Shock cooling
When I learned to fly, in 1960, the term shock cooling just wasn't heard. I'm sure I never heard it once. I was taught that the reason you rev the engine occasionally when flying throttled back, perhaps during a PFL or a glide approach, was to prevent the plugs oiling up in our inverted, in-line engines. The only time we consciously managed our engine temperatures was immediately after starting and when we cooled the engine after landing, immediately prior to shut-down.
The engines in use then were the air-cooled, in-line, inverted, four-cyllinder de Havilland Gypsy Major and Blackburn Cirrus Minor II. And the majority of our instructors then were ex-wartime military pilots with extensive experience on a whole variety of engines including big air-cooled engines.
When I returned to flying a couple of years ago, I encountered this concern with shock-cooling for the first time. And the concern was real. I know for a fact that today gliding clubs in particular do have a constant problem with cracked cyllinders, caused after dropping the tow and returning as quickly as possible to the launch point to collect the next tow.
I wonder whether the current concern with 'shock cooling' could have something to do with the fact that for most of the last forty years private flying has been utterly dependent on the Lycoming and Continental engines. I wonder if these engines are more susceptible to variations in temperature than the engines we used to use.
Broomstick.