Last year, I bought one of those nifty Cessna 180s that is in very good condition and is completely unmolested (bone stock). I look at the illustrated parts catalog and every design detail is exactly as illustrated. I put just under a hundred hours on it, and I believe the hype. It does some things pretty well, and the other stuff very well. In its current configuration, I see just less than 100 knots at 41% power - 2000 rpm and 18 in MP at 5000ft, which is listed in the POH as a max range power setting. It says, which I have verified, that it is burning barely under 8 gph. I know that it is bad to run any machine exactly the same way all of the time, but does anyone know of any detriment to running at low power settings for extended periods? Any horror stories? With fuel costs the way that they are, I am stoked to fly around at 100 knots burning 7.9 gph. I see 130 knots at 2300 rpm with 22 in MP, burning 12.6 gph. This is a 60% increase in fuel burn for 30% more speed. That only makes sense if I'm trying to demonstrate to a Maule driver that they have an inferior craft

That's it! One more negative comment about the Fabulous Maule and I'm gonna launch this pup!!!

I can give you one story as an example of why you shouldn't do that, and then one additional reason.

In 1979, my pard and I bought one of the first TR182s off the line. Frankly, it was a piece of junk as delivered, with more problems than you'll ever want to hear about. But over the next year, Cessna rebuilt a lot of it, so that eventually it was an OK airplane. Thereafter, for tax reasons, we rented it out, and I checked out each pilot renter except one, who was checked out by a different CFII. Unfortunately, proper engine management wasn't included in that check-out.

We began to have plug fouling problems soon after, as that particular renter pilot rented often. Finally, he and I had a talk. He was flying a 145 knot IAS airplane at about 100 knots indicated, by rolling back the power, both throttle and prop, until the fuel flow indicator (which was notoriously inaccurate) was showing 9 gph. He would grind along at 2000 rpm and whatever MP necessary to bring it down to 9 gph. He was leaning, but not accurately (we didn't have an analyzer--not sure now if they even made them then). Although the engine was turbo-charged, it was also carbureted (a real cobbled method that Cessna used for the first years of TR182 manufacture), which meant that fuel distribution wasn't very good, especially at those very low MP settings. So some cylinders were running rich, some were lean, and the engine was over-all running really cold--and that led to the fouled plugs.

The other reason: Why do we fly, instead of drive? Sure, flying is fun, and it lets us get to some places that aren't accessible by other means. But one reason is that it's quicker. Why fly an airplane capable of 130-135 knots easily, at only 100 knots? It's one thing to tool around the local area at best economy, but when going places, it makes more sense to me to use the airplane's capabilities to get there quicker.

Cary

Had 1 cylinder issue with low power settings on C180/O470-K and AVGAS. Went back to running 23/24 no more problems. I hate to say it, but I don't think we would have had problems if we had been using MOGAS. I have a friend who has a 182 they putt around with at 20/22 or something with zero problems using car gas.

We burned less fuel with the 206 than we did the 180 for our 30 minute ride to town. 206 was higher fuel flow but a solid 10 kts faster. Go figure that one...

Scolopax wrote: That only makes sense if I'm trying to demonstrate to a Maule driver that they have an inferior craft

It's about time you responded to my poke at Cessna Drivers, haha!

highroad wrote:

Scolopax wrote: That only makes sense if I'm trying to demonstrate to a Maule driver that they have an inferior craft

It's about time you responded to my poke at Cessna Drivers, haha!

Was wondering if you would catch that. It was sort of intended for you.

^^^^ Yep, what else are friends for?!

Looks like you would save about 4 gallons over a 200 mile trip. Don't know about the kindness to the engine.

I know I was loafing along at 19" 2100 on my O-540 and ended up with some pretty interesting lead fouling on one of my plugs.

TD

Another vote in favor of flying faster when going someplace:

if you factor in all the cost of flying and not just the fuel (extra hours on the engine, oil, airframe, etc) the best MPG speed is not usually the best MP$ speed. In my 180 (STOL kit, bubble windows, 8.5 tires), for a no wind condition, the lowest cost per mile speed ends up around 60-65% power and about 125-130 KTAS. Tailwinds shift the power setting for cheapest distance towards 55%, and headwinds closer to 70% (assuming that I'm at an altitude that allows 70% power). One caveat would be if the extra range eliminates a fuel stop, but with 84 gallons usable that is rarely a concern for the XC flights I normally fly.

