Leaning for ground/taxi/runup

[BravoWhiskey]

I tried searching for this but couldn’t find anything.  What kind of FF do some of you use for ground opps? 

[PeteMc]

I lean to peak or maybe even a little on the lean side of peak.  The reasoning to go as lean as possible is that you can never Take Off while still lean because the engine will not produce TO power.  And it takes only a couple of minutes to damage an engine if you go full power and are lean. 

Winter Ops I'll lean twice.  First time the engine may run al little rough until it gets warmer.  So I'll lean and then get the ATIS, etc.  Then before taxi I'll fully lean.

Summer Ops you can pretty much full lean shortly after the engine starts.

On Mag Check sometimes I'll need to enrich a bit, but I don't go rich.  You'll see a significant larger drop in RPM.  So feel free to check it a few times rich and leaned so you get used to the numbers.  (Don't lean at Mag Check RPMs!  That's too close to TO power where you could potentially attempt a TO while not full rich.  Lean at/near idle.)

Take Off Procedure for me varies with the length of the runway.  Long runways (where I'm based) I'll add some power and start to roll (taxi) down the runway while I twist in the mixture, then full power.  Short runways breaks stay on and I'll add some power (less than my long runway technique), then twist in the mixture. 

I never shove in the mixture.  I have 0 knowledge/proof that it would foul a plug doing that, but I don't want to find out.  Early on when I first got my plane and was reading everything I could on engine care I saw one common thread that a lot of people were saying....  Don't do anything fast unless you have to.  So even my practice missed approaches, go-arounds, stalls, etc. I'm a lot slower with the Throttle than I would be in a real situation.  I figure the same holds true for the Mixture.  (Yes, I've had to do it for real and being slow in training does not affect how I slam everything in if needed.)

[philiplane]

If the engine is set up correctly, you don't need to lean on the ground. Leaning on the ground is a band aid for a faulty ignition system, or over-rich mixture.

[Boilermonkey]

7 hours ago, philiplane said:

If the engine is set up correctly, you don't need to lean on the ground. Leaning on the ground is a band aid for a faulty ignition system, or over-rich mixture.

That is the first time I have ever heard that advice.  Not saying it is wrong or right.

[carusoam]

Once started and warmed up….

1) Lean as much as possible, while still smooth operating…

2) use 1k rpm to spread oil around… near idle while taxiing…

3) at idle, keep an eye on amps… alternator probably won’t have any output to see…

4) The advantage of deep leaning…. You will get a stumble instead of a strong acceleration…. A very welcome reminder of departing too lean.

5) carb’d engines have crummy fuel distribution…

6) unbalanced fuel injectors may give a hint how unbalanced they are….

7) Without leaning… an O360 will collect lead pellets in the lower plugs…

 

PP thoughts only,

-a-

[McMooney]

never pay attention to the fuel flow, I lean till its running slightly rough.  

mixture becomes my throttle

[LANCECASPER]

1 hour ago, Boilermonkey said:

That is the first time I have ever heard that advice.  Not saying it is wrong or right.

I was told by Mooney's Service Director who was there during the years of the TLS/Bravo that you had to lean on the ground and that if they set the fuel flow up to run lean enough not to foul the plugs on taxi that it would be too lean to cool the engine in cruise. 

When I got my checkout in the Bravo in September 1996, Mike Miles, Mooney's test pilot took me up and he said no matter who tells you what, lean aggressively on the ground with this engine. I couldn't believe how far he had the mixture out during taxi, but he knew that airplane extremely well and it was a pleasure to watch him fly it and to be able to go up with him.

[Boilermonkey]

11 minutes ago, LANCECASPER said:

I was told by Mooney's Service Director who was there during the years of the TLS/Bravo that you had to lean on the ground and that if they set the fuel flow up to run lean enough not to foul the plugs on taxi that it would be too lean to cool the engine in cruise. 

When I got my checkout in the Bravo in September 1996, Mike Miles, Mooney's test pilot took me up and he said no matter who tells you what, lean aggressively on the ground with this engine. I couldn't believe how far he had the mixture out during taxi, but he knew that airplane extremely well and it was a pleasure to watch him fly it and to be able to go up with him.

That's what we've done for a long time.

[EricJ]

I have a quadrant and just pull the mixture to within about 3/8"-1/2" or so of the cutoff stop.   It'll still run smooth there, but just barely, and I've not had any fouling problems.

I've seen advice to do that come from enough reputable sources that it seems like a no-brainer.   Lycoming Service Instruction SI-1497A says to lean to rpm reduction and back to smoothness for ground operations for flight schools for the IO-360-L2A used in C-172s.   That's more or less what many here are saying.

