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#5317 - 04/05/10 06:31 PM 172 GPH when leaned out?
Cessna Dude Offline
Diamond Pilot

Registered: 10/21/09
Posts: 6628
Loc: San Antonio, TX
What fuel burn are you C172 owners (and dry-renters/leasers) achieving when at altitude, cruising leaned out?

And your motor HP as well? smile
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Due to certain economic uncertainty, the light at the end of the tunnel has been turned off until further notice.
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#5318 - 04/05/10 06:57 PM Re: 172 GPH when leaned out? [Re: Cessna Dude]
BBreeding Offline
Second in Command

Registered: 02/13/10
Posts: 203
Loc: Harrington, Delaware
I'm running an O-360-A4M 180 hp - get about 9.5 gal per hour (tach)at 2550 rpm. If I slow down a bit I can get it closer to 9 gph
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#5330 - 04/05/10 10:23 PM Re: 172 GPH when leaned out? [Re: BBreeding]
RodneyHooverCFI Offline
The Cessna Sensei
Gold Pilot

Registered: 02/16/10
Posts: 1642
Loc: Pasadena, MD
Haven't really nailed it down in the 172L with the 150HP O-320 that I currently instruct in due to not doing any cross-country flights in it except with one student, seems like those two flights came out really close to what we planned for though.
In the two 172Ps with the 160HP O-320 I used to instruct a lot in, we always came out within a couple of tenths of a gallon to what we calculated before the flight. Always interpolated the chart in the POH to the nearest tenth of a gallon. Power setting usually in the 60-75% range, so that's what, 7.something to 8.4 GPH.
I tell students that tacking 5 minutes to the first checkpoint will generally work out fairly well for accounting for the climb. Round down to the nearest whole knot or MPH for calculating groundspeed, up to the nearest whole minute for ETE, and up to the nearest tenth for fuel burn between checkpoints. Field elevations around here are typically 1,000 to 1,500 and I typically cruise at 4,500, 5,500, or 6,500.
Working out in the practice area seems to work out around 8 GPH, while strictly pattern work burns maybe a gallon or so less.
_________________________
Flight Instructor- ASEL and Instrument Airplane
Commercial Pilot with Instrument Rating- ASEL & AMEL
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#5336 - 04/05/10 11:25 PM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
TaylorSp Offline
Pilot in Command

Registered: 03/03/10
Posts: 313
Loc: Salina, KS
Our 172M has an 0-320-E2D 150 h.p. Over the winter I would lean to peak and then back in 3 clicks. In cruise at 4,500-5,500 ft, and OAT of 40, while running 2,450-2,475 rpm we are burning 6 - 6.5 gph. When we are doing touch and go's we average 5.25 - 5.5 gph. We have yet to calculate fuel burn with the increasing temperatures.
_________________________
1974 Cessna 172M
N13540
CFII/ Comm. Multi.

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#5340 - 04/06/10 12:02 AM Re: 172 GPH when leaned out? [Re: TaylorSp]
OldCrow Offline
Club Sponsor
Silver Pilot

Registered: 02/22/10
Posts: 887
Loc: STS, CA, USA
7-8 at 2350 lean with carb heat at 7500. normally with my short flights and multiple landings 10 is my planning number.
180hp O360 A2F 1969K model
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Another day in paradise
1969 172k AirPlains 180hp

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#5343 - 04/06/10 12:27 AM Re: 172 GPH when leaned out? [Re: OldCrow]
Nightowl Offline
Club Sponsor/Speed Demon
Gold Pilot

Registered: 02/14/10
Posts: 1826
Loc: Northwest lower Michigan
With our 180 hp O-360-A4M, we've averaged around 9.3 gph. We can easily get 3.5 hours plus reserve with 40 gallons usable.

John
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'77 C172N, AirPlains 180 hp conversion

Our sigmap has been flown entirely using aircraft with capabilities at or below those of the C-172.


