Aah! Temperature compensation of the altimeter aneroid capsule. Many a cup of tea went stone cold at Epsom Square as victims, er, candidates, struggled to describe its operation to their Airworthiness Surveyor inquisitors.
The problem was, different books described two different versions and one of them was wrong - the one written by an Airworthiness Surveyor [whose name sounds like a device used by artists]!
