[REPORTED] K-4 level speed

[Hummingbird]

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...

 

Which is probably how it was as we have nothing but conservative calculated climb values for the K-4.

 

Keep in mind that the G-2 averaged 21.5 m/s and went as high as 24.7 m/s in Finnish tests at 1.3 ata.

 

The Germans must have simply estimated climb rate in a different radiator condition.

[rel4y]

Im guessing that is compared to a partially retractible tailwheel on F/ early G models, since it talks about G2-4 models. The long Spornrad of later G models induced much more drag arrested (G14/G10) vs fully retracted (K4). The long Spornrad was necessary to employ 500kg bombs with appropriate ground clearence and improve forward visibility. 3-4 km/h improvement doesnt sound right at all to me. :O

 

I would expect such a small low drag airframe with an 1850 HP engine to climb like hell btw so I wouldnt be suprised if climbrates reached up to 25 m/s. Especially if your hypothesis of neglected exhaust thrust is correct! If it is one thing a 109 was build to do, then its climbing fast (as an interceptor is supposed to do).

 

Edit: Happy Christmas by the way and thanks for your correspondence YoYo.

Edited December 25, 2015 by rel4y

[Hummingbird]

Finnish G-2 climbing tests performed at 1.3 ata:

[Kurfürst]

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

 

This is also good, the more detailed figures are from the LZSTG 109G document, which has summary of drag items and the pure drag "cost" of speed (and also: drag is expressed decrease of flat plate are in sq m - here:

 

http://kurfurst.org/Performance_tests/109G_Leistungzusammenstellung/Leistungzusammenstellung109G.html#dragitems_table

 

No. 19 (wheel well covers, this comes from real life drag installation test in G-6 in 1943), 20 and 21 (short and long tail wheel cost when fully out) are of interest, since those are main changed from G-/AS to K airframe (larger streamlined motor cover already the same).

 

The speed difference in these tables are understood for "standard 109G" speeds at SL (which is 510 km/h, they assumed late G-1 with non-retractable tailwheel, very likely based on WkNr 14 026 tests of August 1942), so at higher speeds the change is slightly different. But for this reason the change in equivalent drag plate area is also expressed in m2 so calculation for greater (or lower) speed should be easy.

 

Regarding tailwheel - document you posted compares possible speed gain to 1/2 retracted to fully retracted tailwheel (F and early G standard). Should be different from difference between fully retracted vs short/long extracted tail-wheel (tables I posted)

 

19 Fahrwerk Restabdeckung (main wheel well covers)

-0,0265 m2 Δ[Fcw]

+10 km/h of sea level speed

 

20 Ausgefahrener Sporn (lowered tailwheel)

 

+0,0350 m2 Δ[Fcw]

-12 km/h of sea level speed

 

21 Erhöhter ausgefahrener Sporn (tall tailwheel, lowered)

 

+0,0540 m2 Δ[Fcw]

-17 km/h of sea level speed

 

The LZSGT 109G document gives drag effects for Sea Level; doc you mentioned probably gives range of speed change figures for SL and higher altitudes.

 

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.

 

Yes I figured out that you probably used 1,3ata throttle then set prop via manual to 2600 to get same rpm as in G-5/AS test.

 

In any case, main point - 109K cannot be the same fast as G-5/AS at the same power, you know why, K is is cleaner aircraft by significant margin, and difference in speed expressed in these drag tables accurately - ca. 27 km/h faster than G at same power.

 

This is 109G with ASM and 1800 PS / 1.7 ata. Real life test.

 

 

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...

 

I do get that, but this isn't reason to chop off 30 km/h from the speed of the aircraft... perhaps other aspect of model needs tuning.

 

Climb figures standard were usually understood for radiators being more open (ca 2/3s, 220-250 mm) than in speed.. so I can think of increased drag from radiator needed, or perhaps the missing part is the radiator jet exhaust thrust being lower at greater radiator opening.

 

But I do not wish to take your job. :p

[Yo-Yo]

Finnish G-2 climbing tests performed at 1.3 ata:

 

Referring to the other tests this result must be named as "excess point" regardless of the reason it appeared.

Possibly not full loaded... or the results were not recalculated to MSA conditions.

 

http://forums.eagle.ru/showpost.php?p=2404077&postcount=8

 

See the bunch of 1.3 ata tests.

