172 Fuel Consumption

[rudel.dietrich]

I started a new company in Air Hauler out of Lake Tahoe and I am doing the starting grind in the 172 to build reputation and money to afford a turbo prop. The A2A 172 makes the process a lot more enjoyable but I find that my aircraft is using far less fuel than it should. Last night I flew a 452 nm flight at 7500 feet at around 3 C (average air temp) with my planes MTOW maxed out and I only used 2.3 GPH in my flight
Shouldn't this be closer to 7-7.5 gph?

I may be trading my car in soon for a 172 to commute to work in if I can get that kind of fuel efficiency!

To add, I have fallen before to using time compression and I know that this messes with Accu Sim, so I went this entire flight at 1x time compression for the 5.5 hour flight and I read a book and played PS4 with my son and daughter and checked on the plane ever 15 min to make sure it had not flown itself into the side of a mountain.


Edit: To add some info. At max MTOW I cruise at 75% throttle and IAS was 105 knots and my ground speed was 113-115 knots.

[cessnaman]

Not sure what's going on, but How many gal. did you burn?
If you were burning 2.3gph then you used almost 13 gal. for a 5.5 hr flight which is definitely not right.
If burning say 7.5gph like you should you would burn a little more than 41.gal. Of course these numbers don't reflect the fuel burn for taxi,takeoff and climb and the winds aloft.
What was the needle showing?
Looks like you had a tail wind, which can help save some fuel.
Sorry I can't help, but also make sure you have the latest up date.

Oh, one other thing, not sure, but maybe with the a2a c172 being a complex realistic aircraft, it may have problems with the air hauler software.
I think I have air hauler, but not sure if it's for fs2004 or fsx. I'll check and see and if I do have it for fsx I'll try when I have time. Actually I think it would be cool to use air hauler with the c172 especially flying the Alaskan Frontier.

Gabe

[cessnaman]

Actually I don't have Air Hauler. I have Cargo Pilot. I'll have to try that wit the c172.

[Great Ozzie]

Last night I flew a 452 nm flight at 7500 feet at around 3 C (average air temp) with my planes MTOW maxed out and I only used 2.3 GPH in my flight
Shouldn't this be closer to 7-7.5 gph?

Edit: To add some info. At max MTOW I cruise at 75% throttle and IAS was 105 knots and my ground speed was 113-115 knots.

Something not right... depends on power setting. Like it was said... updated, right?

I just did some testing fwiw.

C172R: wheel pants / no flap-gap seals
GW (2450lbs)
Clear Wx theme
8000' msl

Approx 2200rpm (64% BHP) gave me 109KTAS using 7.3gph

[rudel.dietrich]

This was updated to the Sept 28th accu-sim update.
I use Active Sky Next for weather and weather was clear and warm on the ground and just above freezing at 7500'. Winds were very light. I think they maxed out at 3 knots at 7500'
I fly pretty hands off on long flights. I put it at 75% throttle after I made altitude and I left it there. I leaned out my mixture but it was still fairly rich. I don't constantly fluctuate it in flight. I keep it lean enough to not corrode the engine but I keep it rich enough to keep the speed high.

Air Hauler keeps track of lbs of fuel used so I had to convert it using 6.02 lbs per gallon (6.79 for jet fuel) which is what I was taught. The total used on that flight was 12.7 gallons which is insanely low for that flight distance.

[cessnaman]

I haven't flown in a couple of weeks so I haven't updated to the latest yet.
I wonder if air hauler is causing this issue.
I don't use Active Sky, I use Opus FSX for weather, but that shouldn't be the issue.
Have you tried flying a long distance without using air hauler?
If not give it a try and see what the fuel burn is. This way you'll know if it's air hauler causing this.
I don't have that program so I can't try it or see if something in that program needs adjusting.
You don't have to do a 5 hour flight, just due a 1 hour flight and see what you get.

Gabe

Edit: If the airplane is showing 7 to 8 GPH while flying with Air Hauler, then it must be that.
Just to be clear, after your flight how much fuel was actually left in the tanks?

