Bf-109 + GM1 -performances?

[delcyros]

A good question for You Bf-109 experts.

I have run through the net but was not able to establish top speed figures for the Bf-109 variants, using the GM1 injection. Some datas I thought beeing worth to assemble:

Bf-109E7Z: ? Km/h at ? alt
Bf-109F2Z: ? Km/h at ? alt
Bf-109F4Z: 670 Km/h at 6.400m and 2.890 Kg? (Rechlin tested)
Bf-109G1: 700 Km/h at 7.650m and 3.060 Kg (Rechlin tested)
Bf-109G3: ? Km/h at ? alt
Bf-109G5: ? Km/h at ? alt
Bf-109G6/U2: ? Km/h at ? alt

 

[Kurfürst]

Bf-109F4Z: 670 Km/h at 6.400m and 2.890 Kg? (Rechlin tested)
Bf-109G1: 700 Km/h at 7.650m and 3.060 Kg (Rechlin tested)

These aren`t GM-1 figures, actually both are for 110%/WEP figures without GM-1; the F-4 is from Rechlin`s flight test, but probably not corrected for compressibility, but this can`t be confirmed.

The 700kph G-1 figure was calculated from the abovementioned F-4`s, but the conditions are not known. I`d say it`s reasonable for Notleistung/110%/WEP w/o comp. corr.

G-1 and G-3 should be identical, as their only difference was radio set fitted (HF vs VHF).

A datasheet showing the effect on the G-6/U2 is shown below, unfortunately, it`s of very poor resulution and it`s hard to figure out the exact specs.

G-6/U2

Apprx.
665 km/h at 8000meter at 100%
680 km/h at 10500 meter at 110%

Appearantly, there were a number of G-5/AS/U2 built. These must have been extremely potent high altitude aircraft..

The other is a Rechlin curve about the F-4 without, and the F-4/Z with GM - 1 injecion.

The third is graphically plotting the climb performance of GM-1ish and GM-1less variants.

Hermann Graf managed to set the new World Record in high altitude flight-14,300 meters (46,885 feet). Aircraft was Bf 109G-5/U2 iirc.

In a Me 109G-1/R2 with GM-1 (N2O injection), R. Klein had achieved 680 km/h at 12000 m and a ceiling of 13800 m.

Also (thanks to GG Hopp and HoHun)
Kurfrst - Kurz-Betriebsanleitung fr Flugzeugfhrer und Bodenpersonal fr GM 1-Anlagen in Bf 109 G.

To put it into context, the Bf 109K managed at full power 630 km/h at 12000 meters. And these GM-1 carrier planes were available in 41/42 already. The G-1/3/5 series also had pressurized cocpits, so these planes were/are the unrecognized high altitude queens.

 

[delcyros]

Thanks for correcting me and providing these informations, Kurfürst.

Do You know whether or not the -109K used GM-1 injection?

The F4Z graph mentions three seperate climb graphs: one without GM-1 equipment (black line), one with it and one with it + "Regeldüse". The latter graph shows substantial differences in climb (the GM-1 may be used starting from full pressure height and developes even more power at higher altitudes). Was the "Regeldüse" (controllduct, or something like that) later introduced or remained experimental. It appears that this would give a notable performance advantage.

 

[Kurfürst]

The 109K didn`t, there are some projected performance figures for it, but there`s no sign it ever did. It had a lare supercharger to start with, though technically it was possible.

Actually you`re right about the F-4..! Hmm, pretty interesting, how could I not notice it so far? It seems there are two kinds of GM-1 injection showned on the graph, one in which the GM-1 system works as we generally knew it - there are two, fixed rates of injection which are either on or off, hence the step at 8000m, which matches Kampfleistung / 2500 rpm and restores boost pressure. If Notleistung / 2700 rpm powered climb curves would present, there should be second one at about 9500m with another 'step', much like as a fixed ratio mechanical supercharger kicks in.

I think there just two figures present for the F-4 on the graph, w. and w/o GM-1 injection.

And there`s of course a third line, which shows the F-4 with the GM-1 using a Regeldüse, or an kind of adjustable injection nozzle I guess, which adjust the rate of injection to the exact needs probably.

I can`t say if it was experimental or not, I would be inclined to say so but there`s very little primary documentation available on GM-1 systems, and the F-4/Z in particular had two types used, so... and unfortunately, this is the only piece from that Rechlin report I have.

