Best High Altitude Take off Lean Procedure?

[Gary0747]

I have fuel flow and digital EGT/CHT and am looking for the best procedure for leaning prior to take off at altitudes above 3000 feet.   I have always leaned to around 1300 F EGT on cylinder number three at full throttle. Sometimes on take off roll.  Is there a better procedure?  

 

[AndyFromCB]

Percent of fuel flow based on your standard day, sea level max climb fuel flow is how I've always done it. Pull out your air pressure table, calculate percent of available air/oxygen, set mixture to that fuel flow on roll out.

[Piloto]

14 minutes ago, Gary0747 said:

I have fuel flow and digital EGT/CHT and am looking for the best procedure for leaning prior to take off at altitudes above 3000 feet.   I have always leaned to around 1300 F EGT on cylinder number three at full throttle. Sometimes on take off roll.  Is there a better procedure?  

 

I think it is a good procedure. But on climb keep an eye on EGT and CHT readings and verify open cowl flaps. CHT readings can increase quickly on the climb.

José

[carusoam]

Gary, how have you come to using 1300°F?

Leaning can be done using °F ROP, to standardize the discussion... Andy's method uses FF, so there isn't going to be a standardization using only a EGT...

As usual, discussing the actual EGT is nice, but very dependent on the installation.

The O uses the same procedure that we are discussing here, but has a blue box on the ship's EGT sensor.  The G1000 panel uses a white box to do the same thing.

The blue box is a range from 200-300°F ROP.  This gives good power for getting off the ground and climbing and maintains a fair amount of cooling at the same time.  As you climb through altitudes, the EGT needle falls out the bottom of the box. Use the red knob to adjust it to the top of the box.

Once you know how this works with your plane.  Andy's method of using FF is a quick method of getting to where you want to be.  Or set the mixture with one technique and verify the result with the other...

PP ideas, not a CFI...  Sharing the ideas...

Best regards,

-a-

[Oscar Avalle]

I flew out of a field that was at 4700 feet with density altitudes that reached 7 to 8k. Given the danger of high CHTs I preferred always to take off with full power and mixture full rich. On climb I then started to lean the mixture. 

[KLRDMD]

49 minutes ago, Gary0747 said:

I have fuel flow and digital EGT/CHT and am looking for the best procedure for leaning prior to take off at altitudes above 3000 feet.   

  I thought I read high altitude in the title 

[carusoam]

Ken,  Earlier today, 60°F was a cold start..! 

Best regards,

-a-

[AndyFromCB]

16 minutes ago, Oscar Avalle said:

I flew out of a field that was at 4700 feet with density altitudes that reached 7 to 8k. Given the danger of high CHTs I preferred always to take off with full power and mixture full rich. On climb I then started to lean the mixture. 

Doesn't that rob you of power to accelerate down runway? It's been a long, long time since I've flown a non-turbo engine, but I recall having much better results leaning than not leaning taking off in CO and WY when I had my Arrow.

[gsengle]

Full rich is too rich generally once you're up a couple of thousand feet msl... And I'd say not climbing is a worse threat than overheating during your takeoff run.


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[jetdriven]

Lean to target EGT on the takeoff roll. Dont fuss with getting it exact, just within ~50 degrees.  Above 1000', set it right on. 

Edited November 29, 2016 by jetdriven

[Gary0747]

10 hours ago, carusoam said:

Gary, how have you come to using 1300°F?

I use this because it is about 200 degrees ROP normally and is close to the EGT I see on take off roll while full rich at 600 foot altitude. 

[jetdriven]

Put the mixture about where you think it ought to be, go full power and set it just  rich of target EGT.  The EGT will be within 50° or so what it will stabilize at in just a few seconds. if Runway length is critical or you really do need the best performance from the airplane hold the brakes, do all this before moving.

Edited November 29, 2016 by jetdriven

[gsengle]

EGT is very quick you're thinking of CHT.


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[gsengle]

EGT I find is almost instantaneous.


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[Bob - S50]

I use 1300F on the EGT as well.  I know from experience that just like Gary, that's what I normally see full rich at SL and I also know the peak EGT on my plane is a bit over 1500F.

