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Loose alternate air door on Continental IO 520L

During routine mx the shop found the alternate air door on our C210L to be loose, the spring had failed. In this installation, alternate air is an automatic system. Speaking to the last pilot who flew the airplane before mx (on a longish x-country), he didn’t notice any anomalies.

So, here’s the question to the wise: what would / should be the symptoms if this happens?

Increased engine wear in dusty conditions? Longer life for induction air filter? Assuming not a carb engine so no air temp change.

EGPE, United Kingdom

Maoraigh wrote:

Assuming not a carb engine so no air temp change.

Correct. I’m trying to figure out what would alert a pilot to that malfunction.

I’ve never seen a C210 up close- where exactly is the air filter located?
The injected engine of our PA28-180R has automatic alternate air as well, but even if it were carburetted, I’d assume it wouldn’t change notably, because the fresh air is already flowing over the port cylinder bank prior to entering the filter. So it isn’t exactly cold, and the alternate air just takes air from a different part from within the cowling. The pro is, it won’t ingest so much dirt, because it is kind of shielded.

We have a lever for manually opening the door, though, and checking it is part of the run-up. I assume you could possibly feel if the force needed to move it is different if something broke.
But the change might be small, and probably not noticeable to someone who doesn’t fly the plane regularly.
Sorry, this is the only thing I could think of.

EDXN, Germany

All I can think of is a slight increase in maximum available MP, but I don’t have a clue by how much, it could be barely noticeable except perhaps if turboed and at high altitude

LESB, Spain
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