[Kurfürst]

Finnish MT 215 (G-2 w. non/retractable tailwheel) was fully loaded - climb results match other at 1.3ata above ca 2500m.

 

Finns note radiator was operated automatically but thermostat begun opening in at ca 2000m - better climb rates almost certainly result from radiator flaps being in minimum drag (near closed) position at start of climb.

 

English translation of results available at http://kurfurst.org/Performance_tests/109G_MT215/109G2_MT215_en.html

 

Point of interest from test notes:

 

Notes of pilot:

 

At 2500m coolant radiator flaps open fully for the first time.

After that varying between open and closed position.

[rel4y]

I was about to post that link as well, thanks Kurfürst. That test is in my opinion actually absolutely legitimate.

[Yo-Yo]

2 Kurfurst

Regarding tailwheel - document you posted compares possible speed gain to 1/2 retracted to fully retracted tailwheel (F and early G standard). Should be different from difference between fully retracted vs short/long extracted tail-wheel (tables I posted)

 

19 Fahrwerk Restabdeckung (main wheel well covers)

-0,0265 m2 Δ[Fcw]

+10 km/h of sea level speed

 

20 Ausgefahrener Sporn (lowered tailwheel)

 

+0,0350 m2 Δ[Fcw]

-12 km/h of sea level speed

 

21 Erhöhter ausgefahrener Sporn (tall tailwheel, lowered)

 

+0,0540 m2 Δ[Fcw]

-17 km/h of sea level speed

 

The LZSGT 109G document gives drag effects for Sea Level; doc you mentioned probably gives range of speed change figures for SL and higher altitudes.

 

What is the source of this data? I mean calculations, WT test or they were taken from the level speed flight?

 

One of the Russian official handbook of the same period gives quite close value of drag area for the half-opened wheels but very different value for a fixed tailwheel... and both sources based on somewhat like tests. :)

[Hummingbird]

Referring to the other tests this result must be named as "excess point" regardless of the reason it appeared.

Possibly not full loaded... or the results were not recalculated to MSA conditions.

 

http://forums.eagle.ru/showpost.php?p=2404077&postcount=8

 

See the bunch of 1.3 ata tests.

 

Again the difference was due to a difference in the radiator position in relation to the German performance figures, as well as finding the actual best climb speed.

 

I actually think you got it right with the FM before the last change Yo Yo, at least all the real life tests seem to suggest to. Remember being able to go around 600 km/h at SL before the last change as well.

[Yo-Yo]

Finnish MT 215 (G-2 w. non/retractable tailwheel) was fully loaded - climb results match other at 1.3ata above ca 2500m.

 

Finns note radiator was operated automatically but thermostat begun opening in at ca 2000m - better climb rates almost certainly result from radiator flaps being in minimum drag (near closed) position at start of climb.

 

English translation of results available at http://kurfurst.org/Performance_tests/109G_MT215/109G2_MT215_en.html

 

Point of interest from test notes:

 

Notes of pilot:

 

At 2500m coolant radiator flaps open fully for the first time.

After that varying between open and closed position.

 

The most of tetsts at 1.3 ata give not more than 17 m/s generalised for 3400 conventional GW.

THis Finnish test gives almost 22 m/s average ROC for the first 150 s of climb.

[Yo-Yo]

Again the difference was due to a difference in the radiator position in relation to the German performance figures, as well as finding the actual best climb speed.

 

I actually think you got it right with the FM before the last change Yo Yo, at least all the real life tests seem to suggest to. Remember being able to go around 600 km/h at SL before the last change as well.

 

Noway... the best climbing speed is calculated as 1-2-3 and this procedure does not require highest math to do it. Radiators can give +- 1 m/s at the speed of climb but not more. Keep in mind that you can not deliberately close or open radiators as you do not wish to kill the engine.

But - as you perform your tests at -30C you will have radiators shut and if you perform tests at +25C they will be open, so, even if you recalculate your results to MSA regarding lift, drag and engine power there will be a difference due to radiators left out of count.

I can agree with this test only if it was performed at -25C and was not recalculated at all.

 

THe last FM had higher engine power by mistake - so it was. :) As far as I can see, the current model is very good corresponded with 109G with the DB 605D engine... possible, if some valuable real test data is found, the drag can be reduced regarding the differences between G and K.

