Do you lean for take off ?

[SCCutler]

See what your sea level EGT at full power is, lean to match.

 

[bflynn]

Yep. Is it o.k.?

You're the pilot, you decide if it's ok. Mine says "mixture set".

Of course, if you don't like what your checklist says, you're absolutely free to modify it however you like. Nobody will care. Probably.

 

[poadeleted20]

That's the thing. It says full rich on take off in all applications...

Do you have either a pressure carb or a turbocharger? What aircraft/engine?

In any event (the exceptions above notwithstanding), the big issue with leaning for takeoff is the potential for overtemping the cylinders. The manufacturers' recommendations are generally pretty conservative, and if you have all-cylinder EGT/CHT monitoring, it's pretty easy to lean to the "normal" takeoff EGT you'd see at sea level/standard day, and then just make sure the CHT's stay in the acceptable range. But without that instrumentation, it's best to stick with what it says in the POH, although I've never seen a POH for a normally aspirated engine which said to use full rich in all conditions, and didn't include leaning recommendations for DA's above 3500-5000 or so.

 

[BigBadLou]

The checklist and POH should say "lean for best power" which would include leaning for the given DA.
If the checklist says or if an instructor teaches "mixture full rich", that is incorrect but usually good enough for most sea-level airports. Every student should experience (under CFI's supervision) at least one flight with high DA. Doesn't have to be Colorado, high DA comes from higher-than-ISA temperatures even at sea level. 110 degrees (F) in Texas will put you in 4k DA easily.

 

[coloradobluesky]

You certainly need to lean if you aren't making full rpms. That is one test. If leaning increases rpms, then you need to lean for max power for takeoff. I recommend leaning for max rpms, then enrichen slightly, unless above 7000' density altitude, then lean for max rpms. This is for most non turbo charged Lycomings and Continentals.

 

[poadeleted20]

You certainly need to lean if you aren't making full rpms. That is one test. If leaning increases rpms, then you need to lean for max power for takeoff. I recommend leaning for max rpms, then enrichen slightly, unless above 7000' density altitude, then lean for max rpms. This is for most non turbo charged Lycomings and Continentals.

...with fixed pitch props, and it's still not consistent with any FAA or manufacturers' recommendations of which I am aware, so I'm wondering where you got these unusual procedures. I know of no manufacturer who recommends leaning for max power (i.e., peak RPM with a f/p prop) below about 3500 DA, and none who says at those middle DA"s (3500/5000-7000) to lean to peak RPM and then enrich so as reduce RPM's again.

And, of course, what you do with a c/s prop is quite different. Again, read the book on your airplane/engine and do what it says unless you have really good information which says there's a better choice.

 

[midlifeflyer]

...with fixed pitch props, and it's still not consistent with any FAA or manufacturers' recommendations of which I am aware, so I'm wondering where you got these unusual procedures. I know of no manufacturer who recommends leaning for max power (i.e., peak RPM with a f/p prop) below about 3500 DA, and none who says at those middle DA"s (3500/5000-7000) to lean to peak RPM and then enrich so as reduce RPM's again.

Other than the 7,000 altitude difference, which over 20 years flying in Colorado I never heard if, leaning at run-up power for max RPM and then enrichening slightly is pretty much SOP in the Rockies and it works just as well for constant speed props as fixed pitch props. Even with a fuel flow meter, it's amazing how close it gets to the recommended target for that D-Alt (and yes, in that case, one may need to tweak slightly on the roll).

As always there are exceptions, but of the 30-40 or so types of singles I've flown, I can count the exceptions on part of one hand:
1. Turbocharged aircraft - move to full rich for takeoff
2. Aircraft with automatic mixture controls
Aircraft without a mixture control
3. Leadville when it's above 70°F (actually it works there also, but I like to go briefly to full power afterwards to check and tweak when the D-Alt is that high)

 

[Ted]

You did the right thing leaning for takeoff at 4,000 MSL. That is normal and what you should do.

 

[BGF_Yankee]

3. Leadville when it's above 70°F (actually it works there also, but I like to go briefly to full power afterwards to check and tweak when the D-Alt is that high)

I barely need one hand to count the number of times I saw 70° in Leadville! -30° is another story altogether though...I might need both hands and feet!

