leaning procedures and EGT

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Runk170
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leaning procedures and EGT

Post by Runk170 »

After incurring stuck exhaust valves, I've been reading s lot on the C-145/0-300 leaning procedures, fuel flow at cruse but have never seen a recommended EGT to lean to. We all know the old procedure of leaning "pull it out till it stumbles then in 4 clicks" but I'm looking for more information on the subject. Best cruse EGT? What is your fuel consumption? Have you also had sticking exhaust valves? Please share your experience and observations. Thanks! See you all at OSH!
counsellj
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Re: leaning procedures and EGT

Post by counsellj »

There is no Magical Target EGT. Your EGT will vary based on outside temps, humidity, fuel used, power setting etc. If you really want to get smarter about EGT, I recommend you do an internet search for John Deakin or Mike Busch. Both are well respected engine operations advisors that have written and taught extensively in this area as well as others. Are you running a multi cylinder instrument or single cylinder gauge?

Hope this helps.

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GAHorn
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Re: leaning procedures and EGT

Post by GAHorn »

Deakin and Busch have some good stuff to say....about highly instrumented, fuel-injected/turbocharged/geared engines. The articles they've written, at the least the ones I've read, do not help much when one is operating an engine like a normally aspirated, direct-drive, fixed-pitch-propeller equipped like ours.

Our C145/O300 engines have very crude carburetion/induction systems. Only one-third of the cylinders receive similar fuel/air mixtures at any given time. Add to that the rudimentary fuel-metering of the MS carburetor and you have all the refinement of the flywheel steam engine era.
(That's not an attempt at humor. It's an accurate description of the standard installation.)

Stuck valves are usually caused by lead-deposit build-up on the valve stems of engines which have been assembled with incorrect valve-guide clearances, frequently operated at overly-rich mixtures. Rapid cool-down during the landing phase followed by a varied throttle taxi to the ramp and rapid shut down without a temperature-stabilizing period of idling contributes to the problem.

You can put a highly accurate and technical engine monitor on these things and, while you can readily see the variations between cylinders, you only have an expensive display of the matter. Which of the six cylinders do you wish to lean perfectly? And which do you wish to subject to less than that? It's like measuring pancake batter with an apothecary scale. You can make fine pancakes simply by adding water until the flour makes a nice, creamy batter and then spoon it onto a greased griddle.

The Owner's Manual actually gives the best method, IMO. Establish a stabilized cruise with a power setting commensurate with the performance tables in the manual. Lean the mixture until max RPM is achieved, then continue leaning slowly until the first indication of RPM degredation,...then enrichen just back to the maximum RPM.

Now, when you decide to make a cruise descent... don't touch that mixture. (Most written material recommends RICH descents and approach/landing. I do not recommend that. I recommend not enrichening unless a higher power setting than what was used in cruise. More on that later.)* Leave the mixture at the cruise setting until after landing until shut-dn. Taxi to the ramp with that setting. Allow the engine to idle at around 800 RPM for at least one minute, then pull the mixture to cut-off.

*If one decides to change an enroute cruise altitude and/or power setting, then completely re-perform the leaning procedure.
In addition, when making a go-around/rejected landing, enrichen mixture appropriately**. RE-lean during downwind.

**What is "appropriately"? Well, if I'm merely adding power gently because I'm abandoning an approach and needing only sufficient power to level-of and fly the pattern...I don't richen at all. ( I limit my power to cruise or less.)
But if it's the "Damn the Torpedoes! Full Speed Ahead!" ...type of go-around ... the sort of thing that really never happens unless an instructor is trying to put the fear of God into a student, or a pilot was asleep at the wheel, or if he stupidly wants to put the fear of God into the guy that he had crowded up behind during his own poor pattern-planning and want to let-off some steam with an idiots buzz-job.... :evil: ....
...in other words, if you are going to actually apply full-power on a go-around, then open your right hand up and include the mixture along with the throttle and carb heat knobs when you push 'em in.
(The rare times when that event will occur will not be significant in terms of proper leaning and stuck valves.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
counsellj
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Re: leaning procedures and EGT

Post by counsellj »

George,

Yes both gentlemen do focus on the engine and operation types you mentioned. But they still have great information for all other engine types. Plus, much of the high performance fuel injected info is till applicable to our engines. I lean the same way you do. Never had any problems with valves either.

