Yak-1/7/9 vs Bf109G2

[Knegel]

i never see data that show that La-5FN was almost as fast atthe 109K, or i need thet you explain how many it's almost

Hi,

for example on this page:
Lavochkin fighters

On this page its listed with 573km/h:
http://www.desertstar.co.uk/warbirds/http___www.btinternet.com_~fulltilt_PerformLa5La7.pdf

There is a other comparison graphic floating around here in this forum(maybe even post), where the La5 FN get shown with 575-580km/h sea level.

All this is pretty close to the 109K4 performence with 1850PS, the La7 show the same or even bettwe performence like the like the K4 with 2000PS (sea level).

I have no idea what is the real source for the La datas, actually i never saw a real complete test for any russian plane, just datas, without source and without circunstances how the the datas was produced.

And i would realy like to see such datas, or at least the source where the known datas came from.

Greetings,

Knegel

 

[Knegel]

Now I believe you are just trolling, instead of wanting any discussion.

You are trolling!!

Since what time its trolling to ask for sources??

Drag datas regarding the 109 are not much worth without to know the model they came from.

Regarding the aerodynamic there was a huge different between 109E, 109F/G(MG17), 109G(MG131), 109G6AS/G10 and 109K4.

 

[Vincenzo]

Hi,

for example on this page:
Lavochkin fighters

On this page its listed with 573km/h:
http://www.desertstar.co.uk/warbirds/http___www.btinternet.com_~fulltilt_PerformLa5La7.pdf

There is a other comparison graphic floating around here in this forum(maybe even post), where the La5 FN get shown with 575-580km/h sea level.

All this is pretty close to the 109K4 performence with 1850PS, the La7 show the same or even bettwe performence like the like the K4 with 2000PS (sea level).

I have no idea what is the real source for the La datas, actually i never saw a real complete test for any russian plane, just datas, without source and without circunstances how the the datas was produced.

And i would realy like to see such datas, or at least the source where the known datas came from.

Greetings,

Knegel

ok at sea level the max speed of La-5FN it's near of that 109K-4, if the K-4 have not MW. but at 3 km there are around 40 km/h of advantage for K-4.

 

[Knegel]

ok at sea level the max speed of La-5FN it's near of that 109K-4, if the K-4 have not MW. but at 3 km there are around 40 km/h of advantage for K-4.

Sure the K4 has MW50 used to reach 585km/h sea level, its its the DC engine without. The DC engine with MW50 had 2000PS at sea level.

At 3km the K4 with MW50 had still around 1800PS(at highspeed), while the La5FN already was good below its power peak and had only around 1650PS. 40km/h more with 150PSmore, thats not a suprise. Oh, actually its only 30km/h and thats a suprise , cause just 30km/h with 150PS more power??

The La7 is listed with the same speed like the K4 at 3000m(650km/h), still with 150PS less(if it use the same engine like the La5FN).

I only can repeat myself: I would like to see the original tests, where the datas of the russian planes came from.

All other stuff is guesswork.

Greetings,

Knegel

 

[Vincenzo]

for M-82FN afaik 3 km around 1350 hp, at that altitude La-5FN speed it's ~610 km/h, La-7 can go 630 km/h or also 670 km/h (early o late variants) the speed of K-4 can go from 650km/h to 680 km/h depend of powerplant configuration.

 

[Knegel]

1350ps was the Ash-82F at the 2nd supercharger stage, so at 5400m(static power, without RAM effect)
The Ash-82FN had 1630PS at 1650m static power, due to the Ram effect at highspeed the rated altitude got shifted upward to around 3000m.
The La5FN speed curve, shown in a russian fighter comparison sheet, display roundabout 620km/h at 3000m, a similar sheet show 650km/h for the la7 at this altiude.
The only known 109K4 DB605DB + MW50 speed curve also show 650km/h at 3000m.
The 109K4 with DB605DC without MW50 was roundabout 5km/h slower, but thats just fluctuation, cause both engines should have the same power output(1850PS sea level, 1900PS at 800m, 1600PS at 6000m, all static power).

