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What exactly is the winter baffle in parentheses, where is it used and what does it do? The image is taken from the preflight checklist of the DA40NG aircraft.

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They are little plates that block off part of the air intakes for winter operations. With the really cold air, the normal flow velocity provides way too much cooling, so to limit the effect, you block part of the flow off. I don't know what the air intake on the wing is for, but you usually see baffles on cowling cooling intakes on air cooled engines for cylinder cooling and oil cooler flow. Otherwise you will never be able to get the cylinders/oil up to operating temperature if it's too cold outside.

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  • $\begingroup$ Based on what you wrote, I assume that this piece is used in regions with very cold weather conditions. $\endgroup$
    – pilot162
    Commented Mar 9, 2023 at 5:18
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    $\begingroup$ Yes, generally if you are going to be operating below 20F or maybe 30F regularly. In northern US or Can you'll install them in Nov and take them off in April. The airplane will have a "winterization kit" with the baffle plates. The most critical item is an alternate exit for the engine breather tube, usually a permanent feature, which can freeze over and if there isn't a secondary outlet to act like a pressure relief (sometimes just a sharkmouth slit in the pipe), the engine will force oil past the crank seals and you'll have oil over over the windshield, and eventually, a quiet engine. $\endgroup$
    – John K
    Commented Mar 9, 2023 at 14:27

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