Lean of peak ops, landing

[Danb]

When flying lean of peak upon approach to landing when do you go full rich. 

[802flyer]

There's nothing about the approach to landing that actually requires full rich. The engine will be perfectly happy if you continue to richen-as-needed per whatever strategy you employed for the rest of the descent phase. The only reason that going full-rich would be necessary is if you require high/full power such as for a go-around.

There's a contingent of people that never go full rich given that the vast majority of landings don't result in a go-around and so they feel better-off avoiding any fouling/increased fuel consumption/etc for routine operations. If a go-around is necessary, they plan to push the mixture forward as part of the go-around procedure (and presumably they practice this way to build muscle memory). This is arguably a valid approach as long as you do indeed remember to configure appropriately on the eventual go-around.

There's another contingent that would like the inevitable unexpected go-around to be as simple as possible, and so they argue in favor of going full rich at some prior point. I go full-rich as part of my GUMPS check (midfield downwind, arriving at FAF, etc.) and haven't had any problems with fouling and don't mind burning a few extra tablespoons of fuel to simplify a go-around. Those who fly normally-aspirated engines at high field elevations might never go full rich regardless.

[Ragsf15e]

26 minutes ago, Danb said:

When flying lean of peak upon approach to landing when do you go full rich. 

I do it (and teach it) during my GUMPS (or “Before Landing Checklist”) which I do on downwind or prior to the final approach fix if ifr.  I prefer to just have the throttle left for a go around, but there are other techniques.

[N201MKTurbo]

My mixture doesn't change with altitude. I set LOP at altitude. When I descend I leave the mixture alone. It will give me full cruise power at that mixture setting. If I have to go around, I can get takeoff power by just pushing the mixture forward. All I have to do is stick a couple of fingers to the right when I increase the throttle.

Plus, it keeps my plugs clean.

[EricJ]

If you fly in high DA a lot there are times when it is a Bad Idea to go full rich.   There've been accidents around here where an aircraft failed to climb out after takeoff or on a go-around that are thought to have been due to insufficient leaning (or full rich) settings.

For me that just means special attention is always required to the mixture on approach and go around.   It is often not "full rich" on go-around, but some estimate of about where it should be to not cause a significant decrease in power.   It's a pretty wide window between "too rich" and "too lean", so a reasonable guess followed up by attention to EGTs is usually sufficient.   It is more work, but can make a difference when needed.

Otherwise I'm in the camp of leaving it alone until needed, which means pushing the mixture forward with the throttle in the event of a go-around.   In any case, keeping an eye on EGTs is always a good idea.

[Ragsf15e]

1 hour ago, Danb said:

When flying lean of peak upon approach to landing when do you go full rich. 

Definitely true what @EricJ mentioned about not needing/wanting “full rich” at high density altitudes, although I like to be on the rich side of peak still.  It’s not hard to make an approximation of a good rich mixture on dw though.  Push it in full, back off 1/2” or so.  As eric said, after the go around is handled, check egts.

[DCarlton]

Not to hijack the thread too far, but I'm curious how many folks use the lean find function on their engine monitor exclusively to set the mixture.  Or do you eyeball the EGTs and adjust the mixture the ole fashioned way until it feels and sounds right.  I've been a bit lazy using my engine monitor and I tend to add a turn or two beyond what's indicated.  I'm still in the ROP camp in my F; just always done it that way.

[MikeOH]

I climb and cruise at WOT. After TO and initial climb I usually set 2600 rpm and lean to keep sea level EGTs (around 1250-1300) until leveling off and then set 2500 rpm. At typical cruise altitudes of 7000-10,000 I just pull the mixture back to 8.5-9.5 gph depending on how fast I want to go

[N201MKTurbo]

23 minutes ago, DCarlton said:

Not to hijack the thread too far, but I'm curious how many folks use the lean find function on their engine monitor exclusively to set the mixture.  Or do you eyeball the EGTs and adjust the mixture the ole fashioned way until it feels and sounds right.  I've been a bit lazy using my engine monitor and I tend to add a turn or two beyond what's indicated.  I'm still in the ROP camp in my F; just always done it that way.

I have it on my UBG16, but I have never used it. I just pull it lean then richen it till my #2 cylinder gets to 380 degrees. That is at 28” 2400 TIT 1525 9.1 GPH. It gets me about 160 down low and about 170 up high.

