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Mixture on descent to land

prkaye

Well Known Member
When i learned flying, i was taught that we always land with the mixture full-rich. In flight training the only time i ever leaned was in cruise.
Later, I learned that one should lean aggressively during ground ups - better for the engine.
Recently, I read (Busch's book "Engines") that the only time we should have the mixture full-rich is on takeoff and initial climb. This suggests that we should be leaned to some extent on final approach and landing? What do you guys do?
 
During the let down I bump up the mixture to just get ROP (listening to the engine provides this indication). It says there until after landing, then lean to just above engine cutout for taxi.

The prop goes full RPM after the plane slows down below governor speed.

For go around all three controls are pushed full forward.

Carl
 
I follow Mike Busch's approach in general, with the caveat that I need to be mentally prepared for a go-around with mixture/prop/throttle running through your mind.

Having said that, my mixture hasn't been full rich since last August, when I departed an airport in Wisconsin.

My home field is 5670' so I'm leaned about an inch for takeoff. So, I lean to about an inch during approach in anticipation of a go-around. The GUMPS check.
 
Altitude

What adjustment is made for the altitude of the airport. A lot of our aiports are above 5K.
I haven't taken a Mountain Flying course yet. :D
Need to start flying soon. Lucy is almost done.
 
What adjustment is made for the altitude of the airport. A lot of our aiports are above 5K.
I haven't taken a Mountain Flying course yet. :D
Need to start flying soon. Lucy is almost done.

I was working on a little column about this recently, but never finished it. I was one of those pilots who lived the first four decades of my life at 1,000’ or below, so things were “full rich” for takeoff and landing. But now that I live int eh mountains, the mixture control never goes all the way in.

Now, living at 4500’, I lean a bit for takeoff, and always figure I should be leaning more, because once i get established in climb, and quickly realize I am already down around 75% power, I lean straight back to LOP, where the engine is cool, clean, and happy. Then for landing, I richer up - but only enough to get me to about 50 ROP (which is peak power) because if I need to go around, I’d want the best power!

So why don’t I use that same mixture setting for takeoff? Habit from forty years of living in the lowlands I guess….. I’d like to think I am still teachable however…so I’ll work on it…..

Paul
 
That red knob only stays forward if you're a student renting wet rate and not responsible for cleaning fouled plugs!

yeah, lean aggressively at lower power settings.
 
When I descend, if I don’t reapply power above 60 percent or so, I leave the mixture leaned from where it was at altitude. I only push it in if I plan to add power more than 60 percent or so, or to keep the engine smooth. In the event of a go around, I move the mixture in with the power, easy to do with the levers in a -4, otherwise, I land leaned.
 
If you want to fiddle with the mixture during a unexpected go around, have at it.

Feel the same. I am always fiddling with the red knob to optimize power and / or fuel burn. However, It is always full for TO and landing (applied during downwind). The fewer things that can go wrong or forgotten in the initial TO or late landing phase, the better the chances of a good outcome in my opinion. I would not be happy if the red knob was aggressively leaned and I went WOT on a go around. BUT it is just one man's opinion. Obviously I don't do that when landing or departing from higher altitude airports. I am usually 800 MSL.
 
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It’s part of my landing checklist to go full rich. I live at 800 feet and often fly at sea level. Being full rich on downwind to landing for 1 minute is not going to hurt anything. Going full power on an unexpected go around could have several bad consequences if I miss the mixture knob as I add power. I prefer to keep it simple. I do stay heavily leaned in the decent.
 
Same

I also have the prop and mixture full forward for landing (I'm basically at sea level, however). Watching Dan Gryder's YouTube channel, I've been impressed with how often accidents are caused by botched go-arounds, so I try to keep go-arounds as simple as possible.

It’s part of my landing checklist to go full rich. I live at 800 feet and often fly at sea level. Being full rich on downwind to landing for 1 minute is not going to hurt anything. Going full power on an unexpected go around could have several bad consequences if I miss the mixture knob as I add power. I prefer to keep it simple. I do stay heavily leaned in the decent.
 
Being full rich on downwind to landing for 1 minute is not going to hurt anything.....

