Leaning for density altitude

[Rusty Pilot]

I apologize for asking a question that I am sure has been asked and answered elsewhere on Mooneyspace, but I was unable to find a thread addressing it.  Yesterday I flew in and out of Garrett County Airport 2G4 about 3,000' field elevation with a 5,000' runway.  No issues, but a long takeoff role for my afternoon flight with 4,600DA.  My climb performance was great and I leaned about 10% for takeoff.  My question is what tips for leaning for best power should I be using?  I flew about 400lbs. below max gross.

[mike_elliott]

Simplified version: Next time you visit the coast and are at sea level, note what the EGT of the hottest cyl is on your takeoff roll. That becomes your target EGT to lean to at any airport for takeoff. lean to this number during your climb to cruise alt. also.

Mike Busch has an article about Target EGT you might look up.

[midlifeflyer]

I lived, flew, and taught in Colorado for 20 years. This is the standard procedure taught at most flight schools (it's a personal copy and paste; no, I did not just type it.

Leaning for takeoff at high density altitude (normally aspirated).

If you are operating for the first time in a high density altitude environment, local instruction is always your best bet because it's not just about the effect on power. That said, this is the method generally taught at flight schools in Colorado.

Target leaning for max power is done at runup power. This is for two reasons other than it just works for all but a very few make/models.  One is that leaning at full power can be hard on the brakes of higher performance engines; the brakes might not even hold in some. The other is that, a constant speed prop will act like a fixed pitch one when set at runup rpm so you an easily see the changes on the tach..

When you are ready to do the run-up:

1. Enrichen the mixture (you should have leaned it for taxi, so you need to enrichen it for the run-up power demand). You don't really need to go back to full rich at this point, but there's no harm in doing so until you learn about where to set it.

2. Go to run-up power.

3. Lean. You will initially see a rise in RPM as you reach best power and then a drop. When you see the drop, enrichen back to peak. 

4. Enrichen more. On airplanes with a vernier mixture control, 3-4 twists will do it. Without a vernier, about 1/4-1/2" tends to take care of it. The enrichment is for 2 reasons:  approximate the additional power  requirements for takeoff and for engine cooling.

In most airplanes, this will be exactly what you need for takeoff. Many instructors I know stop here but bear in mind that this is an *approximation* which needs to be cross-checked, at least until you have learned  the run-up technique works for your airplane.

The cross-check should be done at full power. It does not take long a few seconds at most. If the brakes will hold, you can do it while still at the runup area, or you can wait until the runway just before beginning the takeoff roll. I usually do that final check on the takeoff roll. The exact check varies. It's often simply getting expected rpm but you might have a table of fuel flow targets for takeoff to measure against. If you know your target best power EGT, great. Personally I have never had to move the mixture more than a 1/2 twist or its equivalent. 

Finally, remember that this isn't brain surgery. Look at your POH - that instruction to lean "above 3000' is a pretty good indication of how much leeway is built in.
 

[ArtVandelay]

I use fuel flow. If I know Im going to a high altitude airport, I make a note of where the mixture knob is for that altitude in a previous flight that way I can focus on the flying part instead of fiddling with the mixture knob.

[Greg Ellis]

2 hours ago, mike_elliott said:

Simplified version: Next time you visit the coast and are at sea level, note what the EGT of the hottest cyl is on your takeoff roll. That becomes your target EGT to lean to at any airport for takeoff. lean to this number during your climb to cruise alt. also.

Mike Busch has an article about Target EGT you might look up.

There is a free to download PowerPoint presentation on leaning to your target EGT found at Advanced Pilot Seminars.  It may be helpful as well but basically says what Mike has explained above.

https://www.advancedpilot.com/tech.html 

[RobertGary1]

At high density airports I always do a full power run up and then lean until I get an rpm drop. Than enrichen a bit from there. I certainly would not attempt a full rich take off. In the Lycomings you’ll get less power. In some Continentals you’ll get much less power. We’ve had accidents in the mountains here from that.  

