Leaning for High Altitude Take off

[Tony__L]

I am interested to know the different ways (techniques) you guys lean for high altitude take offs. I live at the coast and have little opportunity or need for this. Also, at what altitude do you believe it becomes necessary to lean for take off.

In case it helps I have a 1967, M20F Executive.

Thanks

Tony

[larryb]

I started with a full rpm runup to set the mixture at target sea level EGT. Then I learned that was 14.5 GPH for me at 5900 feet. So I set it by position now and fine tune to 14.5 gph in the roll if I am off.

[Joe Zuffoletto]

Takeoff in the M20TN is always full rich (it's a turbo), but in my RV-8, which has a Lycoming O-360, I run it up to 2,000RPM, then lean until the RPM maxes out, then nudge it just a little bit rich of that point. We do the same thing in the Xtreme Decathlon, which has a Lycoming IO-390. This is operating out of Denver Centennial, which is 5,800' MSL.

[Robert C.]

I learned to fly in an Archer based in Utah, flying out of airfields with field elevations between 3000 and 5200 ft.

 

The instructor taught me to lean till the engine (O-360) stumbled and then enrichen to get to max power. Should come out to about the same as what Joe described. The bottom line is to lean for best power.

 

Necessary? Well, necessary and practical are different things. Practically speaking i don't really think about it unless the field elevation is above 1000ft and even then only on hot days and with a short runway.

[KSMooniac]

larryb described the optimal way to do it, and make sure you have the mixture set "rich enough" to stay out of the red box of mixture settings.  Leaning for best power >75% isn't a great way to do it in terms of the highest internal cylinder pressures and CHTs.  Using the Target EGT Method will make sure you are >100 dF ROP and out of the red box.

[bonal]

Oh to have a complete monitoring system. I have many high DA days in my summer. and like the others I run to 2000 lean to just rough then back for best RPM usually I get about 100 to 200 more than full rich so 2100 to 2200 RPM after adjusting. then a close watch on EGT and CHT as i climb. When I start out this way I usually dont have to lean further as I reach cooler air until about 4000ft AGL. seems to work OK for me.

[Tony__L]

larryb described the optimal way to do it, and make sure you have the mixture set "rich enough" to stay out of the red box of mixture settings.  Leaning for best power >75% isn't a great way to do it in terms of the highest internal cylinder pressures and CHTs.  Using the Target EGT Method will make sure you are >100 dF ROP and out of the red box.

Interesting, I have heard about the red box before but only in passing conversation. Where can I find some literature on this topic?

[Tony__L]

Thanks for the responses! I will try them out the next time I travel uphill

[The-sky-captain]

Interesting, I have heard about the red box before but only in passing conversation. Where can I find some literature on this topic?

http://www.advancedpilot.com

[Lood]

Tony, for me, target EGT seems the best method when I take off from higher alt airfields than what I'm used to. That said, my F seems to perform very well over quite a wide mixture setting. The thing to watch out for is certainly red box, as mentioned above, but also keep an eye on the CHT's. I find that whenever I take off with the mixture not rich enough, the CHT's will shoot up very quickly.

From my 4000ft home field, I need a fuel flow of around 15 - 16gal/hr to keep temperatures nice and cool. As I climb, I lean as per target EGT and I rarely see any CHT's higher than 350 deg F during the climb.

[aaronk25]

Took of from Leadville with a DA of 12,600. Position at very end of runway, stand on the brakes, full throttle, normally my target is 1270-1290egt at full rich at sea level so I leaned until I hit 1270 then continued to lean to find peak which was around 1420 (normally higher at lower altitudes) so I leaned for max power which is 80 ROP, which was 1340.

Given the DA, didn't need to worry about red box. Fuel flow was around 11gph.

Long roll...30 gallons on board and 1 pax...at about 3500 ft of roll the wheels left the ground.

Just another way of doing it when a takeoff requires every ounce of power the engine will create. There is no better setting than 80rop for making power, just watch the redbox.

[Marauder]

Took of from Leadville with a DA of 12,600. Position at very end of runway, stand on the brakes, full throttle, normally my target is 1270-1290egt at full rich at sea level so I leaned until I hit 1270 then continued to lean to find peak which was around 1420 (normally higher at lower altitudes) so I leaned for max power which is 80 ROP, which was 1340.

Given the DA, didn't need to worry about red box. Fuel flow was around 11gph.

Long roll...30 gallons on board and 1 pax...at about 3500 ft of roll the wheels left the ground.