That depends upon the elevation of the airport that you might need to go around from. In this part of the country, that's throwing away potential power that might be needed for a go-around.

Lean to the appropriate mixture for go-around power for the airport you're using.

Dave
 
One of the nice things about my throttle quadrant is that it makes it very easy to push mixture and throttle forward simultaneously. I also have my flap switch right be the throttle quadrant so my thumb hits the flap switch as i advance teh throttle.
Talking about this is making me miss flying! I've been grounded for 6 months (IRAN)... longest i've gone without flying in at least 14 years.
 
Altitude

Neither the engine nor the airframe recognize "elevation". They recognize only density altitude.
Mid day density altitudes along the Colorado are already above 4000'. Mixture should be leaned for landing at the same setting as would be used for takeoff at that density altitude.
Failure to do so will not only compromise power for a go around, in extreme cases the engine may even quit.
Descending from around 10000' in with my 0 320/carb I move the mixture toward rich just a bit incrementally as I descent. Primitive machine with no fuel flow or EGT.
 
Cab heat

Could maybe ya’ll throw carb heat in this mix? I personally have not flown in years, but seem to recall events where reducing throttle would require carb heat to keep the carb icing down. Mixture and or heat, any correlation? I may be out in left field on this. When taking flying lessons in the 70’s, central Florida, I don’t recall ever messing with mixture, except in shutting down.
 
My airfield is at 660', after the climb out I almost never go full rich. Yeah, my flight instructor taught me to go full rich and full fine downwind to prepare for a go-around, but he taught me to do a lot of other things that I now know were a simplified version of what is best. Once the engine is leaned in the cruise there is no need to richen it to run at a lower power setting in the descent or around the pattern. If a go-around is needed then I will have to enrich the mixture - the red knob (and the blue knob) is close to the throttle which makes it easy. Why burn more gas than you have to?
 
My airfield is at 660', after the climb out I almost never go full rich. Yeah, my flight instructor taught me to go full rich and full fine downwind to prepare for a go-around, but he taught me to do a lot of other things that I now know were a simplified version of what is best. Once the engine is leaned in the cruise there is no need to richen it to run at a lower power setting in the descent or around the pattern. If a go-around is needed then I will have to enrich the mixture - the red knob (and the blue knob) is close to the throttle which makes it easy. Why burn more gas than you have to?

Same rationale as why create drag when you can retract the gear. Makes perfect sense untill that fateful day when you forget. Seems like everyone who has ever landed gear up says “i lower the gear before i land; no big deal. At least until it is. Sometimes we need to build contingencies to account for our own potential fallabilities. I don’t believe i have ever met a human being that has never made a mistake or forgotten to do something they should have.
 
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Everybody and their dog is going to have their own opinion on this, including me; trouble is that as far as I know, none of them are a one size fits all approach.

Cessna says lean for taxi, full rich for takeoff unless above 3000 pressure altitude, full rich for landing. I've got more than a few hours in fuel injected Cessnas and that has always worked pretty well, so thats what I do.
 
Progressively enrich as I’m descending to the airport. I do it to slowly cool the cylinders. I don’t want to land with shock cooled or screaming hot cylinders.

My field is 247’ MSL so I’m full rich as I enter the pattern.

If I go missed, then mixture one less thing to think about.
 
Mixture

There is no one size fits all. Continental and Lycoming have different procedures. Carb vs fuel injection will behave differently. Full rich with carb Lycoming at high density altitude can result in engine failure on go around or even on final.
 
Fuel Injection

Ok one question with Bendix-style fuel injection (in my case Airflow Performance). The fuel control unit measures air density, so does this mean it keeps the same air fuel ratio regardless of altitude?
So does this mean I dont need to worry about compensating for altitude on climb or landing like I would if I have a carb?
Does this mean I dont need to worry about leaning for peak power at high altitude airports?
 
