An emergency brake system for an aircraft comprising: a modulating emergency/parking brake valve (78; 120) in fluid communication with and disposed between a pressure source and a wheel brake (14a, 14b), the emergency brake system being operative in a first stage to provide a moderate amount of brake pressure to the wheel brake (14a, 14b) and a second stage to provide a greater brake pressure to the wheel brake (14a, 14b); and a lever assembly (92; 112; 312) operatively connected with the brake valve (78; 120), the lever assembly (92; 112; 312) including a handle (116; 316) being movable between a non-actuated position where the wheel brake (14a, 14b) is disengaged and a fully-actuated position where the wheel brake (14a, 14b) is fully engaged, wherein the brake pressure provided to the wheel brake (14a, 14b) through the brake valve (78; 120) is configured to be provided according to a position of the handle (116; 316); a lock mechanism (150; 330, 350) operatively connected with the handle (116; 316) to obstruct the handle (116; 316) from moving from an intermediate position, which is between the non-actuated position and the fully actuated position, towards the fully actuated position; and an unlock mechanism disposed on the handle (116; 316) to unlock the lock mechanism (150; 330, 350) to allow the handle (116; 316) to move towards the fully actuated position from the intermediate position; wherein the emergency brake system is in the first stage when the handle (116; 316) is in any position between the non-actuated position and the intermediate position; and wherein the emergency brake system is in the second stage when the handle (116; 316) is in any position between the intermediate position and the fully-actuated position; characterised in that the force on the handle (116; 316) to move the handle (116; 316) increases linearly along a first line from the non-actuated position towards the intermediate position and along a second line from the intermediate position towards the fully-actuated position, wherein the slope of the second line is greater than the slope of the first line, such that an increasingly larger force is needed to move the handle during the second stage as compared with the first stage. a modulating emergency/parking brake valve (78; 120) in fluid communication with and disposed between a pressure source and a wheel brake (14a, 14b), the emergency brake system being operative in a first stage to provide a moderate amount of brake pressure to the wheel brake (14a, 14b) and a second stage to provide a greater brake pressure to the wheel brake (14a, 14b); and a lever assembly (92; 112; 312) operatively connected with the brake valve (78; 120), the lever assembly (92; 112; 312) including a handle (116; 316) being movable between a non-actuated position where the wheel brake (14a, 14b) is disengaged and a fully-actuated position where the wheel brake (14a, 14b) is fully engaged, wherein the brake pressure provided to the wheel brake (14a, 14b) through the brake valve (78; 120) is configured to be provided according to a position of the handle (116; 316); a lock mechanism (150; 330, 350) operatively connected with the handle (116; 316) to obstruct the handle (116; 316) from moving from an intermediate position, which is between the non-actuated position and the fully actuated position, towards the fully actuated position; and an unlock mechanism disposed on the handle (116; 316) to unlock the lock mechanism (150; 330, 350) to allow the handle (116; 316) to move towards the fully actuated position from the intermediate position; wherein the emergency brake system is in the first stage when the handle (116; 316) is in any position between the non-actuated position and the intermediate position; and wherein the emergency brake system is in the second stage when the handle (116; 316) is in any position between the intermediate position and the fully-actuated position; characterised in that the force on the handle (116; 316) to move the handle (116; 316) increases linearly along a first line from the non-actuated position towards the intermediate position and along a second line from the intermediate position towards the fully-actuated position, wherein the slope of the second line is greater than the slope of the first line, such that an increasingly larger force is needed to move the handle during the second stage as compared with the first stage.