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How efficiently can you fly?

N941WR

Legacy Member
I was looking over some pictures from a trip I took this past summer and found this:
2012-09-01_12-18-35_662.jpg


That works out like this:
141 Nautical miles per hour / 162 Statute miles per hour

At 3.1 GPH...
45.5 Nautical miles per gallon / 52.3 Statute per gallon

Leaving an hour’s reserve, this works out to a range of:
10.6 hours of flight time that will allow me to fly...
1496 Nautical miles / 1720 Statute miles
 
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Interesting how did you get 3 gallons, when mine reads 3.x gallons at 1800 rpm running up on ground ?
 
Furthermore I fly at your settings frequently- 2350 rpm 19 mp around 6-7k and see 6 ish gallons sometimes dip in the fives. I don't have a lop indicator though.

I don't have EI like you I wonder If it's that much better. Wow.
 
Super efficient method

Once in a while I pull the red knob all the way out and fly burning 0.0 GPH for several minutes. Who can beat that? :D
 
Interesting how did you get 3 gallons, when mine reads 3.x gallons at 1800 rpm running up on ground ?
It could be the fuel flow you are using and how you have the range set up in the SkiView. I don't recall exactly how mine is configured.
With the aircraft moving, you can get higher RPM's at the same power setting then when sitting on the ground and the prop is struggling to move through the air.

Furthermore I fly at your settings frequently- 2350 rpm 19 mp around 6-7k and see 6 ish gallons sometimes dip in the fives. I don't have a lop indicator though.

I don't have EI like you I wonder If it's that much better. Wow.
Yes, dual electronic ignition is that much better!
 
Thats incredible. Thats TWICE what a Mooney 201 can do, and thats the most efficient certified plane in its class. Amazing.
 
Those CHT's seem really high for how far back on the power you are. Pretty stellar MPG though!
 
Nearly as good

Bill we just got back from a 259 NM trip through Australia's outback. On our last fuel top-up to get home we were quoted a $100 call out fee. I told him what he could do with his avgas as we believed we had enough to get home (with reserve). I have never tried LOP as I want to get the CHT's more even with some playing around with the baffles, so once at altitude I just pulled the throttle back to 100-105 kts IAS (110-115 kts TAS) and was cruising along at 15 LPH (3,9 GPH) (60% ROP)

Bob
0-235 RV9a
(P-Mags and Rotec TBI)
 
Those CHT's seem really high for how far back on the power you are. Pretty stellar MPG though!

Two things are going on here. One, I was still working on the baffles. My CHTs are much better and I continue to tweak the baffles to get the CHTs even lower.

Two, I have found that with the little bit of air going through the engine at slow speeeds, the CHT's are high. Back when I had the O-290 up front I did a 100 mile flight with some friends in much slower planes and had to fly at around 100 to 120 mph and found that while the -9 can fly at those speeds w/o any kind of issue, the CHT's were close to 400. Speeding up, buring more fuel, put more air over the CHTs and brought them down into the 364*F range.

Third, I'm running LoP on a carb'ed O-360 and have worked hard to get the CHT's equal. I'm getting very close but now my front two cylinders will run below 300*F and the back two up around 340. RoP power brings them all in line. So, with the carb it is a trade off. If I could talk Don R. into giving me (Not going to happen) an injection setup, I'm sure I could get all my CHTs ballanced.

Running LoP with the carb works out well and the engine just runs as smooth as could be. I credit the dual electronic ignition. (I don't think it really matters who's EI you use, but they really do help!)
 
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Look at it this way, our planes share the same MPG per seat numbers.

Except our back seats are empty 90% of the time, and the fuel flow meter doesn't know that! LOL. Awesome airplane you got there. Post more details about your engine and airplane mods
Byron
 
OOPS!!