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#5347 - 04/06/10 01:12 AM Re: 172 GPH when leaned out? [Re: OldCrow]
RodneyHooverCFI Offline
The Cessna Sensei
Gold Pilot

Registered: 02/16/10
Posts: 1642
Loc: Pasadena, MD
Originally Posted By: OldCrow
7-8 at 2350 lean with carb heat at 7500.

To me, that reads like you are running with the carb heat on the whole time you are in cruise. Am I correct?
_________________________
Flight Instructor- ASEL and Instrument Airplane
Commercial Pilot with Instrument Rating- ASEL & AMEL
Instructing at W00, Freeway Aviation.
States I've flown to-

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#5385 - 04/06/10 07:08 PM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
Rusty Rudder Offline
Diamond Pilot

Registered: 02/26/10
Posts: 5071
Loc: NorthEast
0-360 A4M @ 2200 RPM Leaned to Max minus 50 F 4500, 5500, 6500'
Last two fills almost 50 gal. 7.25 and 7.43 GPH. That being said, alot of that flying was cold & winter, a little more warm up and taxi time in there...
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#5410 - 04/06/10 11:43 PM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
OldCrow Offline
Club Sponsor
Silver Pilot

Registered: 02/22/10
Posts: 887
Loc: STS, CA, USA
I was trying to run LOP and read that the carb version ran better with carb heat to change the turbulence in the induction system.
Seemed to work
I am a new pilot and run short runs so am experimenting.
I am usually not trying to set any speed records as well so I run at the low end of the Rpm range and below the high power range to avoid detonation while running these experiments.
patrick
_________________________
Another day in paradise
1969 172k AirPlains 180hp

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#5412 - 04/07/10 12:18 AM Re: 172 GPH when leaned out? [Re: OldCrow]
RodneyHooverCFI Offline
The Cessna Sensei
Gold Pilot

Registered: 02/16/10
Posts: 1642
Loc: Pasadena, MD
Hmm, I really wouldn't recommend running in cruise with carb heat on when you aren't having carb ice issues. Carb heat air only has a screen over the inlet that is big enough to slide an ink pen through, so that's a lot of running with dust and grit going into the engine.
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Commercial Pilot with Instrument Rating- ASEL & AMEL
Instructing at W00, Freeway Aviation.
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#5414 - 04/07/10 12:31 AM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
OldCrow Offline
Club Sponsor
Silver Pilot

Registered: 02/22/10
Posts: 887
Loc: STS, CA, USA
not to mention the dratted flying Bic grin

Have not done this often just experimenting -- note my Planning at 10 which is my usual ROP rate -- trying to raise others with ROP LOP ideas.
Agree with your thoughts as well.
patrick
_________________________
Another day in paradise
1969 172k AirPlains 180hp

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#5416 - 04/07/10 12:42 AM Re: 172 GPH when leaned out? [Re: OldCrow]
RodneyHooverCFI Offline
The Cessna Sensei
Gold Pilot

Registered: 02/16/10
Posts: 1642
Loc: Pasadena, MD
Lol, "the dratted flying Bic" thanks for that!
Actually, I spend quite a bit of time in the air with the carb heat on. Most of my flying has been with Private students, so I have no telling how many hours in 3 different 172 with all the different maneuvers that have the power back and therefore have the recommendation of having the carb heat on. Doing that has always been a tricky dilemma for me. Don't want to have an issue with carb ice and I want students to have the habits to minimize the risk of carb ice, yet really don't like the idea of running around so much with unfiltered air being sucked into the engine.
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Flight Instructor- ASEL and Instrument Airplane
Commercial Pilot with Instrument Rating- ASEL & AMEL
Instructing at W00, Freeway Aviation.
States I've flown to-

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#5443 - 04/07/10 06:38 PM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
OldCrow Offline
Club Sponsor
Silver Pilot

Registered: 02/22/10
Posts: 887
Loc: STS, CA, USA
Having experienced carb ice early after getting my ppl I frequently pull it on even if I am at the outer edge of the yellow on the carb (ice) temp gage.
A little engine abrasion vs major Terra event is fine with me. Blackstone says very little silica in the oil so that may be another way to tell if the carb heat on is causing issues.

