PPRuNe Forums - View Single Post - Q1. PFLs in Fuel Injected engines, and 'warming' the engine?
Old 23rd May 2010, 19:35
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IO540
 
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"Shock cooling" is an old topic, with a number of religious camps, and very little real data

The best data I am aware of (from a glider towing operation) is that it is a risk only if the CHT is above a certain figure. If one makes an effort to cool the engine down gradually before the event which requires a sudden power reduction, then it is not a risk.

This is consistent with PPL flying school experience - because they fly full-rich most of the time so the cruise CHTs are pretty low, so they rarely crack cylinders.

The magic CHT value is unknown but it is probably about 300-350F. Much above 400F, aluminium starts to weaken and above 450F it is pretty weak.

When I was doing checkrides in my TB20, I would tell the instructor that a simulated engine failure is not to be done unless the engine was cooled first, by crusing at say only 18" and full-rich.

The PPL training practice of briefly increasing power to "warm the engine" is IMHO bollox. If one had a CHT gauge, one would see that the brief power burst do more or less nothing in CHT terms.
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