109 and compression!!!

[-ik-]

crunch, could you please post the numbers and source which lead you to say the 109G-6's powerloading shot off the charts compared to the 109F? If you're talking about a 109G-6 with MW50, well then I agree. But remember that MW50 would not effect top speed at altitude. From everything i've read the 109G-6 with MW 50 was significantly (about 30mph) faster than the 109F at lower altitudes.



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[Drum]

   Ooops, sorry about that "rudder" trim mix-up.  Your right, that should have read elevator trim.

[fats]

Sink:

I belive you're correct, it's a Flettner tab. The two fixed trim tabs weren't always present though.


//fats

[wells]

The 109 issue...here's what theory predicts.  The estimated speeds at altitude will be slightly underestimated because the difference in IAS is not factored into the thrust calculation.  Thrust will be slightly higher as the IAS is lower.

I'm assuming that 1475 hp and 317 mph are correct sea level figures for the G.

With DB605A (data from Jane's):
 
1355 hp @ 5700m = 280 mph IAS (374 mph)
If MW50 provided a 4% increase in power for a constant boost, then we get this...

with MW50,

1409 hp @ 5700m = 284 mph IAS (379 mph)

With the 605AS engine (higher critical altitude):

1200 hp @ 7800m = 257 mph IAS (392 mph)

with MW50,

1248 hp @ 7800m = 260 mph IAS (397 mph)

IF GM-1 restores power at 7800m to the sea level figure of 1475 hp

1475 hp @ 7800m = 275 mph IAS (420 mph) <---109G-10?

If both MW50 and GM-1 are used and power is restored to a whopping 1800 hp at 7800m.

1800 hp @ 7800m = 294 mph IAS (449 mph) <---K4?

I need to do more research into GM-1 and how effective it was at restoring power.

[juzz]

Wells: the last two figures where you point G-10 and K-4 has nothing to do with the reason they reach coincidentally similar top speeds, after all; both have vitually the same engine (and different from the DB605A) and the K-4 has better aerodynamics than the G-10 - giving it the better speed.

Bf109K-4(G-10)
Powerplant: DB605ASCM(DB605DC, 2000hp at ?) producing 2030hp at 500m, 1800hp at 5000m.
Speed: 378mph at S/L(342mph), 452mph at 6000m(426mph at 7000m), 435mph at 7500m.
Climb: 5000m in 3 minutes, 10000m in 6.7 minutes, 12000m in 10.2 minutes! Fast enough?

GM-1 increases the oxygen available for combustion over the percentage in "normal" air. (N20 = 33% O) So GM-1 would work the same at any altitude(unless O % decreases with altitude?), but MW50 must be more efficient at low altitude. I think...

I want GM-1 so I can get those damn B-17's. And the Spitfire should have LF and HF versions too, not the current weak F version  

[juzz]

Here's fun. Me 109 Wk. Nr.9228, coded TH+TF. A Me 109F model with modifications; fitted with Me 109G wings, ailerons limited to 50% travel, catapult seat and various recording cameras and instruments.

 

 The next four flights followed with a trim setting of 1º15'. With this trim setting, one had to overcome high forces by pushing forward on the stick during the start of the dive. These forces reduced to zero at the recovery point of the dive. By pulling smoothly but firmly, the aircraft recovered safely. During these dives I was able to increase the indicated air speed to more than 700km/h(435mph), but only to a point beyond which a further increase did not seem feasible.

As mentioned above, I had increased the initial altitude for the dives to 10,000 metres (32,809ft), which enabled me to reach maximum speed at an altitude well above 5,000 metres (16,405ft). As a result, I reached more than Mach 0.8, i.e. in excess of 900km/h(559.2mph) true airspeed. Whenever this speed was reached, the aircraft started the rolling motions previously described, giving me the jitters every time. I was travelling at a speed nearly 200km/h(125mph) faster than Fritz Wendel during his (horizontal) record flight with the Me 209. This phenomenon is best described thus: The aircraft would begin to bank slightly to the right, which I was able to counteract using aileron. Without prior warning, the forces reduced and suddenly reversed. The roll to the left then had to be counteracted. Just as I had it under control, it flipped to the other side again. These pendulum type movements continued until the speed had been reduced during recovery. If aileron deflection had not been limited to half the value of normal travel, the overcompensation of the ailerons could have cost me my neck. By modifying the ailerons, Messerschmitt was able to reduce the phenomenon to a tolerable minimum.

On 16th March(1943), I made my twenty-sixth, twenty-seventh and twenty-eighth dives with the Me 109G Wk. Nr.9228. In my final report I declared the task completed, and summed up as follows: 'Achieved maximum values with an initial altitude of 10.7 Km(35,106ft) above sea level and an in-flight weight of 2,900kg(6,380lbs). The dive was initiated by rolling in at a speed of Va = 240km/h(149.1mph). The elevator trim was set to +1º15' and the engine performance at 100 per cent. The dive angle was approximately 70º-80º(reported by the pilot) maximum indicated airspeed: Va max = 737km/h(459mph) at 4.5km(14,764ft) altitude. Maximum true air speed reached, Vw max = 906km/h(563mph) at 5.8km(19,029ft) altitude. Maximum Mach number reached: M max = 0.805 at 7.0km(22,966ft) altitude.'

