Re BPF 'This switching off of Carb heat on short final seems to be a unique to British flight training practice that seems to have been mindlessly passed down through the generations.
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I got my licence on the Australian syllabus and was taught to keep carb heat on until on the ground. When I converted my licence to a UK one, I was told to switch carb hear off at 200'. I've since seen this requirement documented in the order book of a flying club.
I've been following this rule, however a few months ago, climbing out in a Cub behind a C90, I got carb ice at around 300'. I pulled carb heat and recovered power without incident but with a lesson being learned: leave carb heat on until on the ground.