Time Machine Consultant : Maximizing the Bf-109 in January 1943

[Altea]

Originally Posted by Civettone

I don't think the C3 ...
Kurfurst had a say about it ... Axis History Forum • View topic - 87 octane fuel vs. 100 octane !

Kris

Kurfurst said you say... but from

- P.Wilkinson, Aircraft engines of the world, NY 1944. the german C3 has 93 octanes number
- from TsAGI the C3 it's quoted 94
- from TsIAM it's measured at 93, from soviet CFR test (variable volume cylinder)

So the so called 100 octanes german fuel behavior reminds highly questionnable, at least...

[Altea]

Actually it is the combination of compression ratio AND boost that requires high octane.

Think of 2 engines, one with a 7.5 compression ratio and using 1.5 ata of boost and the other 6.0 compresion ratio and 2.0 ata of boost.
Combining the two factors together gives 11.25 for the first engine and 12.0 for the second. if every thing else is the same they are going to need similar fuel.
I know it doesn't work exactly like this but I am trying to keep it simple.

Thank's for good common sense.

Just my five cents: There is some compress loss from the supercharger to cylinder, transformed to turbulence losses, that means extra heat...So i would say 10.13 for the first case, 10.8 for secund if you don't mind...

Regards

[davebender]

If the Me 155 of davebender was to get the enlarged wing and heavier weight of the guns it would be slower than the standard Bf 109. Right dave?

That depends on aerodynamic issues. The P-51D was heavier then a Me-109G6 yet it was a bit faster.

[Civettone]

As the rest of the Bf 109 was left unchanged (perhaps except for a taller tail) )but the wing area increased while the chord did not diminish I find it logical that the speed would decrease.
The P-51 was faster because it had laminar wings, the Monroe effect and a good aerodynamical profile in general.

Kris

[davebender]

The CV version had a greater wing area in order to lower the stall speed, making it easier to land on an aircraft carrier. However nothing requires a land based Me-155 to be exactly the same. It could have clipped wings in an effort to keep the wing area similiar to the Me-109G. You still have wide track landing gear and room in the wing root for a cannon.

[Shortround6]

Putting the landing gear out in the wings retracting inwards would require slightly heavier wing structure to handle the load. The heavier armament will increase weight. Performance will not be as good as a standard 109 but perhaps better than a 109 with underwing gondolas?

[davebender]

Performance will not be as good as a standard 109 but perhaps better than a 109 with underwing gondolas?

That's pretty much what we are aiming for. We also improve capability to operate from rough and/or muddy airfields.

Personally I would delete the 2 cowl mounted machineguns. You don't need them if you have 3 x MG151/20 cannon. That will save a bit of weight and possible allow for aerodynamic improvements.

[Bronc]

Quoted from Messerschmitt Bf-109 by Robert Grinsell, specifically writing about the
Bf-109G:

"...the increased weight of the [engine] and added armament reduced speed and handling
characteristics and made the landing of the aircraft extremely hazardous to fly in inclement weather,
especially at night. [...] Equipment malfunctions, structural failures due to fatigue, and pilots bailing
out rather than trying to land in dangerous and potentially fatal conditions, rapidly reduced the available planes..."

Fellars, when your combat fighter pilots would rather JUMP OUT of their airplanes instead of trying
to land them, THERE IS SOMETHING WRONG WITH THAT AIRPLANE. PERIOD.

The Me-155B with the DB-628: was 50-75 mph faster than the Bf-109G, was armed with (3) three 20mm MG-151/20 cannons, was operating routinely
in test flights at 50,000 feet, COMPLETELY ELIMINATED the Me-109's NOTORIOUS takeoff and landing characteristics and it was ready for series production in January 1943.

The RLM chose not to build the Me-155B, but also, and most incredibly, they walked away from the
DB-628 as well...

Bronc

[davebender]

Me-109 G6. Most common model.
Messerschmitt Bf 109 - Wikipedia, the free encyclopedia
6,940 lbs Loaded Weight.

P-51D. Most common model.
P-51 Mustang - Wikipedia, the free encyclopedia
7,635 lbs. Empty Weight.
9,200 lbs. Loaded Weight.

As you can see the Me-109G6 was a very light aircraft. It weighed less loaded for combat then the P-51D weighed empty. I suspect the Me-155 also weighed considerably less then a P-51D.

[Civettone]

The underwing gondalas created a 8 kmh decrease in maximum speed.
Though extra guns are nice for attacking the bombers, I find it unncessary to change Bf 109 production completely to the Me 155. On the front lines they didn't need a fighter with great high altitude performance nor with better armament.
That's why a standard Bf 109 with removable underwing gondalas was sufficient.
I suppose that's also why the Germans later went for the Bf 109H with only had the longer wings and the new engine.