 

[Stewartb]

Departing KHRX this morning, I did my runup and leaned it to clear the right mag because it was running a little rough. The engine sounded so good I just left it leaned out and took off. Keep in mind, I normally operate from 300 ASL.

Elevation there is ~4000. It was cold so DA wasn't much a factor, but the engine liked it better leaned out.

Did I commit a no-no?

I know you're a warm weather flyer so how cold is cold to you? You might ought to insulate your balance tube if you expect to fly in the cold more often. That alone may explain your engine running like "puke".

 

[CharlieTango]

The most common type of crash around here is from 'sea level pilots' doing full rich take offs. Leaning for best power at high altitude airports is the only way to access all available power.

 

[poadeleted20]

Other than the 7,000 altitude difference, which over 20 years flying in Colorado I never heard if, leaning at run-up power for max RPM and then enrichening slightly is pretty much SOP in the Rockies and it works just as well for constant speed props as fixed pitch props.

I wouldn't like to see the RPM with a c/s prop change at full throttle as I leaned from full rich to best power. If it does, I'm taking it back to the shop to have the propulsion system checked. I can't imagine how high the DA would have to be before full rich would cause the power to be reduced so much that the blades hit the low-pitch stops -- probably well into Class A airspace, I should think.

 

[midlifeflyer]

I wouldn't like to see the RPM with a c/s prop change at full throttle as I leaned from full rich to best power.

Me neither. Read what I wrote.

 

[PPC1052]

Of course you lean for TO if elevation and/or conditions warrant it, "full rich" for to/ldg is not something a CFI with NO experince teaches.

It depends on your elevation. I killed the engine landing on my long solo XC as a student when I forgot to add richness before landing after I had leaned it out for cruise. The engine kept getting quieter and quieter as I got lower and lower. It finally completely died as I was rolling out.

Of course, we are at about 800 feet elevation here in this area.

 

[txflyer]

I know you're a warm weather flyer so how cold is cold to you? You might ought to insulate your balance tube if you expect to fly in the cold more often. That alone may explain your engine running like "puke".

It was about 28 farenheit. I pulled out my POH and all it says for take off is:

• Mixture -- Full rich (unless engine is rough)

And that's how it is worded exactly. Good stuff guys. I'm learning a lot.

 

[poadeleted20]

Me neither. Read what I wrote.

I did. Let me quote it back at you and see if you see what you said even if you didn't think you said it.

.,.leaning at run-up power for max RPM and then enrichening slightly is pretty much SOP in the Rockies and it works just as well for constant speed props as fixed pitch props.

With a c/s prop, you have to use something other than max RPM to tell when you've leaned to max power. Generally with c/s props, the POH's tell you to lean to a specific fuel flow based on DA.

Beyond that, Lycoming says, "For 5,000 feet density altitude and above, or high ambient temperatures, roughness or reduction of power may occur at full rich mixture. The mixture may be adjusted to obtain smooth engine operation. ... For direct-drive and for normally aspirated engines with a prop governor, but without fuel flow or EGT, set throttle at full power and lean mixture at maximum RPM with smooth operation of the engine as a deciding factor." They also say, "If manual leaning of the mixture is permitted at takeoff, climb power or high-performance cruise, it will be specified in the POH/AFM and will list required ranges for fuel flow, power settings and temperature limitations." And their last word is, "The Pilot’s Operating Handbook for the aircraft in which the engines are installed should be the final authority as to how the engine should be operated."

 

[txflyer]

I did. Let me quote it back at you and see if you see what you said even if you didn't think you said it.

With a c/s prop, you have to use something other than max RPM to tell when you've leaned to max power. Generally with c/s props, the POH's tell you to lean to a specific fuel flow based on DA.

Beyond that, Lycoming says, "For 5,000 feet density altitude and above, or high ambient temperatures, roughness or reduction of power may occur at full rich mixture. The mixture may be adjusted to obtain smooth engine operation. ... For direct-drive and for normally aspirated engines with a prop governor, but without fuel flow or EGT, set throttle at full power and lean mixture at maximum RPM with smooth operation of the engine as a deciding factor." They also say, "If manual leaning of the mixture is permitted at takeoff, climb power or high-performance cruise, it will be specified in the POH/AFM and will list required ranges for fuel flow, power settings and temperature limitations." And their last word is, "The Pilot’s Operating Handbook for the aircraft in which the engines are installed should be the final authority as to how the engine should be operated."