Edited December 25, 2015 by Yo-Yo

[Hummingbird]

Well the drag was lower on the K-4, that much is certain, as outlined in the German reports. Actual flight tests with the G-14 provide a good analogue as it weighed the same but featured none of the drag reducing improvements of the K-4, and yet at a lower powersetting it was capable of the same speed as our ingame K-4 (A 300 L tank even being mentioned), so obviously the current drag figure is too high.

 

Another thing, why should we need to use manual prop pitch to attain max speed? It should be automatic. At least I've never read a test which said manual pitch was needed to attain top speed.

Edited December 25, 2015 by Hummingbird

[Yo-Yo]

Another thing, why should we need to use manual prop pitch to attain max speed? It should be automatic. At least I've never read a test which said manual pitch was needed to attain top speed.

 

Sorry, but you misunderstand the main idea I wrote, why I used manual pitch setting. Try to read the post again and think what it was written.

[Hummingbird]

Sorry, but you misunderstand the main idea I wrote, why I used manual pitch setting. Try to read the post again and think what it was written.

 

Well I was also refering to the fact that Rel4y managed 573 km/h with manual prop pitch, but then again that could be due to an ever so slight dip in altitude. So just wanted to make sure that we didn't need to suddenly use manual prop pitch to attain max speed.

 

Anyway seeing as you say that there was a mistake in the power available, I am wondering in what way? As simple as too much bhp?

 

Either way the K-4 should be able to reach at least 595 km/h at sea level as the real aircraft, and since you say engine power is correct then it must be a drag issue.

 

Again the clearest evidence is the tested max speed of the G-14 which reached the same 568 km/h at SL as our clean K-4, yet for a lower powersetting and an aircraft noticably more draggy.

Edited December 25, 2015 by Hummingbird

[Crumpp]

Yo-Yo says:

THe last FM had higher engine power by mistake - so it was. As far as I can see, the current model is very good corresponded with 109G with the DB 605D engine...

 

 

Going from a known point, adding power to achieve performance at an unknown point.

 

That is perfectly valid technique readers.....

 

Yo-Yo says:

possible, if some valuable real test data is found, the drag can be reduced regarding the differences between G and K.

 

Probably not ever going to happen and it is unknown if such data even exist's.

 

A concerted effort at drag reduction was part of the Bf-109K4 program, which complicates things somewhat.

 

 

 

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."

 

The performance estimate appears to be the top of the margins.

 

 

Mtt reported to Rechlin on performance:

 

 

The Kennblatt, which is a flight planning document, also agrees with the 580kph reported to Rechlin.

 

 

568kph - 580 kph = 12kph

 

[12kph/580] * 100 = 2.06% = Gives good agreement with the Kennblatt and published figures for the Bf-109K4.

 

So while the OP claim the DCS Bf-109K4 does not match the specific performance of 580Kph, it does give good agreement with the range of specific performance that can be expected from a Bf-109K4.

 

More importantly, it also gives good agreement with the relative performance of the BF-109K4 vs P-51.

 

The P-51 should have a low velocity turn rate advantage if the Bf-109K4 tries to match the P-51D's best turn speeds:

 

 

It preserves the relative dogfighting performance such that while the individual specific performance is accurate within significant digits, the relative performance is more accurate. That makes for a more balanced and fun fight no matter which aircraft you choose.

 

 

That fun factor is why we play the game. :thumbup:

[Hummingbird]

Crumpp,

 

Keep in mind that far from all K-4's featured wheel well covers, and without those the top speed at 1800 PS would be 580 km/h. However our ingame version does feature the wheel well covers, and with those the SL top speed would be 595 km/h as they represented a 15 km/h gain in speed. Hence the figures sent to Rechlin, which btw are dated 2 months earlier and list engine performance figures 50 PS lower than the final performance estimates that incorperate the wheel well covers :)

 

http://kurfurst.org/Engine/DB60x/DB605_datasheets_DB.html

 

Finally regarding your graphs I don't agree with the lift line at all for a power on situation as that is where the slats should increase in the overall CLmax of the 109 over that of the P-51. Hence how the 109 was able to fly level at 130 km/h at 1.3 ata clean. I usually use a 1.41 freeflow CLmax for the P-51 and 1.48 for the 109, but I estimate an increase to ~1.7 CLmax with power on for the 109 where'as one of ~1.5 for the P-51. But we'll leave that for another discussion.

