Describe the purpose of a run-in test in the overhaul process and the key parameters to monitor.

• A. To test start-up acoustics and cabin noise.
• B. To measure exhaust gas temperature across all cylinders.
• C. To verify stability and performance post-assembly; monitor N1/N2 ramps, turbine inlet temperature, vibrations, fuel flow, and oil pressure.
• D. To verify the electrical bus voltage in the aircraft.

Answer: (C)

Run-in testing after overhaul focuses on confirming the engine behaves as an integrated unit once reassembled, starting from cold conditions and gradually moving into normal operating ranges. The aim is to verify stability and performance after assembly and to catch any issues before the engine returns to service.

The key parameters to monitor are the speeds of the main spools during ramping (N1 and N2) to ensure smooth, commanded acceleration and deceleration without surges or stalls; turbine inlet temperature (TIT or ITT) to keep thermal conditions within safe limits during start, ramp, and steady operation; vibrations to detect imbalances, misalignment, looseness, or bearing issues early; fuel flow to confirm the fuel-control system delivers the correct amount of fuel for the commanded power and remains steady without leaks or spikes; and oil pressure to verify proper lubrication across the ramp and at operating speeds, watching for any abnormal drops or fluctuations. Together, these measurements confirm the engine is performing reliably after overhaul and help catch problems that could affect durability or safety.