Bf109E-7 comparison with E-1/V15a Top Speed and discussion

[6./ZG26_Klaus_Mann]

The Bf109E-7 ingame seems to me to be just about too slow when compared to the tested prototype.

 

With all radiators closed and 1.32ata, full nose down trim I do not achieve more than 485kph in autumn.

The tested V15a achieved a corrected to 20° and with guaranteed power output 498kph, or 493 at 5°C Local speed and derated to 950PS as well as 1/4 open water radiator. Vollgas in the Context of the DB601As meant 1.3ata at 2400rpm.

 

These are the differences between the aircraft that are of aerodynamic nature (I'll mark them + and - for decrease or increase in capability)

 

E-1

-Open Propeller Hub (-)

-Engine slightly derated to 950 HP (--)

-No Cover above exhausts, (?) [Covers were added to prevent exhaust fumes from entering the supercharger air-intake]

-No Ejector Exhausts (-)

-The Automatic Supercharger Control may not have been present/engaged, thus the Supercharger may have been underperforming at SL, resulting in Power decrase (-)

-No armor (?), Old-style Canopy [?(+)]

 

E-7

-Covered Propeller Hub (+)

-Normal Rating of 990 or 1020PS at 1.3ata (+)

-Cover above the exhausts (?)

-Ejectors were fitted (+)

-Automatic Supercharger Control (+)

-New Style Canopy (-?)

-Bulges through MG FF (However no changes in speed were detected IRL tests) (-?)

 

More weight through (how does it effect speed?)

Extensive Armor

Additional Piping

 

Why should I not be able to expect the E-7 to achieve test results flown by an equal Prototype?

[indiaciki]

As far as I know BOS /BOM AC are modelled using actual data from captured AC and tested by the soviet air force during the war = actual performance of mass produced AC. Official data is provided by the manufacturer. Just look at the VW data :D

Edited November 9, 2015 by indiaciki

[6./ZG26_Klaus_Mann]

As far as I know BOS /BOM AC are modelled using actual data from captured AC and tested by the soviet air force during the war = actual performance of mass produced AC. Official data is provided by the manufacturer. Just look at the VW data :D

So the best data for the perfromance of the figurative VW is a Second Hand Golf maintained by the russian Equivalent of ATU (ATU is a german chain of Garages for all makes and models and has a reputation. The Reputation is in the creative abbreviations of its name like "Amateure treiben Unfug" (Amateurs practise Horseplay).

Well if that doesn't stand for reliable results, I don't know what does.

[indiaciki]

something like that. I read a thread a long time ago stating that the Soviet fuel had less octane than the german - might be significant. But AC in war with more than 4 sorties a day are very likely more like a used Golf with 200.000 km than a new one.

Edited November 9, 2015 by indiaciki

[Trinkof]

Mmmmhhh... Doubtful : why the the F4 is so grossly over performing then? And the G2 spot on?

 

I guess like people with common sense, they have mixed sources

[JtD]

At high speed at sea level, the DB605A does not develop ~1000hp. If you take a DB601A power chart, you'll often have the effects of ram pressure on full throttle altitude indicated. Try to use these to extend power production to sea level.

[JtD]

Not that anyone really seems to care, but the DB601A develops about 950hp at high speed at sea level, which is pretty much the same the DB601 in the V15 developed. The test wasn't done under standard conditions, and if you correct for that, you'll end up in the 480-485 km/h range If they were using the V-15 as a reference, it would seem they nailed it.

[6./ZG26_Klaus_Mann]

The V-15 was powered by the A-1, which has the 990PS at 0m withouth RAM Air, Exhaust Cover and Ejector Exhausts. The Test was done at 5°C reaching 493 and corrected to 498 (5% more power and Ejector Exhausts.

I don't see ay reason why in autumn the aerodynamically improved E-7 shouldn't perform as well or better,

[JtD]

What are the atmospheric conditions on the autumn map - temperature, pressure, density? If they are close to standard conditions, the plane will go slower. Other tests suggest they are close to standard, so that would be reason 1 for you.

