After what event does a pre take-off contamination check occur?

The correct answer is based on the procedures followed in aviation regarding de-icing and anti-icing practices. A pre take-off contamination check is crucial for ensuring the aircraft is free from substances that could affect its aerodynamic performance and safety during takeoff.

This check is particularly relevant after the holdover time, which is the period during which anti-icing fluids remain effective under specific weather conditions. Once this time frame has been exceeded, it's necessary to conduct a contamination check to assess whether the protective measures have remained intact. If any contamination is detected or if there is uncertainty about the effectiveness of the de-icing treatment, further measures need to be taken to prepare the aircraft for safe departure.

Understanding this aspect of pre-flight procedures emphasizes the importance of maintaining safety standards in aviation, particularly in adverse weather conditions.