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  #1  
Old 04-04-2020, 10:57 AM
Lizard Lips Lizard Lips is offline
 
Join Date: May 2012
Location: Longview, Texas
Posts: 74
Talking 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. 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
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  #2  
Old 04-04-2020, 11:09 AM
OKAV8r OKAV8r is offline
 
Join Date: Feb 2007
Location: Edmond, OK
Posts: 83
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Quote:
Originally Posted by Lizard Lips View Post
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
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  #3  
Old 04-04-2020, 11:22 AM
Jpm757 Jpm757 is offline
 
Join Date: May 2013
Location: Sherman, CT
Posts: 719
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Quote:
Originally Posted by OKAV8r View Post
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.
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Last edited by Jpm757 : 04-04-2020 at 03:26 PM. Reason: Edit
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  #4  
Old 04-04-2020, 02:22 PM
Lizard Lips Lizard Lips is offline
 
Join Date: May 2012
Location: Longview, Texas
Posts: 74
Default FUEL FLOW QUESTION

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

Stay safe,

Joe
Longview, Texas
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  #5  
Old 04-05-2020, 09:20 AM
wilddog wilddog is offline
 
Join Date: Feb 2008
Location: va.
Posts: 455
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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.
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  #6  
Old 04-05-2020, 09:46 AM
Nova RV Nova RV is online now
 
Join Date: Aug 2015
Location: Leesburg, VA
Posts: 444
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This is from the Lycoming manual for the IO390. Max fuel flow 105lbs per hr at 210HP. That's roughly 17.5GPH
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Leesburg, VA

CFI-I ASMEL, ATP, B-1900, A319/320, B-757/767, B-737, Flight Engineer-Turbojet

RV-14A kit # 140243 (flying as of 11/18)
VAF 2018 and 2019 paid
www.mykitlog.com/chrismoon/
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  #7  
Old 04-05-2020, 05:15 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
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Location: Brisbane Qld. Aust.
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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.
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  #8  
Old 04-05-2020, 06:40 PM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
Posts: 292
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Quote:
Originally Posted by RV10inOz View Post
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
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  #9  
Old 04-06-2020, 02:40 AM
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RV10inOz RV10inOz is offline
 
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Location: Brisbane Qld. Aust.
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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.
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  #10  
Old 04-06-2020, 05:55 AM
Nova RV Nova RV is online now
 
Join Date: Aug 2015
Location: Leesburg, VA
Posts: 444
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Quote:
Originally Posted by RV10inOz View Post
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
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Leesburg, VA

CFI-I ASMEL, ATP, B-1900, A319/320, B-757/767, B-737, Flight Engineer-Turbojet

RV-14A kit # 140243 (flying as of 11/18)
VAF 2018 and 2019 paid
www.mykitlog.com/chrismoon/
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