January 22, 2025

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Sofema Aviation Services (SAS) www.sassofia.com considers the importance of addressing aircraft engine vibration issues at the earliest opportunity

Introduction 

Aircraft engine vibration is a major concern for maintenance teams due to its potential to cause severe damage.

  • Imbalanced parts can lead to cracked components, metal fatigue, and catastrophic engine failure if not addressed.

Vibration Sources

  • Vibration stems from various moving parts within the engine.
  • Aircraft design, engine location, and mount types can amplify vibration issues.
  • Asymmetrical mass distribution in rotating components causes uneven centrifugal forces.
  • Worn parts (e.g., pumps, bearings)
  • Mass redistribution due to wear or damage (e.g., bird strikes)

Imbalance Causes

  • Component Replacement: Fan blades and other parts.
  • Impact Damage: Bird strikes and other impacts.
  • Natural Wear and Corrosion: Leading to mass redistribution over time.

Testing After Specific Events

  • Impact Events: Any event that could affect the balance of the engine, such as bird strikes, foreign object damage (FOD), or severe turbulence, requires immediate vibration testing.
  • Maintenance Activities: Any major maintenance activity that involves disassembly or replacement of rotating components necessitates subsequent vibration testing to ensure balance is maintained.
  • Trend Analysis: Continuous monitoring and analysis of vibration data can identify emerging issues before they become critical.

>> Any significant change in vibration patterns should trigger an unscheduled test.

Airborne Testing Technologies – Real-Time Monitoring Systems

Preventive maintenance and timely detection of issues can reduce costly repairs and unscheduled downtime.

  • Engine systems typically provide real-time vibration monitoring, allowing for immediate detection of abnormal vibrations.
  • These systems can be integrated with the aircraft’s onboard diagnostic systems for continuous health monitoring.
  • Modern equipment often includes features such as wireless data transmission, automated analysis, and user-friendly interfaces.

Trend Analysis

  • Compare current data with historical records to identify trends and deviations.
  • Use manufacturer-specified vibration limits as thresholds for identifying abnormal conditions

Note – Always conduct surveys under consistent operating conditions to ensure data accuracy and comparability.

Measurement Techniques

  • Establish baseline vibration levels for comparison with future data.
  • Perform multiple measurement runs to account for variability and ensure reliable data.
  • Harmonics and Resonance: Analyze frequency spectra to detect harmonics and resonance that indicate specific types of defects.
  • Employ advanced analysis techniques such as Fast Fourier Transform (FFT) for detailed frequency analysis.

Note – Fast Fourier Transform (FFT) is an essential tool in the field of vibration analysis, offering a comprehensive method to diagnose and isolate vibration issues in aircraft engines. By converting time-domain vibration data into the frequency domain, FFT provides detailed insights into the specific frequencies at which vibrations occur, facilitating precise identification of problematic components.

Best Practices

Proper Balancing: Dynamic and field balancing for component stability.

Principles of Dynamic Balancing

  • Smooth operation of rotating components, reducing wear and tear and Improving the overall performance and efficiency of the engine.
  • Minimizes the risk of component failure due to excessive vibration, extending the life of engine parts.

Dynamic balancing is the process of adjusting the mass distribution of a rotating component to ensure that it rotates smoothly without causing undue vibration.

  • Forces: Imbalance in rotating components generates centrifugal forces that cause vibration. Dynamic balancing aims to counteract these forces by adding or removing mass from specific points on the component.

Procedure for Dynamic Balancing

  • Conduct a thorough inspection of the engine to identify visible defects or damage that could affect balance.
  • Measure initial vibration levels to establish a baseline and identify the magnitude and location of the imbalance.
  • Rotate the component at its operational speed or a suitable test speed.
  • Use sensors to measure vibration and collect data on the magnitude and phase of the imbalance.

 Calculating Corrections

  • Analyze the collected data to determine the amount and location of mass adjustments needed.
  • Follow OEM guidance related to adding or removing mass.
  • Make the necessary mass adjustments based on the analysis.

Verification

  • Conduct a final test to verify that the component is dynamically balanced and meets the required vibration specifications.

Next Steps

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Engine Trend Monitoring Training is available as Classroom, Webinar or Online training. Please see Sofema Aviation Services (SAS), Sofema Online (SOL) or email team@sassofia.com if you have any questions or comments.

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Maintenance, Aircraft engine, considerations, aircraft design, SAS blogs, Verification, Trend Analysis, Maintenance Activities, Engine Vibration, engine location, mass distribution, Impact Events, Measurement Techniques, Dynamic Balancing