Bill we just got back from a 259 NM trip through Australia's outback. On our last fuel top-up to get home we were quoted a $100 call out fee. I told him what he could do with his avgas as we believed we had enough to get home (with reserve). I have never tried LOP as I want to get the CHT's more even with some playing around with the baffles, so once at altitude I just pulled the throttle back to 100-105 kts IAS (110-115 kts TAS) and was cruising along at 15 LPH (3,9 GPH) (60% ROP)

Bob
0-235 RV9a
(P-Mags and Rotec TBI)

That was a 2590 NM trip (missed the little round circle on the end :D )
 
For cruise, we normally fly 55% power. At 1000', that is 21'/2100 RPM.
That gives us close to 22 litres/hr (5.8 US GLS) in FF and about 130 KIAS.
We have a IO-360 with dual P-mags (love them!) and operate at 50* LOP.

We normally don't cruise that low, but I still use 55% power up higher: I keep the 2100 RPM and reduce the MAP alittle to get 55%.
The IAS goes down a few knots at altitude, but the TAS increases, so there's a gain anyway.

With alittle tailwinds, that gives us pretty amazing results:

http://www.vansairforce.com/community/showthread.php?t=67560&highlight=toyota
 
Alf, like you, my typical cruise power setting is 55% LoP and I see similar numbers (just a bit higher because of carb, but close) at that power settings. What great airplanes!
 
... Awesome airplane you got there. Post more details about your engine and airplane mods
Byron

Bryon, there is not much to post. It is pretty much a stock RV-9 Tail dragger. I do have the Sam James short cowl and an O-360 but nothing special other than that. The engine is an ECi O-360 kit that I put together with the help of an IA friend. The ignition is a dual P-mag electronic ignition, which helps a LOT with running LoP. (BTW, for those who are wondering, I'm running the "A" curve.) The carburetor is as stock as they come

The build is detailed here and the O-360 and cowl installating is detailed here.

The RV-9 only holds 36 gallons, which isn?t really an issue, if you stick with a small engine. Van?s recommends an O-320 which is really plenty of power for this plane. The O-360 can gulp 16 GPH at takeoff settings and the electric fuel pump on. Needless to say, I don?t run it that way for very long.

75% cruise speeds just touch 170 knots / 200 MPH TAS but you are pumping fuel through it at those speeds at the rate of 10.5 GPH. Call it the same as your 201.

Yes, the RV?s are that good and there is more room than the Money. (Don?t get me wrong, I?m a huge Mooney fan!)

Alf, like you, my typical cruise power setting is 55% LoP and I see similar numbers (just a bit higher because of carb, but close) at that power settings. What great airplanes!
 
Bill, not to pile on, but 3.1 gph, 19.2 MAP and 2330 rpm are not possible on an O360. Well lean of peak at those settings might be in the mid 5 gph's. Seems like gph indication somehow amiss? You have definitely piqued our curiosity...
 
Bill, not to pile on, but 3.1 gph, 19.2 MAP and 2330 rpm are not possible on an O360. Well lean of peak at those settings might be in the mid 5 gph's. Seems like gph indication somehow amiss? You have definitely piqued our curiosity...

I agree.

My fuel flow/HP spread sheet indicates 36.5 HP at 3.1 gph (or 20.26% with a 180HP engine) This is with a BSFC of .51 which is high, I know, but even if one figures .43 (serious LOP) I don't think the RV will cruise at 24.03% power.

Perhaps the fuel flow indication needs calibrating.
 
Bill, not to pile on, but 3.1 gph, 19.2 MAP and 2330 rpm are not possible on an O360. Well lean of peak at those settings might be in the mid 5 gph's. Seems like gph indication somehow amiss? You have definitely piqued our curiosity...

You could well be right; however, I'm never off by more than a few gallons each time I top off.

Maybe I should get a witness and fly a test at those settings.
 
You could well be right; however, I'm never off by more than a few gallons each time I top off.

Maybe I should get a witness and fly a test at those settings.

it should be more like a few 0.1's of a gallon, not a few gallons-
 
You could well be right; however, I'm never off by more than a few gallons each time I top off.

