Accuracy of flight model ?

[I/JG2_Saladin]

[unreasonable]

I take it you mean that at 2300rpm the ata should be higher than that shown in the lower BoS picture.

 

Couple of points: you might want to move this to the flight model forum section where you have a bit more latitude. Also the comparison would be clearer if the top picture was also of 2300rpm. Then we could see if the ata was the same or different and for that matter if the prop is in the same position. 

[I/JG2_Saladin]

Thanks for answer if you can move it for me it will be great !

 

I make my tests with auto prop and the RPM is the result of ATA + Altitude like indicated tn the historical manual of the 109 G2 so  i comapred the tow aircrafts in IL2 1946 and BOS and great was my surprise !

[6./ZG26_5tuka]

I think I know what you are referring to. In the Fw 190 there's a great drop in ata while climbing above 2km during the compressor switch. If you than increase throttle to keep your ata constant the RPM increases with it (Kommandogerät ingame does seem to adjust RPM only by reading throttle leveler position and airspeed).

 

I don't know if this is correctly simulated ingame and how the Kommandogerät used to adjust RPM in detail, but I'm sure you'd get different results at a lower altitude.

 

There's another bug with the G-2's Kommandogerät. If you increase your throttle up to ~ 3/4 or below while rolling or during take off it will always reduce prop pitch back to 8:30. If you than increase throttle it rotates back at 12:30. The same thing can be observed on the Fw 190, not the 109 F-4 though.

Edited July 16, 2015 by Stab/JG26_5tuka

[unreasonable]

I think I know what you are referring to. In the Fw 190 there's a great drop in ata while climbing above 2km during the compressor switch. If you than increase throttle to keep your ata constant the RPM increases with it (Kommandogerät ingame does seem to adjust RPM only by reading throttle leveler position and airspeed).

 

I don't know if this is correctly simulated ingame and how the Kommandogerät used to adjust RPM in detail, but I'm sure you'd get different results at a lower altitude.

 

There's another bug with the G-2's Kommandogerät. If you increase your throttle up to ~ 3/4 or below while rolling or during take off it will always reduce prop pitch back to 8:30. If you than increase throttle it rotates back at 12:30. The same thing can be observed on the Fw 190, not the 109 F-4 though.

 

The 190 KG's drop in ata is correctly modeled - the drop is just as shown in bench tests, starting at critical altitude for 1st stage then disappearing as the gear changes. The control lever determines rpm, not ata.

 

I do not know if 109's controls work the same way, but given that the OP's test is (G2s?) all at 5.8km altitude we must be in high gear already but not yet above critical altitude for 2nd stage - I would think, but I do not know what the critical altitudes are for a G2. So fluctuation due to gear changes, if any, should be over.

 

The question is why the ata shown is quite a lot lower than what the manual says for 2300rpm in the BoS case. (I have no idea! But there might be a perfectly good reason). Also what difference, if any, it makes to the performance of the plane.

 

As I said comparing the two screenshots would make more sense if they were of the same rpm in the different sims.

[JtD]

It's been said and documented many times, the boost on the G-2 is bollocks in many ways. Relation to throttle position, behaviour over altitude...

 

Unfortunately, Han has stated "topic closed".

[Matt]

The 109 engine only has one gear.

Not sure how the above test was done (standard atmospher conditions?). I'm also not 100% sure how the prop governor worked though, could be that those parameters are only valid for standard atmosphere conditions.

[sport02]

BOS :

 

2100 tr/m

1 ATA

5700 m

[RydnDirty]

Bf109 has a hydraulic coupled supercharger . No gear changes and hence no step in the ata like the FW190 when it's supercharger changes gear.

 

 . I think the critical altitude is 5.7km altitude for bf109G2 from memory. Thats why its says 5.7km on the document. So any higher than this and the ata pressure will drop off.  

 

He tested the F4 (top pic) at 5.8km just above critical altitude. And tested the G2 at 6km. Well above critical altitude.

 

I Think he is wondering why the two bf109 , the F4 and G2 are giving different engine values. Is he aware they have different engines?

 

 F4 has a DB601 

G2 has a DB605

 

No surprise they have different critical altitudes.

Edited July 22, 2015 by WillyZurmacht