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jrenwick
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Re: leaning procedures and EGT

Post by jrenwick »

Wow, George! I agree with almost everything you said, except that leaving the mixture leaned through landing is really radical, and contradicts what almost everybody has been taught. GUMPS! "Red, blue, green, runway's clean" on final, etc. I expect an instructor would hear from the examiner about that if a student did it during a check-ride. It's a set-up to have the engine stumble at the worst possible moment when you forget to shove all three controls forward, at a time when you least want to be debugging a problem. Sorry, I just can't go along with that!
John Renwick
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Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
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GAHorn
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Re: leaning procedures and EGT

Post by GAHorn »

jrenwick wrote:Wow, George! I agree with almost everything you said, except that leaving the mixture leaned through landing is really radical, and contradicts what almost everybody has been taught. GUMPS! "Red, blue, green, runway's clean" on final, etc. I expect an instructor would hear from the examiner about that if a student did it during a check-ride. It's a set-up to have the engine stumble at the worst possible moment when you forget to shove all three controls forward, at a time when you least want to be debugging a problem. Sorry, I just can't go along with that!
Yes, I know what you mean. But the masses are taught the "dumb 'em down" methods" and examiners feel the need to "teach" (even tho' that's not their job.)

Example: Newbies are taught to pull carb heat before power reduction in the pattern and leave it there until after touch down.

But... what about the go-around? Oh... now they're supposed to remember to turn OFF the carb heat.
What's different about remembering to push rich on the mixture on a go around?
And what's wrong with simply "clearing" the carb of ice with application of carb heat...check the tach...see no ice accumulated...then turning carb heat OFF for the remainder of the approach/landing? (and guess what?...no need to remember to turn it off in case of go-around.)

It's a matter of "dumbing down"... OR..... teaching the reasons things are done and then... simply requiring excellence in piloting skills.
If you want to teach dummies to fly...then keep pulling carb heat incessantly/forever in the pattern and running the mixture RICH simultaneously...and see what THAT does to spark plugs and valves.

I'd like to think my students are smarter and teachable and more capable than that.

Anyway...the question of the thread was for recommendations on leaning and avoiding stuck valves and that's the way to do it, IMO.

(And, by the way, ...if you want everybody to do "what almost everybody has been taught" ....then you can also forget about Deakin and Busch too.)

"What almost everybody has been taught"...also addresses constant speed props (among a host of other things.) Everybody has been taught to shove the props up to fine pitch before landing, presumeably in the expectation of the "Damn the Torpedos" go-around. Of course, that places unnecessary strain on engines, props as well as passengers...and creates drag when it's not needed which results in a necessary change in throttle to continue a stabilized speed.... but it does make the noise level sound like something important is about to happen so that pax can get concerned.

I don't know of ANY real professional that does that, they leave the props where they were during descent and all thru the touchdown, only moving them to fine pitch after touchdown or in the event of go-around.

I once had an Army C-12 pilot transitioning to the civilian King Air 200 (essentially the same airplane) on a trip to SAT. My cropduster director thought military pilots were the cats-meow. (And let me be clear. They ARE! They are the true professionals in what they do...operate expendable equipment for combat or support. The difference between military and civilian flying is similar to the difference between fresh water and salt water fish. They both swim. But few of them do well in the other environment without serious adaptation.)

<edit: Revisiting this thread made me realize I left a comment hanging...: My "boss" was the director and because of his opinion he had instructed me to let this newly hired former military man to fly on this, his first day on the job. It was unfair to the man because he had not yet received any orientation training to our operations. This flight was the result of that bad decision. I want to make it clear that I do not hold a low opinion of military pilots. I am fully aware that if I was put in command of an airplane in a military environment that it'd likely result in disaster because I've not been trained to operate there. I'm fairly certain that in a fighter jet I'd be the first casualty of the war, if not by my own ignorance of the operation, then at the hands of the enemy, or perhaps having been shot in the back of the head by my own backseater.>

Anyway, this Army C-12 driver was taught methods that his background required, including shoving those props up on final approach.
It apparently made no difference to him if the operational environment was changed.
SAT approach told us to reduce speed to follow traffic, (were doing 220 kts and he was to reduce to 180) so he put out appch flaps.....35 MILES from the final appch fix. (He had been taught to extend flaps when approaching an airport below 190 kts. He made no distinction to the fact we were not yet anywhere near the pattern.) When he intercepted the final at 20 miles, he shoved the props UP to max RPM. When the tower next asked him to increase speed (due to excessive slow down with flaps out and props at fine pitch)...his method was to increase THROTTLE...while leaving all that drag from flaps and props where they were. He refused to return to a previous configuration, so we screamed along at high RPM and high power with flaps out for 20 miles.
When we lined up for that 10,000 ft runway (we were parking at the far end) he reduced speed to cross the threshold at 105 kts in gusty wind. I was uncomfortable and told him so, but it made no difference. He had gear down, full flaps, high power, fine pitch props, and 105 kts all the way to touchdown and immediately on touchdown he slammed it into reverse-thrust and hit the brakes and made the first turn-off.
We then had to taxi nearly two miles to the ramp at the other end of the field.

It was the dumb'em down flying technique.

He did well after I demonstrated on subsequent flights that to slow down one only had to reduce power, and that keeping the airplane CLEAN with flaps up saved noise and fuel and made a more confortable flight for pax.