Good info Ron, but I can barely hold mine with the brakes on a full power run up. There would be no way on the snow/ice covered strip I was on the other day.

Besides, I like my MT prop and clean rubber leading edge strips on my horizontal stabilizer.

I have no engine analyzer, no fuel flow gauge, so how about I just lean it until it sounds good on a normal run-up and call it good? :wink2:

 

[Stewartb]

Your DA that day was around 3000'. Leaning probably helped clear up the roughness but it likely would have cleared with a good, lean run-up and stayed cleared. Cold temps do little tricks to engines. A guy not used to cold ops wouldn't know that. All in all you made it back so the result was acceptable. Live and learn.

I'm curious. How was the airplane stored overnight? How was it preheated? Did you prime it to start? How many strokes?

 

[poadeleted20]

Good info Ron, but I can barely hold mine with the brakes on a full power run up. There would be no way on the snow/ice covered strip I was on the other day.

In that case, you're going to have to do it on the roll.

I have no engine analyzer, no fuel flow gauge, so how about I just lean it until it sounds good on a normal run-up and call it good? :wink2:

Too much changes in the carburetor between run-up throttle setting and full throttle. If I couldn't make full throttle due to skidding, I'd probably adjust it on run-up, then be ready to re-adjust it on the takeoff roll using either RPM (fixed pitch) or fuel flow or just by ear. That's going to be something of a distraction from controlling the aircraft, so watch yourself doing it.

 

[denverpilot]

I'm so used to leaning during run up that flying with Jesse in Lincoln a couple weeks ago I was really lean (as always for taxi) and when I went to run up I twisted it in a couple of turns as if I would add power for the run up and then lean, and then realized I was near sea level.

"Guess that knob needs to be all the way forward down here..." I said, as he chuckled...

 

[txflyer]

Your DA that day was around 3000'. Leaning probably helped clear up the roughness but it likely would have cleared with a good, lean run-up and stayed cleared. Cold temps do little tricks to engines. A guy not used to cold ops wouldn't know that. All in all you made it back so the result was acceptable. Live and learn.

I'm curious. How was the airplane stored overnight? How was it preheated? Did you prime it to start? How many strokes?

Plane was stored in a T-hangar with no door. Cowl plugs were in for birds. Cowl flaps closed.

No pre-heat. But it did have the sun on it for a while. I turned the prop by hand one revolution before getting in.

I primed it four strokes and cranked. No joy. Primed it two more and it fired and died. Primed it two more .. fire and die. Primed it two more and it caught so I pumped the throttle ( I know, that's bad) and finally kept it running that time.

 

[Pilawt]

I was really lean (as always for taxi)

Always lean on taxi ...

 

[Sac Arrow]

It was about 28 farenheit. I pulled out my POH and all it says for take off is:

• Mixture -- Full rich (unless engine is rough)

And that's how it is worded exactly. Good stuff guys. I'm learning a lot.

What are you flying?

Do you have some sort of altitude compensating carburetor?

 

[Stewartb]

So you gave it ten strokes of raw fuel prime and followed it with pumping the throttle, which shot raw fuel into the very cold induction tubes. You definitely needed to clear your cylinders before take-off. In your situation I hope you gave the engine plenty of time to warm up. Were oil and cylinder temps in the green prior to taxiing? Once I saw oil pressure I'd run the idle to about 1500 and I'd lean it til it almost quit and push the knob back in just a smidge. Once warmed I'd do a rolling run-up if it was slick. I wouldn't expect any need to lean for a 3000' DA take-off. But like I've said, my carb is on the lean side. Maybe yours is on the fat side. Do what you need to do.

 

[midlifeflyer]

I did. Let me quote it back at you and see if you see what you said even if you didn't think you said it.

I'm pretty sure what I said. To quote myself:

leaning at run-up power for max RPM and then enrichening slightly is pretty much SOP in the Rockies and it works just as well for constant speed props as fixed pitch props.

The operative phrase is
"at run-up power for max RPM" not "at full power for max RPM."

You mean, you don't get RPM changes during, say, the application of carb heat or mag checks, during your run-up of a normally aspirated piston with a constant speed prop? I do and have for the 20+ years I've been flying with constant speed props. And also when leaning. Both at sea level and at high density altitudes.