For the amount I fly a few extra gallons used by ROP vs LOP is not an issue.
Fun to learn however.
Good to hear you are talking to your students about Carb ice- Not sure the training I had forced that issue as much as it should have.
I would love to have a simplified way to look at the "gages we typically have" and quickly judge if we were at risk.

my only tool is the carb temp, but without that not sure if forecast info is the best.

Engine rpm is the next best as you indicate. Perhaps that is all there is.

Appreciate the discussion, that is why we are here..

We may have hijacked this thread -- back to your regular GPH discussion -- sorry
Patrick


Edited by OldCrow (04/07/10 06:39 PM)
Edit Reason: Hijack
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Another day in paradise
1969 172k AirPlains 180hp

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#5447 - 04/07/10 07:46 PM Re: 172 GPH when leaned out? [Re: OldCrow]
RodneyHooverCFI Offline
The Cessna Sensei
Gold Pilot

Registered: 02/16/10
Posts: 1642
Loc: Pasadena, MD
Heck I've only been in like 2 planes that had a carb temp gauge. Don't understand why every plane doesn't have full EGT, CHT and carb temp (if applicable) drives me crazy having to just guess at such important information. Just have to go by engine sound and feel, plus RPM for typical times for turning the carb heat on. Only time I've had ice form was on the ground, noticed it during run-up. Ooops, yeah, definitely hijacked this thread, now back to regularly scheduled programing....
_________________________
Flight Instructor- ASEL and Instrument Airplane
Commercial Pilot with Instrument Rating- ASEL & AMEL
Instructing at W00, Freeway Aviation.
States I've flown to-

Airport list map:
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#6479 - 04/23/10 11:00 AM Re: 172 GPH when leaned out? [Re: RodneyHooverCFI]
Glenn Darr Offline
Club Sponsor
Gold Pilot

Registered: 03/01/10
Posts: 1630
Loc: Arizona
I have 1969K with a 320-E2D engine, and at 2400 rpm I usually but 6.2-6.6 gph.
Glenn
1969 172K
W45
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Glenn
1969 172K
KAVQ

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#6503 - 04/23/10 03:50 PM Re: 172 GPH when leaned out? [Re: Glenn Darr]
TaylorSp Offline
Pilot in Command

Registered: 03/03/10
Posts: 313
Loc: Salina, KS
Our 74' 172M with the O-320-E2D gets the following:

2,450 RPM: 5.5-5.8 and 118 mph cruise
2,500 RPM: 6.5-7 GPH and 122 mph cruise
2,625 RPM: 8-9 GPH and 127 mph cruise

Leaned as follows: Lean to peak, then in 3-4 clicks.
_________________________
1974 Cessna 172M
N13540
CFII/ Comm. Multi.

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#6526 - 04/23/10 08:34 PM Re: 172 GPH when leaned out? [Re: OldCrow]
Wayne W Offline
Safety Pilot

Registered: 10/22/09
Posts: 70
Loc: West Texas
Originally Posted By: OldCrow
not to mention the dratted flying Bic grin

Have not done this often just experimenting -- note my Planning at 10 which is my usual ROP rate -- trying to raise others with ROP LOP ideas.
Agree with your thoughts as well.
patrick
Why not just run your engine by the book? That is a proven way to lean and is recommended by the guys that built your airplane.
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Happy Landings
Wayne
Visit my website..... http://wings.esisupply.com

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#12109 - 09/14/10 07:26 AM Re: 172 GPH when leaned out? [Re: Wayne W]
Rusty Rudder Offline
Diamond Pilot

Registered: 02/26/10
Posts: 5071
Loc: NorthEast
0-360 A4M @ 2200-2300 RPM Leaned to Max @ >65% power, Most recently, 7.6GPH, 7.7GPH and 8.5GPH for a tank full burned @ full power.
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