What will happen in the event of a hydraulic leak?

In the event of a hydraulic leak, the landing gear will typically fall due to the loss of hydraulic pressure that is necessary for retracting or maintaining the gear in the up position. Many aircraft landing gear systems operate using hydraulic fluid, which applies pressure to mechanisms that control the positions of the landing gear. When there is a hydraulic leak, this pressure is lost, and the weight of the landing gear will generally cause it to drop down into the extended position.

This situation aligns with the design of many aircraft, where the landing gear is engineered to extend automatically if there is a significant loss of hydraulic pressure, ensuring that the aircraft can land safely. The other choices do not align with standard aircraft systems; the landing gear locking in place or remaining up would require constant hydraulic pressure, which the leak has compromised. Thus, the correct understanding is that, under a hydraulic leak, the landing gear indeed will fall to ensure that the aircraft has a safe method for landing.