[philiplane]

Most pilots use too much power to taxi, which is why they need to lean. They're no longer on the idle circuit. I've been tuning engines for 30+ years and the only planes that needed leaning on the ground had Champion massive plugs with high resistance, or Slick magnetos, or both. If you have Bendix mags and fine wire plugs, you'll probably never foul a plug. Or a Surefy electronic ignition, and fine wire plugs, will also be foul proof. Even with a rich idle mixture, you will not foul a plug if the ignition system is up to snuff. The Bravo engine is unique in that it only came with Slick mags. so until the advent of electronic ignition, we had to suffer with low spark output of the Slick magnetos. 

Edited February 4, 2022 by philiplane

[LANCECASPER]

3 minutes ago, philiplane said:

Most pilots use too much power to taxi, which is why they need to lean. They're no longer on the idle circuit. I've been tuning engines for 30+ years and the only planes that needed leaning on the ground had Champion massive plugs with high resistance, or Slick magnetos, or both. If you have Bendix mags and fine wire plugs, you'll probably never foul a plug. Or a Surefy electronic ignition, and fine wire plugs, will also be foul proof. Even with a rich idle mixture, you will not foul a plug if the ignition system is up to snuff.

No Bravos came with anything other than Slick mags. I agree on the fine wire Tempest. My Bravo would idle smoothly at 600 rpm after the fine wires.

[philiplane]

I edited my post to include that the TIO-540 in the Bravo was only offered with Slick mags, it is one of the few engines that did not offer Bendix mags as an option from Lycoming. All other Mooneys could have either brand mags from new or as a retrofit. 

Edited February 4, 2022 by philiplane

[BravoWhiskey]

I had the fine wire but they were garbage.  I switched to massives and like the way she runs now.  And aware I need to lean aggressively on the ground.  I’ll mess around this weekend with some settings to see what works.  Appreciate all the feedback.

[carusoam]

BW,

Any news to go with your fine wires being garbage?

The only fine wire issues noted around here came with the center post going missing in a handful of Tempest made plugs…

That issue was resolved over time as well… when they took that welding step in house…

Just wondering what caused your fine wire experience… possible something else is going on upstream…

 

Looks like there is a consensus…

That leaning the Bravo for taxi is…

1) not needed…

2) Often done…

3) Can indicate other issues if leaning is needed…

 

PP summary only, not original thoughts…

Best regards,

-a-

[BravoWhiskey]

5 hours ago, carusoam said:

BW,

Any news to go with your fine wires being garbage?

The only fine wire issues noted around here came with the center post going missing in a handful of Tempest made plugs…

That issue was resolved over time as well… when they took that welding step in house…

Just wondering what caused your fine wire experience… possible something else is going on upstream…

 

Looks like there is a consensus…

That leaning the Bravo for taxi is…

1) not needed…

2) Often done…

3) Can indicate other issues if leaning is needed…

 

PP summary only, not original thoughts…

Best regards,

-a-

Lancecasper's mention of leaning aggressively is in line with what I have heard from some others and appreciate that coming from a Mooney test pilot. 

Regarding the plugs, after 10hrs of use I had a 500rpm drop for both mags during run up.  The plugs looked good on inspection but still a bit fouled, cleaned them up, and still got the 500rpm drop.  With the massives i got 100 +/- 10.  As far as some other issue up stream, this is very possible.  I just had her at Weber and they did a complete electrical diagnosis and repair.  This included the idle setting and mixture.  I might reconsider going back to fine wire now that all that is done but since i have the massives in now and like the way she's running I think I'll hold off for now... and after a year of overhaul and repairs maybe let the AMU"s replenish!

[affricate]

Here is some good info about spark plugs, engine temperatures from Lycoming upon start up for what it's worth. I was reading about spark plug fouling and thought this could be beneficial.

Spark Plug Fouling.pdf

[Rick Junkin]

On 2/3/2022 at 7:54 AM, BravoWhiskey said:

What kind of FF do some of you use for ground opps?

I see about 2gph fuel flow at 800RPM while leaned for taxi. The engine stumbles at ~950RPM if I don't enrich the mixture.

I run Tempest fine wire plugs URHB32S and standard Slick mags. With proper priming my engine starts like a car, never more than a few blades.

Cheers,
Rick

[PilotX]

On 2/3/2022 at 10:19 PM, carusoam said:

 

Looks like there is a consensus…

That leaning the Bravo for taxi is…

1) not needed…

2) Often done…

3) Can indicate other issues if leaning is needed…

I can only speak for my airport at 5673 feet but full rich bogs the plane down. I lean almost 1.5 inches up here. I would say it is needed. 