Full rich departures for low density take offs 
 

-Robert  

[Ragsf15e]

People covered the target egt method pretty good and several people made sure everyone knows about the possibility of reduced power if you didn’t lean (full rich) or even if you lean too much (past peak rpm).  Here’s one more tidbit... you are balancing maximum power output with engine temperature control.  Don’t forget to look at the temperature side of that equation after you’re safely cleaned up and climbing no matter what technique you use.  At high power, low speed, and thin air (high DA), the CHTs can heat up quickly if you don’t have extra fuel going through for cooling.  No matter if you use target egt (as I do) or if you do a full power runup and then enrich “1-2 turns”, look at your chts on departure and enrich the mixture or increase forward speed if they are climbing too high.  I do something (enrich) by 380f to make sure they will stay around 380 but definitely below 400.  I also cruise climb at 120mph.  The temps are my personal technique, but you should definitely look at cht to adjust your pretakeoff lean and make sure it’s working.  If you do use target egt, adjustment should be minimal but it may be there on a real hot day or high altitude.

[carusoam]

Rusty pilot...

Lets talk the basic measurement of leaning...

The idea of leaning 10% is a new one to me...

 

I haven’t finished reading this thread, yet...

Some people lean to an EGT or TIT...

Some go ROP by a number of degrees... target EGT method.

Some go LOP by a number of degrees...

Some use the blue or white box method... simplified EGT method...

Some lean to peak EGT... for some reason...

Some use FF to lean... to a familiar spot...

But I haven’t heard I leaned about 10%...
 

10% of what?   And how far inside the red box was it?

What was the DA at the airport that day?

 

PP thoughts to become familiar with as you go... Sooner is better than later...

Best regards,

-a-

[Rusty Pilot]

5 hours ago, carusoam said:

Rusty pilot...

Lets talk the basic measurement of leaning...

The idea of leaning 10% is a new one to me...

 

I haven’t finished reading this thread, yet...

Some people lean to an EGT or TIT...

Some go ROP by a number of degrees... target EGT method.

Some go LOP by a number of degrees...

Some use the blue or white box method... simplified EGT method...

Some lean to peak EGT... for some reason...

Some use FF to lean... to a familiar spot...

But I haven’t heard I leaned about 10%...
 

10% of what?   And how far inside the red box was it?

What was the DA at the airport that day?

 

PP thoughts to become familiar with as you go... Sooner is better than later...

Best regards,

-a-

DA was 4,600, runway length 5,000' and the suggestion to lean 10% came from a pilot sitting in the FBO.  To be honest, the high DA for my afternoon takeoff snuck up on me.  It started out as a cool day and I was expecting a DA in the 3,500' range requiring only minimal leaning.  I have a 1974 Mooney 20C with a power quadrant and leaned my mixture back about 1" which is about 10% of my mixture cable travel range.  Since I plan to use 2G4 regularly, I plan to get up with an instructor soon and review proper leaning.  I am a 200 hour pilot with 100 in Mooney and as you might guess from my screen name left flying for a long time and came back 2 years ago.  Now one more dumb question, "what is the red box?"  I don't have an engine monitor and see only 2 cylinder for CHT and have a single EGT gauge I use for leaning in cruise.  The tips on here have been helpful.  I went back and reviewed my POH again it seems I was getting a book value ground role and climb rate (just lucky this time, I want to be smarter next time).

[midlifeflyer]

Leaning to target EGT is a great idea but with respect to high density altitude takeoffs...

1. It's not much help until you know what it is. 
2. I'm happy to use it for cruise. So much more efficient than the EGT version of hunt and peck. But I want manual certainty of best power the old fashioned way for takeoff.

[Greg Ellis]

35 minutes ago, Rusty Pilot said:

 "what is the red box?"  I don't have an engine monitor and see only 2 cylinder for CHT and have a single EGT gauge I use for leaning in cruise.  The tips on here have been helpful.  I went back and reviewed my POH again it seems I was getting a book value ground role and climb rate (just lucky this time, I want to be smarter next time).

Here is an article that may help you with the red box.  It is essentially an EGT and CHT range that you want to try to stay out of at certain percent power due to high cylinder pressures which can cause issues with cylinder life, etc.  The article is by Mike Busch and he essentially explains the work that was done at Advanced Pilot seminars on engine operations.  

https://resources.savvyaviation.com//wp-content/uploads/articles_eaa/EAA_2012-12_red-box-red-fin.pdf

[midlifeflyer]

27 minutes ago, Rusty Pilot said:

Now one more dumb question, "what is the red box?"