 

[Vincenzo]

1350ps was the Ash-82F at the 2nd supercharger stage, so at 5400m(static power, without RAM effect)
The Ash-82FN had 1630PS at 1650m static power, due to the Ram effect at highspeed the rated altitude got shifted upward to around 3000m.
The La5FN speed curve, shown in a russian fighter comparison sheet, display roundabout 620km/h at 3000m, a similar sheet show 650km/h for the la7 at this altiude.
The only known 109K4 DB605DB + MW50 speed curve also show 650km/h at 3000m.
The 109K4 with DB605DC without MW50 was roundabout 5km/h slower, but thats just fluctuation, cause both engines should have the same power output(1850PS sea level, 1900PS at 800m, 1600PS at 6000m, all static power).

my power was yes static but are right 3km, static, it's the badest of low altitude for M-82 engines, it's the lowest value before to start the 2nd supercharge. i'm no expert but for me it's hard think that 1650 metes statico became 3000 with ram effect.
La-5FN go around 610 km/h to 3, 620 km/h at around 5.5 km. La-7 at 650 km/h it's a intermediate variant neither early or late.
109 k curves Kurfrst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM
with 605D with MW 680 km/h at 3km
with 605DC/ASC w/o MW 650 km/h at 3 km
with 605DB/ASB with MW 660 km/h at 3 km

 

[Knegel]

This test curves are all made with the "Dünnbrettschraube "(new propeller), the seriel propeller made 10km/h less.
The DB605D test never felt to my Eye´s, although i was on Kurfürsts page many times.

Interesting to see is that the DB engine had a 1000m higher rated altitude with MW50, so somehow the presure must have been smaler, this would explain the discrepancy.

Still the La5FN and La7 different need a claricication, 35-40km/h cant come from some simple cleanups.

Somewhere i did read that there was a Ash82FN and FNU engines, maybe thats the cause?

 

[Vincenzo]

This test curves are all made with the "Dünnbrettschraube "(new propeller), the seriel propeller made 10km/h less.
The DB605D test never felt to my Eye´s, although i was on Kurfürsts page many times.

Interesting to see is that the DB engine had a 1000m higher rated altitude with MW50, so somehow the presure must have been smaler, this would explain the discrepancy.

Still the La5FN and La7 different need a claricication, 35-40km/h cant come from some simple cleanups.

Somewhere i did read that there was a Ash82FN and FNU engines, maybe thats the cause?

La-5FN and La-7 are not same plane

 

[VG-33]

Hello

What 109 got tested in the wind tunnel?

The E for sure, probably the F, might be the G. But what does-it change for the 109's high Cd square-shaped canopy?

The 109 had one of the smalest front surfaces of all WWII planes, Cd is just a factor that need to get multiplicated with this area.

And one of the highest Cd = 0.036 for in-line engeened planes. From Hoerner studies.

That most canophys could have been better in a aerodynamical way is well known, but plating glas is mainly flat, as such must canophys with plating glas had a not that good Cd, but still its just the area of the very tiny canopy.

For most canopys I don't know, at least Yakovlev and Bell teams made their jobs, Masserschmitt' s one didn't.
A 0.0007 increase in Cd value, even reported to the fuselage only, not the full airframe (don't have the time to browse my docs now) is not a negligible effect.

Of course, it's just one reason between one hundred (ore one thousand of reasons) that made the Yak faster.

btw, i still dont saw any WWII tests of the Yak´s, so where does the datas comes from??

Mainly from the NII-VVS, LII-NKAP, sometimes from experimental operative units, TsAGI reaserch center had it's flying team too.

They stand in the same discrepancy to other 109 tests like some Yak datas also wont fit to each other

.
You should keep your ideas in order. I previously wrote
The mid-statistical value for 1943 being 531 (with +12, -9 km/h sigma gap)
So (+12, -9 km/h ) is the discrepancy: the fastest serial Yak-7B flew at 544, the slowest ones at 523 km/h at SL
531 is the mean value for Yak- 7B planes assembled in the second-half of 1943.

The mean value was 495-500 km/h for the 1942 planes and about 515 for the early 1943 ones.
This is called improvement, from TsAGI devices. As I wrote, previously
Only by sealing hermetic joints between the engine plates and thiknissing radiator fairing lips, TSAGI gained some 19 km/h for once
BTW, did Messershmitt company tried to reduce drag from radiator fairing leading edge redesign, or were it just a stupid plate wall? Were there attempts to use so called "Meredith" effect?