[EricJ]

25 minutes ago, DCarlton said:

Not to hijack the thread too far, but I'm curious how many folks use the lean find function on their engine monitor exclusively to set the mixture.  Or do you eyeball the EGTs and adjust the mixture the ole fashioned way until it feels and sounds right.  I've been a bit lazy using my engine monitor and I tend to add a turn or two beyond what's indicated.  I'm still in the ROP camp in my F; just always done it that way.

Once in a while (as in once every month or two) I'll lean to peak to get an idea of what temperature that is, and then operationally just set EGTs where I want them relative to that, usually around 100F ROP.    Watching EGTs and fuel flow for the conditions or current mission means it varies a bit, and if it's been a while since I've checked where peak EGT is, it might be worth updating.   I'm never trying to squeeze out super performance or efficiency, though, just running it decently to keep it healthy.

[KSMooniac]

I don't go full rich until I go-around, or the next takeoff after landing with a lean mixture.  And if it is hot and/or high density altitude, I may not go full rich then.

[201Mooniac]

1 hour ago, DCarlton said:

Not to hijack the thread too far, but I'm curious how many folks use the lean find function on their engine monitor exclusively to set the mixture.  Or do you eyeball the EGTs and adjust the mixture the ole fashioned way until it feels and sounds right.  I've been a bit lazy using my engine monitor and I tend to add a turn or two beyond what's indicated.  I'm still in the ROP camp in my F; just always done it that way.

I hadn't been using it much until recently.  I installed a GI 275 EIS awhile ago but hadn't been doing much LOP.  I recently tried leaning mode on the EIS to get more data on how lean I was going and how my spread looked once LOP.  It is very informative but it really didn't get me anywhere different from where I was already operating.  Cool to see the data though.

[TheAv8r]

1 hour ago, DCarlton said:

Not to hijack the thread too far, but I'm curious how many folks use the lean find function on their engine monitor exclusively to set the mixture.  Or do you eyeball the EGTs and adjust the mixture the ole fashioned way until it feels and sounds right.  I've been a bit lazy using my engine monitor and I tend to add a turn or two beyond what's indicated.  I'm still in the ROP camp in my F; just always done it that way.

I set it to fuel flow on my JPI 930 based on power setting. In the beginning, I used the LF function to figure out where a good LOP setting was, and what FF I'd get for that based on the power setting. Now, I just lean it to that fuel flow, then check EGTs/CHTs and TAS accordingly. In my M20E, that's usually 65% power, 142kts TAS at 7.7-8gph. 

[A64Pilot]

Pretty simple answer, and I’m not trying to be cute.

We had a saying in the Army, it was think how your going to explain it to the accident review board, that had a tendency to make you follow checklists, because “I followed the checklist” is usually easily defensible, argue that you know better than the approved POH is tougher.

Gas, undercarriage, MIXTURE, Prop is of course generic, but I’ll embarrassingly admit I can’t give you the approved format from memory.

Why would you set mixture for landing anywhere else except in the before landing check? Notice it says mixture, not full rich because as has been said full rich at high altitude may not be optimum, but I think it’s safer to be extra rich than extra lean for a go-around.

Personally I descend at altitude lean setting, meaning it gets leaner the more I descend, therefore it’s pretty likely that it’s so lean it won’t accelerate with rapid throttle advance, but I do go full rich during GUMPS as I’m pretty much at sea level. I’m also well below 65% power so any mixture is safe.

In my opinion you should be prepared for an unplanned nearly instant go-around, whether it’s some idiot crossing the runway or wildlife at some small airport, fly long enough and you’ll suddenly see something in front of you that you had rather not hit. Where I am now, it’s Sand Hill cranes, you would be surprised how well they blend in on a grass runway, the other day it was cows, we had a break in the fence I guess.

Your not going to foul plugs and any fuel difference in landing will be ounces at most.

For those that say they will foul plugs, somethings wrong. It’s not normal to foul plugs on landing

[PeteMc]

I'm in the camp of not going full rich.  Yes, you do need to remember to push in the mixture if you do a Go-Around, but I train that way since I don't see the need to go full rich when (knock on wood) I've only had one time I had to cram everything forward (and that was because we were doing some extreme short field landing training and got a big drop near the threshold).  

On the comment that you should not go full rich at higher DA, I totally agree and wish I had thought that through on my first X-US flight.  Landed in AZ in a Cherokee Six, I had gone full rich in the pattern and once on the runway as soon as I slowed down enough the prop stopped windmilling and I rolled just barely off the runway with a dead engine.  Felt like forever until I figured out what had happened and got the engine started again. 