So much for what almost everybody has been taught by dumb'em down instruction. again...IMO.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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jrenwick
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Re: leaning procedures and EGT

Post by jrenwick »

I don't want to hijack the thread, George, and I do believe you're right in all respects about leaning. I've heard Darryl Bolduc say, if I remember right, that there's no way you can harm these old Continental engines by over-leaning (assuming CHTs don't become excessive).

I always apply carb heat before reducing power on the downwind. I've sometimes closed it on short final in preparation for a possible go-around. It seems like a good idea, except that I don't need one more thing to have to think about at that critical point in the approach, and the 170 and Swift panels are set up nicely for closing carb heat with your thumb as you push the throttle open with the palm of your hand.

I consider myself to be maybe not a "dummy," but at least fallible most of the time, and especially when I'm flying. I'm always looking out for ways I could shoot myself in the foot, and trying to engineer ways to avoid potential mistakes. Mixture rich on downwind is just one of those mistake-avoidance things. I don't know how much harm that does to an engine at a low power setting for the brief period between downwind and landing, but it's a lot less harm than could be done by an accident during an attempted go-around.
John Renwick
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
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Ryan Smith
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Re: leaning procedures and EGT

Post by Ryan Smith »

gahorn wrote:
jrenwick wrote:Wow, George! I agree with almost everything you said, except that leaving the mixture leaned through landing is really radical, and contradicts what almost everybody has been taught. GUMPS! "Red, blue, green, runway's clean" on final, etc. I expect an instructor would hear from the examiner about that if a student did it during a check-ride. It's a set-up to have the engine stumble at the worst possible moment when you forget to shove all three controls forward, at a time when you least want to be debugging a problem. Sorry, I just can't go along with that!
Yes, I know what you mean. But the masses are taught the "dumb 'em down" methods" and examiners feel the need to "teach" (even tho' that's not their job.)

Example: Newbies are taught to pull carb heat before power reduction in the pattern and leave it there until after touch down.

But... what about the go-around? Oh... now they're supposed to remember to turn OFF the carb heat.
What's different about remembering to push rich on the mixture on a go around?
And what's wrong with simply "clearing" the carb of ice with application of carb heat...check the tach...see no ice accumulated...then turning carb heat OFF for the remainder of the approach/landing? (and guess what?...no need to remember to turn it off in case of go-around.)

It's a matter of "dumbing down"... OR..... teaching the reasons things are done and then... simply requiring excellence in piloting skills.
If you want to teach dummies to fly...then keep pulling carb heat incessantly/forever in the pattern and running the mixture RICH simultaneously...and see what THAT does to spark plugs and valves.

I'd like to think my students are smarter and teachable and more capable than that.

Anyway...the question of the thread was for recommendations on leaning and avoiding stuck valves and that's the way to do it, IMO.

(And, by the way, ...if you want everybody to do "what almost everybody has been taught" ....then you can also forget about Deakin and Busch too.)

"What almost everybody has been taught"...also addresses constant speed props (among a host of other things.) Everybody has been taught to shove the props up to fine pitch before landing, presumeably in the expectation of the "Damn the Torpedos" go-around. Of course, that places unnecessary strain on engines, props as well as passengers...and creates drag when it's not needed which results in a necessary change in throttle to continue a stabilized speed.... but it does make the noise level sound like something important is about to happen so that pax can get concerned.

I don't know of ANY real professional that does that, they leave the props where they were during descent and all thru the touchdown, only moving them to fine pitch after touchdown or in the event of go-around.

So much for what almost everybody has been taught by dumb'em down instruction. again...IMO.
Interesting.

I spend quite a bit of time lurking on BeechTalk, where John Deakin frequents, as well as listen in on many of the seminars that Mike Busch hosts with the EAA. I enjoy soaking up the knowledge they willingly share, but it is good to keep an apples-to-apples comparison in perspective. A Baron, a 170 is not. My wheels spin so fast that they often times fly off the axles, so it's good to be grounded by reality. :lol:

That said, when I was flying, I was taught to fully enrich the mixture prior to pattern entry, as well as keep carb heat applied after the first power reduction on downwind. I was young at the time, and simply took my instructors' word as gospel as I didn't have any access to information to rebut their stance. Running an engine over square was a cardinal sin, but I was shocked to read Busch's commentary on the topic where he insisted that running over square was actually better for your engine. I recall several years ago before I moved to Illinois, someone out at Air Harbor talking about an article that Deakin wrote entitled "Manifold Pressure Sucks". That was pretty enlightening, if a little hard to wrap my head around at the time because it completely negated everything that I had ever been taught about engines.

