posted 02-27- 12:57 PM               

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Looking in the OpenPlane guide, EngSFC is defined as: "Specifies specific fuel consumption in units of pounds per brake horsepower generated per hour."

However, to me that would mean if a single engine plane flew for an hour at 100 HP, and its SFC is 150 (which seems pretty standard), then it would consume 15000 pounds of fuel. Obviously this can't be the case, because that's way too much fuel! So, am I smoking crack, or is the definition of engSFC wrong?

charm

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posted 03-26- 05:38 PM               

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The I-16 has an SFC of 315 g/HP/h. I´m an math idiot, but that would be 0.6945 lb/HP/h. If I compare this with the engSFC´s for the other planes that can´t be right.

I also wonder what units are used in the mission editor. In my handbook (german) they say I should use "Pfund" (1 Pfund = 500g). I used pounds instead and the tank is allways half full/empty when I start a mission.

?

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posted 03-26- 08:33 PM               

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Laika--

The Mission Editor uses pounds for planes...so we have discussed this in anpther thread and figured that 1 US gallon weighs 6 pounds and 1 Imperial gallon weighs in at 7.2 lbs.

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posted 03-27- 02:58 AM               

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What about the engSFC ? and why is tank allways half full ?

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posted 03-27- 08:24 AM               

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Make sure the fuel guage is pointed at the right plane and fuel tank.

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posted 03-27- 10:41 AM               

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The DOF for the guage is set up wrong, but thats not the main problem. I need to know wich engSCF I should set up 315 is to much I think but 0.6975 is not enought !

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posted 03-27- 02:41 PM               

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Does anybody know this EngSFC stuff? I really don't understand what I don't understand here. I thought that SFC = 150 is way too big for the reasons I posted originally. Laika has 315g/HP/h for his plane. I assume he means g = grams, not g = gallons. So, that is .315kg/HP/h = .69lb/HP/h, which sounds about like what the numbers should be. After all, if the plane is flying at 200 HP, that would be 140 lb of fuel an hour, which is like 23 gallons an hour, right? That seems reasonable... however, it would mean that the engSFC values for existing planes are way too high.

What's the answer here?

charm

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posted 03-27- 02:55 PM               

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I've not run out of fuel yet.

The best way to test would be to set up a flight using the documented altitude and speed, but use a scaled range (say 30 miles straight). Make sure the plane has the same loadout as the documentation states. Then you scale the fuel load using the same number to scale the distance on the planes max fuel load. If the fuel is exhausted a few dozen feet BEFORE the end of the run, then the engSFC is fairly close to real world.

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posted 03-27- 07:12 PM               

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Yes whirlwind, we could do a test which wouldn't be the most difficult to see how the engSFC works, but who wants to spend an hour setting up a test scenario and figuring the length of time a certain HP plane with a certain SFC takes to run out of fuel? It sometimes annoys me that certain people who are more intimate with the game than us probably know why there is this apparent discrepancy between the shipped planes and the documentation (I think), but they still don't write the 2 sentences which would end the debate immediately: i.e. definition is correct in OpenPlane spec, the shipped planes have high SFC so that they can run out of fuel in the small arena. sigh... I guess everybody has their own priorities.
charm

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posted 03-27- 07:27 PM               

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Correct in what sense? Is 150 engSFC right for all the planes in the game, probably not unless they all used the same engine. The 109 G-6 had a meer 378 mile range. 150 might be right for one of the planes, but not all. Is the engSFC simulated rate accurate? I haven't a clue, and I don't think the communty has tested it yet.

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posted 03-28- 04:01 AM               

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Right charmstar !!! MH could answer this in 10 seconds, maybe he didn´t noticed that topic. You think 0.69 could be right ? I know this: the range of the I-16 is 248 miles at 185 mph (main tank).

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posted 03-28- 12:26 PM               

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Laika-
I really don't know what is right or what isn't. I think that the .69 calculation is correct if we define engSFC as it says it is in the documentation, but is that really how it is? If so, then why do other planes have like 150 for their engSFC? Also, speed doesn't seem to be mentioned at all, but that can't be right... everybody knows the faster you go, the more fuel you burn. I'm inclined to think I have just misread the definition, but it doesn't seem like anybody knows.

charm

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posted 03-28- 12:50 PM            

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charmstar, the speed difference is taken into account with the HP inclusion in the equation.

SFC = gallons/HP/h

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posted 03-28- 03:12 PM               

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Oh, I see... I had assumed that if an engine is 200 HP, then it always runs at 200 HP. I guess this isn't the case? So, if you are at 80% throttle in a 200 HP engine, does that mean 160HP? I had thought that just RPM would be different, but I really am clueless (you can tell I don't know much about engines).

charm

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posted 03-28- 03:25 PM            

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Raising the throttle up on the engine is going to increase the work it does in a unit of time, which is the definition of power.

I dont think the 80% = 160HP would hold because that would imply no power at zero throttle (idle), but the engine is still turning. Theres got to be a minimum HP for the engine running at idle, what it is, i dont know.

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posted 03-28- 04:35 PM               

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Basically, SFC is essentially defined as the amount of fuel consumed at max throttle per hour. The definition in the OpenPlane doc may be incorrect.

I'm fairly sure the FS planes were correctly set.

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posted 03-28- 07:06 PM               

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So MH, is it the amount of fuel in lbs or in gallons (per hour)? This is beginning to make a lot more sense now..

thanks,
charm

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posted 04-01- 06:13 AM               

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I´m not much wiser yet ! Could that be:

315 gramms =0.69 lb, 0.69 lb * max HP = 690, 690/6 =115 gal per hour ? I´m still not sure, cause the I16 got an bigger engine volume than the spitfire so it should need more fuel !?!

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posted 04-02- 12:45 PM               

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Laika-
I _think_ that is right. Also, 115 is right in line with the shipping planes.

charmstar

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