Question: Why is the BF109-G4 16km/h slower than the G2 at 7000m / combat power?

[kraut1]

Hi all,

I would like to know the reason for this from my point of view comparable big difference.

The G4 is only ca. 20kg heavier than the G2, this is not the reason.

And the armament is the same.

Had the new landing gear design a much higher air resistance?

Using combat power in air combat is very importent because it can be used for 30minutes.

G2 v at 7km / 1,30ATA / 2600rpm = 656km/h, empty weight 2486kg, standard weight 2994kg

G4 v at 7km / 1,30ATA / 2600rpm = 640km/h, empty weight 2506kg, standard weight 3014kg

Many Thanks in advance

Edited June 19, 2024 by kraut1

[Hanu]

Retracting tail wheel is the only possibility I can think of. The difference is however quite big, true.

[the_emperor]

There should not be that much of a difference as the drag penalty from drag due to the non retractable tailwheel is greatest at sea level and decreases with altitude.

how did your measure those speeds in game?

[Roland_HUNter]

I calculated in the past, the fixed tail wheel causing around 5-7 km/h loss because of the drag.
But, I do not think so, the wing bulge, because of the new landing gears, should cause 9 km/h drag.

[Roland_HUNter]

I did a double check on this, I think the manual numbers are wrong or outdated.
In the IL-2 app:

 

The difference between the two machines at sea level is 9 km/h.
Also at 1000 metres.
At 3000 metres, 6 km/h.

 

[kraut1]

1 hour ago, Roland_HUNter said:

I did a double check on this, I think the manual numbers are wrong or outdated.
In the IL-2 app:

 

The difference between the two machines at sea level is 9 km/h.
Also at 1000 metres.
At 3000 metres, 6 km/h.

 

Thanks very much! I have never used this app. Very interesting! On weekend I will make a test flight.

[Roland_HUNter]

In game, Kuban, Summer 7.000 Meter.
G-2 on combat, 15% radiator: 460 km/h (IAS)
G-4 on combat, 15% radiator: 453 km/h (IAS)
Bulges+fixed tail wheel: -7 km/h.
But, G-4 has emergency:
461 km/h with that.

[the_emperor]

1 hour ago, Roland_HUNter said:

n game, Kuban, Summer 7.000 Meter.
G-2 on combat, 15% radiator: 460 km/h (IAS)
G-4 on combat, 15% radiator: 453 km/h (IAS)
Bulges+fixed tail wheel: -7 km/h.
But, G-4 has emergency:
461 km/h with that.

that is ~ 10kph true airspeed difference seems about right.

I know for us keybord warriors every kph counts but those are speed differences are in the 1% range...a bad airframe, surface finish, worn out engine or dirt collected on take off would probably have eaten much IRL

[kraut1]

12 hours ago, Roland_HUNter said:

In game, Kuban, Summer 7.000 Meter.
G-2 on combat, 15% radiator: 460 km/h (IAS)
G-4 on combat, 15% radiator: 453 km/h (IAS)
Bulges+fixed tail wheel: -7 km/h.
But, G-4 has emergency:
461 km/h with that.

 

10 hours ago, the_emperor said:

that is ~ 10kph true airspeed difference seems about right.

I know for us keybord warriors every kph counts but those are speed differences are in the 1% range...a bad airframe, surface finish, worn out engine or dirt collected on take off would probably have eaten much IRL

Thanks very much for your answers!

I think in respect of my next BF109-Gx careers / campaigns:

G2: at full throttle derated by default to combat power: comparable good speed, with ca. 30 minutes no time limit problems.

late G6, G6 ASM, G14,... if equiped with MW50 (in the defind altitude for MW50) 10minutes with emergency power possible, okay

E7, F2, F4, G4, G6, G6late without MW50: very short emergency power time of 1...3minutes, as I have already tried 1time I will try find a rating (ata / rpm) a bit higher than combat (30minutes) that allows an increased performance for min. 10minutes without overheating with realistic automatic cooler control (exept of E7 / manual cooler).

[Roland_HUNter]

7 hours ago, kraut1 said:

 

Thanks very much for your answers!

I think in respect of my next BF109-Gx careers / campaigns:

G2: at full throttle derated by default to combat power: comparable good speed, with ca. 30 minutes no time limit problems.

late G6, G6 ASM, G14,... if equiped with MW50 (in the defind altitude for MW50) 10minutes with emergency power possible, okay

E7, F2, F4, G4, G6, G6late without MW50: very short emergency power time of 1...3minutes, as I have already tried 1time I will try find a rating (ata / rpm) a bit higher than combat (30minutes) that allows an increased performance for min. 10minutes without overheating with realistic automatic cooler control (exept of E7 / manual cooler).

My advices:
1.For more emergency time, use 93% for the 1 mins (U can used the 93% for 3 minutes and you can almost reach the full speed)
2.Always use manual radiator on 109s. On Summer 15-20%, on Autumn 10-15%, at Winter 5-8 %.
The automatic radiator flaps are causing high drag, and can make you stall in low speed dogfights and can decrease your climbing ability. (you lose 50 km/h when the rads are fully opened---> 

And this is historically accurate.

