Question about Bf 109K-4

[robert_schulte]

Originally Posted by Kurfürst

That`s debatable. I`ll leave the 152H out, it was a specialized figther and unbeatable in high altitutdes, but otherwise nothing special at normal altitudes.

I wouldn't say, that the 152 H was nothing special at normal altitudes. According to Willi Reschkes book Jagdgeschwader 301/302 a Fw 190 A-8 was easily turned out in a simulated dogfight against a Ta 152 H-0, at altitudes from near ground to 3000 meters. The Fw 190 was flown by an experienced pilot whereas the pilot of the Ta 152 had only 2 take-offs with it then.
Can't have been too bad

[Kurfürst]

no no no, it was not at all of course! What I say it was not so special in normal altitudes than high up. it was as good as the best latest fighters, though I may add outturning the rather heavy A-8 was not too great feat either.

[George Hopp]

According to Willi Reschkes book Jagdgeschwader 301/302 a Fw 190 A-8 was easily turned out in a simulated dogfight against a Ta 152 H-0, at altitudes from near ground to 3000 meters. The Fw 190 was flown by an experienced pilot whereas the pilot of the Ta 152 had only 2 take-offs with it then.

I found this remark very interesting because, in my estimation, the Ta 152H would have been a real bear to maneuver at lower altitudes because of the denser air combined with such a large wingspan. But, in closely checking the story of the 152H, I found that the sucker had Flettner tabs on the ailerons. So that would have helped considerably. But, in the 109s with aileron Flettners, pilots complained that at low speeds the control forces were little more than the control friction force, and so it was easy to overcontrol the a/c. I wonder what the aileron control forces were like in the Ta 152H at various speeds and altitudes. And, was there concern about tearing off the wings at high speed and low altitude?

[George Hopp]

I don't have any costs for the 109K, but here are the "Fertigungsmittelkosten" (Assembly costs [?]) for the 109G. At a rate of 200 a/c per month: Fuselage: 1,950 hours, Control surfaces: 1,050 hours; Wings: 3,000 hours; Powerplant: 500 hours; Total: 6,500 hours. At a rate of 50 a/c, the cost rose to 9,200 hours; and, at a rate of 500 a/c per month, the cost dropped to 3,800 hours. This was from a report of 11.5.44.

[Juha]

Hello Kurfürst

Your pages are very interesting as is Your message on 2000hp DB 605s. Have You seen the article on DB 600 series engines in Aeroplane Monthly May 2005? IIRC it seems to emphasis the importance of sparking plugs in achieving the 1850 and 2000hp in late DB 605 models.

On 109K, IMHO its worst feature was low permitted Vmax for a 1945 fighter. In Finnish manual for Bf 109 G-2/6 the Vmax permitted was 750km/h. It also warn that extra carefulness was needed when coming out from high speed dive because the risk of structural damage. Even with 1310 hp DB 605A (most if not all first line Finnish Bf 109Gs had restricted to 1,3 ata) it was not difficult to excess the Vmax. Finns had used high speed dive as a mean of disengagement since Fokker D.XXIs used it in Winter War). Many lived to tell the story but not all. I have also seen a pilot manual for Bf 109G/AS, date Aug. 44, which gave permissible Vmax as 750km/h at 0-4km altitude, 700km/h 4-5km, 600km/h 5-?km and 500km/h ?-?, I cannot remember the higher altitudes. The speed should be IAS. I don’t know the position error of Bf 109’s speedometer, so I cannot convert the speeds to TASs. Can You help me in this?

Finns seemed to have thought that Bf 109s wings and horizontal tail surfaces were rather weak and the heaviness of controls at high speed was a kind of protection against structural failures because of too harsh movements at those speeds. In fairness Finns also thought that probably Soviet fighters had even lower permitted Vmax because Bf 109s usually could rather easily disengage with high speed dive if altitude allowed that but heavier and more robust planes like Tempest had far greater permissible Vmax and had much lighter controls at very high speed (over 650km/h).

That said 109K should have been able to use its steep climbing ability to turn tables in tight spot. For example, IMHO the steep climbing spiral was an effective combat movement when used against poorer climber.

Juha

[Kurfürst]

Originally Posted by Juha

Hello Kurfürst

Your pages are very interesting as is Your message on 2000hp DB 605s. Have You seen the article on DB 600 series engines in Aeroplane Monthly May 2005? IIRC it seems to emphasis the importance of sparking plugs in achieving the 1850 and 2000hp in late DB 605 models.

Unfurtunately not, AM isn`t available here (hardly any foreign magazine is), but it sounds interesting and I`d love to read it. If it`s possible, could you take me a few shots on the article and send it to my mail address at kurfurst@atw.hu?


On 109K, IMHO its worst feature was low permitted Vmax for a 1945 fighter. In Finnish manual for Bf 109 G-2/6 the Vmax permitted was 750km/h.
...
I have also seen a pilot manual for Bf 109G/AS, date Aug. 44, which gave permissible Vmax as 750km/h at 0-4km altitude, 700km/h 4-5km, 600km/h 5-?km and 500km/h ?-?, I cannot remember the higher altitudes. The speed should be IAS. I don’t know the position error of Bf 109’s speedometer, so I cannot convert the speeds to TASs. Can You help me in this?

IAS and TAS are greatly different things, as a rule of thumb, decrease TAS vs. IAS by 10% for every 1500m altitude, but that`s pretty rough....

If you refer to here : http://www.pbase.com/isegrim/image/5288901, you`ll see how it works. Ie. you noted 750 kph IAS for 0-4 km altitude, where the G-2 would obtain only 492-525 kph in level flight. I also believe Mtt was quite conservative in his limiations, for the known Lukas Schmidt dive reached something like 890 kph TAS on a 109F without trouble, and they dared 906 after limiting aileron deflection, which isn`t really structural but compressibilty related with the Frise ailerons.

Results plotted vs. limitations :



As for the 109K, the diving limitations were increased over the 109G to 850 kph or 527 mph. That`s a pretty high figure imho even for 1945. The limitations are given in the 109K handbuch, 850 kph TAS at SL w. or w/o gondolas, and 800kph TAS at 10 kph - the 109K had altitude compensating speed gauge with two, TAS and IAS needles, and the limit was given in TAS.

[Juha]

Wunderbar Kurfürst

I'll will try to take a passable photo on the DB 605 page(s ) but not on whole article for not to breach too badly the writer's copyright. And I'll give the bibliobraphic data also. please give me day or two for doing that.

What is the source of the most interesting table? I knew the max. Mach number reached from one of my friends but haven't see the table before.

Why was it possible to increase the diving limitation so much for K? I cannot recall any significant reinforcement of structures in K when compared to G. But my knowledge on K is pretty limited.

Juha

[Kurfürst]

Thanks. You can find the report on the 109lair, I think along the tail unit changes stuff, but if not, I can email you.

As for why the change, I don`t know, perhaps because the undercarriage was to be fully retractable and covered on the 109K. Dive limits are more of a function of aerodynamics, rather than raw structural strenght..
But there`s more conservatism involved imho than pure technical neccesity - it`s enough to look on the fact that all 109F and G models, despite quite a variaton between them aerodynamically, had exactly the same dive limits.