Maybe I should get a witness and fly a test at those settings.
Hmmm, I have refrained from commenting since others have noticed the same things as have I and have made their comments. However, when you make this statement:
I'm never off by more than a few gallons. . .
Well. . . this is very telling. Unless this is a typo, this should be a huge red flag that there is something amiss. If your instrumentation is accurate you should NOT be off by a FEW GALLONS. As the previous poster stated, your calculations and those of the instrument should be very very close. A few gallons is not any where near close in the analysis of whether your readout is accurate or not.
 
That really does seen too good to be true (accurate??). I thought my 6A with dual electronic ignition and electronic fuel injection was doing great at 130kts TAS at 6.2gph 50 degrees LOP at 4500' with a 320... Im currenyly switching to a 360 with the same set up...If I half my burn and add 10kts...the swap will pay for itself in no time!!! FYI my fuel calculations were ALWAYS within .02-.03 gal. at fil up. For comparison what are you showing at idle or take off? How does that fuel flow compare to other carb 360s with a more calibrated fuel flow sensor?
 
The problem might be the carb. The fuel pump supplies way more fuel than the motor can use. So as the float closes off the seat, the fuel flow will decrease.

It should be accurate for overall fuel used. But so is the stick I check my tank with.... Within 3/10ths per fill up.

Fuel flow gauges look like a lot of fun, and give you something else to look at during a long flight. Unless it can give you an average over an hour flight, I wouldn't place much value on FF numbers with a carb.

I would not plan a cross country based on the FF in your picture.

But, as all of you know....... I have been wrong in the past.................:D
 
Bill forgot this photo was taken before he adjusted his Skyview (it was a brand new install.. this IIRC was first trip after installation).

You guys should ask to see the photo when he was on his way back from Ocracoke ;) (this one was taken on the way there..)... or any other more recent photos post-adjustment of fuel flow.
 
Once in a while I pull the red knob all the way out and fly burning 0.0 GPH for several minutes. Who can beat that? :D

I think Scott Card mentioned he and Tanya catch thermals in their 9A. If they're pulling the red knob (and I don't know if they are) they have you beat (and me too). They would be going up, not down, on 0.0 gph!

I will say, watching you do real dead stick landings last spring was impressive.

You can be sure I'll be trying to soar my 9A soon. Scott's post inspired me.
 
The problem might be the carb. The fuel pump supplies way more fuel than the motor can use. So as the float closes off the seat, the fuel flow will decrease.

It should be accurate for overall fuel used. But so is the stick I check my tank with.... Within 3/10ths per fill up.

Fuel flow gauges look like a lot of fun, and give you something else to look at during a long flight. Unless it can give you an average over an hour flight, I wouldn't place much value on FF numbers with a carb.

I would not plan a cross country based on the FF in your picture.

But, as all of you know....... I have been wrong in the past.................:D

It does not work that way....many thousands of us out here flying with carbs and fuel flow transducers that work quite well. If the system is properly calibrated and the engine is running, you will get an accurate and reliable instantaneous reading and at fillup you should be really close if you are properly calibrated.

When the engine is running, the float/needle never fully close off. They stay cracked open to keep the fuel in the bowl at a constant level. The more power you demand, the wider the crack. Flow is flow no matter how big a volume the source can provide.
 
Bill, You sure have me beat. I don't think I've topped 32 mpg yet and typically I'm getting more like 25. Wind seems to have a lot to do with "mileage" and pay more attention to fuel burn and IAS when I look at economy. If I ever add a OAT probe to my D100 I think I'd look at TAS vs fuel burn.

On the other hand, I'm just now approaching 50 hours in the plane and I'm still learning but I have never seen anything approaching 4 GPH, yet.
 
Our FF meter uses the tried and true Floscan transducer. The fuel used is accurate to 2-3% which ends up being .1 to .2 gallons in 40. if the fuel used is dead on, so is the FF.
 
Bill forgot this photo was taken before he adjusted his Skyview (it was a brand new install.. this IIRC was first trip after installation).

You guys should ask to see the photo when he was on his way back from Ocracoke ;) (this one was taken on the way there..)... or any other more recent photos post-adjustment of fuel flow.

Radomir, you are incorrect. This photo was taken after I adjusted my fuel flow and it still reports a little high, which is how I like it.