So as I mentioned, if you are on low speed, and the rads start to opening, it will decrease your speed and it will bank the plane to the left. This moment could cost you your life!

The thermostate will open the rads on 100 C°, but the engine can stand with 115C°.
And the auto radiators are a little big bugged.
I did a dive with 700 km/h, and I started climbing, When I reached the "top" the radiators were fully opened under 100 C°.
The P-51 has the same "issue". 

[kraut1]

1 hour ago, Roland_HUNter said:

My advices:
1.For more emergency time, use 93% for the 1 mins (U can used the 93% for 3 minutes and you can almost reach the full speed)
2.Always use manual radiator on 109s. On Summer 15-20%, on Autumn 10-15%, at Winter 5-8 %.
The automatic radiator flaps are causing high drag, and can make you stall in low speed dogfights and can decrease your climbing ability. (you lose 50 km/h when the rads are fully opened---> 

And this is historically accurate.

So as I mentioned, if you are on low speed, and the rads start to opening, it will decrease your speed and it will bank the plane to the left. This moment could cost you your life!

The thermostate will open the rads on 100 C°, but the engine can stand with 115C°.
And the auto radiators are a little big bugged.
I did a dive with 700 km/h, and I started climbing, When I reached the "top" the radiators were fully opened under 100 C°.
The P-51 has the same "issue". 

Thanks very much!

As far as I can remember I have used sometimes in IL2 1946 for the G2 manual cooler control too, because it was opened too early.

 

[the_emperor]

20 hours ago, Roland_HUNter said:

The thermostate will open the rads on 100 C°, but the engine can stand with 115C°.
And the auto radiators are a little big bugged.
I did a dive with 700 km/h, and I started climbing, When I reached the "top" the radiators were fully opened under 100 C°.
The P-51 has the same "issue". 

 

yes, the radiators in game for should start opening at 102C. in game it seems they open a bit to early...

the P-51 seems also a bit bugged...

but overall low speed cooling seems far to effectiv accross all nations (as is low speed controll surface effectivness)...

[Kurfurst]

On 6/19/2024 at 7:56 AM, kraut1 said:

Hi all,

I would like to know the reason for this from my point of view comparable big difference.

The G4 is only ca. 20kg heavier than the G2, this is not the reason.

And the armament is the same.

Had the new landing gear design a much higher air resistance?

Using combat power in air combat is very importent because it can be used for 30minutes.

G2 v at 7km / 1,30ATA / 2600rpm = 656km/h, empty weight 2486kg, standard weight 2994kg

G4 v at 7km / 1,30ATA / 2600rpm = 640km/h, empty weight 2506kg, standard weight 3014kg

Many Thanks in advance

 

The (short) non-retractable tail wheel costs -12 kph/h at sea level (cc. 50% more at full throttle height).

[Roland_HUNter]

1 hour ago, VO101Kurfurst said:

 

The (short) non-retractable tail wheel costs -12 kph/h at sea level (cc. 50% more at full throttle height).

Do you have the same report about the G-6 Mg131 bulges?
Based on my test -12 km/h was my result.

[Kurfurst]

3 hours ago, Roland_HUNter said:

Do you have the same report about the G-6 Mg131 bulges?
Based on my test -12 km/h was my result.

 

The most relevant part of the report is here: Kurfürst - Leistungzusammenstellung Me 109 G. (kurfurst.org)

 

The MG 131 bulges added 40 kg and decreased speed by 9kph, and, about 50% more in full throttle height (this is pure added drag decrease, the weight increase decreased speed by a miniscule amount as well).

 

I think the devs have this compilation of the effect of various modifications so it looks quite correct.

[kraut1]

On 6/23/2024 at 7:08 PM, VO101Kurfurst said:

 

The most relevant part of the report is here: Kurfürst - Leistungzusammenstellung Me 109 G. (kurfurst.org)

 

The MG 131 bulges added 40 kg and decreased speed by 9kph, and, about 50% more in full throttle height (this is pure added drag decrease, the weight increase decreased speed by a miniscule amount as well).

 

I think the devs have this compilation of the effect of various modifications so it looks quite correct.

Thanks, very interesting, especially that the from my point of view big cannon gondolas under the wings cost only 8km/h and standard bulges for the MG131 9km/h.

[FTC_ChilliBalls]

I still don‘t get why they needed those ugly bulges for the G6 when Adolf Galland had 131s installed to his 109 F2 with way smaller bulges.

 

Either they weren‘t feasible with the G airframe or they caused some sort of issues. 

[BENKOE]

I don't agree. The dynamic pressure is the only directly measurable quantity that relates to the aircraft's speed with respect to the air, expressed as airspeed.

So, under standard conditions, 12 km/h indicated airspeed at Mean Sea Level produce the same dynamic pressure q(h,TAS) as 12 km/h indicated airspeed at full throttle height.

 

On 6/23/2024 at 1:37 PM, VO101Kurfurst said:

 

The (short) non-retractable tail wheel costs -12 kph/h at sea level (cc. 50% more at full throttle height).