How concerned should I be about throttling back for lower fuel burn?

Kenny Phillips said:
Yeah, I was so guilty at the latter that I stopped logging those hours. (Now I'm digging through paperwork to add 'em back in! Just because; no desire to fly professionally.)
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I did the same thing with SCUBA diving. I was on Guam for four years and stopped logging for six months (until my Dad came to visit then I started logging again) and still managed over 500 dives in the logbook. They were not, however, the same dives over and over again. My dive buddy was just as adventurous as I was and we made some pretty interesting dives.
 
Ryanb said:
Don’t fly in circles, fly somewhere. Flying in circles will get old quickly and it’s not very productive.
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He didn't say anything about flying circles, just that he wants to fly at very low speed/power/fuel burn. You can fly from any point on the continent to pretty much any other point on the continent at 2100 RPM if you want. The only penalty would be that it'll take more time than if you flew that trip faster. And since building time is the object, its not a penalty at all. Sounds to me like all that's being asked is if there is any concern for the engine in doing so.
 
MarkH said:
running 130Kts at 9gph does not make much sense when I am flying in circles to build time after work.
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Juliet Hotel said:
He didn't say anything about flying circles
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Refer. :cool:

Nothing wrong with low and slow, nor did I say there was. Do whatever suits your fancy! I just offered my thoughts on a few things that came to mind after reading the question asked.
 
aftCG said:
Well I did have more in my post but deleted it since I just wanted point out why he won't have power tables for this engine application, and to poke a bit of fun at the OP.
So here goes:
My Citabria has an STC for the O-320 (from the O-325). Even though the pamphlet that serves as the POH/AFM is scant, it does have power tables for the O-320 because the factory produced that variation.

That said, the extra power in my case is great at getting the plane off the ground and climbing very well but you have to burn a lot of gas to get much more top end speed out of it. As such, I do commonly fly at 2200 rpm, which gives me 90mph - and when leaned half way properly burns a documented 4-4.5 gal/hr. Running at 2500 rpm only gives me 105 mph for almost double the fuel burn. I'm not bulking up my log book at this point but I do get in an airplane to enjoy the flying part, so the OP's intent doesn't strike me as insanity. At 90 mph my plane is much quieter and passengers even comment on how nice the ride is. I can and do have the option of using all the power available to fight a stiff headwind, beat some weather/darkness or get over the mountains before it gets rough. It's nice to have.

As for operating the O-320 below the green arc, SOP for instrument conditions in the C172 when I got my rating was 1900rpm which produced 80 knots in level flight and we used that for holds and most things on the approach plate. Just one of the (many) reasons was that you could go missed by just applying power and not even need to trim. We flew for hours that way, no problem.

Back to the OP's situation. You bought a stubby wing plane. I've read that they're a scream with the 150hp STC and they have been on my short list of planes before. There is most certainly a reduced power setting, like 2200 or 2300 which will give you a very efficient cruise without wallowing around in the sky. Go find out what RPM is required to hit the book speed for your 4.5 gal/hr figure and work from there.
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Thank you, this is very informative.
 
Tantalum said:
^don't do that

If you're nervous to leave the safety and comfort of the 51nm radius around your home airport you need to work on that first before going to the same airport 50.1 nm away dozens of times. You will learn a lot more planning and executing a longer leg.. especially if you are trying to build time to do this as a career.
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Yes I said flying in circles, no it was not entirely literal.

Having said that, am I the only person who just likes being in the air? Yes I want to plan and fly legs, I want to go airplane camping, I want to island-hop in the Carribean, but when I get off of work, have dinner plans and want to fly for a bit, I don't intend to just stay on the ground because I am not going to a destination.

Sometimes, my mission is to eat lunch in New Orleans or travel to a new airport. Sometimes its to go on vacation.
Sometimes I just want to go up and get pictures of the sunset. Will I make it a career, I don't know, but I intend to get commercial ratings so I have the option.

For some of those, 125 knots cruise is going to be amazing, for others it will not add much.

And for everyone who thinks flying in circles is a bad thing, I will give you some free advice: soon, on a nice day when the sky clear, take your plane flying a bit before sunset, not to practice landings or go somewhere, but just to meander around and enjoy the sights and the calm of being in the air. It's the most relaxing thing I have ever done and some of ya'll clearly need that.
 

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MarkH said:
And for everyone who thinks flying in circles is a bad thing, I will give you some free advice: soon, on a nice day when the sky clear, take your plane flying a bit before sunset, not to practice landings or go somewhere, but just to meander around and enjoy the sights and the calm of being in the air. It's the most relaxing thing I have ever done and some of ya'll clearly need that.
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Hey I can relate. I do a good bit of that type of fun flying!
 