Would be interesting if this datas are calculated or tested and if they are corrected to standard athmosphair etc.

Usually in the world of aeronautics, yes!

Same strange actually is the discrepancy between some La7 and La5FN datas, where the same engine and very similar airframe show a different of 40km/h over the full height.
40km/h, thats like a 109G-2 with and without 250kg bombs.

And you know what, all the La-5F, La-5FN, La-7 used in 1944 the same Shvetsov M-82FN engine…
With mean 613, 634, 662 km/h respectively at rated hight for serial planes.

Of course the were some discrepancy and speed loose, from serial to experimental and "standard" (reference) planes:
620, 648, 680 km/h due to poor manufacturing quality.

But, the mean speed increase between the tree models is for well-known reasons, since they were obtained by several modifications on the same airframe. 50km/h (24 km/h for hermetic sealing, 15 for other reasons) on the SN° 37212282, and on the "Dubbler". Some sources quoted the heat/pressure (Meredith) optimised effect on the FN model. The SN 37212282 being the transition from La-5F to FN airframe.
35 km/h at least were gained on the SN° 39210206, transitional from the La-5FN to the La-7.

But it's outside the tread subject

he La-5FN airframe must have been absolut rubbish, still this radial powered plane was almost as fast as the 109K with same power and faster than the 2000 PS FW190A (according to the datas) .

Difficult to say, without aerodynamical knowledge, what should be rubbish and what not. It takes an experienced graduated engeneer.

Still, also for this La5/7 datas i never saw a test.

Here for instance, a complaint report with an unsatisfactory La-7, from the NII-VVS

??????????


"See" your later after your "banned" period,

Regards

 

[Kurfürst]

And one of the highest Cd = 0.036 for in-line engeened planes. From Hoerner studies.

Regards

Hoerner's figures are estimates, based on some very rough estimates of speed, thrust and propeller effiency. They are in disagreement with the actual Messerschmitt papers and polars I have, which state a Cd = 0.023 for the 109F/G - that's pretty avarage BTW.

But basically Cd is a meaningless figure, its not even a measure of aerodynamic cleaness. Its always related to wing area, not the entire wetted or frontal area. Basically aircraft with smaller wing area will get higher Cds because of this, since the wing only creates a portion of the drag (say 30-50%), but you compare 100% of the drag to that figure.

 

[VG-33]

Hello

But basically Cd is a meaningless figure, its not even a measure of aerodynamic cleaness. Its always related to wing area, not the entire wetted or frontal area. Basically aircraft with smaller wing area will get higher Cds because of this, since the wing only creates a portion of the drag (say 30-50%), but you compare 100% of the drag to that figure

.

Basically the drag coefficient is always reported to the frontal aera for hydro- aerdynamical science except the aeronautical branch for old peremptary habit reasons. Fortunately there is no low forbidden you to use Cdw, Cdf related to the entire wetted or frontal area, and compare it then to a thin plate. It's why it's often done. If you got values for both 109 an Yak planes, you're welcome.

Sure, the Cd wing 's not the panacea, but it's far from being meaningless too, as well as you don't compare apples and oranges, Gee-Bees and Friedrichshafen G-III planes.

Hoerner's figures are estimates, based on some very rough estimates of speed, thrust and propeller effiency. They are in disagreement with the actual Messerschmitt papers and polars I have, which state a Cd = 0.023 for the 109F/G - that's pretty avarage BTW.

Hoerner is fully right from it's start hypothesis. And i'm not against to have a look at Messerschmitt Polars.

But from Knegel's figures:

Sea Level:
Bf109G-1 525km/h 1310PS
Yak-1/9 530km/h 1210PS

It takes a 73% propeller output (0.73) to obtain a 0,023 Cd (0,0316 Cd x (êtha)) for the Me-109. But VDM wouldn't agree with that.


From the RDK 43 TsAGI manual, the output was 0.785 "practical" for the mounted VISh. I take 0.78.
It makes a 0.0207 Cd for (0.0266 Cd x (êtha)) for Yak.

Not very impressive, since Yak 1-9 Cd ranges from 0.0255 to 0.0195. It's pretty close to the Me-109 values.
Personnaly; i don't see any reason for Knegel to loose sleep for that...

