[REPORTED] K-4 level speed

[Hummingbird]

Just tested the K-4's max level speed at SL which turned out to be 568 km/h IAS.

 

This is off by 30-40 km/h in comparison to the real thing which did 595-608 km/h at SL at 1.8 ata depending on engine model:

http://kurfurst.org/Performance_tests/109K_PBLeistungen/files/5026-26_DCStart_noMW_geschw.jpg

http://kurfurst.org/Performance_tests/109K_PBLeistungen/files/5026-18_DCSonder_MW_geschw.jpg

 

In other words the ingame Bf-109 K-4 is currently performing like a Bf-109 G-14 running at 1.7 ata w. MW-30 (and if I'm not mistaken a 300 L drop tank too):

http://kurfurst.org/Performance_tests/109G14_May44trials/G14_erflogen_May44_viaGGHopp.jpg

Edited December 23, 2015 by Hummingbird

[Hummingbird]

Could this be the result of the effort to reduce the climb rate from earlier?

[gavagai]

I don't read German, but the DCS 109K-4 airspeed seems like a good match to this graph:

[Hummingbird]

This is the original chart presented below Gavagai, and it reads 595 km/h (370 mph) at SL with the std. prop (same as the thin prop), which is 27 km/h faster than what our ingame K-4 is capable of:

 

PS: Be careful using the performance data on Mike Williams site for anything but Allied aircraft, he's sadly very picky with what he chooses to show for German aircraft and his agenda is very obvious. What he cites on his graph is actually the K-6's performance curve at Sondernotleistung with the thin prototype prop.

Edited December 24, 2015 by Hummingbird

[ArkRoyal]

This is the original chart presented below Gavagai, and it reads 595 km/h (370 mph) at SL with the std. prop (same as the thin prop), which is 27 km/h faster than what our ingame K-4 is capable of:

 

PS: Be careful using the performance data on Mike Williams site for anything but Allied aircraft, he's sadly very picky with what he chooses to show for German aircraft and his agenda is very obvious. What he cites on his graph is actually the K-6's performance curve at Sondernotleistung with the thin prototype prop.

 

 

Your point on this issue is largely moot.

 

If in fact you actually conducted your level speed run correctly, we still don't really have a problem here. At least not relatively speaking.

 

Your tested speed of 354mph about 5mph slower than the in game P-51s stop SL speed about about 360mph. This isnt bad considering that a P-51D (w/wing racks) could do 375mph to your K4's 370mph:music_whistling: You should rejoice that at least one aspect of the reletive 109/51 flight model is correct :megalol:

 

 

By they way, I'm sure you just forgot to mention it :megalol:, but those same German graphs show that the current in game bf109 is massively over climbing! As of the latest patch the 109 at max internal fuel is still climbing at about 5000 feet per minute! Also known as 600 feet per minute faster than it should be! I am sure you were just about to either start a new climb thread or post your consternation at this error is one of the existing ones!

[otto]

Your point on this issue is largely moot.

 

If in fact you actually conducted your level speed run correctly, we still don't really have a problem here. At least not relatively speaking.

 

Your tested speed of 354mph about 5mph slower than the in game P-51s stop SL speed about about 360mph. This isnt bad considering that a P-51D (w/wing racks) could do 375mph to your K4's 370mph:music_whistling: You should rejoice that at least one aspect of the reletive 109/51 flight model is correct :megalol:

 

 

By they way, I'm sure you just forgot to mention it :megalol:, but those same German graphs show that the current in game bf109 is massively over climbing! As of the latest patch the 109 at max internal fuel is still climbing at about 5000 feet per minute! Also known as 600 feet per minute faster than it should be! I am sure you were just about to either start a new climb thread or post your consternation at this error is one of the existing ones!

 

I think your point is absolutely true concerning relative speed and climb but too many emoticons on same page.

I've read a bunch of german publications and a climb rate value of 22m/s is mentioned . In game currently is 25 m/s or so.