Short version. The engine studies by Busch and others referenced above (Go to it, really) demonstrate that an engine should be operated in cruise either substantially rich of peak (about 100 F) or lean of peak. They found that for most engines, the 50 F rich EGT in the POH is the worst place to be, producing the highest CHT and internal pressures, both leading to premature engine wear. Both high rich of peak and lean of peak are cool. 

Perhaps obviously, when one leans the engine to run lean of peak one needs to pass through that area where the effects are the worst. The Red Box is that range of "bad" EGT between "good" rich and "good" lean.

[apenney]

@Rusty Pilot you based at Stafford or Shannon?

[ArtVandelay]

Short version. The engine studies by Busch and others referenced above (Go to it, really) demonstrate that an engine should be operated in cruise either substantially rich of peak (about 100 F) or lean of peak. They found that for most engines, the 50 F rich EGT in the POH is the worst place to be, producing the highest CHT and internal pressures, both leading to premature engine wear. Both high rich of peak and lean of peak are cool. 
Perhaps obviously, when one leans the engine to run lean of peak one needs to pass through that area where the effects are the worst. The Red Box is that range of "bad" EGT between "good" rich and "good" lean.

That’s the first time I saw someone mention “premature engine wear”. Is that a function of the high CHTs? Because I don’t see high cylinder pressure being a bad thing if cylinders remain cool and the combustion event is normal and timed properly

[Rusty Pilot]

36 minutes ago, apenney said:

@Rusty Pilot you based at Stafford or Shannon?

Shannon, hanger 34, red and white 7104V

[apenney]

Just now, Rusty Pilot said:

Shannon, hanger 34, red and white 7104V

Based in Wisconsin but I'm in Fredericksburg from time to time - this was the first for my Mooney though in July.

 

[midlifeflyer]

42 minutes ago, ArtVandelay said:

That’s the first time I saw someone mention “premature engine wear”. Is that a function of the high CHTs? Because I don’t see high cylinder pressure being a bad thing if cylinders remain cool and the combustion event is normal and timed properly

The guys who do this put high CHT and high cylinders pressure together.

[larryb]

The cylinder pressure they are talking about is peak pressure. You don’t want the peak too high. Think of a sharp spike vs a gradual push. In the red box you get more of a spike. Outside the box more of a push.

[Rusty Pilot]

2 hours ago, apenney said:

Based in Wisconsin but I'm in Fredericksburg from time to time - this was the first for my Mooney though in July.

 

Great looking Mooney.  I think we have 5 on the field now and several owners are on Mooneyspace.

[midlifeflyer]

BTW, Busch et al tend to get very technical. The very best dow-to-earth discussion of LOP, ROP, and the Red Box is Martin Pauly's 

 

[Ragsf15e]

12 hours ago, midlifeflyer said:

Leaning to target EGT is a great idea but with respect to high density altitude takeoffs...

1. It's not much help until you know what it is. 
2. I'm happy to use it for cruise. So much more efficient than the EGT version of hunt and peck. But I want manual certainty of best power the old fashioned way for takeoff.

1. True.  However it only takes 1 takeoff at sea level, full rich.  Look at the egts.  IO-360 should be low 1200s if mixture is set up right.  I don’t know where a carb version falls.

2.  With respect, I think you’ve got it backwards.  Target egt is real good to keep max power balanced with CHTs as you climb.  You will have to lean slowly every 1,000’ or so as you climb to keep egt at your target.  Doesn’t have to be exact, just within about 20-50 and you’ll see consistent power and CHTs.  If you leave a target egt set in cruise, you’ll be overly rich.  Maybe 150-200 ROP as a guess.

In cruise, there are a lot of factors affecting cruise power and they are more constant than when you’re climbing since alt/temp/pressure are no longer changing.  In cruise you can be very exact and set a very specific egt for desired operation-like 100ROP or 20LOP for example.  In cruise, it’s worthwhile to go through the 1-2 minutes of setting the egt properly.

