Describe the role of rotor balancing in the overhaul process and how completed assemblies are tested.

• A. Increases engine speed.
• B. Cosmetic only.
• C. Not required.
• D. Eliminates vibration by balancing rotors; static/dynamic balancing in a test stand; document balances and adjust as needed.

Answer: (D)

Rotor balancing is used to prevent vibration and premature wear by ensuring the rotating assembly spins with uniform mass distribution. In the overhaul process completed rotor assemblies are balanced to remove any residual imbalance. The process begins with static balancing, where the rotor is mounted so gravity reveals major one-plane imbalances; weight is added or removed to bring the rotor to rest in a stable orientation. Then dynamic balancing is performed on a test stand with sensors while the rotor runs at operating speeds, identifying remaining imbalance in multiple planes and providing data to adjust weights or pad positions accordingly. After balancing, the assembly is tested under run-up and run-down conditions, verifying vibration levels stay within specified limits across the operating speed range. All balance data—weights added/removed, locations, and measured vibration metrics—are documented for traceability and future maintenance. Balancing reduces vibration and bearing loads and improves reliability; the other options are not correct because balancing is not about increasing speed, cosmetic appearance, or optional in service.