Lean of peak

[Hans]

Question:
I have a DA40 with 350hrs, 2004, game injectors and fine wire plugs. I normally fly 1800rpms under 5000ft and can fly at 4.9 gph...my oil temp rind at 161 and my hottest CHT is around 310....but when I depart I always have to keep an eye on my CHT which will quickly climb to 400 if I don't manage the speed...any thoughts
Thx

[Charles]

Approaching 400F in climb is normal, for me anyway. But 1800 RPM in cruise seems low to me and probably not an rpm with which you would want to fly with more than 50-60% power which is probably what you're doing if only burning 4.9gph.

What is your LOP question?

[Hans]

Sorry that's at 40 percent power, I am never in a hurry enjoy it to much..is lean of peak better at low or high altitudes ?
Thx

[CFIDave]

Most DA40 can't fly "lean of peak" (LOP) because the IO-360 engine operates too roughly. Your airplane may be an exception with GAMIjectors installed -- if you've been able to completely balance fuel flows across the injectors.

I don't think high vs. low altitude matters very much in trying to fly LOP. If you fly above 7000 feet, operating rich of peak at any power level is just fine because the engine can't make more than 75% power.

[Chris B]

when I depart I always have to keep an eye on my CHT which will quickly climb to 400 if I don't manage the speed...any thoughts

Hi Hans -

Airspeed is key to managing CHT. I typically climb at ~90 kts IAS until at least 7k.

Also, check for baffling leaks. Even seemingly small openings can significantly reduce cooling efficiency. Prime culprits include: 1) the seal between the cowl & top baffles, & 2) gaps between the composite shroud and the engine case (particularly near the spinner). Both are easily fixed with RTV.

Are all of your CHTs similar (w/in ~20F)?

Chris

[Hans]

Thx for the great replies. You are right, I struggle to fly LOP because you can hear the engine start to choke, so I can fly "peak"...also taking advantage of the wind direction, with a nice tailwind I will fly 1800 rpm....against 2200...at 1800 CHT are around 310.....at 2200 around 340 all very close in numbers around 5-8 degree difference ...still learning a lot...climb is 75 but that does not provide enough cooling, so I always have to pitch down....how long do you guys keep your TO flaps on ??
THX AGAIN

[Chris B]

how long do you guys keep your TO flaps on ??

80 kts IAS.

[waynemcc999]

Retracting takeoff flaps... when I first got my 2008 DA40 I was only comfortable retracting at 75 KIAS and 600'+ AGL. Now I retract (and simultaneously pitch up a bit) progressively sooner, say 200'-to-300' AGL.

[CFIDave]

In a DA40 I usually climb at 90 knots, to provide sufficient engine cooling, and so I can see other traffic over the nose of the aircraft.

I raise T/O flaps as soon as I reach pattern altitude or clear an obstacle. The plane climbs better with flaps up.

[Antoine]

Hans: my experience of the DA40 engine is that you need to "listen" to it. I don't know how you make it run smoothly at 1800 RPM, I can't do that. My lowest RPM is typically 2250.
And I think Dave's advice on climb is spot on. If you climb slower than 90 knots you will find yourself with unnecessary overheating issues. Get to your cruise altitude quick, it is good for your engine and safer in case you need to do an engine out landing.
The DA40 is not a cub. Just make sure you don't fly it TOO slow and if you have some extra knots you don't need, I could use them