 

[delcyros]

Kurfürst, do You happen to have power-figures for the DB-605 variants utilized for GM-1? I would be very interested to see how the power changes. The 300 hp gain at 10Km / 8 Km seems to drop slowly using normal controll and raises notably using adjustable nozzle.
I wonder if Notleistung could be used with GM-1.

 

[Kurfürst]

Yup, there`s a DB live test on high altitude test stand. Basically its very simple, the curve looks just the same as the climb curves, a sudden increase of power by 300 PS when GM-1 kicks in around 8000, then it decreases with altittude parallel to the 'normal' power curve then the second sudden increase 1-2 km higher.

GM-1 could be definietely used with Notleistung, only at a higher alttiude. There were two rates for GM-1 injection (two nozzles/injectors), one for Kampfleistung, then as altitude increased, the second nozzle kicked in, increased injection rate to double and restored the boost again.

Look at the G-6/U2 curves for the shape.

 

[HoHun]

Hi Delcyros,

>Was the "Regeldüse" (controllduct, or something like that) later introduced or remained experimental. It appears that this would give a notable performance advantage.

I believe that there were three different systems:

1) Single jet injection: One fixed rate of injection, used a certain height above full throttle altitude.

2) Dual jet injection: Three rates of injection by using only the smaller jet, only the larger jet or both at once. These could be switched on sequentially at higher altitudes.

3) Adjustable jet injection: This would give a variable rate so that it could extract the maximum possible power at any altitude above full throttle height.

I'm not sure which systems were used on the Me 109, I've found hints that both fixed-rate jet variants might have been employed. I suspect that the adjustable jet might have been experimental only - you'd have to increase the fuel flow in parallel to the nitrous oxide flow, and I imagine it was more challenging to get this right for a variable nitrous oxide injection rate.

Normally, the power gain should be directly proportional to the injection rate - due to the high altitude, I imagine the apparent quicker drop in climb rate might be due to a decreasing propeller efficiency rather than due to powerplant concerns.

With regard to your Notleistung question, I think that 2600 rpm was preferred over 2800 rpm for the same reason - the higher tip speeds would seriously decrease propeller efficiency at the extreme altitudes we're considering.

Regards,

Henning (HoHun)

 

[delcyros]

Thanks HoHun and Kurfürst.

I have recently seen that the Bf-109E7z also received GM-1 but was unable to find anything on the net.
A mystery for me is the Bf-109H0/1, which was based on the -109F4z /-109G0 but with pressurized cockpit and different wing along other differences. Top speed is said to be 460 mp/h with GM-1, but I cannot say how well this figure is substantiated.

 

[Kurfürst]

Yes, the E-7/Z also existed from March 1941, with DB 601N + GM-1.

 

[HoHun]

Hi Delcyros,

>I have recently seen that the Bf-109E7z also received GM-1 but was unable to find anything on the net.

The early version of the GM-1 equipment relied on pressurized nitrous oxide stored in several pressure flasks aft of the cockpit. It was injected in gaseous form.

Later versions (like the Gustavs, though I'm not sure when the transition was actually made) relied on cooled nitrous oxide that was stored in the well-known 85 L insulated vessel aft of the cockpit which had to be pressurized with pressurized air to force it into the feed lines.

The cooled liquid storage had a number of advantages, including a greater power gain for the same nitrous oxide flow rate due to the additional charge-cooling effect.

A disadvantage was that the insulated vessel could only withstand a certain amount of pressure so that there was a constant loss of nitrous oxide if the aircraft had been filled and was at readiness due to the nitrous oxide slowly warming up and evaporating.

Regards,

Henning (HoHun)

 

[Glider]

This is an interesting thread. Can I ask if there is any information or details about the level of fighting that was done at very high altitude ?

 

[delcyros]

Again, thanks Henning&Kurfürst.

I believe that Gm-1 boosted -109´s were extensively used as high cover for interceptors in 44.

The US also experimentated with No2-injection as a immediate measure to improve the P-51 speed against the Me-262. And some high alt Mosquitos had them, too.

 

[koivis]

Where there any Bf 109s made (or planned) with both GM-1 and MW50?
Anyway, even if there weren't, how cool would've been a Bf 109G-5/AS/U2/R2 with MW50...

It would've had:
-pressurised cockpit (G-5 variant)
-AS engine = larger supercharger = more power at alt
-U2 = GM-1
-R2 = recce version = no MG131s? or a camera?
plus the MW50 which had no official designation in G-6s

maybe 720+ kph, ceiling 15+ km?

 

[Vincenzo]

afaik the tank was one so or MW50 or GM-1