FUEL FLOW QUESTION
 

In preparing the paperwork for my Airworthiness Certificate for my RV-14A, one of the documents (not actually required by FAA but highly recommended by EAA) is a Fuel Flow Test. The form makes reference to "Engine fuel consumption at maximum take-off power".
I have searched everywhere I can think of and have not come up with a number for tlhis. :confused: My installed engine is a Lycoming IO-390 obtained through Van's.
Can anyone tell me where to look for this number?

Joe
Longview, Texas

RV-14A 95% Complete, 95% to go:D
Arion Lightning LS-1 flying routinely
2020 Dues Paid

You can calculate it. BSFC is nominally .o88 times the rated horsepower, so if it is 210HP, fuel flow at full power would be:
210 x .o88= 18.48 GPH

Yes those numbers are good, that is what I used for my calculations for my IO-360. I disconnected the fuel line at the servo and recorded the time to fill a 5 gallon container with the electric fuel pump. Then just do the math. If I recall my Andair pump was putting out about 33 gph.

FUEL FLOW QUESTION
 

Thanks, guys. That's the kind of responses and info that I needed.

Stay safe,

Joe
Longview, Texas

I did similar test but raised the fuel line so pump was pumping uphill similar to a steep climb. Still got way more GPH than needed.

This is from the Lycoming manual for the IO390. Max fuel flow 105lbs per hr at 210HP. That's roughly 17.5GPH

That is MIN fuel flow not max.

You should have around a BSFC of 0.58 and that will be 20.0 - 20.5 USG/Hr based on ISA and sea level.

This should be checked because every new Lycoming with the Avstar FI servo that I have seen has been below min spec and has been removed and sent to a workshop to correct it. Many more out there not flowing enough. :(

Could the BSFC be even higher, full power, full rich on a cold day on climb out?

Finn

The BSFC might not be higher. Lets assume you have a 0.58 on a ISA day at sea level. You take off at -10dC and with a QNH of say 1030.

Lots more mass air flow, lots more HP, and a proportional increase in fuel flow. BSFC is the same.

In a TCM engine your flow will be constant, thus lower BSFC than normal and a leaner mixture.

According to AC90-89A using the generic calculation to "approximate" the required fuel flow using .55 x HP then divide by 6 to get GPH is to be used if engine manufacturer's data is not available. Lycoming says you need a "minimum" of 17.5 GPH to make 210HP on the IO390 and the fuel flow test is to document that you can flow at least 125% or 150% (depending on pressurized or gravity feed) of that published minimum number.

The factory setup in a 14 should flow 40+ GPH so there is plenty of headroom vs what they call for in the AC

Fuel flow
 

RV-14A. Andair electric pump with wing-root mounted Andair gascolator (70 micron mesh). 1.5 gallon fuel in the the tank. Fuel line disconnected at the FM-150 fuel servo and tied up on that level.

Level flight attitude and 15 degrees nose up (mains on the floor and tail on the floor). Both attitudes: around 36 GPH.

Please put your mains on blocks and tail down to get to 20 degrees or more nose up. I would love to have those fuel flow numbers.

Will be interesting to know what is the degrees nose up at Vx (70 kts). Maybe 20 degrees, maybe more.

Andair fuel flow
 

I got around 50 GPH when I did my fuel flow test at just over 16 degrees nose up, hose disconnected just before the fuel servo. The Andair data sheet says open flow of 55-60 GPH @ 5 PSI.



http://www.andair.co.uk/product/boost-pump-px375-tc/