109G2 radiators

[FTC_Blaky]

In the book "Messerschmitt BF-109: 1935 onwards" there is as very specific piece of info saying: "...under cold conditions you can fly at 1.0 ATA with radiators closed..." This is specifically for restored G2 with original engine. I tried to do it in BOS in winter map, but engine overheated fast. Is there any other info about how fast the engine in G2 overheated or is this wrongly modelled? 

Edited June 16, 2016 by II./JG53_Wolf_Ettel

[Kurfurst]

The cooler effiency seems a bit low for winter conditions (keep in mind though you cannot fully close the radiators!, the standard was about 40-50 mm open on the exit flaps)

 

These are trials for G-2 at 1,3ata combat, and 15 Celsius conditions. The curve at the bottom shows the temperature (Y) vs coolant radiator opening (X). Basically, the indenfietely allowed 102 degrees Celsius could be held at about 40-50 mm opening in high speed level flight at 2000m. 

 

The tested aircraft is semi-standard testbed however, it has a left cooler out of copper (with better cooling properties) and a standard aluminium right cooler.

 

 

[FTC_Blaky]

OK, so the info seems wrong (but why would a real pilot talking about a real plane make such a mistake). Just thinking loudly - the power is at about 60% (1.0 ATA) and the temperature at about -20 degrees, wouldn't just the airflow be enough to keep the engine cool? I am not a technician, so I don't know. Because 1.3 is basically 100% in what we have available (and temperature is higher and the radiators are open very little). What do you think? Btw. 50 mm should be 10% translated to technochat, isn't it (440 mm is fully open, when 220 mm is half)? 

[Kurfurst]

AFAIK the opening limit was 360 mm. 220 was about 2/3s, 50 mm would be around 14%. The system itself seems to have been designed around to keep the temps at an optimal 85 degrees celsius coolant temp under temperate conditions, even in climb, with a 1/2-2/3s radiator opening.

 

I am quite certain that in these conditions you flew at, ie. 1 ata cruise and outside tempereature of -20 Celsius... the engine should run extremely cool and not 100+ Celius. Since it seems there is some trouble with the thermodynamic model and that the cooling capacities of the 109G are definitely on the low side, I am not sure if for the full range of radiator opening, but the bug is definitely for small openings.

 

Perhaps the cooling capacity is linear in the sim, and was non-linear in real life.

[Dakpilot]

"(but why would a real pilot talking about a real plane make such a mistake)"

 

I know many very experienced pilots and test pilots, they very often make mistakes about Aircraft specs and suchlike, talk to 3 Pilots who flew the same type of aircraft for years and often you can get 3 different stories 

 

Most Pilot 'anecdotes' are often generalisations to some extent, it is simply human nature, this is not a criticism of such info, it can be very useful, but not the same as recorded data, which itself can be misleading when only relating to a single aircraft in a very explicit set of circumstances/conditions..

 

Of course I am generalising as well   and also far from infallible when remembering details of aircraft I have flown

 

Cheers Dakpilot

[JtD]

I don't know if this has recently been remodelled, but last time I tested the performance of the 109 cooling, it was extremely poor compared to the sources I found. The developers claim they base their 109 cooling effectiveness on some "African curve" (or so, feel free to dig up the original statement), which I haven't seen. They introduced it when they introduced non-linearity in cooling effect. That said, radiators completely closed with no airflow through water and oil radiators, will overheat the engine under pretty much all conditions.

 

There's quite a bit of info on 109 cooling on http://www.wwiiaircraftperformance.org. Kurfurst also has good info on the subject.

[Matt]

 

 

I don't know if this has recently been remodelled, but last time I tested the performance of the 109 cooling, it was extremely poor compared to the sources I found.

 

That has been fixed.

 

In cold conditions, you can fly around with 5% open radiators with 1.3 ATA at ground-level. But it's doesn't work to compare fully closed radiator performance, because you can fully close the radiators in BoS, which shouldn't be practically be possible. If you fly at 2000 meters at +15°C with 1.3 ATA and fully open radiators, you'll reach an cooling temperature between 70 and 80°C, which is in pretty good agreement with the source.

[JtD]

Thanks for the update, Matt!

[FTC_Blaky]

Thanks for answers gents. May be the answer lies in what Matt wrote - that the radiators shouldn't be possible to close fully, I mean 0%, because 5% responds to 18 mm, which is practically closed... So far it seems that those 5% corresponds with that winter setting. 

@Dakpilot - I know what you mean, but in this case it was a very specific technical piece of info with only one unknown point - cold weather. IMHO, it is completely different from notes like:"... nasty stall characteristic..." 

As I am not good in German I asked people who I believe know more about the subject. For me it seems solved, thanks.

Edited June 16, 2016 by II./JG53_Wolf_Ettel