Lukas Schmid, from Test Pilots by W.Späte.

[This message has been edited by juzz (edited 01-05-2000).]

[niklas]

i have three pictures published now on my website. They show climb and speed, mostly for the 109K. I know the 109K is better than a 109G10, but i think it´s interesting to see the engine characteristic of the DB605D.

There are also some graphs for gondolas and use of gm1. Gondolas seems to give you about 200ft/minute less climb performance.

So the critical altitude for the DB605D without MW50 is still to low in AH. Should be at least in 8500m (28000ft)for climb, for speed even higher. I made a quick test and i think it´s still in about 20000ft here
With such a low critical altitude our 109G10 here is definitly not a high altitude fighter.
And GM1, yes i want it too!

So have a look. The graphics have a seize of about 100K each. Better print them out.
 http://www.stud.mw.tum.de/~sl1/testdata.html

niklas

[fd ski]

If i recall correctly only Ta 152 sported both GM1 and MW 50 - someone please correct me ?



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Bartlomiej Rajewski
S/L fd-ski Sq. 303 (Polish) "Kosciuszko" RAF
   www.raf303.org  

[Stiglr]

I think you're right, fdski, that GM-1 and N02 were not installed on the same planes.

In AH, I would think they should be available as different "loadouts", depending on the action you were expecting.

[wells]

MW50 was supposed to be standard on the 605D engine and I really don't believe that the G-10 could hit 429 mph without GM-1 as well.  GM-1 seemed to have raised the power by 300-400 hp or so above critical altitude, so I don't think 1800 hp is attainable.  If I use 1534 hp (GM-1 restores power to 1475, then MW50 provides a 4% boost), then speed becomes

279 mph IAS (426 mph TAS) @ 8000m

Is that a coincidence?  It's close enough for me.

[juzz]

So how come G-6's with GM-1 did 406mph at 8500m? Not 420mph like your calculations show.

What exactly are the differences between these engines (in brackets what info I have - injection/boost, hp, model of Bf109) and does anyone have "normal" and "boosted" hp numbers for them. Somehow I doubt the DB605D only made 1475hp without using any injection/boost...

DB605A (standard, 1475hp, G-0)
DB605A-1 (??, ????hp, G-1)
DB605AM (MW50, 1800hp, G-6)
DB605AS (bigger supercharger, ????hp, G-6)
DB605ASOM (MW50 and 93 octane, 2000hp, G-6)
DB605ASCM (MW50, 2000hp, K-4)
DB605D (??, ????hp, G-10) - was there a plain "D" engine?
DB605DB (GM-1, ????hp, G-10)
DB605DC (??, 2000hp, G-10
DB605DBCM (GM-1, ????hp, K-2)
DB605L (two stage supercharger, 1700hp, 1350hp at 9500m, K-14 = 451mph at 37500ft  )

[wells]

 

So how come G-6's with GM-1 did 406mph at 8500m? Not 420mph
               like your calculations show.

That was a G-2 using the 605A engine.  My calcs were for the AS engine,  which maintains power a bit higher.  I suspect the power output was a bit lower on that test, probably 200 hp or so.

The differences are.  

605A - standard engine (1475 hp with 42" Hg)
605AM - MW50, otherwise, same as A
605AS - increased supercharger (higher critical altitude, otherwise, same as A)
605D - MW50 and supercharger from AS as standard equipment.
605DC (96 octane fuel)
605DB (87 octane fuel)

There is nothing in the engine designation to indicate that GM-1 was used.  That was in the aircraft designation or part of a R kit.  Example:  109F-4Z <-- Z means GM-1 and I forget what R number also corresponded to GM-1, R-2?

[juzz]

I think the problem is you don't exactly know what effect GM-1 has on power output? I think it will increase hp at any altitude for the same power settings. Take a look at niklas' website - the speed graphs are very interesting, especially the G-6 top speed...

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When the light was right it was actually possible to see the 30mm(1.18ins) shells in flight. - Heinrich Beauvais(Test Pilots, W.Späte).

[wells]

Wow, that explains everything!  What doesn't make sense though, is that the AS on the G5 apparently has a lower? critical altitude.  Could those lines be mis-labelled for the G6 and G5?  That would make more sense...

It also looks like the high-altitude pressurized fighter (G5) got the AS engine.

[juzz]

Your reading it wrong, I think?
_____ _ = 109G6 DB605A (critical alt = 6600m, 620km/h)
_ _ _ _ = 109G5 DB605AS (critical alt = 8300m, 664km/h)

and....
_______ = 109K4 DB605D (with GM-1 = 717km/h at 11700m  )