The I-301 (LaGG-1 exp) Cd being more impressive = 0.185 with 0.78 prop output, but 200 -250 kg heavier (more induced drag) and some wing slots extra drag. But it's nothing compared to the Spitfire and the Mustang.

Regards

 

[drgondog]

Hoerner's figures are estimates, based on some very rough estimates of speed, thrust and propeller effiency. They are in disagreement with the actual Messerschmitt papers and polars I have, which state a Cd = 0.023 for the 109F/G - that's pretty avarage BTW.

But basically Cd is a meaningless figure, its not even a measure of aerodynamic cleaness. Its always related to wing area, not the entire wetted or frontal area. Basically aircraft with smaller wing area will get higher Cds because of this, since the wing only creates a portion of the drag (say 30-50%), but you compare 100% of the drag to that figure.

The reason these drag discussion get out of hand is that people on these forums don't get simple agreement regarding what they mean relative to various components of drag.

When calculation Parasite Drag in toto there are MANY components, when summed up, relate to all the individual contributors. Many simply look at a zero lift drag contribution of the wing and loudly pronounce "there is your Cd0 - now lets find CL and we are ready to talk aero"

Not so - and the other frequent dialogue is to calculate the Cd at max speed, and then use that value as a constant everafter when discussing for example 'turning characteristics'.

DRAG is Non Linear. If one has a drag bucket plot of Parasite Drag and Induced Drag as a function of velocity it is all there for you FOR LEVEL FLIGHT throughout the flight regime - but the high point Parasite Drag at the high end is a summation of Cdo x wing area, Cdf for entire wetted area of the airframe, Cd contribution for an open wheel well, a turret, multiple engine nacelles, antennae, gaps in elevators and ailerons and flaps, trim drag for control surface deflections, etc - ALL go into the Parasite Drag summation, along the entire flight profile and only a few relate specifically to the plan view area of the wing... whereas Induced Drag is entirely related to the Wing plan area..

Once the discussion departs from non accelerated, variable speed, variable altitude and variable bank angles - do Not pull out some mysterious "Cd0" and proudly proclaim that you have the answer to the Holy Grail..You don't.

That would be BS...and entirely in the world of Asymmetrical flight conditions over the wing/body where spanwise flow, different loads and drag on "up vs down' wing, trim drag, etc, etc, etc, etc - which are NOT factored into the standard Drag Polar.

 

[Timppa]

Hoerner's figures are estimates, based on some very rough estimates of speed, thrust and propeller effiency. They are in disagreement with the actual Messerschmitt papers and polars I have, which state a Cd = 0.023 for the 109F/G - that's pretty avarage BTW.

Hi,
can you post the document.

 

[Kurfürst]

Great post, DGD!

@Timppa,

 

[VG-33]

Thanks

And are theese sheets related to the F or the G?

The C(alpha) was it for Landung? Was it the freeflow or propeller blowed value?

 

[Timppa]

Thanks, Kurfürst.
I am quite puzzled, as where the difference comes from. Hoerner's subject was apparently G-6, the most draggy submodel, but still

 

[Kurfürst]

The first one is an F datasheet, the second one is G polar. As for its contents, you already know as much as I do, and I think people better trained in engineering then I am to properly explain the deeper meaning of these docs.

 

[VG-33]

Thanks, Kurfürst.
I am quite puzzled, as where the difference comes from. Hoerner's subject was apparently G-6, the most draggy submodel, but still

Hello Timppa

The Hoerner 1944's 109 G was flying at 380 mph at 22 000 ft, 1200 hp.The chosen prop output was 0.85.

I have made my calculations at SL, 525 km/h, output = (0.73).

The Cx =P. (etha) / (rhô) . V^3 . S

Cx being Cd in french. So it's inversly proportionnal to the density and the cubic speed order. So the 660 km/h flying G1, would have a Cd reduced from (660/610)^3 value.
( 1.08 ) ^3 = 1.26
So G-1 Cd (0.36/1.26) = 0.285

Not 0.23 but the plane is flying at a higher both fuselage and wing AoA, due to the density and some power loss at altitude.

Horner's report is somewhere on the WWII Aircraft Performance site

As DrGondog said in his repy, the Cd has no vocation to stay constant.

Regards