Couple of newby ops questions

ALASKA99762 · Post by **ALASKA99762** » Thu Jun 08, 2006 6:16 pm

I'm still getting acquainted with 10C, and am concerned with oil temps and fuel cusumption. On two seperate flights at 40F and cruising low at 2100 RPM my oil temp never got above 150 and my fuel usage was 9.5 gal per hour.

Should I be concerned? I do have the oil cooler blocked with what I assume is part of the Cessna winter kit.

Should I lean while cruising at low altitudes...500-1000 MSL?

Is there any harm in cruising along for 2-3 hours at this low RPM setting?

Thanks for your help. Bryan

Jr.CubBuilder · Post by **Jr.CubBuilder** » Thu Jun 08, 2006 6:57 pm

Burning that much gas at 2100 rpm sounds high to me, I would expect 8gph if I were loafing around at that rpm, maybe less. The oil temp sounds about the same as mine though, I leave my oilpan cooler opening covered till it gets over 35F.

lowNslow · Post by **lowNslow** » Thu Jun 08, 2006 7:45 pm

Bryan, assuming you have a O-300, that fuel flow sounds high to me as well. When I am out just boring holes, I usually burn about 7.6 gph at 2200rpm, and yes I always lean at any altitude. Your oil temp sounds normal for 40F.

Mike Smith · Post by **Mike Smith** » Thu Jun 08, 2006 8:47 pm

I always lean when cruising. Given that you were running full rich, that may be about right on the fuel burn, it's hard to say since I don't cruise at full rich. I do know that if I run at a high RPM at low altitude I can get it to burn just over 9 gph (and I lean for that also). The oil temperature is something you will have to figure out with your own airplane since you are basically "experimenting" with the configuration by changing its cooling ability. Not that this is a bad technique, but since this is not "standard" you will just have to make your own notes/tests and see what works best for you and your airplane.

Good Luck

ALASKA99762 · Post by **ALASKA99762** » Thu Jun 08, 2006 10:13 pm

Thanks for the advice, guys. Seems that every flight there is something that gets my attention. Tonight I'll lean the mixture and see what difference it makes.

Converted a buddy last night who has been telling me not to waste money on a plane. I guess seeing 7 grizzlies in an hour and covering so much ground got him thinking. He wants flying lessons now!

Thanks again.

alaskan99669 · Post by **alaskan99669** » Sat Jun 10, 2006 1:55 am

Bryan,

I followed a buddy in his PA-12 from Kenai to Bristol Bay and back. I had to idle back to 2150 to match his speed. We flew for 7 hours and my fuel burn was only 6.5 GPH. Most of the flying was below 2,000' and I lean at all altitudes. I burn 8 GPH at 2450 RPM.

My oil temp stays just below the center of the green gauge with the square vent covered in the front and two rubber plugs in the inlets of the blast tubes at OAT from 0 to 50+.

Post by **GAHorn** » Sat Jun 10, 2006 4:27 pm

It's easy to know what this engine should do. The Owner's Manual has the performance data in it at most altitudes/rpms . The 170A manual states that at 3K feet altitude, 2100 rpm should burn 7.3 gph rich and 5.5 gph leaned. It also gives the range and endurance at whichever rpm you are using.
Oil temperature questions come up all the time, and the FIRST thing to do whenever questioning oil temps is to confirm the cockpit gauge accuracy. (They are notoriously bad.) A long, BBQ thermometer probe stuck down the dipstick tube will confirm the current reading. (Don't do this in flight. Only on the ground. Otherwise you might fall out of the plane trying to read it. )

The usual complaint is too high oil temps. Too low temps (in other than arctic conditions) is usually an inaccurate indication.

spiro · Post by **spiro** » Mon Jun 12, 2006 1:29 am

under 65%hp you can lean without restriction. That's like 2350rpm w/ stock prop according to the book. Lean is clean. Fewer fouled plugs, stuck valves.

I run mostly 100LL and so aggressively lean at all times except takeoff. 2300rpm w/ 7653 prop or 2400rpm w/ 8042 is my cruise, they burn about the same and similar speeds. Last 10 years average is under 7gph.

oil temp sounds fine. Look for deviations from what's usual, not a specific number - it's not a very accurate system. In the winter w/ full covers and W65 I'm sometimes happy to see it reach the green.

ALASKA99762 · Post by **ALASKA99762** » Mon Jun 12, 2006 5:01 am

Thanks again for the advice. I'm leaning now and getting the numbers you've suggested. Learning more everyday.

Abe · Post by **Abe** » Tue Jun 13, 2006 3:26 am

Spiro,
Glad to hear someone else is getting a fuel burn of less than 7-gals/hr..I was beginning to think my tack was off. I have a 7551 Prop and cruise most often at 2450 rpm at 5K - 9K here in NE Oregon and lean at all altitudes and takeoff (we're at 4K at our airport). I have put 190 hours on 2604D and for those hours I have burnt 6.26 gal/hr. I always get a funny look when I share these numbers with other. Thanks for sharing your numbers.

Post by **GAHorn** » Tue Jun 13, 2006 5:58 am

Abe wrote:Spiro,
Glad to hear someone else is getting a fuel burn of less than 7-gals/hr..I was beginning to think my tack was off. I have a 7551 Prop and cruise most often at 2450 rpm at 5K - 9K here in NE Oregon and lean at all altitudes and takeoff (we're at 4K at our airport). I have put 190 hours on 2604D and for those hours I have burnt 6.26 gal/hr. I always get a funny look when I share these numbers with other. Thanks for sharing your numbers.

Abe are you sure you have a 7551 prop?

beeliner · Post by **beeliner** » Tue Jun 13, 2006 12:23 pm

Not only what it says in the specs or on the prop, but check the logs thoroughly. My prop is a "53 but was shortened many years ago due to nicks on the tip. It now is just over the minimum allowed length. I still get good numbers and it it very smooth so I guess it's OK.

Cruise full throttle @ >8500msl = 7 gph and 100-105kts gps & true (leaned to just above rpm drop).

Post by **GAHorn** » Tue Jun 13, 2006 1:52 pm

I'll bet then, that it's still a 7653...which has been shortened... not modified to a different model.

Abe · Post by **Abe** » Tue Jun 13, 2006 3:06 pm

When I first got 2604D in Feb of 2003 it had quite abit of vibration according to our AI here and the FBO gent. We flipped it 180 and it took about half the vibration out. Still not satisfied we sent it to a prop shop in Troutdale, OR and they called us back up and said that this prop was no good and had no temper as it had been in a fire at one time...Hard to believe that someone, sometime sold this prop knowing it was no good...Now it's a wall hanger....So they looked around and found the current prop a McCauley Model DM7551/1Ci60 SN#52295. The prop log says it's overhauled, reconditioned, and set angles.

Post by **GAHorn** » Tue Jun 13, 2006 9:43 pm

Yep. Buying used airplane parts from unknown sources is hazardous.
The 75XX model is not listed as an approved propeller for this airplane, neither is the 1C160. You should find an alternative approval basis if that is what you actually have. IMHO