 

[Stewartb]

Instead of arguing..... why not school us on the proper procedure to lean for best power for a high DA take-off and while you're at it, tell us what your definition is for high DA?

 

[MAKG1]

High DA is defined in your POH. Usually 3000-5000 DA. In some airplanes (Cessna), it IS possible to have high DA at sea level on a particularly unpleasant day. On a turbonormalized or turbocharged aircraft, high DA is considerably higher.

I prefer a full power run-up when feasible as there is a lot less guessing involved. Even using lean roll-off, though an EGT gauge or engine analyzer is better. Without those, I'll usually defer to the fuel flow placards or tables in the POH, but if there is also no fuel flow gauge, lean roll off may be all that is available (and it works better at run up power).

 

[coloradobluesky]

With a Constant Speed prop, a lot of POH's specify runup at 1800 or 1900 rpm. This is such low power that the prop is full fine pitch. You can find peak by leaning to roughness and then enrichening just until peak rpm (for that throttle setting). Then enrichen more if you want rich of peak. So its not acting like a constant speed prop, it acts like a fixed pitch prop, which is what constant speed props do at low power settings like this.

The reason you see 5000' called out as where to start leaning is because of this. At sea level the engine gets 90% of rated power (due to the muffler and the air filter being installed). At 5000' you lose 15% of sea level power which puts you down to about 75% power (if that). You wont get detonation if leaned to peak at 75% power and below. Now to be conservative, they drop it to 65% which is why you run rich of peak by turning the knob in 3 half turns at 5000'.

Altitude is continuous. If you want to "fine tune" your procedures. Richen 4 half turns at 4000', 5 half turns at 5000' etc. And as you go up, 2 half turns at 6000', one half turn at 7000'. Above 7000', set it for full lean. The reason for this is to get full power and not be way overly rich at lower altitudes. At above 7000' you need all the power you can get and its impossible to get into detonation. Compression ratios stay the same at all altitudes, but absolute compression goes down because you are starting with less air. Lower compression, no detonation concerns. Lean to max power.

There is one other consideration. Lets say you are doing the full rich below 5000' thing and you are wondering if you should at say 4500' airport. Set the lean to full rich, do a full power runup, and lean. If you get more power when leaned that is an indication that you should consider leaning at 4500', but perhaps not quite as much as at 5000'. You want to be at full power, but not into detonation. Best to be rich of peak on takeoff and climbout. It is the portion of the flight where you will be a max power and closest to detonation. Best to err on the rich side, but not so much as to take away too much power. These altitudes should be density altitudes BTW.

 

[midlifeflyer]

Instead of arguing..... why not school us on the proper procedure to lean for best power for a high DA take-off and while you're at it, tell us what your definition is for high DA?

Sure.

My definition? Well, until 2012 I lived for 20 years in Colorado, flying and, since 1999, giving flight instruction on both the flatlands (~6,000' msl) and public mountain airports (up to 9,934 msl in Leadville). But really, anything above 1,000' D-Alt is enough for consideration, although, the typical POH guideline of 3,000 or 5,000 tells me that purity is not a requirement, so there's no need to use a micrometer to measure a tent (see use of the term "ballpark" below).

The procedure I used and, AFAIK, was in general use in Colorado, for normally-aspirated pistons was fairly simple:

At the runup, the mixture is enriched (from its taxi setting). With some experience, one gets to ballpark how much, but since it won't be that long, close to or even full rich is OK.

The engine is then set to it's recommended runup power setting (bold for Ron). Runup power is used for all the reasons already mentioned about not using full power, such as the braking power of more powerful aircraft being insufficient to hold the airplane.

While at the recommended runup power Before the other system checks (carb heat, mag checks, etc), the engine is leaned by moving the mixture control slowly from its full to lean position. As the mixture is leaned, watch RPM. RPM will increase, reach a peak as the engine reaches is best setting at runup power and then begin to drop off. Enrichen the mixture until it reaches the peak RPM observed on the way down.

That will give the best setting, but only at run-up power.

The procedure continues (still at runup power and before the other runup system checks) after than is to enrichen the mixture to ballpark for fuel and cooling needs at full power. Typical for mixture with a vernier control is 3 half turns of the vernier; for non-vernier controls, about 1/4".

