Final answer:
The aircraft's main landing gear is held in the up-and-locked position primarily by mechanical locks, uplock mechanisms, and hydraulic systems to ensure it stays secure during flight.
Step-by-step explanation:
The main landing gear of an aircraft are held in the up-and-locked position by a combination of mechanical locks, uplock mechanisms, and/or hydraulic systems. When the gear is retracted upon take-off, these components work together to ensure that the gear remains securely in place during flight. The mechanical locks engage to prevent the gear from extending unintentionally due to gravity or in-flight maneuvers. Similarly, uplock mechanisms typically include hooks or latches that hold the gear up until the pilot or automatic systems release them for the landing procedure. Furthermore, the hydraulic system may employ pressure to maintain the gear in the retracted position until it is time to land.