Reliability-Based Preventive Maintenance Planning of Pressure Regulator Shut-Off Valve Components on CN235 Aircraft

Abstract

Aircraft component reliability is essential for maintaining flight safety and operational continuity. The Pressure Regulator Shut-Off Valve (PRSOV) is a critical component of the CN235 bleed air system because it regulates and shuts off pressurized air supplied to the aircraft environmental control system. Historical maintenance records indicated 17 PRSOV-related failures during 0–8,952 flight hours, including failures involving the valve, connector, diaphragm, seal O-ring, spring, and solenoid. This study aims to characterize PRSOV reliability, identify dominant failure modes and their causes, and develop reliability-based preventive maintenance recommendations. A quantitative reliability analysis was conducted using a two-parameter Weibull distribution, supported by Failure Mode and Effects Analysis (FMEA) and Fault Tree Analysis (FTA). Weibull analysis indicated a shape parameter greater than one, representing an increasing failure-rate pattern and suggesting the influence of component aging and wear-out mechanisms. FMEA was used to prioritize failure modes based on severity, occurrence, and detection, while FTA was applied to identify the logical relationships among basic failure causes. The integrated results indicate that preventive maintenance intervals should be differentiated according to component-specific reliability characteristics and failure risks rather than relying solely on the manufacturer's general maintenance interval. The proposed approach provides a basis for improving PRSOV reliability, reducing unscheduled maintenance, and supporting CN235 operational safety.