Also the 109's turn rate in game that does't really match up what i read.

[MiloMorai]

Is prop 9-12199 the standard prop fitted to the K-4?

[Hummingbird]

Is prop 9-12199 the standard prop fitted to the K-4?

 

No, that is the thin prototype prop. The graph lists the performance of the std. 12159 prop as well. The advantage of the thin prop was increased performance at high altitude (at SL it was identical to the std. prop as noted in the report), but for a slight sacrifice in climb rate.

 

All of it is detailed in the report.

Edited December 25, 2015 by Hummingbird

[Hummingbird]

I think your point is absolutely true concerning relative speed and climb but too many emoticons on same page.

I've read a bunch of german publications and a climb rate value of 22m/s is mentioned . In game currently is 25 m/s or so.

Also the 109's turn rate in game that does't really match up what i read.

 

No the turn rate should be higher, but that's probably a power on CLmax issue as I don't believe the advantage of the slats in power on conditions is modelled. The Finnish were after all able to fly the 109G level at a mere 130 km/h clean at 1.3 ata, showcasing how the slats in a power on situation allowed for the outboard wing section to keep up with the inboard section energized by the prop wash, thereby significantly raising the overall CLmax of the wing as apposed to had it not featured any slats.

 

As for the climb rate, I haven't tested it at all so I can't speak of it. However the issue was said to be solved in another thread as far as I can remember?

Edited December 25, 2015 by Hummingbird

[Hummingbird]

Your point on this issue is largely moot.

 

If in fact you actually conducted your level speed run correctly, we still don't really have a problem here. At least not relatively speaking.

 

Your tested speed of 354mph about 5mph slower than the in game P-51s stop SL speed about about 360mph. This isnt bad considering that a P-51D (w/wing racks) could do 375mph to your K4's 370mph:music_whistling: You should rejoice that at least one aspect of the reletive 109/51 flight model is correct :megalol:

 

Not sure what you're getting at? This thread is not about the P-51 you know. Please stay on topic.

 

 

By they way, I'm sure you just forgot to mention it :megalol:, but those same German graphs show that the current in game bf109 is massively over climbing! As of the latest patch the 109 at max internal fuel is still climbing at about 5000 feet per minute! Also known as 600 feet per minute faster than it should be! I am sure you were just about to either start a new climb thread or post your consternation at this error is one of the existing ones!

 

I haven't tested the 109's climb rate, and I haven't seen any figures from anyone who did?

 

The real 109 K-4's climb rate at 1.8 ata was 22.5 m/s, at 1.98 ata it was 25 m/s.

Edited December 25, 2015 by Hummingbird

[Kurfürst]

Couple of points:

 

1. The Graph on Mike Williams site has transcription errors, it shows the data for the K-6 intstead of the K-4

2. The original German 109K speed graph show both the thin bladed 12199 propellor and the standard (serial production) wide chord 12159. The latter is shown by the thin continuous line

3. The German 109K charts are calculated references, essentially prepeared to show the improvements with the new 199 propellor compared to the the existing 159 prop. YoYo made calculations and said that the he concluded that that exhaust thrust was probably not factored in the calculated climb rates on the German charts, hence in real life conditions the climb rate is very likely to exceed the calculated figures.

4. German level speed charts assumed the radiator flaps 3/4 closed, or about 50 mm wide radiator exit width. Be sure to use that in tests as it greatly effects speed (up to 50 km/h difference)

5, The K-4 in DCS is modelled as the 1,8ata DB 605DB version with 1850 PS at SL, as this was probably the most common version in 1944, and which, according to the German charts (5026/27) should do 595 km/h at SL and 715 (710 km/h after Mach corrections) at 7500 m.

[rel4y]

Ok, I tested as well. Were the tests conducted by the germans with 100% fuel quantity? I started with 100% fuel and took the screenshots probably 40-50s into the run, after settings the radiators and leveling out. Prop pitch was on auto and altitude was 7500 m +-8 m at FTH, 8 m +-2 m at SL. Weather effects were set to zero.

