An aircraft comprising a landing gear assembly comprising a landing gear mounted for movement between a deployed position and a stowed position in a landing gear bay, a capture pin mounted on the landing gear, an uplock for locking the landing gear in the stowed position, the uplock including a hook configured to move between (a) a closed position, in which the hook retains the capture pin in a captured position thus preventing the landing gear from moving away from its stowed position and (b) an open position which permits movement of the capture pin from the captured position thus allowing the landing gear to move away from its stowed position, and an uplock hook sensor which provides an output signal indicating if the hook is in its closed position, a proximity detector comprising a target and a sensor (152, 154), the target being mounted in the landing gear bay such that the sensor (152, 154) detects the target when the landing gear is stowed with the capture pin in its captured position, a signal processing unit arranged to receive an input from the uplock hook sensor, to receive an input from the proximity detector, and to produce an output indicating if both the hook is in its closed position and the capture pin is in its captured positon, characterised in that the sensor (152, 154) of the proximity detector is mounted on the structure of the landing gear and the target of the proximity detector is formed by part of the uplock hook. a landing gear assembly comprising a landing gear mounted for movement between a deployed position and a stowed position in a landing gear bay, a capture pin mounted on the landing gear, an uplock for locking the landing gear in the stowed position, the uplock including a hook configured to move between (a) a closed position, in which the hook retains the capture pin in a captured position thus preventing the landing gear from moving away from its stowed position and (b) an open position which permits movement of the capture pin from the captured position thus allowing the landing gear to move away from its stowed position, and an uplock hook sensor which provides an output signal indicating if the hook is in its closed position, a hook configured to move between (a) a closed position, in which the hook retains the capture pin in a captured position thus preventing the landing gear from moving away from its stowed position and (b) an open position which permits movement of the capture pin from the captured position thus allowing the landing gear to move away from its stowed position, and an uplock hook sensor which provides an output signal indicating if the hook is in its closed position, a proximity detector comprising a target and a sensor (152, 154), the target being mounted in the landing gear bay such that the sensor (152, 154) detects the target when the landing gear is stowed with the capture pin in its captured position, a signal processing unit arranged to receive an input from the uplock hook sensor, to receive an input from the proximity detector, and to produce an output indicating if both the hook is in its closed position and the capture pin is in its captured positon, characterised in that the sensor (152, 154) of the proximity detector is mounted on the structure of the landing gear and the target of the proximity detector is formed by part of the uplock hook.