Shock cooling (aircraft engines) prevention procedures

Dad babied his cherished Skylane. He never let me fly it solo. (He did endorse my log book for ‘high performance’ aircraft.) One thing he made certain of was not to ‘shock cool’ the engine. That is, he didn’t want the engine temperature to come down to quickly and result in a stuck valve or cracked cylinder.

The Wikipedia article says there is controversy about shock cooling, and many consider it a myth. It’s been a quarter century since I flew the 182, and I don’t remember the descent procedure to prevent shock cooling (if it exists). I remember slow reduction of the throttle, carb heat on, and cowl flaps closed.

Can someone remind me of the procedures?

(And no, I’m not going to rent a Skylane. If I were, I’d receive instruction at the time. :wink: )

Shock cooling is real according to articles written by reputable airplane mechanics and engineers that I have read. There is an article about is in this month’s Plane and Pilot magazine. It certainly isn’t limited to planes like a 182. Almost any plane with a reciprocating engine can be shock cooled or heated. There is a small risk of cracking a cylinder during extreme scenarios but everything I have read indicates the problem is usually more subtle and insidious. The real threat of rapid thermal cycling is to the service life (TBO) of the engine. Shock cooling introduces microscopic cracks in the engine parts and greatly speeds up wear on the engine.

I have never flown a Cessna 182 so I don’t know the exact procedure for avoiding shock cooling in that specific plane but the basic idea is the same for all similar planes and even automobiles. You gradually change power and make more gentle throttle maneuvers rather than suddenly advancing or pulling back the throttle whenever possible. You also try to avoid rapid, power-off altitude changes or prolonged full-throttle climbs.

I haven’t flown a big carby engine, only injected so don’t know about use of carb heat. In the Shrike which had IO540 engines I think, we just had cowl flaps open for climb and closed for descent. Descending at 500’/min using a descent profile of 5 NM per 1000 feet generally allowed for a gradual reduction in power throughout the approach.

Our Pitts Special had a Lycoming IO360 engine (BTW “I” for injected and “O” for opposed) and no cowl flaps. We flew 12-15 minute flights in it constantly day in day out using full power for take-off and 25"/2500 RPM for aerobatics. Routine was take-off and climb to 3000’ then aerobatics directly overhead the airfield. power stayed constant at 25"/2500 during aeros, i.e., no reduction in power for dives or anything. Height reduced to 1500’ during the routine then straight into the circuit with power coming back to idle on finals. I flew it for 4 years and never had problems with cracked cylinders or poor engine life.

Used to fly a Cessna 310 with IO 520s. Seem to recall figuring on 1" MP per minute while on descent. It’s been a shockingly long time since I’ve flown a recip.