MarkH said:
just to meander around and enjoy the sights and the calm of being in the air
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Totally.. that's what flying is all about, right? Initially you said you were trying to build time so I assumed you were going towards IR / commercial, with a focus on saving costs. But yes, the afternoon cruise is great fun!!

Cheers
 
Ryanb said:
Refer. :cool:
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Oh crap, I missed that. Count me with the others in that case. If your goal is to represent yourself as having 1500 hours of aviation experience, go out and get 1500 hours of meaningful experience, not 1500 hours of circling the same herd of cows in a pasture.
 
Might as well fudge your logbook if you’re not going to get real experience.
 
Wow, this thread turned "judgey" pretty fast.
He has 7 hours in his new plane, and asked a perfectly reasonable question, nothing to do with career-building.

@MarkH, spend your airplane time in whatever manner you like, enjoy it, and don't listen to anyone who says it's not "real" or "meaningful".
 
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Not an O-320, but in my O-200 powered C150 when I want to just putt around and look at the sights, I often pull the power back to 1800 rpm, which is well below the performance charts and likely down in the 40-45% power range. I get fuel burn of about 2.9 gph, 75 mph (which is pretty close to best glide speed and therefore best L/D), and haven't had any more fouled plugs, gunked up valves, or other troubles. Not exactly data for you, but one data point anyway.

Patrick
 
Depending on airframe pulling the power back by 1 gph is most likely only 10 mph or so in exchange you can save 6-7k over 1500 hours. Not to mention the engine hours add up slower saving you money there as well.
 
how about listing to the radio while idling on the ramp....and logging those hours? You could save lots of fuel that way....o_O
 
Wow, it is entertaining to be on poa. Good on you, mr OP for standing in there and taking the beating.
 
There’s absolutely no down side to going slow while time building. Time building is done by the hour, not the mile. Just be sure you keep enough power to keep it from stalling easily. Don’t plan on mushing through the air.
 
Salty said:
Might as well fudge your logbook if you’re not going to get real experience.
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This wasn’t meant to be judgey, or harsh as it may have sounded. I don’t even care if you fudge your logbook. It ain’t my job. But I’m serious that I don’t see the difference between fudging your logbook and flying in circles slowly to build hours. Neither make you a better pilot and fudging the logbook is much cheaper and safer.
 
Ryanb said:
.........,,

Is the RPM sufficient to provide good oil pressure? CHT and OilT staying healthy at that power, speed, and pitch configuration?

The most concerning thing is to check if your oil is running too cool. The bearings, cylinder pressures etc all like running at low power but unless you’re getting around 70c, the oil won’t evaporate the moisture from your engine.

Nonetheless, trying to run an O-320 like an O-200 is kind of obtuse, but each to their own.
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Agree. Getting the oil warm enough to burn off the combustion creating moisture will no doubt reduce engine corrosion but the lubricating quality of oil at the proper operating temperature is equally important.

The other aspect is that, if your engine is carbureted, reduced RPM sets you up for more CARB ICE and a cold engine that has less excess heat to amply supply CARB HEAT to melt that ice. Carb ice is not infrequently seen by us IFR flyers when flying practice holds and approaches at reduced speeds, in the right conditions. So clearing the engine frequently and using carb heat at frequent intervals become more important.

And definitely lean to peak egt at those low power settings.
 
Instead of pulling power back, why not just climb so high that you're burning O-235 burns? I don't know anything about grummans (grummen? :D) but I'd think 12K and up would be highly economical and still get some groovy TAS so you can go places and get experience.

I go high when I need to stretch my endurance.
 
Gas is the cheapest thing you'll put in an airplane. That is true of a 414 burning 34 an hour, or a 150 burning 4.5.

As for the "building time flying in circles thing," I just don't get this mentality. Why not go somewhere? A Lynx is, in many ways, the ultimate certified 2 seater. MUCH better in turbulence than a 150/2, fast enough to be an actual travelling plane and really economical. Even with the O-320, your fuel burn is negligible. A 3 hour XC takes just as long as 3 hours abusing your plane in the pattern. One flown fast means you just open yourself to interesting places.
 
God forbid that someone would just want to fly around a bit for the sake of flying around a bit.
Never fly on a nice day because it is too easy.
If you ain't scud running, you ain't running at all.
Always run full rated power, full rich. Real pilots light cigars with $100 bills.
 
