Gulfstream GIV: Troubleshooting High Engine RPMs

During recent outgoing engine runs on a Gulfstream GIV, Duncan Aviation technicians noticed the Left Engine HP Idle RPM on the Rolls-Royce Tay 611-8 was 66% (Approach Idle), and the Right Engine was 48-49% (GND Idle).  The LP RPM and Fuel Flow agreed with the higher HP RPM of the left engine.

This led the technicians to suspect the Approach Idle Solenoid Valve was stuck open, accounting for the additional 18% of HP RPM. The valve is powered closed when the aircraft is on the ground.

After verifying 28v and a GND were present at the Solenoid Valve, the valve was replaced, and an Operational Check was performed. All engine indications were now reading correctly at GND Idle.

Duncan Aviation has three full-service facilities located in Battle Creek, Michigan; Lincoln, Nebraska; and Provo, Utah, providing all major hourly and calendar inspections, including the 5000-cycle, on GIV, G300, G400, G350, G450, GV, and G550. They perform special and unscheduled inspections, airworthiness limitation inspections, and prebuy evaluations on large-cabin models.

Duncan Aviation is approved for Rolls Royce CorporateCare® and new engine warranty work on aircraft. We are authorized and have inventory and tooling to support the Rolls Royce Spey/Tay, BR710, and AE3007A engine models to perform engine removals and installations, line-level inspections, maintenance and repair, and service bulletins.