Now, one more time about the Me 155B (with the DB 628 ). The Bf 109H was similar as both got an added wing section.

The Bf 109H was an attempt to design a high-altitude fighter to fill a gap in the Luftwaffe inventory left by the failure of the earlier Me 155 and Me 209 projects. The 109H was based on the same fuselage as the Bf 109G. It was to be equipped with a high-altitude pressurized cockpit. The standard 109 wings were lengthened from 9.92m to 13.25m by the addition of a rectangular central section. The Bf-109H-1s were evaluated by the Luftwaffe in France in early 1944. The trials went well, except for the fact that the aircraft demonstrated an unhealthy wing flutter in dives. Tests were conducted on some of these aircraft back in Augsburg, and in April 1944 one lost a wing during a dive. This apparently stalled the program, which was then presently cancelled in favor of the Focke-Wulf Ta-152H.

I have also read an account by one the pilots who were testing the Bf 109H in France. He thought it was the most idiotic idea ever. But I don't know why he was opposed to it. It could also have been due to the GM-1 and flying at extreme high altitude...

Now as to the DB 628. I have also said this before. The DB 628 was longer. It shifted the centre of gravity in such a way that a redesign of the wing placement was required. This led to even more changes until the design was too altered to still use a standard Bf 109 which was required for production. I have seen the diagrams of the Bf 109H with DB 628. It is quite clear. Also the DB 628 was far from ready. DB only managed to complete the DB 605D and the DB 603A during the war. All other projects failed to reach production. All of this is quite unfortunate because I think the Bf 109 with a DB 628 could have been great.



http://www.ww2aircraft.net/forum/avi...ich-15884.html (Cannons for Friedrich)
This thread also showed that the later Bf 109K-6 managed to get two cannons inside the wing, not as gondolas.
Kris

[davebender]

Kurfurst - Your resource on Messerschmitt Bf 109 performance

635 to 660 kph. Me-109F4 Max speed. The German data sheets do not agree.
632 to 664 kph. 652 kph average. Me-109G1 Max speed.

3 kph. Speed reduction from cowl mounted MG131s. With enlarged cowl made for MG131 installation.
8 kph. Speed reduction from 2 x MG151/20 wing cannon and ammunition. 215 kg additional weight.
12 kph. Speed reduction from non-retractable tailwheel.

652 kph. Me-109G14/U Max speed.
.....1 x Mk108 3cm engine mounted cannon.
.....2 x MG131 13mm cowl mounted machineguns.
.....2 x MG151/20 wing mounted cannon.
.....DB605 AM engine with MW-50.

It appears to me the Luftwaffe decided the 652 kph / 405 mph max speed of the Me-109G1 was fast enough. Higher HP engines were matched with additional firepower so max speed remained around 652 kph throughout 1942 to 1945. The Me-109G14 has plenty of firepower for knocking down heavy bombers while retaining more then adequate performance vs P-51D escort fighters. All this talk about the Me-109 series falling behind in performance is much ado about nothing.

If I were going to change something....
- Delete the two cowl mounted machineguns. Wiith three cannon you don't need them.
- Keep the retractable tailwheel. This will probably increase aircraft cost slightly.

With both these changes late war Me-109s will be 15 kph / 9 mph faster. A worthwhile performance increase with no drawbacks that I can see.

[Shortround6]

Which aspect of performance?

Top straight line speed at the optimum altitude for the engine? Which maybe several thousand feet lower than the optimum altitude for the opposing fighters?

Climb?

Which sufferes much more from weight increases than straight line speed.

Rolling ability?

Turning ability?

Both wing loading and power loading. The latter helping the fighter sustain speed in a turn.

And of course the ever popular landing and take-off performance.

Not to mention the 109s heavy controls at high speeds. Not much sense in going really fast if your control forces are so high that you have trouble out manuvereing your oposition.

Straight line performance is a rather simplistic way of comparing fighters or judging if an aircraft was passed it's prime.

[Glider]

I think the problem with the 109 when equipped with the wing cannons was more to do with handling in particular the climb, acceleration and the rate of roll. So as long as the bombers were not escorted and you have enough warning to climb to the bombers you were OK.
If they were escorted or you didn't have time then you were in trouble.

[davebender]

Perhaps this is part of the reason someone decided 652 kph is fast enough for the Me-109G.

[tomo pauk]

Originally Posted by davebender

Perhaps this is part of the reason someone decided 652 kph is fast enough for the Me-109G.

...which leads to the another question: by what time we could remove the 109 away from the Premier league of fighters? Early or late 1943? Early 1944?