Fuel Flow Tests and Reports

[sglynn]

What is really needed for fuel flow tests and reports for airworthy certificate and safe flight?

I see the EAA packet for final registration and airworthiness has a form for fuel flow results but it doesn't really say it is required. And is it required that we do a flow test in a climbing, nose up attitude? I've done several tests including on bench, and two on the RV-7A and am seeing 30+ GPH using the Andair Aux boost pump. I've ensured the vent lines are open and working.

I've heard Van's did fuel flow tests and that I should request a copy of theirs. I asked, but they didn't know of such a report due to builder options.

So does everybody jack up their RVs into a climb configuration and test with the boost pump? Is that what's needed to ensure it will work?

[9GT]

Originally Posted by sglynn

So does everybody jack up their RVs into a climb configuration and test with the boost pump? Is that what's needed to ensure it will work?

Yes that is what I did before my DAR A/W inspection on my RV-10. Prior to my DAR inspection, my DAR had a list of things he would require to see were completed, and fuel flow was on it. YMMV depending on who you use. I think it is a good idea to know anyway.

[BillL]

Steve, I did three tests.

1.Pressure leak test between the fuse wall and servo. Air pressure (30 psi) for 24 hrs. Had zero drop, but if anything leaked (a 10 friend did) it dropped pretty fast as there is not a lot of volume.
2. Flow at pressure while running to determine unusable fuel. Bypassed the servo, disconnected the supply to the spider and hooked a clear section prior to a ball valve. Did each side and recorded how much fuel was still in the tank. The "not used" method.
Flow was measured by the red cube, clear section was observed to detect air bubbles in case of a suction leak. The ball valve set the system flow to max take-off flow (or near it), and recorded the pressure to ensure it was within Lycoming limits.

3. #2 was repeated with nose down and nose up. Nose up left very little fuel in the tank.

An initial 1/2 gallon of fuel was run through first and the tank drained, that purged the line and the fuel looked bad. After the purge all fuel was able to be reused.


EDIT: We tested at the over delivery required by the FAA test as well to be sure the boost pump delivered through the mechanical pump.

[pilotkms]

I did a fuel flow test with the aircraft level. It easily exceeded the requirements. I then taxied over to an incline we have on the airport that approximates the climb attitude and ran it for 3 minutes plus. It continued to work fine. I felt better for it and showed my flo results and incline position to my DAR and he was satisfied for my plane. If u want to do more, maybe a Canadian will chime in - I believe they have a very specific testing requirement.

[az_gila]

Originally Posted by pilotkms

I did a fuel flow test with the aircraft level. It easily exceeded the requirements. I then taxied over to an incline we have on the airport that approximates the climb attitude and ran it for 3 minutes plus. It continued to work fine. I felt better for it and showed my flo results and incline position to my DAR and he was satisfied for my plane. If u want to do more, maybe a Canadian will chime in - I believe they have a very specific testing requirement.

No need to go to Canada...

https://www.faa.gov/documentLibrary/.../AC_90-89B.pdf

The FAA gives the fuel flow test requirements in AC 90-89 on pages 33 and 34. This same requirement is in the FAA AC 91-116 for a second pilot in Phase I testing. It also says how you can document it.

[Ralph Inkster]

Yep, Gil's reference is the same procedure we use in Canada.

[pilotkms]

I have to give Gil credit, he always seems to have the technical or source credit with a copy or link to the many questions that are posed by us VAF?rs. Good job Gil - keep it up.

[sglynn]

Thanks all. I have one more fuel test to do. Nose Up. I'll have to find a hill on the airport and pull the tail down until the skid hits and put a ramp or blocks under the nose gear. Not going to jack the mains.

One thing the documents seem to overlook is whether the vent lines are working well enough. One test I did was a simple drain test. I let fuel drain out of the cocks and on one of them I noticed the flow slowing down to trickle. Caps are on. Something was partially blocking the vent line. I blew it out and all works fine.

[az_gila]

Originally Posted by sglynn

Thanks all. I have one more fuel test to do. Nose Up. I'll have to find a hill on the airport and pull the tail down until the skid hits and put a ramp or blocks under the nose gear. Not going to jack the mains.

One thing the documents seem to overlook is whether the vent lines are working well enough. One test I did was a simple drain test. I let fuel drain out of the cocks and on one of them I noticed the flow slowing down to trickle. Caps are on. Something was partially blocking the vent line. I blew it out and all works fine.

Nah, it's not overlooked.

If your fuel flow meets the requirements at climb angles then the vents are allowing in enough replacement air into the tank. If the vents were clogged then you would not get the proper fuel flow.

Implied is that the fuel flow test should be done in a fully operational mode testing from each tank with the fuel caps on.

[maniago]

Originally Posted by az_gila

No need to go to Canada...

https://www.faa.gov/documentLibrary/.../AC_90-89B.pdf

The FAA gives the fuel flow test requirements in AC 90-89 on pages 33 and 34. This same requirement is in the FAA AC 91-116 for a second pilot in Phase I testing. It also says how you can document it.

Awesome! Thanks Gil. My EAA chapter just did an OpsLims presentation and started me thinking on docs and DAR prep. An AC that covers a bunch of this and things I've not yet thought of yet is money! Now to order the EAA packet....