I have not touched the thing since before this flight. Those numbers are pretty close to true.

As for the rest of you, there are two things about my plane that most of you don't understand. While a good number of you are poo-poo'ing the -9 because it is not acrobatic or not as strong as the clip wing RV's, one thing it does have going for it is the Roncz airfoil matched to a longer wing which is optimized for high altitude "efficient" cruising. Thus, an RV-7 with the same engine putting out the same power and at same weight should be slower than the -9. Flip this around and the -9 should be able to fly at the same speed as a -7 (or -4, -6, & -8) while burning less fuel. It is just one of those tradeoffs you selected when you ordered your kit.

The second thing I did was my prop selection. Since my plane is not acrobatic and I felt like 1400 to 2200 FPM (Gross to solo) climb rates were good enough for me, I asked Craig Catto to carve me an Uber Cruiser prop.

In fact, it is so efficient that I went all in at 2500 AGL, side-by-side, with a friend who's CS prop equipped RV-7's engine dyno'ed at well over 220 HP. At 169 kts indicated (I have no idea what TAS was) he asked me to pull back because I was pulling away from him.

So, while you can call BS on the photo, it is what it is.

The truth of it is, not very many of us fly at these lower speeds. I only did it on this trip because there wasn't fuel available at our destination and I wanted to make it there and back w/o stopping for fuel. Sometimes flying slower is actually flying faster because you don't have to stop to fill up.
 
?....... Thus, an RV-7 with the same engine putting out the same power and at same weight should be slower than the -9.......

Mine hasn't been dyno'd, but figure it puts out 190hp. So Aurora and I will do a wingtip to wingtip comparison with you. ;):D
I haven't spent much time at 2500', but here's 4000'
photobucket-36965-1359951007272_zps9bc8adae.jpg


And my normal cruise numbers up higher.
brianphonesep12094.jpg
 
Radomir, you are incorrect. This photo was taken after I adjusted my fuel flow and it still reports a little high, which is how I like it.

I have not touched the thing since before this flight. Those numbers are pretty close to true.

As for the rest of you, there are two things about my plane that most of you don't understand. While a good number of you are poo-poo'ing the -9 because it is not acrobatic or not as strong as the clip wing RV's, one thing it does have going for it is the Roncz airfoil matched to a longer wing which is optimized for high altitude "efficient" cruising. Thus, an RV-7 with the same engine putting out the same power and at same weight should be slower than the -9. Flip this around and the -9 should be able to fly at the same speed as a -7 (or -4, -6, & -8) while burning less fuel. It is just one of those tradeoffs you selected when you ordered your kit.

The second thing I did was my prop selection. Since my plane is not acrobatic and I felt like 1400 to 2200 FPM (Gross to solo) climb rates were good enough for me, I asked Craig Catto to carve me an Uber Cruiser prop.

In fact, it is so efficient that I went all in at 2500 AGL, side-by-side, with a friend who's CS prop equipped RV-7's engine dyno'ed at well over 220 HP. At 169 kts indicated (I have no idea what TAS was) he asked me to pull back because I was pulling away from him.

So, while you can call BS on the photo, it is what it is.

The truth of it is, not very many of us fly at these lower speeds. I only did it on this trip because there wasn't fuel available at our destination and I wanted to make it there and back w/o stopping for fuel. Sometimes flying slower is actually flying faster because you don't have to stop to fill up.

Sorry Bill,
You may have a very fast airplane, and I of course don't disagree with you regarding your comparison of the long and short wing,
but if your other instrumentation is correct (MP and RPM), there is no way (without changing the laws of physics... where is Scotty when you need him) that you can burn anywhere near 3.1 GPH at 19.2 inches and 2330 RPM.

Puttering around my local area I fly at lower power settings than your photo, and I don't get F.F. anywhere near that low (and yes I know how to lean).
 
