When de-icing engines, the spray angle should be directed at what part using a mist/fog spray pattern?

The correct choice emphasizes that when de-icing engines, it's important to aim the spray at the leading edge of the engine cowling. This area is crucial because it is where ice accumulation can occur, potentially affecting engine performance and aerodynamics. Applying the de-icing fluid in a mist or fog pattern helps ensure even coverage and reduces the risk of ice formation, which could lead to serious operational issues.

The leading edge of the engine cowling is particularly sensitive, as ice buildup in this location can disrupt air intake and negatively impact engine efficiency. Aiming the spray here ensures that the most critical areas are treated effectively.

Other options, while they may seem relevant in different contexts, do not directly address the primary concern of preventing ice buildup on the engine's intake, which can lead to engine performance issues or failures.