There are, of course exceptions (in addition to those I mentioned earlier). For example, the Cutlass usually requires more than those 3 half turns (you learn that pretty quickly). So it may require a minor tweak once taking the runway (or if you choose, briefly going to full power after the runup is complete), which is why I refer to it as a ballpark setting.

As I said earlier, the procedure works fine in both constant speed and fixed pitch props, including aircraft with target fuel flows based on altitude.

Or at least in the normally-aspirated single-engine Cessnas, Pipers, Mooneys, Bonanzas, etc I've flown other than the exceptions I mentioned earlier.

 

[midlifeflyer]

With a Constant Speed prop, a lot of POH's specify runup at 1800 or 1900 rpm. This is such low power that the prop is full fine pitch. Any added power (like when you lean it and get say 1950rpm) the additional power makes the prop rpm higher. So its not acting like a constant speed prop, it acts like a fixed pitch prop, which is what constant speed props do at low power settings like this.

Exactly. Ron seems to be missing that part.

 

[Stewartb]

So the OP describes a rough condition at 3000' DA on a 28* morning after cold starting with 10 shots of primer and a follow-up of throttle pumping. Do you think the issue was that he needed to lean it for best power at take-off? More likely he needed to blow lots of residual fuel out of the intake and cylinders? What do you guys think?

 

[midlifeflyer]

So the OP describes a rough condition at 3000' DA on a 28* morning after cold starting with 10 shots of primer and a follow-up of throttle pumping. Do you think the issue was that he needed to lean it for best power at take-off? More likely he needed to blow lots of residual fuel out of the intake and cylinders? What do you guys think?

Could be a number of things. As I read the OP it said, \

Departing KHRX this morning, I did my runup and leaned it to clear the right mag because it was running a little rough. The engine sounded so good I just left it leaned out and took off.

If the DA was 3,000' (28° at 3,000 DA is still 3,000 DA), leaning for takeoff would IMO not be a no-no (txflyer's question) unless there was a limitation against it in his manual. I know the "POH" mantra but the reality is that older manuals (and even some new ones) are written from a sea level perspective. I flew a 1958 Comanche for a number of years and it's original manual says simple "Mixture Rich" for takeoff and landing. It would not have worked too well.

Most likely culprit to me is the most common cause of what he described - a rough running right mag - due to the mixture being too rich for taxi and a simple buildup that responds to engine leaning. That happens even at low altitudes. Funny - I flew with someone as my safety pilot the other day (~250 msl; DA not a factor) and he was expecting me to do a "mag burn" when we got to the runup. Since I leaned for taxi, it wasn't necessary and the mag check was within normal parameters.

Other alternatives? Your guess is as good as mine and might even be better.

 

[poadeleted20]

I'm pretty sure what I said. To quote myself:


The operative phrase is
"at run-up power for max RPM" not "at full power for max RPM."

You mean, you don't get RPM changes during, say, the application of carb heat or mag checks, during your run-up of a normally aspirated piston with a constant speed prop? I do and have for the 20+ years I've been flying with constant speed props. And also when leaning. Both at sea level and at high density altitudes.

My misreading. However, leaning at run-up RPM not provide a real good set-up since a lot changes between run-up RPM and full throttle, and I don't know of any POH or engine manufacturer which suggests doing it that way.

 

[poadeleted20]

Instead of arguing..... why not school us on the proper procedure to lean for best power for a high DA take-off and while you're at it, tell us what your definition is for high DA?

It's what I said earlier.

For fixed-pitch props, set full throttle and lean to peak RPM.

For c/s props, follow the POH, which usually has a target fuel flow for each DA (often printed right on the fuel flow gauge). If you have nothing else, do what the engine manufacturer says, which for Lycoming is to set full throttle, and lean until it smooths out.

As for the definition of "high DA", it's usually stated as 5000 or above, but check your POH as I've seen some which say 3500.

 

[Stewartb]

txflyer,

The next time you find yourself in that situation try to push 3-4 shots of prime and then get back out and pull at least two full 360* revolutions of the prop by hand. Back into the plane, give it one more shot and pull the primer back out, crank it to start, and be ready to slowly feed the primer in to keep it running initially. Once it catches and smooths out the throttle will respond normally. I believe you'll find it works better than what you did and it'll have a greatly reduced potential for an induction fire. Cheers from the frozen north.

