I 25.3 Performance requirements

All applicable performance requirements of CS-25 must be met with the ATTCS system functioning normally as designed, except that the propulsive thrust obtained from each operating engine after failure of the critical engine during take-off, and the thrust at which compliance with the one-engine-inoperative climb requirements in CS 25.121(a) and (b) is shown, must be assumed to be not greater than the lesser of –

(a)The actual propulsive thrust resulting from the initial setting of power or thrust controls with the ATTCS system functioning normally as designed, without requiring any action by the crew to increase thrust or power until the aeroplane has achieved a height of 122 m (400 feet) above the take-off surface; or

(b)111 percent of the propulsive thrust which would have been available at the initial setting of power or thrust controls in the event of failure of the ATTCS system to reset thrust or power, without any action by the crew to increase thrust or power until the aeroplane has achieved a height of 122 m (400 feet) above the take-off surface. Note 1. The limitation of performance credit for ATTCS system operation to 111 percent of the thrust provided at the initial setting is intended to:

(i)Assure an adequate level of climb performance with all engines operating at the initial setting of power or thrust controls, and

(ii)Limit the degradation of performance in the event of a critical engine failure combined with failure of the ATTCS system to operate as designed. Note 2. For propeller-driven aeroplanes, propulsive thrust means the total effective propulsive force obtained from an operating engine and its propeller.