Edited December 26, 2015 by Hummingbird

[ArkRoyal]

Oh I must say this is all rather entertaining.

 

 

For those of you on the sidelines, or not familiar with the history of complaints for the DCS WW2 Aircraft, you might find what I'm about to say interesting. For those of you who are in the know, teeheehee.

 

 

Alright people, what we have here is a classic case of the shoe being on the other foot. What is truly captivating here is watching the three primary axis fanboys on these forums doing their darnedest to prove the 109K is wrong through documentation. Interesting approach, considering that in every thread where documentation was used to claim axis aircraft were over-performing, they used every trick in the book to obfuscate the issue and claim the documents were wrong in one way or another. Now that Yo-Yo has castrated one of their own planes, they seek to prove him wrong with the historical documentation. :music_whistling:

 

But I gotta hand it to Yo-Yo. I certainly dont agree with this approach, but at least he is being consistent with his usual explanation for a FM problem when it doesn't agree with government data. As per usual, the government data is flawed in some manner. The only evidence of this error being that ED's flight model doesn't agree with the historical data (which of course means its the historical data that is wrong, not the FM. :music_whistling:) There is never any explicit evidence of such documentation errors on the various governments parts: it is merely presumed that the governments in question were at fault in some convenient manner, and ED's math is never wrong.

[Hummingbird]

You really can't stick to the topic can you ArkRoyal?

[ArkRoyal]

You really can't stick to the topic can you ArkRoyal?

 

My good man, but I was on topic. I am merely commenting on the spirit of the discourse in this thread. :D

[Hummingbird]

My good man, but I was on topic. I am merely commenting on the spirit of the discourse in this thread. :D

 

No, you're trying to derail the thread with accusations of bias.

 

How about we stick to the documentation?

[ArkRoyal]

No, you're trying to derail the thread with accusations of bias.

 

How about we stick to the documentation?

 

You've got me all wrong. By all means continue your argument about 109 speed. Me pointing out their is bias on both sides is highly relevant to any legitimate debate. Its always important to know if all the players are on the level. :music_whistling:

 

What you don't see here is that I'm trying to help you out. Albeit, I cannot in good conscience do that by pretending the wrong party here was never without its own foibles.

 

This is the common ED tactic. Whenever concrete evidence is given to refute the present nature of a flight model, ED makes insinuations as to the accuracy of the documentation given. There is never any explicit evidence of this other than the FM not agreeing with the data.

 

So you see, I'm helping us all out by pointing out that this same method is being used against both sides of the aisle. But to be fair, in good conscience, I simply must point out that this particular side of the aisle has sided with the aforementioned tactic when convenient. :megalol:

 

But by all means....continue your arguments to fix the 109.

[Hummingbird]

 

PS: As it should.

[NineLine]

So this thread went from K-4 level speed, to climb rate to pictures of our favorite planes... I love these threads... not.

[Hummingbird]

So this thread went from K-4 level speed, to climb rate to pictures of our favorite planes... I love these threads... not.

 

I'd love it if it could stay on topic SiTh, I just felt obliged to show I am no axis fanboy :)

 

As for the climb rate, it is actually relevant as drag & thrust play into that, and since there were recent changes to these areas it needs to be considered.

[Crumpp]

You've got me all wrong. By all means continue your argument about 109 speed. Me pointing out their is bias on both sides is highly relevant to any legitimate debate. Its always important to know if all the players are on the level. :music_whistling:

 

What you don't see here is that I'm trying to help you out. Albeit, I cannot in good conscience do that by pretending the wrong party here was never without its own foibles.

 

This is the common ED tactic. Whenever concrete evidence is given to refute the present nature of a flight model, ED makes insinuations as to the accuracy of the documentation given. There is never any explicit evidence of this other than the FM not agreeing with the data.

 

So you see, I'm helping us all out by pointing out that this same method is being used against both sides of the aisle. But to be fair, in good conscience, I simply must point out that this particular side of the aisle has sided with the aforementioned tactic when convenient. :megalol:

 

But by all means....continue your arguments to fix the 109.

 

Where is the aisle and who are the sides??

 

Thanks but no need to answer.

 

Your post is simply irrelevant, off topic, and trying very hard to be inflammatory without cause.