 

[Palmpilot]

I once took off with the mixture full rich when the density altitude was 3000 feet, and the engine started running rough on the upwind, whereupon I made my first ever emergency landing. Fortunately, I still had a couple hundred feet per minute of climb performance left, so I was able to continue around the pattern and land on the runway. Later, I performed the procedure for clearing fouled plugs during runup, and the engine performed normally after that. (This was in a Cessna 182Q.)

 

[midlifeflyer]

My misreading. However, leaning at run-up RPM not provide a real good set-up since a lot changes between run-up RPM and full throttle, and I don't know of any POH or engine manufacturer which suggests doing it that way.

It does not change any manufacturer's recommendations. The method I described in more detail is just an efficient shortcut to the same result and was being used by pilots in Colorado long before I moved there (it was old and standard when it was first taught to me in the summer of 1992).

 

[txflyer]

So you gave it ten strokes of raw fuel prime and followed it with pumping the throttle, which shot raw fuel into the very cold induction tubes. You definitely needed to clear your cylinders before take-off. In your situation I hope you gave the engine plenty of time to warm up. Were oil and cylinder temps in the green prior to taxiing? Once I saw oil pressure I'd run the idle to about 1500 and I'd lean it til it almost quit and push the knob back in just a smidge. Once warmed I'd do a rolling run-up if it was slick. I wouldn't expect any need to lean for a 3000' DA take-off. But like I've said, my carb is on the lean side. Maybe yours is on the fat side. Do what you need to do.

I leaned it for taxi and taxi'd out with the cowl flaps closed. I waited for oil temp and pressure to be well into the green and ran it up past 1700 a couple of times. And I leaned it hard on the run ups to clear the right mag.

Field elevation at KHRX is 3788'. Hereford and Amarillo sit on the same plain as the Grand Canyon for trivia.

I'll try your prime ... turn by hand ... crank with the primer out method next time. Thanks for the tips.

 

[denverpilot]

It's what I said earlier.

For fixed-pitch props, set full throttle and lean to peak RPM.

For c/s props, follow the POH, which usually has a target fuel flow for each DA (often printed right on the fuel flow gauge). If you have nothing else, do what the engine manufacturer says, which for Lycoming is to set full throttle, and lean until it smooths out.

As for the definition of "high DA", it's usually stated as 5000 or above, but check your POH as I've seen some which say 3500.

What fuel flow should I shoot for in my c/s equipped carb'd O-470 with no fuel flow meter? LOL

 

[denverpilot]

It does not change any manufacturer's recommendations. The method I described in more detail is just an efficient shortcut to the same result and was being used by pilots in Colorado long before I moved there (it was old and standard when it was first taught to me in the summer of 1992).

I know for a fact it works for carb'd engines because the only thing that happens between 1700 RPM and full throttle is my mixture goes richer. And only at full throttle.

Lean to peak at 1700, you're guaranteed to be rich enough to avoid detonation at full throttle above 3000 MSL.

Probably below it, too. But below 3000 the POH says to be full rich.

Can't speak for injected or other systems. Clark, for example, has a different procedure for his Frankenkota because it's a very different system than I fly.

I can confirm that the technique offered is taught at every flight school here. There's an additional technique taught to do a short run at full throttle in the REALLY high DA days and lean for peak again making sure you're really there after doing it at run up power. The assumption is that you're close with the low power setting but you want it as accurate as possible and you briefly check, if you're only going to climb out at 200-300 ft/min anyway that day. There's also the possibility that those full throttle jets aren't doing their thing properly. Etc. Might as well know before you're on the runway b

Mine isn't even making 60% of sea level power on a hot day up here anyway, so you're not going to hurt it.

And it's also not cooling very well, so sometimes you'll give up a little power for cooling. Not a ton of extra fuel, but a half twist on the mixture after clear of obstructions or up to a safe turn back altitude (your call) will make a big difference in CHT on those days, if you can afford the power loss.

On those really bad days, there also isn't a limitation on leaving the prop full forward on mine. And I've been up on a few days when I needed it. I've needed it/wanted it twice during downdraft escape maneuvers away from rising terrain to the West also. I'll take the noise and the additional thrashing to make 5% more power on days like that.