strategies for maintaining less than full tanks

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catmando
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strategies for maintaining less than full tanks

Post by catmando » Mon Jun 10, 2019 3:45 pm

Hi all, first post here.

I own a share (with 3 others) in a DA40 (with extended range tanks) and DA42.

I am wondering if there are any decent strategies for keeping tanks say 10 gallons less than full (i.e. 60-70 lbs of payload)

Very little of our missions take the plane more than 2 hours away, so having the extra payload would be helpful.

I flew pipers for years, and was used to the "fill it to the tabs" routine.
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Re: strategies for maintaining less than full tanks

Post by BRS » Mon Jun 10, 2019 4:37 pm

I suspect that it would be possible to pull the tanks and reinstall as 40 Gal system. The 50 gal system is 3 tanks per wing and the fuel filler location for the 40 Gal tanks is clearly marked.

Image

It would take some reconfiguration of the G1000 (if your plane is so equipped). Has anyone done this?
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Re: strategies for maintaining less than full tanks

Post by Rich » Mon Jun 10, 2019 5:35 pm

Mitch,
I assume you're not looking to be as drastic as converting the plane's capacity to 40 gal. And I also assume you understand that merely restraining fuel load to 40 gal of the 50 gal. capacity does not relieve the 100.4 in. CG limit.

The documented method of measurement is to use the partial-tank gizmo Diamond provides. But these things are hard to use properly and they keep getting lost or broken, so that's not my recommendation.

What I do to consider how much fuel I have is simply use the gauges. For example, there are times when I have a bit of a load and it's summer (lots of 5500+ DA days around here), a short flight, and I'm going into/out of a sketchy field so I'll limit the fuel I carry. Having had my plane for 17 years, I've found that my gauges are accurate within 1 gallon, so if the 2 gauges show 9 and 6, for example, I might add 6 and 9 gal. respectively, to bring it up to 30 gal. The uncertainty is 2 gallons total, because resolution of each the gauges is 1 gallon. But this is also true of pretty much any alternative measuring device you can come up with. My example is different because it's not a question of hitting MTOW or CG limitations, it's just recognition that I don't need all that much fuel for a particular flight and leaving some behind works in my favor, despite the common aphorism to the contrary. I also have the luxury now of being the only one flying my plane, so I know when it was last filled, how many hours it has since been flown, and the nature of those flights.

I used to have a Cherokee 140 with those tabs. Rarely did I fill above them, as higher Density Altitude was a factor on almost every flight. "Filling to the tabs" also left a bit of uncertainty but it was close enough for any flight I made. But there were times when I did use the full tank capacity, when performance margins were favorable (and usually when I was alone; 5-6 hours in the air could incite mutiny among the passengers :) )

One last thing: I always have a bit of buffer in my figuring how close I am to W&B limits. I'm confident in the empty weight/CG of the plane, and fairly confident of the fuel load (especially if I have filled the tanks), but the actual weight and locations of people and cargo are estimates.
2002 DA40: MT, PF, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal.
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Re: strategies for maintaining less than full tanks

Post by catmando » Mon Jun 10, 2019 7:57 pm

thanks, that is the best I could come up with as well. With 4 guys sharing the planes, it would be a matter of checking the fuel before filling and the instructing the fuelers (we are at a pretty big airport) how to fill each side.
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Re: strategies for maintaining less than full tanks

Post by catmando » Mon Jun 10, 2019 8:05 pm

FYI I can't imagine doing it, but how would you replace the tanks? how hard would it be to do?
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Re: strategies for maintaining less than full tanks

Post by Boatguy » Mon Jun 10, 2019 11:22 pm

I have an NG, but I have also found the gauges to be very accurate, certainly within 1 gallon. I confirm it with a visual indication, but I don't think it's relevant to you since our tanks are different.
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Re: strategies for maintaining less than full tanks

Post by mdieter » Tue Jun 11, 2019 12:12 am

Mitch,
You didn't mention how your planes are equipped. We use the fuel usage on our G1000 DA40. It's very accurate. We keep the plane at 30 gallons. We replace what we used to bring it up to 30 gals after each flight and increment the fuel totalizer. The fuel gauges are pretty accurate too. A couple times a year we top it off to get rid of any accumulated error. Worked well for us.
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Re: strategies for maintaining less than full tanks

Post by catmando » Tue Jun 11, 2019 3:23 pm

Mark,

Thanks I was was wondering if that works well enough. Sounds like it does.
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