fuel flow discrepancy

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farleymike
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Re: fuel flow discrepancy

Post by farleymike »

I generally fly my DA42 at 80% power in cruise and see 5.8 gph. I had 1.7 engines on my DA42 and currently have the new CD-135 engines and the fuel flows are the same at the same power settings and on both engines the totalizer/fuel used is always within 1 gallon, usually within .5 gallon of fuel put back in plane when topping off.

mike
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Aart
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Re: fuel flow discrepancy

Post by Aart »

Mike,

That confuses me.. See my above table. If you see 5.8 on the display, and the actual FF as per the book is 6.2 at 80% (which is known to be an accurate value) than there should be a significant difference between what the totaliser says and what would actually be in your tank after a flight. That is exactly what my (and a fellow DA42 owner's) problem is, although we read 5.9 on the display. Are you sure?

As to the K-factor. I assume this is a fixed factor. But the readings of the FF meters either under-read or overread, depending on the power setting, so I don't see how the change in this factor can correct my readings across the board of my power settings, or am I missing something.
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Sandy
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Re: fuel flow discrepancy

Post by Sandy »

Interesting, as my 1977 Piper Lance held 128 gallons of fuel (enough to fly of 8.5 hours at normal cruise), as the prior owner was an "importer" who had installed 15 gallon bladders in each wing (very handy, along with the radar altimeter that it had, for long overwater night flights). It had a fuel totalizer (made by Shadin) that was never off by more the 0.1 gallons. It used a "turbine" sensor that was installed in the fuel line.

So much for modern electronics.

Sandy
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farleymike
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Re: fuel flow discrepancy

Post by farleymike »

Hi Aart,

I have been flying my airplane since new in 2006 with the 1.7 engine until 2015 when put new CD-135 engines on the airplane as well as many other DA42's with 135 hp engines as I was a sales rep for USAero and currently with Premier Aircraft selling new and used Diamonds. All the DA42's I have flown when flying at 80% power show a fuel burn of 5.8 gph with the occasional 5.9 gph and when I refill the airplane the amount of fuel put back in the airplane is with in 1 gallon of the fuel used/totalizer number on the G1000 fuel page.

My experience with the Diamond Aircraft since 2004 is that they perform better than the book values.
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ememic99
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Re: fuel flow discrepancy

Post by ememic99 »

There's nothing wrong with Aart's recording - I have exactly the same problem and the readings shown by FF are not in line with manual, same as Aart's. The issue results with difference of 3 to 6 USG of difference between actual tanks content and figure shown by fuel totalizer, depending on hours flown between refuelings.

We discussed this in another thread viewtopic.php?f=9&t=5961

When I manually track fuel using book values (instead ones shown by FF), I get the same actual consumption as confirmed by refueling. So the only conclusion can be that FF-meter under-reads actual fuel flow.
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