REFLECTOR: Fuel Consumption Performance

Wed Aug 12 09:27:05 CDT 2009

Thanks Doug.  Interesting data. 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Douglas Holub
Sent: Tuesday, August 11, 2009 11:24 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fuel Consumption Performance

Got back from vacation today-- Texas to Seattle and back. My fuel filter
clogged up at 10,500 feet between Butte and Missoula in the Rockies. Pretty
exciting. Ask me about that story some time.

Last two legs were Laramie, WY to Denver FTG, then FTG to Dallas.  Had to
divert around some thunderstorm activity, so those two legs were 765 nm on
38 gallons of fuel. 5.9 hrs on the hobbs. That's 20.1 nm/gal including two
take offs and landings. Average TAS around 140-145 kts at 9500 feet, 2400
RPMs, 50 degrees LOP. IOX-360 with electronic ignition. FG with a
retractable nose gear. Fixed pitch, 2-blade prop. Standard fuselage. Hauling
about 475 lbs of people and baggage.

Doug Holub

N2980W, 95 hrs

----- Original Message ----- 

From: Tom Tolton <mailto:tjtolton at charter.net>  

To: 'Velocity Aircraft <mailto:reflector at tvbf.org>  Owners and Builders
list' 

Sent: Thursday, August 06, 2009 8:08 AM

Subject: Re: REFLECTOR: Fuel Consumption Performance

Thank you all for the data on my fuel consumption question.  I especially
appreciate the time spent to help me better understand what is involved.  It
is a pleasure to be part of a group so interested in building and flying.  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Tuesday, August 04, 2009 12:15 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Fuel Consumption Performance

Corrected data below - I made an error on the number for Dave's plane; it
should be 15.2 nm/g at 165KTAS.  So you can delete the previous message and
look at this one.

Al

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Tuesday, August 04, 2009 7:54 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Fuel Consumption Performance

Tom;

Fuel burn is directly proportional to power produced; and speed increases by
the cube root of power; so it's very dependant on speed.  But 6.2 gph at 125
is very good.

Here's a tabulation of what people have reported.  Numbers given for fuel
consumption are hard to compare because of different conditions, and degree
of leaning, so everything below is approximate.  Comparing at TAS helps as
it eliminates some variables on air density.

Just computing in nautical miles per gallon (nm/g)

Jim - - - - - - - - - - - - 20.4    @ 143

Tom's friend  - - - - - - 20.2   @ 125

Terry  - - - - - - - - - -  16.8   @ 193

John  - - - - - - - - - - - 15.5   @ 165

Dave - - - - - - - - - - - 12.9   @ 185

My SE RG with 20B rotary does roughly as follows: speed, burn, nm/g.

120

6.2

19.4

140

7.3

19.2

160

9.0

17.8

180

11.4

15.8

In an effort to compare at the same speed, I assumed then relationship with
speed would be about the same as my plane (using least squares fit to data).
So translating to 165 KTAS, the nm/g comes out as follows:

Terry  - - - - - - - - - -  20.4   

Jim - - - - - - - - - - - - 18.8    

Tom's friend  - - - - - - 18.1   

Al - - - - - - - - - - - -- - 17.4

John  - - - - - - - - - - - 15.5   

Dave - - - - - - - - - - - 15.2  

Terry's look very good (too good?); Dave's are not leaned; and of course,
the 173 FG with 200 hp could probably not go 165 KTAS.  

It is interesting to note that, for my plane, the nm/g flattens goes pretty
flat as the speed goes below 140 KTAS, but does peak at about 130 - 135.  So
if you are looking for minimum cost per mile; somewhere about that speed may
be it; but you'd have to run the numbers for your aircraft.

Hopefully this doesn't lose its formatting when transmitted.

FWIW,

Al

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Tom Tolton
Sent: Monday, August 03, 2009 3:29 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Fuel Consumption Performance

I recently traveled to Oshkosh with a friend who owns a Velocity 173 with
fixed gear and a 200 HP fuel injected Lycoming.  He was able to reduce gas
consumption to 6.2 gallons per hour at 10500 feet and maintain a speed of
about 125 nm/hr using LOP techniques.  

I am building a XLFG -5 with constant speed propeller.  I am looking for
what one might expect in minimum gas consumption using LOP techniques at a
density altitude of 10000  feet.  I am considering the Lycoming IO540 260
and 300 HP, as well as, the 310 HP Continental 550N.  It has been suggested
that if I buy one of the more powerful 300 HP engines  I will just be able
to run with less throttle and bring the fuel consumption to a reasonable
level.

I would appreciate any comments / experience of the builders and owners with
a similar XLFG configuration.    

Tom Tolton

989-835-5828 (Home)

989-750-8567 (Cell)

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