How to lean when landing at high altitude airport?

kicktireslightfires

kicktireslightfires

Pre-takeoff checklist
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kicktireslightfires
As thorough as Cessna's POHs are, they don't seem to have a checklist for landing at a high altitude airport, at least not for the Cessna 162. It says to lean for max RPM above 3000' pressure altitude, so I'm assuming if you're landing at an airport above 3000', you should not go full rich in preparing for landing and instead should have it leaned for maximum RPM (in the event you need to go around). My question is how does one do that? Say you're coming in to land an airport at 4,500' MSL on a stable 500 FPM descent, how do you know where to lean your naturally aspirated engine with no lean assist and by RPM rise only? Even if you leveled off at TPA, what are you supposed to do, go full throttle for 30 seconds so you can lean the mixture until the RPM rise (and giving it a couple fast twists back in)? And even then, that will only be leaned for 1,000' above the airport, not the TDZE.
 
Hopefully you're at pattern altitude several miles prior to entering the pattern. Before landing check list (MIXTURE set, Throttle set, Trim Set, Prop a little later after entering the pattern). Mixture above is Pull the Red knob back until a slight stumble, if vernier type, two turns to enrichen (3 if you're nervous) and you'll be all set for the go-around.
 
danhagan said:
Hopefully you're at pattern altitude several miles prior to entering the pattern. Before landing check list (MIXTURE set, Throttle set, Trim Set, Prop a little later after entering the pattern). Mixture above is Pull the Red knob back until a slight stumble, if vernier type, two turns to enrichen (3 if you're nervous) and you'll be all set for the go-around.
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This.

or you can also set it per EGTs or fuel flow. I have recently heard of the method you mention regarding a quick full throttle application to set mixture, but it was in a context of mountain flying (6000-12000 DA).
 
kaiser said:
This.

or you can also set it per EGTs or fuel flow. I have recently heard of the method you mention regarding a quick full throttle application to set mixture, but it was in a context of mountain flying (6000-12000 DA).
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How would I utilize the EGT for that? On the Cessna 162, there is only one EGT, not one for each cylinder.
 
kicktireslightfires said:
How would I utilize the EGT for that? On the Cessna 162, there is only one EGT, not one for each cylinder.
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I’m not familiar with the 162. If you’re familiar with your plane, you’ll get an idea of your EGT temps in various conditions (take off 100% near sea level, cruise ROP etc). You can lean to those target numbers. In many of the normally aspirated planes I fly, it’s 1250-1350. But it could vary considerably. If you only have one gauge, err for the rich side.
 
kicktireslightfires said:
As thorough as Cessna's POHs are, they don't seem to have a checklist for landing at a high altitude airport, at least not for the Cessna 162. It says to lean for max RPM above 3000' pressure altitude, so I'm assuming if you're landing at an airport above 3000', you should not go full rich in preparing for landing and instead should have it leaned for maximum RPM (in the event you need to go around). My question is how does one do that? Say you're coming in to land an airport at 4,500' MSL on a stable 500 FPM descent, how do you know where to lean your naturally aspirated engine with no lean assist and by RPM rise only? Even if you leveled off at TPA, what are you supposed to do, go full throttle for 30 seconds so you can lean the mixture until the RPM rise (and giving it a couple fast twists back in)? And even then, that will only be leaned for 1,000' above the airport, not the TDZE.
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Depends entirely on the physical altitude and the density altitude. One way to lean in flight is to reduce mixture until the engine is running just a tiny bit rought, as described above, then increase mixture.

But…if you’re coming into land at 4500 msl, you’ve already been at that altitude and higher, so you should have been leaning at cruise for altitude. Hence when you’re ready to land, you increase the mixture, don’t lean for landing!

Again, as noted in earlier response,set eveything up long before the pattern altitude,don’t futz with it at landing. Don’t complicate things.

You don’t lean for a mere 1000 ft.

Where are you flying?
 
kaiser said:
I’m not familiar with the 162. If you’re familiar with your plane, you’ll get an idea of your EGT temps in various conditions (take off 100% near sea level, cruise ROP etc). You can lean to those target numbers. In many of the normally aspirated planes I fly, it’s 1250-1350. But it could vary considerably. If you only have one gauge, err for the rich side.
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Cessna’s failed attempt at an LSA. Kinda fun to fly but also kinda uncomfortable.
 