[Oracle427]

rudel.dietrich,

Have you check the aircraft payload manager from A2A to verify the amount of fuel used in there? Perhaps Air Hauler is not tracking the usage properly vs the way A2A is tracking it.

[Great Ozzie]

rudel.dietrich,

Have you check the aircraft payload manager from A2A to verify the amount of fuel used in there? Perhaps Air Hauler is not tracking the usage properly vs the way A2A is tracking it.

Now that's a good thought.

[Lewis - A2A]

I don't believe Air Hauler or any program that tries to track the default FS programming will track this correctly. Accu-sim uses its own advanced simulation for this, details can be found under your shift + 2 panel for fuel usage etc.

thanks,
Lewis

[spork]

And make sure you aren't using time acceleration. Did a trip from Seattle to Boise once, used around 4gph.

[EnDSchultz]

Yes, Accusim seems to completely ignore in-sim time acceleration. If you do a four-hour flight but time-compress it down to one hour, you're only going to have one hour of use on your airframe and engine, which encompasses everything from wear to oil and fuel consumption.

[AKar]

Yes, Accusim seems to completely ignore in-sim time acceleration. If you do a four-hour flight but time-compress it down to one hour, you're only going to have one hour of use on your airframe and engine, which encompasses everything from wear to oil and fuel consumption.

Correct, I was once quite surprised when I paid attention that my tanks were rather full on my Columbia river following tour when I was already getting towards Grand Coulee dam...

I don't think that this is noted in the manuals... Of course, over time I've learned much about Accusim, but what I might suggest that there would be a separate Accusim manual/booklet. It could apply to all the Accusim products, and tell about what is currently simulated, perhaps what is in the works, what is not simulated on purpose - and importantly, about limitations of it. This time compression issue being one, as it takes some time to find out yourself.

I think it would make a nice brochure too to those souls still wandering in FSX darkness who've not yet stepped into the Accusim.

-Esa

[rudel.dietrich]

I was able to do some flights over the weekend and I still do not have any answers. The in cockpit 'fuel flow' gauge shows between 10-11 gph when at 100% throttle and 7 gph when at 75% cruise throttle (what is the real cruise throttle for a C172 anyways?)
Shift+2 shows me the same thing as the gauge. So the aircraft is showing the correct fuel consumption.

However, when I look at the actual fuel being used out of the wing tanks, it is not correct. It is still only using between 2.2/3.0 gph.
Also, Air Hauler does not seem to correctly be able to 'talk' to Accu-Sim in regards to payload. If I load up 560 lbs of cargo in Air Hauler, it does not reflect that in the Shift panels inside FSX.
I don't have this issue with any other aircraft, including ones that make use of complex third party payload programs like my Majestic Q-400 MJC8 Q400
Or my Quality Wings BAE 146 or 757 or even the PMDG 777 which has a payload manager so complex even I don't understand it. However, when I accept a job in Cargo Hauler and load weight onto the plane through the utility it relfects the correct weight in every plane I have tried.
Except my C172 and P-51 Mil/Civ

My next step is to uninstall all three planes and then reinstall them and the core accu-sim update and see if this corrects the fuel flow issue and the weight issue.
If not I will just shelve them for Air Hauler use. I still make plenty of flights outside of Air Hauler so it is not a life breaking issue. Just a minor annoyance.

[Oracle427]

Are you checking fuel in the tanks using the shift-4 screen?

[Great Ozzie]

The in cockpit 'fuel flow' gauge shows between 10-11 gph when at 100% throttle and 7 gph when at 75% cruise throttle (what is the real cruise throttle for a C172 anyways?)

Sounds like you are using the "S" prop based on your fuel flow at full throttle.

For RW cruise performance, one would start by going to the performance charts in the POH, determine what %BHP one would like to use (typical range is 55% BHP to 75% BHP - 65% common) and then determine the RPM setting for a particular altitude & temp.

Given std. temp & pressure... 7gph equates to roughly 50% bhp.