 

Max speed at SL was 569 km/h IAS.

 

 

Max speed at FTH was 468 km/h IAS.

 

 

I have no time to convert it to EAS, feel free to tell us though. :)

Edited December 25, 2015 by rel4y

[Hummingbird]

Couple of points:

 

1. The Graph on Mike Williams site has transcription errors, it shows the data for the K-6 intstead of the K-4

2. The original German 109K speed graph show both the thin bladed 12199 propellor and the standard (serial production) wide chord 12159. The latter is shown by the thin continuous line

3. The German 109K charts are calculated references, essentially prepeared to show the improvements with the new 199 propellor compared to the the existing 159 prop. YoYo made calculations and said that the he concluded that that exhaust thrust was probably not factored in the calculated climb rates on the German charts, hence in real life conditions the climb rate is very likely to exceed the calculated figures.

4. German level speed charts assumed the radiator flaps 3/4 closed, or about 50 mm wide radiator exit width. Be sure to use that in tests as it greatly effects speed (up to 50 km/h difference)

5, The K-4 in DCS is modelled as the 1,8ata DB 605DB version with 1850 PS at SL, as this was probably the most common version in 1944, and which, according to the German charts (5026/27) should do 595 km/h at SL and 715 (710 km/h after Mach corrections) at 7500 m.

 

I guess this makes sense considering how the captured 109G tested by the RAF managed to showcase a climb rate mostly superior to anything it was tested against at low altitude without any use of MW50.

 

Also it was normal for calculations to be conservative in regards to real life performance, and that goes for calculations made on both sides.

[Hummingbird]

Ok, I tested as well. Were the tests conducted by the germans with 100% fuel quantity? I started with 100% fuel and took the screenshots probably 40-50s into the run, after settings the radiators and leveling out. Prop pitch was on auto and altitude was 7500 m +-8 m at FTH, 8 m +-2 m at SL. Weather effects were set to zero.

 

Max speed at SL was 569 km/h IAS.

 

 

Max speed at FTH was 468 km/h IAS.

 

 

I have no time to convert it to EAS, feel free to tell us though. :)

 

Yes the figures were for full fuel.

 

What gets me is that in actual test flights the more draggy G-14 was capable of the same 568 km/h speed at SL at 1.7 ata using MW30 and seemingly with a 300 L drop tank attached.

[iFoxRomeo]

Hummingbird, try the following(I'm not at home, so I can't do it)

At level flight at full throttle with 1.8ata, select manual prop pitch and increase the angle of (prop)pitch till rpm drops to 2600.

In an earlier softwareverson of the K4 I could obtain higher speeds that way, but have not tried it with the current OpenBeta and OpenAlpha

 

Fox

[Hummingbird]

Hummingbird, try the following(I'm not at home, so I can't do it)

At level flight at full throttle with 1.8ata, select manual prop pitch and increase the angle of (prop)pitch till rpm drops to 2600.

In an earlier softwareverson of the K4 I could obtain higher speeds that way, but have not tried it with the current OpenBeta and OpenAlpha

 

Fox

 

That shouldn't be necessary though as all the German speed runs were with auto pitch, which should automatically set the absolute optimum prop pitch.

[rel4y]

With prop pitch settings corresponding to 2600 RPM I get max 573 km/h at SL, 1.8 ATA MW50, radiator 3/4 closed, 100% fuel. Still not close to the charts.

Edited December 25, 2015 by rel4y

[Yo-Yo]

The charts you are praying at ARE NOT FROM REAL TESTS. These are simplified engineering estimations based on idealised power curves, efficiency, etc...

 

Here is real tests of G model with 605 AS having 1270 ps at SL.

 

http://www.wwiiaircraftperformance.org/me109/me109g-26108.html

 

 

The corrected for the std temperature result is 507 kph at SL.