I also love my stock 180 and sometimes use that low power setting, but as some others have said, the mpg isn't a lot better than 20" and 2200 rpm, that is where I do most of my cursing. At around 10K I usually get 130 knots and burn 10 gph. Hard to beat. In over 2000 hours I have never fowled a plug. It seems like I should overhaul the thing, but it is running too well.
I think that the folks that put on the aerodynamic mods are doing themselves a disservice. A buddy of mine modded up, and ended up almost 10 knots slower than me.
Did I mention that I love my 180?........

The point about plug fouling that Cary and others made is a good one - that can be corrected* with proper leaning technique (*unless your engine was never run in correctly). Personally, I'm not sure 15-30% more fuel burn is worth a few handfulls of KIAS every time - sometimes it makes sense.

Remember - one or two events does not make a trend

fredy wrote:Another vote in favor of flying faster when going someplace:

if you factor in all the cost of flying and not just the fuel (extra hours on the engine, oil, airframe, etc) the best MPG speed is not usually the best MP$ speed. In my 180 (STOL kit, bubble windows, 8.5 tires), for a no wind condition, the lowest cost per mile speed ends up around 60-65% power and about 125-130 KTAS. Tailwinds shift the power setting for cheapest distance towards 55%, and headwinds closer to 70% (assuming that I'm at an altitude that allows 70% power). One caveat would be if the extra range eliminates a fuel stop, but with 84 gallons usable that is rarely a concern for the XC flights I normally fly.

Hey Fredy, congrats on your first post!! It only took you 3 years... Haha.

The O-540 in the Bearhawk has operated for 700 hours so far at low power settings. Both auto fuel and 100LL are used. The power settings range from 19 to 21 squared and average closer to 19. At 19, it burns 8.5 to 9 gph and down to 8 with aggressive leaning. Takeoff is always at full power and it is normally pulled back by the time pattern altitude is reached. The only concern is getting the cylinders too cold in the winter so the power is bumped up to keep CHT's above 300.

All 6 cylinders have CHT and EGT sensors and it has very accurate fuel flow measuring. With 8:50 tires, 9gph yields 125mph TAS or about 14mpg ($38/hr fuel cost). At 14gph it can go 30mph faster at an auto fuel cost of $22/hr which also works out to about 11mpg ($60/hr fuel cost). I'm rarely in a hurry to get someplace and like to be low enough to see things on the ground which around here is usually below 8,000 msl. With a tailwind I'm higher and headwind lower.

At about 400 hours, it did have a stuck ring on #3, but review of the engine history before and after operation gives many reasons that could have caused it so without specific data pointing to any one cause, it remains an anomaly. Number 3 runs the coolest and number 5 the hottest.

If u wanna save fuel n avoid lead fouling try LOP.

Normally cruise at 22"/2400 n see 150-155mph at 10.5gph.

Just flew alongside a cub from CO to central TX at 15-18" and 2250 rpm. Fuel burn was 6.5 gph LOP for 13.5 hours. First time the new motor has used any oil, 1 quart.

I'm in the better to run hard than lope along camp, at least that's what I've heard my engine's tellin me......

I bought my '54 180 a year ago. Continued land slavery issues kept me from actually going anywhere, so my 40ish hours flown last year were around my home valley on MoGas at low power setting because I'm cheap and had nowhere to go. During the annual last May all of the compressions on my 350 hour motor came up low, 50's to low 60's. We discussed with smarter people and on their advice went out and flew hard for about two hours. Rechecked and all compressions came out in the higher 60's. Engine analyzer bought, not installed and now running mostly 24 square. I will reduce that some after we get the analyzer off the shelf and in the airplane.

Skalywag wrote:If u wanna save fuel n avoid lead fouling try LOP.

Normally cruise at 22"/2400 n see 150-155mph at 10.5gph.

Just flew alongside a cub from CO to central TX at 15-18" and 2250 rpm. Fuel burn was 6.5 gph LOP for 13.5 hours. First time the new motor has used any oil, 1 quart.

I'm in the better to run hard than lope along camp, at least that's what I've heard my engine's tellin me......

One thing to keep in mind is that aircraft engines should use oil. More information and an explanation can be found in this Avweb article, topic #5.

http://www.avweb.com/news/maint/182849-1.html

Well stated on LOP, too.