This is getting into a flat-lander vs. highlander type discussion. Our density altitudes here easily exceed 8,000' in the Summer and are half that in the winter. If you take off full rich in the Winter here you are very rich and fouling plugs. If you take off full rich in the Summer her you are flying through the power lines instead of over them. When I learned to fly here my primary instructor said screw the full rich checklist item and we instead optimized mixture during run-up. As you know the POH supplied with type certificated aircraft is written for standard sea level conditions. Period. As that is the industry standard. And the POH red knob in is just fine for flat Canada, Illinois and Virginia. Not so much Denver or Albuquerque. Here it was never full rich when we were done with the run-up mixture optimization. We also taxied from the ramp with the mixture pull out enough to make the engine stumble or get the idle mixture roll and then put about two half turns on the vernier back in (one for mama, one for the babies). If we didn't lean aggressively on taxi we would invariably have fouled plugs on run-up requiring a plug burn out and re-test.
 
Ok one question with Bendix-style fuel injection (in my case Airflow Performance). The fuel control unit measures air density, so does this mean it keeps the same air fuel ratio regardless of altitude?
So does this mean I dont need to worry about compensating for altitude on climb or landing like I would if I have a carb?
Does this mean I dont need to worry about leaning for peak power at high altitude airports?

As Jim said, you need to lean.

There is some air mass compensation according to my numbers. For example, taking off from sea level is about 17.1 GPH on my IO360 with FM200, and about 16.3 at 1400 ft. I don't know if this will continue up to very high density altitudes like 8000 ft. Might be an interesting test to see what full rich numbers look like at altitude. I lean as part of my climb check, staying ROP but bringing FF back to a more reasonable number for my climb power like 12 GPH.
 
What everybody has hinted at but nobody has stated explicitly is that it depends... on the individual airplane and the density altitude.

My RV-9A had high EGTs and that problem was solved by swapping carburetors with the new carb set on the flow bench to the rich end of the settings. For this individual airplane, even at sea level, I lean it all the time except on takeoff and last thing before landing. When I lean it, I can often hear the difference that the engine is running better.

Other airplanes I've flown worked better with different techniques.
 
Ok one question with Bendix-style fuel injection (in my case Airflow Performance). The fuel control unit measures air density, so does this mean it keeps the same air fuel ratio regardless of altitude?
So does this mean I dont need to worry about compensating for altitude on climb or landing like I would if I have a carb?
Does this mean I dont need to worry about leaning for peak power at high altitude airports?

I compensates a bit, but definately NOT completely. Go try to do an 8K' climb. You will need to progressively lean with the red knob to keep a constant AFR. It handles small to moderate changes well, but not gross ones.
 
This thread encompasses different engines, different fuel systems, different airplanes different throttle/mixture lever arrangements, different personal preferences, and different density altitudes from sea level to 8000 feet. There are a lot of right answers, but the most obvious one is "it depends".
 
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Ok one question with Bendix-style fuel injection (in my case Airflow Performance). The fuel control unit measures air density, so does this mean it keeps the same air fuel ratio regardless of altitude?
So does this mean I dont need to worry about compensating for altitude on climb or landing like I would if I have a carb?
Does this mean I dont need to worry about leaning for peak power at high altitude airports?

Second page, measured, specific to your question:

https://www.danhorton.net/Articles/Bendix-and-Beyond (1).pdf
 
That depends upon the elevation of the airport that you might need to go around from. In this part of the country, that's throwing away potential power that might be needed for a go-around.

Lean to the appropriate mixture for go-around power for the airport you're using.

Dave

I agree on that point if the airport is above 4000 density altitude.
 
If you want to fiddle with the mixture during a unexpected go around, have at it.

That's just fearmongering. The point people are making here is that you adjust your mixture for the flight conditions (density altitude) to optimize power output. On descent to land, you'd optimize for a go-around. If it happened unexpectedly, you'd already be set for it. Power up and go.
 
Enrich as I roll wings level on final. (I haven’t been IFR current in a long time, so there are very few long straight-ins. If that is the case, I go full rich at about 500 AGL.) These days, all of my landings are within 50’ of sea level, so it’s full rich. After slowing to taxi speed, lean until it stumbles with a power increase.
 
That's just fearmongering. The point people are making here is that you adjust your mixture for the flight conditions (density altitude) to optimize power output. On descent to land, you'd optimize for a go-around. If it happened unexpectedly, you'd already be set for it. Power up and go.
"Fearmongering"?
 
