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Fuel Flow Test, Propeller

Fuel Flow Test


Now that the fuel pipes were all connected, it was time to try out the system and carry out a fuel flow rate test from both fuel tanks.

But first the CAV-110 Fuel Drains needed fitting … actually I had purchased a stainless steel version of these fittings earlier in the build.

After applying Loctite 567 on the threads since they are NPT, I gently nipped them up.


We only put 5 litres in each tank, but this was the first time fuel had been in them.

Such a small quantity is obviously not checking them properly for leaks, but so far so good!

The UK regulations urge you to carry out the flow test in a climbing attitude, but this would be challenging and risky to rig up for a RV14! Bottom line … we simply settled for three point attitude.

I had powered the aeroplane up from the EarthX battery several days earlier, so out of interest selected the G3X screen showing the flow rate to compare … it will be calibrated properly later.

We disconnected the fuel pipe from the fuel servo, and simply ran the Fuel Pump and collected the fuel over 60 seconds.

Then we decanted it into a measuring jug to record the exact volume.


The left tank flow rate worked out at 168 litres/hour, and the right at 171 litres/hour.

Amazingly the Red Cube Flow sender showed a flow rate of 171 litres/hour!

The “eagle-eyed” will notice a Red Cross on EGT4. This was the only issue I noticed on the power up after fitting all the sender wiring, and I tracked it down to a faulty EGT probe, now replaced.

I guess we were very unlucky to purchase a new faulty probe!


We carried out the tests twice per tank to check for consistent results, and then torqued up the fuel pipe back onto the fuel servo.


We also measured unusable fuel.

This needs to be done with the plane in a flying attitude, so we raised the tail up on a trestle.

Then we ran the fuel pump until until the flow faltered, and then drained out the remaining fuel.

As expected the unusable amount is very small, as seen in this picture of the measuring jug … 0.25 litres per tank.



We had removed the propeller ready for the paint shop, but we now refitted it and torqued the bolts.


These bolts need a large torque value, and luckily a friend had one suitable which we borrowed.


The bolts have to be wire locked, which proved challenging since some of the holes ended up very hard to access in the recesses.

The only way was to back off some of the bolts, thread the locking wire through the holes, and then re-torque.

All done : )


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