Just another way of doing it when a takeoff requires every ounce of power the engine will create. There is no better setting than 80rop for making power, just watch the redbox.

 

You forgot the part about changing underwear afterwards If I watched 3000'+ of runway go by -- and I wasn't airborne, I would be changing mine

[aaronk25]

You forgot the part about changing underwear afterwards If I watched 3000'+ of runway go by -- and I wasn't airborne, I would be changing mine

No kidding. I knew it would fly, but I also knew that rotating to soon and high angle of attack climb out would create additional drag so I built a extra 7kts on the ground and "tip toed" it off the runway and established a 100fpm climb out until air speed was north of 100kts, then steepened the climb.

I brought extra undies with just in case though

Turbo would have been wonderful!

[KSMooniac]

Leadville is an experience!  Mine was similar to Aaron's, but I was solo and had ~ 13,500 DA at the time.  3000' of ground roll, and a slow climb rate as expected.  Fortunately the terrain around Leadville is pretty benign so you don't have to be in a hurry to climb, unlike Aspen!  

[midlifeflyer]

You forgot the part about changing underwear afterwards If I watched 3000'+ of runway go by -- and I wasn't airborne, I would be changing mine

 

One gets used to it.

[midlifeflyer]

No kidding. I knew it would fly, but I also knew that rotating to soon and high angle of attack climb out would create additional drag so I built a extra 7kts on the ground and "tip toed" it off the runway and established a 100fpm climb out until air speed was north of 100kts, then steepened the climb.

Another technique is to do a modified soft field takeoff, get the airplane into the air early, put the nose down and accelerate in ground effect until reaching climb speed

[201er]

larryb described the optimal way to do it, and make sure you have the mixture set "rich enough" to stay out of the red box of mixture settings.  Leaning for best power >75% isn't a great way to do it in terms of the highest internal cylinder pressures and CHTs.  Using the Target EGT Method will make sure you are >100 dF ROP and out of the red box.

Thing is, if you're high enough to need to lean for power, then you will be making less as well. That means you can be less ROP than for sealevel takeoff relative to peak.

[Marauder]

Thing is, if you're high enough to need to lean for power, then you will be making less as well. That means you can be less ROP than for sealevel takeoff relative to peak.

Oh my! A Mike visit! Or was it a hit and run? Where you been? No weekend lunches, no parrot visits, nothing!

BTW - I met your friend Philip over here. Remember him?

[midlifeflyer]

Thing is, if you're high enough to need to lean for power, then you will be making less as well. That means you can be less ROP than for sealevel takeoff relative to peak.

 

Yes and no. First, this isn't brain surgery. If you normally don't lean for takeoff at altitudes below a certain level, say below 3000 D-Alt, then you know you have quite a bit of leeway in terms of what is optimum. Second, there is a bit more of a tendency for aircraft to overheat at higher density altitudes, perhaps because so much less power is being used to preform the same task - just like the proverbial 90-lb weakling will sweat more moving a boulber than a football linebacker. And, as we know, one of the things fuel does is help cool the engine.

 

So, it's pretty common at high density altitudes to lean for an approximation of best power (using various techniques based on the experience level of the pilot with high density altitudes and the equipment) and then enrichen a bit more for better engine cooling.

[Oscar Avalle]

My field is At 5000 feet with density altitudes that are often around 8000 to 9000. I run up at 2000 rpm and lean to target EGT. The I enrich it a little bit to ensure that the engine is cooled. The main problem I have is high temperatures and CHT.

[adamsboomer]

My DA is usually around 7K.  I run up at 2000rpm, lean for peak RPM then reduce by leanness by half (if knob pulled out 2", I push back in 1")

[M016576]

You forgot the part about changing underwear afterwards If I watched 3000'+ of runway go by -- and I wasn't airborne, I would be changing mine

You ever look out the window during takeoff roll for a CRJ700? I swear, those things don't get airborne until the last brick...

Rolls greater than 2000' tend to get me wondering in the mooney, too

[M016576]

Double post

[midlifeflyer]

You ever look out the window during takeoff roll for a CRJ700? I swear, those things don't get airborne until the last brick...

Rolls greater than 2000' tend to get me wondering in the mooney, too

 

Rolls substantially greater than  the POH performance tables get my attention. If we fly in areas with approximately the same elevation, we have a sense of what that is, but when we go elsewhere...

[Chimpanzee]

However what is the target EGT ? I haver heard it referred to but what actually is the value or how do I determine it for my C model with O 360 engine?
Thanks to my Insight G1 monitor, I can see both EGT and CHT.

Cheers
Norbert