In which situation is it crucial to re-evaluate de-icing procedures?

Re-evaluating de-icing procedures is particularly crucial in the event of equipment failure that interrupts operations. When equipment issues arise, the effectiveness of de-icing operations may be compromised. If the necessary de-icing machinery or materials are not functioning properly, there could be a risk of not adequately removing ice or contaminants from aircraft surfaces, which can lead to safety hazards during takeoff and flight.

In such scenarios, it's important to reassess the current de-icing strategy to determine whether alternative methods or equipment should be employed or if operations should be halted entirely until the malfunction is resolved. This ensures that safety protocols are maintained and that aircraft are free from contaminants that could affect their performance.

While visible contaminants, personnel readiness, and rising temperatures do play roles in the overall de-icing process, they are not as critical to immediately re-evaluating procedures as a failure in the equipment that serves the de-icing function.