[BravoWhiskey]

2 hours ago, affricate said:

Here is some good info about spark plugs, engine temperatures from Lycoming upon start up for what it's worth. I was reading about spark plug fouling and thought this could be beneficial.

Spark Plug Fouling.pdf 87.37 kB · 8 downloads

Interesting.   This document seems to contradict some operating procedures for shutdown for me.  I run at 1800rpm to do my after landing mag drop then I need 5 minute cool down for the turbo.  While the procedures on this document make sense I don’t see my engine on the list.  Having said that I have not been running at 1000-12000 after startup I’ve been at lower settings.

[Boilermonkey]

This document predates the Bravo....so take it with a grain of salt/lead.

[Rick Junkin]

14 minutes ago, BravoWhiskey said:

Interesting.   This document seems to contradict some operating procedures for shutdown for me.  I run at 1800rpm to do my after landing mag drop then I need 5 minute cool down for the turbo.  While the procedures on this document make sense I don’t see my engine on the list.  Having said that I have not been running at 1000-12000 after startup I’ve been at lower settings.

It's always interesting when this comes up.

The M20M POH and the Lycoming Operator's Manual for TIO-540 series engines differ on both starting and shutdown procedures. The POH is "binding" from a regulatory standpoint, but that doesn't preclude us from using better procedures for engine operation learned over time and codified in the engine manufacturer's documentation. Case in point is the POH cruise settings for the M20M - no one uses them anymore because of the learning that occurred through operating at those settings.

Starting:

     Mooney POH says to idle at 700-750 RPM for warm-up
     Lycoming says to idle at 1000-1200 RPM for warm-up

     The starting procedure itself is different between the two as well - the POH has you cranking with the mixture full rich, Lycoming has you start cranking at idle/cut off and advance the mixture as the engine starts. I've used both with varying degrees of success and ultimately found what works best for me and my engine, which not surprisingly ended up being a combination of the two. I warm up at 900-1000 RPM with a leaned mixture and proceed once the oil is above 100 and the CHTs are at 250.

Shut down:

     Mooney POH includes a CAUTION that states you need to operate the engine at idle (below 1000RPM) for 5 minutes to allow for turbocharger cool-down. Taxi time can be included in that 5 minutes.
     Lycoming says to "idle until there is a decided decrease in cylinder head temperature"

     So which one is right? Personally I'm past that question. My practice is low power on approach and in the pattern, idle at round-out and into the flair, rarely add much power for taxi, and do my post-flight mag and grounding check at 1000RPM when I reach the chocks. Then I shut down. The intent is to allow things to cool down and this practice accomplishes that.

My suggestion is use the documentation as guidance, understand the intent, and execute in a way that works and is easily repeatable every time you fly. When you learn something new, see if it makes sense to you and if it does, incorporate your learning to improve your practices. But don't skip the "does it make sense" step and make sure what you've heard/learned applies to you and your airplane.

Cheers,
Rick

 

 

[carusoam]

6 hours ago, BravoWhiskey said:

then I need 5 minute cool down for the turbo.  

There is plenty of data, explanations, and training available from a reliable resource….

That essentially points out that the coolest the turbo gets is just prior to the wheels touching the pavement….

Any cooler, may require a chiller….

 

just saved you five minutes…. 
 

kinda of an OWT for turbo owners…. Discussed around here somewhat frequently.

Best regards,

 

-a-

[Fly Boomer]

Geo. Braley says he actually instrumented an engine in an airplane, and flew it to prove what @carusoam said.

[BravoWhiskey]

I watched the video by Hartzell a few months back about this and if I both recall and understood correctly it had something to do with the circulation of the oil through the internal components of the turbo to prevent coking.  I just overhauled the engine and alternator… I’d like to do whatever I can to avoid going through any other overhauls for at least another year or 2

Edited February 6, 2022 by BravoWhiskey

[LANCECASPER]

6 minutes ago, BravoWhiskey said:

I watched the video by Hartzell a few months back about this and if I both recall and understood correctly it had something to do with the circulation of the oil through the internal components of the turbo to prevent coking.  I just overhauled the engine and alternator… I’d like to do whatever I can to avoid going through any other overhauls for at least another year or 2

This has been discussed at great length here. Sitting there for 5 minutes with no air cooling your air cooled engine and accessories is raising your temps. When I taxi up to my hangar I have to raise my RPMs to do a 180 to position myself to get back in the hangar, so after I do that I pull back the rpms just so my oil pressure is still in the green and wait for my temps to stabilize (TIT to drop and settle and not go up). That's going to leave the coolest oil in the turbo bearings on shutdown. Sitting there longer heats up the oil and is more likely to produce coking. There's nothing magic about 5 minutes or 3 minutes. It's temperatures you're looking for.