Now what about an intermediate level off or altitude changes on instrument vectors... First, if the power is pulled back below 65%, you aren’t gonna hurt anything so it doesn’t really matter where the mixture is set as long as it’s running smoothly.  If you’re at full power, use a known fuel flow to get in the ballpark of 100ROP or LOP, like ~9gph for LOP or 12gph rop (original target egt is fine too but overly rich).

[carusoam]

See if you can get your single EGT set up properly... that thing has a handbook of about 20 pages that can be very helpful...

Its probably posted around here and findable by its manufacturer’s name...

Best regards,

-a-

[midlifeflyer]

11 hours ago, Ragsf15e said:

1. True.  However it only takes 1 takeoff at sea level, full rich.  Look at the egts.  IO-360 should be low 1200s if mixture is set up right.  I don’t know where a carb version falls.

2.  With respect, I think you’ve got it backwards.  Target egt is real good to keep max power balanced with CHTs as you climb.  You will have to lean slowly every 1,000’ or so as you climb to keep egt at your target.  Doesn’t have to be exact, just within about 20-50 and you’ll see consistent power and CHTs.  If you leave a target egt set in cruise, you’ll be overly rich.  Maybe 150-200 ROP as a guess.

In cruise, there are a lot of factors affecting cruise power and they are more constant than when you’re climbing since alt/temp/pressure are no longer changing.  In cruise you can be very exact and set a very specific egt for desired operation-like 100ROP or 20LOP for example.  In cruise, it’s worthwhile to go through the 1-2 minutes of setting the egt properly.

Now what about an intermediate level off or altitude changes on instrument vectors... First, if the power is pulled back below 65%, you aren’t gonna hurt anything so it doesn’t really matter where the mixture is set as long as it’s running smoothly.  If you’re at full power, use a known fuel flow to get in the ballpark of 100ROP or LOP, like ~9gph for LOP or 12gph rop (original target egt is fine too but overly rich).

I didn't say "climb." I said I wanted manual confirmation that have best power for "takeoff." I should have been clearer. You are right about extended climb. The altitude and hence the requirements are changing and maintains target EGT is a bit better than guestmating.

But I am not willing to bet on the numbers for takeoff at Key West automatically applying for takeoff at Leadville. I want to see it and feel it. I can be a Luddite about some things.

[midlifeflyer]

On 9/8/2020 at 7:31 AM, mike_elliott said:

Simplified version:

Here's a pretty good simplified version directly from the Advanced Pilot Seminars group Busch bases his article on...

https://www.advancedpilot.com/course/download/TargetEGT.pdf

[Missile=Awesome]

On 9/9/2020 at 6:01 AM, Rusty Pilot said:

DA was 4,600, runway length 5,000' and the suggestion to lean 10% came from a pilot sitting in the FBO.  To be honest, the high DA for my afternoon takeoff snuck up on me.  It started out as a cool day and I was expecting a DA in the 3,500' range requiring only minimal leaning.  I have a 1974 Mooney 20C with a power quadrant and leaned my mixture back about 1" which is about 10% of my mixture cable travel range.  Since I plan to use 2G4 regularly, I plan to get up with an instructor soon and review proper leaning.  I am a 200 hour pilot with 100 in Mooney and as you might guess from my screen name left flying for a long time and came back 2 years ago.  Now one more dumb question, "what is the red box?"  I don't have an engine monitor and see only 2 cylinder for CHT and have a single EGT gauge I use for leaning in cruise.  The tips on here have been helpful.  I went back and reviewed my POH again it seems I was getting a book value ground role and climb rate (just lucky this time, I want to be smarter next time).

Hey Rusty,

You really should invest (I just sold an edm700 for $500) in a multi probe engine monitor.  The cylinder temps and egt’s And lean features are worth the price of admission.  Once probes are installed you can likely reuse for a “latest and greatest” at a later date.  You will NOT like flying without one once you have one.  I consider them “basic” for today’s flying.  I paid like $200 for a Gem 602 in my first plane.  NOT a big hit for a nice chunk of info.  GET ONE  

Edited September 10, 2020 by Missile=Awesome