🔍 Key Concepts

• How condensation forms inside partially filled fuel tanks • Effect of tank level (high vs low) on the air space (ullage) above the fuel • Role of relative humidity in creating water droplets on cool tank surfaces

💭 Think About

• Think about which situation gives the largest air space above the fuel and what happens when that moist air cools down at night or with temperature changes. • Consider whether high or low humidity air will deposit more water when it cools and condenses on the inside of the tank. • Ask yourself: in which combination of tank level and humidity will the most moisture repeatedly enter and leave the tank and end up in the fuel?

✅ Before You Answer

• Identify the condition that creates the greatest volume of moist air above the fuel inside the tank. • Determine when the dew point is most likely to be reached, causing water to condense on internal tank surfaces. • Confirm which option would lead to the most frequent or heaviest condensation over time, not just in a single event.