What I do is once at pattern altitude I lean until I get an RPM drop. I then richen until I see the peak RPM I saw during the leaning. Then I push the mixture about 1/2 way in or with Vernier Mixture most airplanes I will richen 3 full turns. This is pretty rich mixture and should be fine for a Go around and good engine temps. This is often what I do for pattern work, during the runup.

But every airplane is a bit different, So listen to the engine and instrumentation you have to determine if you should change that some.
I use the same leaning procedure on the ground during runup. If the CHT temps are good I will often only richen about 1/4 the way back in or 2 turns in from peak RPM if departing where it is going to be getting richer as I climb to cruise altitude.

Again I monitor temps and if CHTs get much above 380 I richen it up.

Brian
CFIIG/ASEL
 
murphey said:
But…if you’re coming into land at 4500 msl, you’ve already been at that altitude and higher, so you should have been leaning…
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Good advice. Go to full power and lean for best power, as you pass through your destination field altitude. Remember where the red knob needs to be, and set it there on final. In the meantime, set it for best power when in cruise flight.

You don’t lean for a mere 1000 ft.
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Correct.
 
If your engine has a fixed pitch prop and you are at cruise speed and throttle, then slowly lean until you get an RPM reduction, then slowly add richness until the RPM increases and tops out. If you are setting up for a go-around, I would increase richness slightly more until RPM just begins to drop slightly. This will put you on the rich side of Peak EGT and depending on how high the altitude is this may be enough. Red Box 15 MR IO360 200HP.JPG RED FIN RAW.png

The Graph for the IO-360 200HP is the one I use in my airplane. Notice the green constant air flow lines are vertical at max power for that airflow setting, and this would be the sum of MP + RPM/100 at that power setting from the POH. Notice the lines curve towards less power the richer and higher they go, and the lines curve more to less power the leaner and lower they go. The constant fuel flow curves are vertical at maximum fuel economy. At this point HP developed = 15 times fuel flow. So 60% x 200HP = 120 HP. 120 / 15 = 8 GPH.

You can adapt this curve to your engine by taking your rated HP x % power / 15 will equal GPH. If naturally aspirated, then the MR numbers will be the same. A quick rule of thumb for power is a loss of 3% per 1000 feet above standard altitude. So if your take-off Density Altitude is 2000 feet then the total power available will be .97 x .97 = .9401 or 94.01%. If your high altitude airport is 3000 feet above your first airport with then the Density Altitude will be 2000 + 3000 = 5000 feet DA. .97 x .97 x .97 x .97 x .97 (or .97 to a power of 5) = .8787 or 85.87% of rated power. Look at the graph. In order to be in the safe zone I would want to be about 1/3 more rich for the go-around, but that is just me. YMMV.
 
Or better yet....find a CFI or someone who's intimately familiar with the 162 and understands how to lean properly.
 
Keep in mind that most manuals talk about leaning at 3000 or 5000 feet (density altitude). One thing that tells us is that being perfect isn't necessary. It's a pretty big ballpark. My own method involves recognizing that huge fudge factor and guesstimating what I need for a go-around. Worked just fine all 20 years I flew in Colorado.

Need a little more certainty? A second workable alternative is to lean to roughness and increase to smooth operation during the descent. Add a little (3-4 twists if you have a venire) for extra fuel and cooling. That will also keep you in that ballpark.

If you want more specific numbers, the same EGT that was the result of your leaning at altitude will work all the way down to sea level.
 
murphey said:
But…if you’re coming into land at 4500 msl, you’ve already been at that altitude and higher, so you should have been leaning at cruise for altitude. Hence when you’re ready to land, you increase the mixture, don’t lean for landing!
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Increase/richen the mixture by how much is the question. After coming down from higher altitude where was leaned at cruise, just richen the mixture until RPM peaks?
 
Todd82 said:
The reason it's not in the 162 POH is nobody ever thought they'd get a 162 high enough for it to matter.
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The 162 service ceiling is 15,500. I've personally been in one up to 13,500. I've never landed one at an airport higher than 1,000' however.
 
kicktireslightfires said:
The 162 service ceiling is 15,500. I've personally been in one up to 13,500. I've never landed one at an airport higher than 1,000' however.
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I did my first 100+ hours in a C162, all of that in the northern Sierra flying out of airports with density altitudes 6000' to 9000'. With a power/weight ratio better than a 180hp C172, I also had the C162 up to 13,500 over Tioga Pass.

As many noted above, before or upon entering the pattern: set a high power setting, lean mixture to onset of roughness, and then enrichen until reasonably smooth.
 
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