Fuel Flow

Fuel flow * 14.9 / Rated HP = % power when operating LOP
Your flow = 3.1 * 14.9 / 180 = 25% power (46 HP) I think most EIS use ROP tables based on RPM and MP.
Also, look at the indicated OAT...71F at 7500'. I wonder if thats correct, have you calibrated it? If reading high, your TAS is reading high also. If the sendor is in the slip stream that may be one reason for any error, try going from slow flight to fast cruise at the same altitude, see if it changes.
FWIW
Tim
 
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You could well be right; however, I'm never off by more than a few gallons each time I top off.

Maybe I should get a witness and fly a test at those settings.

Folks re-read this post - this is the indicator. If you are off by a few gallons in 36, you could easily be showing these numbers too. Lose "a few" and you, too, will be showing incredible economy. If the fuel flow was accurate, the math should be within a few tenths on fill up. Figure most fill ups are not from dry tanks, this could easily be a 20% difference.
 
...Also, look at the indicated OAT...71F at 7500'. I wonder if thats correct, have you calibrated it? If reading high, your TAS is reading high also. If the sendor is in the slip stream that may be one reason for any error, try going from slow flight to fast cruise at the same altitude, see if it changes.
FWIW
Tim
Welcome to August in the south.

Using the standard lapse rate of 3.5*F/2*C for every thousand feet:
7500-250 (Ground elevation)/1000*3.5+71=96.4*F

Look at the GPS ground speed, 143 kts, with 6 kts winds, five of which is a cross wind. TAS is 141, I would make the one knot difference a rounding error.

My OAT is accurate.
 
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Folks re-read this post - this is the indicator. If you are off by a few gallons in 36, you could easily be showing these numbers too. Lose "a few" and you, too, will be showing incredible economy. If the fuel flow was accurate, the math should be within a few tenths on fill up. Figure most fill ups are not from dry tanks, this could easily be a 20% difference.

Yes, but I'm always putting in less fuel than the SkyView is telling me. Meaning, I land with more fuel than the computer thinks I have. Not the other way around. Out of 25 gallons, I might be off one gallon.

Keep it coming...

One question, have any of the rest of you tried flying this slow LoP? What numbers are you seeing?
 
My Results

I fly LOP fast and slow most of the time.

Her is the best I can do - RV-9A, carb, dual EI, Hartzell

6.1GPH * 6lbs/gal
------------------- = 0.41 BSFC
160HP * 56%

154KTAS/6.1GPH = 25.25 NMPG or 29 SMPG

Flying at 130KTAS I burn 5.0GPH = 26 NMPG or 29.9 SMPG

I am within .2 Gals on each fill up and slightly less effcient than the Van's - 9A was at the CAFE foundation. My plane has Std cowl and is not all that clean (but I still love her!)

Meet%20Liv_066.JPG
 
Yes, but I'm always putting in less fuel than the SkyView is telling me. Meaning, I land with more fuel than the computer thinks I have. Not the other way around. Out of 25 gallons, I might be off one gallon.

Keep it coming...

One question, have any of the rest of you tried flying this slow LoP? What numbers are you seeing?
Bill,
those of us who are questioning your 3.1 gph are not disputing the efficiency of the 9/9A airplane. Actually we are not even questioning your integrity. What I am saying, and I believe others are saying as well, is that the readings on your instrumentation do not hold up to the scrutiny of scientific factual reality.

I have a 9A running an ECI 180 HP IO-340 with Catto 3-blade 68X72 prop, Lightspeed plasma III and Slick Mag ignition, forward facing cold air induction, ECI fuel injection with return fuel lines, Vetterman 4-straight pipes, standard Van's Cowl with snorkel (no snout). I religiously fly LOP at every altitude whenever possible. I run LOP slow and fast, high and low. My comparable speeds (in MPH), FF (GPH), etc. at 6,500ft can be seen in this picture:

LOP%2520%2540%252031F.jpg

When this pic was taken I was running fairly close to what you are showing in your pic in terms of altitude and airspeed. Notice my MAP, RPM, OAT, and most specifically, Fuel Flow (7.5 gph in the box just above the MAP gauge on the bottom right of the EFIS). Flying at the speeds and altitude you reported this is a standard operating range I will see with my fuel injected 180 hp engine.
 
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