And if the engine in the E-7 is a normal A-1, it will not develop the 1018PS at 1.3ata the V15 figures were corrected to. Ata settings in game suggest it is, so that would be reason 2 for you.

 

How do you know which engine the V15 had during that test? Even Kurfürst on his page who's hosting the original transcripts of the test protocol is just speculating on that matter. If you have a definite source answering that question, you may want to share it with him. I'm sure he'd be happy about it.

[Matt]

Temperature and pressure on the autumn map are 15 °C and 760 mmhg.

 

I ran a test using these conditions and calculated by measuring time needed to fly 30 km with constant speed:

 

1.3 ATA / 2400 RPM

25% open radiator

Fully closed oil cooler

Stabilizer fully nose down

No armored headrest

100 % fuel load

no ammo

 

Result at 300 meters : 480 km/h

I would extrapolate that to 477 km/h at sea-level and considering that i don't have any idea, wether the E-7 was exactly as draggy (the new windscreen was more draggy btw) as a V-15A prototype and since this test of the V-15A shows the highest caluclated speed with 1.35 ATA and that you can find a few German and some other flight tests that show a lower speed at 1.3 ATA and we have the late/new supercharger with higher critical altitude, which could easily cause a slight power loss at lower altitude and that i didn't even compensate for side slip, i would consider that acceptable.

 

There was a very interesting topic on the CloD forums which you can find by googling for "Bf 109 e-1 speed" and Kurfürst is taking part in the discussion and even he doesn't seem to believe that the V-15A test should be used for modelling the E-1, which is a hell lot more comparable to the V-15A than the E-7 we have in BoM.

 

As for indiacikis statement that the devs are using Soviet test of captured aircraft for the speed of the German aircraft, that's nonsense.

Edited November 14, 2015 by Matt

[6./ZG26_Klaus_Mann]

"The 109E was produced with at least two major models of the DB 601A engine (DB 601N model was also used, but is not detailed here):

the A-1, with 1,30 ata manifold pressure for  990 PS output at 0m, and
the  Aa, with 1,35 ata manifold pressure for 1045 PS output at 0m, both for cleared for 5 minute periods.

It should be also noted that the D.(Luft) T.3601, DB 601 A Motoren-Handbuch also notes that slightly higher manifold pressures up to +0,03 ata are normal under some circumstances; it also notes +/- 2,5% tolerence on output. During the trials, the  engine, referred to simply as 'DB 601A', developed 1,31-1,33 ata and 951 PS (Blatt 6).  The 996 PS nominal output indicated by the report points to the use of a DB 601A-1 engine.

    The DB 601A engine was bench-tested before the trials and it was found that it was not developing full power guaranteed by the engine manufacturer, but only 951 PS instead of the 996 PS as indicated on the engine curves (value corrected for test conditions in the report), thus claims that the V15a prototype was operating in excess of the established operational limits of the DB 601A are baseless.

    It appears that variable-speed hydraulic supercharger control was either not present or not engaged in the tests (ie. testing seperately with both supercharger gears) : low-altitude and high-altitude supercharger speeds were engaged at a given boost pressure, therefore the curves do not show the characteristic shape of the DB power curve - this would result in a more smooth,curved transition and improved in performance between the supercharger`s two critical altitudes (ca between 2200 and 4800m) in level flight.

Corrected performance for guaranteed engine output, as well as for the correct manifold pressure regulator settings is shown with staggered line marked Garantieleistung. Performance at the guaranteed nominal output was thus 498 km/h at 0 m, and 572 km/h at 4800 m. See Blatt 6.

    Both DB 601 A-1 and Aa possessed a special 1-minute overload output with 1,40 and 1,45ata, for 1100 and 1175 PS at SL, respectively. Performance using this rating was not tested during this Meßprotokoll. It's is also known that the A-1 received an improved supercharger very early on that increased it's rated altitude to 4,500m - it appears the test was performed (given the date and results) with the old type supercharger.

