Final answer:
To clear an aircraft engine during a glide, the pilot temporarily increases power, which burns off unburned fuel and oil residues. However, the provided information seems to relate to rocket engines, which are not cleared in the same way as aircraft engines. Consultation of the operating manual is essential for specific guidelines.
Step-by-step explanation:
During a prolonged glide in aviation, it's important to occasionally clear the engine. This is done to prevent fouling of the spark plugs and to ensure that the engine remains ready for a powered-up transition if needed. To clear the engine, a pilot briefly increases the engine's power to a higher setting before returning to the glide power setting. This process burns off any unburned fuel and oil residues that could lead to engine problems.
The information provided about engines using liquid fuel/oxidant mixture and solid mixture seems to refer to rocket engines, which operate on different principles. Rocket engines, especially in the context of space flight, are not typically 'cleared' during operation in the same way aircraft engines are. The first engines mentioned, igniting at 3 seconds with a green flame, utilize a liquid fuel/oxidant mixture. The second set of engines, igniting at 4 seconds with a yellow flame, use a solid mixture. The color of the flame indicates the type of propellant being burned.
However, if the question is indeed about aircraft engines, it's important to consult the aircraft's operating manual for specific procedures for engine management during flight. In general, clearing an aircraft engine involves increasing throttle to a specified power setting, holding it for a certain number of seconds, and then returning to the previous throttle setting.