Good topic - I'm on the side where I think it's quite important to lean the whole time during taxi. As photofly posted, what if you're waiting in line for 20 mins for takeoff? After you get the takeoff clearance is not a fun time to realize the plugs are all fouled!
One cool thing I've seen on a plane I was flying for some time that had a 540 lycoming was that in the runup checklist, you had to go to full throttle and lean to a specific fuel flow depending on the pressure altitude on the ground.
How far do you lean while on the ground before takeoff
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Re: How far do you lean while on the ground before takeoff
I do the same as a lot of others said; lean during taxi and enrich prior to takeoff. As for forgetting, I think it's no different than the way I would do it in a light twin vs a 172. I was always taught with power application for takeoff, go right to left. So for takeoff in a light twin, I verify mixtures full fwd, props full fwd, and then apply throttle. I do the same if it's a 182 or 172 with only mixture and throttle. Then I never forget.
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Cat Driver
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Re: How far do you lean while on the ground before takeoff
Well if the plugs fouled bad enough to cause a power loss you could always reject the take off.After you get the takeoff clearance is not a fun time to realize the plugs are all fouled!
I have been trying to remember if I ever had a situation where the plugs became fouled during ground operations and so far I can not remember it ever happening......not that it can not of course, it just never happened to me as far as I can recall.
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
Re: How far do you lean while on the ground before takeoff
That’ll be because you always leaned the mixture on the ground 
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
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Cat Driver
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Re: How far do you lean while on the ground before takeoff
Like everything in aviation leaning the fuel mixture varies from airplane to airplane, some of the little four bangers tend to be more prone to plug fowling than others and of course the altitude at which you are operating is also a factor.That’ll be because you always leaned the mixture on the ground
Operating out of a sea level airport is less problem mixture wise than say Leadville Colorado at ten thousand feet ASL.
When operating any aircraft the engine manufacturer will determine how and when to lean.
I have over ten thousand hours operating big radial piston engines and "" always "" started, taxied, took off and climbed with them in Auto Rich and plug fowling was never a problem.
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
Re: How far do you lean while on the ground before takeoff
Is plug fowling where a chicken pops out of the exhaust
?DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
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Cat Driver
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Re: How far do you lean while on the ground before takeoff
F.O. to Capt.
Which came first, the chicken or the egg?
Capt.
Neither, it was the Rooster.
Which came first, the chicken or the egg?
Capt.
Neither, it was the Rooster.
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
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Cat Driver
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Re: How far do you lean while on the ground before takeoff
Capt.
Why did the pervert cross the road?
F.O.
To get on the other side?
Capt.
No, he was stuck in his chicken.
Why did the pervert cross the road?
F.O.
To get on the other side?
Capt.
No, he was stuck in his chicken.
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
Re: How far do you lean while on the ground before takeoff
... or it's a genuinely-experienced pilot who's flown enough hours to know that safety comes from multiple layers of safeguards rather than a fantasy of personal infallibility.
@CYRO
Re: How far do you lean while on the ground before takeoff
Normally-aspirated piston engines (at least) aren't capable of getting anywhere remotely close to CHT limits at idle/taxi power on the ground, regardless of where you set the mixture. You need to be at cruise power before you can generate enough heat to do them damage.FL007 wrote: ↑Fri Jul 06, 2018 7:25 am I always preferred to have a cooler cylinder head temp on takeoff. The last thing I'd want to worry about on takeoff is an engine that is at its thermal limit (considering age of engine, students beating it up, etc.), and that thermal stress is even more pronounced at colder temperatures where shock cooling is a factor. To each their own though!
OTOH, an overly-rich mixture on the ground will generate a lot more carbon monoxide (hopefully not making its way into the cabin), leave significant lead deposits on your plugs, and cost you a couple of loonies more in fuel.
@CYRO
Re: How far do you lean while on the ground before takeoff
I have a normally aspirated engine. If it's 25°C outside it will hit 400°F in under 10 minutes at idle.
