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Minimum Fuel for Fuel Flow Testing?

P

PhatRV

Well Known Member
Patron
What is the minimum fuel in each tank for the fuel flow testing? I plan to put 5 gallons in each tank before starting the test in the nose up position. Is this the amount that I should be using? Given 10 gallons total, 5 gallons in each tank will give me approximately 1 hour of reserve, which is my personal minimum.

Let me know. Thanks
 
Min fuel test.

Assuming both tanks are built the same I would fill one tank to 10 gallons.
The other tank with 2 gallon.
Run the test on the tank with 2 gallon, until engine begins stumbling.
Take of and landing on the tank with 10 gallon.
Be sure to stay on safe altitude and in gliding distance to the runway.

Good luck
 
fuel flow testing

I used the EAA flight test manual for fuel flow tests. It gives very clear and easy to understand step-by-step instructions for this. It says to fill each tank with minimum takeoff fuel level and no need to run the motor.....only your boost pump. You sound ready to begin a cool time in your build. I highly recommend you buy the EAA flight test manual. It will walk you through all phases of flight testing including getting your AWC. Well worth the cost.
Good luck and have fun
danny
RV9
IO-360 (with new crankshaft)
 
minimum fuel

I had 9 gallons per side. An IO-360 at full power uses 17gph at full power, 150% of that =25.5gph. I wanted 25.5gph minimum fuel flow. My fuel flow worked out to be 48gph.
9 gallons was approx 1/2 hour at power before the plane became a glider.
Do yourself a big favor and get the EAA Flight Test Manual.
danny
 
Interesting comments in this thread. Is there any reason you wouldn't test fuel flow all the way until the tanks are dry? Personally, I've found the RV tank's design provides reliable fuel delivery in the nose up attitude all the way until its dry, but one should certainly verify a new build. 5 gallons down to zero in each tank seems more than adequate to me.

Its fine to set personal minimums ahead of time (like not taking off with less than xx gallons), but its nice to know the true capabilities of the equipment for those edge cases that inevitably pop up in the real world. Like landing at an airport and finding the pumps are inop.
 
I used 5 gallons and it worked just fine. I would not be taking off with that little fuel usually so figured that was enough.
 
I was instructed to mimic a "worst case scenario", destination closed out, travel to alternate and, because you're tired, distracted etc, a go around - one gallon above unuseable fuel, pitch greater than Vx.

Yes, I'm sure none of us will ever find ourselves in that situation - but it's a confidence builder . . but then there's always the unexpectedly severe headwind, etc. !

I've tested 3 aircraft using this criteria. A tank with 5 gal of head pressure is not the wisest approach IMHO.
 
I used 5 gallons per tank. My test results came out at over 6 lbs of fuel per minute which is 3x the required fuel flow for the 180HP engine.
The rationale for 10 gallons total is 1 hour minimum. From the Aviation101 YouTube channel, Josh landed to refuel with 1:30hour of reserve but the self serve fuel pump was out of order. This necessitated a short trip to another airport for fuel. This is the same scenario I was testing.

The fuel flow testing is to verify there is not unforeseen restriction in the fuel circuit for a minimum ops fuel condition rather than an absolute zero fuel. Granted, if I build this plane with my own fuel system design then I wanted to test everything to an empty tank. I may do that in the course of final assembly but it’s not required per the EAA test card. The test result was forwarded to the DAR and he is okay with it.

Thanks for all the comments
 
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