System design
(b) System design. Each hydraulic system must: (1) Have means located at a flightcrew station to indicate appropriate system parameters, if (i) It performs a function necessary for continued safe flight and landing; or (ii) In the event of hydraulic system malfunction, corrective action by the crew to ensure continued safe flight and landing is necessary; (2) Have means to ensure that system pressures, including transient pressures and pressures from fluid volumetric changes in elements that are likely to remain closed long enough for such changes to occur, are within the design capabilities of each element, such that they meet the requirements defined in 25.1435(a)(1) through (a)(5); (3) Have means to minimize the release of harmful or hazardous concentrations of hydraulic fluid or vapors into the crew and passenger compartments during flight; (4) Meet the applicable requirements of 25.863, 25.1183, 25.1185, and 25.1189 if a flammable hydraulic fluid is used; and (5) Be designed to use any suitable hydraulic fluid specified by the airplane manufacturer, which must be identified by appropriate markings as required by 25.1541.