Re: How far do you lean while on the ground before takeoff
What do you see at 75% cruise?
@CYRO
Re: How far do you lean while on the ground before takeoff
65% is 320-360. I don't think 75% is much higher.
Re: How far do you lean while on the ground before takeoff
What’s the aircraft type? Ground temperatures are going to be heavily influenced by cowl and baffle design etc.
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
Re: How far do you lean while on the ground before takeoff
On the ground, do you find that leaning has much of an impact on the idling temperature? In theory, the lowest CHTs should be when the mixture is extremely lean (just above cut-off); the next lowest should be full rich, and the hottest CHTs should be when it's only moderately leaned (e.g. 50–100°F rich of peak EGT). You should still have lower CHTs taxiing (very) lean than taxiing full rich, but as others rightly pointed out, a lot would depend on your baffling, cowl, whether you're facing into the wind, etc.
@CYRO
Re: How far do you lean while on the ground before takeoff
If you get very high cht while idling on the ground where the engine is generating maybe 5% of rated power I would be much more inclined to look at airflow issues than fiddle about with the mixture.
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
Re: How far do you lean while on the ground before takeoff
Exactly. I have no idea what effect using a brutally lean mixture setting on the ground is having on my CHTs because they are climbing rapidly anyway.
Photofly the aircraft is a BD4. Same engine and about 1/3 the frontal cooling air intake area as a 172. Very good temps full power climb and cruise but on a hot day on the ground the options are to takeoff or shutdown. I flew a new RV6 last year with the same engine and the same problem but it also runs very hot in the air so a much bigger problem, especially considering it was 400 pounds lighter and 20 knots faster than mine.
Photofly the aircraft is a BD4. Same engine and about 1/3 the frontal cooling air intake area as a 172. Very good temps full power climb and cruise but on a hot day on the ground the options are to takeoff or shutdown. I flew a new RV6 last year with the same engine and the same problem but it also runs very hot in the air so a much bigger problem, especially considering it was 400 pounds lighter and 20 knots faster than mine.
Re: How far do you lean while on the ground before takeoff
Sounds rough. I don't have a CHT gauge on my Warrior II -- the O320-D3G is a simple, nearly bullet-proof engine, so I just make sure I cross-check the mechanical tach with an optical tach from time to time to make sure I'm not cruising over 75%. I also fly LOP-WOT, which the engine loves (given maintenance reports over the past past 15 years).ahramin wrote: ↑Thu Jul 26, 2018 10:16 am Exactly. I have no idea what effect using a brutally lean mixture setting on the ground is having on my CHTs because they are climbing rapidly anyway.
Photofly the aircraft is a BD4. Same engine and about 1/3 the frontal cooling air intake area as a 172. Very good temps full power climb and cruise but on a hot day on the ground the options are to takeoff or shutdown. I flew a new RV6 last year with the same engine and the same problem but it also runs very hot in the air so a much bigger problem, especially considering it was 400 pounds lighter and 20 knots faster than mine.
I do have an EGT gauge. It doesn't show absolute temperature, but it indicates far lower on the ground (the needle barely budges) than it does in cruise (typically 11:00 or 12:00 position), so CHTs should be proportionally lower. When I taxi over to the pumps without flying, my engine cranks more like a cold start than a hot start, also suggesting that it isn't heating up much on the ground.
@CYRO
Re: How far do you lean while on the ground before takeoff
I usually lean over and close the door, then Giv’er!
But seriously i got a bit of advice from another Continental O-300 owner was to lean on the ground extensively and if holding short run er up to 1700 like I’m doing a mag check. As long as there is nobody behind me that is what i usually do. Keeps my champions winning.
But seriously i got a bit of advice from another Continental O-300 owner was to lean on the ground extensively and if holding short run er up to 1700 like I’m doing a mag check. As long as there is nobody behind me that is what i usually do. Keeps my champions winning.
