Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
The past week has been strange down here at our airpark south of Houston. We actually suffered little to no serious damage on the runway (one wood-frame hanagr was destroyed, but all the modern metal structures were fine), and power came back on Sunday night. Cable and Internet is still out (hense my lack of particiaption here - Blackberries and overloaded Cell circuits just don't hack it!), but all in all, there hasn't been much to do.

One problem up until yesterday was the lack of ability to get Avgas - most of the local "watering holes" were out of power (KLBX is back up now for Houston RV'ers looking for fuel), so I was fueling at College Station each time I went up, and then thinking carefully about my flying in between trips.

One thing I rarely do in the RV is throttle back - I like to go fast, and run at 75% most of the time. But being acutely aware that fuel was not quite as available this week got me to bring the black lever back to 55-60% for local "storm evaluation" flights. This brought fuel flows back to the 6 gph range, and for looking at the ground, the slower speeds worked better anyway.

I'm pretty sure that I'm not unique in the RV world when it comes to enjoying the speed of our machines. Especially out here in Texas and farther west, making the endless miles go by as fast as possible is usually the goal! But there are times when pulling back can really show the efficency of these mounts. At 6 gph, I can stay up for over 6 hours if I needed to - plenty of time if you're just "loafing" anyway....

Paul
 
I agree Paul, this is why I like RV's so much. I can pull the throttle back on my -3, 0-235 and burn 4 GPH and still go 140 MPH! I like to go flying late in the afternoon before sunset. I'm in no hurry to go anywhere, I just want to see the blue sky turn orange and turquoise. I like going nowhere slowly.
 
Yup

I do all my cruising at 7 to 7.5 GPH (unless I get up high), i.e at about 60%LOP

This equates to about 160kts in the 7a with the SJ cowl.

When doing my practice approaches I throttle back to 20" and 2400RPM which still give Cessna munching performance and plenty of climb authority.

In fact throttling back, setting prop and mixture can be a handful when flying the departure procedure to 3000' and not blowing stright through it.

Really neat airplanes!

Oh yes, Paul I too an really glad you suffered no loss!

Frank
 
MPG

Hi Paul
This weekend I am going to Corvallis in my 4 and I will be trying to nail down the best speed for MPG I think it will be around 140kts @ 6gph. How does this line up with the rest of the RVer's?







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Hi Dayton

Hope we can hok up when you get here.

I think you have a FP prop and a carb?...Of course this will likely limit you to ROP operation and partially closed throttle (at low power cruise) which gives extra pumping losses that the C/S guys don't have.

By comparison a C/S and FI is probably going to be around 1.5 GPH better than an engine as described above.

I seem to remember you telling me you normally cruised at 9GPH on your last trip and mine is around 7.5..Of course your 4 is going to be faster than my 7a due to less drag at any given power setting.

Have a great trip up here

Frank
 
At the reduced power, are you leaning as well?
I get the same fuel burn, 9.3 - 9.5 US gal per hour, at reduced power full rich, 2300 x 15 inches at 6000 ft 130 knots as I do leaned ( 2300x22 inches at 6000 ft 170 knots). RV8 IO360- 200 hp
 
Flying Albert said:
At the reduced power, are you leaning as well?
I get the same fuel burn, 9.3 - 9.5 US gal per hour, at reduced power full rich, 2300 x 15 inches at 6000 ft 130 knots as I do leaned ( 2300x22 inches at 6000 ft 170 knots). RV8 IO360- 200 hp
Click to expand...

YES........ I am at sea level, I lean just after start up at 1200 rpm, taxi at 7 to 900 rpm....... full rich at MAG CHECK and take off. And then I lean any time I am under 65% power. Plugs stay clean. I have never had a fouled plug....... LSI and BENDIX.
 
6 GPH operation ALL the time.

I can see my favorite topic has come up again. Since I built an RV-9A with a 160 HP O-320, carb, CS prop, 1 mag, 1 LSE electronic ignition, I was always about the balance between speed and economy. Like those of you trying to save gas by pulling the power back and leaning appropriately, you have finally realized you don't have to go fast all the time. I have always done my long cross-country flights up high 10,000-13,000 MSL wide-open, leaned, 2300 RPM, and used 5.5 to 6 GPH at 25 MPG, 160 MPH true air speed. When I am down low, I pull the throttle back, lean the mixture, run at 5.5 to 6 GPH and get 140 MPH. The photo below shows 143 knots (164 MPH) true air speed on my Dynon D-10A, with a GPS ground speed of 157 MPH fighting minor headwinds. Don't get excited about that RED light on the fuel gauge, I fixed that loose connection a long time ago. The photo was taken on July 31, 2005 heading home from PA to Chattanooga, TN.
DSCN0015.JPG


Yeah, I have made a few high-speed passes way back in Phase 1 testing to prove the 194 MPH top speed of the RV-9A at 1,000 MSL, but that took about 11 GPH to do that. Needless to say, I only did it about 2 or 3 times for short bursts watching the temperatures, and that was enough to prove the point. The Hobb's has nearly 257 hours on it since June 2005.

When the cheap AVGAS today is found for $4.45-$4.75, I am glad I learned good cruising habits early. Ah, the price of gas in 2005, when I paid $2.69 to $3.00 and cruised a lot: OSH, the Great Lakes, New England, NYC, Florida several times, Georgetown, TX to see my son for Labor Day 2005, LOE5, Denver in 2006, and just a bunch of short hops around home.

I love these machines! I flew only 189 hours in various Cessnas from 1991 to 2005 before my RV-9A took to the air.
 
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