There’s been a fair amount of EuroGA discussion recently about efficient engines and aircraft operating cost, so I thought given my recent low cost flying I’d throw out some numbers. Also, Peter has encouraged people to start threads and I don’t do it often enough… So here’s a story about my flying in Plane #1, my Forum namesake, built in 1946 and powered by an A-65 Continental. I hadn’t flown this plane since October last year, shame on me. This situation has been developing over the last couple of years, so at the last Annual my friend the A&P IA said (as he does) “Unless you average 1 hr per month on the plane I’m not doing this next year”. His absolutely valid reasoning is that he does this on both my planes (and a couple of others) basically as a ‘community service’ to keep people and nice planes flying… so why bother if its not being flown. Also he likes to screw with me and does it with a grin, a benefit of putting himself in a position of power 
So (getting to the bottom line) I started flying the plane again on Saturday and have done three flights so far… 1.5 hrs Saturday, 1.0 hr Sunday and today after work another 0.7 hrs, for a total of 3.2 hrs. I topped off the tanks tonight and it took 13 USG or 49 Litres, so average fuel burn was 4.1 USG/hr. Since Avgas at my US base is currently $4.15/USG my cost for flying the plane is $17 USD/hour or €14/hr. If the plane was burning non-alcohol unleaded Auto Fuel (legal by STC in the plane given 6.3:1 compression ratio, but using fuel now outlawed locally by the greenies) I could be flying for the equivalent of about €9/hr.
That’s pretty economical flying, if you don’t mind going nowhere very quickly (at 82 kts). It’d be interesting to compare numbers for both ‘hour building’ (burn per hour) and ‘touring’ (burn per nautical mile at altitude, going fast)
That’s cheap flying. What’s your mpg you think?
Here’s a guy who’s taken hypermiling flying to new levels:
AdamFrisch wrote:
What’s your mpg you think?
About 21 statute mpg, or 18 NM per gallon. About the same as an RV homebuilt going twice as fast 
Silvaire the Luscombe’s are nicely efficient – my Super Cub also cruises at around 80-82 KTAS but on 90HP and just over 5 USG per hour. So 50% more HP to achieve the same cruise as your Silvaire. Although fuel consumption doesn’t seem to reflect the HP difference – the C-90-8F likes to be run top of the green, around 75%.
@RobertL18C, you can run the A-65 as low as perhaps 3.5 USG per hour, which scales more logically to the consumption of a C-90, but with the A-65 it is common to fly at higher power settings. Redline is 2300 rpm, normal cruise is 2150 rpm, and it’s smooth and reliable anywhere up to full throttle & rpm. Also, with a Stromberg (versus Marvel) carb you can’t lean very accurately at altitude and that increases fuel burn a bit. I’ve had mine to 10,000 ft.
There is no free lunch. According to the book my C175 with 6-cylindre Franklin burns at 65% 11.6 USG per hour giving 120kt. Since I am leaning on every flight and reduce rpm to 2300 (55%) in cruise instead of 24/24 fuel burn is down to 9.5 to 10 USG. Cruise is reduced from 120kt to 115kt.
A couple of months ago I calculated the MPG (direct comparison to statue miles like in cars) for a bunch of airplanes during another thread here. I just unearthed that excel sheet. The performance figures taken for this correspond to economy cruise.
The results are quite interesting. The range I see goes from 11.3 MPG ot about 18 MPG with most of the current fleet in between. Also there is not really a clear connection of “best” vs “worst” in terms of manufacturer. Those scoring best are those who use the least HP to achieve their cruise speeds. Those worst have answered the need for speed in high HP engines rather than aerodynamics.
Some of the extremes:
I got two twins in there. The PA30 and PA34. The PA30 has an astonishing 13 MPG for a twin, whereas the PA34 only gets 9 MPG.
Low power airplanes such as the Cherokee 140 and the Cessna 150 are astonishingly better than many retracables in terms of MPG with 15.2 and 15.3 mpg respectively. Similar MPG can be found with the Mooney 252, the Piper Arrow III and The M20F and the Grumman Traveller.
The Cherokee 180 by contrast has 12 MPG, as does the SR22 and Turbo Twin Commanche…
Th TB20 is mid field with 14, similar to the Ovation and the SR20, Mooney Eagle as well as the 240 hp Commanche and the Grumman Tiger.
Top of the list are the M20C with 18.1 mpg, the Grumman Cheetah with 17.5 mpg, the 201 with 17.1 mpg. The M20E and 231 are runners up with 16.1 mpg.
Rock bottom is the Mooney TLS with 10.4 followed by the Acclaim with 11.3
In terms of kots per horsepower, the range goes from 0.5 to 0.9. This is the max horsepower the engine(s) has vs the cruise speed, so not necessarily what happens in actual cruise, when speed and power ratio are different. Bang for buck, simply.
In the 0.5 to 0.65 range are in no specific order the PA30, Seneca, SR22, PA28-180, TB20, Ovation 2 and the Comanche 240.
In the 0.66 to 0.75 range are the PA28-140, Arrow, Ovation, TLS, M20E and F as well as the original AA5 Traveller.
0.75 to 0.8 find the Mooneys Eagle, Acclaim and SR20, Gruman Cheetah and Tiger.
Above 0.8 are the Mooney 201 (0.80), M20C (0.806), the 231 (0.857), 252 (0.864).
Top of the list produces 90 kts with 100 hp: The Cessna 150 with 100 hp.
All in all just a game of numbers but some results are thought provoking.
Having just completed a trip in the RV-8 (2-up and at gross weight) where the sum of point-to-point distances added up to 6500nm, I can offer the following statistics:
Cruise consumption 7USG/hour at 155 KTAS so about 22NM/USG in nil wind.
Total trip fuel including a few sightseeing diversions and formation hook ups; about 350 USG so average effective fuel consumption about 18NM/USG.
As for economy, well the fuel price varied between $3.50 and $14/USG!
Typical power settings were lean of peak at about 65% power.
My C150 costs me about 92 pounds per hour all in to operate.
My 3 axis microlight on the other hand is alot cheaper at about 42 pounds per hour.
I prefer the microlight for fun. But I’m constantly amazed what I can do in a C150. Day vfr, imc, night and I regular shoot approaches down to minima with its DME and ADF combination.
It’s about to have an 8.33 radio fitted. I’ve been quoted 3800 for a trig ty96. The microlight on the other hand was 150 quid fitted.
Mooney_Driver wrote:
Top of the list produces 90 kts with 100 hp: The Cessna 150 with 100 hp.
Are we talking only certified? If not then mine is 115kts from 80Hp, I can push 120kts (WOT at certain altitudes – but that limits my range heavily) and 14.5 litres per hour