[Danb]

7 hours ago, 802flyer said:

There's nothing about the approach to landing that actually requires full rich. The engine will be perfectly happy if you continue to richen-as-needed per whatever strategy you employed for the rest of the descent phase. The only reason that going full-rich would be necessary is if you require high/full power such as for a go-around.

There's a contingent of people that never go full rich given that the vast majority of landings don't result in a go-around and so they feel better-off avoiding any fouling/increased fuel consumption/etc for routine operations. If a go-around is necessary, they plan to push the mixture forward as part of the go-around procedure (and presumably they practice this way to build muscle memory). This is arguably a valid approach as long as you do indeed remember to configure appropriately on the eventual go-around.

There's another contingent that would like the inevitable unexpected go-around to be as simple as possible, and so they argue in favor of going full rich at some prior point. I go full-rich as part of my GUMPS check (midfield downwind, arriving at FAF, etc.) and haven't had any problems with fouling and don't mind burning a few extra tablespoons of fuel to simplify a go-around. Those who fly normally-aspirated engines at high field elevations might never go full rich regardless.

Reason for question embarrassing as it is, I just started running LOP upon landing in St Louis I think I didn’t go full rich on landing and my engine cut out on the runway, didn’t have enough energy to rook to taxiway, had a difficult time hot starting and tied up the runway for a few minutes. Not my best day, never had issues with the bravo not so with my crappy acclaim. I assume I went rich but can’t come up with a reason the engine cut out, I was lowish on fuel but had 24 gallons based on my top off. 

[Fly Boomer]

3 minutes ago, Danb said:

Reason for question embarrassing as it is, I just started running LOP upon landing in St Louis I think I didn’t go full rich on landing and my engine cut out on the runway, didn’t have enough energy to rook to taxiway, had a difficult time hot starting and tied up the runway for a few minutes. Not my best day, never had issues with the bravo not so with my crappy acclaim.

Those big-bore Continentals are more sensitive to poorly maintained fuel systems.  Here is a suggestion that's easy to say, but hard to do:  Find a maintainer that knows how to set up a big-bore Continental, and let them do the job.  If they don't have the knowledge and instrumentation, they don't have a chance.

[Danb]

It just had a top done about 50 hours ago at maxwells I believe there competent

[N201MKTurbo]

2 minutes ago, Fly Boomer said:

Those big-bore Continentals are more sensitive to poorly maintained fuel systems.  Here is a suggestion that's easy to say, but hard to do:  Find a maintainer that knows how to set up a big-bore Continental, and let them do the job.  If they don't have the knowledge and instrumentation, they don't have a chance.

The procedure is straight forward. It is spelled out in the maintenance manual along with the required gauges. That being said, I've seen plenty of mechanics just turn a screw with no gauges saying "It just needs a little more fuel" or something like that. I'm pretty sure that's how they get jacked up. Even here on Mooneyspace, I've heard comments that suggest setting the fuel flows outside the specs. While this may help cool the engine, it could mess up the linearity of the system and the mixture may not track the throttle quite right.

[LANCECASPER]

1 hour ago, Danb said:

Reason for question embarrassing as it is, I just started running LOP upon landing in St Louis I think I didn’t go full rich on landing and my engine cut out on the runway, didn’t have enough energy to rook to taxiway, had a difficult time hot starting and tied up the runway for a few minutes. Not my best day, never had issues with the bravo not so with my crappy acclaim. I assume I went rich but can’t come up with a reason the engine cut out, I was lowish on fuel but had 24 gallons based on my top off. 

Funny you should mention that. I did the exact same thing landing at KGPZ (Grand Rapids, Minnesota) this summer, as I pulled off the runway onto the taxiway it stumbled and died. Completely my fault for not enriching the mixture in my GUMPS. This engine doesn't load up the plugs when it's rich like a lot of Lycomings do so I now make sure I work that into my flow.

[jlunseth]

Well, the OP flies a turbocharged aircraft, not an NA. Reading through the answers, quite a few apply to NAs. For example, in an NA it would indeed be a problem at a high DA airport to go too rich. That is not relevant to turbo ops. The turbo needs all the fuel it can get at full power to keep the engine cool.  Lots of answers from F and J folks.