On a final note, the amount of time logged in aircraft with a constant speed propeller is less than ten hours total. When John Barrett so graciously allowed me to fly his 170 with him last year, once we were established on the approach back into the airport, I slowly started to turn the propeller back to fine pitch. John told me to leave it where it was, since we were in the proper configuration on a stabilized approach. Going to fine pitch on the propeller would cause us to basically lose airspeed and drop out of the air. It made sense, and stuck with me. Prior to flying John's airplane, the last airplane I flew was a Maule MX7-180C, which has a Hartzell constant-speed propeller. My instructor would have me go to full fine pitch in the pattern...so when I flew with John, I was only mirroring what I was taught.

Final closing thought...had I known better, I probably would have operated the engine in the 170 as Arash and George have described. My dad lost his marbles when I was back-taxiing at a jogging speed to clear the runway once when there were other aircraft in the pattern one evening. He probably would have thrown me out of the airplane if he saw that I didn't leave the carb heat on or go to full rich on the mixture in the middle of the day in July.

Ovid Bonham (I believe) wrote a pretty good article on leaning operations in 170s that made its way to the 170 book. I'm about due for a new copy...I've worn mine out after only having it a year. I'm not sure what will happen to it once I finally get an airplane. 8O
n3833v
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Re: leaning procedures and EGT

Post by n3833v »

Here is a Forum at Oshkosh. This is the only time listed.
Jul28 Leaning 101 Fundamentals
Monday, July 28
0830 - 0945 (8:30 - 9:45)Forum 7
(map)Presented by Mike Busch

John
John Hess
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Director 2005-2014, TIC170A
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LBPilot82
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Re: leaning procedures and EGT

Post by LBPilot82 »

I have an EGT probe on cyl #2 only. Typical temp at cruise (7500ft or so) is somewhere around 1350. Peak is typically around 1380. Fuel flow is usually 7.8-8.0 at 2550RPM. Everyone has their own tried and true method for leaning and mixture control. While I can't endorse George's method of not enrichening prior to touchdown, this would ensure a lean mixture during the descend/landing. If you forget to enrichen prior to a go-around, however, you may be in for a quiet surprise. My method is to fly the 170 as if it had a turbo charger and try to minimize throttle/mixture movements during the descent. If I time it right, I will usually hold about a 200-300fpm descent all the way down and keep the power near cruise RPM until turning final. Keeping a higher RPM through the descent helps keep temps up as well as gives you a good ground speed during descent. This means starting the descent well before you may be used to. I almost never use full rich since full power doesn't need it. Each plane is different but I know that about 1 inch out will give me about 10GPM and 1300EGT at full power at my field elevation (2200ft). I heavily lean on the ground (to the point where I can't get much over 1000 RPM) and I've never had a fouled plug or valve (always running 100LL).

Just my 2 cents.
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Re: leaning procedures and EGT

Post by C170U2 »

Are you folks always leaning or just when you get above a certain altitude? I've been using 3,000'. For short hops when I am just playing in the weeds or hitting the pattern I haven't been leaning.
counsellj
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Re: leaning procedures and EGT

Post by counsellj »

I always lean.
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GAHorn
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Re: leaning procedures and EGT

Post by GAHorn »

I do the same, as soon as I am out of the pattern I pull the mixture out to approx. where I know it should be.
I have an ACS mixture control, which is a "ratchet" type control. It has small ribs on the operating rod just beneath the knob, which begin to appear when the knob is pulled about an inch from the panel. I know from previous experience with this SN where the "sweet spot" is.
I do not aggressively lean during the climb, however. It just isn't full-rich. (I have no sophisticated instrumentation, only a tach and a CHT, and perhaps this technique may be a good argument in favor of an engine monitor, but no evidence of harsh treatment has appeared and I'd rather spend it on avgas or save for ADS-B.)

<I realize now that I'd left out an important comment in my previous post (above) and have inserted a blue comment I hope will not be missed.>
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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cessna170bdriver
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Re: leaning procedures and EGT

Post by cessna170bdriver »

I'm based at 4000' MSL, so I rarely have the red knob pushed all the way in. My UBG-16 from EI with 6-cylinder CHT/EGT may not be necessary, but I do instrumentation for a living, and kind of like knowing details about what's going on up front. I have found that leaning to peak EGT on the hottest cylinder then richening about 25 or so puts me right in the same spot that the old lean-to-rough/richen-to-smooth procedure puts me, right around 1425* F on the hottest EGT. Now I just know how far out to pull the red knob to get that number. Fuel usage (calculated at tank filling) is about 8.5 or so at 2600 cruise, and about 7.5 at 2450.

I don't think an actual EGT number means very much from one airplane to the other, especially with systems installed in the field. Just a small change in location can mean a big difference in measured temperature. My probes are as close as I could get them to 2 inches below the flange.

I used to have a lot of valve sticking problems, but they all went away when I switched to a steady diet of 100LL. I haven't had to clean plugs between annuals for nearly 20 years.
Miles

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