Case Description
Investigating a "No Rotation" condition during engine start sequence. Verified pilot indications (Start Lights) and Bleed Air Regulator status to isolate the fault to the Starter Control Valve.
Required Tools
Multimeter (to check SCV solenoid voltage), Pressure Gauge, Standard line maintenance hand tools
Safety Protocol
Ensure all bleed air sources (GTC/APU) are OFF and system is depressurized before loosening SCV clamps. Remain clear of the propeller arc at all times during testing.
Lessons Learned
Always verify the "Start Valve Open" light first. If the light is OFF but air is available, the fault is likely the Control Valve, not the Starter itself. Diagnosing from the cockpit indications saves hours of troubleshooting time , Problem: Engine failed to rotate when the start switch was engaged.rnrnTroubleshooting process:rnrnPilot Feedback: Asked the pilot "Did the Start Valve Open light come on?". Pilot confirmed: NO.rnSystem Check: Checked the air source. The Regulator Bleed Valve was OPEN and supplying sufficient duct pressure.rnIsolation: Since bleed air was reaching the engine nacelle but the start light did not illuminate (and no rotation occurred), the issue was isolated to the Starter Control Valve (SCV) or the starter itself.rnDiagnosis: Confirmed power signals reached the valve, but air was not passing through.rnConclusion: The Starter Control Valve was mechanically failed in the closed position, preventing air from driving the pneumatic starter. Replaced SCV to fix the issue.
Case Overview
Estimated Time
4
Views
17
Author
Fayez Almutairi