'remaining 60% could include not only the surface roughness (entirely), but also magically all exposed surface parts (Radiator scoops, Carb duct, canopy, radio masts, gun ports), Interfernce drag, (wing.fuse attach) espcially) as well as Compressibility (7%), you not only have eliminated all necessary features to take flight, attach a wing - but also re-write physics and aerodynamics to eliminate compressibility.
The last point (compressibility) for he 109G example is for .55M at 22000 feet. At 22000 feet, 500mph, CDm factor for drag rise applied to CDp for th very efficent P-51 wing is about 1.5X of the CDp for .55M
I suppose the Bf 109K came closest to Hoerners' vision.
S&K rpm would be not 2600'? i don't find the trouble with the tachometer in the report where is?
6420 is ever a bit lower
Hello Vincenzo
Yes, the S&K rpm should be 2600 rpm.
I could post the page from the test report as an attachment but I don't think it's worth it. The text just really states the fact and I don't think more than a couple of members of the site know Finnish. But in the test table I posted, all the values in the columns with a small a are instrument readings and the columns without them are the true ones. So one can see that the tachometer showed 40 rpm too high readings.
Yes, the S&K rpm should be 2600 rpm.
I could post the page from the test report as an attachment but I don't think it's worth it. The text just really states the fact and I don't think more than a couple of members of the site know Finnish. But in the test table I posted, all the values in the columns with a small a are instrument readings and the columns without them are the true ones. So one can see that the tachometer showed 40 rpm too high readings.
For interest, the Daimler-Benz figures for the DB 605 A show the following details for the engine Rated Altitude, at S u. K (1.30/2600) with varying additional Ram pressure.
0 Kg/m2 =5800m. @1250PS.
400 Kg/m2 =6400m. @1240PS.
800 Kg/m2 =7150m. @1230PS.
1200 Kg/m2 =7800m. @1220PS.
The altitudes and powers here are read off a graph. I believe that these additional Ram pressures will be at the supercharger impeller face and are not factored for intake efficiency.
Cheers
Eng
Hello Vincenzo
In the original test report the table is on the page 18 and A. Mittarien tarkistus./A. Istrumentation check. on the page 20. and 3. Engine gauges is on the same page.
In ww1 Germany faced similar raw material shortages with ww2. Still was able to produce very competitive fighters to the last day of the war. Fokker dvii and dviii, siemens-suckert DV etc.
In ww2 , from late 1941 , Germany s fighters were badly outperformed by the western fighters. Despite the great potential of both the bf109 and fw190 , the final products that was delivered to the fighter wings were sitting ducks for the spitfires, Mustangs,p47s etc. Unreliable engines, poor building quality, strange aerodynamic choices, poor projects management, lack of two stage superchargers, terrible sacrifice of performance in order not to disrupt the production numbers, unreasonable armament requirements resulted in inferior fighters beyond any hope
A good question is why it took the western air forces 4 years to defeat LW given the huge advantage they possessed not only in numbers but in quality as well.
Really , an American pilot that entered the fight in 1944 , was very easy to score 5-10 kills even if he was not particular talented . If he could be fast enough to score before his comrades. Strafing was the dangerous mission.
On the other hand , even a single kill against an Anglo American fighter in 1944-45, was an amazing succes for a German pilot. The average operational german fighter of the era was 80-100 km/h slower than the p51,spit xiv ,spit ix 25lbs, tempest, p47m , p38l, la7 ,yak3,
In ww2 , from late 1941 , Germany s fighters were badly outperformed by the western fighters. Despite the great potential of both the bf109 and fw190 , the final products that was delivered to the fighter wings were sitting ducks for the spitfires, Mustangs,p47s etc. Unreliable engines, poor building quality, strange aerodynamic choices, poor projects management, lack of two stage superchargers, terrible sacrifice of performance in order not to disrupt the production numbers, unreasonable armament requirements resulted in inferior fighters beyond any hope
A good question is why it took the western air forces 4 years to defeat LW given the huge advantage they possessed not only in numbers but in quality as well.
Really , an American pilot that entered the fight in 1944 , was very easy to score 5-10 kills even if he was not particular talented . If he could be fast enough to score before his comrades. Strafing was the dangerous mission.
On the other hand , even a single kill against an Anglo American fighter in 1944-45, was an amazing succes for a German pilot. The average operational german fighter of the era was 80-100 km/h slower than the p51,spit xiv ,spit ix 25lbs, tempest, p47m , p38l, la7 ,yak3,
Peter Gunn
Master Sergeant
FalkeEins
Senior Airman
..ever read Bob Goebel's memoir 'Mustang Ace' ? All American fighter pilots could probably fly pretty well, this was certainly true for all P-51 pilots. Only relatively few fighter pilots could shoot as well as they could fly. I guess that's what you meant....
It is a statement of nonsense on par with "anyone could win in Max Verstappen, Lewis Hamilton Michael Schumacher's car. In fact joe public cant even pull off and keep the tyres warm on an F1 car. The number of allied pilots that were shot down in 1944 proves it wasnt easy.
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- #35
drgondog
Major
A VERY small % of American pilots that entered combat vs LW after June 1st scored five in the air.
Crimea_River
Marshal
A good answer is that it's because many of your facts are distorted. Your statements "badly outperformed" after 1941, "sitting ducks", "inferior fighters beyond any hope" would have been met with some derision by the thousands of allied casualties after 1941.
Snautzer01
Honourably banned
- 38,170
- Mar 26, 2007
Indeed look up Richard Hammond of top gear in an f1 car. Now these boys of top gear drive a fast car all right. Never seen Hammond so much trying to get round and failed. And being Hammond he did try even over his limits.
After that i looked at f1 racers quite differently.
It was Hammond (and others) I had in mind, he had a few goes at pulling off then they had to stop because the tyres were so cold they were flat, he drives fast cars but is not a racing driver, he is Joe Public. If you look at the losses on both sides in 1944 any claim that anything was easy is an insult to all concerned.
Many yrs. ago i read Heinz Knokes book, where he stated in a passage that his Me109g was becoming very sluggish, he blamed it on all the crap being hung on the airframe and the "bulges" all over the fuselage. The R4M rockets on the wings seemed to draw his ire as a major drag issue. I think some pilots nicknamed the aircraft "the bulge"
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- #40
drgondog
Major
combination of pressure drag items (carb inlet, radiator size incease), G heavier than F, bulges for 15mm MG 131 & low quality camo paint very grainy and draggy & open gap wheel well (parasite drag), weight increase (increased induced drag, engine weight increase from DB 601 through DB 605, etc.