[Bob - S50]

Just now, Hyett6420 said:

doesn't peak EGT vary with altitude though?  I have found that the EGTT at 4000 feet is less than the EGT at 7000 feet.

Andrew

Doesn't seem to vary much on my plane.  Usually around 1520 or so regardless of the altitude.

[gsengle]

It varies once you get higher than the altitude where you can generate peak manifold pressure to be sure...


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[Joe Zuffoletto]

My RV-8 is carbureted and normally aspirated, and my leaning procedure is quite simple: at the end of the high-RPM portion of my run-up I slowly pull the mixture back until the RPM peaks and then starts to decrease again; then I move the mixture knob forward about 1/2" to set the mixture just on the rich side of peak RPM. Next, I slowly pull the throttle to idle to do my idle check, and at my lean mixture setting the engine idles very smoothly. BTW, if I try an idle check with the mixture full rich, the idle is very rough.

On climb-out I need to keep the nose down and airspeed up to keep the CHT's in the green. The RV has no cowl flap.

This is the same procedure I used for my old Archer II (pretty much the same engine), and it has always worked well.

Field elevation at my home drome is 5,800' and DA is typically above 7,000'.

[Oscar Avalle]

Doesn't that rob you of power to accelerate down runway? It's been a long, long time since I've flown a non-turbo engine, but I recall having much better results leaning than not leaning taking off in CO and WY when I had my Arrow.

Indeed it does, but my runway was about 9500 feet long...so I preferred to trade off runway length to CHT.

On climb the issue was dicier, on very hot days (80+ degrees) I had to manage the climb rate very carefully...on several occasions I had to level off to manage the CHTs and oil temp. Climb rate was never stellar, but always within a reasonable range.

When I had to take off from shorter fields I always tried to leave in the morning or late PM. Also, at that point I leaned on the ground, but again on climb I sometimes had to enrich the mixture to manage temperatures.

Obviously, given that I was flying out of a valley, surrounded by mountains and volcanos, I had to have excellent situational awareness to avoid running into something, but that is a different story.

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[carusoam]

1) most of us are discussing the 'target EGT' method.

2) some of us have come to a short cut to get there based on experience in their specific machine.

3) the short cut is often needed to get to the target, because the runway length is short compared to the response time of the EGT sensor.

4) if your EGT sensor takes longer than a few seconds, consider getting fast response sensors...  a TC by itself is very reactive.  A thickly jacketed TC is well protected, but terribly slow to respond. 

5) know that EGT changes are actually very fast and stabilize very quickly in a FI engine. CHT responses takes much longer...

6) An example of quick EGT responses, think of the saw tooth chart patterns that are an indication of a leaking valve malfunction.

Things that come to the mind of an ordinary PP, not a CFI or mechanic...

Best regards,

-a-

[KLRDMD]

18 hours ago, carusoam said:

Ken,  Earlier today, 60°F was a cold start..! 

60º IS a cold start ! 

[KLRDMD]

5 hours ago, Oscar Avalle said:

On climb the issue was dicier, on very hot days (80+ degrees) . . .

80º are very hot days, I see . . .

[Oscar Avalle]

8 minutes ago, KLRDMD said:

80º are very hot days, I see . . .

Yes, 80 are very hot days... specially at 4700 feet... density altitude 7500 feet... air density only .06 lb/ft3. So no wonder that the engine had a hard time swallowing enough air to keep the engine cool...

[KLRDMD]

21 minutes ago, Oscar Avalle said:

Yes, 80 are very hot days... specially at 4700 feet... density altitude 7500 feet... air density only .06 lb/ft3. So no wonder that the engine had a hard time swallowing enough air to keep the engine cool...

Around here hot doesn't start until 110º, very hot would have to be nicely over 115º. Flagstaff routinely has density altitudes over 10,000 ft in the summer. Some people call 4,000 ft peaks mountains too so I guess it is all a matter of perspective.

[Oscar Avalle]

2 hours ago, KLRDMD said:

Around here hot doesn't start until 110º, very hot would have to be nicely over 115º. Flagstaff routinely has density altitudes over 10,000 ft in the summer. Some people call 4,000 ft peaks mountains too so I guess it is all a matter of perspective.

Yes, everything is relative...My volcanos were about 9k tall...