In-game 109 having the same power at 2600 rpm (thanks to manual prop!) goes 509 kph.

 

Then, let's recall that max speed = k * Power^0.3333.

So, the optimistic result for the plane flying 507 kph at 1270 ps will be only 575 kph presuming the same CD for the plane (that is correct for SL because M number is not high enough to get noticable increasing of CD) and for the same prop efficiency (that is not correct because of increased rpm and speed that leads to higher Mach numbers at the blade tip, so - to lower efficiency).

In-game 109 flies 568 kph at SL and it is corresponds with the optimistic limit with 1-1.5% acuracy.

 

The case is closed.

Edited December 25, 2015 by Yo-Yo

[Hummingbird]

The G-14 chart is based on actual flight testing Yo Yo, and it shows 568 km/h at SL @ 1.7 ata for a much draggier airplane than the K-4. Furthermore the G-2 achieved 525+ km/h at SL in actual testing at 1.3 ata as well, 527 km/h in Russian testing infact.

 

Now consider that compared to the G-14 the K-4 is considerably cleaner too thanks to:

 

1. Wheel well covers

2. Retractable tail wheel (responsible for 12+ km/h alone)

3. Smoothened MG-131 bulges

 

So I would definitely no consider this case closed at all and I am chocked that you would say that.

 

 

Finally as mentioned in the last part of the report on the K-4's performance:

"The stated performance figures are going to be reached with

well-built serial production machines for certain. No specials were

included in the calculations; improvements as in the case of

Leistungsmaschine I., such as improved surface finish through

special threatment to the airframe and surface protective layer on

the wing and on the propeller, improved radiator passthrough,

symmetrical ailerons, by which an additional ca. 12km/h gain in

level flight can be expected. This 12 km/h will be only added to

the calculations, if the abovementioned measures can be actually

materialized for series production."

 

 

In short the stated performance figures are conservative calculations as to what can 100% be expected. In pretty much every case actual flight testing showcased superior performance.

Edited December 25, 2015 by Hummingbird

[Hummingbird]

Bf-109 G-14 U4 with DB605AM performance with gondola cannons at 1.8 ata (1800 ps, 3504 kg):

http://kurfurst.org/Performance_tests/109G14_PBLeistungen/Leistungen_g14u4_am-asm.html

 

= 557 km/h at SL.

 

Bf-109 G-14 with DB605AM test flown performance at 1.7 ata:

http://kurfurst.org/Performance_tests/109G14_May44trials/109G14_GLCE-may44_trials.html

 

= 568 km/h at SL

 

For the K-4 you need to add at least ~12 km/h due to retractable tail wheel and another ~15 km/h due to wheel well covers (this is probably way too low).

Edited December 25, 2015 by Hummingbird

[rel4y]

In YoYos link the 109 does have "faired bumps" for mg 131. It says fixed tailwheel and uses apparently GM1 system which was not used during testing. It did not incorporate MW50 as it says combat power only was used and GM1 was mentioned. Edit: Graph says 1.3 ATA.

 

I think Hummingbird has a valid point here. The G14 chart says "erflogene Werte" which means it is a real flight test.

Edited December 25, 2015 by rel4y

[Kurfürst]

The charts you are praying at ARE NOT FROM REAL TESTS. These are simplified engineering estimations based on idealised power curves, efficiency, etc...

 

Here is real tests of G model with 605 AS having 1270 ps at SL.

 

http://www.wwiiaircraftperformance.org/me109/me109g-26108.html

 

 

The corrected for the std temperature result is 507 kph at SL.

In-game 109 having the same power at 2600 rpm (thanks to manual prop!) goes 509 kph.

 

Then, let's recall that max speed = k * Power^0.3333.

So, the optimistic result for the plane flying 507 kph at 1270 ps will be only 575 kph presuming the same CD for the plane (that is correct for SL because M number is not high enough to get noticable increasing of CD) and for the same prop efficiency (that is not correct because of increased rpm and speed that leads to higher Mach numbers at the blade tip, so - to lower efficiency).