Second page, measured, specific to your question:

https://www.danhorton.net/Articles/Bendix-and-Beyond (1).pdf

That's a great article.

Just did some testing today - level flight at about 10800 density altitude, best power (peak EGT) was about 9.6 GPH with about 179 KTAS, and going to full rich brought me up to 14.6 GPH with speed dropping to around 172 KTAS. All at 2500 RPM.

So leaning properly saved 5 GPH and increased speed by 7 knots. I'm guessing that someone smarter than me could calculate the HP cost of these 7 knots but clearly it's going to be significant enough to encourage people taking off from a hot and high runway to lean properly.

best power (peak EGT) - See Carl's post below - I was flying at "best power", which is not peak EGT.
 
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Do you need it all?

These planes are NOT the underpowered trainer you learned on. They are high performance and almost over powered.

I have spent a career teaching new jet pilots in corporate jets (that will do 10K fpm) and my admonition is that “you don’t need it all”.

I have departed from air parks at 2 AM and used 23/23 to be quiet. At that power, I still climb out at nearly 1000 fpm.

Go arounds are not common but when done, you already have flying speed and usually some altitude. You only need a few hundred feet to re-enter the pattern. I just bring the MP to normal climb and retract the flaps.

I land (at sea level) with the prop at 2300 and mixture set where it was at 23” in descent. It is hard to imagine needing full power unless landing high and hot.
 
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So leaning properly saved 5 GPH and increased speed by 7 knots. I'm guessing that someone …..could calculate the HP cost of these 7 knots ….

In level cruise, speed varies approximately as the cube of power. So 4% speed loss equals about a 12% power loss.
 
That's a great article.

Just did some testing today - level flight at about 10800 density altitude, best power (peak EGT) was about 9.6 GPH with about 179 KTAS, and going to full rich brought me up to 14.6 GPH with speed dropping to around 172 KTAS. All at 2500 RPM.

So leaning properly saved 5 GPH and increased speed by 7 knots. I'm guessing that someone smarter than me could calculate the HP cost of these 7 knots but clearly it's going to be significant enough to encourage people taking off from a hot and high runway to lean properly.

Good stuff.

A comment about terminology: Lycoming defines the 'Best Power' mixture setting as approximately 100°F ROP, and the 'Best Economy' mixture setting as peak EGT. These are for power settings at 75% and below.

Ref: https://www.lycoming.com/content/leaning-lycoming-engines
 
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Thanks for the article

Thanks for the article. What I took away is that although the Bendix style fuel injection does not completely compensate for altitude during climb and descents, it is really close…. Much better than a carb.
 
...and carb heat.....

On the -4 and the -8, the levers are right next to each other.. you just push them up together on a go-around.

...which is why my carb heat control is right in front of the throttle and mixture: with a go-around, everything goes foreword, the last thing is my hand hitting the "T" handle of the carb heat. After I slowly pull the flaps back up, I bring the mixture back to a reasonable setting while climbing out. This is at a field elevation of 5200. As stated, these aircraft are usually pretty good at climbing out, even with less-than-ideal mixture settings. Get climb stabilized, then mess with the mixture....
 
Just curious why not rich/lean for the altitude?
I am at 2600' and my mixture is pulled a bit and if I am at higher airports, I pull the mixture even more. The EGTs are the main guide for me during take off, cruise and landing.
 
The drill for go around should always be - mixture, prop, throttle anyway.

You may have a need to go around or to go to max power in all kinds of scenarios. Mixture, prop, throttle. Mixture Prop Throttle.

In the twin I used to fly around, the fuel went all the way forward for initial take off and climb ONLY. It was leaned aggressively for tax, and in climb as we went, and then again in cruise. (The throttles never come back until its time to land or the descent is too hot).

A nice descent profile can have you go all the way to landing without touching the mixtures, or ever advancing the throttle, just consistent reductions. I look at it as harvesting back all the energy I spent climbing.

But once I started flying twins especially it was drilled, mixture prop throttle.

And, depending, I think just dumping the fuel forward could put you in an awkward position after a long cool descent where you load up the engines.

Theses are just my opinions.
 
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