A landing gear controller for an aircraft, the controller being operatively connectable to a landing gear extension and retraction system, the landing gear extension and retraction system comprising: a landing gear, a landing gear actuator; a landing gear sensor to indicate a position of the landing gear; a landing gear bay door; and a landing gear uplock hook, the controller, in use, being configured to: issue a release signal to the landing gear bay door, to move from a closed position to an open position; send a signal to the landing gear actuator to extend the landing gear from a retracted position to an extended position; receive a confirmation signal from the landing gear sensor that the landing gear is in the extended position; and measure an extension time for the landing gear, the extension time comprising a time between issue of the release signal and receipt of the confirmation signal, and characterised in that the controller is configured to: determine if the measured extension time is less than a predefined extension time; and if the measured extension time is less than the predefined extension time, provide a warning signal to indicate potential failure of the landing gear uplock hook to hold the landing gear in a retracted position. a landing gear, a landing gear actuator; a landing gear sensor to indicate a position of the landing gear; a landing gear bay door; and a landing gear uplock hook, the controller, in use, being configured to: issue a release signal to the landing gear bay door, to move from a closed position to an open position; send a signal to the landing gear actuator to extend the landing gear from a retracted position to an extended position; receive a confirmation signal from the landing gear sensor that the landing gear is in the extended position; and measure an extension time for the landing gear, the extension time comprising a time between issue of the release signal and receipt of the confirmation signal, and characterised in that the controller is configured to: determine if the measured extension time is less than a predefined extension time; and if the measured extension time is less than the predefined extension time, provide a warning signal to indicate potential failure of the landing gear uplock hook to hold the landing gear in a retracted position. issue a release signal to the landing gear bay door, to move from a closed position to an open position; send a signal to the landing gear actuator to extend the landing gear from a retracted position to an extended position; receive a confirmation signal from the landing gear sensor that the landing gear is in the extended position; and measure an extension time for the landing gear, the extension time comprising a time between issue of the release signal and receipt of the confirmation signal, and characterised in that the controller is configured to: determine if the measured extension time is less than a predefined extension time; and if the measured extension time is less than the predefined extension time, provide a warning signal to indicate potential failure of the landing gear uplock hook to hold the landing gear in a retracted position. determine if the measured extension time is less than a predefined extension time; and if the measured extension time is less than the predefined extension time, provide a warning signal to indicate potential failure of the landing gear uplock hook to hold the landing gear in a retracted position.