• There seems to be an uptick in Political comments in recent months. Those of us who are long time members of the site know that Political and Religious content has been banned for years. Nothing has changed. Please leave all political and religious comments out of the forums.

    If you recently joined the forums you were not presented with this restriction in the terms of service. This was due to a conversion error when we went from vBulletin to Xenforo. We have updated our terms of service to reflect these corrections.

    Please note any post refering to a politician will be considered political even if it is intended to be humor. Our experience is these topics have a way of dividing the forums and causing deep resentment among members. It is a poison to the community. We appreciate compliance with the rules.

    The Staff of SOH

  • Server side Maintenance is done. We still have an update to the forum software to run but that one will have to wait for a better time.

Fuel and range issues

Pat Pattle

Pat Pattle

SOH-CM-2025
I've been tinkering with the '109 files trying to get the range accurate.
Based on Wikipedia the E series as used in BoB had an 88 gallon tank and a range of about 410 miles.

So I set up a test mission with the first waypoint at 410 miles after take off so cruising I would expect the fuel to run out somewhere around that point but is doesn't. It keeps going another 50-100 miles.

So I made sure in the cfg file that the capacity is 88 gallons.

[fuel]
Center1=-15.90,0.00,-1.00,88.00,0.00 (last 2 entries are useable and unusable fuel)
fuel_type= 1.000
number_of_tank_selectors= 1

..... and even doubled the fuel flow figure. "fuel_flow_scalar=2.0"

But these don't seem to have any effect, am I missing something or should I be looking in the air file, anyone any ideas please?

Thanks,

Clive :)

edit... I set the flow rate to 5 and the fuel ran out where I thought it should, need to do some more testing.
The ai seem unaffected, do they ever run out of fuel?
 
First thing I'd check Clive is the units used - gallons US or imperial? Fuel_flow_scalar does adjust the rate at which an engine burns fuel for a given power output, according to the sdk, and the DB60x was a notoriously thirsty brute, but it sounds like the AI also need their configs altered to suit.

I haven't spotted anything relevant in the .air file as yet
 
Thanks Tom, you may be right about the US gallons. The 109 capacity was set at 105 which if that was US units would equate to 90 Imperial.

Regarding the ai I've even tried setting the fuel load to zero and the blighters still keep flying!
I seem to remember from something Ted or Nigel said that the ai fm is simplified.
 
Some things to consider are that the range of a combat aircraft (if calculated properly) includes the take off and the very fuel consuming climb to cruising altitude, as well as a reasonable reserve for a safe landing. Often it also includes five or ten minutes of combat because that's what the aircraft was made to do in the first place. CFS3 doesn't model the climb as it magically teleports you to the cruising altitude and cruising speed with zero fuel consumption as soon as you hit the autopilot. When flying "manually" the results are a lot closer to reality.

I tried it myself, with a Bf 109E from MAW to make sure it's a 4.00 flight model and flew the test at 20.000 feet, 0.96 ata and 2200 rpm. The fuel consumption was 5% in six minutes and I was doing 280 mph so 100% would take 120 minutes and the distance covered would be 560 miles. It has to be remembered that it's a full blown ferry range though and doesn't even include taking off. I'll conduct a more realistic test, take off from Berlin, climb to 20.000 feet and keep flying at a direction of 270 degrees, with five minutes of full throttle aerobatics somewhere during the route. I should run out of fuel somewhere across the Channel, it's around 430 miles from Berlin.

EDIT - Test done. Now that was a boring flight if any! I took off from Tegel, climbed to 20.000 feet and set course with 80% throttle which translated to around 0.92 ata and 2200 rpm. Slightly before halfway down the route I firewalled the throttle and engaged emergency power for five minutes of general badly executed aerobatics after which I continued the flight. When I crossed the Dutch coast I had just a hair over 10% of fuel left which would mean a reserve of 10 to 12 minutes depending on the throttle usage and had travelled around 380 miles at that point. The engine coughed and died slightly past halfway over the Channel with the English coast being a distant haze at the horizon, something like 440 miles done.
 
Well that's a much better test than I did and your results are probably about right then, thankyou! I've just realised that the fm I was testing wasn't AvH but an old Aeroplane heaven one :blind:.

The ai issue is a real pain though, what were M$ thinking of! In Rowans BoB the ai will turn and head for home when their fuel gets low, I wish we had that sims ai pilots.
 
Very interesting, thanks to you guys for discussing this. Just curious, though, what's "ata" and in 0.92 ata or 0.96 ata?

Thanks,

Tom
 
It's one of the names for the boost pressure unit in the metric system, probably correctly written ATA but standing for ATmosphere Absolute, the same thing as 1 bar. On the other hand 1 bar equals around 30 in/hg or 14.5 PSI.
 
Ah, thank you! Must be another reason I'm a "Human Drone." I didn't even know you could set boost! Or is it done (like my Pontiac) automatically as well (in real life, that is)?
 
Generally in WWII era fighter aircraft the throttle lever actually controls boost pressure, more throttle means more boost. Originally the pilot was required to keep an eye on the boost gauge to avoid overboosting the engine at lower altitudes but development led to automatic boost control systems with which full throttle could be safely used and the control system let extra boost out of the system below the full throttle height, not much unlike wastegates in turbo engines.

Power settings are (usually) reported as a combination of boost and rpm as "75% power" can differ wildly depending on if it's at sea level or at 30.000 feet but 1.00 ATA and 2500 rpm is 1.00 ATA and 2500 rpm regardless of the altitude or the throttle position, naturally taking into account that such boost may not be available at higher altitudes but as long as it is it's the most valid way to tell the power setting.
 
Interesting. I'm at work so I can't jump into the "cockpit". I'm curious as to how you know you are at a given ATA.

Thanks,

Tom
 
Every aircraft has a boost gauge. On German aircraft it's the one that reads up to roughly 1.8 and the unit used is ATA, on British aircraft it reads up to 20 and the unit used is lbs/sq in, and on American aircraft it's the one that reads up to 75 and the unit is hg/in. To use a certain boost just fiddle with the throttle until the gauge reads what you want it to, there's no other magic trick or at least I don't know it if there is.
 
You must log in or register to reply here.
Back
Top