Results are corrected for Standard Day (Normaltag) conditions, and CINA-altitude."

 

From the http://kurfurst.org/Performance_tests/109E_V15a/Geschw_109V15a.html

 

I know that the Document is real, I have seen it on other Websites I stupidly enough didn't save it.

The changes between the two should result in +-0 speed at least in my opinion.

The test was performed with 1.32 ata.

[Matt]

Good copy and paste job there. Yes, the V-15A had the DB 601 Aa, which should've managed to get a boost of 1.35 ATA. Then it would've reached the 498 km/h. When it was tested with 1.3 ATA (then it had the same power output as the DB 601 A-1, which is the engine our E-7 has), it managed to reach 480 km/h. If you don't believe me, maybe you believe Kurfürst. 

 

http://forum.1cpublishing.eu/showthread.php?t=34816&page=2

 

And if you don't believe him, there's nothing i can do for you.

[6./ZG26_Klaus_Mann]

Good copy and paste job there. Yes, the V-15A had the DB 601 Aa, which should've managed to get a boost of 1.35 ATA. Then it would've reached the 498 km/h. When it was tested with 1.3 ATA (then it had the same power output as the DB 601 A-1, which is the engine our E-7 has), it managed to reach 480 km/h. If you don't believe me, maybe you believe Kurfürst. 

 

http://forum.1cpublishing.eu/showthread.php?t=34816&page=2

 

And if you don't believe him, there's nothing i can do for you.

No,

The engine in flight, if you looked at the  table and description clearly states that in flight it only put out 950 PS, when it should have put out 996 PS according to DB's Powercurve (of coourse corrected to the Level above the SL where the tests were taking place) , while the Aa is specified for 1045PS at 0m.

The V15a defeintely had an A-1.

The Page is about Cliffs of Dover, different Aircraft.

The Test was flown at 1.31 ata and something caused the engine to deliver less power than specified, one plausbile cause for which could be that the Supercharger apparently was mechanically driven, due to lack of the hydraulic clutch device which allows for supercharger slip, delivering less power to the superharger at SL, thus allowing it to produce more.

 

 

 

It appears that variable-speed hydraulic supercharger control was either not present or not engaged in the tests (ie. testing seperately with both supercharger gears) : low-altitude and high-altitude supercharger speeds were engaged at a given boost pressure, therefore the curves do not show the characteristic shape of the DB power curve - this would result in a more smooth,curved transition and improved in performance between the supercharger`s two critical altitudes (ca between 2200 and 4800m) in level flight.

[Matt]

 

 

It should of course match the real life DB 601Aa at 1.35ata (V-15a, Baubeschreibung "5%" specs, Swiss trials of serial no. 2404 - these all have Aa, although it's quite clear the Swiss graph is only showing high speed supercharger, ie. Hohenlader performance - note the almost exact match between V15a Hohenlader and the Swiss single speed graph)

Yeah well, Kurfürst disagrees, but who cares. This is now my last post.

[6./ZG26_Klaus_Mann]

Yeah well, Kurfürst disagrees, but who cares. This is now my last post.

The Fact remains that the Guranteed Power Curve given doesn't fit the Aa at all, and the fact that maybe the Supercharger Drive was faulty fits just as well too, since it would decrease the power oputput having the Supercharger spin too fast at SL, even in low gear.

[Askania]

http://usaaf.superforum.fr/t2-a-vendre-bf109-e1-7

Bf 109 E-7 Werk-Nr 3523, CS+AJ, Rote 6, 5./JG5

motor DB 601 Aa Werk-Nr 11220

[6./ZG26_Klaus_Mann]

 

 

This is for Combat Power, however on Kurzleistung 475 seem plausible.

That's why a DB601Aa as an option would be a great idea too.