Checkout_my_Six said:
how about listing to the radio while idling on the ramp....and logging those hours? You could save lots of fuel that way....o_O
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Just be sure to set the brake or pay attention. If you drift off then idle into a hangar & cause an ‘accident’, your hour building scheme will backfire.
 
Salty said:
I don’t even care if you fudge your logbook. It ain’t my job. But I’m serious that I don’t see the difference between fudging your logbook and flying in circles slowly to build hours. Neither make you a better pilot and fudging the logbook is much cheaper and safer.
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You said it much eloquently than I could have. If you're hoping to build time to go do more advanced flying (assuming that's your reason for wanting to build hours) you're not doing yourself or anyone else any favors by burning the clock orbiting the local area at low power. Gee great you've got X hours in your book so here's the keys to company jet. But you won't have nearly the level of actual aviation experience as someone who got their time by going from point a to point b and point a to point c and point a to point d etc.

You want to fly slow? Great do it. But go someplace while you're doing it. In fact go many places. Make it a goal to visit every airport in your state and every airport in every state that touches your state. Do some of those flights with your GPS. Do some with only VORs if you can. Do flights to airports you've never been to and navigate using nothing but a sectional and a windshield. In other words challenge yourself to do something you've never done or are otherwise not strong at on every flight. That's what time building should be about IMO.
 
MarkH said:
I decided to buy a plane to travel and build time. I was shopping for a Cessna 150, but I found an Grumman AA1C with an O-320 and bought that instead.

One of the things I was looking forward to was building time 5gph in the Cessna, I recently flipped through a manual for an AA1B and noticed that it shows a power setting for cruising at 52% power on 4.5 gph. In theory, my O-320 should get similar fuel burn at similar power outputs (approx. 56hp), but it would require throttling back to 37% power and most performance charts do not go below 50% power.

Are there any risks to throttling that far back in cruise? Is there anything I should watch out for if I were to try this?
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All I know is my fuel flow instrument pegs around 12.5 gallons per hour at full throttle on cooler days (O-320-E2D) 6.5 gallons is doable at 5500 or so feet but its slow, but the airplane is a lot bigger and hold 48 usable gallons. Given the power to weight ratio is more unfavorable I usually need to climb at full power for 12 minutes or so to my typical cruise altitudes (4500-6500 from 1320) on hotter days
 
My Tiger handbook goes down to 40% power at 10000 ft pressure altitude and the highest temperature option. So that's within the operating range its O-360.

There is a pilot who frequently posts on the Grumman Gang mail list who flies his Tiger long distances at slow maximum endurance speeds that correspond to below 40% power (he explains that going high for favorable winds and avoiding fuel stops provides shorter door to door times for his mission). I will also do that on a $100 omelet run to give me more time to enjoy the flight (particularly with a tail wind). When doing this my oil temperature is in the green, and I do not have issues with either carbon or lead fouling of my plugs. CHTs are low (280-300F on my EI CGR-30P with EI bayonet probes), but annual borescope cylinder examinations show no combustion deposit buildup internally. We lean following the handbook guidance of leaning until rough and enriching until smooth.

So at least with AA5's, I haven't seen evidence of any issues flying at <40% power either with my plane or others who have posted online. If you want to get input from people with the most AA1x experience, I encourage you to sign up for the Grumman Gang mail list (http://grumman.net/) and ask your question there.

Give the open canopy a try while you're puttering along. And enjoy.
 
MarkH said:
Yes I said flying in circles, no it was not entirely literal.

Having said that, am I the only person who just likes being in the air? Yes I want to plan and fly legs, I want to go airplane camping, I want to island-hop in the Carribean, but when I get off of work, have dinner plans and want to fly for a bit, I don't intend to just stay on the ground because I am not going to a destination.

Sometimes, my mission is to eat lunch in New Orleans or travel to a new airport. Sometimes its to go on vacation.
Sometimes I just want to go up and get pictures of the sunset. Will I make it a career, I don't know, but I intend to get commercial ratings so I have the option.

For some of those, 125 knots cruise is going to be amazing, for others it will not add much.

And for everyone who thinks flying in circles is a bad thing, I will give you some free advice: soon, on a nice day when the sky clear, take your plane flying a bit before sunset, not to practice landings or go somewhere, but just to meander around and enjoy the sights and the calm of being in the air. It's the most relaxing thing I have ever done and some of ya'll clearly need that.
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Mark, great sentiment. Here's one more resource for you that, while it is not directly applicable to your AA1x, does relate to Grummans. It is an article written by Ron Levy (Captain Ron) and published in the AYA Star magazine over 20 years ago and it is still relevant today. The main points that are relevant to your question is that the discussion covers speeds that represent power levels in the range that interest you, and the Cheetah runs the same basic engine as yours. There is no mention of downsides to operating in that regime (other than bladder endurance).