In-game 109 flies 568 kph at SL and it is corresponds with the optimistic limit with 1-1.5% acuracy.

 

The case is closed.

 

568 km/h for 1,8 ATA K-4 is simply wrong by ca. 30 km/h.

 

If you assume that the power and drag of G-5/AS and K-4 were the same then its clear where the error in the model lies - the drag of the K-4 was significantly lower due to improvements: (a) main wheel well covers: +10 km/h, (b) reatractable, covered tailwheel: +17 km/h.

See Leistungzusammenstelkung 109G of January 1944.

 

In short, K-4 had less drag than G-5/AS tested.

If you add this missing +10+17 = 27 km/h of drag you get exactly 595 km/h. :)

 

Furthermore 109K 30-min rating speed were also greater because power was significantly greater of 605DB (1,45ata/2600 rpm - 1430 PS) then on 605AS (1,3 ata/2600 - 1240 PS).

[Hummingbird]

In YoYos link the 109 does have "faired bumps" for mg 131. It says fixed tailwheel and uses apparently GM1 system which was not used during testing. It did not incorporate MW50 as it says combat power only was used and GM1 was mentioned.

 

A different prop is used as well.

[Hummingbird]

568 km/h for 1,8 ATA K-4 is simply wrong by ca. 30 km/h.

 

If you assume that the power and drag of G-5/AS and K-4 were the same then its clear where the error in the model lies - the drag of the K-4 was significantly lower due to improvements: (a) main wheel well covers: +10 km/h, (b) reatractable, covered tailwheel: +17 km/h.

See Leistungzusammenstelkung 109G of January 1944.

 

In short, K-4 had less drag than G-5/AS tested.

If you add this missing +10+17 = 27 km/h of drag you get exactly 595 km/h. :)

 

Furthermore 109K 30-min rating speed were also greater because power was significantly greater of 605DB (1,45ata/2600 rpm - 1430 PS) then on 605AS (1,3 ata/2600 - 1240 PS).

 

 

I'm sure that the wheel well covers added more than 10 km/h, more like 20 km/h infact. Open orifices on a wing surface are VERY draggy.

 

Also keep in mind that the K-4 features larger wing bulges, thus if you add in a ~5 km/h speed loss due to these and a ~15 km/h speed gain due to the wheel well covers then you get the same ~595 km/h top speed.

[Yo-Yo]

568 km/h for 1,8 ATA K-4 is simply wrong by ca. 30 km/h.

 

If you assume that the power and drag of G-5/AS and K-4 were the same then its clear where the error in the model lies - the drag of the K-4 was significantly lower due to improvements: (a) main wheel well covers: +10 km/h, (b) reatractable, covered tailwheel: +17 km/h.

See Leistungzusammenstelkung 109G of January 1944.

 

In short, K-4 had less drag than G-5/AS tested.

If you add this missing +10+17 = 27 km/h of drag you get exactly 595 km/h. :)

 

Furthermore 109K 30-min rating speed were also greater because power was significantly greater of 605DB (1,45ata/2600 rpm - 1430 PS) then on 605AS (1,3 ata/2600 - 1240 PS).

 

Possibilities for increasing performance

Airframe-wise

 

Wheel well covers, ca 11-14 km/h

Improved MG 131-installation, 7-9 km/h

Fully retractaible tailwheel, 3-4 km/h

 

 

 

THis recommendation is taken from

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

 

 

 

 

And, futhermore, the power ratings you mentioned plays no role - the test was conducted having the same power as for DB 605 AS that was obtained in manual mode.

 

By the way, decreasing the drag you increase CL/CD max that defines climb ratio... so, returnung to the extrapoltaion of it based on real tests we will get higher rates of climb...

Edited December 25, 2015 by Yo-Yo