FUEL FLOW QUESTION

[Lizard Lips]

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. 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
Arion Lightning LS-1 flying routinely
2020 Dues Paid

[OKAV8r]

Originally Posted by Lizard Lips

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. 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
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

[Jpm757]

Originally Posted by OKAV8r

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.

[Lizard Lips]

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

Stay safe,

Joe
Longview, Texas

[wilddog]

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.

[Nova RV]

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

[RV10inOz]

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.

[FinnFlyer]

Originally Posted by RV10inOz

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

[RV10inOz]

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.

[Nova RV]

Originally Posted by RV10inOz

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.

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