Mark, after I posted this message I went back to find where I got my copy of the article I referenced and could not find it publicly available online. I should not have posted it here without either Ron's or the magazine's permission. So I deleted it.

Instead, here is a link to the article by Melville Byington, Jr. which was referenced in Ron's publication. It contains data on the Tiger along with several other piston singles, and, while I do not have power data for other than the Tiger, the max range airspeeds are so low for most that they must be at power in the range you are considering.

https://commons.erau.edu/cgi/viewcontent.cgi?article=1115&context=jaaer
 
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bkspero said:
My Tiger handbook goes down to 40% power at 10000 ft pressure altitude and the highest temperature option. So that's within the operating range its O-360.

There is a pilot who frequently posts on the Grumman Gang mail list who flies his Tiger long distances at slow maximum endurance speeds that correspond to below 40% power (he explains that going high for favorable winds and avoiding fuel stops provides shorter door to door times for his mission). I will also do that on a $100 omelet run to give me more time to enjoy the flight (particularly with a tail wind). When doing this my oil temperature is in the green, and I do not have issues with either carbon or lead fouling of my plugs. CHTs are low (280-300F on my EI CGR-30P with EI bayonet probes), but annual borescope cylinder examinations show no combustion deposit buildup internally. We lean following the handbook guidance of leaning until rough and enriching until smooth.

So at least with AA5's, I haven't seen evidence of any issues flying at <40% power either with my plane or others who have posted online. If you want to get input from people with the most AA1x experience, I encourage you to sign up for the Grumman Gang mail list (http://grumman.net/) and ask your question there.

Give the open canopy a try while you're puttering along. And enjoy.
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40% in a Tiger means you're still going at a reasonable clip. 40% in a Lynx is pretty slow. There is a 15-20 knot difference between the two.

Also, 280-300 on EI means 350-370 on JPI
 
"God forbid that someone would just want to fly around a bit for the sake of flying around a bit.
Never fly on a nice day because it is too easy.
If you ain't scud running, you ain't running at all.
Always run full rated power, full rich. Real pilots light cigars with $100 bills."

My kinda guy ….. ;)
 
Take a few cross countries at whatever power setting works for you.
 
Southpaw said:
"God forbid that someone would just want to fly around a bit for the sake of flying around a bit.
Never fly on a nice day because it is too easy.
If you ain't scud running, you ain't running at all.
Always run full rated power, full rich. Real pilots light cigars with $100 bills."

My kinda guy ….. ;)
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Absolutely nothing wrong with wanting to go fly just to go fly. But kind of by definition, if you're a person who is looking to go fly around a bit just for the sake of flying around a bit, you are not a person who is the least bit concerned with trying to build time. There was a time when I was obsessed with logging every possible minute trying to build time to get to the next level and open up the doors for that job on the next rung up the ladder. Toward the end of my career, I went hole months of flying 5 and 6 days a week and never once putting a pen to my logbook. Still liked flying but hated flying for a living and could not care less about building time.
 
N1120A said:
40% in a Tiger means you're still going at a reasonable clip. 40% in a Lynx is pretty slow. There is a 15-20 knot difference between the two.

Also, 280-300 on EI means 350-370 on JPI
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A couple of corrections.

Based on the detailed 2014 Cubcrafters study which compared EI, JPI, and three other probes and their respective engine analyzers (copy attached to this note), the average temperature difference between EI P-100 probes (as I have) and JPI M-5050T bayonet probes was 44 degrees F in cruise flight. So the 280-300F I see with my EI installation is no more about 325-345F, not 350-370F. That means that my cylinders would be still considered less than hot even if I had a JPI system. And whatever the temperature actually is, the key point is that I have no issue with combustion deposits or plug fouling when operating my Tiger for extended times at =<40% power and the CHT's that produces.

As for the speed, 40% power in a Lynx would be slower with the stock 115 hp Lycoming O-235-L2C. But the OP's airplane has an O-320, so it has at least 150 HP. People flying that combination typically report Tiger airspeeds (or even better...for example, see http://grumman.net/archive/2001/msg09090.html), so 40% power in the OP's plane and a Tiger would likely put their speeds in the same ballpark, not 15-20 kt slower for the Lynx (not that it would be a problem if the OP chose to enjoy flying slower).
 

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