I don’t fly an Acclaim, I fly a 231, so it may be that the fuel setting issues are a little different between the two. But I am going to relate what I do in my 231 to the extent it is applicable to the Acclaim. Turbocharged engines are generally set to provide a very rich fuel flow at full power in order to keep the engine cool on takeoff and during a long climb to altitude. Mine is that way when set up properly. During landing the engine will burble if I make the fuel flow full rich. The burble is because the engine is drowning in fuel and not igniting consistently. The way to handle it is to keep the mixture lean during the landing phase. For that reason, I don’t make the mixture full rich unless I actually need to go around.

Typically it is necessary to make the mixture a little richer after touch down. Once the aircraft’s descent is no longer helping the prop, the engine can die during rollout if it is very lean, so a little more fuel may be needed.

The 231s induction system is not as sophisticated as the Acclaim, so it may be that the mixture issues are less pronounced, but advice applicable to leaning an NA engine is generally not applicable to a turbo and in fact can damage the turbo.

[Z W]

I do exactly what jlunseth does - stay lean for landing to avoid the full rich at idle "burble", but then enrichen back to ground taxi setting prior to taxi.  If you don't add a little mixture back in, depending on how lean you were, you can kill the engine when you add throttle to taxi.  In fact, I will sometimes enrichen back to the taxi mixture setting in the pattern - just leaned out about an inch and a half.  That's a good setting for both landing and taxi.

Takeoff and go-around are always mixture -> prop -> throttle.  You should be leaned to taxi to the runway, and don't want to takeoff leaned (turbo engines only).  So just make it part of your muscle memory.

Also a 231 engine here, but maybe this will help you with a technique for your Acclaim.

[PeteMc]

7 hours ago, Z W said:

enrichen back to the taxi mixture

Did you really mean "taxi mixture" while in the Downwind?  From what I've been taught (PPP and others) and told by multiple mechanics when I've asked, my "Taxi Mixture" is WAY TOO LEAN for the engine to operate in flight.  It is intentionally too lean to achieve Takeoff Power so I don't forget to go Full Rich when I do go to Takeoff.  

 

[jlunseth]

1 hour ago, PeteMc said:

Did you really mean "taxi mixture" while in the Downwind?  From what I've been taught (PPP and others) and told by multiple mechanics when I've asked, my "Taxi Mixture" is WAY TOO LEAN for the engine to operate in flight.  It is intentionally too lean to achieve Takeoff Power so I don't forget to go Full Rich when I do go to Takeoff.  

 

I understood what he was saying. When I do pattern work, it is full rich for takeoff and for the climb to pattern altitude, but once at pattern altitude I reduce MP to 24.5 or so and also pull the mixture back somewhat so the engine is operating lean. The objective is to slow the aircraft to 90 when the gear goes down. There isn’t time to fiddle with the mixture to the tenth of a GPH. I pull it back about as far as I do for taxi, where I lean to idle rise. In both instances the engine won’t be operating at that setting for very long so it is just a rough approximation. I would say that idle rise is about an inch and a half leanward on the stick from full rich, but frankly it changes at annual whenever the fuel flows are reset. When that happens (the fuel flows are reset), I take a flight or two to get used to the new position of the mixture knob, I might actually do an idle rise test, pull the knob back with the engine at 1100 until I get to the highest RPM. You should see a rise of about 75 RPMs from full rich, and then a further fall once the mixture is more lean than idle rise. That tells me about where idle rise is going to be in terms of how far out the mixture knob needs to be. I pull the mixture about that far out once I am at pattern altitude and in level flight, maybe a little more than at taxi but pretty close.

[Z W]

5 hours ago, PeteMc said:

Did you really mean "taxi mixture" while in the Downwind?  From what I've been taught (PPP and others) and told by multiple mechanics when I've asked, my "Taxi Mixture" is WAY TOO LEAN for the engine to operate in flight.  It is intentionally too lean to achieve Takeoff Power so I don't forget to go Full Rich when I do go to Takeoff.  

 

Yes.  I don't lean that much for taxi.  I've heard it taught as well.  I find it too easy to give it a little too much throttle while trying to taxi uphill and stall the engine, which doesn't inspire confidence in passengers and can disrupt ground traffic flow.  So I leave it rich enough for that not to happen, about 1.5 inches out.  It's enough that I've never fouled a plug, and I go full rich before every takeoff and go-around.  And I'm enrichening the mixture in the pattern to get there, from my cruise mixture setting.

It's probably still too lean to make full takeoff power, if I had to guess.  And verifying fuel flow when you start the takeoff roll is always a good idea too.  But setting your engine up to stall as some kind of a reminder to enrichen the mixture for takeoff doesn't sit right with me.  I prefer a checklist and good muscle memory.