Ground leaning the DA40

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I have a 05 DA40 G1000. I read your article about engine management
and was hoping you could be more specific on how to do the ground
leaning before taxi out or after landing. Is it appropriate to use
the Lean Assist? Anything in particular to watch for?


-- George Swetlitz, March 26, 2006


I didn't have Lean Assist on my DA40 so I didn't use it! For ground leaning you don't have to worry about being too lean because the engine is not really producing any power. So just pull the mixture back at least halfway. It should be set so that if you pull back any farther the engine will begin to run rough (or quit!).

-- Philip Greenspun, March 26, 2006

I have an early 2006 DA40. I find Lean Assist to be of no value for ground leaning. I rely on Deakin's dictum: "Lean brutally on the ground." You can do your engine no damage this way, and it prevents you from trying to take off too lean if you forget. That's because the aggrssively leaned engine will stall at full throttle.

I lean aggressively right after starting and right after landing. On my ship, that means more than halfway back on the mixture lever.

Advantages: slightly lower fuel burn, less risk of plug fouling, slightly faster oil temp rise, and elimination of risk of taking off too lean.

HTH, Tom

-- Tom Cooper, March 27, 2006

Tom is right. An overly lean mixture is only bad when you are producing a lot of power (I would say over 30-40%). On the ground, when you overly lean, symptoms will be rough running followed by a stalled engine. That means it too lean. Richen it up a bit. This will depend on temp somewhat too. On a cold morning, fuel is less likely to vaporize and the mixture will have to be a bit richen than on a hot summer day. On my car, I have control over my mixture. I lean for as much economy as possible during cruise/light throttle events. AFR of 15 if possible (or leaner, but it is hard to get the mixture lit off leaner than that). You do notice some hesitation sometimes with those lean settings. Full-throttle is rich and safe (11.5:1 under boost.

-- Matthew Greenlaw, April 17, 2006