What is the protocol if contamination is observed during pre-flight checks after de-icing?

When contamination is observed during pre-flight checks after de-icing, the correct protocol is for the aircraft to undergo additional de-icing procedures before departure. De-icing is crucial for safe flight operations, as the presence of ice, snow, or other contaminants can significantly impact the aircraft's aerodynamic performance and increase the risk of accidents during takeoff and flight.

In this context, ensuring that the aircraft is free from any contaminants is essential for maintaining safety standards. Additional de-icing procedures will remove any remaining ice or snow and ensure that the critical surfaces of the aircraft, such as wings and tail, are clear and ready for safe operation. By reaffirming that the aircraft is adequately de-iced before takeoff, flight crews can mitigate risks associated with potential loss of lift or increased drag.

The other choices reflect responses that are less appropriate when dealing with contamination. Grounding the aircraft for inspection may be excessive unless indicated by severe contamination or other indicators. Taking off with caution or dismissing minor contamination can compromise safety, as even small amounts of ice can affect aircraft performance. Therefore, additional de-icing procedures are necessary to uphold safety protocols and ensure the aircraft is fully prepared for departure.